Esters and their biosynthesis in fermented dairy products: a review

Sensory characteristics and key odor-active compounds of oxidized Antarctic krill oil: A comparative study with oxidized fish oil

Oxidized Antarctic krill oil (AKO) has unique sensory characteristics that have not been fully elucidated. This study was aimed to explore the sensory characteristics and key odor-active compounds of oxidized AKO by comparing with oxidized fish oil (FO) through accelerating storage experiments. The sensory evaluation results exhibited that oxidized AKO had a distinct ammonia odor and oxidized FO had an obvious fishy odor. GC-MS and GC-O analysis identified 21 and 28 odor-active compounds in AKO and FO samples, respectively, and the correlation analysis showed a good correlation between sensory attributes and odor-active compounds. Trimethylamine (27.73 mg/kg) was the key odor-active compound with an ammonia odor in AKO, and not found in FO. Although AKO samples also contains odor-active compounds such as 1-penten-3-ol (4.93 mg/kg) and 1-penten-3-one (1.12 mg/kg) contributing to fishy odor in FO samples, the masking effect between the odor compounds prevented obvious fishy odor from being sensed.

The availability of ethanol: A decisive factor in the biosynthesis of ethyl esters in enzyme-modified cheese flavor

Lactic acid bacteria (LABs) exhibit a strong acid-producing capability in the manufacturing of enzyme-modified cheese flavor (EMCF), but their limited ester synthesis ability resulted in EMCF having strong sour aroma with imbalance flavor. Strains with higher esterase activity were screened by simulated fermentation. Lacticaseibacillus casei exhibited greater activity in synthesizing ethyl hexanoate and ethyl octanoate, while Lactobacillus helveticus had a higher yield of ethyl acetate. The analysis of volatile compounds revealed that ethyl esters were not detected under the conditions of both fatty acids and esterases, indicating that ethanol served as a key substrate limiting the synthesis of esters. The addition of ethanol significantly increased both the variety and concentration of volatile compounds, especially acids, alcohols, and ethyl esters. Sensory analysis indicated that ethanol contributed to the development of fruity and wine aromas. EMCF exhibitd a softer flavor at 0.5 % ethanol addition, which providing practical insights for balancing EMCF flavor.

Understanding the flavor dynamics of high-fat dairy products: Insights into mechanisms, aroma profiles, and sensory evaluation

Cream, butter, and anhydrous milk fat are the most widespread high-fat dairy products produced and consumed globally, appreciated for their nutritional value and appealing flavor. For manufacturers, understanding the flavor of these products by closely examining their sensory attributes and chemical properties is crucial to maintaining high-quality flavors and ensuring consumer acceptance. This review provides a comprehensive and up-to-date analysis of the flavor aspects of these high-fat dairy products, focusing on the mechanisms of aroma-active compound formation, odor assessment methods (including extraction, qualitative analysis, identification, and chemometric approaches), and descriptive sensory evaluation techniques. Over 100 aroma-active substances have been identified in high-fat dairy products, with aldehydes, lactones, and ketones as significant contributors. These aroma-active substances formation occurs primarily through lipolysis, proteolysis, and fermentation. Advanced analytical techniques show promise for comprehensive flavor profiling; however, challenges remain in correlating instrumental data with sensory perceptions. Future research should focus on identifying trace off-flavors, improving extraction methods, and developing rapid, non-destructive quality control techniques to enhance sensitivity, real-time monitoring, portability, time efficiency, and visualization for a complete flavor profile. Additionally, these efforts will provide deeper insight into the factors contributing to flavor variations during processing, improve quality control, and enhance the marketability of innovative dairy products.

Matching the Sensory Analysis of Serpa PDO Cheese with the Volatile Profiles-A Preliminary Study

Serpa cheese, a Portuguese Protected of Denomination Origin (PDO) cheese, known for its unique sensory attributes, is made from the raw milk of native sheep. In this preliminary work, ten samples of Serpa cheese were submitted for a sensory evaluation performed by an expert panel in a sensory laboratory accredited according to ISO 17025 for Serpa cheese parameters, and the panelists classified the cheeses based on texture, taste and odor scores, in accordance with the specifications for the classification of this type of cheese. All cheeses were analyzed by SPME-GC-MS. Following an exploratory unsupervised multivariate analysis, the supervised multivariate analysis by partial least squares-discriminant analysis (PLS-DA), associated the relative percent area of the identified volatiles with the classification of cheeses attributed by the sensory panel. Among the 144 compounds putatively identified, there was a pattern of compound distribution of some of them, such as acetoin, diacetyl, and 2,3-butanediol, leaning toward the cheese samples with high taste and odor scores, while other compounds, such as ethyl caprate, capric acid, and 3-methylindole, were more associated with the cheese samples rated with a low score. Despite the reduced number of samples that may have imposed some restrictions on the conclusions drawn, there was a clear trend in the volatiles' distribution, allowing us to identify, based on the higher correlation loadings, potential candidates for the Serpa cheese sensory quality. This preliminary study presents, for the first time, an overview of the volatiles that are present in Serpa PDO cheese that may be responsible for the positive or negative sensory evaluation of this PDO cheese.

Lactic acid fermentation of a novel Sea buckthorn-monk fruit beverage: Phenolic profile, volatile compounds, and antidiabetic and antihypertensive potential

Functional foods offer health benefits that extend beyond basic nutrition, addressing critical public health challenges such as diabetes and hypertension. This study developed a novel lactic acid bacteria (LAB)-fermented beverage integrating sea buckthorn and monk fruit, two bioactive-rich ingredients with complementary properties. Sea buckthorn provides a robust profile of antioxidants, while monk fruit's natural sweetness and low glycemic index make it an ideal ingredient for health-conscious consumers. Three LAB strains (Lactiplantibacillus plantarum (LP), Lacticaseibacillus paracasei (LPC), and Lactobacillus acidophilus (LA) were utilized individually and in combination to evaluate their impact on the beverage's bioactive and functional properties. Phenolic profiling (HPLC) revealed 13 phenolic compounds, with LPC fermentation achieving the highest total polyphenol content (232.50 ± 2.37a). Quinic acid and neochlorogenic acids were most abundant in all samples, with significantly elevated concentrations observed in fermented samples. Remarkably, LAB fermentation induced the formation of kaempferol, a phenolic compound with well-documented therapeutic properties, which was absent in the control. Volatile compound analysis (HS-SPME-GC-MS) and aroma profiling (E-nose) demonstrated that LP and LPC + LA fermentations enhanced key volatile compounds and improved sensory complexity, as corroborated by aroma profiling. The functional properties of the beverage were assessed through α-amylase, α-glucosidase, and angiotensin-converting enzyme (ACE) inhibitory assays. LP and LP + LPC demonstrated superior antidiabetic and antihypertensive potential. A Mantel test confirmed strong correlations between phenolic profiles and bioactivities, substantiating the role of LAB fermentation in enhancing therapeutic potential.

Analytical Mapping of Swiss Hard Cheese to Highlight the Distribution of Volatile Compounds, Aroma, and Microbiota

Cheese is one of the most consumed fermented animal-based products globally, rendering its quality assessment and evaluation of substantial economic interest. Understanding the degree of cheese homogeneity is paramount for designing effective sampling strategies, yet this information is largely lacking. This study investigates the homogeneity of a cheese wheel based on the distribution of volatile compounds, microbiota, sodium chloride content, and pH, combined with sensory analyses. The outer zones of the cheese wheel were primarily characterized by the presence of sulfur compounds, esters, pyrazines, ketones, Streptococcus thermophilus, high sodium chloride concentration and high pH. In contrast, the inner zones of the cheese wheel were dominated by lactones, carboxylic acids, aldehydes, Lactobacillus delbrueckii subsp. lactis and Lacticaseibacillus paracasei. The presence of alcohols and Lactobacillus helveticus was observed throughout the cheese wheel. Furthermore, sensory descriptions were found to match predominantly with the aroma of the volatile compounds identified. The cheese wheel was found to be heterogeneous in all investigated characteristics. Our results indicate that the level of cheese homogeneity should be considered when designing sampling strategies, as these significantly impact the accuracy and reproducibility of analytical outcomes.

The production of esters by specific sourdough lactic acid bacteria species is limited by the precursor concentrations

The production of fruity esters by sourdough lactic acid bacteria (LAB) and yeasts has not been explored in detail. Moreover, the biosynthesis of esters by LAB species under conditions similar to those occurring during sourdough production is still questionable. Concerning yeasts, a genome mining of 75 genomes revealed a strain dependency of the presence of seven specific ester biosynthesis genes. Accordingly, PCR assays to detect these acetate (ATF1 and ATF2) and ethyl ester (EHT1 and EEB1) biosynthesis genes were developed and used to screen 91 strains of yeast species. Concerning LAB, a genome mining of 401 genomes revealed a species dependency of the presence of three esterase-encoding genes (estA, estB, and estC). A phenotypic analysis carried out with a selection of 10 strains of the LAB species Companilactobacillus crustorum, Companilactobacillus nantensis, Companilactobacillus paralimentarius, Fructilactobacillus sanfranciscensis, Lactiplantibacillus xiangfangensis, Levilactobacillus zymae, and Limosilactobacillus fermentum in a wheat sourdough simulation medium (WSSM) supplemented with ester precursor molecules ([higher] alcohols and fatty acids) revealed that their ester biosynthesis capacity was limited by the precursor concentrations. Ethyl acetate and ethyl lactate were produced by all strains, except for those of Frul. sanfranciscensis. These results suggested that one of the esterase-encoding genes considered could be implicated in the ethyl acetate and/or ethyl lactate biosynthesis. Overall, the ester biosynthesis capacity by LAB is of great interest in view of fruity flavor formation during sourdough and sourdough bread productions.

IMPORTANCE

The present study gave insights into the production of esters, which impart fruity flavors to fermented foods, by not only sourdough yeasts but also lactic acid bacteria. It showed that some lactic acid bacteria species can synthesize the esters ethyl acetate (sweet notes) and ethyl lactate (creamy notes) under specific conditions. The information gathered during the present study will enable sourdough bakers and companies from the bakery sector to get more information on how to produce sourdoughs that can add fruity notes to the final products after a rational screening and selection of potential starter culture strains.

Fermenting shea nuts using the traditional pit method yields better physicochemical properties with potential environmental benefits

Shea oil, a globally consumed commodity, is intricately linked to the labor of women in Sub-Saharan Africa. This study examines local perceptions and adoption of a traditional shea nut fermentation method using subterranean pits in rural West African communities, and the chemical profiles of the kernels processed through different traditional methods. Key findings are that 1) local processors prefer the pit method due to its convenience and efficiency, and 2) lipid analyses indicate that fermenting shea nuts for three to six months results in an optimal chemical profile, characterized by lower free fatty acid (more than threefold) and polar lipid (more than 15-fold) content compared to boiled kernels. This enhances quality and mechanical processability, both criteria desirable for industrial applications. This study fills an important gap by chemically characterizing a traditional shea processing practice that has received little scientific attention. The results imply that the pit method holds potential for industrial shea oil extraction and for reducing firewood and water use in producing communities. However, this potential depends on fair benefit-sharing, local communities' willingness to adopt the new practice, and overcoming the challenges for scaling up.

Effects of Sodium Acetate and Sodium Butyrate on the Volatile Compounds in Mare's Milk Based on GC-IMS Analysis

This study aims to explore the impact of adding sodium acetate and sodium butyrate on the composition, blood biochemical parameters, and volatile flavor compounds of lactating mares' milk. By assessing the influence of these additives on milk flavor enhancement, the findings provide scientific evidence for optimizing flavor characteristics and offer new strategies for improving the sensory attributes of mare milk products. Eighteen lactating Yili mares were randomly assigned to three groups: a control group, a sodium acetate group (85 mg/kg·BM-1), and a sodium butyrate group (85 mg/kg·BM-1). The experiment lasted 90 days, with milk yield recorded on days 0, 30, 60, and 90. Milk samples were collected on day 60 (peak lactation) for compositional analysis, and GC-IMS was employed to identify and quantify volatile compounds. Additionally, blood samples were drawn from the jugular vein before morning feeding on day 60 using heparinized tubes to assess key biochemical markers, including glucose, triglycerides, total cholesterol, and urea. The results revealed the following findings: (1) Milk yield and composition: The addition of sodium acetate and sodium butyrate had no significant effect on milk yield. However, both treatment groups exhibited significantly or extremely significantly higher milk fat content compared to the control group, whereas milk protein and lactose levels remained largely unchanged. (2) Blood biochemical indicators: The sodium butyrate group showed an extremely significant increase in urea levels compared to the sodium acetate and control groups. Glucose levels in the sodium acetate group were also significantly higher than in the control group. Moreover, triglyceride levels were markedly elevated in the sodium butyrate group compared to the sodium acetate group, while total bilirubin concentrations were significantly higher in the sodium acetate group than in the control group. (3) Volatile compounds: The addition of these additives led to a significant increase in the diversity and concentration of volatile compounds in mare milk. Notably, esters, aldehydes, and ketones showed substantial enrichment in both treatment groups. The relative abundance of esters such as butyl acetate, L-lactic acid ethyl ester, 1-pentene-3-ol, pentanol, and 3-pentanone increased, alongside a significant rise in aldehydes and ketones, including 2-heptenal and 3-pentanone. In conclusion, sodium acetate and sodium butyrate enhance milk flavor by modulating milk composition and metabolic parameters, providing a scientific foundation for improving the quality of mare milk products.

Insight into the mechanism of gel properties, microstructure and flavor of surimi gels improved by wheat bran with different particle sizes

This study investigated the effect of wheat bran (WB) with different particle sizes (W1, 155.00 ± 2.08 μm; W2, 78.33 ± 0.52 μm; W3, 46.90 ± 0.60 μm; W4, 23.53 ± 0.49 μm; and W5, 12.97 ± 0.19 μm) on the gel strength, texture, microstructure, dynamic rheological, secondary structures and flavor of surimi gels. Results demonstrated that the gel strength and water-holding capacity (WHC) of the surimi gels gradually increased with the decrease in WB particle size. The added W5 (12.97 ± 0.19 μm) increased the bound water content in the surimi gels by 12.60 % whereas the free water decreased by 6.59 % (p < 0.05), indicating that the addition of superfine WB contributed to the conversion of free water into bound water in the surimi gels matrices. Microstructural observations indicated that WB with different particle sizes promoted the formation of a continuous gel matrix and a denser surimi gel network structure. The β-sheet dominated in the secondary structure of surimi gels. Electronic tongue results showed that the addition of WB reduced the bitterness of surimi gels. Gas chromatography-ion mobility spectrometry (GC-IMS) results revealed that more esters were present in the samples when W1, W2, and W3 were added. Overall, W5 had the best enhancement effect on the quality of surimi gels, and this study lays the reference value for WB as an agricultural by-product to improve the quality of surimi products.

Odor-active aroma compounds in traditional fermented dairy products: The case of mabisi in supporting food and nutrition security in Zambia

Aroma is a key sensory attribute that determines consumer preference and acceptability of foods. The aroma of fermented dairy products comprises the volatile organic compounds (VOCs) produced by the activity of fermenting microbes and the compounds originally present in unfermented raw milk. A unique combination of specific compounds detectable by human olfactory senses creates the distinct odor profile of fermented products. This study investigated the influence of different production methods on the VOCs responsible for the odor-active compounds, and the microbial communities present in mabisi, a traditional Zambian fermented dairy product. The VOCs and microbial community composition of four mabisi variants were investigated using GC-O-MS and PTR-QiTOF-MS techniques, and 16S rRNA amplicon sequencing, respectively. A panel of three assessors identified the odor-active compounds from the GC-O-MS, and the compound's quantitative aspects were obtained by the PTR-QiTOF-MS. Twelve volatile compounds were identified as odor-active compounds during the GC-O-MS analysis. The most prominent were ketones and esters, which imparted a buttery and fruity aroma, respectively. The PTR-QiTOF-MS run identified and quantified a total of 390 m/z peaks, 55 of which were tentatively identified. 16S rRNA amplicon sequencing revealed a diverse microbial community, with Lactococcus species dominating. While the VOC profiles showed significant variation in functionality among the variants, minor differences were observed in microbial composition. The study confirms that high compound concentration does not necessarily correlate with compound odor activity. Our findings offer insights into the significance of aromas and microbial ecology to support optimization strategies for upscaling traditional fermented products.

Metagenomic Reveals the Role of Autochthonous Debaryomyces hansenii in the Fermentation and Flavor Formation of Dry Sausage

The effect of Debaryomyces hansenii SH4, a typical aroma enhancer, on flavor formation of the dry fermented sausage was investigated using gas chromatography-mass spectrometry and metagenomic sequencing. The results showed that inoculation with D. hansenii SH4 promoted volatile compound formation from carbohydrate and amino acid metabolism and accelerated ester synthesis. The enzymes, genes, and microorganisms involved in the formation pathway of volatile compounds based on microbial metabolism were predicted and constructed into a metabolic pathway network. D. hansenii, Lactobacillus curvatus, Lactobacillus sakei, Lactobacillus plantarum, Leuconostoc fallax, Weissella minor, and Staphylococcus and Candida species were found to be the predominant functional microbes for flavor development in dry sausage. This study established a new insight into the metagenome-based bioinformatic effects of D. hansenii SH4 as a starter culture on the microbial synthesis of key volatile compounds in dry sausage.

Volatile Profile of Bee Pollens: Optimization of Sampling Conditions for Aroma Analysis, Identification of Potential Floral Markers, and Establishment of the Flavor Wheel

The volatile profile of bee pollen samples from Central and Eastern Europe was investigated by headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Sampling conditions were optimized for the extraction of volatiles. Pollen odorants were extracted with six different fiber coatings, five various extraction times, three diverse extraction temperatures and three differing desorption times. The most effective combination was the application of divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber coating used at 60°C for 30 min for extraction and 1 min for desorption. The optimized method was applied to investigate the volatile profile of 14 pollen samples (three rapeseed, musk thistle, rock-rose, traveler's joy, dropwort, honey locust, sunflower, red poppy, phacelia, sweet cherry, wild blackberry, and dandelion). The volatile profiles of bee pollens were different and were crucially depended on botanical origin. The aroma activity of the samples was generated by 31.0%-48.3% of total volatiles. The number of the identified odorants were between 75 and 101 in the pollen samples by GC-MS, of which 26-42 were aroma-active. The volatile organic compounds (VOCs) were classified into 13 different chemical classes. In most pollen, fatty acids were the predominant volatiles (14.87%-50.58%), while in some samples esters were the most abundant odorants (4.09%-45.46%). Panelists confirmed the presence of six main sensory characteristics described as "green/sour", "fruity", "spicy/herbal", "earthy/mushroom", "sweet/baked/caramel/honey", and "floral" compounds. These results establish the flavor wheel suitable for the comprehensive sensory description of pollen pellets from individual plant species. All samples contained characteristic odorants that may help in their botanical identification.

Characterization of volatile compound profile in Mongolian traditional fermented mare's milk, as Airag

We aimed to evaluate the volatile compounds profile in traditional airag samples collected from two regions, including Bulgan and Uvurkhangai provinces, whereas famous airag-making areas in Mongolia. The volatile compounds of airag were investigated by the GC-MS method. A total of 95 kinds of volatile compounds were detected, and these were classified into 6 different classes: 14 acids, 14 alcohols, 16 aldehydes, 19 esters, 9 ketones, and 23 aliphatic hydrocarbons. Among them, acetic acid, 2-methyl propionic acid, isoamyl lactic acid, 2-methyl butanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, n-decanoic acid, 1-propanol, 3-methyl 1-butanol, phenyl ethyl alcohol, acetaldehyde, acetoin, ethyl acetate, ethyl hexanoate, ethyl caprylate, ethyl decanoate, ethyl 9-decanoate, and ethyl laurate had a high concentration in airag samples. It may explain that acids, alcohols, and esters mainly influence the taste and aroma of airag, and aldehydes change depending on their fermentation time. We also found that Bulgan provinces` samples contained 20 types of aliphatic hydrocarbons, which may relate to the vegetation and fermentation process. The formation of sensory characteristics in airag is a complex and unclear process because it affects many factors. Our findings provide essential guidance on the composition of volatile compounds in Mongol airag.

The Effect of Salt Reduction on the Microbial Community Structure and Metabolite Composition of Cheddar Cheese

As consumer demand for low-salt diets increases, the development of low-salt cheese has emerged as a prevailing trend. To gain a deeper insight into the effects of salt reduction on cheddar cheese, this study used cheddar cheese with a 2.0% salt concentration (full salt, FS) as the standard control, exploring the differences in quality and composition between cheddar cheese with a 1.5% salt concentration (reduced salt, RS) and a 1.0% salt concentration (half salt, HS). The results revealed that, while the RS group exhibited significant differences in texture compared to the FS group, their physicochemical composition and microbial communities were similar, resulting in a product with quality comparable to traditional cheese. In contrast, the HS group differed notably from the FS group in terms of its physicochemical composition, texture, and microbial communities. Shifts in the microbial community within the HS group promoted enhanced protein metabolism, producing a substantial increase in free amino acids and volatile flavor compounds. In summary, cheddar cheese with a 1.5% salt concentration is similar to traditional varieties in terms of quality, while the 1.0% salt variety displays a more complex composition, due to microbial community shifts facilitating protein metabolism.

Multi-omics combined approach to analyze the mechanism of flavor evolution in sturgeon caviar (Acipenser gueldenstaedtii) during refrigeration storage

Multi-omics techniques were combined with microstructure, molecular sensory science and non-volatile matrices for the first time to investigate variations in organic macromolecules and flavor in caviar during preservation. After 4-6 weeks of storage, the peroxide value was 35.38 mg/g and the accumulation of thiobarbiturates was significant with caviar membranes exhibiting a decrease in elasticity and an increase in viscosity. Sixteen key volatile compounds were detected by GC-MS, while the volatile compounds that contributed to the differences in caviar flavor at different storage times were mainly tetradecane, (E)-2-hexenal, and heptanal. The pathways associated with flavor release during storage were mainly abundant in the linolenic acid metabolism, alanine metabolism, and glycerophospholipid metabolism pathways. The correlation of 11 differential proteins and 24 differential lipids with odorants was further explored, such as arginine, proline, alanine, PE (20:4/22:6), PE (16:1/18:2), and PE (20:5/18:2). Overall, Aspartate, glutamate, oleic acid, linoleic acid, and phospholipids enriched in C22:6 and C18:2 chains are potential metabolic markers. This study provides a basis from a multi-omics perspective for the investigation of the relationship between quality deterioration and precursor metabolism in caviar storage process.

Determination of free fatty acids and volatile compounds of butter oil produced from pasteurized and unpasteurized butter at different temperatures

In this study, the effects of different raw materials, different processing temperatures, and storage temperatures on some properties of butter oil were investigated. Two different kinds of butter were produced from cream containing 40% milk fat. Both butter samples were processed into butter oil at three different temperatures (60, 90, and 120°C). Butter and butter oil samples were stored at +4°C and analyses were performed at 0, 30, and 60 days of storage. There are no significant differences between the atherogenicity index and the saturated and unsaturated fatty acid composition of butter and butter oil samples. Free fatty acid values of all samples increased during storage. Also, in all three storage periods, it was determined that free fatty acids were higher in butter samples than in butter oil samples. During storage, saturated and unsaturated free fatty acid values are generally higher in butter oil processed at 60°C than in butter oil processed at 90°C and 120°C. In total, 40 volatile compounds were detected, which included 8 ketones, each of 6 aldehydes, alcohols, acids, and hydrocarbons, 5 terpenes, and 3 esters in butter and butter oil samples. Aldehydes and ketones were generally highest in butter oil processed at 120°C.

Enhancement of β-galactosidase catalytic activity and stability through covalent immobilization onto alginate/tea waste beads and evaluating its impact on the quality of some dairy products

The current study aimed to evaluate the hydrolysis of whole fat milk (WFM) and sweet whey (SW) using β-galactosidase (β-gal) after covalent immobilization onto activated alginate/tea waste (Alg/TW) beads as a novel carrier. The optimum temperature for free and Alg/TW/β-gal was 40 °C and the ideal pH was 7.0. However, Alg/TW/β-gal displayed better stabilities at high temperatures and a wide pH range. Additionally, the value of Km and Vmax for Alg/TW/β-gal was higher than the free enzyme. The Alg/TW/β-gal showed better residual activity (78.6 %) after 90 storage days at 4 °C. The reusability of Alg/TW/β-gal was very good as it conserved its full activity after 15 consecutive cycles and conserved 93 % of its initial activity after 10 cycles with ONPG (O-nitrophenyl-β-D-galactopyranoside) and lactose as a substrate, respectively. The impact of Alg/TW/β-gal on WFM and SW using HPLC analysis revealed a remarkable decrease in lactose concentration and increase of glucose and galactose concentrations. The SW exhibited higher degree of lactose hydrolysis (97.3 %) compared to WFM (62.4 %). Besides, SW had a prominent increase in total phenolic content (96.8 mg/L) compared to WFM (54.3 mg/L). The antioxidant activity had increased after enzyme treatment in both WFM and SW. The GC-MS analysis for volatile compounds identified twenty-five flavour constituents. Finally, Alg/TW/β-gal has a potential application for obtaining healthy, acceptable, and commercial dairy products of low lactose.

Transcriptomics to evaluate the influence mechanisms of ethanol on the ester production of Wickerhamomyces anomalus with the induction of lactic acid

Wickerhamomyces anomalus is one of the most important ester-producing strains in Chinese baijiu brewing. Ethanol and lactic acid are the main metabolites produced during baijiu brewing, but their synergistic influence on the growth and ester production of W. anomalus is unclear. Therefore, in this paper, based on the contents of ethanol and lactic acid during Te-flavor baijiu brewing, the effects of different ethanol concentrations (3, 6, and 9% (v/v)) combined with 1% lactic acid on the growth and ester production of W. anomalus NCUF307.1 were studied and their influence mechanisms were analyzed by transcriptomics. The results showed that the growth of W. anomalus NCUF307.1 under the induction of lactic acid was inhibited by ethanol. Although self-repair mechanism of W. anomalus NCUF307.1 induced by lactic acid was initiated at all concentrations of ethanol, resulting in significant up-regulation of genes related to the Genetic Information Processing pathway, such as cell cycle-yeast, meiosis-yeast, DNA replication and other pathways. However, the accumulation of reactive oxygen species and the inhibition of pathways associated with carbohydrate and amino acid metabolism may be the main reason for the inhibition of growth in W. anomalus NCUF307.1. In addition, 3% and 6% ethanol combined with 1% lactic acid could promote the ester production of W. anomalus NCUF307.1, which may be related to the up-regulation of EAT1, ADH5 and TGL5 genes, while the inhibition in 9% ethanol may be related to down-regulation of ATF2, EAT1, ADH2, ADH5, and TGL3 genes.

The difference analysis of physicochemical indexes and volatile flavor compounds of chili oil prepared from different varieties of chili pepper

Because of its peculiar flavor, chili oil is widely used in all kinds of food and is welcomed by people. Chili pepper is an important raw material affecting its quality, and commercial chili oil needs to meet various production needs, so it needs to be made with different chili peppers. However, the current compounding method mainly relies on the experience of professionals and lacks the basis of objective numerical analysis. In this study, the chroma and capsaicinoids of different chili oils were analyzed, and then the volatile components were determined by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion migration spectrometer (GC-IMS) and electronic nose (E-nose). The results showed that Zidantou chili oil had the highest L*, b*, and color intensity (ΔE) (52.76 ± 0.52, 88.72 ± 0.89, and 118.84 ± 1.14), but the color was tended to be greenyellow. Xinyidai chili oil had the highest a* (65.04 ± 0.2). But its b* and L* were relatively low (76.17 ± 0.29 and 45.41 ± 0.16), and the oil was dark red. For capsaicinoids, Xiaomila chili oil had the highest content of capsaicinoids was 2.68 ± 0.07 g/kg, Tianjiao chili oil had the lowest content of capsaicinoids was 0.0044 ± 0.0044 g/kg. Besides, 96 and 54 volatile flavor substances were identified by GC-MS and GC-IMS respectively. And the main volatile flavor substances of chili oil were aldehydes, alcohols, ketones, and esters. A total of 11 key flavor compounds were screened by the relative odor activity value (ROAV). Moguijiao chili oil and Zidantou chili oil had a prominent grass aroma because of hexanal, while Shizhuhong chili oil, Denglongjiao chili oil, Erjingtiao chili oil, and Zhoujiao chili oil had a prominent floral aroma because of 2, 3-butanediol. Chili oils could be well divided into 3 groups by the partial least squares discriminant analysis (PLS-DA). According to the above results, the 10 kinds of chili oil had their own characteristics in color, capsaicinoids and flavor. Based on quantitative physicochemical indicators and flavor substances, the theoretical basis for the compounding of chili oil could be provided to meet the production demand more scientifically and accurately.

Application of Ligilactobacillus salivarius SP36, a Strain Isolated from an Old Cheese Seal, as an Adjunct Culture in Cheesemaking

Adjunct cultures originating from artisanal cheese environments may play an important role in recreating and developing traditional cheese flavours, thanks to their enzymatic activities, involved in different metabolic pathways that occur during cheese ripening. In this work, Ligilactobacillus salivarius SP36, a strain isolated from an old cheese seal, was added as an adjunct culture to the cheese's raw milk, and its effect on the microbiological, physical-chemical and sensory characteristics of the cheese was studied. The use of L. salivarius SP36 in cheese manufacturing had no significant (p > 0.05) effect on the cheese microbiota, gross composition (fat percentage, protein, total solids, moisture and NaCl concentration), colour or texture of the cheese. However, L. salivarius SP36 increased (p < 0.01) the formation of 25 volatile compounds, including 10 esters, 1 aldehyde, 8 alcohols and 6 carboxylic acids. In addition, cheeses made with L. salivarius SP36 received higher scores (p < 0.01) for aroma intensity and quality than control cheeses. L. salivarius SP36 proved to be a good candidate as an adjunct culture for cheesemaking, since it improved the cheese flavour by making it more intense and recovering typical sensorial notes of traditional cheeses.

Exploiting Chloroform-COware Chemistry for Pd-Catalyzed Carbonylation of Naturally Occurring and Medicinally Relevant Phenols

In this study, a ligand-free palladium-catalyzed carbonylation of phenols is conducted under ambient conditions, utilizing the "Chloroform-COware" chemistry. The developed methodology enables the conversion of diverse medicinally relevant phenols, encompassing both natural and synthetic derivatives, into their respective aryl ester counterparts. This transformation is achieved through the reaction with a broad spectrum of aryl and heteroaryl iodides. The protocol is characterized by its simplicity, generality, and wide substrate scope, delivering bioactive aryl ester derivatives in good to excellent yields. A direct comparison with the one-pot approach, resulting in poor yields of aryl esters, highlights the superior efficiency of the two-chamber setup (COware). Moreover, we successfully applied this two-chamber technique for gram-scale synthesis and postmodification of the synthesized ester to a pharmaceutically important benzocoumarin core.

Addressing flavor challenges in reduced-fat dairy products: A review from the perspective of flavor compounds and their improvement strategies

In recent years, the demand for reduced-fat dairy products (RFDPs) has increased rapidly as the health risks associated with high-fat diets have become increasingly apparent. Unfortunately, lowering the fat content in dairy products would reduce the flavor perception of fat. Fat-derived flavor compounds are the main contributor to appealing flavor among dairy products. However, the contribution of fat-derived flavor compounds remains underappreciated among the flavor improvement factors of RFDPs. Therefore, this review aims to summarize the flavor perception mechanism of fat and the profile of fat-derived flavor compounds in dairy products. Furthermore, the characteristics and influencing factors of flavor compound release are discussed. Based on the role of these flavor compounds, this review analyzed the current and potential flavor improvement strategies for RFDPs, including physical processing, lipolysis, microbial applications, and fat replacement. Overall, promoting the synthesis of milk fat characteristic flavor compounds in RFDPs and aligning the release properties of flavor compounds from the RFDPs with those of equivalent full-fat dairy products are two core strategies to improve the flavor of reduced-fat dairy products. In the future, better modulation of the behavior of flavor compounds by various methods is promising to replicate the flavor properties of fat in RFDPs and meet consumer sensory demands.

Formation of Key Aroma Compounds During 30 Weeks of Ripening in Gouda-Type Cheese Produced from Pasteurized and Raw Milk

Gouda-type cheeses were produced on a pilot-scale from raw milk (RM-G) and pasteurized milk (PM-G). Sixteen key aroma compounds previously characterized by the sensomics approach were quantitated in the unripened cheeses and at five different ripening stages (4, 7, 11, 19, and 30 weeks) by means of stable isotope dilution assays. Different trends were observed in the formation of the key aroma compounds. Short-chain free fatty acids and ethyl butanoate as well as ethyl hexanoate continuously increased during ripening but to a greater extent in RM-G. Branched-chain fatty acids such as 3-methylbutanoic acid were also continuously formed and reached a 60-fold concentration after 30 weeks, in particular in PM-G. 3-Methylbutanal and butane-2,3-dione reached a maximum concentration after 7 weeks and decreased with longer ripening. Lactones were high in the unripened cheeses and increased only slightly during ripening. Recent results have shown that free amino acids were released during ripening. The aroma compounds 3-methylbutanal, 3-methyl-1-butanol, and 3-methylbutanoic acid are suggested to be formed by microbial enzymes degrading the amino acid l-leucine following the Ehrlich pathway. To gain insight into the quantitative formation of each of the three aroma compounds, the conversion of the labeled precursors (13C6)-l-leucine and (2H3)-2-keto-4-methylpentanoic acid into the isotopically labeled aroma compounds was studied. By applying the CAMOLA approach (defined mixture of labeled and unlabeled precursor), l-leucine was confirmed as the only precursor of the three aroma compounds in the cheese with the preferential formation of 3-methylbutanoic acid.

GC-IMS-Based Volatile Characteristic Analysis of Hypsizygus marmoreus Dried by Different Methods

Gas chromatography-ion mobility spectroscopy (GC-IMS) was used to analyze the volatile components in dried Hypsizygus marmoreus of different drying methods, including hot air drying (HAD), heat pump drying (HPD), heated freeze-drying (HFD), and unheated freeze-drying (UFD). A total of 116 signal peaks corresponding to 96 volatile compounds were identified, including 25 esters, 24 aldehydes, 23 alcohols, 13 ketones, 10 heterocyclic compounds, 8 carboxylic acids, 7 terpenes, 3 sulfur-containing compounds, 2 nitrogen-containing compounds, and 1 aromatic hydrocarbon. The total content of volatile compounds in H. marmoreus dried by the four methods, from highest to lowest, was as follows: HAD, HPD, HFD, and UFD. The main volatile compounds included carboxylic acids, alcohols, esters, and aldehydes. Comparing the peak intensities of volatile compounds in dried H. marmoreus using different drying methods, it was found that the synthesis of esters, aldehydes, and terpenes increased under hot drying methods such as HAD and HPD, while the synthesis of compounds containing sulfur and nitrogen increased under freeze-drying methods such as HFD and UFD. Nine common key characteristic flavor compounds of dried H. marmoreus were screened using relative odor activity values (ROAV > 1), including ethyl 3-methylbutanoate, acetic acid, 2-methylbutanal, propanal, methyl 2-propenyl sulfate, trimethylamine, 3-octanone, acetaldehide, and thiophene. In the odor description of volatile compounds with ROAV > 0.1, it was found that important flavor components such as trimethylamine, 3-octanone, (E)-2-octenal, and dimethyl disulfide are related to the aroma of seafood. Their ROAV order is HFD > UFD > HPD > HAD, indicating that H. marmoreus using the HFD method have the strongest seafood flavor. The research findings provide theoretical guidance for selecting drying methods and refining the processing of H. marmoreus.

Quality properties of fish ball with abalone and its relationship with sensory properties

In this work, whiteness, water-holding capacity, gel strength, textural profile analysis were performed to examine the quality of fish balls with abalone (FBA). In addition, a correlation between quality and sensory properties was established. The addition of abalone significantly increased the water holding capacity, gel strength and textural properties of FBA, and decreased their whiteness, the best overall quality was achieved at 9 % w/w abalone addition. The E-nose and E-tongue results revealed that the addition of abalone changed the flavour of FBA. HS-SPME-GC-MS identified 65 volatile organic compounds (VOCs) and proved to be effective in reducing fishy flavour. E-nose can distinguish between the VOCs in FBA. Moreover, Umami and 1-octen-3-ol can serve as important indicators to observe changes in the quality of FBA, as they were positively connected with WHC, gumminess, chewiness, resilience, a*, hexanal, etc. The results provided a theoretical basis for the development of abalone and surimi products.

Production of a Cheese-Like Aroma via Fermentation of Plant Proteins and Coconut Oil with the Basidiomycetes Cyclocybe aegerita and Trametes versicolor

Cheese is one of the most common dairy products and is characterized by its complex aroma. However, in times of climate change and resource scarcity, the possibility to mimic the characteristic cheese-like aroma from plant-based sources is in demand to offer alternatives to cheese. Accordingly, the production of a natural cheese-like aroma via fermentation of four plant-based proteins and coconut oil with basidiomycetes has been addressed. Mixtures of soy and sunflower protein with coconut oil (15 g/L) have shown the formation of a cheese-like aroma after 72 and 56 h after fermentation with Cyclocybe aegerita and Trametes versicolor, respectively. Isovaleric acid, butanoic acid, ethyl butanoate, 1-octen-3-ol, and various ketones were identified as the key odorants. Similarities to typical cheeses were observed by the principal component analysis. Overall, the finding offered an approach to a sustainable production of a natural cheese-like aroma from a plant source, thus contributing to the development of cheese alternatives.

Microbial ecology and metabolite dynamics of backslopped triticale sourdough productions and the impact of scale

Triticale (X Triticosecale Wittmack) is a hybrid of wheat (Triticum aestivum L.) and rye (Secale cereale L.), combining the positive attributes of both cereals. However, it has not been exploited for sourdough production yet. Further, the effect of scale on sourdough production has not been investigated systematically up to now. The aims of the present study were to assess the microbial ecology and metabolomic output of eleven spontaneously fermented, backslopped sourdough productions made with triticale flour on a scale of 100, 200, 500, and 1000 g. The acidification profile [pH and total titratable acidity (TTA)], microbial diversity (culture-dependent and culture-independent), metabolite dynamics, and appropriate correlations were determined. After ten fermentation steps, different species of Lactobacillaceae were prevalent in the mature sourdoughs, in particular Latilactobacillus curvatus, Limosilactobacillus fermentum, and Pediococcus pentosaceus. The microbial diversity could be traced back to the grains and was also present in the milling fractions (flour, bran, and shorts). Furthermore, thanks to the use of Illumina-based high-throughput sequencing and an amplicon sequence variant (ASV) approach, the presence of undesirable bacterial groups (bacilli, clostridia, and enterobacteria) during the initial steps of the backslopping cycle was revealed, as well as a finetuned taxonomic diversity of the LAB genera involved. Small sourdough productions (100 and 200 g) selected for a lower species diversity and reached a stable consortium faster than large ones (500 and 1000 g). Although a comparable final pH of 3.6-4.0 was obtained, the TTA of small sourdoughs was lower than that of large ones. Regarding the metabolic output, the simultaneous production of mannitol and erythritol, beyond ethanol and glycerol, could be linked to sourdoughs in which Liml. fermentum was the sole LAB species present. Further, the use of the arginine deiminase pathway by P. pentosaceus and Liml. fermentum was obvious. An appropriate extraction method followed by liquid injection gas chromatography coupled to triple quadrupole tandem mass spectrometry allowed the quantification of interesting volatile organic compounds, such as ethyl lactate. These findings support the inclusion of triticale as a viable alternative to wheat or rye for the production of sourdoughs that can be integrated into bread-making production schemes.

Flavor Formation in Dry-Cured Fish: Regulation by Microbial Communities and Endogenous Enzymes

Dried salted fish is a traditional dry-cured fish that is sprinkled with salt before the curing process. With a unique flavor as well as diverse varieties, dry-cured fish is popular among consumers worldwide. The presence of various microbial communities during the curing process leads to numerous metabolic reactions, especially lipid oxidation and protein degradation, which influence the formation of flavor substances. However, during industrial curing, the quality of dry-cured fish is difficult to control, leading to the formation of products with diverse flavors. This review describes the curing process of dried salted fish, the key microorganisms involved in the curing process of typical dried salted fish products at home and abroad, and the correlation between biological metabolism and flavor formation and the underlying mechanism. This review also investigates the prospects of dried salted fish products, proposing methods for the analysis of improved curing processes and the mechanisms of dried salted fish. Through a comprehensive understanding of this review, modern production challenges can be addressed to achieve greater control of microbial growth in the system and improved product safety. In addition to advancing our understanding of the processes by which volatile flavor compounds are formed in conventional dry-cured fish products, we expect that this work will also offer a theoretical framework for enhancing their flavor in food processing.

The Screening and Isolation of Ethyl-Carbamate-Degrading Strains from Fermented Grains and Their Application in the Degradation of Ethyl Carbamate in Chinese Baijiu

Ethyl carbamate (EC), a 2A carcinogen produced during the fermentation of foods and beverages, primarily occurs in distilled spirits. Currently, most studies focus on strategies for EC mitigation. In the present research, we aimed to screen strains that can degrade EC directly. Here, we report two Candida ethanolica strains (J1 and J116), isolated from fermented grains, which can reduce EC concentrations directly. These two yeasts were grown using EC as the sole carbon source, and they grew well on different carbon sources. Notably, after immobilization with chitosan, the two strains degraded EC in Chinese Baijiu by 42.27% and 27.91% in 24 h (from 253.03 ± 9.89 to 146.07 ± 1.67 and 182.42 ± 5.05 μg/L, respectively), which was better than the performance of the non-immobilized strains. Furthermore, the volatile organic compound content, investigated using gas chromatography-mass spectrometry, did not affect the main flavor substances in Chinese Baijiu. Thus, the yeasts J1 and J116 may be potentially used for the treatment and commercialization of Chinese Baijiu.

Understanding animal-based flavor generation, mechanisms and characterization: Cheddar cheese and bacon flavors

Natural animal-based flavors have great appeal to consumers and have broad applications in the food industry. In this review, we summarized findings related to bacon and Cheddar cheese flavors' components and their precursors, reaction mechanisms, influential factors, and characterization methods. The results show that free sugars, free amino acids, peptides, vitamins, lipids, and nitrites are precursors to bacon flavor. The conditions governing the formation of bacon flavor are thermally dependent, which facilitates the use of thermal food processing to generate such a flavor. For Cheddar cheese flavor, milk ingredients such as lactose, citrate, fat, and casein are reported as precursors. The optimum conditions to generate Cheddar cheese flavor from precursors are quite strict, which limits its application in food processing. As an alternative, it is more practical to generate Cheddar cheese flavor by combining key aroma compounds using thermal food processing. This review provides the food industry the comprehensive information about the generation of bacon and Cheddar cheese flavors using precursor molecules.

Multi-omics analysis reveals that the metabolite profile of raw milk is associated with dairy cows' health status

The metabolic status of dairy cows directly influences the nutritional quality and flavor of raw milk. A comprehensive comparison of non-volatile metabolites and volatile compounds in raw milk from healthy and subclinical ketosis (SCK) cows was performed using LC-MS, GC-FID, and HS-SPME/GC-MS. SCK can significantly alter the profiles of water-soluble non-volatile metabolites, lipids, and volatile compounds of raw milk. Compared with healthy cows, milk from SCK cows had higher contents of tyrosine, leucine, isoleucine, galactose-1-phosphate, carnitine, citrate, phosphatidylethanolamine species, acetone, 2-butanone, hexanal, dimethyl disulfide and lower content of creatinine, taurine, choline, α-ketoglutaric acid, fumarate, triglyceride species, ethyl butanoate, ethyl acetate, and heptanal. The percentage of polyunsaturated fatty acids in milk was lowered in SCK cows. Our results suggest that SCK can change milk metabolite profiles, disrupt the lipid composition of milk fat globule membrane, decrease the nutritional value, and increase the volatile compounds associated with off-flavors in milk.

Higher CO2 during controlled atmosphere storage of unshelled 'Barton' pecans or carnauba wax coating: Effect on the quality after long-term storage at two temperatures

Pecan nuts, a healthy food, have shown an increased demand for consumption. Therefore, there must be a certain level of care to avoid quality losses, which are primarily influenced by storage conditions and time. This study evaluates the effects of long-term controlled atmosphere (CA) storage with low O₂ partial pressure (pO₂ - 2 kPa), combined or not with high CO₂ (pCO₂ - 40 or 80 kPa), carnauba wax coating (CW), and ambient atmosphere (AMB; control) at 10 and 20 °C, on unshelled 'Barton' pecan nut quality. Color, water activity (A_w), moisture content (MC), and oxidation markers, such as peroxide value (PV), acidity value (AV), TBARS, and volatile compounds (VC) were evaluated. Storage up to twelve months at 10 °C and with CA (regardless of the temperature) ensured higher luminosity and color parameter b* ("golden") and a lower a* parameter ("reddish"). The MC ranged from 2.8 to 3.6%, irrespective of storage conditions, for up to twelve months, which is suitable. The AMB at 10 °C ensured lower AV, TBARS, and PV compared to the CW treatment. Furthermore, CA with low pO₂ and high pCO₂, even at 20 °C, guaranteed lower AV, TBARS, and PV. Storage at 20 °C increased characteristic VCs of lipid oxidation (aldehydes, acids, alcohols, ketones, lactones, and esters, especially with CW coating). However, all conditions at 10 °C and with pCO₂ (even associated at 20 °C) reduced the presence of these VCs. The CW used as a coating on the pecans did not show satisfactory results and should not be recommended for pecan storage at these applied conditions. Our findings showed that low pO₂ and high pCO₂ maintain better pecan quality than O₂ ambient (20 kPa), even at temperatures above refrigeration (20 °C). Nevertheless, there were no significant differences between 40 and 80 kPa CO₂.

Study of volatile compounds profiles in milk matrices using Enterococcus faecalis EstA and Rhizomucor miehei lipase

The use of esterase/lipase enzymes of different origins in food industry is a widely employed strategy to enhance the formation of characteristic aromatic compounds derived from fat and diversify flavour. In the present work, we studied EstA enzyme of Enterococcus faecalis and a high purity Rhizomucor miehei lipase (Palatase). EstA was obtained recombinantly in Escherichia coli BL21 (DE3), and optimum esterase activity was detected at pH 6.75 and 40 °C. We evaluated the effect of the enzymes on milk mixtures prepared with different fat contents (2.8 and 6%) and structure (native or homogenized) on volatile compounds profiles. The milk fat structure before and after the application of low homogenization was characterized by dynamic light dispersion and microscopy. Native milk fat mixtures presented particles of 4.6 μm and 184 nm and homogenized mixtures had particles of 1.4 μm and 258 nm; microscopy images were in concordance with these results. Fifteen volatile compounds were identified, including ketones, esters, alcohols, and acids. We showed the key role of milk fat levels and microstructure in the nature of the volatile compounds produced by the R. miehei enzyme. Both in native or homogenized states, the highest content of fat favored a higher production of acids whereas the lowest fat level favored a higher esters production along with a more balanced volatile profile. For EstA enzyme, results showed a limited action on fat, as biosynthesis of esters only increased with the highest fat level homogenized.

Use of probiotic yeasts with biocontrol activity for fermentation of ewe's milk

BACKGROUND

There are sufficient scienctific studies that support the benefit that fermented dairy products produce in those who consume them. Traditionally, cow's milk has been the most commonly used milk but there is a growing interest in the development of new dairy products, substituting cow's milk with milk from other sources, as well as in the use of microorganisms in fermentation to replace artificial preservatives or treatments that may affect the chemical and organoleptic characteristics of the product. For these reasons, the aim of the present work was to understand the behavior of five potential probiotic yeasts during the fermentation of ewe's milk and to consider their potential use as biocontrol agents.

RESULTS

Saccharomyces cerevisiae 3 and Hanseniaspora osmophila 1056 provided the most promising kinetic parameters in the different salt, temperature and pH conditions tested in their technological characterization. The profiles of organic acids and volatile compounds after the fermentation period was noteworthy for contributing to the final aroma of the dairy product. Sensory analysis revealed the sour taste of all samples, and S. cerevisiae 3, Lachancea thermotolerans 1039, and H. osmophila 1056 stood out for an accentuated cheese flavor. In addition, all strains showed biocontrol activity; they reduced the mycelium of the mycotoxigenic molds.

CONCLUSION

Saccharomyces cerevisiae 3 and H. osmophila 1056 could be inoculated along with bacterial starters to provide a functional fermented beverage with improved flavor. These strains also have an added value as they act as biocontrol agents. © 2022 Society of Chemical Industry.

Health value and keeping quality of chevon from goats fed finisher diets containing hemp (Cannabis sativa L.) seed cake

Wether goats (n = 7) were fed finishing diets containing either 0, 25, 50, 75 or 100 g/kg DM of hempseed cake (HSC) substituting soybean meal to evaluate chevon fatty acid, volatile and oxidative profiles. Feeding HSC diets linearly decreased (P < 0.05) chevon c9-16:1, 16:0, total saturated FA (SFA) and protein oxidation but linearly increased (P < 0.05) t9-18:1, t11-18:1, conjugated linoleic acids, n-3 polyunsaturated FA (PUFA), individual long-chain n-6 PUFA and antioxidant activity. On day 1 and 7 of retail display, diets containing 75 and 100 g/kg DM HSC had greater (P < 0.05) TBARS than the other diet × day interactions. Addition of HSC to the diet increased (P < 0.05) and preserved (P < 0.05) chevon contents of hexanal and methyl caprate throughout the retail display period. Overall, feeding HSC up to 100 g/kg DM enhances chevon profiles of healthful PUFA, desirable flavor volatiles and protein shelf-stability.

Analysis of volatile compounds and flavor fingerprint in hairtail (Trichiurus lepturus) during air-drying using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS)

In the present study, changes in volatile compounds during processing were analyzed using the headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), to investigate the generation of aroma in hairtails (Trichiurus lepturus) during air-drying. Physicochemical indices, such as moisture content and thiobarbituric acid reactive substances (TBARS), were also detected. Flavor fingerprints were studied and developed to distinguish the samples of fresh hairtails (0 day) from air-dried hairtails (2 and 4 days). A total of 75 volatile organic compounds (VOCs) were identified in hairtails, in which alcohols, aldehydes, ketones, and esters were the principal contributors to the formation of the overall flavor of hairtails during air-drying. Seven flavor compounds (ethanol, 3-methyl-1-butanol, 1-pentanol, hexanal, octanal, benzaldehyde, and 3-methylbutanal), two flavor compounds (acetoin and dimethyl sulfide), and eight flavor compounds (1-hexanol, 1-octen-3-ol, nonanal, heptanal, 2-heptanone, ethyl acetate, trimethylamine, and ammonia) were identified in 0, 2, and 4 air-dried hairtails as biomarkers, respectively. The results showed that HS-GC-IMS could detect VOCs in different air-dried hairtails rapidly and comprehensively.

Capturing the impact of oral processing behavior and bolus formation on the dynamic sensory perception and composition of steamed sturgeon meat

The effect of oral processing on flavor release and change in composition of steamed sturgeon meat was investigated. Oral processing caused changes in the concentrations of taste compounds including amino acids, 5'-nucleotides, organic acids, and Na⁺. Sensory omics demonstrated that the concentrations of 12 volatile compounds increased significantly (p < 0.05) during the initial stage of oral processing. There is no significant difference in microstructure, texture, and particle size of meat bolus. The top fifteen differential lipids which including eight phospholipids in all processed samples significantly (p < 0.05) correlated with the flavor release. A total of 589 differential proteins were detected in three samples with different chewing times (0, 12, and 30 s). Analysis of the correlations between odorants and 19 differential proteins was performed. Enriched pathways including fatty acid degradation, valine, leucine and isoleucine degradation, glycine, serine and threonine metabolism, and arachidonic acid metabolism were associated with flavor release during oral processing. This study aimed to investigate potential links between flavor release and biological processes during oral processing from a proteomics perspective.

Relationship between the dynamics of volatile aroma compounds and microbial succession during the ripening of raw ewe milk-derived Idiazabal cheese

Cheese microbiota contributes to various biochemical processes that lead to the formation of volatile compounds and the development of flavour during ripening. Nonetheless, the role of these microorganisms in volatile aroma compounds production is little understood. This work reports for the first time the dynamics and odour impact of volatile compounds, and their relationship to microbial shifts during the ripening of a raw ewe milk-derived cheese (Idiazabal). By means of SPME-GC-MS, 81 volatile compounds were identified, among which acids predominated, followed by esters, ketones and alcohols. The ripening time influenced the abundance of most volatile compounds, thus the moments of greatest abundance were determined (such as 30-60 days for acids). Through Odour Impact Ratio (OIR) values, esters and acids were reported as the predominant odour-active chemical families, while individually, ethyl hexanoate, ethyl 3-methyl butanoate, ethyl butanoate, butanoic acid or 3-methyl butanal were notable odorants, which would provide fruity, rancid, cheesy or malt odour notes. Using a bidirectional orthogonal partial least squares (O2PLS) approach with Spearman's correlations, 12 bacterial genera were reported as key bacteria for the volatile and aromatic composition of Idiazabal cheese, namely Psychrobacter, Enterococcus, Brevibacterium, Streptococcus, Leuconostoc, Chromohalobacter, Chryseobacterium, Carnobacterium, Lactococcus, Obesumbacterium, Stenotrophomonas and Flavobacterium. Non-starter lactic acid bacteria (NSLAB) were highly related to the formation of certain acids, esters and alcohols, such as 3-hexenoic acid, ethyl butanoate or 1-butanol. On the other hand, the starter LAB (SLAB) was related to particular ketones production, specifically 3-hydroxy-2-butanone; and environmental and/or non-desirable bacteria to certain ketones, hydrocarbons and sulphur compounds formation, such as 2-propanone, t-3-octene and dimethyl sulphone. Additionally, the SLAB Lactococcus and Psychrobacter, Brevibacterium and Chromohalobacter were described as having a negative effect on aroma development caused by NSLAB and vice versa. These results provide novel knowledge to help understand the aroma formation in a raw ewe milk-derived cheese.

Changes in Key Aroma Compounds and Esterase Activity of Monascus-Fermented Cheese across a 30-Day Ripening Period

Monascus-fermented cheese (MC) is a new type of mold-ripened cheese that combines a traditional Chinese fermentation fungus, Monascus purpureus M1, with Western cheese fermentation techniques. In this study, the compositions of the volatile aroma compounds in MC were analyzed during a 30-day ripening period using SPME-Arrow and GC-O-MS. The activity of esterase in MC, which is a key enzyme catalyzing esterification reaction, was determined and compared with the control group (CC). Next, sensory analysis was conducted via quantitative descriptive analysis followed by Pearson correlation analysis between esterase activity and the key flavor compounds. A total of 76 compounds were detected. Thirty-three of these compounds could be smelled at the sniffing port and were identified as the key aroma compounds. The esterase activity in MC was found to be 1.24~1.33 times that of the CC. Moreover, the key odor features of ripened MC were alcohol and fruity flavors, considerably deviating from the sour and cheesy features found for the ripened CC. Furthermore, correlation analysis showed that esterase activity was strongly correlated (|r|> 0.75, p < 0.05) with various acids such as pentanoic and nonanoic acids and several aromatic esters, namely, octanoic acid ethyl ester and decanoic acid ethyl ester, revealing the key role that esterases play in developing the typical aroma of ripened MC.

DLLμE/GC-MS as a Powerful Analytical Approach to Establish the Volatilomic Composition of Different Whiskeys

The volatilomic fingerprint of nine different whiskeys was established using a rapid and sensitive analytical approach based on dispersive liquid–liquid microextraction (DLLμE) followed by gas chromatography mass spectrometry detection (GC-MS) and gas chromatography with flame ionization detection (GC-FID). The influence of the extractor solvent on the extraction efficiency of volatile compounds (VOCs) was evaluated by DLLμE/GC-MS. The highest amounts of VOCs were obtained using 5 mL of sample, dichloromethane as the extractor solvent, and acetone as the disperser solvent. The proposed method showed no matrix effect, good linearity (R2 ≥ 0.993) in the assessed concentration range, recovery (ranging from 70 to 99%, precision (RSD ≤ 15%) and sensitivity (low limits of detection and quantification). A total of 37 VOCs belonging to different biosynthetic pathways including alcohols, esters, acids, carbonyl compounds, furanic compounds and volatile phenols were identified and quantified using DLLμE/GC-MS and DLLμE/GC-FID, respectively. Alcohols (3-methylbutan-1-ol, propan-1-ol), esters (ethyl decanoate, ethyl octanoate, ethyl hexanoate), and acids (decanoic acid, octanoic acid, hexanoic acid) were the most abundant chemical families. The multivariate statistical analysis allowed for the discrimination of whiskeys based on their volatilomic fingerprint, namely octanoic acid, 2-furfural, ethyl octanoate, ethyl hexanoate, acetic acid, ethyl dodecanoate, butan-1-ol, and ethyl decanoate.

The Effect of the Ratio of Gamma Aminobutyric Acid-Producing Saccharomyces cerevisiae DL6–20 and Kluyveromyces marxianus B13–5 Addition on Cheese Quality

Kazakh cheese is a traditional dairy product in Xinjiang, China. The function and potential probiotic characteristics of Saccharomyces cerevisiae DL6–20 and Kluyveromyces marxianus B13–5 in Kazakh cheese and its contribution to cheese fermentation was studied. In this study, the effect of the addition ratio of gamma aminobutyric acid (GABA)-producing S. cerevisiae DL6–20 and K. marxianus B13–5 on cheese quality was investigated. Cheeses were prepared by fermentations with a total of six treatments: comercial culture alone as control (CS), a combination with one yeast, either; K. marxianus B13–5 (CSM); S. cerevisiae DL6–20 (CSS); and three different proportions of this two yeasts (CSM:CSS 1:1, 1:2, 2:1). We measured the GABA content of cheese, as well as basic physical and chemical indicators, microbial content, free amino acid (FAA) content, texture, and flavor compound content. The total FAA content of mixed bacteria fermentation was higher than that of the single bacteria alone. The GABA content CSM:CSS 1:2 GABA content was 0.114 g/100 g, CSM:CSS 2:1 GABA content was 0.12 g/100 g, CSM:CSS1:1 content of GABA produced in the late ripening period of cheese was the highest, reaching 0.189 g/100 g and the number of LAB and yeasts in CSM:CSS 1:1 was higher than that of other cheeses. The mixed-strain fermentation generally produced cheeses with a higher protein content than that of the single-strain fermentation in the late stage of the maturation process, especially the protein content of CSM:CSS 1:1 during the ripening period, when the protein content was highest at day 50. CSM:CSS 1:1 had a low moisture content, making it easy to store. With the exception of water and protein content, there is no significant difference in other physical and chemical indicators. CSM:CSS 1:1 contributed to the formation of cheese texture. In addition, multivariate statistical analysis indicated that mixed-strain fermentation was beneficial to the production of cheese aroma, with the aroma production performance of CSM:CSS 1:2 and CSM:CSS 2:1 found to be better than that of CSM: CSS 1:1.

Physicochemical composition, nitrogen fraction and volatile profiles of goat cheese made with artisanal liquid coagulant

In this study, physicochemical composition, nitrogen fractions and volatile compounds of goat cheeses manufactured using artisanal liquid coagulant by four different manufacturers in a mountainous area were investigated. Fresh goat cheeses were characterized by their high fat and high levels of total free amino acids. Volatile profiles were isolated by a solid-phase microextraction technique (SPME/GC-MS) and analyzed by gas chromography-mass spectrometry (GC-MS). In the cheeses, 50 aroma components were identified as ten acids, nine terpens, nine alcohols, eight esters, six aldehydes, five ketones, two volatile phenols and one norisoprenoid with 13 carbon atoms. The major aroma compounds found were nonanoic acid, 2-hexanol and acetoin.

Threadfin bream surimi gel containing squid fin protein hydrolysate: Textural properties, acceptability, and volatile profile

Gel properties of threadfin bream surimi gels with squid fin protein hydrolysate (SFPH) at various concentrations (0, 1, 2, 3, and 4%; w/w) were determined. The gel without SFPH (CON) had the highest breaking force (BrF) and deformation (DeF) as compared to those with SFPH (p < 0.05). Among the gel with SFPH, gel containing 1 and 2% SFPH (SFPH-1 and SFPH-2, respectively) had the highest BrF, whereas the lowest value was obtained when 4% SFPH was used (SFPH-4) (p < 0.05). The whiteness of all samples was slightly decreased with an upsurging amount of SFPH. However, water holding capacity was increased with augmenting levels of SFPH (p < 0.05). Sensory analysis revealed that SFPH-2 had a higher squid odor and flavor likeness score than CON (p < 0.05). Textural properties, especially hardness, were decreased with increasing SFPH, except for SFPH-1 and SFPH-2 (p > 0.05). In addition, the rheological properties, microstructure, and volatile profile of the selected surimi gel were also studied. The storage modulus (G') of SFPH added samples was decreased as compared to the CON sample. The CON gel had a finer and more compact network as compared to SFPH-2 and SFPH-4 samples. Volatile profiles indicated that alcohols, carboxylic acids, ketones, and ether were the major volatile compounds present in both gel samples. Furthermore, thiophene, 3-methyl-, contributing to squid flavor, was found in the SFPH-2 sample. Overall, SFPH at 2% could act as a flavorant in the threadfin bream surimi gel without markedly negative impact on gelling and textural properties, while providing squid odor and flavor to the resulting gel. PRACTICAL APPLICATION: The various low-valued byproducts generated from the squid processing industry could result in various environmental problems. Those byproducts are rich in various biomolecules such as proteins, fats, enzymes, and so forth, which could be utilized to produce value-added products. Among them, protein hydrolysate (PH) rich in amino acids with excellent antioxidant properties could serve as an alternative flavorant. Therefore, PH from squid byproducts, especially fins, could be applied in foods such as fish balls, surimi gels, and so forth to enhance the nutritional and flavoring profile of a finished product. Moreover, bioactive peptides in PH with antioxidant potential could retard the oxidation of proteins and lipids.

Modulation of Metabolome and Overall Perception of Pea Protein-Based Gels Fermented with Various Synthetic Microbial Consortia

Moving to a more sustainable food system requires increasing the proportion of plant protein in our diet. Fermentation of plant product could thus be used to develop innovative and tasty food products. We investigated the impact of fermentation by synthetic microbial consortia (SMC) on the perception of pea protein-based gels, giving possible keys to better understand the origin of sensory perception (e.g., beany, bitter). Two types of pea gels, containing (i) 100% pea proteins and (ii) 50% pea proteins/50% milk proteins, were fermented with three different SMC. Major species developing in both types of gels were Geotrichum candidum, Lactococcus lactis, and Lactobacillus rhamnosus. In pea gels, sensory analyses revealed that bitterness increased after fermentation, which could be due to hydrophobic amino acids resulting from protein hydrolysis, but also decreased pea note intensity in pea gels. In mixed gels, pea perception was similar whatever the SMC, whereas cheesy perception increased. Olfactometry experiments revealed that some specific “green” aroma compounds, responsible for green off-note, were suppressed/reduced by fermentation. The data presented investigated to which extent the design of SMC, together with gels composition (pea gels versus mixed gels), could modulate sensorial perception and drive consumer acceptability.