Reduction of green off-flavor compounds: Comparison of key odorants during fermentation of soy drink with Lycoperdon pyriforme

Variation of volatile compounds and sensory profile for Protaetia brevitarsis larvae fermented with lactic acid bacteria and yeast

This study aimed to investigate the correlation between the composition of volatile compounds, consumer acceptance, and drivers of (dis)liking of Protaetia brevitarsis larvae fermented using lactic acid bacteria and yeast. Volatile compounds were analyzed using HS-SPME-Arrow-GC-MS, and a sensory evaluation was conducted with 72 consumers. A total of 113 volatile compounds were detected, and principal component analysis indicated that the samples could be divided into three groups. The calculated relative odor activity values (ROAV) revealed the presence of 27 compounds (ROAV >1). Volatile compounds with high ROAV were predominantly found during yeast fermentation. The sensory evaluation results indicated a strong correlation between low levels of off-odor intensity and high odor liking, emphasizing that odor profile had a more direct association with consumer acceptance than odor intensity. These findings suggest that yeast fermentation using volatile compounds, which positively influences consumer acceptance, is appropriate for Protaetia brevitarsis larvae.

Exploring the flavor changes in mung bean flour through Lactobacillus fermentation: insights from volatile compounds and non-targeted metabolomics analysis

BACKGROUND

Mung beans are highly nutritious but their leguminous flavor limits their development. Lactic acid bacteria (LAB) fermentation can decrease unwanted bean flavors in legumes and enhance their flavor. This study examined the influence of Lactobacillus fermentation on the flavor characteristics of mung bean flour (MBF) using volatile compounds and non-targeted metabolomics.

RESULTS

Lactobacillus plantarum LP90, Lactobacillus casei LC89, and Lactobacillus acidophilus LA85 eliminated 61.37%, 48.29%, and 43.73%, respectively, of the primary bean odor aldehydes from MBF. The relative odor activity value (ROAV) results showed that fermented mung bean flour (FMBF) included volatile chemicals that contributed to fruity, flowery, and milky aromas. These compounds included ethyl acetate, hexyl formate, 3-hydroxy-2-butanone, and 2,3-butanedione. The levels of amino acids with a fresh sweet flavor increased significantly by 93.89, 49.40, and 35.27% in LP90, LC89, and LA85, respectively. A total of 49 up-regulated and 13 down-regulated significantly differential metabolites were annotated, and ten metabolic pathways were screened for contributing to the flavor. The correlation between important volatile compounds and non-volatile substances relies on two primary metabolic pathways: the citric acid cycle pathway and the amino acid metabolic system.

CONCLUSION

The flavor of MBF was enhanced strongly by the process of Lactobacillus fermentation, with LP90 having the most notable impact. These results serve as a reference for identifying the flavor of FMBF. © 2024 Society of Chemical Industry.

Review of plant-based milk analogue: its preparation, nutritional, physicochemical, and organoleptic properties

In recent years, the market demand for plant-based milk analogues has been rising because of health concerns with bovine milk, like lactose intolerance and hypercholesteremia. Another reason is the lifestyle changes like adopting veganism. This review aims to offer a layout of the manufacturing process and discuss the different properties of plant-based milk analogues. The health benefits offered by the plant-based milk analogues and measures taken to eliminate the existing limitations are also discussed. Sensory profile and stability of plant-based milk analogues which add to the quality of the product were also taken into account and reviewed. The current review's objective is to present a comprehensive, scientifically comparable overview of the preparation procedures, nutritional content, and sensory characteristics of plant-based milk analogues. This is done while keeping in mind the potential of plant-based milk substitutes and associated challenges.

Effect of heat treatment on the release of off-flavor compounds in soy protein isolate

The effects of different heat treatment conditions (65℃ for 30 min, 75℃ for 15 min, and 95℃ for 2, 15 and 30 min) on the evolution of off-flavor compounds in soy protein isolate (SPI) were investigated in terms of lipid oxidation, Maillard reaction and protein structural characteristics. Higher off-flavor concentrations were observed in control and 65℃ treated SPI due to lipoxygenase-mediated enzymatic lipid oxidation. Protein structure played an important role in the release of off-flavors above 65℃. When heated from 75℃ to 95℃ for 2 min, Maillard reaction occurred, glycinin was completely denatured, the particle size increased and the small molecular weight soluble aggregates were formed, resulting in an increase in the content of partial off-flavors. The off-flavor content decreased with time at 95℃, accompanied by the formation of larger molecular weight soluble aggregates. This finding provides practical implications for the beany removal through the SPI structural regulation.

Rapid Acidification and Off-Flavor Reduction of Pea Protein by Fermentation with Lactic Acid Bacteria and Yeasts

Pea protein is widely used as an alternative protein source in plant-based products. In the current study, we fermented pea protein to reduce off-flavor compounds, such as hexanal, and to produce a suitable fermentate for further processing. Laboratory fermentations using 5% (w/v) pea protein suspension were carried out using four selected lactic acid bacteria (LAB) strains, investigating their growth and acidification capabilities in pea protein. Rapid acidification of pea protein was achieved with Lactococcus lactis subsp. lactis strain LTH 7123. Next, this strain was co-inoculated together with either the yeasts Kluyveromyces lactis LTH 7165, Yarrowia lipolytica LTH 6056, or Kluyveromyces marxianus LTH 6039. Fermentation products of the mixed starter cultures and of the single strains were further analyzed by gas chromatography coupled with mass spectrometry to quantify selected volatile flavor compounds. Fermentation with L. lactis LTH 7123 led to an increase in compounds associated with the "beany" off-flavors of peas, including hexanal. However, significant reduction in those compounds was achieved after fermentation with Y. lipolytica LTH 6056 with or without L. lactis LTH 7123. Thus, fermentation using co-cultures of LAB and yeasts strains could prove to be a valuable method for enhancing quality attributes of pea protein-based products.

Optimization of thermal desorption conditions of stir bar sorptive extraction facilitated by machine learning

Stir bar sorptive extraction is an effective technique for trapping odorants, but there are limited studies on the effect of varying thermal desorption conditions on desorption efficiency of odorants. Therefore, we conducted this study to explore the relationship between desorption conditions and desorption efficiency for 18 odorants with diverse physicochemical properties using instrumental analysis and mathematical modeling. We trained four types of machine learning models using a dataset comprising 864 different combinations of four desorption conditions (each three levels) and physicochemical properties. The prediction value of the selected model was validated using a validation dataset of six new odorants. The Random Forest model had the highest performance (R = 0.910). The order of feature importance using this model was as follows: cryo-focusing temperature, molecular weight, log P, boiling point, desorption temperature, desorption time, and helium flow. For testing on new odorants, the correlations between predicted and experimental data for terpene (R = 0.99), alcohol (R = 0.98), ester (R = 0.92), sulfide (R = 0.89), phenol (R = 0.88), and aldehyde (R = 0.61) were determined.

Composition, functional properties, health benefits and applications of oilseed proteins: A systematic review

Common oilseeds, such as soybean, peanut, rapeseed, sunflower seed, sesame seed and chia seed, are key sources of edible vegetable oils. Their defatted meals are excellent natural sources of plant proteins that can meet consumers' demand for health and sustainable substitutes for animal proteins. Oilseed proteins and their derived peptides are also associated with many health benefits, including weight loss and reduced risks of diabetes, hypertension, metabolic syndrome and cardiovascular events. This review summarizes the current status of knowledge on the protein and amino acid composition of common oilseeds as well as the functional properties, nutrition, health benefits and food applications of oilseed protein. Currently, oilseeds are widely applied in the food industry regarding for their health benefits and good functional properties. However, most oilseed proteins are incomplete proteins and their functional properties are not promising compared to animal proteins. They are also limited in the food industry due to their off-flavor, allergenic and antinutritional factors. These properties can be improved by protein modification. Therefore, in order to make better use of oilseed proteins, methods for improving their nutrition value, bioactive activity, functional and sensory characteristics, as well as the strategies for reducing their allergenicity were also discussed in this paper. Finally, examples for the application of oilseed proteins in the food industry are presented. Limitations and future perspectives for developing oilseed proteins as food ingredients are also pointed out. This review aims to foster thinking and generate novel ideas for future research. It will also provide novel ideas and broad prospects for the application of oilseeds in the food industry.

Influence of peeling on volatile and non-volatile compounds responsible for aroma, sensory, and nutrition in ginger (Zingiber officinale)

Industrial use of ginger after peeling results in large amounts of agro-waste. To provide a basic reference for the sustainable processing of ginger products as a spice, we investigated the differences between unpeeled ginger, peeled ginger, and corresponding ginger peel, in terms of aroma, sensory profiles, and nutrition relevant physicochemical properties. The results showed that the total concentrations of identified odor-active compounds in unpeeled ginger, peeled ginger, and ginger peel were 876.56, 672.73, and 105.39 mg/kg, respectively. Unpeeled ginger exhibited more intense citrus-like and fresh impressions compared to peeled ginger, revealed by descriptive sensory analyses. This is relevant to the high odor activity values of odorants such as β-myrcene (pungent, citrus-like), geranial (citrus-like), citronellal (citrus-like, sourish), and linalool (floral, fresh). In parallel, unpeeled ginger contained higher total polyphenol (84.49 mg/100 g) and total sugar content (33.4 g/kg) in comparison with peeled ginger (76.53 mg/100 g and 28.6 g/kg).

Functional Characterization of Fermented Beverages Based on Soy Milk and Sea Buckthorn Powder

Limitations of dairy products, such as lactose intolerance, problems related to a high cholesterol intake in diet, malabsorption, and the requirement for cold storage facilities, as well as an increasing demand for new foods and tastes, have initiated a trend in the development of non-dairy probiotic products. The possibility of producing beverages based on soy milk, sea buckthorn powder, and fermented by Bifidobacterium bifidus (Bb-12^®, Bb) strain at different temperatures (30 °C and 37 °C) was examined. Strain viability, pH, and titratable acidity were measured during the fermentation period while the viability, pH, titratable acidity, and water holding capacity were determined during the storage time at 4 °C ± 1 °C within 14 days. Additionally, the survival and stability of Bb-12^®, inoculated into a functional beverage when exposed to simulated gastrointestinal tract conditions, were assessed. The results obtained in this study revealed that the content of potent bioactive compounds in fermented soy milk and sea buckthorn powder depends on the processing conditions, the bacteria used in the fermentation step, and storage time.

Isolation and Identification of Lactic Acid Bacteria and Their Effects on the Off-odor of Burdocks

Burdocks have diverse nutritional and pharmacological functions, but their unique odor is unwelcome. Here, the effect and mechanism of lactic acid bacteria fermentation on the off-odor of burdocks were investigated. The sensory evaluation showed that burdocks had earthy, musty, grassy, and pepper odors. 2-Isobutyl-3-methoxypyrazine (IBMP) and 2-secbutyl-3-methoxypyrazine (IPMP) mainly contributed to burdock's unique off-odor and were identified by gas chromatography-mass spectrometry combined with headspace-solid phase microextraction (HS-SPME-GC-MS) and relative odor activity value (ROAV) analysis. Weissella cibaria ZJ-5 from screened strains performed with the strongest ability to remove the off-odor and generate a fragrant odor, as determined by sensory evaluation. When incubated aerobically together with IBMP during fermentation, ZJ-5 degraded IBMP directly from 149.56 ± 0.72 to 71.55 ± 1.81 ng/mL. Additionally, linoleic acid content in fermented burdocks was significantly decreased compared with unfermented burdocks. (E,Z)-2,6-Nonadienal, which mainly contributed to fermented burdock's odor, may have been generated from linoleic acid during ZJ-5 fermentation, through the acid catalysis pathway. It indicated that LAB fermentation could improve burdock odor by degrading off-odor compounds and precursors and by generating new aldehydes.

Fermentation for Designing Innovative Plant-Based Meat and Dairy Alternatives

Fermentation was traditionally used all over the world, having the preservation of plant and animal foods as a primary role. Owing to the rise of dairy and meat alternatives, fermentation is booming as an effective technology to improve the sensory, nutritional, and functional profiles of the new generation of plant-based products. This article intends to review the market landscape of fermented plant-based products with a focus on dairy and meat alternatives. Fermentation contributes to improving the organoleptic properties and nutritional profile of dairy and meat alternatives. Precision fermentation provides more opportunities for plant-based meat and dairy manufacturers to deliver a meat/dairy-like experience. Seizing the opportunities that the progress of digitalization is offering would boost the production of high-value ingredients such as enzymes, fats, proteins, and vitamins. Innovative technologies such as 3D printing could be an effective post-processing solution following fermentation in order to mimic the structure and texture of conventional products.

Mechanism and application of fermentation to remove beany flavor from plant-based meat analogs: A mini review

Over the past few decades, there has been a noticeable surge in the market of plant-based meat analogs (PBMA). Such popularity stems from their environmentally friendly production procedures as well as their positive health effects. In order to meet the market demand, it is necessary to look for plant protein processing techniques that can help them match the quality of conventional meat protein from the aspects of sensory, quality and functionality. Bean proteins are ideal options for PBMA with their easy accessibility, high nutrient-density and reasonable price. However, the high polyunsaturated lipids content of beans inevitably leads to the unpleasant beany flavor of soy protein products, which severely affects the promotion of soy protein-based PBMA. In order to solve this issue, various methods including bleaching, enzyme and fermentation etc. are developed. Among these, fermentation is widely investigated due to its high efficiency, less harm to the protein matrix, targeted performance and low budget. In addition, proper utilization of microbiome during the fermentation process not only reduces the unpleasant beany flavors, but also enhances the aroma profile of the final product. In this review, we provide a thorough and succinct overview of the mechanism underlying the formation and elimination of beany flavor with associated fermentation process. The pros and cons of typical fermentation technologies for removing beany flavors are discussed in alongside with their application scenarios. Additionally, the variations among different methods are compared in terms of the strains, fermentation condition, target functionality, matrix for application, sensory perception etc.

A Comparative Analysis of Plant-Based Milk Alternatives Part 1: Composition, Sensory, and Nutritional Value

Consumers are becoming increasingly interested in reducing the consumption of animal-based foods for health, sustainability, and ethical reasons. The food industry is developing products from plant-based ingredients that mimic animal-based foods’ nutritional and sensory characteristics. In this study, the focus is on plant-based milk alternatives (PBMAs). A potential problem with plant-based diets is the deficiency of important micronutrients, such as vitamin B12, B2, and calcium. Therefore, an analysis of micronutrients in PBMAs was conducted to assess their nutritional value. The second main focus was on the sensory description of the PBMAs, done by a trained panel, and instrumental assessment to characterize the sensory attributes. Almond drinks met the daily micronutrient requirements the least, while soy drinks came closest to cow’s milk in macro- and micronutrients. The experimentally determined electronic tongue and volatile compound results confirmed the sensory panel’s evaluations and could therefore be used as a method for easy and effective assessments of PBMAs. The PBMAs evaluated in this study could not completely replace cow’s milk’s nutritional and sensory properties. They are products in their own product group and must be evaluated accordingly. Given the variety of products, consumers should experiment and make their decisions regarding the substitution of cow’s milk.

Surmounting the off-flavor challenge in plant-based foods

Plant-based food products have been receiving an astronomical amount of attention recently, and their demand will most likely soar in the future. However, their unpleasant, intrinsic flavor and odor are the major obstacles limiting consumer's acceptance. These off-flavors are often described as "green," "grassy," "beany," "fatty" and "bitter." This review highlights the presence and formation of common off-flavor volatiles (aldehydes, alcohols, ketones, pyrazines, furans) and nonvolatiles (phenolics, saponins, peptides, alkaloids) from a variety of plant-based foods, including legumes (e.g. lentil, soy, pea), fruits (e.g. apple, grape, watermelon) and vegetables (e.g. carrot, potato, radish). These compounds are formed through various pathways, including lipid oxidation, ethanol fermentation and Maillard reaction (and Strecker degradation). The effect of off-flavor compounds as received by the human taste receptors, along with its possible link of bioactivity (e.g. anti-inflammatory effect), are briefly discussed on a molecular level. Generation of off-flavor compounds in plants is markedly affected by the species, cultivar, geographical location, climate conditions, farming and harvest practices. The effects of genome editing (i.e. CRISPR-Cas9), various processing technologies, such as antioxidant supplementation, enzyme treatment, extrusion, fermentation, pressure application, and different storage and packaging conditions, have been increasingly studied in recent years to mitigate the formation of off-flavors in plant foods. The information presented in this review could be useful for agricultural practitioners, fruits and vegetables industry, and meat and dairy analogue manufacturers to improve the flavor properties of plant-based foods.

Development of probiotics beverage using cereal enzymatic hydrolysate fermented with Limosilactobacillus reuteri

Although most probiotic products are milk based, lactose intolerance and vegetarianism inspired the idea of developing nondairy probiotic products. In this study, probiotic beverages were produced from four enzymatically hydrolyzed cereal substrates (coix seed, quinoa, millet, and brown rice) and fermented by Limosilactobacillus reuteri. Fermentation parameters, including pH, titratable acidity, viable count, organic acids, and volatile components were determined. Results showed that the pH values decreased and titratable acidity increased with the fermentation process (p < .05). Although the final pH in all samples was below 4.0, the growth of L. reuteri was not significantly inhibited by low pH. The number of viable bacteria (12.96 log CFU/ml) in coix seed substrate was significantly higher than that in other samples after the fermentation for 24 h (p < .05). Lactic acid and acetic acid were the main organic acids after fermentation and the highest in quinoa (lactic acid: 7.58 mg/ml; acetic acid: 2.23 mg/ml). The flavor analysis indicated that there were differences in the flavor components of different cereal beverages. Forty‐nine volatile compounds were identified in four beverages, including acids, alcohols, aldehydes, ketones, and esters. The results of the electronic tongue showed that the umami taste of the fermented coix seed was better than that of other samples, displaying the more pleasant taste characteristics. In conclusion, it is feasible to prepare probiotic symbiotic cereal beverage with L. reuteri as starter culture. This study provides a reference for the development of nondairy probiotic products.

Flavor challenges in extruded plant-based meat alternatives: A review

Demand for plant-based meat alternatives has increased in recent years due to concerns about health, ethics, the environment, and animal welfare. Nevertheless, the market share of plant-based meat alternatives must increase significantly if they are to support sustainable food production and consumption. Flavor is an important limiting factor of the acceptability and marketability of plant-based meat alternatives. Undesirable chemosensory perceptions, such as a beany flavor, bitter taste, and astringency, are often associated with plant proteins and products that use them. This study reviewed 276 articles to answer the following five research questions: (1) What are the volatile and nonvolatile compounds responsible for off-flavors? (2) What are the mechanisms by which these flavor compounds are generated? (3) What is the influence of thermal extrusion cooking (the primary structuring technique to transform plant proteins into fibrous products that resemble meat in texture) on the flavor characteristics of plant proteins? (4) What techniques are used in measuring the flavor properties of plant-based proteins and products? (5) What strategies can be used to reduce off-flavors and improve the sensory appeal of plant-based meat alternatives? This article comprehensively discusses, for the first time, the flavor issues of plant-based meat alternatives and the technologies available to improve flavor and, ultimately, acceptability.

Influence of protein extraction and texturization on odor-active compounds of pea proteins

BACKGROUND

The use of plant proteins as food ingredients might be limited due to the presence of foreign or 'off' flavors, which may evolve during extraction and subsequent processing. In this study, the influence of dry (TVP) and wet (WTP) texturization on characteristic volatile compounds of two different pea protein isolates was assessed using gas chromatography-mass spectrometry-olfactometry (GC-MS-O) after direct immersion stir bar sorptive extraction (DI-SBSE).

RESULTS

Twenty-four odor-active compounds were found, with a prevalence of carbonyls from fat oxidation. Nine of these compounds which are also known as major (off-) flavor contributors in peas were distinctively impacted in all texturates: hexanal, nonanal, 2-undecanone, (E)-2-octenal, (E, Z)-3,5-octadiene-2-one, (E, E)-2,4-decadienal, 2-pentyl-furan, 2-pentyl-pyridine, and γ-nonalactone. For example, hexanal, a characteristic green odorant, was reduced by up to sixfold by wet texturization, from 3.29 ± 1.05% (Pea Protein I) to 0.52 ± 0.02% (Pea WTP I). Furthermore, (E,Z)-3,5-Octadiene-2-one and (E,E)-2,4-decadienal were decreased by 1.5- and 1.8-fold when Pea Protein I and Pea TVP I were compared.

CONCLUSION

An overall reduction in fat oxidation products and of green and fatty odor-active compounds was observed. The results represent a first insight into the process-related modulation of pea protein (off-) flavors to broaden the applicability of pea proteins as food ingredients.

Nutritional Function and Flavor Evaluation of a New Soybean Beverage Based on Naematelia aurantialba Fermentation

The soy beverage is a healthy product rich in plant protein; however, its unpleasant flavor affects consumer acceptance. The aim of this study was to determine the feasibility of using Naematelia aurantialba as a strain for the preparation of fermented soybean beverages (FSB). Increases in Zeta potential, particle size, and viscosity make soy beverages more stable. We found that nutrient composition was increased by fermenting N. aurantialba, and the antioxidant activity of soybean beverages significantly increased after 5 days of fermentation. By reducing the content of beany substances such as hexanal and increasing the content of 1-octen-3-ol, the aroma of soybean beverages fermented by N. aurantialba changed from “beany, green, and fatty” to “mushroom and aromatic”. The resulting FSB had reduced bitterness but considerably increased sourness while maintaining the fresh and sweet taste of unfermented soybean beverages (UFSB). This study not only provides a theoretical basis for the market promotion of FSB but also provides a reference for basidiomycetes-fermented beverages.

Characterization of cheesy odor formed during fermentation of soy drink with Agrocybe aegerita

The market for plant protein-based substitutes for cheeses is growing, but the sensory properties are distinctively different from the original products. Hence, natural and vegan cheesy flavors are needed to aromatize the products. A cheesy, sweaty and parmesan-like aroma was produced by fermentation of soy drink with Agrocybe aegerita. Aroma dilution analysis revealed short-chain fatty acids (SCFAs) as main influencing cheesy odorants analyzed by gas chromatography-mass spectrometry-olfactometry. In comparison to the five cheese varieties, the SCFA profile of the fermented soy drink revealed similarities with Parmesan and Emmental cheese. Meanwhile, principal component analysis showed an approximation of the aroma profile after fermentation with A. aegerita to those of cheeses. 3-Methylbutanoic acid was synthesized from the protein fraction, while the oil fraction contributed to the formation of unbranched SCFAs like butanoic acid. Accordingly, the production of these compounds can be increased by addition of the fractions.

Effect of Coix Seed Extracts on Growth and Metabolism of Limosilactobacillus reuteri

Coix seed (Coix lachryma-jobi L.) is an important nourishing food and traditional Chinese medicine. The role of their bioactive constituents in physiology and pharmacology has received considerable scientific attention. However, very little is known about the role of coix seed bioactive components in the growth of Limosilactobacillus reuteri (L. reuteri). This study aimed to evaluate the effects of coix seed extract (CSE) on the growth, acidifying activity, and metabolism of L. reuteri. The results showed that CSE can increase the growth and acidifying activity of L. reuteri compared with the control group. During the stationary phase, the viable bacteria in the medium supplemented with coix seed oil (CSO, 13.72 Log₁₀ CFU/mL), coix polysaccharide (CPO, 12.24 Log₁₀ CFU/mL), and coix protein (CPR, 11.91 Log₁₀ CFU/mL) were significantly higher (p < 0.05) than the control group (MRS, 9.16 Log₁₀ CFU/mL). CSE also enhanced the biosynthesis of lactic acid and acetic acid of L. reuteri. Untargeted metabolomics results indicated that the carbohydrate metabolism, amino acid metabolism, and nucleotide metabolism activities of L. reuteri were increased after adding CSE. Furthermore, CSE increased the accumulation of bioactive metabolites, such as phenyl lactic acid, vitamins, and biotin. Overall, CSE may have prebiotic potential and can be used to culture L. reuteri with high viable bacteria.

Effect of Microbial Fermentation on the Fishy-Odor Compounds in Kelp (Laminaria japonica)

Kelp (Laminaria japonica) is an important marine resource with low cost and rich nutrition. However, its fishy odor has compromised consumer acceptance. In this study, the effects of fermentation with Lactobacillus plantarum FSB7, Pediococcus pentosaceus CICC 21862 and Saccharomyces cerevisiae SK1.008 on fishy notes in kelp was studied using gas chromatography-mass spectrometry (GC-MS), gas chromatography-ion mobility spectrometry (GC-IMS) and odor activity values (OAVs). Forty-four volatile organic compounds (VOCs) were identified in unfermented kelp, most of which were aldehydes, followed by alkanes, alcohols and ketones. Among them were 19 volatile compounds with OAV greater than one. Substances containing α,β-unsaturated carbonyl structure (1-Octen-3-one, (E,Z)-2,6-nonadienal, (E,E)-2,4-decadienal, etc.) are the main contributors to kelp fishy odor. The number of VOCs in kelp samples fermented by L. plantarum, P. pentosaceus and S. cerevisiae were decreased to 22, 24 and 34, respectively. GC-IMS shows that the fingerprint of the S. cerevisiae fermented sample had the most obvious changes. The disappearance of 1-octen-3-one and a 91% decrease in unsaturated aldehydes indicate that S. cerevisiae was the most effective, while L. plantarum and P. pentosaceus only reached 43-55%. The decrease in kelp fishy notes was related to the decrease in α,β-unsaturated carbonyl groups. The experimental results show that odor reduction with fermentation is feasible.

Off-Flavor Removal from Sheep Placenta via Fermentation with Novel Yeast Strain Brettanomyces deamine kh3 Isolated from Traditional Apple Vinegar

Animal placentae can be used as health-promoting food ingredients with various therapeutic efficacies, but their use is limited by their unpleasant odor and taste. This study aimed to investigate the possibility of deodorization of sheep placenta via yeast fermentation. A yeast strain was successfully isolated and identified as a novel Brettanomyces strain (Brettanomyces deamine kh3). The deodorizing efficacy of fermentation of the sheep placenta with B. deamine kh3 was evaluated by 42 panels, based on evaluation of preference, ranking, and aroma profiles, and compared with normal placenta and placenta fermented with B. bruxellensis. The results of the sensory evaluation indicated that fermentation of the sheep placenta with B. deamine kh3 may improve its palatability by increasing flavors such as that of grass (tree), rubber, and burnt, and by decreasing the odor and soy sauce flavor. Solid-phase microextraction-gas chromatography (SPME-GC) showed that major off-flavors in sheep placenta, such as ammonia, dimethyl disulfide, and 1,3-dioxolane, were completely diminished in the sheep placenta fermented with B. deamine kh3. This study presents those major volatile compounds, including 2-isobutyl\-4,4-dimethyl-1,3-dioxane, and 3-methyl-1-butanol, could be crucial in improving the palatability of the sheep placentae fermented with B. deamine kh3. This study provides a good starting point for the industrial application of a new deodorization method.

Off-flavor in soy drink: Development, optimization, and validation of an easy and fast method to quantify the key odorants

A detailed molecular flavor profile was necessary to understand the low acceptance of soy drink by Western consumers. Accordingly, key odor-active compounds were detected by means of aroma dilution analyses coupled with gas chromatography-mass spectrometry-olfactometry after application of suitable solvent-free volatile extraction techniques. Four quantification methods (standard addition, external calibration, internal standard, and stable isotope dilution assay) were developed and validated to measure the concentrations after direct immersion-stir bar sorptive extraction. The quantitative methods provided correctness between 97% and 111% and precision ranging from 78% to 99% for the 21 key odorants. Considering the advantages to be efficient, easy to perform and cheap, internal standard method was further applied to four commercially available soy drinks in Germany. Correlated to a sensory acceptance test (n = 52) contents of 1-octen-3-one, (E,E)-2,4-decadienal and 2-methoxy-4-vinylphenol were suggested to be linked to the aversion of Western consumers to soy drink.

Comparison of the microbial community and flavor compounds in fermented mandarin fish (Siniperca chuatsi): Three typical types of Chinese fermented mandarin fish products

Fermented mandarin fish have been receiving attention from consumers due to their nutritional value and specific flavor. Microbial diversity in fermented mandarin fish has an important impact on their flavor and quality. However, little is known about the microbiome and the differences among different products. In this study, the bacterial profiles and flavor compounds in three typical fermented mandarin fish products were investigated and compared, and a correlation network was used to explore the potential relationship between microorganisms and flavor. Bacterial community analysis demonstrated clear differences in microbiota among the HF-, MF-, and OF-fermented mandarin fish products. Psychrilyobacter, Fusobacterium, and Vibrio were the most dominant in the HF-, MF-, and OF-fermented products, respectively. In addition, 14, 12, and 4 flavor substances (relative odor activity value, ROAV ≥ 1) were detected in the muscles from the central dorsal and ventral sides of the three samples, respectively. Several bacteria correlated with the production of important flavor compounds, and three genera (Arcobacter, Psychrilyobacter, and Shewanella) were the primary microorganisms contributing to more than six characteristic flavor compounds in fermented mandarin fish products. Therefore, the study's systematic method allows identificating important microbes and characteristic volatile flavor compounds in fermented mandarin fish and provides new insights into the relationship between microorganisms and flavor.