Insights into the major aroma-active compounds in clear red raspberry juice (Rubus idaeus L. cv. Heritage) by molecular sensory science approaches

Revealing key aroma compounds and the potential metabolic pathways in sea buckthorn berries

To clarify the aromatic compounds of sea buckthorn and their formation pathways, the key aroma compounds in Hippophae rhamnoides subsp. sinensis were determined first. There were 21 compounds identified as the key aroma components (e.g. ethyl isovalerate, ethyl caproate, ethyl octanoate, 1-hexanol, 1-nonanol, phenylethyl alcohol, nonanal, 6-methyl-5-heptene-2-one) of sea buckthorn, which were mainly composed of esters and alcohols. There were obvious differences in the composition of compounds among Hippophae rhamnoides subsp. sinensis (SI, SS) and Hippophae rhamnoides subsp. thibetana (TS). Esters were the main volatiles of Hippophae rhamnoides subsp. sinensis (SI, SS), while alcohols were the main volatiles of Hippophae rhamnoides subsp. thibetana (TS), which resulted in a lack of overall aromas in TS and a strong fruity and winy odor in SI and SS. The aroma of sea buckthorn could be reproduced well by analyzing key aroma components. Additionally, oleic acid, linoleic acid, leucine, phenylalanine, lycopene, and other compounds generated key aroma compounds by fatty acid oxidation pathway, amino acid degradation pathway, mevalonic acid pathway, methylerythritol phosphate pathway, carotenoid degradation pathway. Therefore, the key aroma compounds in sea buckthorn berries and their metabolic pathways were studied in the paper, which provided the research basis for genetic breeding and fine processing of sea buckthorn.

Comparative metabolomic in-depth exploration of red raspberry: new insights into changes in phytochemicals between different breeds

Based on a non-targeted metabolomic approach, a comprehensive analysis of the metabolic profiles of two raspberry cultivars, Selina (TSM) and Tulameen (CSM), was conducted to explore the potential for further processing of these two varieties. A total of 752 metabolites were identified in both raspberry varieties, with 375 metabolites detected in negative ion mode and additional metabolites identified in positive ion mode. The total number of differential metabolites between TSM and CSM was 62, with orthogonal partial least squares discriminant analysis (OPLS-DA) revealing that the main differential metabolites between the two varieties were phenolic compounds, organic acids, and alkaloids. KEGG pathway analysis identified the top three significantly different metabolic pathways as biosynthesis of amino acids; valine, leucine, and isoleucine biosynthesis; and alanine, aspartate, and glutamate metabolism. In conclusion, this study comprehensively analyzed the metabolic characteristics of TSM and CSM raspberry varieties, providing valuable insights and revealing their potential application prospects. Compared to previous studies, this research provides new insights into the metabolic differences between TSM and CSM cultivars, specifically highlighting newly identified metabolites that were not reported before. These findings include novel differences in phenolic compounds and alkaloids, which play important roles in plant stress response and have potential health benefits. This enhances our understanding of the unique properties of each cultivar and underscores the biological functions of the newly identified metabolites, contributing to the broader field of functional food development.

Lactic acid bacteria sequential fermentation improves viable counts and quality of fermented apple juice via generating two logarithmic phases

This study investigated the impact of lactic acid bacteria (LAB) sequential fermentation on viable counts and apple juice quality. The optimal fermentation conditions were obtained by a step-by-step optimization process, including pH 4.5, temperature 37 °C, the second inoculation time 16 h, total fermentation time 40 h and fermentation sequence (first 21,805 + 21,828, second 20,241). Under the optimal conditions, sequential fermentation allowed LAB to experience two logarithmic phases, increasing viable counts to 1.38 × 108 CFU/mL, exceeding simultaneous fermentation for 24 h and 40 h by 4.10 × 107 CFU/mL and 5.40 × 107 CFU/mL, respectively. This process enhanced sugar utilization, yielding more lactic acid and polyphenols. Furthermore, sequential fermentation improved DPPH (71.71 %) and ABTS (84.79 %) scavenging rates, and enriched volatile compounds, particularly beta-Damascenone, potentially contributing to floral and richer apple flavor. Sequential fermentation also achieved optimal sensory acceptability. This study proposes a novel strategy for high-density LAB fermentation to produce high-quality apple juice.

A comprehensive profiling of phenolic compounds and antioxidant activities of 24 varieties of red raspberry cultivated in Northeast China

Red raspberries, valued for their nutrients and bioactive compounds, have broad uses in processing and healthy products. However, limited comprehensive research focused on the comparison of phenolic compounds of red raspberry, especially species cultivated in Northeast China, has been reported. This study aimed to conduct a thorough investigation of 24 red raspberry varieties in Northeast China for the first time, evaluating their phenolic compounds and antioxidant capacities. The results showed that 'DNS1' had the highest total phenolic content (TPC), 'Willamette' had the highest total flavonoid content (TFC), and 'Boyne' had the highest total anthocyanin content (TAC). Phenolic compounds in red raspberries were predominantly found in esterified form, while glycosylated phenolics should not be overlooked. Chlorogenic acid, cryptochlorogenic acid, ellagic acid, and arbutin were the main phenolic compounds, and the distribution of their contents varied between varieties. The antioxidant activity in the red raspberry had a close association with the content of phenolic compounds. Principal component analysis (PCA) showed that phenolic compounds and antioxidant activities were higher in samples from 'DNS1', 'Boyne', 'Beijing10', 'DNS5', and 'Willamette' varieties. These varieties should be given priority in breeding programs that aim to boost the utility and bioactive profile of red raspberries. PRACTICAL APPLICATION: Red raspberry is becoming a desirable commercially grown fruit species and is viewed as a new functional food. In this context, this research offers strong support for confirming the quality of 24 varieties of red raspberry and plays a critical role in the food industry. It also indicates the potential sources of superior varieties of red raspberry, which are advantageous for growers and consumers in search of high-quality red raspberry varieties.

A Comparative Study of Physicochemical, Aroma, and Color Profiles Affecting the Sensory Properties of Grape Juice from Four Chinese Vitis vinifera × Vitis labrusca and Vitis vinifera Grapes

In order to compare the grape juice sensory properties of four common seedless grape varieties (Kyoho, Summer Black, Moldovan, and Sweet Sapphire) in China, a thorough comparison of these grape varieties was conducted. Physicochemical indicators, aroma, and color characteristics were analyzed and compared to a commercially available not-from-concentrate Concord grape juice. The contents of fructose, glucose, and seven organic acids were evaluated. Kyoho and Sweet Sapphire possessed optimal Brix-acid ratio in the range around 35-40. In terms of aroma, 60 volatiles were identified by GC-MS, including 16 alcohols, 9 terpenes, 6 aldehydes, and 4 ketones. Kyoho demonstrated the highest aroma intensity with superior floral and fruity notes, while Sweet Sapphire showed the lowest aroma intensity with a grassy scent. Additionally, grape pigment profiles were investigated by HPLC-PDA-MS. Summer Black grapes featured a vibrant color, and 52.5% of their anthocyanins were acylated, which helps provide good stability in follow-up processing. Concord juice showed the best overall properties, with the most saturated color and delightful aroma. It was suggested that blending Summer Black with Kyoho could be a promising way to achieve balanced color, taste, and aroma of grape juice. This study provides a feasible and promising combination of Chinese local grapes for making all-round high-quality juice products.

Chemometrics and sensomics-assisted identification of key odorants responsible for retort odor in shelf-stored green tea infusion: A case study of Biluochun

The deterioration of aroma quality in tea beverages during the shelf life is a significant issue. In this study, sensomics techniques were employed to identify the characteristic factor contributing to aroma degradation in green tea infusion. Samples A (no/faint retort odor) and B (high intensity retort odor) were selected based on their retort-like odor intensity after heat treatment simulating shelf-life conditions. The key odorants were identified through a combination of chemometrics analysis, comparative aromatic extract dilution analysis (cAEDA), detection frequency analysis (DFA), and odor-specific magnitude estimation (OSME). Subsequently, eight odorants, including linalool (892.451 μg/L), (E)-β-damascenone (5.105 μg/L), phenylacetaldehyde (27.720 μg/L), nonanal (2201.439 μg/L), α-terpineol (7.166 μg/L), geraniol (0.499 μg/L), theaspirane (0.044 μg/L), and 2-hydroxy-5-methylacetophenone (2.973 μg/L), were identified as the key substances contributing to the retort-like odor in sample B. Aroma recombination and omission test further demonstrated that elevated concentrations of nonanal, geraniol, phenylacetaldehyde, and theaspirane might be the primary reasons for the retort odor observed in samples.

A new raspberry ketone synthesis gene RinPKS4 identified in Rubus idaeus L. by transcriptome analysis

Raspberry ketone accounts for the characteristic aroma of the raspberry fruit. In order to explore the genes involved in raspberry ketone synthesis, the transcriptome in fruit tissues of two red raspberry varieties "Polka" and "Orange legend", were sequenced and 24213 single genes were obtained. As the red raspberry fruit ripening, genes involved in flavonoid and anthocyanin synthesis were up-regulated, while those associated with lignin synthesis were down-regulated. A gene (RinPKS4) highly related to raspberry ketone synthesis was identified by transcriptome analysis, and RinPKS4 gene was over-expressed in raspberry in order to further understand the function of RinPKS4 gene in raspberry ketone synthesis. The results showed that the gene expression level of RinPKS4 in the leaf tissues of a transgenic lines increased by about 4-fold and the content of raspberry ketone increased by 42.64% compared with the wide type. This study lays a theoretical foundation for further study on the synthesis and regulation of raspberry ketone in red raspberry.

Multiomics integrated with sensory evaluations to identify characteristic aromas and key genes in a novel brown navel orange (Citrus sinensis)

'Zong Cheng' navel orange (ZC) is a brown mutant of Lane Late navel orange (LL) and emits a more pleasant odor than that of LL. However, the key volatile compound of this aroma and underlying mechanism remains unclear. In this study, sensory evaluations and volatile profiling were performed throughout fruit development to identify significant differences in sensory perception and metabolites between LL and ZC. It revealed that the sesquiterpene content varied significantly between ZC and LL. Based on aroma extract dilution and gas chromatography-olfactometry analyses, the volatile compound leading to the background aroma of LL and ZC is d-limonene, the orange note in LL was mainly attributed to octanal, whilst valencene, β-myrcene, and (E)-β-ocimene presented balsamic, sweet, and herb notes in ZC. Furthermore, Cs5g12900 and six potential transcription factors were identified as responsible for valencene accumulation in ZC, which is important for enhancing the aroma of ZC.

Effect of osmotic dehydration combined with vacuum freeze-drying treatment on characteristic aroma components of peach slices

Hot air drying (HD), vacuum freeze drying (FD), and pilot-scale freeze drying (PSFD) are extensively used to prepare peach slices. However, the aroma of hot air drying and vacuum freeze-drying is yet to be addressed. In this study, HS-SPME-GC-MS was used to characterize and quantify the volatile compounds in peach slices. First, 33, 36, and 46 volatile compounds were identified and quantified in the HD, FD, and PSFD groups, respectively. PSFD is preferable to HD and FD in terms of the volatile compound types, content, and aroma profiles. PSFD was selected for subsequent permeation and dehydration experiments. The key aroma compounds with an OAV ≥ 1 were found in the PSFD30 group. GC-O analysis was conducted on the PSFD30 group, leading to the preliminary identification of 2-methylbutanal, pentanal, hexanal, 2-hexenal, phenylacetaldehyde, ethyl acetate, 2-methylbutyl acetate, ethyl lactate, linalool, methyl heptenone, and γ-octalactone as distinctive aromas in dried peach slices.

Decoding the Effects of High Hydrostatic Pressure and High-Temperature Short-Time Sterilization on the Volatile Aroma Profile of Red Raspberry Juice

The loss of distinctive aromas due to sterilization significantly hinders efforts to enhance the sensory quality of fruit and vegetable juices. This study aimed to elucidate the impacts of high-hydrostatic pressure (HHP) and high-temperature short-time (HTST) sterilization methods on the loss of C6 aldehyde aroma-active compounds in red raspberry juice. External standard quantification and quantitative descriptive analysis (QDA) revealed a notable decline in the levels of hexanal and (Z)-3-hexenal following the HHP and HTST treatments (p < 0.05), resulting in a marked attenuation of the grassy aroma characteristic of red raspberry juice. Furthermore, a comprehensive examination of the precursors, pivotal enzymes, intermediates, and downstream aromas within the fatty acid metabolism pathway in different raspberry juice samples indicated that the C6 aldehydes loss induced by HHP and HTST sterilizations was primarily ascribed to the competitive inhibition of β-oxidation and the hindered enzymatic oxidation of fatty acids. These insights suggest that modifying sterilization protocols and enhancing enzymatic stability may help preserve the aroma integrity of raspberry juice. Our findings offer practical guidance for optimizing juice processing techniques to maintain flavor.

Overview of the distinctive characteristics of strawberry, raspberry, and blueberry in berries, berry wines, and berry spirits

Red berries have gained popularity as functional and nutritious food due to their health benefits, leading to increased consumer demand and higher production, totaling over 11,000 ktons for strawberries, raspberries, and blueberries combined in 2021. Nutritionally, strawberries, raspberries, and blueberries present high levels of vitamin C (9.7-58.8 mg/100 g dry weight [dw]), folates (6-24 µg/100 g dw), and minerals (96-228 mg/100 g dw). Due to their perishable nature, producers have utilized alcoholic fermentation to extend their shelf life, not only increasing the lifespan of red berries but also attracting consumers through the production of novel beverages. Strawberry, blueberry, and raspberry wines possess low alcohol (5.5-11.1% v/v), high acidity (3.2-17.6 g/L), and interesting bioactive molecules such as phenolic compounds, carotenoids, polysaccharides, and melatonin. Distillation holds tremendous potential for reducing food waste by creating red berry spirits of exceptional quality. Although research on red berry spirits is still in the early stages, future studies should focus on their production and characterization. By incorporating these factors, the production chain would become more sustainable, profitable, and efficient by reducing food waste, capitalizing on consumer acceptance, and leveraging the natural health-promoting characteristics of these products. Therefore, this review aims to provide a comprehensive overview of the characteristics of strawberry, blueberry, and red raspberry in berries, wines, and spirits, with a focus on their chemical composition and production methods.

Microbial inactivation of pressure spray combined with high-voltage electrospray and its application in honey raspberry juice

Pressure spray combined with high-voltage electrospray (PS-ES) has garnered considerable interest as a novel, non-thermal approach for microbial inactivation and preservation of liquid food. This study compared PS-ES with heat treatment (HT) to understand its inactivation mechanism against E. coli and S. aureus in a simulated system. Microbial activity, cell permeability, membrane integrity, membrane potential, and cell membrane structure were assessed. Furthermore, the impact of PS-ES treatment on microbial activity and flavor in honey raspberry juice, was examined. The changes in microbial growth and color during storage were also discussed. The experimental findings revealed that PS-ES treatment effectively reduced the number of E. coli and S. aureus by 1.99 and 1.83 log colony-forming units (CFU/mL). Additionally, it disrupted the integrity of bacterial cell membranes increasing their permeability, which led to the release of cellular proteins and nucleic acids. PS-ES treatment lowered the membrane potential and altered the structure of bacterial proteins. Application of PS-ES in honey raspberry juice reduced bacterial counts from 4.48 log CFU/mL to 1.99 log CFU/mL, with less flavor deterioration compared to HT treatment. After 30 days of storage at 4 °C and room temperature, PS-ES effectively controlled the growth of microorganisms in raspberry juice and maintained the color of the juice.

Factors affecting aroma compounds in orange juice and their sensory perception: A review

Orange juice is the most widely consumed fruit juice globally because of its pleasant aromas and high nutritional value. Aromas, contributed by free and bound aroma compounds, are an important attribute and determine the quality of orange juice and consumer choices. Aldehydes, alcohols, esters, and terpenoids have been shown to play important roles in the aroma quality of orange juice. Many factors affect the aroma compounds in orange juice, such as genetic makeup, maturity, processing, matrix compounds, packaging, and storage. This paper reviews identified aroma compounds in free and bound form, the biosynthetic pathways of aroma-active compounds, and factors affecting aroma from a molecular perspective. This review also outlines the effect of variations in aroma on the sensory profile of orange juice and discusses the sensory perception pathways in human systems. Sensory perception of aromas is affected by aroma variations but also converges with taste perception. This review could provide critical information for further research on the aromas of orange juice and their manipulation during the development of products.

Aroma Components in Horticultural Crops: Chemical Diversity and Usage of Metabolic Engineering for Industrial Applications

Plants produce an incredible variety of volatile organic compounds (VOCs) that assist the interactions with their environment, such as attracting pollinating insects and seed dispersers and defense against herbivores, pathogens, and parasites. Furthermore, VOCs have a significant economic impact on crop quality, as well as the beverage, food, perfume, cosmetics and pharmaceuticals industries. These VOCs are mainly classified as terpenoids, benzenoids/phenylpropanes, and fatty acid derivates. Fruits and vegetables are rich in minerals, vitamins, antioxidants, and dietary fiber, while aroma compounds play a major role in flavor and quality management of these horticultural commodities. Subtle shifts in aroma compounds can dramatically alter the flavor and texture of fruits and vegetables, altering their consumer appeal. Rapid innovations in -omics techniques have led to the isolation of genes encoding enzymes involved in the biosynthesis of several volatiles, which has aided to our comprehension of the regulatory molecular pathways involved in VOC production. The present review focuses on the significance of aroma volatiles to the flavor and aroma profile of horticultural crops and addresses the industrial applications of plant-derived volatile terpenoids, particularly in food and beverages, pharmaceuticals, cosmetics, and biofuel industries. Additionally, the methodological constraints and complexities that limit the transition from gene selection to host organisms and from laboratories to practical implementation are discussed, along with metabolic engineering's potential for enhancing terpenoids volatile production at the industrial level.

Volatilomics of raspberry fruit germplasm by combining chromatographic and direct-injection mass spectrometric techniques

The application of direct-injection mass spectrometric (DI-MS) techniques, like Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR-ToF-MS) has been suggested as a reliable phenotyping tool for fruit volatilome assessment in both genetic and quality-related studies. In this study the complexity of raspberry aroma was investigated by a comprehensive untargeted VOC analysis, done by combining SPME-GC-MS and PTR-ToF-MS assessments with multi-block discriminant analysis using the DIABLO mixOmics framework. The aim was to acquire an exhaustive characterization of the raspberry volatilome according to different fruit ripening stages (pink, ripe, and overripe) and genetic variances (50 accessions), as well as to investigate the potential of PTR-ToF-MS as a rapid and high throughput VOC phenotyping tool to address issues related to raspberry fruit quality. Results of this study demonstrated the complementarity between SPME-GC-MS and PTR-ToF-MS techniques to evaluate the raspberry aroma composition. PTR-ToF-MS generates reliable raspberry VOC fingerprints mainly due to a reduced compound fragmentation and precise content estimation. In addition, the high collinearity between isomers of monoterpenes and norisoprenoids, discovered by GC analysis, reduces the main analytic limitation of PTR-ToF-MS of not being able to separate isomeric molecules. The high similarity between the VOC matrices obtained by applying PTR-ToF-MS and SPME-GC-MS confirmed the possibility of using PTR-ToF-MS as a reliable high throughput phenotyping tool for raspberry volatiolome assessment. In addition, results provided by the germplasm collection investigation enabled to distinguish the best performing accessions, based on VOCs composition, to be used as superior parental lines for future breeding programs.

High-pressure treatment enhanced aromatic compound concentrations of melon juice and its mechanism

Introduction

The flavor deterioration blocks the development of melon juice.

Methods

The effects of ultra-high temperature (UHT) and high pressure (HP) treatments on the aromatic compound concentrations of melon juice and their mechanisms were explored with fresh juice as the control.

Results

A total of 57 volatile compounds were identified by gas chromatography-tandem mass spectrometry analysis. β-ionone was shown to be the major aromatic component of melon juice for the first time. The HP at 200 MPa for 20 min increased the total volatile concentration of melon juice by 1.54 and 3.77 times the control and UHT, respectively. Moreover, the sum concentration of a major aromatic component in the HP treatment was 1.49 and 5.94 times higher than that of the control and UHT, respectively.

Discussion

The HP treatment raised the concentration of volatile and aromatic components of melon juice by reducing their surface tension.

Low-frequency ultrasonic treatment: A potential strategy to improve the flavor of fresh watermelon juice

A molecular sensory science approach was used to explore the effects of ultrasonic treatment on aroma compounds of watermelon juice. Watermelon juice was submitted to ultrasonic power at 325 W for 20 min. Ultrasonic treatment reduced odor related to cucumber and green descriptors, whilst significantly improved odors related to sweet, floral, and fruity descriptors, thus contributing to the overall flavor of watermelon juice. Compared with untreated watermelon juice, the amount and concentration of volatile compounds in ultrasonicated watermelon juice increased by 82.50% and 111.84%, respectively. Notably, 22 alkene compounds were newly formed in ultrasonicated watermelon juice, which contributed to sweet and fruity aroma of watermelon juice. The findings of the present study suggest that ultrasonic treatment may be a potential method to improve the overall flavor of watermelon juice.

Nutrient content prediction and geographical origin identification of red raspberry fruits by combining hyperspectral imaging with chemometrics

The geographical origin and the important nutrient contents greatly affect the quality of red raspberry (RRB, Rubus idaeus L.), a popular fruit with various health benefits. In this study, a chemometrics-assisted hyperspectral imaging (HSI) method was developed for predicting the nutrient contents, including pectin polysaccharides (PPS), reducing sugars (RS), total flavonoids (TF) and total phenolics (TP), and identifying the geographical origin of RRB fruits. The results showed that these nutrient contents in RRB fruits had significant differences between regions (P < 0.05) and could be well predicted based on the HSI full or effective wavelengths selected through competitive adaptive reweighted sampling (CARS) and variable iterative space shrinkage approach (VISSA). The best prediction results of PPS, RS, TF, and TP contents were achieved with the highest residual predictive deviation (RPD) values of 3.66, 3.95, 2.85, and 4.85, respectively. The RRB fruits from multi-regions in China were effectively distinguished by using the first derivative-partial least squares discriminant analysis (DER-PLSDA) model, with an accuracy of above 97%. Meanwhile, the fruits from three protected geographical indication (PGI) regions were successfully classified by using the orthogonal partial least squares discrimination analysis (OPLSDA) model, with an accuracy of above 98%. The study results indicate that HSI assisted with chemometrics is a promising method for predicting the important nutrient contents and identifying the geographical origin of red raspberry fruits.

Identification and confirmation of key compounds causing cooked off-flavor in heat-treated tomato juice

Cooked off-flavor produced by heat treatment greatly limited the acceptability of commercial tomato juice. To screen and identify the cooked off-flavor compounds, gas chromatography-mass spectrometry-olfactometry (GC-MS-O), aroma extract dilution analysis (AEDA), gas chromatography-mass spectrometry (GC-MS), and odor activity value (OAV) calculation were applied simultaneously. The results showed that there were 17 aroma-active compounds in tomato juice samples. Among them, three newly formed sulfur-containing compounds (dimethyl sulfide, dimethyl trisulfide, and methional) and 1-octen-3-one, which exhibited cooked corn/potato, onion, and mushroom odor, were proved to be responsible for the cooked off-flavor in heat-treated tomato juice (HTJ) by omission experiments and electronic nose analysis. The three newly formed sulfur-containing compounds were further confirmed to be the key compounds responsible for the cooked off-flavor in four different tomato cultivars that were commonly consumed in the market. PRACTICAL APPLICATION: Tomato is one of the most popular vegetables in the world and tomato juice is an important part of the tomato industry. However, the cooked off-flavor of tomato juice after sterilization severely restricts its industrial development. This study analyzed and compared the changes of aroma compounds before and after sterilization, and identified and confirmed the major off-flavor components. This work could provide fundamental information for the prevention of cooked off-flavor.

Effects of microbial diversity and phospholipids on flavor profile of caviar from hybrid sturgeon (Huso dauricus × Acipenser schrencki)

Thirty-seven volatiles were identified by gas chromatography-ion mobility spectrometry in sturgeon caviar. Alkenes (37, 43), alcohols (30, 36), aldehydes (9, 10), and esters (11, 13) were detected by two-dimensional gas chromatography-time-off-flight mass spectrometry in fresh and stored caviar, respectively. Alkenes (humulene, caryophyllene, longifolene, and d-limonene), aldehydes (heptanal, hexanal, pentanal, and 3-methyl butanal), and 2-ethyl-1-hexanol were sniffed and described as providing fresh, fatty, and fishy attributes by gas chromatography-olfactometry. The fungal genera of Apiotrichum, Penicillium, Filobasidium, Gibberella, and Cladosporium and 16 bacterial genera were significantly correlated with variations in the contents of 25 aldehydes and 11 ketones. Nine strains, 20 fatty acids, and 69 differential phospholipids were isolated and profiled. Glycerophosphoethanolamine (20:2/20:4), glycerophosphoethanolamine (22:6/22:5), and glycerophosphocholine (16:0/13:0) were significantly associated with the formation of odorants and the proposed mechanism of flavor formation from phospholipids is summarized. This study represents a foundation for achieving targeted preservation and flavor control of caviar.

Free and glycosidically bound aroma compounds in fruit: biosynthesis, transformation, and practical control

Fruit aroma makes an initial flavor impression and largely determines the consumer preference and acceptance of fruit products. Free volatile organic compounds (FVOCs) directly make up the characteristic aromas of fruits. While glycosidically bound volatile compounds (GBVs) can be hydrolyzed during fruit ripening, postharvest storage, and processing, releasing the attached aglycones as free volatiles that could alter the overall aroma attributes of fruits. GBVs typically exhibit significantly higher concentrations than their free counterparts in fruits such as grapes, cherries, kiwifruits, tomatoes, and tamarillos. This review highlights the biosynthesis of FVOCs and GBVs in fruit and illustrates their biological transformations for various functional purposes such as detoxification, aroma enhancement, plant defense, and pollinator attraction. Practical applications for regulating the levels of aroma compounds emitted or accumulated in fruit are also reviewed, emphasizing the metabolic engineering of free volatile metabolites and hydrolytic technologies on aroma glycosides. Generally, enzymatic hydrolysis using AR2000 is a common strategy to enhance the sensory attributes of fruit juices/wines, while acidic hydrolysis induces the oxidation and rearrangement of aglycones, generating artifacts with off-aromas. This review associates the occurrence of free and glycosidic bound volatiles in fruit and addresses their importance in fruit flavor enhancement and industrial applications.

Assessment of chemical constitution and aroma properties of kiwi wines obtained from pure and mixed fermentation with Wickerhamomyces anomalus and Saccharomyces cerevisiae

BACKGROUND

To improve the aroma of kiwi wine through the utilization of Wickerhamomyces anomalus, kiwi juice was fermented using a selected W. anomalus strain in pure culture and mixed fermentations with Saccharomyces cerevisiae, which was inoculated simultaneously and sequentially. The physicochemical indices, volatile compounds and aroma properties of the kiwi wines were assessed.

RESULTS

The study suggested that the ethanol, color indices and organic acids of the wines were closely related to the method of inoculation. Compared with the pure S. cerevisiae fermentation, the mixed fermentations produced more varieties and concentrations of volatiles. The sequential fermentations increased the concentrations of esters and terpenes, improving the flower and sweet fruit notes of the wines. The simultaneous inoculation enhanced the contents of esters and aldehydes, intensifying the flower, sweet and sour fruit of the wines. Partial least-squares regression analysis showed that esters and terpenes contributed greatly to the flower and sweet fruit aroma, whereas aldehydes were the major contributors to the sour note.

CONCLUSION

Based on our results, the mixed fermentations not only enriched the types and concentrations of volatiles, but also had better sensory properties. © 2021 Society of Chemical Industry.

Effect of Issatchenkia terricola WJL-G4 on Deacidification Characteristics and Antioxidant Activities of Red Raspberry Wine Processing

Our previous study isolated a novel Issatchenkia terricola WJL-G4, which exhibited a potent capability of reducing citric acid. In the current study, I. terricola WJL-G4 was applied to decrease the content of citric acid in red raspberry juice, followed by the red raspberry wine preparation by Saccharomyces cerevisiae fermentation, aiming to investigate the influence of I. terricola WJL-G4 on the physicochemical properties, organic acids, phenolic compounds and antioxidant activities during red raspberry wine processing. The results showed that after being treated with I. terricola WJL-G4, the citric acid contents in red raspberry juice decreased from 19.14 ± 0.09 to 6.62 ± 0.14 g/L, which was further declined to 5.59 ± 0.22 g/L after S. cerevisiae fermentation. Parameters related to CIELab color space, including L*, a*, b*, h°, and ∆E* exhibited the highest levels in samples after I. terricola WJL-G4 fermentation. Compared to the red raspberry wine pretreated without deacidification (RJO-SC), wine pretreated by I. terricola WJL-G4 (RJIT-SC) exhibited significantly decreased contents of gallic acid, cryptochlorogenic acid, and arbutin, while significantly increased contents of caffeic acid, sinapic acid, raspberry ketone, quercitrin, quercetin, baicalein, and rutin. Furthermore, the antioxidant activities including DPPH· and ABTS+· radical scavenging were enhanced in RJIT-SC group as compared to RJO-SC. This work revealed that I. terricola WJL-G4 had a great potential in red raspberry wine fermentation.

Characterization of the Aroma-Active Compounds in Banana (Musa AAA Red green) and Their Contributions to the Enhancement of Sweetness Perception

"Hongmeiren" bananas are popular because of their red peel. Two extraction methods solvent-assisted flavor evaporation and headspace solid-phase microextraction, combined with gas chromatography-olfactometry and gas chromatography-mass spectrometry (GC-MS), were used to analyze the volatile components of "Hongmeiren" bananas. A total of 86 aroma compounds were identified by GC-MS, 62 of which were identified as the major aroma-active compounds with an odor activity value ≥ 1 or modified frequency ≥ 30%. Ethyl (E)-2-butenoate, 4-undecanone, and α-phellandrene were found in bananas for the first time. Sensory experiments showed that eight sweet-associated odorants could significantly achieve the sweetness enhancement effect at 30 g/L sucrose solution by odor-induced changes in taste perception. These experiments suggest that selected odorants can achieve sugar reduction, but with consideration of the sugar concentration. The study of the sweetness enhancement effect of individual compounds provides a more direct theoretical support for sugar reduction in the food industry.

The Aroma Fingerprints and Discrimination Analysis of Shiitake Mushrooms from Three Different Drying Conditions by GC-IMS, GC-MS and DSA

The aroma fingerprints and discrimination analysis of shiitake mushrooms under different drying conditions were performed by GC-IMS, GC-MS, and descriptive sensory analysis (DSA) with advanced chemometric methods. Three samples (A, B, and C) were treated with varied drying degree and rate. The sample A and C were at the same drying degree and the sample B and C were at the same drying rate. The GC-IMS volatile fingerprints, including the three-dimensional topographic map, topographic map, and gallery plot, showed that 29 compounds showed higher signal intensities in sample B. Moreover, 28 volatile compounds were identified by HS-SPME-GC-MS and only 8 compounds were ever detected by GC-IMS. The sample B not only had more varieties of volatile compounds, but also showed significant higher contents than sample A and C, especially C8 compounds (p < 0.05). Additionally, sample B showed the highest intensity in mushroom-like, chocolate-like, caramel, sweat, seasoning-like, and cooked potato-like odors by DSA. PCA, fingerprint similarity analysis (FSA) and PLSR further demonstrated that the sample B was different from sample A and C. These results revealed that samples with different drying degree were different and drying degree exerted more influence on the volatile flavor quality than the drying rate. This study will provide a foundation and establish a set of comprehensive and objective methods for further flavor analysis.

Does Organic Farming Increase Raspberry Quality, Aroma and Beneficial Bacterial Biodiversity?

Plant-associated microbes can shape plant phenotype, performance, and productivity. Cultivation methods can influence the plant microbiome structure and differences observed in the nutritional quality of differently grown fruits might be due to variations in the microbiome taxonomic and functional composition. Here, the influence of organic and integrated pest management (IPM) cultivation on quality, aroma and microbiome of raspberry (Rubus idaeus L.) fruits was evaluated. Differences in the fruit microbiome of organic and IPM raspberry were examined by next-generation sequencing and bacterial isolates characterization to highlight the potential contribution of the resident-microflora to fruit characteristics and aroma. The cultivation method strongly influenced fruit nutraceutical traits, aroma and epiphytic bacterial biocoenosis. Organic cultivation resulted in smaller fruits with a higher anthocyanidins content and lower titratable acidity content in comparison to IPM berries. Management practices also influenced the amounts of acids, ketones, aldehydes and monoterpenes, emitted by fruits. Our results suggest that the effects on fruit quality could be related to differences in the population of Gluconobacter, Sphingomonas, Rosenbergiella, Brevibacillus and Methylobacterium on fruit. Finally, changes in fruit aroma can be partly explained by volatile organic compounds (VOCs) emitted by key bacterial genera characterizing organic and IPM raspberry fruits.

Exploring Genotype-by-Environment Interactions of Chemical Composition of Raspberry by Using a Metabolomics Approach

Promoting the consumption of fruits is a key objective of nutrition policy campaigns due to their associated health benefits. Raspberries are well appreciated for their remarkable flavor and nutritional value attributable to their antioxidant properties. Consequently, one of the objectives of present-day raspberry breeding programs is to improve the fruit’s sensory and nutritive characteristics. However, developing new genotypes with enhanced quality traits is a complex task due to the intricate impacts genetic and environmental factors have on these attributes, and the difficulty to phenotype them. We used a multi-platform metabolomic approach to compare flavor- and nutritional-related metabolite profiles of four raspberry cultivars (‘Glen Ample’, ‘Schönemann’, ‘Tulameen’ and ‘Veten’) grown in different European climates. Although the cultivars appear to be better adapted to high latitudes, for their content in soluble solids and acidity, multivariate statistical analyses allowed us to underscore important genotypic differences based on the profiles of important metabolites. ‘Schönemann’ and ‘Veten’ were characterized by high levels of anthocyanins and ellagitannins, respectively, ‘Tulameen’ by its acidity, and ‘Glen Ample’ for its content of sucrose and β-ionone, two main flavor contributors. Our results confirmed the value of metabolomic-driven approaches, which may foster the development of cultivars with enhanced health properties and flavor.

Recent trends in the chromatographic analysis of volatile flavor and fragrance compounds: Annual review 2020

The chromatographic analysis of volatile flavor and fragrance compounds is performed routinely in several industries and in many fields of scientific research. Typical applications include food-, environmental-, essential oil- and cosmetics analysis. Even though the analysis of flavors and fragrances have become increasingly standardized during the past decade, there are still a large variety of techniques that can be used for their extraction, chemical analysis, and sensory analysis. Moreover, there are certain less commonly used techniques that are now being used with increased frequency and that are showing the potential of being used as alternatives to the existing standard techniques. In this annual review, the techniques that were most commonly used in 2020 for the investigation of these volatile compounds are discussed. In addition, a number of emerging trends are discussed, notably the use of solvent assisted flavor evaporation (SAFE) for extraction, GC ion mobility spectrometry (IMS) for volatile compound analysis and electronic senses, that is, E-noses and E-tongues, for sensory analysis. Miscellaneous hyphenated techniques, advances in stationary phase chemistry and a number of interesting applications are also highlighted.

An Insight by Molecular Sensory Science Approaches to Contributions and Variations of the Key Odorants in Shiitake Mushrooms

An insight using molecular sensory science approaches to the contributions and variations of the key odorants in shiitake mushrooms is revealed in this study. Odorants were extracted by headspace solid phase microextraction (HS-SPME) and direct solvent extraction combined with solvent-assisted flavor evaporation (DSE-SAFE) in fresh and hot-air-dried shiitake mushrooms. Among them, 18 and 22 predominant odorants were determined by detection frequency analysis (DFA) and aroma extract dilution analysis (AEDA) combined with gas chromatography-olfactometry (GC-O) in the fresh and dried samples, respectively. The contributions of these predominant odorants in the food matrix were determined by quantification and odor activity values (OAVs) with aroma recombination verification. There were 13 and 14 odorants identified as key contributing odorants to overall aroma, respectively. 1-Octen-3-ol and 1-octen-3-one were the most key contributing odorants in the fresh samples in contributing mushroom-like odor. After hot-air-drying, the OAV and concentrations on dry basis of the key contributing odorants changed, due to oxidation, degradation, caramelization and Maillard reactions of fatty acids, polysaccharides and amino acids. 1-Octen-3-ol was reduced most significantly and degraded to 1-hydroxy-3-octanone, while phenylethyl alcohol increased the most and was formed by phenylalanine. In hot-air-dried samples, lenthionine became the most important contributor and samples were characterized by a sulfury odor. Overall contributions and variations of odorants to the aroma of shiitake mushrooms were revealed at the molecular level.

Characterizing volatile metabolites in raw Pu'er tea stored in wet-hot or dry-cold environments by performing metabolomic analysis and using the molecular sensory science approach

The aroma profile of raw pu'er tea (RPT) depends on its storage duration (2-10 years) and storage conditions (wet-hot or dry-cold environment). We analyzed the major odorants of RPT samples by performing metabolomic analysis and by using the molecular sensory science approach. Under dry-cold storage conditions, tea leaves had more carotenoid derivatives, glycoside-derived volatiles, and phenolic volatiles, resulting in "fresh," "floral," and "sweet" aroma. Under wet-hot storage conditions, tea leaves had more methoxybenzenes, which contributed considerably to their "stale" and "woody" aroma. We identified 11 and 4 compounds as the odor markers of RPTs when stored in dry-cold and wet-hot environments, respectively. Our findings provide a scientific basis for optimal storage that yields the desired aroma profile.

Antioxidant activities and volatile compounds in longan (Dimocarpus longan Lour.) wine produced by incorporating longan seeds

The seeds of dried longan, one of the major processed fruits in Thailand, contain several bioactive compounds. In this study, we developed longan wine by incorporating its seeds during juice preparation and evaluated the antioxidant activities and volatile compounds in different conditions. The results suggested that Saccharomyces cerevisiae EC-1118 was suitable for fermentation of longan juice supplemented with 50% seed and 20% initial soluble solids at an optimal temperature of 30 °C. Different yeast strains showed various extents of antioxidant activities; however, the fermentation temperature and initial soluble solids of longan juice had little effect on the inhibition of reactive species. Antioxidant activities were significantly increased with increasing seed content. Dominant volatile compounds, which were independent of the winemaking conditions, were found to be phenethyl alcohol, 2,3-butylene glycol, 5-hydroxymethyl-2-furaldehyde, ethyl hydrogen succinate, and 4-hydroxyphenethyl alcohol. These compounds highly influenced the antioxidant activities of longan wine produced by incorporating the seeds.

Nanoencapsulation of anthocyanins-loaded β-lactoglobulin nanoparticles: Characterization, stability, and bioavailability in vitro

This work aims to investigate the effect of desolvation on the stability and bioavailability of nanoparticles of β-lactoglobulin (β-Lg) and anthocyanins (AC) extracted from red raspberry pomace. Interactions between the substrates were also studied using multispectral approaches. β-Lg-nanoparticles were fabricated via heat treatment at 85 °C for 30 min before initiating the desolvation method at pH 7. This method generated monodisperse particles, nano-scale size of β-Lg, and AC-β-Lg ranged from 129.13 to 351.85 nm with square morphology obtained by SEM. The AC extract was encapsulated successfully during desolvation process into β-Lg-nanoparticles with encapsulation efficiency (EE %) of ~77%. Results also showed that AC (from 1 to 13 × 10^-4 M) quenched the fluorescence intensity of de-solvated β-Lg estimated to be 98%, and a binding among them occurred with a K_a-value of 7.59 × 10⁸ M^-1 at 25 °C. Addition of AC also gradually increased the antioxidant activity of β-Lg-nanoparticles with values of 82.51% at the highest AC-concentration (13 × 10^-4 M) loaded on β-Lg-nanoparticles. AC-loaded β-Lg nanoparticles was more stable in mouth (pH 6.8), simulated gastric (SG, pH 2), and simulated intestinal (SI, pH 6.9) by showing high retention rate (%) than that of AC unencapsulated. Overall, de-solvated-β-Lg increased the heat-stability and bioavailability of AC, which could be further utilized in various food and pharmaceutical matrices. These findings recommend that β-Lg nanoparticles could be appropriated as delivery systems for anthocyanins.