The m6A reader SlYTH2 negatively regulates tomato fruit aroma by impeding the translation process.

N6-methyladenosine (m6A) is a fundamentally important RNA modification for gene regulation, whose function is achieved through m6A readers. However, whether and how m6A readers play regulatory roles during fruit ripening and quality formation remains unclear. Here, we characterized SlYTH2 as a tomato m6A reader protein and profiled the binding sites of SlYTH2 at the transcriptome-wide level. SlYTH2 undergoes liquid-liquid phase separation and promotes RNA-protein condensate formation. The target mRNAs of SlYTH2, namely m6A-modified SlHPL and SlCCD1B associated with volatile synthesis, are enriched in SlYTH2-induced condensates. Through polysome profiling assays and proteomic analysis, we demonstrate that knockout of SlYTH2 expedites the translation process of SlHPL and SlCCD1B, resulting in augmented production of aroma-associated volatiles. This aroma enrichment significantly increased consumer preferences for CRISPR-edited fruit over wild type. These findings shed light on the underlying mechanisms of m6A in plant RNA metabolism and provided a promising strategy to generate fruits that are more attractive to consumers.

Mechanisms underlying the formation of main volatile odor sulfur compounds in foods during thermal processing.

Volatile sulfur compounds (VSCs) significantly influence food flavor and garner considerable attention in flavor research due to their low sensory thresholds, diverse odor attributes, and high reactivity. Extensive research studies have explored VSC formation through thermal processes such as the Maillard reaction, thermal pyrolysis, oxidation, and enzymatic reactions. However, understanding of the specific reaction mechanisms and processes remains limited. This is due to the dispersed nature of existing studies, the undefined intermediates involved, and the complexity of the matrices and processing conditions. Given these limitations, the authors have shifted their focus from foods to sulfides. The structure, source, and chemical characteristics of common precursors (sulfur-containing amino acids and derivatives, thiamine, thioglucoside, and lentinic acid) and their corresponding reactive intermediates (hydrogen sulfide, thiol, alkyl sulfide, alkyl sulfenic acid, and thial) are provided, and the degradation mechanisms, reaction rules, and matrix conditions are summarized based on their chemical characteristics. Additionally, the VSC formation processes in several typical foods during processing are elucidated, adhering to these identified rules. This article provides a comprehensive overview of VSCs, from precursors and intermediates to end products, and is crucial for understanding the mechanisms behind VSC formation and managing the flavor qualities of processed foods.

Characterization of Volatile Organic Compounds in Five Celery (Apium graveolens L.) Cultivars with Different Petiole Colors by HS-SPME-GC-MS.

Celery (Apium graveolens L.) is an important vegetable crop cultivated worldwide for its medicinal properties and distinctive flavor. Volatile organic compound (VOC) analysis is a valuable tool for the identification and classification of species. Currently, less research has been conducted on aroma compounds in different celery varieties and colors. In this study, five different colored celery were quantitatively analyzed for VOCs using HS-SPME, GC-MS determination, and stoichiometry methods. The result revealed that γ-terpinene, d-limonene, 2-hexenal,-(E)-, and ß-myrcene contributed primarily to the celery aroma. The composition of compounds in celery exhibited a correlation not only with the color of the variety, with green celery displaying a higher concentration compared with other varieties, but also with the specific organ, whereby the content and distribution of volatile compounds were primarily influenced by the leaf rather than the petiole. Seven key genes influencing terpenoid synthesis were screened to detect expression levels. Most of the genes exhibited higher expression in leaves than petioles. In addition, some genes, particularly AgDXS and AgIDI, have higher expression levels in celery than other genes, thereby influencing the regulation of terpenoid synthesis through the MEP and MVA pathways, such as hydrocarbon monoterpenes. This study identified the characteristics of flavor compounds and key aroma components in different colored celery varieties and explored key genes involved in the regulation of terpenoid synthesis, laying a theoretical foundation for understanding flavor chemistry and improving its quality.

Cellular antioxidant mechanism of mannan-oligosaccharides involving in enhancing flesh quality in grass carp (Ctenopharyngodon idella).

BACKGROUND: Deterioration of flesh quality has bad effects on consumer satisfaction. Therefore, effects of safe mannan-oligosaccharides (MOS) on flesh quality of grass carp (Ctenopharyngodon idella) muscle were studied. A total of 540 healthy fish (215.85 ± 0.30 g) were randomly divided into six groups and fed six separate diets with graded levels of MOS (0, 200, 400, 600, 800 and 1000 mg kg-1 ) for 60 days. This study aimed at investigating the benefits of dietary MOS on flesh quality (fatty acids, amino acids and physicochemical properties) and the protection mechanism regarding antioxidant status. RESULTS: Optimal MOS could improve tenderness (27.4%), pH (5.5%) while decreasing cooking loss (16.6%) to enhance flesh quality. Meanwhile, optimal MOS improved flavor inosine 5'-monophosphate (IMP) of 11.8%, sweetness and umami-associated amino acid, healthy unsaturated fatty acid (UFA) of 14.9% and n-3 polyunsaturated fatty acids (n-3 PUFAs) especially C20:5n-3 (15.8%) and C22:6n-3 (38.3%). Furthermore, the mechanism that MOS affected pH, tenderness and cooking loss could be partly explained by the reduced lactate, cathepsin and oxidation, respectively. The enhanced flesh quality was also associated with enhanced antioxidant ability concerning improving antioxidant enzymes activities and the corresponding transcriptional levels, which were regulated through NF-E2-related factor 2 (Nrf2) and target of rapamycin (TOR) signaling. Based on pH24h , cooking loss, shear force and DHA (docosahexaenoic acid, C22:6n-3), optimal MOS levels for grass carp were estimated to be 442.75, 539.53, 594.73 and 539.53 mg kg-1 , respectively. CONCLUSION: Dietary MOS is a promising alternative strategy to improve flesh quality of fish muscle. © 2022 Society of Chemical Industry.

Special tea products featuring functional components: Health benefits and processing strategies.

The functional components in tea confer various potential health benefits to humans. To date, several special tea products featuring functional components (STPFCs) have been successfully developed, such as O-methylated catechin-rich tea, γ-aminobutyric acid-rich tea, low-caffeine tea, and selenium-rich tea products. STPFCs have some unique and enhanced health benefits when compared with conventional tea products, which can meet the specific needs and preferences of different groups and have huge market potential. The processing strategies to improve the health benefits of tea products by regulating the functional component content have been an active area of research in food science. The fresh leaves of some specific tea varieties rich in functional components are used as raw materials, and special processing technologies are employed to prepare STPFCs. Huge progress has been achieved in the research and development of these STPFCs. However, the current status of these STPFCs has not yet been systematically reviewed. Here, studies on STPFCs have been comprehensively reviewed with a focus on their potential health benefits and processing strategies. Additionally, other chemical components with the potential to be developed into special teas and the application of tea functional components in the food industry have been discussed. Finally, suggestions on the promises and challenges for the future study of these STPFCs have been provided. This paper might shed light on the current status of the research and development of these STPFCs. Future studies on STPFCs should focus on screening specific tea varieties, identifying new functional components, evaluating health-promoting effects, improving flavor quality, and elucidating the interactions between functional components.

PacBio sequencing reveals bacterial community diversity in cheeses collected from different regions.

Cheese is a fermented dairy product that is popular for its unique flavor and nutritional value. Recent studies have shown that microorganisms in cheese play an important role in the fermentation process and determine the quality of the cheese. We collected 12 cheese samples from different regions and studied the composition of their bacterial communities using PacBio small-molecule real-time sequencing (Pacific Biosciences, Menlo Park, CA). Our data revealed 144 bacterial genera (including Lactobacillus, Streptococcus, Lactococcus, and Staphylococcus) and 217 bacterial species (including Lactococcus lactis, Streptococcus thermophilus, Staphylococcus equorum, and Streptococcus uberis). We investigated the flavor quality of the cheese samples using an electronic nose system and we found differences in flavor-quality indices among samples from different regions. We found a clustering tendency based on flavor quality using principal component analysis. We found correlations between lactic acid bacteria and the flavor quality of the cheese samples. Biodegradation and metabolism of xenobiotics, and lipid-metabolism-related pathways, were predicted to contribute to differences in cheese flavor using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). This preliminary study explored the bacterial communities in cheeses collected from different regions and their potential genome functions from the perspective of flavor quality.

Simultaneous determination of diethylacetal and acetaldehyde during beer fermentation and storage process.

BACKGROUND: Acetaldehyde is an important flavor component in beer which is possibly carcinogenic to humans. Owing to the limitations of present detection methods, only free-state acetaldehyde in beers has been focused on, while acetal in beers has hardly been reported so far. RESULTS: A sensitive headspace gas chromatography method was developed for the determination of diethylacetal and acetaldehyde in beer. The column DB-23 was chosen with a total run time of 22.5 min. The optimal addition amount of NaCl, equilibrium temperature and equilibrium time were 2.0 g, 70 °C and 30 min respectively. For both diethylacetal and acetaldehyde analyses, the limit of detection was 0.005 mg L-1 with relative standard deviation < 5.5%. The recoveries of acetaldehyde and diethylacetal were 95-110 and 95-115% respectively. The diethylacetal and acetaldehyde average contents in 24 beer products were 11.83 and 4.36 mg L-1 respectively. The Pearson correlation coefficient between diethylacetal and acetaldehyde was the highest (0.963). Both diethylacetal and acetaldehyde contents increased to a peak value after fermentation for 3 days and then decreased to a lower value. During both normal and forced aging storage, the diethylacetal content decreased and the acetaldehyde content increased gradually over time. When beers were forced aged for 4 days, the increased ratio of acetaldehyde could be above 40.00%. CONCLUSION: The newly established method can be used to assess acetaldehyde level and flavor quality in beer more scientifically. © 2018 Society of Chemical Industry.

Discrepancy on the flavor compound affect the quality of Taiping Houkui tea from different production regions.

Taiping Houkui (TPHK) is prevalent green tea in China, its flavor quality is significantly influenced by different production regions. However, the key flavor compounds responsible for these discrepancies remain unclearly. Here, TPHK samples were produced from fresh leaves of 'Shidacha 2' cultivar planted in 14 distinct production regions. In 14 TPHK samples, a total of 33 non-volatile compounds were identified and quantified. Partial least-squares discriminant analysis (PLS-DA) reveal that theanine and glutamate were the main umami compounds, caffeine imparted with bitterness, which collectively contributed to the variation in the taste flavor of TPHK across different production regions. Furthermore, the profiles of 51 volatile compounds were determined, integrated PLS-DA with odor activity values of volatiles indicated that linalool (165.7-888.5) and geraniol (11.9-141.4) affecting the floral aroma of TPHK among different production regions. Our findings revealed the critical compounds that contributed to the effect of production regions on flavor quality of TPHK.

Re-rolling treatment in the fermentation process improves the taste and liquor color qualities of black tea.

Fermentation is a vital process occurred under the premise of rolling affecting black tea quality. Theoretically, re-rolling during fermentation will remodel the biochemical conditions of tea leaves, and thus influence black tea quality. Herein, we studied the effect of re-rolling on black tea taste and liquor color. Sensory evaluation showed that re-rolling significantly weakened the astringency taste and improved the redness and luminance of liquor. With re-rolling, the color attributes of a* and L* and the contents of theaflavins and thearubigins were significantly improved. Metabolomics analysis showed that the contents of 110 non-volatile compounds were significantly different among black teas with different rolling treatments. In summary, re-rolling accelerated the oxidation of polyphenols into pigments, the hydrolysis of proteins into amino acids, and the metabolism of alkaloids, organic acids, glycosidically-bound volatiles, and lipids during the fermentation period. Our study provided a novel and simple way to improve black tea quality.

Effect of tea stems on the quality formation of large-leaf yellow tea: Sensomics and flavoromics approaches.

In this study, the stems (ST) and leaves (LT) isolated from Large-leaf yellow tea (LYT) were used for sensory evaluation and quantitative analysis of flavor metabolites by sensomics and flavoromics. The results showed that the flavors of ST and LT in LYT were significantly different, and ST had stronger roasty and nutty aroma and sweet taste, which was mainly due to the accumulation of higher theanine and soluble monosaccharides in ST, and provided more substrates for the production of more pyrazine by the Maillard reaction; whereas LT contributed to the mellow and thick taste quality of LYT, and the abundance of catechins and caffeine were the main reason. The metabolic patterns of flavor metabolites indicated that the flavor differences between ST and LT were mainly due to biological metabolism in tea plants. This study provides the selection of raw materials for LYT in the future and product development of tea stems.

Insight into flavor changes in bighead carp (Aristichthys nobilis) fillets during storage based on enzymatic, microbial, and metabolism analysis.

The flavor alterations in bighead carp subjected to varying storage temperatures and the underlying metabolic mechanism were elucidated. Analysis of volatile flavor compounds, electronic nose, free amino acids, ATP-related compounds, and sensory evaluations uncovered a progressive flavor deterioration during storage, especially at 25 °C. Metabolomics-based flavor relating component profiling analysis showed that free fatty acids formed various fatty aldehydes including (E, E)-2,4-heptadienal and nonanal under lipoxygenase catalysis. Alcohol dehydrogenase and alcohol acyltransferases were intimately involved in alcohol and ester generation, while alkaline phosphatase, 5'-nucleotidase, and acid phosphatase were closely associated with IMP, Hx, and HxR conversion, respectively. Aeromonas, Serratia, Lactococcus, Pseudomonas, and Peptostreptococcus notably influenced flavor metabolism and enzyme activities. The metabolism disparities of valine, leucine, isoleucine, lysine, and α-linolenic acid could be the primary factors contributing to flavor metabolism distinctions. This study offers novel insights into the flavor change mechanisms and potential regulation strategies of bighead carp during storage.

Exploring the influence and mechanism of different frying methods on the flavor quality of low-salt sour meat.

To obtain nutritious, healthy, and flavor-enriched sour meat products, the effects of different frying methods (microwave, air-frying, and traditional frying) on the flavor quality of low-salt sour meat were evaluated using metabolomics and other flavor analysis techniques. The pH value of the sour meat rose dramatically, while the TBARS value dropped significantly after frying. E-nose and E-tongue results showed that air-frying could reduce acidity and improve umami. The comprehensive analysis of all samples revealed the identification of 107 volatile flavor compounds, including 10 unique aroma compounds that were specifically detected in the AF group. Additionally, the air frying process notably increased the free amino acid and nucleotide concentrations in sour meat by 53.58% and 159.29%, respectively, while causing a significant reduction in both fatty acid and lactic acid content by 22.84% and 49.29%, respectively. All three frying methods altered the flavor of the samples, but air frying performed better in terms of flavor and texture.

Utilization of low-temperature heating method to improve skim milk production: Microstructure, stability, and constituents of milk fat globule membrane.

In the process of defatting milk, preheating treatment is an important factor affecting the flavor of skim milk. Here, raw milk was preheated at different times and temperatures. Then laser confocal microscopy, multiple-light scattering instrument, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to analyze the microstructure of milk fat globule membrane (MFGM), milk stability, and MFGM protein (MFGMP) components. Results showed that phospholipid domain of MFGM changed from an ordered state (Lo) to a disordered state (Ld) with increase in treatment temperature and time, leading to an increase in MFGMP content in skim milk. During the stability test, the stability of raw milk decreased significantly with increase in preheating temperature, while the opposite was true for skim milk. Finally, the results of MFGMP differentiation analysis showed that, the content of ten taste-related MFGMPs in the control group samples was significantly lower compared to the optimal group (P < 0.05).

High temperature and nib acidification during cacao-controlled fermentation improve cadmium transfer from nibs to testa and the liquor's flavor.

Migration of nib Cd to the testa during fermentation can be achieved with high temperatures (> 45 °C) and low nib pH values (< 5.0) using spontaneous fermentation. However, this low pH can lead to low flavor quality. This study used three controlled temperature fermentation treatments on three cacao genotypes (CCN 51, ICS 95, and TCS 01) to test its effects on the nib pH, the migration of nib Cd to the testa, and the liquor flavor quality. All treatments were effective in reducing the total nib Cd concentration. Nevertheless, the treatment with the higher mean temperature (44.25 °C) and acidification (pH 4.66) reached the highest mean nib Cd reductions throughout fermentation, a 1.37 factor in TCS 01, promoting the development of fine-flavor cocoa sensorial notes. In unfermented beans, the Cd concentration of nibs was higher than that of the testa, and the Cd migration proceeded down the total concentration gradient. However, Cd migration was observed against the concentration gradient (testa Cd > nib Cd) from the fourth day. Cd migration could increase by extensive fermentation until the sixth day in high temperatures and probably by the adsorbent capacity of the testa. Genotype-by-treatment interactions were present for the nib Cd reduction, and a universal percentage of decrease of Cd for each genotype with fermentation cannot be expected. Selecting genotypes with highly adsorbent testa combined with controlled temperatures would help reduce the Cd concentration in the cacao raw material, improving its safety and quality.

Volatile metabolomics reveals the characteristics of the unique flavor substances in oats.

Oats is a cereal well known for its high nutritional value and unique flavor. This study investigated the metabolomics data from oats, wheat, and barley using broadly targeted GC-MS metabonomic techniques. A total of 437 volatile organic compounds (VOCs) were identified, of which 414 were shared metabolites, with three metabolites unique to oats. Three hundred and seven differentially accumulated metabolites (DAMs) were screened from all the comparison groups, of which 27 metabolites were shared by oats and barley, and 121 shared by oats and wheat. Terpenoids and esters were the key metabolites determining the differences in flavor. A KEGG analysis indicated that the alpha-linolenic acid and phenylalanine pathways were the most significant metabolic pathways. The 42 DAMs found may be the main substances leading to the flavor differences between the different varieties. Overall, this study reveals the main reasons for the unique flavor of oats through metabolomic evidence.

Metabolomics reveal changes in flavor quality and bioactive components in post-ripening Torreya grandis nuts and the underlying mechanism.

Secondary metabolites are a group of small molecules with critical roles in plants fitness in addition to their potential bioactivities in humans. Most of these compounds are associated with the flavor and quality formation of fruits or nuts during the development or the postharvest stages. Change in metabolic profiles and shifts underpinning the post-ripening process in T. grandis nuts are not yet reported. In this study, a large scale untargeted metabolomics approach was employed in T. grandis nuts, revealing for a total of 140 differential accumulated metabolites. Among them, nearly 60% of metabolites belonging to terpenoids, coumarins and phenolic acids, and phytohormones were showed a gradual accumulation pattern, while most of compounds in flavonoids were decreased during post-ripening. An in-depth analysis of changes in these metabolite classes suggest a framework for post-ripening process effect associated with the postharvest quality of T. grandis nuts for the first time.

Inoculation strategies affect the physicochemical properties and flavor of Zhenjiang aromatic vinegar.

Inoculation strategy is a significant determinant of the flavor quality of Zhenjiang aromatic vinegar. Herein, the comparative analyses of the effects of various inoculation strategies on the physicochemical properties, microbial community structure, and flavoring characteristics of Zhenjiang aromatic vinegar were performed. The results showed that the contents of total acid (6.91 g/100 g), organic acid (2099.63 ± 4.13 mg/100 g) and amino acid (3666.18 ± 14.40 mg/100 g) in the direct inoculation strategy were higher than those in the traditional inoculation strategy (6.21 ± 0.02 g/100 g, 1939.66 ± 4.16 mg/100 g and 3301.46 ± 13.41 mg/100 g). At the same time, it can effectively promote the production of acetoin. The diversity of strains under the traditional inoculation strategy was higher than that under the direct inoculation strategy, and the relative abundance of major microbial genera in the fermentation process was lower than that under the direct inoculation strategy. In addition, for two different inoculation strategies, pH was proved to be an important environmental factor affecting the microbial community structure during acetic acid fermentation. The correlation between main microbial species, organic acids, non-volatile acids, and volatile flavor compounds is more consistent. Therefore, this study may help to develop direct injection composite microbial inoculants to replace traditional starter cultures in future research.

Effects of Konjac Glucomannan/ε-Polylysine Hydrochloride/Ferulic Acid Composite Coating on the Freshness Preservation Performance and Flavor of Refrigerated Sea Bass Fillets.

Coating preservation has a remarkable effect on the preservation of aquatic products. This work prepared a composite coating using konjac glucomannan (KGM) as the film-forming matrix and ε-polylysine hydrochloride (ε-PL) and ferulic acid (FA) as the preservative. Three types of treated sea bass (KGM, KGM-ε-PL, and KGM-ε-PL-FA) and untreated sea bass were stored at 4 °C for 20 days to compare freshness changes under different treatment conditions. The results showed that the surface color and texture of sea bass in refrigerated storage changed dramatically and deteriorated as storage time increased. The composite coating treatment was significantly different from the control group. Using Gas-phase ion migration spectrometry (GC-IMS) technology, 32 volatile compounds, such as aldehydes, alcohols, and ketones, were found in fillets during flavor quality analysis. The composite coating can successfully inhibit the formation of odor compounds such as 2-nonenone, isoamyl alcohol monomer, ammonia, and trimethylamine, delaying the deterioration of fish and improving freshness. Among them, KGM-ε-PL-FA composite coating has the most remarkable preservation performance, which significantly inhibits the occurrence of rotten odor, and has a potential application prospect in the field of food preservation.

Dietary supplementation with honeycomb extracts positively improved egg nutritional and flavor quality, serum antioxidant and immune functions of laying ducks.

Introduction: Honeycomb is a traditional natural health medicine and has antioxidant, antibacterial, anti-inflammatory, antiviral and antitumor activities. It is currently unclear whether honeycomb extract supplementation has positive effects on the intensive farming laying duck production. This study aims to evaluate the effects of honeycomb extracts on the laying performance, egg nutritional and flavor quality, serum biochemical indexes, and antioxidant and immune status in laying ducks. Methods: A total of 672 healthy 28-week-old Shanma laying ducks with similar laying performance and body weight were randomly distributed into four dietary treatments with 6 replicates of 28 birds. The birds in each treatment were fed the basal diet supplemented with 0 (control group), 0.5, 1.0 or 1.5 g/kg honeycomb extracts, respectively. Feed and water were provided ad libitum for 45 days. Laying performance, egg quality, egg nutrition and flavor quality, serum parameters were assessed. Results: The results showed that compared with the control group, honeycomb extracts addition significantly increased the average daily feed intake but did not affect the other laying performance indexes, egg quality or serum biochemical indexes of laying ducks. Dietary supplementation with honeycomb extracts significantly increased crude protein content and decreased the contents of cholesterol and trimethylamine in eggs. Diets supplemented with 1.5 g/kg honeycomb extracts significantly improved egg total amino acids and flavor amino acids contents, monounsaturated fatty acids and polyunsaturated fatty acids composition and enhanced the serum antioxidant activity and immune functions of ducks. Discussion: Duck eggs are rich in nutrients and a valuable source of high-quality food for human, while they are rarely consumed directly by consumers because of their stronger fishy odor and lower sensory quality. Many studies have showed that the influence of dietary supplementation on egg components. This study indicated that dietary supplementation with honeycomb extracts positively reduced the contents of egg cholesterol and trimethylamine, improve egg amino acids contents and fatty acid profiles, enhanced serum antioxidant and immune status of laying ducks. The recommended supplemental level of honeycomb extracts was 1.5 g/kg in the diet of laying ducks.

The roles of novel chitooligosaccharide-peanut oligopeptide carbon dots in improving the flavor quality of Chinese cabbage.

Carbon dots (CDs), a novel type of nanomaterial, play crucial roles in the agriculture field. However, it remains unclear their impacts on the flavor quality of vegetables. The present study synthesized a novel chitooligosaccharide-peanut oligopeptide-carbon dots (COS-POP-CDs) material through the chitooligosaccharide (COS) and peanut oligopeptide (POP) high temperature Maillard reactions and studied its effect on the flavor quality of Chinese cabbage (Choy sum). Results indicated that COS-POP-CDs emit blue visible light that readily absorbed by chloroplasts, while also demonstrating some degree of antibacterial and antioxidant activities. After transplanting of Choy sum, foliar spraying 0.12 mg/mL COS-POP-CDs twice can increase the content of soluble proteins, Vitamin C, and enhance the strawberry and spicy flavors of Choy Sum. After harvest of Choy Sum, foliar spraying 0.12 mg/mL COS-POP-CDs once can slow down the spoilage. These results suggest that COS-POP-CDs have significant potential to improve crop quality.