Multi-omic applications for understanding and enhancing tropical fruit flavour.

Consumer trends towards nutrient-rich foods are contributing to global increasing demand for tropical fruit. However, commercial cultivars in the breeding pipeline that are tailored to meet market demand are at risk of possessing reduced fruit flavour qualities. This stems from recurrent prioritised selection for superior agronomic traits and not fruit flavour, which may in turn reduce consumer satisfaction. There is realisation that fruit quality traits, inclusive of flavour, must be equally selected for; but currently, there are limited tools and resources available to select for fruit flavour traits, particularly in tropical fruit species. Although sugars, acids, and volatile organic compounds are known to define fruit flavour, the specific combinations of these, that result in defined consumer preferences, remain unknown for many tropical fruit species. To define and include fruit flavour preferences in selective breeding, it is vital to determine the metabolites that underpin them. Then, objective quantitative analysis may be implemented instead of solely relying on human sensory panels. This may lead to the development of selective genetic markers through integrated omics approaches that target biosynthetic pathways of flavour active compounds. In this review, we explore progress in the development of tools to be able to strategically define and select for consumer-preferred flavour profiles in the breeding of new cultivars of tropical fruit species.

Editing VvDXS1 for the creation of muscat flavour in Vitis vinifera cv. Scarlet Royal.

Muscat flavour represents a group of unique aromatic attributes in some grape varieties. Biochemically, grape berries with muscat flavour produce high levels of monoterpenes. Monoterpene biosynthesis is mainly through the DOXP/MEP pathway, and VvDXS1 encodes the first enzyme in this plastidial pathway of terpene biosynthesis in grapevine. A single-point mutation resulting in the substitution of a lysine with an asparagine at position 284 in the VvDXS1 protein has previously been identified as the major cause for producing muscat flavour in grapes. In this study, the same substitution in the VvDXS1 protein was successfully created through prime editing in the table grape Vitis vinifera cv. 'Scarlet Royal'. The targeted point mutation was detected in most of the transgenic vines, with varying editing efficiencies. No unintended mutations were detected in the edited alleles, either by PCR Sanger sequencing or by amplicon sequencing. More than a dozen edited vines were identified with an editing efficiency of more than 50%, indicating that these vines were likely derived from single cells in which one allele was edited. These vines had much higher levels of monoterpenes in their leaves than the control, similar to what was found in leaf samples between field-grown muscat and non-muscat grapes.

Flavour physics as a window to new physics searches.

Flavour physics is one of the essential elements of the Standard Model (SM). Experimental studies of weak decays of [Formula: see text] and [Formula: see text] mesons at [Formula: see text] factories have, together with the discovery of the Higgs boson at LHC, provided the final confirmation of the validity of the SM. The present generation of precision flavour physics experiments is looking for departures from the SM. We discuss studies of anomalies in [Formula: see text] hadron decays, and studies of rare decays, which are a very promising method for searching for new physics. This article is part of the theme issue 'The particle-gravity frontier'.

Pyruvate stimulates transamination of leucine into α-ketoisocaproic acid and supports 3-methylbutanal production by Lactococcus lactis.

AIM: To investigate the effect of pyruvate and glucose on leucine transamination and 3-methylbutanal production by Lactococcus lactis, including the comparison with cells possessing glutamate dehydrogenase (GDH) activity. METHODS AND RESULTS: L. lactis cells were incubated in chemically defined medium (CDM) with the pH controlled at 5.2 to mimic cheese conditions. Pyruvate supplementation stimulated the production of the key flavour compound 3-methylbutanal by 3 to 4 times after 72 hours of incubation. Concurrently, alanine production increased, demonstrating the involvement of pyruvate in transamination reactions. Glucose-metabolising cells excreted α-ketoisocaproic acid and produced even 3 times more 3-methylbutanal after 24 hours than pyruvate-supplemented cells. Conjugal transfer technique was used to transfer the plasmid pGdh442 carrying the gdh gene encoding for GDH to L. lactis. Introducing GDH did not stimulate the excretion of α-ketoisocaproic acid and the production of 3-methylbutanal. CONCLUSIONS: These results demonstrate that Lactococcus uses pyruvate to transaminate leucine into α-ketoisocaproic acid which supports 3-methylbutanal production. Surprisingly, GDH activity did not stimulate leucine transamination and 3-methylbutanal production.

Developing defined starter culture for reproducible profile of flavour compound in Chinese xiaoqu baijiu fermentation.

Defined starter cultures, containing selected microbes could reduce the complexity of natural starter, are beneficial for controllable food fermentations. However, there are challenges in identifying key microbiota and constructing synthetic microbiota for traditional food fermentations. Here, we aimed to develop a defined starter culture for reproducible profile of flavour compounds, using Chinese Xiaoqu Baijiu fermentation as a case. We classified all microbes into 4 modules using weighted correlation network analysis. Module 3 presented significant correlations with flavour compounds (P < 0.05) and the highest gene abundance related with flavour compound production. 13 dominant species in module 3 were selected for mixed culture fermentation, and each species was individually deleted to analyse the effect on flavour compound production. Ten species, presenting significant effects (P < 0.05) on flavour compound production, were selected for developing the starter culture, including Rhizopus oryzae, Rhizopus microsporus, Saccharomyces cerevisiae, Pichia kudriavzevii, Wickerhamomyces anomalus, Lactobacillus acetotolerans, Levilactobacillus brevis, Weissella paramesenteroides, Pediococcus acidilactici, and Leuconostoc pseudomesenteroides. After optimising the structure of the starter culture, the profile similarity of flavour compounds produced by the starter culture reached 81.88% with that by the natural starter. This work indicated feasibility of reproducible profile of flavour compounds with defined starter culture for food fermentations.

Exploring the opinions and potential impact of unflavoured e-liquid on smoking cessation among people who smoke and smoking relapse among people who previously smoked and now use e-cigarettes: findings from a UK-based mixed methods study.

BACKGROUND: Although electronic cigarettes (e-cigarettes) appear to be effective in helping people who smoke to stop smoking, concerns about use of e-cigarettes among young people have led to restrictions on non-tobacco flavoured e-liquids in some countries and some US states. These restrictions could reduce the appeal of these products to non-smoking youth but could have negative consequences for people who smoke or use e-cigarettes. METHODS: In this mixed methods study, we recruited UK adults who smoked or used to smoke and subsequently vaped to explore their opinions of unflavoured e-liquids and their beliefs about how they would be impacted by hypothetical e-liquid flavour restrictions. Participants trialled an unflavoured e-liquid instead of their usual nicotine product for four hours and completed a survey and an online interview. RESULTS: Using Interpretive Phenomenological Analysis and graphically presented data, we found differences in participants' opinions of unflavoured e-liquid. If only unflavoured, tobacco flavoured, and menthol flavoured e-liquids remained on the UK market, some people who smoke or vape may be unaffected, but some may relapse to smoking or continue smoking. Despite most wanting to prevent young people from initiating vaping, participants had varying opinions on whether flavour restrictions would be an effective method. CONCLUSIONS: The findings highlight that people who smoke and vape could be impacted by flavour restrictions in a range of ways, some of which could have a potential adverse impact on harm reduction efforts in the UK (e.g., by making smoking more appealing than vaping).

Characterisation of Pea Milk Analogues Using Different Production Techniques.

Research background: Among legumes, peas are characterised by their high protein content, low glycaemic index and exceptional versatility. However, their potential as a food is often compromised by their undesirable off-flavour and taste. Hence, this study focuses on minimising off-flavours through simple pretreatments with the aim of improving the potential for the production of pea milk analogues. Pea milk analogues are a burgeoning type of plant-based milk alternatives in the growing plant-based market. Experimental approach: Pea seeds were subjected to different pretreatments: (i) dry milling, (ii) blanching followed by soaking in alkaline solution and subsequent dehulling and (iii) vacuum. Typical physicochemical properties such as pH, viscosity, colour, titratable acidity and yield were measured to obtain a brief overview of the products. Consumer acceptance test, descriptive sensory analysis, gas chromatography-mass spectrometry and gas chromatography-olfactometry were used to map the complete sensory profile and appeal of the pea milk substitutes. Results and conclusions: The L* values of the pea milk analogues were significantly lower than those of cow's milk, while a*, b*, viscosity and pH were similar. In the descriptive sensory analysis, sweet, astringent, pea-like, cooked, hay-like, boiled corn and green notes received relatively higher scores. The vacuum-treated pea milk analogues received higher scores for flavour and overall acceptability in the consumer acceptance test. The pretreatments resulted in significant changes in the volatile profiles of the pea milk analogues. Some volatiles typically associated with off-flavour, such as hexanal, were found in higher concentrations in blanched pea milk analogues. Among the applied pretreatments, vacuum proved to be the most effective method to reduce the content of volatile off-flavour compounds. Novelty and scientific contribution: This study stands out as a rare investigation to characterise pea milk analogues and to evaluate the impact of simple pretreatments on the improvement of their sensory properties. The results of this study could contribute to the development of milk alternatives that offer both high nutritional value and strong appeal to consumers.

Integrating new variables into a framework to support cacao denomination of origin: a case study in Southwest Colombia.

BACKGROUND: Cocoa quality plays a pivotal role in establishing denominations of origin, with genotypes, geography, climate and soil conditions being key variables. However, these factors have not been comprehensively explored in defining cacao denominations of origin. The present study addresses this gap by laying the foundation for cacao denomination of origin, focusing on the Buenaventura region on Colombia's Pacific coast. Our goal is to provide a holistic understanding of the elements underpinning cacao denomination of origin, emphasizing Buenaventura's unique cocoa quality and geographical significance. RESULTS: Through the Buenaventura case, we propose a robust framework applicable to other cacao-producing regions, elevating the recognition and value of cacao denomination of origin. Our framework encompasses geography, agronomy, genetics, microbial diversity, pests and diseases and cocoa quality. In a pioneering move, we propose a cacao denomination of origin in Colombia, specifically examining Bajo Calima, Sabaletas and Cisneros within Buenaventura region. Buenaventura stands out for its cocoa quality, characterized by fruity flavors attributed to the rich biodiversity of the lowland rainforest. CONCLUSION: Our analysis indicates specific geographical indicators for each of the study zones, with Buenaventura identified as a region with natural characteristics to produce fine flavour cocoa products. Each zone exhibited a high differentiation and diversity of cacao cultivars. Buenaventura has the potential to be designated as a future denomination of origin for cacao from the Pacific region of Colombia, characterized by its unique fruity-aroma chocolates. Our framework is adaptable to other cacao-producing regions, facilitating the establishment of denominations of origin within the cocoa industry and agriculture. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Identification of antioxidant and flavour marker compounds in Kalosi-Enrekang Arabica brewed coffee processed using different postharvest treatment methods.

This research aims to predict the presence of marker compounds that differentiate tubruk brew from coffee beans with different postharvest processing. This research also aims to predict compounds correlating with antioxidant activity and sensory flavour attributes. This research used Kalosi-Enrekang Arabica coffee beans, which were processed with three different postharvest processing (honey, full-washed and natural), roasted at medium level, and brewed using the tubruk method. Each brew was analyzed for chemical profiles using LC-MS and GC-MS, antioxidant analysis using the DPPH IC50 and FRAP methods, and sensory analysis for flavour using the QDA and SCAA methods for cupping scores. OPLS-DA analysis revealed the presence of marker compounds from each brew, and the dried fruit flavour attribute was to be an inter-process marker. After that, OPLS analysis showed marker compounds that correlate to antioxidant activity and flavour attributes. Rhaponticin is thought to be one of the marker compounds in natural coffee brews and is one of the compounds that correlates to the antioxidant activity of the DPPH method (IC50); prunin is thought to be one of the marker compounds for full-washed coffee brews and is one of the compounds that correlates to the activity antioxidants of FRAP method. Triacetin, which is thought to be a marker compound in natural brewed coffee, correlates with fruity flavour. 3-acetylpyridine, as a marker in honey-brewed coffee, correlates with nutty flavour. Even though there are differences in dominant flavours, the cupping score shows the brew is categorized as a specialty. This research shows that different post-harvest processing processes influence the compound profile, antioxidant activity and flavour attributes of Tubruk brewed coffee. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-024-05948-8.

Multisensory integration of orally-sourced gustatory and olfactory inputs to the posterior piriform cortex in awake rats.

Flavour refers to the sensory experience of food, which is a combination of sensory inputs sourced from multiple modalities during consumption, including taste and odour. Previous work has demonstrated that orally-sourced taste and odour cues interact to determine perceptual judgements of flavour stimuli, although the underlying cellular- and circuit-level neural mechanisms remain unknown. We recently identified a region of the piriform olfactory cortex in rats that responds to both taste and odour stimuli. Here, we investigated how converging taste and odour inputs to this area interact to affect single neuron responsiveness ensemble coding of flavour identity. To accomplish this, we recorded spiking activity from ensembles of single neurons in the posterior piriform cortex (pPC) in awake, tasting rats while delivering taste solutions, odour solutions and taste + odour mixtures directly into the oral cavity. Our results show that taste and odour inputs evoke highly selective, temporally-overlapping responses in multisensory pPC neurons. Comparing responses to mixtures and their unisensory components revealed that taste and odour inputs interact in a non-linear manner to produce unique response patterns. Taste input enhances trial-by-trial decoding of odour identity from small ensembles of simultaneously recorded neurons. Together, these results demonstrate that taste and odour inputs to pPC interact in complex, non-linear ways to form amodal flavour representations that enhance identity coding. KEY POINTS: Experience of food involves taste and smell, although how information from these different senses is combined by the brain to create our sense of flavour remains unknown. We recorded from small groups of neurons in the olfactory cortex of awake rats while they consumed taste solutions, odour solutions and taste + odour mixtures. Taste and smell solutions evoke highly selective responses. When presented in a mixture, taste and smell inputs interacted to alter responses, resulting in activation of unique sets of neurons that could not be predicted by the component responses. Synergistic interactions increase discriminability of odour representations. The olfactory cortex uses taste and smell to create new information representing multisensory flavour identity.

Biology and physiology of Hanseniaspora vineae: metabolic diversity and increase flavour complexity for food fermentation.

Apiculate yeasts belonging to the genus Hanseniaspora are predominant on grapes and other fruits. While some species, such as Hanseniaspora uvarum, are well known for their abundant presence in fruits, they are generally characterized by their detrimental effect on fermentation quality because the excessive production of acetic acid. However, the species Hanseniaspora vineae is adapted to fermentation and currently is considered as an enhancer of positive flavour and sensory complexity in foods. Since 2002, we have been isolating strains from this species and conducting winemaking processes with them. In parallel, we also characterized this species from genes to metabolites. In 2013, we sequenced the genomes of two H. vineae strains, being these the first apiculate yeast genomes determined. In the last 10 years, it has become possible to understand its biology, discovering very peculiar features compared to the conventional Saccharomyces yeasts, such as a natural and unique G2 cell cycle arrest or the elucidation of the mandelate pathway for benzenoids synthesis. All these characteristics contribute to phenotypes with proved interest from the biotechnological point of view for winemaking and the production of other foods.

Flavour by design: food-grade lactic acid bacteria improve the volatile aroma spectrum of oat milk, sunflower seed milk, pea milk, and faba milk towards improved flavour and sensory perception.

BACKGROUND: The global market of plant-based milk alternatives is continually growing. Flavour and taste have a key impact on consumers' selection of plant-based beverages. Unfortunately, natural plant milks have only limited acceptance. Their typically bean-like and grassy notes are perceived as "off-flavours" by consumers, while preferred fruity, buttery, and cheesy notes are missing. In this regard, fermentation of plant milk by lactic acid bacteria (LAB) appears to be an appealing option to improve aroma and taste. RESULTS: In this work, we systematically studied LAB fermentation of plant milk. For this purpose, we evaluated 15 food-approved LAB strains to ferment 4 different plant milks: oat milk (representing cereal-based milk), sunflower seed milk (representing seed-based milk), and pea and faba milk (representing legume-based milk). Using GC‒MS analysis, flavour changes during anaerobic fermentations were studied in detail. These revealed species-related and plant milk-related differences and highlighted several well-performing strains delivered a range of beneficial flavour changes. A developed data model estimated the impact of individual flavour compounds using sensory scores and predicted the overall flavour note of fermented and nonfermented samples. Selected sensory perception tests validated the model and allowed us to bridge compositional changes in the flavour profile with consumer response. CONCLUSION: Specific strain-milk combinations provided quite different flavour notes. This opens further developments towards plant-based products with improved flavour, including cheesy and buttery notes, as well as other innovative products in the future. S. thermophilus emerged as a well-performing strain that delivered preferred buttery notes in all tested plant milks. The GC‒MS-based data model was found to be helpful in predicting sensory perception, and its further refinement and application promise enhanced potential to upgrade fermentation approaches to flavour-by-design strategies.

An in-depth multiphasic analysis of the chocolate production chain, from bean to bar, demonstrates the superiority of Saccharomyces cerevisiae over Hanseniaspora opuntiae as functional starter culture during cocoa fermentation.

Hanseniaspora opuntiae is a commonly found yeast species in naturally fermenting cocoa pulp-bean mass, which needed in-depth investigation. The present study aimed at examining effects of the cocoa isolate H. opuntiae IMDO 040108 as part of three different starter culture mixtures compared with spontaneous fermentation, regarding microbial community, substrate consumption, and metabolite production dynamics, including volatile organic compound (VOC) and phytochemical compositions, as well as compositions of the cocoa beans after fermentation, cocoa liquors, and chocolates. The inoculated H. opuntiae strain was unable to prevail over background yeasts present in the fermenting cocoa pulp-bean mass. It led to under-fermented cocoa beans after four days of fermentation, which was however reflected in higher levels of polyphenols. Cocoa fermentation processes inoculated with a Saccharomyces cerevisiae strain enhanced flavour production during the fermentation and drying steps, which was reflected in richer and more reproducible aroma profiles of the cocoa liquors and chocolates. Sensory analysis of the cocoa liquors and chocolates further demonstrated that S. cerevisiae led to more acidic notes compared to spontaneous fermentation, as a result of an advanced fermentation degree. Finally, different VOC profiles were found in the cocoa beans throughout the whole chocolate production chain, depending on the fermentation process.

Rare short- and medium-chain fatty acid-producing anaerobes from raw soil play vital roles in formation of diverse flavour compounds of Jiangxiangxing Baijiu.

Pit mud is an essential habitat for diverse anaerobes, however, how pit mud of Jiangxiangxing Baijiu contributes to flavour is still unclear. The correlation between pit mud anaerobes and flavour compounds formation was investigated by analyzing flavour compounds and prokaryotic community of pit mud as well as fermented grains. Then scaling-down fermentation and culture-dependent approach were used to verify the effects of pit mud anaerobes on flavour compound formation. We found that short- and medium-chain fatty acids and alcohols, e.g., propionate, butyrate, caproate, 1-butanol, 1-hexanol, and 1-heptanol, were the vital flavour compounds produced by pit mud anaerobes. Pit mud anaerobes hardly migrated into fermented grains because of the low pH and low moisture of fermented grains. Therefore, the flavour compounds produced by pit mud anaerobes might enter fermented grains via volatilization. Moreover, enrichment culturing proved that raw soil was one of the sources for pit mud anaerobes, e.g., Clostridiumtyrobutyricum, Ruminococcaceae bacterium BL-4 and Caproicibacteriumamylolyticum. These rare short- and medium-chain fatty acid-producing anaerobes in raw soil can be enriched during Jiangxiangxing Baijiu fermentation. These findings clarified the role of pit mud during Jiangxiangxing Baijiu fermentation and revealed the key species involved in short- and medium-chain fatty acid-producing production.

Volatile flavour identification and odour complexity of radix Angelicae sinensis by electronic nose, integrated gas chromatography-mass spectrometry/olfactometry and comprehensive two-dimensional gas chromatography-time-of-flight-mass spectrometry.

INTRODUCTION: Radix Angelicae sinensis (Danggui, DG) is known as one of the typical traditional Chinese medicines. DG material consists of a variety of volatile substances, polysaccharides, organic acids, ceramides, amino acids, vitamins, microelements, among others, and thus has been used for medicinal and edible purposes in a long history. The fragrance is of importance to assessing the DG material quality. OBJECTIVES: This study was to determine volatile flavour compositions of DG materials and to reveal the odour complexity. MATERIAL AND METHODS: Electronic nose (E-nose), integrated gas chromatography-mass spectrometry/olfactometry (GC-MS/O) and comprehensive two-dimensional gas chromatography-time-of-flight-mass spectrometry (GC × GC-TOF-MS), combined with solid-phase micro-extraction (SPME), were mainly used to address the flavour complexity of DG materials. RESULTS: Using the E-nose sensor responses, a total of 105 batches of DG samples cultivated in six provinces of China were categorised according to their odour differentiations, and a principal component analysis (PCA) model was established for evaluating the sample quality through a combination of Hotelling's T2 and Q-residual values in a statistical quantitative sense. By the GC-MS/O and GC × GC-TOF-MS analyses, 196 volatile flavour compounds were identified, 51 odour-active areas discerned and 39 odourants determined. It was terpenes and aromatics of the flavour compounds that mainly contributed to the odour attributes of DG herb. CONCLUSION: The SPME-GC × GC-TOF-MS method was the first time employed to analyse the volatile flavours of DG materials, and thus made a breakthrough in determining 196 flavour compounds, much more than those in any previous report. The work also made a significant step forward to link the flavour compositions and odour complexity of radix Angelicae sinensis by E-nose and GC-MS/O techniques. It not only provided a statistical PCA model that did not depend on any predetermined compositions or sensory properties for, but also a comprehensive insight into the quality evaluation of DG materials.

Impact of Fermentation Conditions on Physicochemical Properties, Antioxidant Activity, and Sensory Properties of Apple-Tomato Pulp.

The aim of the study was to optimize the conditions [inoculum size (4, 6, and 8%), fermentation temperature (31, 34, and 37 °C), and apple: tomato ratio (2:1, 1:1, and 1:2)] on the viable cell count and sensory evaluation in apple-tomato pulp by response surface methodology (RSM), and determine the physicochemical properties, antioxidant activity, and sensory properties during fermentation. The optimal treatment parameters obtained were an inoculum size of 6.5%, a temperature of 34.5 °C, and an apple: tomato ratio of 1:1. After fermentation, the viable cell count reached 9.02 lg(CFU/mL), and the sensory evaluation score was 32.50. During the fermentation period, the pH value, total sugar, and reducing sugar decreased by 16.67%, 17.15%, and 36.05%, respectively. However, the total titratable acid (TTA), viable cell count, total phenol content (TPC), and total flavone content (TFC) increased significantly by 13.64%, 9.04%, 21.28%, and 22.22%, respectively. The antioxidant activity [2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging ability, 2,2'-azino-di(2-ethyl-benzthiazoline-sulfonic acid-6) ammonium salt (ABTS) free-radical scavenging ability, and ferric-reducing antioxidant capacity power (FRAP)] also increased by 40.91%, 22.60%, and 3.65%, respectively, during fermentation. A total of 55 volatile flavour compounds were detected using HS-SPME-GC-MS among the uninoculated samples and fermented samples before and after fermentation. The results showed that fermentation increased the types and total amount of volatile components in apple-tomato pulp, and eight new alcohols and seven new esters were formed. Alcohols, esters, and acids were the main volatile components in apple-tomato pulp, accounting for 57.39%, 10.27%, and 7.40% of the total volatile substances, respectively.

Influence of Different Ratios of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus on Fermentation Characteristics of Yogurt.

Lactic acid bacteria (LAB) are industrially important bacteria that are widely used in the fermented food industry, especially in the manufacture of yogurt. The fermentation characteristics of LAB are an important factor affecting the physicochemical properties of yogurts. Here, different ratios of L. delbrueckii subsp. bulgaricus IMAU20312 and S. thermophilus IMAU80809 were compared with a commercial starter JD (control) for their effects on viable cell counts, pH values, titratable acidity (TA), viscosity and water holding capacity (WHC) of milk during fermentation. Sensory evaluation and flavour profiles were also determined at the end of fermentation. All samples had a viable cell count above 5.59 × 107 CFU/mL at the end of fermentation, and a significant increase in TA and decrease in pH were observed. Viscosity, WHC and the sensory evaluation results of one treatment ratio (A3) were closer to the commercial starter control than the others. A total of 63 volatile flavour compounds and 10 odour-active (OAVs) compounds were detected in all treatment ratios and the control according to the results from solid-phase micro-extraction-gas chromatography-mass spectrometry (SPME-GC-MS). Principal components analysis (PCA) also indicated that the flavour characteristics of the A3 treatment ratio were closer to the control. These results help us understand how the fermentation characteristics of yogurts are affected by the ratio of L. delbrueckii subsp. bulgaricus to S. thermophilus in starter cultures; this is useful for the development of value-added fermented dairy products.

Isoflavones Play a Potential Role in Off-Flavour Scavenging, with a Key Role of IFS2 in Isoflavone Accumulation in Soybean Seeds.

Research background: Soybean (Glycine max (L.) Merr) is a nutrient-rich crop with a high protein content and various bioactive compounds with health-promoting properties. Nevertheless, it is poorly accepted as a food by consumers due to its off-flavour. Due to the ubiquitous presence of isoflavones in soybeans, their inherent antioxidant potential and inhibitory effect on lipoxygenase activity, their sensory properties are currently being considered to mitigate the off-flavour. Experimental approach: In the present study, the content and composition of isoflavones in 17 soybean cultivars are determined. The correlation between the isoflavone mass fraction and lipid peroxidation was also established, using thiobarbituric acid (TBA) value and carbonyl compound concentration as indices for the development of off-flavour. Cloning, gene expression analysis and in silico analysis of isoflavone synthase isoforms (IFS1 and IFS2) were also performed. Results and conclusions: The total isoflavone mass fraction in soybean genotypes ranged from (153.5±7.2) µg/g for PUSA 40 to (1146±43) µg/g for Bragg. There was a moderately negative correlation between the indices of off-flavour formation and the genistein/daidzein ratio (p<0.1). However, the correlation with total isoflavone mass fraction was found to be insignificant, indicating complex interactions. Higher protein-protein interactions for the predicted structure of IFS2 with other biosynthesis enzymes and its comparatively higher expression in the Bragg than that of IFS1 indicated its more important role in isoflavone synthesis. Novelty and scientific contribution: The genistein/daidzein mass ratio was found to be an important factor in controlling off-flavour. IFS2 was identified as key to produce soybeans with high isoflavone mass fraction and potentially lower off-flavour formation.

Evaluation of dietary metabolizable energy concentrations on meat quality and lipid metabolism-related gene expression in yellow-feathered chickens.

This study evaluated the effects of different dietary metabolizable energy (ME) concentrations on the meat quality, carcass traits, volatile flavour and lipid metabolism-related gene expression levels in yellow-feathered chickens. In total, 600 Huxu female chickens aged 90 days were randomly assigned to six dietary treatments, each with 10 replicates of 10 birds. During the finisher phase, the birds were fed diets containing 2880 (low), 2940, 3000, 3060, 3120 and 3180 (high) kcal ME/kg. The results showed that the average daily gain of chickens increased as the dietary ME concentration increased, while the feed to gain improved (p < 0.05), and the intramuscular fat content of breast muscle increased (p < 0.05). The energy concentration had no effect on the breast muscle pH (45 min and 24 h), colour parameter (L*) or percentage of drip loss (p > 0.05), but the shear force values decreased significantly (p < 0.05). The diameter and area of the breast muscle fiber decreased and the muscle fibre density increased as the dietary ME concentration increased (p < 0.05). The highest ME concentration (3180 kcal) increased the percentages of aldehydes (hexanal, heptanal, 2,4-nonadienal, octanal, nonanal and 2-decenal), alcohols (2-nonen-1-ol, trans-2-undecen-1-ol, 7-hexadecenal, 2-hexyl-1-decanoal and n-nonadecanol-1,3,7,11-trimethyl-1-dodecanol), alkanes (2,6-dimethyl-heptadecane) and carboxylic acids (9-hexadecenoic acid), but reduced the percentages of octadecanal, octadecane, heneicosane and tetradecanal (p < 0.05). In addition, the mRNA gene expression levels of fatty acid-binding protein 3 and apolipoprotein B were significantly upregulated in the liver, whereas that of cholesteryl ester transfer protein was significantly downregulated. In conclusion, increasing the ME diet to 3180 kcal/kg significantly improved the quality and flavour of the meat from yellow-feathered broilers. our finding may help poultry producers to improve the taste of meat by regulating genes related to lipid metabolism, thereby achieving the flavour and taste characteristics preferred by consumers.

Complete dominant inheritance of intracellular leucine accumulation traits in polyploid yeasts.

The yeast Saccharomyces cerevisiae is widely used for ethanol production. In the production of alcoholic beverages, flavours are affected mainly by yeast metabolism in the fermentation process. To increase the contents of initial scented fruity flavours, such as isoamyl alcohol and isoamyl acetate, leucine accumulation in yeast cells is induced by a decrease of leucine feedback inhibition in the l-leucine synthetic pathway using conventional mutagenesis. Diploid strains are commonly used in sake brewing because of better fermentation performance, such as vitality and endurance, compared with those of haploid strains. Heterozygous mutations are mostly detected in target genes of brewing yeasts generated through mutation breeding. Here we describe that an allele of the LEU4 gene, LEU4G516S , dominantly induced leucine accumulation even in triploid and tetraploid yeasts as with in diploid yeasts. Importantly, we demonstrated that there is no difference in the intracellular amount of branched-chain amino acids between LEU4G516S /LEU4 heterozygous diploids and LEU4G516S /LEU4G516S homozygous diploids. The approach to increase isoamyl alcohol and isoamyl acetate by intracellular leucine accumulation can potentially be applied to a variety of yeast strains, including aneuploid and polyploid yeasts.