Fruity Aroma Research Articles

Isolation and identification of non‐Saccharomyces yeasts and their flavour characteristics while brewing Yinhong plum wine

AbstractThe objective of this study was to screen non‐Saccharomyces yeast suitable for enhancing the aroma of Yinhong plum wine. Five non‐Saccharomyces yeasts with strong ester‐producing ability, namely, Wa3 (Wickerhamomyces anomalus), Hu12 (Hanseniaspora uvarum), Pk2A2, PkW2 and PkY2 (Pichia kluyveri), were selected from various naturally fermented fruit juices for molecular biological identification, analyses of physiological characteristics and tolerance and determination of their effects on the flavour of Yinhong plum wine. Analysis of brewing characteristics showed that they differed in their abilities of producing acetic acid, hydrogen sulfide, killer activity and tolerance. Among them, Wa3 showed the best tolerance to high concentrations of alcohol, sugar and SO2. Compared to the control Saccharomyces cerevisiae FX10, Yinhong plum wine fermented with non‐Saccharomyces yeast exhibited a decrease in alcohol content, while residual sugar, glycerol content and the types and quantities of volatile compounds all showed an increase. Among the fermented wines, PkY2 generated the highest content of ester compounds in the fermented wine, which was 5.66 times higher than that generated by the control. The compounds produced by PkY2 were closely related to various ethyl and acetate odour‐active compounds (odour‐active value >1), which could impart a rich floral and fruity aroma to Yinhong plum wine. Sensory analysis revealed that both floral and fruity aromas were significantly increased in Yinhong plum wine fermented by non‐Saccharomyces yeasts, with the highest scores of floral and fruity aromas for PkY2. In conclusion, a Pichia kluyveri strain, PkY2, with excellent brewing characteristics and potential for enhancing the aroma of Yinhong plum wine was identified.

Sensory-directed approach to explore cider typicity: the case of ciders from the Canary Islands (Spain)

PurposeThe main aim of this study is to characterise and identify specific chemo-sensory profiles of ciders from the Canary Islands (Spain).Design/methodology/approachCommercial samples of Canary ciders were compared to ciders from the Basque Country and Asturias. In total, 18 samples were studied, six for each region. The analysis comprised their sensory profiling and chemical characterisation of their polyphenolic profile, volatile composition, conventional chemical parameters and CIELAB colour coordinates. In parallel, the sensory profile of the samples from the Canary Islands was first compared with their Basque and Asturian counterparts by labelled sorting task. Then, their specific aroma profile was characterised by flash profile. Further quantification of sensory-active compounds was performed by GC–MS and GC-FID to identify the volatile compounds involved in their aroma profile.FindingsResults show that Canary ciders present a specific chemical profile characterised by higher levels of ethanol, and hydroxycinnamic acids, mainly t-ferulic, t-coumaric and neochologenic acids, and lower levels of volatile and total acidity than their Asturian and Basque counterparts. They also present a specific aroma profile characterised by fruity aroma, mainly fruit in syrup and confectionary, and sweet flavours related to their highest levels of vinylphenols formed by transformation of hydroxycinnamic acids.Originality/valueAn integrated strategy to explore the typicity of the currently existing Canary ciders in the market was developed. The results are important in that they will help other regions to identify specific typical chemo-sensory profiles and to promote the creation of certifications supporting regional typicity.

Amino acid preference and fermentation performance of Pichia kluyveri strains in a synthetic wort

Pichia kluyveri is a maltose-negative yeast applied for non- and low-alcoholic beer (NABLAB) production due to its fruity aroma attributes, however, related literature is still limited. Thus, this study aims to investigate basic fermentation parameters, such as growth, sugar consumption, and production of primary fermentation metabolites, but also the amino acid preference of three different P. kluyveri strains in an agitated model brewers’ wort substrate. Furthermore, the effect of agitation on these parameters was studied for one of the strains. The three strains assessed, PKCH_01, PKCH_02 and PKCH_03, shared a glucophilic nature, a cell growth from 4E+07 to 6E+07 E+07 CFU/mL, similar amino acid preference, and equivalent ethanol yield factor (Yse) from 0.45 to 0.5 g ethanol/g glucose. In addition, agitation increased the cell growth yield factor by 78% and favored the uptake of amino acids, minimizing their release to the medium. Interestingly, a strong preference for methionine (above 80% consumption) by P. kluyveri in a beer-related medium was reported for the first time, whereas glutamine and glutamate were within the low-preference group (below 15% consumption). This study provides a better understanding about fermentation and physiological attributes of P. kluyveri, thereby revealing its potential for brewing applications.

Juice drinks based on vegetable raw materials

Numerous scientific studies have repeatedly proved the importance of consumption of fresh vegetables and fruits for human health. Natural juices from vegetables and fruits are a concentrated form of vitamins, minerals and antioxidants. Vegetable juices help absorb nutrients at a high rate. When consuming vegetables in the form of juice, β-carotene is absorbed faster, which contributes to the normal formation of the skin and strengthening of the mucous membranes. The purpose of the research is to develop a technology for the production of juice drinks based on vegetable raw materials with a balanced content of nutrients and low calorie content. The article presents data on the development of the technology of juice drinks based on fruit and vegetable raw materials using apple juice, pumpkin and carrot puree. The choice of blending components for creating biologically valuable drinks is substantiated: the basis is pumpkin puree; auxiliary – unclarified apple juice; biologically valuable additive – carrot puree. It has been experimentally investigated that the prescribed amount of apple juice in a blend with pumpkin and carrot should be at least 2.5 parts of the blend. The optimal content of carrot puree in a pumpkin-apple drink has been determined – no more than 10 %. The drink had a pleasant sweet pumpkin taste, a fruity aroma with a hint of orange apple and evenly distributed pulp. Various options for recipe ratios of food components for creating a pumpkin-apple-carrot drink with pulp according to organoleptic evaluation were studied. A technological scheme for the production of pumpkin-based juice with the addition of apple juice and carrot puree has been developed. Organoleptic evaluation and sensory analysis of experimental drinks were carried out. It was found that the ratio of components in mixed drinks against the background of the main one significantly affects the organoleptic indicators of the finished product.

Analysis of tea quality of large-leaf black tea with different harvesting tenderness based on metabolomics

The harvesting tenderness of tea fresh leaves has a significant effect on the flavor and aroma quality of black tea (BT), which is one of the important standards for BT grading. In this study, sensory evaluation, electronic tongue technique and metabolomics were performed to evaluate the flavor and aroma qualities of three different tenderness of large-leaf BTs that were manufactured from the fresh leaves of single-bud, one-bud and one-bud two-leaf teas, respectively. The results of the electronic tongue and sensory evaluation indicated that the increase in the tenderness of the fresh leaf material enhanced the sweetness, freshness and fruity flavor of the tea and reduced the bitterness of the tea. A total of 519 differential flavor components and 84 differential aroma components were identified by metabolomics. Among them, elevated levels of maltitol, cyclic leucine and l-methionine and l-aspartic acid led to elevated sweetness and freshness in more tender tea leaves. Reduced levels of 4-aminosalicylic acid, tyrosol, uracil, inosine, benzamide, and l-tyrosine led to reduced bitterness in BT. Moreover, the content of volatiles such as (Z)-2-Decenal, Phenylacetic acid propyl ester, Acetophenone, and 2-phenylethyl ester were increased, which contributed to the fruity aroma in the high-tenderness tea. This study provides a theoretical basis for grading the flavor quality of BT with different tenderness.

Evaluation of stress tolerance and design of alternative culture media for the production of fermentation starter cultures in cacao

Ecuador is one of the world's leading producers of cacao beans, and Nacional x Trinitario cacao represents one of the most distinctive varieties due to its flavor and aroma characteristics. This study aimed to evaluate the effect of the starter culture isolated from microbial diversity during the spontaneous fermentation of Nacional x Trinitario cacao. A total of 249 microbial isolates were obtained from spontaneous culture, with Lactiplantibacillus (45 %), Saccharomyces (17 %), and Acetobacter (2 %) being the most relevant genera for fermentation. Tolerance tests were conducted to select microorganisms for the starter culture. Lactiplantibacillus plantarum exhibited the highest tolerance at pH 5 and 6 % ethanol and tolerated concentrations up to 15 % for glucose and fructose. Acetobacter pasteurianus grew at pH 2 and 6 % ethanol, tolerating high sugar concentrations of up to 15 % for glucose and 30 % for fructose, with growth observed in concentrations up to 5 % for lactic and acetic acid. Subsequently, a laboratory-scale fermentation was conducted with the formulated starter culture (SC) comprising S. cerevisiae, L. plantarum, and A. pasteurianus, which exhibited high tolerance to various stress conditions. The fermentation increased alcoholic compounds, including citrusy, fruity aromas, and floral notes such as 2-heptanol and phenylethyl alcohol, respectively 1.6-fold and 5.6-fold compared to the control. Moreover, the abundance of ketones 2-heptanone and 2-nonanone increased significantly, providing sweet green herbs and fruity woody aromas. Cacao fermented with this SC significantly enhanced the favorable aroma-producing metabolites characteristic of Fine-aroma cacao. These findings underscore the potential of tailored fermentation strategies to improve cacao product quality and sensory attributes, emphasizing the importance of ongoing research in optimizing fermentation processes for the cacao industry.

Factors affecting consumers’ acceptability of fiber drink products

The objective of this study was to evaluate factors that impact consumers’ acceptability of fiber drink products. The influence of both the sensory and non-sensory factors on the liking of fiber drink was investigated using 121 consumers (mean age 20.3 ± 3.2-year-old). Six commercial fiber drink samples were investigated in this study with different flavor and characteristics. The CATA (Check-All-That-Apply) method was implemented for descriptive measurement of the fiber drink samples and consumer acceptance was measured using 9-point hedonic scale. The result showed that both sensory and non-sensory characteristics were able to impact liking of fiber drink samples. The sensorial characteristics of bright color (p< 0.001), sweet aroma (p< 0.001), fruity aroma (p< 0.001), berry aroma (p=0.043), sweet taste (p< 0.001), and fruity taste (p< 0.001), were shown to significantly impact liking. In contrast, attributes of darker (p< 0.001) and green (p< 0.001) color, texture of sandy (p=0.002), clumpy (p< 0.001), puree (p=0.009) and gel-like (p< 0.001) were significantly decreasing liking. For the non-sensory attributes, factors associated with health and wellness have significantly impact liking with artificial (p=0.018) and nauseated (p<0.001) showed to negatively impact liking. This is the baseline study to understand factors impacting the acceptability of consumers in fiber drink samples and can be used to develop fiber drink products with the most acceptable profiles based on consumers’ evaluations.

Aroma formation mechanism by the drying step during Congou black tea processing: Analyses by HP-SPME and SAFE with GC-MS

Drying plays a key role in the formation of the final aroma of black tea. However, the contribution to its aroma remains unclear. Herein, headspace solid-phase microextraction (HP-SPME) and solvent-assisted flavor evaporation (SAFE) coupled with GC-MS were used to detect the volatiles of tea samples (before or after drying) from three cultivars. We found that the drying step caused increase in sweet and fruity aromas and decrease in mint-like and green aromas. 89 Differential volatiles were identified with variable importance in projection (VIP) over 1. Furthermore, 25 decreased aroma-active volatiles were obtained with relative odor activity values (rOAVs) over 1, showing that green, flowery, fruity, sweet, and mint-like decreased significantly by 62.27%, 64.88%, 67.56%, 58.26%, and 69.72% after drying step. (Z)-3-Hexen-1-ol (rOAV = 36.93), linalool (rOAV = 301.56) and methyl salicylate (rOAV = 5.50) were the odorants for the green, flowery, fruity, and mint-like odor. Moreover, other 3 increased aroma-active volatiles showed that flowery, fruity, and sweet volatiles increased significantly after drying step. β-Damascenone (rOAV = 43.49) was the main odorant for fruity and sweet aroma. The 28 differential volatiles were associated with carotenoid degradation, lipid degradation, and glycoside hydrolysis. This study reveals the contribution of drying to the aroma formation of black tea.

Impact of Pure, Co-, and Sequential Fermentations with Hanseniaspora sp. and Saccharomyces cerevisiae on the Volatile Compounds of Ciders

Pure, co-, and sequential fermentations of Hanseniaspora uvarum, H. guilliermondii, and Saccharomyces cerevisiae strains were evaluated to improve the aromatic quality of ciders. In sequential fermentations, Hanseniaspora strains were used as starter, followed by S. cerevisiae inoculation succeeding one, two, and three days of fermentation. Kinetics, physicochemical parameters, and volatile compounds were assessed during 10 days of fermentation. The headspace technique was used to capture the volatile compounds from the ciders obtained in each experiment and analyzed by gas chromatography. Fermentations with pure strains of Hansenisaspora sp. showed a high population (&gt;1010 CFU/mL) but had a low fermentation rate (2.3–3.8 CO2 g/L/d), low consumption of amino acids (20–40 mg/L) with a high residual content, high sugar consumption (80–90 g/L), and low alcohol content (&lt;2.0% v/v). The H. uvarum strain produced a notably high ester content (245 mg/L). In the co-fermentations, H. guilliermondii with S. cerevisiae highlighted a significant production of higher alcohols, similar to that produced by S. cerevisiae alone (152–165 mg/L). In general, the maximum fermentation rate of the sequential inoculations was lower than co-fermentations but showed low residual nitrogen content (&lt;69 mg/L) and good conversion of sugars into ethanol (4.3–5.7% v/v). The highest concentrations of volatile compounds were observed in treatments involving the two non-conventional strains: H. uvarum with S. cerevisiae inoculation after three days (564 mg/L) and H. guilliermondii after just one day (531 mg/L) of fermentation. These differences stemmed from the metabolic activity of the strains. H. uvarum was influenced by the presence of Saccharomyces, whereas H. guilliermondii did not exhibit this effect. Thus, a pure H. uvarum inoculum has the potential to produce a demi-sec cider with low alcohol content and high content of esters, contributing to a fruity aroma. In addition, ciders with sequential inoculation were the most promising for dry cider processing concerning fermentation parameters and bioaroma enrichment.

Profiling flavor characteristics of cold brew coffee with GC-MS, electronic nose and tongue: effect of roasting degrees and freeze-drying.

Roasting is an important process in the formation of coffee flavor characteristics, which determines the quality of coffee and consumer acceptance. However, the influence of roasting degree on the flavor characteristics of cold brew coffee has not been fully described. In the present study, the flavor characteristics of cold brew coffee with different roasting degrees were compared in detail by using chromatographic and electronic sensory approaches, and the flavor changes induced by freeze-drying were investigated. Pyrazine and heterocyclic compounds were the main aroma compounds in coffee, and gradually dominated with the increase of roasting. Pyridine was consistently present in cold brew coffees of different roasting degrees and showed significant gradient of quantity accumulation. Aroma compounds such as pyrazine, linalool and furfuryl acetate were the main contributors to coffee roasting, floral and fruity flavor. Freeze-drying preserved the fruity and floral aromas of medium-roasted cold brew coffee, whereas reducing the bitterness, astringency and acidity properties that are off-putting to consumers. The higher consumer acceptance and enjoyment in medium roast cold brew coffee may be related to its stronger floral and fruity aroma. The aroma profile qualities of freeze-drying processed medium roasted cold brewed coffee were more dominant and more suitable for freeze-drying processing than medium dark roasting. Application of freeze-drying for cold brew coffee will promote the convenience of drinking. The present study provides valuable technical guidance in improving the flavor and quality of cold brew coffee, and also promotes its commercialization process. © 2024 Society of Chemical Industry.

Analysis of volatile organic compounds in Korean-bred strawberries: insights for improving fruit flavor.

The strawberry industry in South Korea has witnessed a significant 65% growth over the past decade, surpassing other fruits and vegetables in production value. While sweetness and acidity are well-recognized flavor determinants, the role of volatile organic compounds (VOCs) in defining the desirable flavor profiles of strawberries is also crucial. However, existing research has predominantly concentrated on a limited range of commercial cultivars, neglecting the broader spectrum of strawberry varieties. This study embarked on developing a comprehensive VOC database for a diverse array of strawberry cultivars sourced both domestically and internationally. A total of 61 different strawberry cultivars from Korea (45), the USA (7), Japan (8), and France (1) were analyzed for their VOC content using Tenax TA Thermo Desorption tubes and Gas Chromatography-Mass Spectrometry (GC-MS). In addition to VOC profiling, heritability was assessed using one-way ANOVA to compare means among multiple groups, providing insights into the genetic basis of flavor differences. The analysis identified 122 compounds categorized into esters, alcohols, terpenes, and lactones, with esters constituting the majority (46.5%) of total VOCs in Korean cultivars. 'Arihyang', 'Sunnyberry', and 'Kingsberry' exhibited the highest diversity of VOCs detected (97 types), whereas 'Seolhong' showed the highest overall concentration (57.5mg·kg-1 FW). Compared to the USA cultivars, which were abundant in γ-decalactone (a peach-like fruity aroma), most domestic cultivars lacked this compound. Notably, 'Misohyang' displayed a high γ-decalactone content, highlighting its potential as breeding germplasm to improve flavor in Korean strawberries. The findings underscore the importance of a comprehensive VOC analysis across different strawberry cultivars to understand flavor composition. The significant variation in VOC content among the cultivars examined opens avenues for targeted breeding strategies. By leveraging the distinct VOC profiles, particularly the presence of γ-decalactone, breeders can develop new strawberry varieties with enhanced flavor profiles, catering to consumer preferences for both domestic and international markets.

Lactiplantibacillus plantarum and Komagataeibacter europaeus enhance energy metabolism, acetic acid and aromatic amino acids catabolism flux in cider vinegar fermentation

Fruit vinegar is typically produced through a two-stage submerged fermentation involving Saccharomyces cerevisiae (alcohol fermentation) and Acetobacter pasteurianus (acetic acid fermentation). In order to enhance its flavor and nutritional properties, Lactiplantibacillus plantarum and Komagataeibacter europaeus were introduced into the respective stages. The fermentation process was monitored to assess their individual and combined effects, while non-targeted metabolomic analysis aided amino acids and organic acids analysis was applied to characterize the metabolic profiles and identify the differential metabolites.Lactic acid accumulated by L. plantarum, enhanced energy metabolism and ethanol respiratory chain, thereby promoting the K. europaeus growth. In the presence of K. europaeus, A. pasteurianus biomass increased 36–57%, leading to elevated acetic acid synthesis. The co-fermentation systems, especially those containing K. europaeus, exhibited enhanced conversion of shikimic acid to aromatic amino acids and their derivatives such as ferulic acid, isoferulic acid, serotonin, l-kynuanine, phenylacetaldehyde and benzaldehyde. The co-fermentation with K. europaeus and L. plantarum resulted in an enhancement of ethyl phenylacetate, ethyl lactate and ethyl hexanoate production, thereby intensifying the fruity aroma profile. The findings presented here contributed to a deeper comprehension of bioconversion mechanism involving multiple species in cider vinegar fermentation processes.

Changes in nutritional and antioxidant properties, structure, and flavor compounds of Tartary buckwheat (Fagopyrum tataricums) sprouts during domestic cooking

This study aims to investigate the impact of domestic cooking methods, such as microwave, steaming, and boiling, on the color, sensory quality nutritional content, antioxidant capacity, structure, and flavor of Tartary buckwheat (Fagopyrum tataricum) sprouts. According to research, the highest cooking loss in 90 s of microwave was 28.89%. Steaming had been found to have the most significant impact on color loss. Microwaving for 30 s had been observed to increase reducing sugar levels by 4.65%, while boiling for 60 s increased chlorophyll levels by 14.52%. The highest retention rates of total flavonoids, total phenols, and vitamin C were 87.25%, 97.25%, and 92.80% respectively when the food was microwaved for 30 s. Moreover, the microwave treatment exhibited the highest antioxidant capacity. Further analysis using FTIR and SEM techniques revealed an increase in carbonyl content under microwave treatment and the presence of a small amount of ungelatinized starch granules. Different cooking methods had similar effects on flavor, reducing eucalyptol and ethylbenzene content, increasing amyl acetate, hexanal, and limonene content, and the emergence of oily and fruity aromas. This study found that microwaves are the best way to retain the nutritional value of Tartary buckwheat sprouts, providing data reference for the development of future cooking technology.

Identification of Volatile Compounds Contributory to Mango and Tropical-Type Aroma in Whisky

There is an increasing drive across the global distilling industry for a greater understanding of the development of sensory properties in whisky. Origins of the fruity aroma descriptor have been reasonably well-explored in the current literature, but this umbrella term captures a wide range of quite varied sub-descriptors. One such fruit-type lexicon term that has received limited attention is that of mango. The present trial assessed the sensory profiles of 14 commercial whisky products and identified whiskies elevated in the target mango trait. Further analysis of product volatile compound composition allowed for the shortlisting of candidate compounds potentially contributory to this trait. Spiking of candidate compounds into a base whisky identified a potential role for several common whisky components in the development of mango aroma. In particular, aldehyde and acetal components (such as isobutyraldehyde, isovaleraldehyde, and isovaleraldehyde diethyl acetal) were found to positively impact the sensory reporting of mango aroma in whisky. These compounds are not atypical to whisky, and their production pathways and precursors are previously identified; this provides scope for their control without substantial process modification.

Effect of exogenous organic acids on chemical compositions and sensory attributes of fortified sweet wines from dehydrated grapes

In this study, acidity was regulated with the addition of exogenous tartaric acid and citric acid before bottling. The effect of exogenous organic acids on chemical compositions and sensory attributes of fortified sweet wines from dehydrated grapes were investigated. The results indicated that exogenous organic acids promoted the conversion of monomeric anthocyanins to copigmented anthocyanins in wines. Specifically, the combination of malvidin-3-O-glucoside and flavanols (catechin and epicatechin) was facilitated to form copigmented anthocyanins. Sensory analysis suggested that exogenous organic acids improved the balance of sugar and acidity and benefited the harmony in wines on the taste. Wines with a residual sugar and titratable acidity ratio of about 11:1 exhibited the more harmonious taste. In addition, it was also observed changes in the aroma profile related to volatile compounds, namely, more intense fruity aroma in wines with the addition of organic acids.

Development of Assessment Criteria for Managing the Quality of Taishan Black Tea

In order to obtain the quality information of Taishan black tea and provide data support for the establishment of assessment criteria for quality control of Taishan black tea, in this study, 45 samples of Taishan black tea were collected during the summer to investigate their quality characteristics. The results showed that the Taishan black tea typically exhibited a dark-brown, curly appearance and a uniform texture. The tea soup displayed a bright orange-red color. The tea was mainly described as having a fruity aroma, followed by a caramel flavor, sweet aroma, flowery flavor, and clean aroma, with a strong and enduring fragrance. The taste profile was mostly heavy and mellow or heavy and strong, with fewer samples exhibiting slight bitterness and astringency. The tea leaves were characterized by a reddish-auburn color, a soft texture, and an even appearance. The main biochemical components of the Taishan black tea fell within the following ranges: water extracts (38.65–43.35%), free amino acids (1.41–3.45%), tea polyphenols (9.80–15.05%), catechins (6.11–9.03%), and caffeine (1.65–3.05%). The phenolic acid/amino acid ratio was 2.31–6.65%. Catechins and tea polyphenols emerged as critical indicators influencing taste quality, followed by amino acids, water extracts, and caffeine. The aroma analysis identified common compounds, such as 3-methyl-butanal, 2-methyl-butanal, decanal, 2-methyl-propanal, 1-octen-3-ol, and β-ionone, in most samples. These compounds exhibited relatively high contents and high odor activity values, making them the primary contributors to the tea’s aroma. This investigation into the quality of Taishan black tea offers valuable scientific insights, providing a foundation for the standardization of Taishan black tea’s quality.

Metabolomics analysis of flavor differences in Shuixian (Camellia sinensis) tea from different production regions and their microbial associations

Shuixian is renowned for its “rock flavor”. However, the variations in Shuixian flavor are unclear, as the discussion mainly considers regional factors and overlooks the role of microorganisms. Sensory evaluation of Shuixian from three different regions (Zhengyan, Banyan, and Waishan) revealed that each had unique flavor characteristics: a woody aroma with slight acidity, a strong floral and fruity aroma with good freshness, and a distinct sweet aroma and sourness. Metabolomic analyses have revealed that 2-methylpyrazine was a crucial component of the woody aroma, whereas other metabolites contributed to sweet aroma, freshness, and acidity. Moreover, examinations of the relationship between flavor metabolites and microorganisms revealed that fungi had a more pronounced influence on the metabolite content of Shuixian. The study evaluated the role of fermentation microorganisms in shaping the flavor based on Shuixian flavor analyses, contributing to further research into the “rock flavor”, as well as potential microbial interventions.

Aroma and taste analysis of pickled tea from spontaneous and yeast-enhanced fermentation by mass spectrometry and sensory evaluation

Anaerobically fermented pickled tea (PT) can be produced by spontaneous fermentation (SF) or yeast-enhanced fermentation (YF). Aroma and taste characteristics of PT during YF and SF were investigated using sensory evaluation, odour activity, aroma character impact values, HS-SPME-GC–MS, UPLC-QQQ-MS/MS, and spectrophotometry, annotating 198 volatile and 115 non-volatile components. The main contributing volatile components were β-ionone, and 1-octanol, promoted by YF and SF, and yielding floral and fruity aromas respectively. Additionally, compared with SF, YF promoted the formation of citronellol yielding a floral aroma, inhibited the stale aroma of methoxybenzenes, and reduced bitter, astringent, and sour tastes. Furthermore, partial least-squares regression analysis identified the main components related to the ‘acides aroma’ of PT as linalool oxide, n-decanoic acid, hexanoic acid, 3,7-dimethyl-2,6-octadienoic acid, 3-methyl-1-dodecyn-3-ol, and nerolidol. This application could be used as methodology for the comprehensive analysis of tea aroma and taste and these results can act as guidelines for PT production and quality control.

Effects of fermentation with different probiotics on the quality, isoflavone content, and flavor of okara beverages.

The present study aimed to prepare and evaluate a new probiotic functional beverage, using single-probiotic and compound probiotic fermentation on okara. Four different forms of fermentation microorganisms used were Lacticaseibacillus rhamnosus S24 (Lr), Lacticaseibacillus paracasei 6244 (Lp), Lactobacillus acidophilus 11,073 (La), and mixed fermentation (Lr + Lp + La). The physicochemical properties, antioxidant activity, flavor change, and storage period of fermented okara beverages with probiotics were investigated. The results showed that different fermentation schemes could significantly improve the physicochemical properties, antioxidant activity, and sensory quality of the okara beverages. The number of viable bacteria in the Lp group (3.53 × 108 CFU/mL), isoflavone content (0.514 μg/mL) were the highest; total phenol and flavonoid content were 3.32 and 5.68 times higher than in the CK group, respectively. DPPH and ABTS+ free radical scavenging rates were increased by 11.32% and 20%, respectively (p < .05). Through SPME/GC-MS analysis, 44 volatile compounds were identified in the Lr + Lp + La groups, mainly as a result of changes in alcohols and aldehydes produced by fermentation metabolism. It enhances the floral and fruity aroma of the okara beverage. All probiotic-fermented okara beverages can be stored at 4°C for 15 days, with probiotic activity greater than 107 CFU/mL. This study can obtain a probiotic okara beverage rich in soybean isoflavones and with good flavor. Overall, okara can be used to develop functional beverages containing probiotics and contribute to a zero-waste approach in the food industry.

The effects of different rootstocks on aroma components, activities and genes expression of aroma-related enzymes in oriental melon fruit.

Grafting is widely applied in the cultivation of melon. In this study, 'Qinmi No.1' (Cucumis melo L.(QG)) and 'Ribenxuesong' (Cucurbita maxima Duch. (RG)) were used as rootstocks for 'Qingxin Yangjiaocui' (Cucumis melo L.). The results showed that grafting with muskmelon rootstocks had no significant effect on fruit aroma, but grafting with pumpkin rootstocks significantly reduced the odor intensity and odor preference scores of melon fruits. Compared with the fruits from self-grafted plants (SG), four new aromatic volatiles with a sweet smell were detected, the alcohol dehydrogenase (ADH) activity was significantly decreased at 30 DAP, but unaffected at 42 DAP in QG fruits. There was no difference for alcohol acetyltransferase (AAT) activity between QG and SG fruits. The expression level of CmADH2 was significantly higher at 30 DAP and 42 DAP, but CmAAT2 was significantly lower at 42 DAP in QG fruits compared with SG fruits. In RG fruits, the main aroma compounds including butanoic acid ethyl ester, 2-methyl-2-butene-1-al, and 2-methylheptan-1-al were absent, while the volatile compounds with unpleasant odor characteristics including trans, cis-2,6-nonadien-1-ol, (E,E)-2,4-heptadienal, octanoic acid, and styrene were detected. Compared with SG fruits, 1-nonanol and 1-heptanol with green odor characteristics were significantly increased, but eucalyptol and farnesene with fruity aroma characteristics were significantly decreased in RG fruits. The ADH activity of RG fruits was significantly lower than that of SG fruits at 30 DAP and the AAT activity was significantly lower than that of SG fruits at 42 DAP. In addition, the expression levels of CmADH and CmAAT homologs in RG fruits were significantly lower than those in SG or QG fruits. These results show that grafting with pumpkin rootstocks affected the main aroma components, reduced ADH and AAT activities, and down-regulated the expression levels of CmADHs and CmAATs in the melon fruits. This study reveals the mechanism of different rootstocks on melon fruit aroma quality, and lays a theoretical foundation for the selection of rootstocks in melon production. Future studies using overexpression or CRISPR/CAS system to obtain stable transgenic lines of genes encoding key aromatic volatiles, would be promising to effectively improve the flavor quality of melon.