The aroma transformation of Japanese sea bass (Lateolabrax japonicas) through endogenous enzyme incubation during the lag phase of attached microorganisms.

Endogenous enzymes play a crucial role in determining fish product aroma. However, the attached microorganisms can promote enzyme production, making it challenging to identify specific aromatic compounds resulting from endogenous enzymes. Thus, we investigated the aroma transformation of Japanese sea bass through enzymatic incubation by controlling attached microorganisms during the lag phase. Our results demonstrate that enzymatic incubation significantly enhances grassy and sweet notes while reducing fishy odors. These changes in aroma are associated with increased levels of 10 volatile compounds and decreased levels of 3 volatile compounds. Among them, previous studies have reported enzyme reaction pathways for octanal, 1-nonanal, vanillin, indole, linalool, geraniol, citral, and 6-methyl-5-hepten-2-one; however, the enzymatic reaction pathways for germacrene D, beta-caryophyllene, pristane, 1-tetradecene and trans-beta-ocimene remain unclear. These findings provide novel insights for further study to elucidate the impact of endogenous enzymes on fish product aromas.

Reduction of aldehydes with green odor in soy products during fermentation with Lycoperdon pyriforme and analysis of their degradation products.

Soy products are rejected by Western consumers because of their green and beany off-aroma. The off-aroma profiles of typical soy products (soy drink and soy protein isolate) were analyzed and forty-five regions imparting green and beany odor impressions were perceived after application of direct immersion-stir bar sorptive extraction coupled with gas chromatography-mass spectrometry-olfactometry. After a fermentation of 28 h with Lycoperdon pyriforme the intensity of the off-aroma was reduced. Accordingly, thirteen and fourteen of the thirty-five quantified compounds were significantly decreased after fermentation of soy drink and soy protein isolate, respectively. The major off-aroma contributors, aldehydes, were reduced during fermentation and their degradation products were analyzed. The following bio-pathways were suggested (i) saturated aldehydes were reduced to the corresponding alcohols with increased odor threshold, leading to less intense sensorial perception, and (ii) di-unsaturated aldehydes did not form any odor-active substance in the volatile spectrum. Both of the phenomena explained the decreased sensorial perception of the off-aroma.

α-D-1,6-glucan from Castanea mollissima Blume alleviates dextran sulfate sodium-induced colitis in vivo.

A homogenous α-D-1,6-glucan (CPA) was extracted from Castanea mollissima Blume. The effect of CPA on ameliorating dextran sulfate sodium induced colitis was investigated. CPA repressed TNF-α and IL-1ß level in LPS stimulated RAW264.7 cells. After the intragastric administration of CPA (200 or 400 mg/kg/day), the colon length and body weights of mice with colitis increased and the disease activity index reduced. CPA alleviated colon tissue damage by elevating ZO-1 and occludin protein levels and regulating TNF-α and IL-1ß by inhibiting the protein expression of NLPR3 and NF-κB p65. The abundance of Bacteroidetes and Firmicutes was altered and short-chain fatty acid (SCFA) levels, especially propionic, butyric, and isovaleric acids increased significantly. These results indicated that CPA could alleviate colitis by protecting mucosal barriers, reducing inflammation, and regulating intestinal microbiota and SCFA levels. Thus, CPA can be developed as a functional food for the prevention and treatment of colitis.

Fine tuning of medium chain fatty acids levels increases fruity ester production during alcoholic fermentation.

Pichia fermentans Z9Y-3 and its intracellular enzymes were inoculated along with S. cerevisiae in synthetic grape must to modulate fruity ester production. The levels of ester-related enzymes, ester precursors, and fruity esters were monitored every 24 h during fermentation. Results showed that the levels of ethyl acetate, acetate higher alcohol esters (AHEs), short chain fatty acid ethyl esters (SFEs), and medium chain fatty acid ethyl esters (MFEs) were significantly enhanced in mixed fermentation. Pearson correlation analysis further revealed that higher alcohols and fatty acids played a more important role in fruity ester production than enzymes; Particularly, the correlation coefficient between fatty acids and MFEs was 0.940. In addition, supplementation of medium chain fatty acids (7.2 mg/L) at the metaphase of single S. cerevisiae fermentation improved ethyl acetate, AHE, SFE, and MFE production by 42.56%, 21.00%, 61.33%, and 90.04%, respectively, although the high level of ethyl acetate might result in off-flavors.

Using an electronic nose and volatilome analysis to differentiate sparkling wines obtained under different conditions of temperature, ageing time and yeast formats.

Effect of yeast inoculation format (F), temperature (T), and "on lees" ageing time (t) factors were evaluated on the composition of sparkling wines by a quantitative fingerprint obtained from volatile metabolites and the response of an electronic nose (E-nose). Wines elaborated according the traditional method at 10 and 14 °C, free cells and yeast biocapsules formats were monitored at 15 and 24 months of ageing time. Sixty-six volatiles identified and quantified in the eight sampling lots were subjected to a pattern recognition technique. A dual criterion based on univariate (ANOVA) and multivariate analysis (PLS-DA) through the variable importance projection (VIP) values, allowed to identify ten volatiles as potential markers for T factor, eleven for t and twelve for F factors. The discriminant models based on E-nose dataset enable a 100% correct classification of samples, in relation with t and F factors and the 83% for T factor.

Active food packaging through controlled in situ production and release of hexanal.

Transportation and storage of vegetables and fruits, including berries, is increasing to meet growing consumer demand for fresh foods. Ripening and softening of plant tissues may be slowed down by hexanal, a safe volatile compound that also has antimicrobial properties. Thus hexanal could be applied during the food distribution chain to slow down the spoilage of plant-based products and reduce food waste. Nonetheless, due to the rapid evaporation of hexanal, a constant supply is needed. Our aim was to develop a concept to incorporate food-grade sunflower oil in a polysaccharide aerogel matrix for controlled in situ production and release of hexanal. We compared enzyme- and light-catalyzed lipid oxidation reactions, determined the release of hexanal at different conditions, and performed storage stability tests of blueberries and cherry tomatoes. The lipid-loaded aerogels assessed here are a potential novel delivery matrix for controlled hexanal formation to extend the shelf life of plant-based products.

Gluten free sourdough bread enriched with cricket flour for protein fortification: Antioxidant improvement and Volatilome characterization.

Insects represent a novel source of edible high nutritional value proteins which are gaining increasing interest as an alternative to traditional animal foods. In this work, cricket flour was used to produce gluten-free sourdough breads, suitable for celiac people and "source of proteins". The doughs were fermented by different methods and pH and microbial growth, volatile compounds, protein profile, and antioxidant activity, before and after baking, were analyzed and compared to standard gluten-free doughs. The results showed that cricket-enriched doughs and the standard had similar fermentation processes. Cricket enrichment conferred to the breads a typical flavoring profile, characterized by a unique bouquet of volatile compounds, made by nonanoic acid, 2,4-nonadienal (E,E), 1-hexanol, 1-heptanol, and 3-octen-2-one, expressed in different amounts depending on the type of inoculum. Finally, antioxidant activities were significantly enhanced in cricket breads, indicating that cricket powder provides to bakery gluten-free goods high nutritional value proteins and antioxidant properties.

Use of a flor yeast strain for the second fermentation of sparkling wines: Effect of endogenous CO2 over-pressure on the volatilome.

Saccharomyces cerevisiae flor yeast is used for the first time in sparkling wine-making. Twenty-six oenological variables and fifty-three volatile metabolites are quantified in the middle (P = 3 bar) and at the end (P = 6 bar) of the second fermentation, carried out in open and closed bottles. A heat-map of volatiles and the fingerprints obtained for ten chemical families and ten odorant series visualize the changes for each condition. Terpenes, fatty acids and volatile phenols increased their contents by pressure effect at the end of the study by 25.0, 7.8 and 2.2%, respectively. The remaining families decrease between 17.4% and 30.1% for furanic compounds and esters in the same stage. A Principal Component Analysis established that nine volatiles are mainly affected by pressure and five by fermentation stage. The use of ethanol-tolerant flor yeasts constitutes an innovative procedure for the enhancement of the sparkling wines diversification.

Characterization of key odorants causing the roasted and mud-like aromas in strong-aroma types of base Baijiu.

The roasted and mud-like aromas in Chinese strong-aroma types of base Baijiu (base SAB) and the interactions among the corresponding key compounds causing these two characteristic aromas were investigated. A total of 68 and 64 odorants were identified in the base and commercial SAB by comparative aroma extract dilution analysis. Furthermore, the complex matrix of Baijiu always pose a long-term challenge for quantitative accuracy and precision of target aroma compounds; thus, the odorants with flavor dilution (FD) ≥ 9 were further quantified by multiple quantitative techniques, including the direct injection combined with gas chromatography-flame ionization detector, the vortex-assisted surfactant-enhanced emulsification liquid-liquid microextraction (VSLLME) combined with GC-MS, and the derivatization method combined with VSLLME-GC-MS, and 37 and 26 odorants were shown to be important odorants as their OAVs ≥1. Among these components, 5 compounds, hexanoic acid, butyric acid, p-cresol, 3-methylindole, and 3-(methylthio)propanal showed higher OAVs in base than in commercial SAB, and based on aroma recombination and omission analysis, they were confirmed to be the key odorants responsible for the mud-like and roasted odors. The evaluation of the aforementioned five key odorants by the "addition" test showed that the roasted and mud-like aromas of base SAB were related, and the odors were mainly attributed to additive or masking effects among the compounds.

Assessment of sugar content, fatty acids, free amino acids, and volatile profiles in jujube fruits at different ripening stages.

Volatile profiles of jujube fruits at different ripening stages were characterized by GC-MS and E-nose. Changes in the possible precursors of volatile components were also investigated. Four ripening stages were established: GM, green maturity; YM, yellow maturity; HRM, half-red maturity; RM, red maturity. Fruit maturity showed significant effect on the volatile components and their precursors. (E)-2-hexenal was the most abundant component which showed rising trend from 169.2 µg/kg (GM) to 733.4 µg/kg (RM). Glucose and fructose showed a decreasing tendency during ripening. As the important precursors of jujube flavor, seven fatty acids were identified, the predominant ones were C16:0, C16:1n7, C18:1n9c and C18:2n6c; twenty-six free amino acids were quantified, in which l-AspNH2 and l-Pro were the abundant components. Owing to the highest content of total aldehydes (59.33%) and the strongest responses of E-nose, jujubes at HRM stage showed superior overall flavor quality among all the samples.

Dispersed phase volume fraction, weak acids and Tween 80 in a model emulsion: Effect on the germination and growth of Bacillus weihenstephanensis KBAB4 spores.

In foodstuffs, physico-chemical interactions and/or physical constraints between spores, inhibitors and food components may exist. Thus, the objective of this study was to investigate such interactions using a model emulsion as a microbial medium in order to improve bacterial spore control with better knowledge of the interactions in the formulation. Emulsions were prepared with hexadecane mixed with nutrient broth using sonication and were stabilized by Tween 80 and Span 80. The hexadecane ratio was either 35% (v/v) or 50% (v/v) and each emulsion was studied in the presence of organic acid (acetic, lactic or hexanoic) at two pH levels (5.5 and 6). Self-diffusion coefficients of emulsion components and the organic acids were measured by Pulsed Field Gradient-Nuclear Magnetic Resonance (PFG-NMR). The inhibition effect on the spore germination and cell growth of Bacillus weihenstephanensis KBAB4 was characterized by the measure of the probability of growth using the most probable number methodology, and the measure of the time taken for the cells to germinate and grow using a single cell Bioscreen® method and using flow cytometry. The inhibition of spore germination and growth in the model emulsion depended on the dispersed phase volume fraction and the pH value. The effect of the dispersed phase volume fraction was due to a combination of (i) the lipophilicity of the biocide, hexanoic acid, that may have had an impact on the distribution of organic acid between hexadecane and the aqueous phases and (ii) the antimicrobial activity of the emulsifier Tween 80 detected at the acidic pH value. The interface phenomena seemed to have a major influence. Future work will focus on the exploration of these phenomena at the interface.

Evaluating the microbial ecology and metabolite profile in Kazak artisanal cheeses from Xinjiang, China.

Kazak artisanal cheese is one of the famous fermented food in Uighur Autonomy Region of Xinjiang, China. However, the microbial ecology in Kazak artisanal cheeses across different regions is unclear. In this study, we determined the microbial community composition through amplicon sequencing and measured the flavor profile of 10 cheese samples from different regions of Xinjiang. The associations between microbial communities, flavors and environmental factors were examined by redundancy analysis and Monte Carlo permutation test. Cheeses from different regions had different microbial communities, which was mainly reflected in the relative abundance of Lactobacillus, Streptococcus, Issatchenkia, Debaryomyces and Kluyveromyces. In addition, Pichia and Torulaspora were also the key microbial groups, according to the high relative abundance and large co-occurrence incidence in the correlation network. Using the microbe-metabolites correlation analysis, the major flavor-producing taxa were identified as Kluyveromyces, Anoxybacillus, Torulaspora, Lactobacillus, Streptococcus and Dipodascus. Environmental factors accounted for the majority of the microbial community variations, 88.54% for bacteria and 75.71% for fungi. Compared to physico-chemical factors (temperature, moisture, and pH), geographical factors (longitude, latitude and elevation) had a stronger effect on microbial communities in cheese samples from different regions of Xinjiang.

Dynamic correlations between microbiota succession and flavor development involved in the ripening of Kazak artisanal cheese.

Cheese is a typical handcrafted fermented food in Kazak minority from the Uighur Autonomy Region in China. The ripening process of the cheese is crucial for quality and flavor. The aim of this study was to gain a deeper knowledge on the bacterial and fungal community diversity at different time points during the post-ripening of the cheese and to understand the relationship between bacterial and fungal profiles and the chemical components including amino acids, fatty acids and volatile compounds related the cheese flavor. Cheese samples were collected from days 5, 10, 15, 20 and 30 after the starting point of post-ripening. The bacterial and fungal compositions were analyzed with next generation sequencing targeting the 16S rDNA loci for bacteria and ITS loci for fungi. The amino acids contents were analyzed by reversed phase high performance liquid chromatography combined with UV detection. The fatty acids and the volatile components were analyzed by Solid Phase Micro Extraction followed by Gas Chromatography/Mass spectrometry. We found that Lactobacillus, Streptococcus, Kluyveromyces and Torulaspora were the dominant cheese's population. Bidirectional orthogonal partial least squares (O2PLS) based correlation analysis between microbiota succession and flavor dynamics showed that bacteria made more contributions to flavor formation than fungi. Eight bacteria genera and seven fungi genera were determined as functional core microbiota for the flavor production based on their dominance and functionality in microbial community. This study provided a comprehensive picture of the dynamic changes of microbiota profiles through the post-ripening process. The elucidation of the causal relationship between microbiota and the flavor components has advanced our understanding of the mechanism underlying the cheese development.

Characterization of odor-active compounds of chicken broth and improved flavor by thermal modulation in electrical stewpots.

The influence of high temperature modes (cooking in traditional clay stewpot (TS) and cooking in commercial ceramic electrical stewpot (CS)) and low temperature modes (cooking in electrical stewpot with Temperature Modulations, TM1-TM6) on chicken broth sensory evaluation and flavor profile was studied. Sensory evaluation results showed that chicken broth processed using TM1 had the best flavor with higher chicken meat-like and lower off-flavor scores. Gas chromatography-mass spectrometry (GC-MS) and GC-MS/olfactometry (GC-MS/O) results revealed that the TM1 samples had the most abundant odorants. The umami-taste components from TM1 samples such as umami free amino acids and inosine 5'-monophosphate (IMP) had the highest amount, 20.0 ±â€¯0.10 mg/g chicken broth and 17.19 ±â€¯0.58 µg/g chicken broth respectively. The relationship between sensory evaluation and odor-active compounds were evaluated by Partial Least Squares Regression (PLSR), and the PLSR analysis indicated that heptanal, benzaldehyde, (Z)-2-decenal, (E,E)-2,4-decadienal, 1-pentanol, 2-undecanone, 2-pentyl-furan and one unknown compound were significantly and positively correlated with chicken meat-like note. Whereas, fatty aroma were significantly and positively correlated with octanal, (E,E)-2,4-decadienal and 1-pentanol. (E,E)-2,4-Decadienal and 2-undecanone had a significant and negative correlation with off-flavor attribute.

Characterization of volatile profile from ten different varieties of Chinese jujubes by HS-SPME/GC-MS coupled with E-nose.

Volatile profile of ten different varieties of fresh jujubes was characterized by HS-SPME/GC-MS (headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry) and E-nose (electronic nose). GC-MS results showed that a total of 51 aroma compounds were identified in jujubes, hexanoic acid, hexanal, (E)-2-hexenal, (Z)-2-heptenal, benzaldehyde and (E)-2-nonenal were the main aroma components with contributions that over 70%. Differentiation of jujube varieties was conducted by cluster analysis of GC-MS data and principal component analysis & linear discriminant analysis of E-nose data. Both results showed that jujubes could be mainly divided into two groups: group A (JZ, PDDZ, JSXZ and LWZZ) and group B (BZ, YZ, MZ, XZ and DZ). There were significant differences in contents of alcohols, acids and aromatic compounds between group A and B. GC-MS coupled with E-nose could be a fast and accurate method to identify the general flavor difference in different varieties of jujubes.

Comparison of orthologous cyanobacterial aldehyde deformylating oxygenases in the production of volatile C3-C7 alkanes in engineered E. coli.

Aldehyde deformylating oxygenase (ADO) is a unique enzyme found exclusively in photosynthetic cyanobacteria, which natively converts acyl aldehyde precursors into hydrocarbon products embedded in cellular lipid bilayers. This capacity has opened doors for potential biotechnological applications aiming at biological production of diesel-range alkanes and alkenes, which are compatible with the nonrenewable petroleum-derived end-products in current use. The development of production platforms, however, has been limited by the relative inefficiency of ADO enzyme, promoting research towards finding new strategies and information to be used for rational design of enhanced pathways for hydrocarbon over-expression. In this work we present an optimized approach to study different ADO orthologs derived from different cyanobacterial species in an in vivo set-up in Escherichia coli. The system enabled comparison of alternative ADOs for the production efficiency of short-chain volatile C3-C7 alkanes, propane, pentane and heptane, and provided insight on the differences in substrate preference, catalytic efficiency and limitations associated with the enzymes. The work concentrated on five ADO orthologs which represent the most extensively studied cyanobacterial species in the field, and revealed distinct differences between the enzymes. In most cases the ADO from Nostoc punctiforme PCC 73102 performed the best in respect to yields and initial rates for the production of the volatile hydrocarbons. At the other extreme, the system harboring the ADO form Synechococcus sp. RS9917 produced very low amounts of the short-chain alkanes, primarily due to poor accumulation of the enzyme in E. coli. The ADOs from Synechocystis sp. PCC 6803 and Prochlorococcus marinus MIT9313, and the corresponding variant A134F displayed less divergence, although variation between chain-length preferences could be observed. The results confirmed the general trend of ADOs having decreasing catalytic efficiency towards precursors of decreasing chain-length, while expanding the knowledge on the species-specific traits, which may aid future pathway design and structure-based engineering of ADO for more efficient hydrocarbon production systems.

Effect of xanthan gum on the release of strawberry flavor in formulated soy beverage.

The effects of xanthan gum on the release of strawberry flavor compounds in formulated soy protein isolate (SPI) beverage were investigated by headspace gas chromatography (GC). Seven strawberry flavor compounds (limonene, ethyl hexanoate, (Z)-3-hexenyl acetate, ethyl 2-methylbutanoate, ethyl butanoate, (Z)-3-hexen-1-ol and diacetyl) could be detected by GC and hence analyzed the gas-matrix partition coefficients (K). The release of flavor compounds was restrained in SPI and/or xanthan gum solution. The retention of (Z)-3-hexen-1-ol, limonene and diacetyl significantly changed (p<0.05) with increasing xanthan gum concentrations. Presence of any other esters led to suppression of the release of ester compounds in water and SPI solution. The less-volatiles (γ-decalactone, methyl cinnamate, hexanoic acid, 2-methyl butyric acid and furaneol) accelerated the release of ester compounds to some extent in different matrices. The above results demonstrated that presence of SPI and xanthan gum could bring about an imbalance in the strawberry flavor.

Development of spoilage bacterial community and volatile compounds in chilled beef under vacuum or high oxygen atmospheres.

Research into microbial community development and metabolism is essential to understand meat spoilage. Recent years have seen the emergence of powerful molecular techniques that are being used alongside conventional microbiology approaches. This enables more accurate studies on meat spoilage. The aim of this study was to investigate the influence of packaging (under vacuum and in high oxygen atmosphere) on the development of microbial communities and metabolic activities at 6 °C by using culture-dependent (cultivation, ribotyping) and culture-independent (amplicon sequencing) methods. At the beginning of shelf life, the microbial community mostly consisted of Carnobacterium and Lactobacillus. After two weeks of storage, Lactococcus and Lactobacillus were the dominant genera under vacuum and Leuconostoc in high oxygen meat packages. This indicates that oxygen favoured the genus Leuconostoc comprising only heterofermentative species and hence potential producers of undesirable compounds. Also the number of volatile compounds, such as diacetyl, 1-octen-3-ol and hexanoic acids, was higher in high oxygen packages than under vacuum packages. The beef in high oxygen atmosphere packaging was detected as spoiled in sensory evaluation over 10 days earlier than beef under vacuum packaging. Leuconostoc gelidum, Lactococcus piscium, Lactobacillus sakei and Lactobacillus algidus were the most common species of bacteria. The results obtained from identification of the isolates using ribotyping and amplicon sequencing correlated, except for L. algidus, which was detected in both types of packaging by amplicon sequencing, but only in vacuum packaged samples using the culture-based technique. This indicates that L. algidus grew, but was not cultivable in high oxygen beef using the Nordic Committee on Food Analysis standard method.

Development of a method for identification and accurate quantitation of aroma compounds in Chinese Daohuaxiang liquors based on SPME using a sol-gel fibre.

Aroma compositions of Chinese Daohuaxiang liquors, including five kinds of commercial liquors and three kinds of base liquors, were extracted by solid phase microextraction using a sol-gel divinylbenzene/hydroxy-terminated silicone oil fibre. The effectiveness of the fibre was evaluated in comparison with commercial fibres and liquid-liquid extraction. After identification by GC-MS and GC-O, the compounds were accurately quantified by GC-FID using internal standards. Wide linear ranges, low limits of detection, satisfactory precision and recoveries were achieved. A total of 57 volatile compounds were detected and 28 of them were quantified. Most of them were common in these liquors but differed in terms of their relative amounts. Thirteen out of the 28 compounds had odour activity values greater than 1 in all of the liquors, and are suggested to be the key aroma-contributing substances of Daohuaxiang liquors. Besides, the differences among different aroma types and kinds of Daohuaxiang liquors were also discussed.

In vitro determination of volatile compound development during starter culture-controlled fermentation of Cucurbitaceae cotyledons.

The effects of Lactobacillus plantarum UFLA CH3, Pediococcus acidilactici UFLA BFFCX 27.1, and Torulaspora delbrueckii UFLA FFT2.4 inoculation on the volatile compound profile of fermentation of Cucumeropsis mannii cotyledons were investigated. Different microbial associations were used as starters. All associations displayed the ability to ferment the cotyledons as judged by lowering the pH from 6.4 to 4.4-5 within 24h and increasing organic acids such as lactate and acetate. The population of lactic acid bacteria (LAB) and yeasts increased during fermentation. In the fermentation performed without inoculation (control), the LAB and yeast populations were lower than those in inoculated assays at the beginning, but they reached similar populations after 48 h. The Enterobacteriaceae population decreased during the fermentation, and they were not detected at 48 h in the L. plantarum UFLA CH3 and P. acidilactici UFLA BFFCX 27.1 (LP+PA) and L. plantarum UFLA CH3, P. acidilactici UFLA BFFCX 27.1, and T. delbrueckii UFLA FFT2.4 (LP+PA+TD) samples. The assays inoculated with the yeast T. delbrueckii UFLA FFT2.4 exhibited the majority of volatile compounds (13 compounds) characterized by pleasant notes. The LP+PA+TD association seemed to be appropriate to ferment C. mannii cotyledons. It was able to control the Enterobacteriaceae population, and achieved high concentrations of esters and low concentrations of aldehydes and ketones.