Food research international (Ottawa, Ont.)最新文献

Green is no longer the only color used to describe tea leaves. As tea plants with different leaf colors-white, yellow, and purple-yield significant economic benefits, scholars are growing increasingly curious about whether these differently colored leaves possess unique aromatic characteristics. Headspace solid-phase microextraction (HS-SPME) combined with GC-MS was used to analyze the volatile metabolites of buds and leaves from 7 white-leaf tea plants, 9 yellow-leaf tea plants, 4 purple-leaf tea plants, and 7 normal (green) tea plants. A total of 125 aroma metabolites were identified. The aroma compounds of heterochromatic tea leaves and green-leaf tea were compared separately. It was found that white-leaf tea had the most upregulated compounds (63 up), mainly floral and fruity aromas, including nerol, Z-isogeraniol, and E-3-hexen-1-yl acetate. Purple-leaf tea had the most downregulated compounds (31 down), including β-myrcene, benzyl alcohol, and methyl salicylate, which are related to fresh and fruity aromas. According to variable importance in projection (VIP > 1) and a p-value < 0.05, a total of 40 differential compounds were detected, among which Z-3-hexenol, 1-nonanol, 2,4-di-tert-butylphenol, and 2,6,10,15-tetramethyl-heptadecane were common in all heterochromatic tea. The random forest model constructed using differential metabolites screened out five aroma metabolites, including Z-3-hexenyl isobutyrate, E-3-hexen-1-yl acetate, 2,4-di-tert-butylphenol, Z-jasmone, and Z-isogeraniol. These metabolites demonstrated high accuracy in the model (AUC = 1) and have the potential to serve as characteristic aroma compounds for distinguishing tea leaf colors.

Ya'an Tibetan tea, a dark tea with a rich historical heritage, is typically processed using two primary piling fermentation methods: wet piling with rolled leaves (moisture content around 60%) and dry piling with sun-dried or baked green tea leaves (moisture content below 30%). This study employed sensory evaluation, targeted and non-targeted metabolomics, and fungal Internal Transcribed Spacer (ITS) sequencing to investigate changes in quality components and fungal composition in Tibetan tea processed by both wet and dry-piling methods. The results revealed that 3,7-Dimethyl-1,5,7-octatriene-3-ol and D-limonene were identified as key volatile metabolites contributing to the aroma variations between the dry and wet-piled teas. More pronounced differences were observed in non-volatile components, with 407 differential metabolites identified between the wet- and dry-piled teas. Linear discriminant analysis effect size (LEfSe) identified Rhizomucor, Aspergillus, Thermomyces, Setophoma, and Debaryomyces as the key fungal genera with significant differences between the two piling methods, also dominating in abundance and playing a crucial role in the fermentation process of Tibetan tea. Correlation analysis between microbial communities and differential metabolites showed that Debaryomyces, Thermomyces, and Setophoma were significant contributors to the aroma differences between the teas produced by the two piling methods, while Rhizomucor and Aspergillus had a greater influence on non-volatile metabolites. Since Rhizomucor and Aspergillus were the most dominant fungi in the wet (63.05%) and dry-piled (68.70%) samples, respectively, and showed opposite correlations with major non-volatile differential metabolites, they may underlie the flavor differences between the two piled teas, such as mellowness, thickness, and sweet aftertaste. This study sheds light on the chemical and fungal mechanisms underlying the quality formation of Ya'an Tibetan tea processed by wet and dry piling methods, providing theoretical guidance for the improvement, standardization, and potential enhancement of production efficiency of Ya'an Tibetan tea production.

This study aimed to generate new functional ingredients from microalgae and wine pomace through starter-assisted fermentation. Five lactic acid bacteria (LAB) and five yeasts were variously chosen for their species diversity, origin, and metabolic potential. During fermentation, the combination of Chlorella vulgaris and wine pomace overcame the limited growth observed in pomace substrate, with all LAB and yeasts effectively utilizing sugars and synthesizing microbial metabolites. Additionally, the synergistic interplay between the substrates, alongside the enzyme specificity of the starter cultures, improved the bioavailability of phenolic compounds, particularly flavanols, flavonols, and procyanidins, while simultaneously generating unique peptides in the formulated ingredients. In some cases, these metabolic changes were associated with enhanced antioxidant activity, improved protein digestibility, and overall protein quality. Our findings highlighted the potential of fermented mixed substrates as new functional ingredients, with promising health-promoting benefits and significant potential for applications in the food industry.

Lactiplantibacillus plantarum and Staphylococcus xylosus are common starters for fermented sausages. Several studies have demonstrated the impact of these two strains on the quality of fermented sausages. However, the mechanism underlying the effects of these two microorganisms on co-cultivation in sausages remains unclear. This study aimed to investigate the effects of inoculation with various combinations of starters on the microbial communities and metabolic profiles of fermented sausages. High-throughput sequencing revealed that, during sausage fermentation, Firmicutes was the dominant bacterial phylum, and the primary microorganisms were Lactococcus, Staphylococcus, Lactobacillus, and Pseudomonas. On the last day of fermentation, the highest abundance of Staphylococcus was observed in the co-inoculation group. Furthermore, inoculated fermentation effectively inhibited the growth of pathogenic and spoilage bacteria. Metabolomic analysis of the four groups of samples identified 208 metabolites in positive ion mode and 109 in negative ion mode. A total of 31 differential metabolites were identified (P < 0.05, variable importance in the projection >1.5), primarily benzene and substituted derivatives, carboxylic acids and derivatives, and fatty acyls. Five crucial differential metabolites (subaphylline, naringenin, 1-hexadecanol, beta-alanyl-L-lysine, and 3'-AMP) were identified as potential biomarkers for fermented sausages. Key differential metabolite metabolic pathways indicated that L. plantarum YR07 dominated in metabolite regulation during sausage fermentation, and S. xylosus Y-18 downregulated the fatty acid degradation pathway, which also affected the metabolism of fermented sausages. Co-cultivation of the two bacteria exhibited a synergistic effect on the metabolism of the fermented sausages. This study offers further insights into improving the quality of fermented sausages, thereby establishing a theoretical foundation for the production of excellent fermenters.

Drying is the step that is to be used to adjust and control the formation of flavour and quality in black tea processing. In the present work, the comprehensive two-dimensional gas chromatography with mass spectrometry (GC × GC-MS) and gas chromatography olfactometry with mass (GC-O-MS) were used to determine the dynamic change of the volatile compounds in black tea during drying at 90, 120, 150 °C for 1 h. Results showed that the ratio of esters and aldehydes largely declined when temperature was elevated from 90 °C to 150 °C, while the ratio of heterocycles was increased to 22.4 % from 16.5 %. A total of 15 key aroma activity volatiles were screened out in three temperature dried samples, therein 11 volatiles were connected with the Maillard reaction, meaning these volatiles were highly relevant to the degradation of amino acids during the drying process. We detected that 21 amino acids were decreased with enhanced temperature and extended the drying time, which promoted the Maillard-derived volatiles formation. Therefore, it was suggested that to control the degradation of amino acids adjust the flavour profiles of black tea by changing the drying temperature and time.

Galactomannan comes from a wide range of plant resources and has some biological activities, but its bioavailability is limited due to its large molecular weight and complex structure. In this study, three degradation methods (H₂O₂, ultrasound, and β-mannanase) combined with ethanol fractional precipitation (25 %, 50 %, and 75 %) were used to degrade and separate Gleditsia sinensis galactomannans (GSG), and the physicochemical properties and biological activities of GSG after degradation were analyzed. Comprehensive comparison indicates that H₂O₂ exhibits had a better degradation effect. After 4 h of degradation using 4 % H₂O₂, the yield of GSG precipitated with 50 % ethanol was 37.06 % (the yield of undigested GSG is 1.80 %). Simultaneously, the molecular weight (reduced from 225.25 to 36.87 kDa) and viscosity were significantly reduced under this condition, while the solubility was increased. In addition, the low-molecular-weight GSG (LGSG) obtained by 4 % H₂O₂/50 % ethanol showed the strongest free radical scavenging activity in vitro. Furthermore, the results of in vivo antioxidant assays showed that LGSG inhibited Aflatoxin B1-induced developmental toxicity by regulating gene expression in the Keap1/Nrf2 pathway. LGSG also promoted Nrf2-mediated expression of the lipid metabolism genes ppar-α and cpt1, while suppressing expression of the fatty acid synthesis genes fas and scd-1. Therefore, the liver recovered from lipid peroxidation induced nonalcoholic fatty liver disease (NAFLD). The present study introduces a method for green and efficient preparation of LGSG, indicates its potential as a nutritional product.

With an ever-increasing global population and dwindling natural resources, a shift towards more sustainable food systems is required. Important aspects to aid in this transition are the reduction of food waste, and a movement towards non-animal protein sources. Brewers spent yeast (BSY) is an abundant by-product of the brewing industry, which is generally regarded as waste, despite its high nutritional value. Previous work has shown that fermentation of BSY with Lactobacillus amylovorus FST 2.11 resulted in changes in composition, functionality, and improved palatability of the processed raw material (PBSY). In this study, in vitro protein digestibility, amino acid bioaccessability, and protein quality of PBSY was explored using the static INFOGEST in vitro model. In vitro protein digestibility of PBSY (73.0 %) was almost two-fold higher than that of CBSY (40.0 %), while PBSY also displayed significantly higher in vitro bioaccessability values for all essential amino acids, except for tryptophan. Investigation of protein quality using the digestible indispensable amino acid score (DIAAS) values and the FAO recommended amino acid scoring pattern for individuals >3 years old showed that the protein quality for CBSY was low (DIAAS of 17.0 %), while PBSY was considered to be of "good" protein quality (DIAAS of 98.2 %). Investigation of the modulation potential of PBSY on the gut microbiome using an in vitro colon model system showed an increase in gut microbiome α-diversity indices and an abundance of beneficial Mediterranean diet-responsive taxa after 24 h. Overall, this study highlights the potential of BSY as raw material for the production of a high-quality food ingredient with potential prebiotic effects, aiding in the reduction food waste and supporting global food systems.

Fermented foods of the Indian Himalaya are unexplored functional resources with high nutritional potential. Chhurpi cheese, fermented by defined native proteolytic lactic acid bacteria of Sikkim was assessed for ACE inhibitory, HOCl reducing, and MPO inhibitory, activity across varying stages of gastrointestinal (GI) digestion. The enhanced bioactivity of Lactobacillus delbrueckii WS4 chhurpi was associated with the generation of bioactive and multifunctional peptides during fermentation and GI digestion. Qualitative and quantitative in silico tools were employed for prediction of ACE inhibitory activity of novel chhurpi peptides. Selected peptides, with highest predictive ACE inhibitory potential were synthesized and in vitro validation revealed the ACE inhibitory potential of peptides HPHPHLSFM and LKPTPEGDL. LKPTPEGDL showed the most potent ACE inhibitory activity (IC₅₀ of 25.82 ± 0.26 µmol) which slightly decreased upon GI digestion. The peptides demonstrated a non-competitive type mixed ACE inhibition modality. Furthermore, the two peptides exerted observable HOCl reducing and MPO inhibitory activity, demonstrating their antioxidative potential. HPHPHLSFM exhibited superior HOCl reduction (EC₅₀ of 0.29 ± 0.01 mmol), while LKPTPEGDL demonstrated higher MPO (IC₅₀ of 0.29 ± 0.01 mmol) inhibition. Molecular docking of the two peptides with MPO revealed proline and aspartate near peptidyl C-terminus to bind with enzyme catalytic residues. This study presents the first peptidome analysis of chhurpi produced through controlled fermentation and identifies novel peptides with MPO and ACE inhibitory activity. Furthermore, it marks the first synthesis and in vitro bioactivity validation of bioactive peptides from chhurpi cheese, highlighting its multifunctional potential.

Maillard reaction products (MRPs) were prepared at high temperatures using soybean protein hydrolysates (SPH) and reducing pentose (xylose and arabinose), hexose (galactose and glucose), and disaccharide (maltose), and their potential as flavoring in plant protein foods was evaluated. The results indicated that, after sugar was involved in the reaction, the unfolding of proteins enabled aromatic amino acid residues to enter a more hydrophobic environment, contributing to the reduction of bitterness in MRPs and formation of caramelization. This effect was partially attributed to the interaction forces, hydrogen bonds and van der Waals forces, that existed between the sugars and SPH involved in Maillard reaction. More basic amino acid residues interacted with pentose during the reaction, which exhibited faster reaction rate and promoted the formation of pyrazines and oxygen containing compounds, thereby contributing to meaty, roasted and caramelized flavors. Trimethyl pyrazine, 3-ethyl-2,5-dimethylpyrazine, 2-methylpyrazine, and 2-heptanone were the most abundant in pentose MRPs, and these volatile compounds were positively correlated with umami and richness. Overall, MRPs prepared with arabinose may serve as a potential meaty flavoring with notable umami, and hexose contributed to the enrichment of nutty flavor profiles, while the MRPs formed by disaccharide exhibited the characteristics of superior fruity aromas. MRPs from different reducing sugar may be used to develop different food ingredients.

1,3-dioleoyl-2-palmitoylglycerol (OPO) and 1-oleoyl-2-palmitoyl-3-linoleoylglycerol (OPL) are two essential types of human milk fat substitutes (HMFS). Their unique fatty acid composition and distribution play a significant role in promoting infant health, making the reaction conversion and acyl migration critical factors for developing efficient preparation methods. Promoting the conversion of the substrate while simultaneously inhibiting acyl migration is crucial for obtaining the desired HMFS products. In this study, we comparatively investigated enzymatic acidolysis and transesterification for HMFS production and revealed enzymatic kinetics as well as acyl migration mechanism during the process. Acyl migration was observed through the lipase-catalyzed mechanism, and the associated free energy changes were analyzed using density functional theory (DFT). The presence of long-chain fatty acids in the synthesis system resulted in intermediates with higher relative free energy during acyl migration. Based on these findings, we propose a novel synthesis strategy consisting of multi-step transesterification and dry fractionation, leveraging the differences in freezing points to minimize acyl migration. The resulting OPO product contains 90.42% oleic acid specifically at the sn-1,3 positions, highlighting its potential application in infant formulas. This study presents a systematic investigation of the kinetics and mechanisms involved in lipase-mediated HMFS production, providing valuable insights for rational synthesis approaches.