Free Amino Acid Content Research Articles

Nutritional, Biochemical, and Functional Properties of Spinach Leaf-Enriched Dough: A Healthier Alternative to Conventional Pasta

This study explored the effects of spinach flour (SF) enrichment on pasta, focusing on chemical, nutritional and sensory properties, cooking performance, and microbiological stability. SF was added at 12.5% (PSP12) and 25% (PSP25). The enriched pasta had a lower pH than the control (CP), due to spinach-derived organic acids, with PSP25 showing the highest fiber content. Enrichment increased B vitamins and minerals, especially calcium, magnesium, sodium, and potassium. PSP25 had a shorter cooking time, higher water absorption, and greater cooking loss. Enriched pasta showed lower starch hydrolysis index and predicted glycemic index, suggesting potential benefits for managing postprandial blood sugar levels. SF significantly altered the free amino acid (FAA) profile, with PSP25 showing the highest concentration of total FAAs. Antioxidant assays demonstrated that spinach-enriched pasta retained higher levels of phenols and flavonoids, after cooking also, compared to CP. Sensory analysis indicated that while PSP12 had higher overall acceptability, PSP25 exhibited stronger herbaceous flavors, which could affect consumer preference. Microbiologically, all samples were stable for 110 days. The findings suggest that SF enrichment enhances the nutritional value, antioxidant potential, and sensory qualities of pasta, with potential for commercial applications, although consumer acceptance could be influenced by its non-traditional taste and texture.

Enhanced Oligopeptide and Free Tryptophan Release from Chickpea and Lentil Proteins: A Comparative Study of Enzymatic Modification with Bromelain, Ficin, and Papain.

Plant-based foods offer a sustainable alternative to meet the growing protein demand. Legumes are the most promising of these, as they contain relatively high concentrations of protein, low digestible starch, and dietary fiber, as well as them possibly featuring low levels of fat. Enzymatically modified legume proteins provide us with tempting perspectives in terms of enhancing foods' biological values. However, their bioavailability and digestibility are generally less sufficient than that of proteins of animal origin, which may be improved by well-tailored enzyme modification. In this study, the efficacy of three plant-based proteases (bromelain, ficin, and papain) were evaluated at two distinct concentrations (2.5% and 10%) and three hydrolysis durations (1, 2, and 12 h) when transforming chickpea and lentil proteins. The degree of hydrolysis (DH), peptide profiles, and free amino acid content were analyzed to determine the efficiency of each enzyme. Results showed significant variations in DH, which was influenced by enzyme type, concentration, and hydrolysis duration. Papain exhibited the highest DH, particularly at a 10% concentration, reaching 27.8% efficiency in chickpea and 34.8% in lentils after 12 h. Bromelain and ficin were proven to be less effective, with ficin showing the least hydrolytic activity. SDS-PAGE analysis revealed substantial protein degradation, especially subsequent to papain treatment, pointing out that most proteins were cleaved into smaller peptides. SEC-HPLC indicated a predominant release of peptides within the 200-1000 Da range, suggesting enhanced bioavailability. Papain and bromelain treatments resulted in a significant release of oligopeptides and dipeptides. UHPLC analysis highlighted a marked post-hydrolysis increase in total free amino acids, with arginine, leucine, and lysine being the most abundant ones. Notably, tryptophan, being undetectable in untreated samples, was released in measurable amounts post-hydrolysis. These findings demonstrate papain's superior performance in protein hydrolysis and its potential in producing bioactive peptides, highlighting its applicability in food processing and the development of both nutraceuticals and functional foods.

Comprehensive analysis of bacterial succession and flavor components in Xiguajiang with different watermelon juice supplementation during fermentation

This study investigated the physicochemical factors, bacterial communities, and volatile aromatic components in watermelon soybean pastes (WSP) prepared with different ratios of different watermelon juice to koji during the fermentation process. The results indicated that high concentration of watermelon juice could significantly increase the contents of amino acid nitrogen, reducing sugar, and free amino acids, but decreased bacterial diversity. Enterococcus, Bacillus, Enterobacter, Staphylococcus, Pediococcus, Lactobacillus, and Weissella were identified as the dominant genus bacteria in WSP samples, while Enterococcus and Pediococcus were found to account for more than 50% in WSP-4 samples. In WSP samples, this study identified 142 volatile components, the concentration of volatile components was more abundant in WSP-4 samples compared to WSP-2 and WSP-3 samples, especially in the pyrazine family. Furthermore, E-nose results showed that the influence of watermelon juice on the aroma components of WSP samples was mainly focused on the late fermentation periods, but aroma profiles were relatively similar in all WSP samples regardless of watermelon juice concentration throughout the fermentation period. Therefore, this study discovered that controlling the amount of watermelon juice and fermentation time can affect the aroma profiles of WSP samples to a certain extent, and improve the industrial production and food quality.

Dextran-enriched pea-based ingredient from a combined enzymatic and fermentative bioprocessing. Design of an innovative plant-based spread.

In this study a plant-based spread was developed using dextran-enriched ingredients derived from pea flours, supplemented with defatted durum wheat germ and almond flour. Optimization of fermentation with Leuconostoc pseudomesenteroides DSM 20193, both with and without enzymatic hydrolysis, aimed to enhance exopolysaccharide production and the nutritional value of pea flours. Best results were achieved through enzymatic hydrolysis with Veron PS protease followed by fermentation at 25°C, resulting in elevated dextran levels and increased peptides and total free amino acid concentration in green and yellow pea-based ingredients. The yellow pea-based ingredient was selected for the final plant-based spread formulation, blended at 35% w/w, with 45% w/w defatted durum wheat germ, and 20% w/w almond flour. The resultant spread exhibited elastic and solid-like characteristics like milk-based spreadable cheese and yogurt, boasting 'high protein' (12.49 g/100g) and 'high fiber' (11.01 g/100g) designations. It maintained chemical, biochemical, and microbiological stability over a 10-day shelf-life under refrigerated conditions. Sensory evaluation confirmed the acceptability of the plant-based spread (PBS), highlighting a well-balanced aroma and a grainy, adhesive texture. This research underscores the potential of an integrated approach utilizing food-grade enzymes and fermentation for the in-situ production of dextran to create innovative, clean label, and plant-based foods.

Queen Bee Larva, an Edible By-Product of Royal Jelly, Alleviate D-Galactose-Induced Aging in Mouse by Regulating Gut Microbiota Structure and Amino Acid Metabolism

Queen bee larva (QBL), as a by-product of royal jelly, is a kind of protein-rich edible insect. However, the development and utilization of QBL have been very limited for an extended period, resulting in considerable economic waste. Notably, QBL has substantial potential for anti-aging treatments; however, systematic studies have been scarce. The present study aimed to analyze the effects of freeze-dried QBL powder (QBLP) treatment in a D-galactose (D-gal)-induced-aging mouse and to explore the mechanisms. A behavioral test indicated that QBLP-treated mice had improved cognitive function and memory decline caused by aging compared to untreated aged mice. Furthermore, QBLP treatment improved organ index in aged mice and prevented pathological damage to the brain tissue. Concomitantly, treatment of D-gal-induced-aging mice with QBLP significantly reduced the oxidative damage of serum and increased the skin moisture content of aging mice. Finally, integrated analyses of the gut microbiota and the serum metabolome showed that QBLP supplementation altered the composition of the gut microbiota, enriched biochemical pathways associated with amino acid metabolism, and adjusted serum concentrations of beneficial free amino acids. Overall, QBLP can improve symptoms related to D-gal-induced aging in mice by regulating gut microbiota structure and amino acid metabolism.

Impact and correlation of fermentation temperature on the bacterial community, flavor characteristics, and proteolysis of Harbin dry sausages

Proteins undergo degradation to produce peptides and free amino acids, which in turn promote the production of volatile compounds with important contributions to the taste and aroma. This study investigated the effect of fermentation temperatures (8, 15, and 25 °C) on the bacterial community, flavor profile, and protein degradation of Harbin dry sausages. The physical and chemical properties were improved at 25 °C compared with 8 and 15 °C. Staphylococcus xylosus increased with the increase in fermentation temperature, whereas Latilactobacillus sakei decreased. The degree of protein degradation increased, and the content and proportion of taste peptides and free amino acids increased. Similarly, a higher fermentation temperature led to an increase in volatile compounds, such as aldehydes, alcohols, and esters. In conclusion, there is an inseparable relationship between proteolysis and microbial proteases. The fermentation temperature of 25 °C best contributed to the sensory quality and flavor characteristics of Harbin dry sausages.

Effect of Dietary Digestible Protein Levels on Muscle Growth and Oxidative Stress in Amazonian Pintado (Pseudoplatystoma reticulatum × Leiarius marmoratus).

This study aimed to evaluate the effects of dietary digestible protein levels on the growth dynamics and oxidative stress status of white muscle fibers in Amazonian Pintado (Pseudoplatystoma reticulatum × Leiarius marmoratus). Four hundred and fifty-five juveniles of Amazonian Pintado were fed diets containing varying digestible protein levels (225, 250, 275, 300, 325, 350, or 375 g kg-1) for 75 days. At the end of the experiment, the fish were fasted for 24 h, anesthetized, and euthanized to obtain muscle samples. The linear and quadratic effects of dietary digestible protein levels on white muscle fiber diameter, metabolite concentrations, and oxidative stress were assessed. The results revealed that increasing dietary digestible protein levels linearly raised the concentrations of free amino acids and total proteins in muscle tissue but also led to elevated levels of TBARS, indicating increased oxidative stress. Notably, the average area of muscle fibers with a cell area greater than 1133 µm2 decreased, reflecting restricted muscle hypertrophy, whereas glycogen and glucose levels also declined. These findings suggest that although high dietary digestible protein enhances protein and free amino acid concentrations in muscle tissue, it may compromise muscle hypertrophy and increase oxidative damage in Amazonian Pintado, underscoring the complexity of optimizing diet formulation.

Enhanced antioxidant activities, polyphenols, flavonoids, and free amino acid contents of Nelumbo nucifera bee pollen via high hydrostatic pressure treatment

ABSTRACT The aim of the present study was to address the effect of high hydrostatic pressure (HHP) on bioactive compounds and antioxidant activity of Nelumbo nucifera (Lotus) bee pollen (LBP). The total phenolic contents (TPC) and free amino acids were determined and flavonoid composition was identified by UPLC-Triple-TOF-MS. Five analytical methods including DPPH, ABTS, reducing power, FRAP, and silver nanoparticles antioxidant capacity were used for the antioxidant activity analysis. The results revealed a significant increase in the TPC and free amino acid compositions after HHP treatment. The DPPH, ABTS, reducing power, FRAP, and AgNPAC of the extracted fractions were augmented by over 13.94, 2.9, 2.68, 85, and 2.6 times, respectively. PCA analysis showed a strong correlation between TPC, some distinct flavonoids, and antioxidant activities. These results indicated that HHP enhances the antioxidant activity of LBP via increase in amino acids, TPC, and some flavonoids such as Licoagrone, Kuwanon K, Cyanidin 3-rutinoside, etc.

Okra (Abelmoschus esculentus L.) Flour Integration in Wheat-Based Sourdough: Effect on Nutritional and Technological Quality of Bread.

The aim of this study was to develop an innovative sourdough using dehydrated okra (Abelmoschus esculentus L.) pod flour and to use it in the production of bread. Three different flours (sun-dried S, freeze-dried F, oven-dried O) were individually mixed at 9% with wheat flour (Dough Yield 300) and fermented (N0: 8.0 log10 CFU/g) for 14 h, using Lactiplantibacillus plantarum ITM21B, Weissella cibaria C43-11 or Leuconostoc mesenteroides C43-2M. The results showed that after fermentation, the content of organic acids (lactic, acetic and propionic), exopolysaccharides (EPS), l-glutamic acid and total free amino acids (TFAA) increased and the high molecular weight proteins were converted into smaller proteins. Sourdough based on Leuc. mesenteroides and O flour (O_LeuMes) was selected to evaluate its applicability in bread making. It was included in the yeast-leavened bread formulation at 20 or 40% (0.6% and 1.21% w/w O flour replacement). The results showed that fermentation limited the negative effects of unfermented O flour on bread quality attributes, mainly the specific volume and firmness. Bread with O_LeuMes at 40% was improved in TFAA, EPS and l-glutamic acid content and showed a higher specific volume and lower moisture and firmness compared to bread with the unfermented O flour.

Replacement of fish meal with defatted black soldier fly (Hermetia illucens) in diet of Pacific white shrimp (Litopenaeus vannamei): growth, flesh quality and transcriptome

Abstract This study evaluated the impacts of replacing fish meal (FM) with defatted black soldier fly (Hermetia illucens; BSF) on the growth performance, flesh quality and transcriptome of Pacific white shrimp (Litopenaeus vannamei). In a diet containing 560 g/kg FM, BSF was used to replace 0%, 20%, 40%, 60%, 80% and 100% of dietary FM (BSF0, BSF20, BSF40, BSF60, BSF80 and BSF100). Thus, six isonitrogenous and isolipidic diets were prepared, and then fed to juvenile Pacific white shrimp (1.70 ± 0.10 g) for 60 days. In growth performance, the BSF20 group showed the similar FCR and WGR to the control group (), and the other four BSF groups presented significantly lower WGR and higher FCR than the BSF0 group (). The flesh chewiness and the contents of crude lipid, collagen and total amino acid in flesh were significantly decreased (), and flesh cooking loss, thawing loss was significantly increased when the replaced FM was ≥40% (). When the replaced FM reached 60%, the flesh hardness, heat-insoluble collagen content, shear force, body surface redness and the ratio of n-3/n-6 fatty acids were significantly lower (), while n-6 polyunsaturated fatty acid content and total free amino acid content in flesh were significantly higher than those of the BSF0 group (). Hepopancreatic samples were used for transcriptomic analysis, and a total of 1,456 differentially expressed genes (DEGs) were identified between the BSF groups and BSF0 group, which were mainly involved in growth-promoting, energy metabolism and antioxidant capacity key pathways and genes, including the cathepsin L, folate synthesis pathway, redox-related genes and glutathione metabolism pathway. In conclusion, in a diet containing 560 g/kg FM, BSF could successfully replace 20% of dietary FM, and higher FM replacement (≥40%) decreased the growth performance and flesh quality of Pacific white shrimp.

Application of Pyroligneous Acid as a Plant Growth Stimulant Can Improve the Nutritional Value of Soybean Seed

Farmers today are using biochemical treatments to improve their crop yields. Commercialized organic biostimulants exist in the form of pyroligneous acid generated by burning agricultural waste products. During the 2023 growing season, we demonstrated that soil treatment with a commercial pyroligneous acid product, Coriphol™, manufactured by Corigin Solutions, Inc., stimulated plant growth and significantly improved yield with an optimal treatment dose of 2 gal. acre−1. In the present work, we examined the effect of this treatment on soybean nutritional content using seed harvested from the 2023 season. Total mean seed protein content for untreated control plants was 32.26 ± 0.49% of dry mass and increased 10.8% to 35.64 ± 0.64% with treatment. This increase resulted in a net reduction in total free amino acid content, although levels of the essential dietary amino acid, lysine, were boosted 6-fold. Total lipid content was unaffected by treatment with mean levels of 21.61 ± 0.70% of dry mass noted. Treatment, however, reduced saturated fatty acid content by roughly 40%, and reduced the polyunsaturated content of linoleic acid in favor of the monounsaturated fatty acid, oleic acid. Finally, Coriphol™ treatment did not impact seed content of eight essential micronutrients including Na, Mg, K, Ca, Fe, Ni, Cu, and Mo, but did significantly boost Zn and Mn levels. Altogether, these results demonstrate that soil treatment with the growth stimulant Coriphol™ has the potential to improve the dietary nutritional value of soybean.

Biological conversion of red garlic (Allium sativum L) protein to bioactive peptides: ACE- DPP-IV inhibitory, and Techno-functional features

This study explores the impact of enzymolysis on the free amino acid content, techno-functional properties, free-radical scavenging, ACE, DPP-IV inhibition, iron-ion chelation and TBARS production in O/W emulsion stabilized with red garlic protein (RGP) and hydrolysates (RGPHs). The research reveals that enzymolysis time and pH significantly influence the amino acid content (antioxidant, hydrophobic, and essential ones), functional and biological quality of RGP/RGPHs. The study demonstrates that enzymolysis positively correlates with solubility (up to 90 %), health-promoting and antioxidant characteristics like DPPH (74.2 %), ABTS (81.3 %), OH (63.4 %), Reducing power (1.1 Abs700), NO (59.5 %), TAA (1.4 Abs695), ACE (71.9 %), DPP-IV (51.5 %) inhibitory, Fe2+ chelating (46.8 %) activity, and leading to reduced water/oil holding capacities, TBARS (from 0.61 to 0.38) value and lipid oxidation. However, extensive enzymatic hydrolysis (over 90 min) reduced emulsion and foaming abilities. On the other hand, the techno-functional properties of RGP and RGPHs exhibited a significant decline near the isoelectric point. This enhancement suggests that RGP could be used as a natural antioxidant with potential health benefits (antihypertensive and antidiabetic) in food and pharmaceutical formulations.

The effect of packaging material and adjunct culture on the biogenic amine content, microbiological and textural properties of Dutch-type cheese

The aim of the study was to assess the effects of the packaging materials applied (shrink foil, copolymer coating and food wax) in combination with Lacticaseibacillus casei CCDM 198 microbial strain on biochemical, microbiological and textural properties of Dutch-type cheese during ripening (at 12 ± 1 °C for 168 days). A multivariate principal component analysis method based on a correlation matrix was employed to evaluate the relationships between basic chemical properties, textural and microbiological parameters, biogenic amine and free amino acid contents in relation to the packaging material used and the length of the ripening time. The use of different packaging materials did not have a significant effect on the salt content, fat content, and pH values, whereas significant differences were observed for dry matter content and textural properties development. The presence of Lacticaseibacillus casei CCDM 198 strain accelerated proteolysis in all samples. Shrink foil and food wax had similar effects on the development of biogenic amine content during ripening, while considerable differences were observed for the samples wrapped in copolymer coating. Copolymer coating in combination with Lacticaseibacillus casei CCDM 198 strain was able to reduce biogenic amine content by up to 28% after 168 days.

Developmental-specific regulation promotes the free amino acids accumulation in chlorotic tea plants (Camellia sinensis)

Chlorophyll-deficient tea plant exhibits a significantly higher accumulation of free amino acids (FAAs) than normal tea plants. This study focused on the impact of leaf color and the developmental stage on FAAs in six tea germplasms while maintaining all other conditions. The total FAAs content initially increased as the leaf matured during the one-bud-two-leaves (1B2L) and one-bud-three-leaves (1B3L) stages in green germplasms, then decreased or stabilized in the one-bud-four-leaves (1B4L) stage. In contrast, chlorotic germplasms showed continuous FAAs’ content increase from 1B2L to 1B4L, thus being significantly positively correlated with total chlorophyll content. Interestingly, ethylamine content decreased with leaf maturation in both chlorotic and green germplasms, thus showing a significant negative correlation with L-theanine content only in chlorotic germplasms. Comparative RNA-seq analysis linked FAAs accumulation in chlorotic germplasm’s 1B3L to photosynthesis inhibition and in 1B4L to nitrogen assimilation promotion. Feeding experiments revealed higher L-theanine synthesis and degradation abilities in chlorotic shoots versus green shoots, with synthesis efficiency exceeding degradation efficiency. Overall, this study uncovers a developmental-specific FAAs accumulation pattern in chlorotic germplasms and offers novel insights into the precise regulation by leaf color and developmental stage.

Drying-induced metabolic changes in daylily: A comprehensive analysis of VOC profiles and antidepressant compounds

Daylilies are mellow-colored edible items with significant medicinal value. This study systematically evaluates the changes in the morphology and texture of daylily buds (DLB) dried by three different techniques (vacuum freeze-drying (FD), vacuum drying (VD), and hot-air drying (HD)). FD-DLB retain a more complete microstructure appearance with brighter colors and a better rehydration ability than VD-DLB or HD-DLB. According to the results of electronic-tongue and free amino acid content analyses of nutritional components, FD-DLB retain the freshness, taste, and nutritional value of DLB more than HD-DLB and VD-DLB. GC–IMS detected 28 differential metabolites; among them, the VD-DLB samples contain a relatively high content of 24 volatile components such as methyl hexanoate-D. LC–MS indicates that FD enables the retention of a high level of certain flavonoid components with strong antidepressant activity such as hyperoside, rutin, quercetin. The results of this study confirm that the FD method, which enables a better retention of nutritional and antidepressant active ingredients in DLB samples, exhibits promising potential for industrial application as a drying technology for the manufacture of DLB samples with dual-use value as medicine and food. Therefore, this study contributes significantly to guide future research on optimal methods for the treatment of functional foods.

The effect of adding Gracilaria on flavor and quality of low-salt fermented soy sauce

With the increasing awareness of health, there are higher expectations of customers for the unique flavor, umami, and nutritional value of soy sauce. To explore the potential application of edible seaweed in soy sauce, this study utilized high nutritional value seaweeds to ferment soy sauce and investigated the effects of the addition of Gracilaria on the physicochemical properties and flavor substances of soy sauce. The contents of amino acid nitrogen and total nitrogen in Gracilaria soy sauce were 0.8 g/100g and 1.4 g/100g, respectively, which were higher than those in traditional soy sauce. The free amino acid content of Gracilaria soy sauce (17.82 mg/g) was 1.35 times higher than that of traditional soy sauce, the organic acids content of Gracilaria soy sauce (15.78 mg/mL) was 1.12 times higher than that of traditional soy sauce. Compared with traditional soy sauce, the addition of Gracilaria promoted the accumulation of pyrazines and acids in soy sauce, which contributed to the seafood-like flavor. In general, the addition of Gracilaria to ferment soy sauce can improve the quality and give it a unique flavor. This study can provide a reference for improving the quality and flavor diversity of soy sauce by using seaweed as a fermentation substrate.

Analysis of free amino acids and evaluation of the quality of gallnut honeys from different geographical areas

AbstractGallnut honey, a typical Chinese medicinal commodity, is produced from the nectar of Rhus chinensis Mill. Gallnut honey is very popular with consumers because of its health effects and nutritional value, but its specific nutritional composition and medicinal components are not clear. Free amino acids are important nutritional components of honey, and can provide relevant information about the honey, such as geographical and botanical origin, as well as adulterations. The aim of this paper was to explore the free amino acid characteristics of gallnut honeys in different areas. 18 free amino acids from 17 places in China were determined by automatic amino acid analyser analysis, and the geographical characteristics were studied by principal component analysis and cluster analysis. Results showed that gallnut honey is rich in free amino acids. A total of 12 types of free amino acids were detected in all honey-producing areas, and the total amino acid content was 0.132–0.292 g/100 g. Due to its free amino acid content gallnut honey has high nutritional supplement potential, and exhibits good pharmacodynamic activity and special taste characteristics. Flavour-related free amino acids were primarily aromatic free amino acids and umami free amino acids. Pharmacodynamic free amino acids accounted for 61.22–83.85%. Results also showed that free amino acids contribute to the geographical tracing of honey, and samples of gallnut honey at different altitudes can be distinguished by cluster analysis.

Effects of Variable-Temperature Roasting on the Flavor Compounds of Xinjiang Tannur-Roasted Mutton.

This study investigates the effect of variable-temperature roasting on the flavor compounds of Xinjiang tannur-roasted mutton. Gas chromatography coupled with ion mobility spectroscopy (GC-IMS) was used to compare and analyze the volatile components and flavor fingerprints of Xinjiang tannur-roasted mutton using variable-temperature electrically heated air roasting (VTR), constant-temperature electrically heated air roasting (EHAR), and constant-burning charcoal roasting (BCR) techniques. The changes in fatty acids and free amino acids in Xinjiang tannur-roasted mutton under different roasting conditions were compared. By using GC-IMS analysis, 11 flavor compounds, including 4-methyl-3-penten-2-one, isoamyl propionate, trans-2-heptenal, trans-2-heptenal, 2-hexanone, n-hexanol, 2-hexenal, 2-ethylfuran, and ethyl 2-methylbutanoate, were identified as characteristic volatile compounds in the temperature-controlled electrothermal roasting of Xinjiang tannur-roasted mutton using the following conditions: 0-4 min, 300 °C; 5-10 min, 220 °C; and 11-17 min, 130 °C (VTR3). Through principal component analysis, it was found that the substances with the highest positive correlation with PC1 and PC2 were n-hexanol and 3-methylbutanol. The sensory evaluation showed that VTR3 had high acceptability (p < 0.05) and a fat flavor (p < 0.05). There was no significant difference in the total fatty acid (TFA) content between the VTR3 and burning charcoal roast for 1-17 min at 300 °C (BCR3) (p > 0.05), but it was lower than that in the other experimental groups (p < 0.05). The lowest proportion of glutamic acid content in VTR3 was 22.44%, and the total free amino acid content in the electric thermostatic roasting for the 1-17 min, 300 °C (EHAR3) group (347.05 mg/100 g) was significantly higher than that in the other experimental groups (p < 0.05). By using Spearman correlation analysis, the roasting loss rate showed a highly significant negative correlation with essential amino acids (EAAs), non-essential amino acids (NEAAs), and total free amino acids (TAAs) (the correlation coefficients (r) were 0.82, 0.87, and 0.87, respectively) with p < 0.01. There was no correlation between changes in the free amino acid content and fatty acid content (p > 0.05). By using Differential scanning calorimetry (DSC) analysis, we also found that there was no significant difference in peak temperature (Tp) between the VTR3 and EHAR experimental groups (p > 0.05). Variable temperature electric heating can affect the flavor of lamb, and there are significant differences in the content of flavor precursors such as fatty acids and amino acids in Xinjiang tannur-roasted mutton.

Changes of physicochemical and volatile flavor compounds of dry-cured Diqing Tibetan pig hams during fermentation

This study aimed to explore the flavor formation mechanism of Diqing Tibetan pig hams by investigating changes of their physicochemical and volatile flavor compounds during fermentation (0, 30, 90, 180, 360, and 540d) using amino acid analyzer , texture profile analysis, and gas chromatography-ion mobility spectroscopy (GC-IMS). During fermentation, the hams significantly decreased in moisture and centrifugal loss, while increased in chewiness, hardness, and proteolysis index, with their free amino acids content reaching the maximum at 360d and significantly decreasing at 540d. GC-IMS identified 78 volatile organic compounds, with the highest total content of alcohols and aldehydes at 180d, ketones and heterocycles at 360d, and esters at 540d. PLS-DA screened 24 volatile flavor markers, with aldehyde (2-methyl-2-propenal), ketone (2-heptanone-D), alcohol (3-methylbutanol-D), ester (ethyl3-methylbutanoate-M), and heterocyclic substances (2,3-dimethylpyrazine-M) as the main VFMs at 360d. The unique flavor of 540d Diqing Tibetan pig hams was attributed to their higher content of 3-methyl-2-butenal, 3-(methylthio) propanal, ethyl caproate and 2-butanone. These findings provide a scientific basis for the flavor formation mechanism of hams which favoring the further development processing strategies for Diqing Tibetan pig.

Effect of copper on nitrogen uptake, transportation, assimilation processes, and related gene expression in Chinese cabbage [Brassica campestris L. ssp. Chinensis (L.)] under various nitrate-to-ammonium ratios.

Improving vegetable yield and optimizing its quality through nutrient management have long been central to plant nutrition and horticultural science. Copper (Cu) is recognized as an essential trace element that promotes plant growth and development. However, the mechanisms by which Cu influences nitrogen (N) metabolism remain largely unknown, with limited studies exploring the interaction between Cu and varying nitrate-to-ammonium (nitrate/ammonium) ratios. In this study, Chinese cabbage was exposed to two Cu concentrations (0 and 0.02 mg L-1) in combination with three nitrate/ammonium ratios (10/90, 50/50, and 90/10) under hydroponic conditions. The results showed that Cu application increased plant biomass, nitrate reductase (NR) and glutamine synthetase (GS) enzyme activities, the expression of NR (NIA) and GS2 (Gln2) genes, and N content in both shoots and roots. Additionally, Cu treatment decreased nitrate and free amino acid contents, as well as the expression of nitrate transporters NRT1.1 and NRT2.1 in roots while increasing these four parameters in shoots. Additionally, these effects were significantly modulated by the nitrate/ammonium ratios. In conclusion, Cu may facilitate nitrate transportation, enhance nitrate reduction, promote ammonium assimilation, and influence the transformation of organic N compounds, highlighting its potential role in improving N metabolism in Chinese cabbage.