Amino Nitrogen Content Research Articles

Study of the jellyfish Rhizostoma pulmo hydrolysis and characterization of the obtained product

The purpose of this work is to develop technological parameters for the hydrolysis of barrel jellyfish Rhizostoma pulmo involving the use of enzymatic agents «Enzy-mix» and alcalase, available through the domestic market, as well as to investigate the amino acid and mineral composition of the resultant hydrolysate.Methods used: the process of hydrolysis has been assessed based on the changes in peptide concentrations in the hydrolysate, the content of amino nitrogen, and the degree of hydrolysis. To investigate its chemical, amino acid, and mineral composition, the standard methods were used. Novelty: the use of jellyfish for hydrolysis after its thawing and the hydrolysis procedure not involving the addition of water into the raw material subjected to hydrolysis present a novel approach.Result: the optimal regime for hydrolysis of barrel jellyfish Rh. pulmo after its thawing has been identified, which was characterized by the use of 1% alcalase at the temperature 55±2 °C and duration of 1 h. It has been shown that alcalase is more effective in terms of amino nitrogen accumulation than enzymatic agent «Enzy-mix». The values of amino nitrogen after 1 h of hydrolysis involving the use of 1% alcalase were higher than the values of the same parameter obtained during the 3-hour hydrolysis involving 1.5% «Enzy-mix» at the temperature 40±2 °C. The hydrolysate, after its concentration to the dry matter exceeding 30%, contains no less than 15.1±0.59% of protein represented by 48% of essential amino acids, out of which leucine and isoleucine prevail (15 %). Among non-essential amino acids, the most prominent was glycine (17 %). For all essential amino acids, except for valine, the amino acid score exceeds 100%. In humans, consumption of around 20 g of the hydrolysate covers the daily physiological requirement of magnesium.Practical significance: the obtained data on the amino acid profile and mineral composition of the barrel jellyfish Rh. pulmo hydrolysate provide the basis for its consideration as a promising ingredient for the functional nutrition products.

Effect of inoculating Lactiplantibacillus plantarum Y279 on bacterial community structure and quality of fermented Yujiaosuan

The unique flavor and extended shelf life were identified as essential characteristics of Yu jiaosuan (YJS), while challenges of fermentation control and poor stability were noted to have hindered its industrialization. The effects of Y279 inoculation on the bacterial community structure and quality improvement of YJS were investigated in this study. The results showed that after fermentation with Y279, the total acidity and amino nitrogen concentration of YJS were increased by 0.40 g/kg and 18.45 mg/100 g, respectively, while the pH, TBARS value, and nitrite content were significantly decreased by 0.28, 0.2, and 0.0048 mg/kg, respectively. High-throughput sequencing confirmed that Lactobacillus and Weissella were the dominant genera in the inoculated fermentation group. Forty-five differential metabolites were identified, involving three tastant-related pathways: arginine and proline metabolism, arginine biosynthesis, and purine metabolism. Additionally, molecular docking revealed substances in these differential metabolites that were bound to taste receptors via traditional hydrogen and carbon-hydrogen bonds. The results of sensory evaluation showed that the umami and sourness taste and color of the inoculated fermentation group were enhanced.This study offers theoretical guidance for the use of fermentation agents to improve YJS quality.

Comparative analysis of bacterial community structure and physicochemical quality in high-temperature Daqu of different colors in Qingzhou production area

To compare the effects of differences in Daqu making technology and production regions on the bacterial composition and physicochemical properties of high-temperature Daqu (HTD), this study analyzed the bacterial community structure of three colors of HTD in the Qingzhou production area and measured their physicochemical quality. At the same time, a comparative analysis was conducted on the bacterial composition of Qingzhou and Xiangyang regions. The results revealed that the HTD in the Qingzhou area exhibited a diverse bacterial community dominated by Lentibacillus, Scopulibacillus, and Staphylococcus. The black HTD displayed the lowest bacterial richness (P < 0.05) and a relatively unique microbial structure. Significant variations were observed in the physicochemical qualities of the three colors of HTD. Notably, white HTD demonstrated higher moisture and ash content, saccharification and liquor-producing power. Yellow HTD exhibited higher amino nitrogen and protein content, and black HTD displayed higher water activity, acidity, and starch content. The variation in Bacillus, Limosilactobacillus, and Weissella distributions across different colors of HTD primarily contributed to these findings. From the HTD samples in the Qingzhou area, Bacillus (61.90 %) and lactic acid bacteria (17.46 %) being the predominant cultivable communities. Cluster analysis identified significant differences in bacterial communities among HTD samples from various production areas. It can enhance the understanding of HTD quality in the Qingzhou area and offer insights for optimizing HTD and Maotai-flavor Baijiu quality.

Comprehensive Review of the Potential of Sorghum in Malt and Beer Production

Sorghum has a relatively lower price compared to other brewing cereals, and consequently has potential as an alternative substrate for lager beer brewing and especially represents an excellent option for gluten-free beers. Attributes such as extracts, proteins, total nitrogen and free amino nitrogen content of sorghum malt and the wort obtained from mashes indicate that sorghum is potentially an alternative substrate for conventional beer brewing in the tropics. In alcohol industry, some distillers prefer sorghum varieties with high starch and less protein contents. The variation in biochemical compositions among sorghum varieties affects the optimal malting conditions and characteristics of the grains. The degree of steeping and temperature, and germination capacity, kilning temperature and the intrinsic enzyme activity determine sorghum grain malt quality. The high degree of gelatinization temperature, poor saccarification, lower fermentability and filterability of sorghum malt could generally affects the acceptability of sorghum beer by the consumer than a beer brewed from malt barley.

Dose-dependent alteration in hepatic and cerebral glucose metabolism following exposure to polystyrene microplastic in Wistar rats

Background: Recently, microplastics (MPs) with dimensions less than 5 mm have gained more attention due to their adverse impact on the environment and living creatures. Polystyrene (PS) particle is a key element of primary microplastics, which are causing numerous health issues such as interruption of energy metabolism, oxidative stress, neurotoxicity, immunotoxicity, digestive gland disorders, reproductive disruption, and genotoxicity in marine living organisms. Method: Alteration in carbohydrate metabolism was evaluated in male Wistar rats (six weeks of age) after four weeks of oral exposure to polystyrene microplastic (PS-MP) at three different doses (0.5mg/L, 5mg/L and 50 mg/L via drinking water). Results: Polystyrene exposure caused a significant decrease in blood glucose, liver glycogen, and pyruvic acid content in liver and cerebral tissue. Free amino nitrogen content significantly altered in the liver and cerebrum in a dose-specific manner. The LDH activity was found to be decreased in the liver, whereas it increased in the cerebral cortex of rats in a dose-responsive fashion. Enzymes like glucose 6-phosphatase, GOT, GPT, and succinate dehydrogenase activities demonstrated differential effects on the liver and cerebrum of rats in terms of energy metabolism. Conclusion: It is suggested that sub-acute polystyrene exposure significantly perturbs glucose metabolism by inducing hypoglycemia associated with decreased glycolysis and increased TCA cycle enzyme function in rat liver in a dose-dependent manner. Gluconeogenesis is also affected differentially by metabolic adjustment in the studied organs.

Exploring the role of production and release of proteins for microbial interactions in kombucha

Driving kombucha fermentation through microbial consortia remains based on scarce scientific elements, especially regarding the consumption of nitrogenous nutrients. This study aimed at analyzing quantitatively proteins and free amino nitrogen (FAN) concentrations, and qualitatively the soluble proteins profiles during a 12-day production process. The effect of microbial interactions was evaluated by comparing the growth of previously isolated major microorganisms in monoculture and cocultures to original kombucha. Protein and FAN relative concentrations kinetics depended on microbial compositions. These parameters were associated to less variations and a positive effect on total microbial population in original kombucha, underlining a complex yet better management of the nutrients. Analysis of extracellular proteins by electrophoresis showed the presence of a microbial 15 kDa fraction common to all cultures. In contrast, a 21 kDa protein fraction was associated with the presence of Acetobacter indonesiensis. Exploratory proteomics analysis revealed the presence of characteristic extracellular moonlighting proteins, originating from this acetic bacteria. Production of extracellular vesicles was successfully confirmed with the isolation and observation of vesicles in A. indonesiensis culture, as well as in kombucha. The results characterize the central role of microbial interactions on FAN consumption and open new perspectives on the function of the bacterial vesicles observed.

Impact of pulsed electric field treatment on barley germination for malting

The malting process takes one week to steep, germinate, and kiln barley to make malt. Making quality malt is critically important to achieve the desired attributes of the finished beer, and the process is time-intensive and costly. Malt quality is assessed by indicators including β-glucan quantity, α-amylase activity, Free Amino Nitrogen (FAN) content, and overall extract concentration in the finished malt. Here, we report Pulsed Electric Field (PEF) treatment of barley to accelerate malt production. A small-scale trial of 250 g to 1.00 kg barley, was evaluated for germination at two PEF treatment conditions, generically referred to as “low” and “high”, that resulted in increased barley rootlet length during germination of 1.3 mm longer than was observed for the control. Large-scale trials of 1.00 kg–3.00 kg barley, resulted in an increase in germination rate and a decrease of β-glucan concentration in the PEF treated barley. Micromalted barley using PEF parameters of 1.0 kV/cm and 15.0 kJ/kg displayed a reduction in β-glucan concentration by 38%, and increase in malt extract by 1.5%, FAN by 6.2%, and α-amylase by 8.4%, supporting the hypothesis that PEF treated barley generates more and better malt, leading to greater efficiency in the beer making process.

Enhanced sporulation of B. licheniformis BF-002 through automatic co-feeding of carbon and nitrogen sources.

Bacillus licheniformis formulations are effective for environmental remediation, gut microbiota modulation, and soil improvement. An adequate spore quantity is crucial for the activity of B. licheniformis formulations. This study investigated the synergistic effects of carbon/nitrogen source consumption and concentration on B. licheniformis BF-002 cultivation, with the aim of developing an automatic co-feeding strategy to enhance spore production. Initial glucose (10 g/L) and amino nitrogen (1.5 g/L) concentrations promote cell growth, followed by reduced glucose (2.0 g/L) and amino nitrogen (0.5 g/L) concentrations for sustained spore generation. The spore quantity reached 2.59 × 1010 CFU/mL. An automatic co-feeding strategy was developed and implemented in 5 and 50 L cultivations, resulting in spore quantities of 2.35 × 1010 and 2.86 × 1010 CFU/mL, respectively, improving by 6.81% and 30.00% compared to that with a fixed glucose concentration (10.0 g/L). The culture broth obtained at both the 5 and 50 L scales was spray-dried, resulting in bacterial powder with cell viability rates of 85.94% and 82.68%, respectively. Even after exposure to harsh conditions involving high temperature and humidity, cell viability remained at 72.80% and 69.89%, respectively. Employing the automatic co-feeding strategy increased the transcription levels of the spore formation-related genes spo0A, spoIIGA, bofA, and spoIV by 7.42%, 8.46%, 8.87%, and 9.79%, respectively. The proposed strategy effectively promoted Bacillus growth and spore formation, thereby enhancing the quality of B. licheniformis formulations.

The principal component analysis of key and significant features of the safety and nutritional value of Mahyaveh sauce.

The objective of present research is to evaluate the changes in the chemical, microbial, and biogenic amines in Persian fish sauce (Mahyaveh) during 40 days of fermentation. In the current survey, the parameters of salt percentage, pH, total nitrogen concentration, amino nitrogen concentration, Brix, color features, cadaverine, and histamine concentration were measured in the fish sauce. The amino nitrogen content, total protein, Brix, and salt were increased along with the progression of fermentation process. The microbial population of Mahyaveh sauce demonstrated that lactic acid bacteria (LAB), total bacterial count, and Enterobacteriaceae decreased during fermentation. The population of lactic acid bacteria and the total count of bacteria were around one logarithmic cycle lower in the presence of 10% salt than under low salt conditions. Histamine and cadaverine concentrations increased to 43.49 and 42.76 mg/kg during the fermentation period, respectively. As a result, the population density of histamine-producing bacteria rose from 3.00 log CFU/mL at the beginning to 4.58 log CFU/mL at the end of process. The population density of cadaverine-producing bacteria was 3.43 and 5.24 log CFU/mL on the 20th and 40th days of fermentation, respectively. Sensory evaluation results indicated that our sample of fish sauce had an overall acceptability score of 5.1 (good). On the other hand, Principal Component Analysis (PCA) demonstrated a positive correlation between the most of chemical parameters and the fermentation period. The concentration of cadaverine and histamine has a positive association with the pH and type of bacteria producing the biogenic amines.

Modeling and Optimization of Triticale Wort Production Using an Artificial Neural Network and a Genetic Algorithm.

Triticale grain, a wheat-rye hybrid, has been reported to comply very well with the requirements for modern brewing adjuncts. In this study, two triticale varieties, in both unmalted and malted forms, were investigated at various ratios in the grist, applying different mashing regimes and concentrations of the commercial enzyme Shearzyme® 500 L with the aim of evaluating their impact on wort production. In order to capture the complex relationships between the input (triticale ratio, enzyme ratio, mashing regime, and triticale variety) and output variables (wort extract content, wort viscosity, and free amino nitrogen (FAN) content in wort), the study aimed to implement the use of artificial neural networks (ANNs) to model the mashing process. Also, a genetic algorithm (GA) was integrated to minimize a specified multi-objective function, optimizing the mashing process represented by the ANN model. Among the solutions on the Pareto front, one notable set of solutions was found with objective function values of 0.0949, 0.0131, and 1.6812 for the three conflicting objectives, respectively. These values represent a trade-off that optimally balances the different aspects of the optimization problem. The optimized input variables had values of 23%, 9%, 1, and 3 for the respective input variables of triticale ratio, enzyme ratio, mashing regime, and triticale variety. The results derived from the ANN model, applying the GA-optimized input values, were 8.65% w/w for wort extract content, 1.52 mPa·s for wort viscosity, and 148.32 mg/L for FAN content in wort. Comparatively, the results conducted from the real laboratory mashing were 8.63% w/w for wort extract content, 1.51 mPa·s for wort viscosity, and 148.88 mg/L for FAN content in wort applying same input values. The presented data from the optimization process using the GA and the subsequent experimental verification on the real mashing process have demonstrated the practical applicability of the proposed approach which confirms the potential to enhance the quality and efficiency of triticale wort production.

Monitoring of optimal conditions for producing fermented black soybeans rich in sulfur-containing amino acids

The optimal fermentation conditions for producing fermented black soybeans rich in sulfur-containing amino acids were investigated. Response surface methodology monitored fermentation conditions. A central composite design examined the effect of independent variables: enzyme concentration (X1) and fermentation time (X2) on yield and methionine content. Both factors significantly influenced these dependent variables. Enzyme concentration more profoundly affected amino nitrogen content than fermentation time. β-Glucan content and cystine level were primarily affected by fermentation time. We elicited each variable’s regression formula and identified optimal fermentation conditions for functional compounds. The predicted optimum conditions were an enzyme concentration of 0.28-0.32% and a fermentation time of 58.0-62.0 min. Under these optimal conditions, each black soybean variety's sulfur amino acid content ranged from 818.62 to 922.62 mg/100 g, demonstrating significant variety differences.

Partial characterization of canola (Brassica napus L.) protein isolates as affected by extraction and purification methods

Canola (Brassica napus L.) meal represents a prominent alternative plant-based source for protein isolation. This work aimed to investigate the combined effect of extraction and purification methods for the production of canola protein isolates (CPIs). CPIs were characterized in terms of process yield, protein recovery, basic composition, amino acid profile, in vitro protein digestibility, techno-functional properties, structural properties, and molecular features. The results showed that the Alk-Uf method enhanced yield (16.23 %) and protein recovery (34.88 %). Meanwhile, the Et-Alk-Uf method exhibited the highest crude protein (89.71 %) and free amino nitrogen (4.34 mg g protein−1) contents. Furthermore, protein digestibility (95.5 %) and protein digestibility corrected amino acid score (1.0) were improved using the Et-Alk-Ac method. Conversely, the amino acid composition, secondary structure, and electrophoretic profiles were generally similar for all CPIs. The Alk-Uf and Et-Alk-Uf methods produced isolates with the highest water solubility (∼39.18 %), water absorption capacity (∼3.86 g water g protein−1), oil absorption capacity (∼2.77 g oil g protein−1), and foaming capacity (∼505.26 %). Finally, the foaming stability (93.75 %) and foaming density (34.38 %) were increased when employing the Alk-Ac method. These findings suggest that, in general, the Alk-Uf and Et-Alk-Uf methods can be used to obtain CPIs with high added value for use in food formulations.

Quantitative analysis of key components in Qingke beer brewing process by multispectral analysis combined with chemometrics

In order to monitor the Qingke beer brewing process in real time, this paper presents an analytical method for predicting the content of key components in the wort during the mashing and boiling stages using multi-spectroscopy combined with chemometrics. The results showed that the Neural Networks (NN) model based on Raman spectroscopy (RPD = 3.9727) and the NN model based on NIR spectroscopy (RPD = 5.1952) had the best prediction performance for the reducing sugar content in the mashing and boiling stages; The partial least Squares (PLS) model based on Raman spectroscopy (RPD = 2.7301) and the NN model based on Raman spectroscopy (RPD = 4.3892) predicted the content of free amino nitrogen best; The PLS model based on UV–Vis spectroscopy (RPD = 4.0412) and the NN model based on Raman spectroscopy (RPD = 4.0540) are most suitable for the quantitative analysis of total phenols. The results can be used as a guide for real-time control of wort quality in industrial production.

Engineered salt-tolerant yeast to improve the physicochemical properties and volatiles of sweet flour paste

Sweet flour paste is a traditional condiment and fermented in high brine solution (14∼18%). Aroma-producing yeast plays a crucial role in the flavor and taste of sweet flour paste, but high salt concentrations often inhibit the action of the yeast. In this study, yeast Zygosaccharomyces rouxii AS2.18 was used as the parent strain to breed a salt-tolerant aroma-producing yeast strain by a combination of atmospheric and room temperature plasma (ARTP) mutagenesis and adaptive laboratory evolution (ALE). The engineered strain AMS79 showed the good growth and fermentation capacity at 18% NaCl concentration. The salt tolerance was closely related to intracellular glycerol production, Na+K+-ATPase activity enhancement and cell wall integrity improvement of the strain. During sweet flour paste fermentation, the maximum amino nitrogen content of the AMS79 group was 1.07- and 1.11-fold higher than that of the AS2.18 group and blank group, respectively. Compared to Blank group, the inoculation of AS2.18 enhanced the relative contents of alcohols, acids, ketones and furan(one)s, and the content of all 7 volatile compound types increased when AMS79 was inoculated for fermentation. In particular, the contents of 2-methyl-butanoic acid, benzeneacetaldehyde, 5-methyl-2-phenyl-2-hexenal and furfural were significantly enhanced by the salt-tolerant strain AMS79 compared to the parent strain AS2.18.

Fruitlet Thinning Improves Juice Quality in Seven High-tannin Cider Cultivars

Over 3 years (2016–18), tree productivity, biennial bearing, return bloom, and fruit quality were evaluated for seven high-tannin cider apple (Malus ×domestica Borkh.) cultivars. Five treatments were evaluated on each of the seven cultivars: hand-thinned of all fruit (a zero crop load treatment); hand-thinned to crop densities of three, six, or nine fruit/cm2 trunk cross-sectional area (TCSA); or left unthinned. In this paper, we report on the fruit maturity and juice quality properties that were analyzed for the three nonzero crop load treatments and the unthinned control. The effects of crop load on fruit maturity, as measured by starch pattern index and preharvest drop, were cultivar dependent. Crop density (fruit/cm2 TCSA) had a significant effect on all fruit maturity and juice quality variables, although effects were weakest in the “off” year (2017) for the whole planting when initial fruit set was low. As crop density increased, total poly phenols, titratable acidity, soluble solids, and primary amino nitrogen decreased in the juice of all seven cultivars. A partial budget analysis indicated that the reduced costs of nitrogen supplements due to increased primary amino nitrogen concentration alone would not justify cost of chemical or hand-thinning. By extrapolating the spring flowering density in the fourth year to potential fruit yields at harvest, we found that reducing crop load was projected to increase cumulative total polyphenol yields per tree over the long term. For the cultivars in this experiment, a target crop density of nine fruit/cm2 was found to adequately decrease biennial bearing while also not diminishing juice quality for hard cider production. High-tannin cider apple growers should consider juice quality, particularly tannin production, when making crop load management decisions.

Changes in the content of aminonitrogen and the activity of aminotransferases in saliva in lymphomas

Background. The relevance of studying changes in the activity of metabolic enzymes in saliva in lymphomas lies in the non-invasive method of research, the search for new ways in the diagnosis of oncology to detect the disease in the early stages, as well as to obtain a complete picture of the course of the pathological process. The activity of certain biochemical enzymes is significantly higher in saliva than in blood serum. In addition, saliva is a less hazardous environment for laboratory testing than blood, which reduces the risk of infection for medical personnel. Objective. The aim of this work was to search for biochemical markers in saliva in Hodgkin’s and non-Hodgkin’s lymphomas, the value of which was statistically significantly different from the values of the same markers among healthy subjects included in the control group. Design and methods. In the case-control study, volunteers were divided into 2 groups: the main group, with a histologically confirmed diagnosis of Hodgkin’s lymphoma (53 people) or non-Hodgkin’s lymphoma (82 people) and the control group (135 people), apparently healthy individuals. Inclusion in groups occurred in parallel. All participants underwent a biochemical study of saliva to determine the content of amine nitrogen, the activity of enzymes (AlAT, AsAT, GGT, alkaline phosphatase). The patients of the main group were recruited on the basis of the Clinical Oncological Dispensary (Omsk, Russian Federation). Results. A significant increase in amino nitrogen (p &lt; 0,0084), ALT (p &lt; 0,0205), AST (p &lt; 0,0047), GGT (p&lt;0,0291) was found in the group of patients diagnosed with non-Hodgkin’s lymphoma, compared with subjects from the control group. Conclusion. A preliminary hypothesis was put forward that aminotransferases such as ALT, AST and GGT can be used not only as indicators of liver damage. A change in the activity of amine transferases with a simultaneous increase in the activity of amino nitrogen may reflect a pronounced redistribution of nitrogen in the body for the synthesis of new non-essential amino acids that are necessary for neoplastic cells as structural components for their growth and proliferation. This work also confirms that saliva is an informative diagnostic liquid that can be used in the routine practice of a clinician.

Effect of variety and malting conditions on proteolytic activity, free amino nitrogen, and soluble protein contents of two maize varieties (Atp-Y and Coca-sr): amylolytic activity and physico-chemical and functional properties of optimal sample.

The utilization of sprouted meals in beer production and enhancing the physicochemical properties of supplementary foods is widespread in Africa. This work aimed to determine the influence of soaking, germination, maturation and variety conditions on the physicochemical properties, proteolytic activity, free amino nitrogen (FAN) and soluble protein contents of Coca-sr and Atp-Y maize varieties. To achieve this, the central composite design (CCD) was used for the optimization of five parameters, namely soaking time (18-42 h), plant salt concentration (0.5-1.2%), soaking temperature (25-41°C), sprouting time (80-195 h) and ripening time (17.50-42 h), and following dependent variables were investigated: proteolytic activity, FAN content and soluble protein. Optimal samples flours obtained were then subsequently subjected to physicochemical and functional analysis. The analysis of results showed that the linear, interactive and quadratic effects of the factors significantly (p<0.05) affected the proteolytic activity, FAN and soluble protein contents of both varieties. The direction of each factor's variation and its effects were not similar in the two varieties. The optimal malting conditions were 7.31 h soaking with 1.678% vegetable salt at a temperature of 34.65°C followed by sprouting for 245.59 h and maturation for 0.765 h for the Atp-Y variety. For the Coca-sr variety, it requires 1.608 h of soaking with 1.678% vegetable salt at a temperature of 51.93°C followed by 273.94 h and 58.73 h for sprouting and ripening time respectively. The meals of Coca-sr produces using these optimal conditions showed a significantly (p<0.05) higher proteolytic activity, FAN and soluble protein content. The amylolytic activity was more pronounced in the Atp-Y variety, as was the content of essential amino acids. The above optimal conditions reduced the content of anti-nutrients (phytates, saponins, oxalates, condensed and hydrolysable tannins), improved the availability of minerals (Ca and Mg), reduced the pH, mass density, water retention capacity and swelling rate. As a result, the optimal flours of these two maize varieties could be applied in the formulation of supplementary foods, bakery products and beer by industrialists.

Flavor and quality characteristics of Guizhou red sour soup prepared by different artificially fortified fermentation methods

Red sour soup is a typical condiment in Guizhou Province, China. However, its flavor quality is often limited by its unstable traditional fermentation methods. In the study, red sour soup was prepared with three fermentation methods (split fortification, mixed fortification, and natural fermentation) and then various indicators of the prepared soup were determined. Compared with natural fermentation, two fortified fermentation methods could accelerate the pH decrease of red sour soup (on the 6th day pH = 3.36 ± 0.01 for split fortification and pH = 3.26 ± 0.06 for mixed fortification), increase the total number of lactic acid bacteria, total acid, umami value, and amino nitrogen content, and more efficiently control the content of nitrite and saltiness. Mixed fortification realized the contents of organic acids (26.776 ± 8.351 g/kg) and cis-lycopene (9.540 ± 0.559%). The contents of the key esters (methyl butyrate, hexyl acetate, etc.) and alcohols (2-ethylhexanol, 1-hexanol, etc.) in the red sour soup prepared with two fortified fermentation methods were higher than those in the red sour soup prepared with natural fermentation. The characteristic flavoring substances in the red sour soup prepared with split fortification were mainly leaf alcohol, ethyl butyrate, isoamyl acetate, and α-turnipene, whereas the characteristic flavoring substances in the red sour soup prepared with mixed fortification were mainly methyl butyrate, isobutyl acetate, hexyl acetate, and linalool oxide. The study provides the basis for the optimization of fermentation parameters and the quality control of red sour soup.

Microbial Community Succession and Its Correlation with Quality Characteristics during Gray Sufu Fermentation.

Gray sufu, a traditional fermented food derived from soybeans, undergoes a complex fermentation process. This study aimed to investigate the dynamics of the microbial community during sufu fermentation and its relationship with key quality characteristics. Through systematic sampling of sufu at different phases of fermentation, 143 bacterial genera and 84 fungal genera involved in the process were identified. Among these, Chishuiella, Enterococcus, Lactococcus, and Weissella emerged as the predominant bacterial communities. After seven days of ripening fermentation, Trichosporon supplanted Diutina as the predominant fungus, accounting for more than 84% of all fungi. Using redundancy analysis, significant correlations between microbiota and physicochemical properties were uncovered. Chishuiella and Empedobacter displayed positive relationships with pH, soluble protein, and amino nitrogen content. In addition, five biogenic amines were detected, and it was determined that tyramine accounted for more than 75% of the total biogenic amines in the final gray sufu products. Spearman correlation analysis revealed significant positive relationships between Lactococcus, Enterococcus, Tetragenococcus, Halanaerobium, and Trichosporon and the five biogenic amines examined. These findings shed light on the complex interactions between microorganisms and biogenic amines during the fermentation of gray sufu, thereby facilitating the development of microbial regulation strategies for better quality control.

Effect of fermentation with Tetragenococcus halophilus and Zygosaccharomyces rouxii on selected non-volatile taste compounds in soybean protein hydrolysates

This work was focused on investigating the effect of fermentation with Tetragenococcus halophilus and Zygosaccharomyces rouxii on the flavor characteristics of soy protein hydrolysates (SPH). The sensory attributes and non-volatile taste compounds of SPHs were analyzed using high performance liquid chromatography, electronic tongue and sensory evaluation. The results demonstrated that fermentation could effectively increase the contents of amino nitrogen, total acids, organic acids (especially lactic acid), umami amino acids (growth rate ranging from 10.9% to 30.6%) and sweet amino acids (increased by 7.8%–62.0%) compared with control groups, contributing to improve the acidity, as well as umaminess and sweetness taste of samples. Principal component analyses and partial least square discriminant analyses confirmed the substantial impacts on the non-volatile taste characteristics of SPHs by lactic acid bacteria (LAB) and yeast fermentation, especially for the flavor profile of the sample with Aspergillus oryzae hydrolysis and sequential addition of LAB and yeast (SFH-2), and the sample with commercial protease hydrolysis and simultaneous addition of LAB and yeast (SH-1). These findings provided a theoretical basis for enhancing the flavor intensity of soybean protein hydrolysates.