Increase In Fermentation Temperature Research Articles

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.

Microbial community succession in the fermentation of Qingzhuan tea at various temperatures and their correlations with the quality formation

With the aim to reveal the microbial community succession at various temperatures in the fermentation of Qingzhuan tea (QZT), the Illumina NovaSeq sequencing was carried out to analyze bacterial and fungal community structure in tea samples collected from the fermentation set at various temperatures, i.e., 25 °C, 30 °C, 37 °C, 45 °C, 55 °C, and room temperature. The results showed that fermentation temperature profoundly affected the microbial community succession in the QZT fermentation. Microbial richness and community diversity decreased along with the increase of fermentation temperature. Despite the differences between microorganisms and their metabolic types among various temperatures, most bacteria and fungi showed positive correlations at the genera level. Klebsiella, Paenibacillus, Cohnella, and Pantoea were confirmed as the main bacterial genera, and Aspergillus and Cyberlindnera were the main fungal genera in QZT fermentation. The microbial genera (i.e. Aspergillus, Rhizomucor, Thermomyces, Ralstonia, Castellaniella, and Vibrio) were positively correlated with fermentation temperature (P < 0.05), while Klebsiella, Paenibacillus, and Aspergillus had good adaptability at different temperatures. Conversely, Pantoea and Cyberlindnera were only suitable for low temperature (≤37 °C) growth, and Thermomyces was only suitable for high temperature (>37 °C) growth. Aspergillus had a significant positive correlation with tea aroma quality (r = 0.64, p < 0.05). This study would help to understand the formation mechanism of QZT from microflora perspective.

Process improvement to prevent the formation of biogenic amines during soy sauce brewing.

Biogenic amines (BAs) are a class of bioactive organics produced during the fermentation of soy sauce. A high concentration of BAs may bring about serious physiological and toxicological effects on the human body. In this study, we reported an optimized process to produce soy sauce with lower BA concentration and found the contents of putrescine, cadaverine and histamine increased with the increase of fermentation temperature but decreased with the increase of NaCl concentration. The final content of total BAs with improved fermentation was 105.56±0.13mg/L, which was reduced by 89.11% compared to traditional brewing. Besides, the pilot production test was performed to verify the optimized conditions and physicochemical indexes were measured to better understand the change principle of the chemical compounds. Taken together, we present an effective process to inhibit the formation of BAs while ensuring that characteristic nutrients are not lost.

Effect of controlled temperature on the amino acid profile and protease activity of fermented bottle gourd seed

The effect of controlled temperature on the amino-acid profile and protease activity of bottle gourd seed (BGS) as well as melon seed (MES) was studied. De-hulled seeds were boiled for 6 hours and fermented at 28oC, 35oC and 42oC for 96 hours. The amino-acid profile of raw, boiled and fermented BGS and MES were determined respectively. The protease activity of the seeds was as well determined at various stages of fermentation. The amino-acid profile of the samples showed high content of glutamic acid (152.1 to 158.8 mg/g for BGS and 145.4 to 166.7 mg/g for MES). Generally, the concentration of the respective amino-acids (essential and non-essential amino-acids) present in the seeds decreased with boiling but increased after fermentation. Fermentation was found to significantly (p&lt;0.05) affect the protease activity of the seeds. The magnitude of the effect was dependent on the seed type, fermentation time and temperature. An increase in fermentation temperature from 28 to 42oC led to an increase in the protease activity of the respective seeds (15.8 to 23.8 units/ml for BGS and 21.6 to 23.0 units/ml for MES) which invariably resulted to the increase in the concentration of the amino-acids present in the respective seeds thereby increasing the bioavailability of the proteins present in the seeds. Microorganisms isolated and identified in the fermenting mashes include; Bacillus Subtilis, Bacillus cereals, Micrococcus luteus, Staphylococcus aureus and corynebacterium sp. The results showed that fermented BGS could favourably substitute for fermented MES as a source of cheap and affordable dietary protein.

Physical adsorption of patulin by Saccharomyces cerevisiae during fermentation.

Patulin (PAT), a mycotoxin mainly produced by various species of fungi, is frequently detected in moldy fruit- and vegetable-based products, which pose a health risk to the consumer. Over the past decades, a few studies reported that PAT content could be significantly decreased by microbial fermentation process. However, the physical adsorption mechanism between PAT and yeast during fermentation is still unclear. In this paper, we focused on the physical adsorption of PAT by Saccharomyces cerevisiae CCTCC 93161 during fermentation in aqueous solutions. Firstly, morphology of differently treated yeast cells were analyzed by scanning electron microscope, then the interactions between PAT and yeast cells were investigated by infrared absorption spectra of differently treated S. Cerevisiae cells before and after the adsorption of PAT. The results showed that the efficiency of PAT removal raised significantly with the increase of fermentation temperature and time, whereas it decreased significantly with the increase of initial PAT concentration in the fermentation system. The proteins and polysaccharides in the cell walls of yeast interacted with PAT and accounted for the physical adsorption. The current work would possibly provide some new insights on PAT control for fermented foods.

Effect of processing variables on the physico-chemical characteristics and aroma of borş, a traditional beverage derived from wheat bran

Borş is a traditional Romanian beverage obtained by naturally fermenting an aqueous suspension of wheat bran and corn flour, used as flavoring enhancer in local gastronomy since ancient times, and more recently consumed as refreshing drink. To investigate the changes in sensory, physico-chemical, phenolic and aroma composition resulted after two successive fermentations, borș samples were subjected to standard, sensory, HPLC and GC/MS analysis. Total phenolic compounds and ferulic acid, the most abundant phenolic compound, were positively influenced by natural starter addition, increase of fermentation temperature, and thermal treatment, whereas the effect on less abundant phenolic acids was not univocal. The variables had the same effect on antioxidant activity and brown index. Volatiles (alcohols, carboxylic acids, esters), pungent-sour and goat milk-cheese odor notes increased at higher fermentation temperature, whereas bran and yogurt odor notes decreased. The addition of a natural starter at 4 °C allowed balancing odor intensity and antioxidant activity.

Effect of fermentation temperature on the properties of exopolysaccharides and the acid gelation behavior for milk fermented by Streptococcus thermophilus strains DGCC7785 and St-143

We investigated the effect of fermenting milk with 2 strains (DGCC7785 and St-143) of Streptococcus thermophilus, which are known to produce different types of exopolysaccharide (EPS) structures. The yields and physical properties of these ropy EPS were monitored during the fermentation of milk at different temperatures. We wanted to understand how these types of EPS properties affected yogurt gelation. Reconstituted skim milk was fermented at 33, 39, or 45°C until pH values reached 5.2, 4.9, 4.7, and 4.5. Molar mass of ropy EPS samples was determined using size exclusion chromatography coupled with multiangle laser light scattering. Rheological properties of fermented milk gels were analyzed using small-strain dynamic oscillatory measurements. In both strains, concentrations of ropy EPS increased during fermentation and at all temperatures. Fermentation times, by both strains, were shortest at 45°C and longest at 33°C. For both strains, molar mass of ropy EPS ranged from 2 to 4 × 106 g/mol during fermentation. A major proteinaceous contaminant that was co-isolated with the ropy EPS fraction by our isolation method was identified as a milk-derived phosphoglycoprotein PP3. Increase in fermentation temperature from 33 to 45°C significantly decreased the storage modulus values (from 170 to 41 Pa) for milk gelled by strain DGCC7785, whereas the gels made with St-143 had very low storage modulus values (11-17 Pa) regardless of fermentation temperatures. For both strains, the values of maximum loss tangent in the milk gels increased with fermentation temperature; the maximum loss tangent occurred at higher pH values when milk was fermented by strain DGCC7785. The specific type of EPS produced appeared to be responsible for the differences in yogurt texture rather than the concentration or molar mass of the EPS.

Effects of Fermentation Temperature on Key Aroma Compounds and Sensory Properties of Apple Wine

Fermentation temperature strongly affects yeast metabolism during apple wine making and thus aromatic and quality profiles. In this study, the temperature effect during apple wine making on both the key aroma compounds and sensory properties of apple wine were investigated. The concentration of nine key aroma compounds (ethyl acetate, isobutyl acetate, isopentylacetate, ethyl caprylate, ethyl 4-hydroxybutanoate, isobutylalcohol, isopentylalcohol, 3-methylthio-1-propanol, and benzeneethanol) in apple wine significantly increased with the increase of fermentation temperature from 17 to 20 °C, and then eight out of the nine key aroma compounds with an exception of ethyl 4-hydroxybutanoate, decreased when the temperature goes up 20 to 26 °C. Sensory analysis showed that the apple wine fermented at 20 °C had the highest acceptance for consumers. Fermentation at the temperature of 20 °C was therefore considered to be the most suitable condition using the selected yeast strain (Saccharomyces cerevisiae AP05) for apple wine making. Changes in the fermentation temperature can considerably affect the production of key aroma compounds and sensory profiles of apple wine. These results could help apple wine producers make better quality production for consumers at the optimal fermentation temperature.

Aroma-active ester profile of ale beer produced under different fermentation and nutritional conditions

A broad range of aroma-active esters produced during fermentation are vital for the complex flavour of beer. This study assessed the influence of fermentation temperature, pH, and wort nutritional supplements on the production of yeast-derived ester compounds and the overall fermentation performance. The best fermentation performance was achieved when wort was supplemented with 0.75 g/l l-leucine resulting in highest reducing sugar and FAN (free amino nitrogen) utilization and ethanol production. At optimum fermentation pH of 5, 38.27% reducing sugars and 35.28% FAN was utilized resulting in 4.07% (v/v) ethanol. Wort supplemented with zinc sulphate (0.12 g/l) resulted in 5.01% ethanol (v/v) production and 54.32% reducing sugar utilization. Increase in fermentation temperature from 18°C to room temperature (± 22.5°C) resulted in 17.03% increased ethanol production and 14.42% and 62.82% increase in total acetate ester concentration and total ethyl ester concentration, respectively. Supplementation of worth with 0.12 g/l ZnSO4 resulted in 2.46-fold increase in both isoamyl acetate and ethyl decanoate concentration, while a 7.05-fold and 1.96-fold increase in the concentration of isoamyl acetate and ethyl decanoate, respectively was obtained upon 0.75 g/l l-leucine supplementation. Wort supplemented with l-leucine (0.75 g/l) yielded the highest beer foam head stability with a rating of 2.67, while highest yeast viability was achieved when wort was supplemented with 0.12 g/l zinc sulphate. Results from this study suggest that supplementing wort with essential nutrients required for yeast growth and optimizing the fermentation conditions could be an effective way of improving fermentation performance and controlling aroma-active esters in beer.

Study on the Metabolites of a Bacteria Strain Producing Esterifying Synthetase

The metabolites characteristics of a bacteria producing esterifying synthetase in different fermentation conditions were studied. A bacteria strain producing esterifying enzyme was isolated from Luzhou-flavor Daqu and it was identified by Biolog Microbes automated identification System. Fermentation conditions such as fermentation time, fermentation initial pH and fermentation temperature were changed. The fermentatiom broth was extracted by ethanol and analyzed by GC-MS. The results showed that the strain was Geobacillus thermoglucosidasius. With the prolonging of fermentation time, methanol and various higher alcohols were gradually decreased and even disappeared, but the esters were gradually increased. With the rise of fermentation initial pH, the acids were decreased. When initial pH was 7.5, more esters were produced, but some metabolites were not changed with the initial pH of fermentation, such as acetic acid, acetaldehyde, 3-methyl butanol and 3-Hydroxy-2-butanone etc. With the increase of fermentation temperature, the alcohols and acids kinds increased. When the fermentation temperature was 35°C, the more esters were produced.

Establishment of evaluation method to determine effects of veterinary medicinal products on manure fermentation using small-scale composting apparatus

To evaluate on a laboratory scale the influence of veterinary medicinal products (VMPs) excreted into feces on manure fermentation, we have developed an evaluation method that uses a small-scale composting apparatus. Each run is of approximately 3 kg scale and the operation can be conducted in an environmentally controlled laboratory. The main evaluation parameter is calorific value generated by aerobic fermentation. At the sulfadimethoxine (SDM) trial, the volume of CO(2) generated during fermentation and the disappearance of the inhibitory effect of immature manure on sprouting (using Komatsuna (Brassica rapa var. perviridis)) were measured. In addition, DNA of 16S rRNA was extracted from a manure sample and subjected to denaturing gradient gel electrophoresis (DGGE). The results suggest that the presence of such VMPs in feces affected the microbial community in manure fermentation, and indicate that the evaluation method may be used as a standard method to evaluate the effect of VMPs on the microbial community. Using the method, we obtained data of the influence of five VMPs approved for stockbreeding in Japan on swine manure fermentation. Erythromycin (EM) affected the calorific value even at a relatively low concentration (105 mg/3 kg manure). In contrast, oxytetracycline hydrochloride (OTC), norfloxacin (NFLX), and tylosin tartrate (TS) had no effect at that concentration. These VMPs also affected the increase of fermentation temperature when added at high concentrations.

Effect of yeast strain and fermentation conditions on the release of cell wall polysaccharides

To improve our understanding of the factors involved in polysaccharide release during alcoholic fermentation, we investigated three Saccharomyces cerevisiae strains in fermentation trials conducted at two temperatures (25 °C and 32 °C) and three sugar concentrations (20%, 23.5%, and 27%), with or without supplementation of grape juice with diammonium phosphate (DAP) or microcrystalline cellulose. In two yeast strains, the release of cell wall polysaccharides increased significantly with an increase in fermentation temperature and sugar concentration of the grape juice; the polysaccharide release was greater in stressed conditions, in which the cells were less viable and less metabolically active. In the third strain, the average amount of polysaccharides released into the medium decreased significantly at 32 °C with 27% sugar, and increased in grape juice supplemented with DAP. Thus, this strain released more polysaccharides when conditions were nearer to optimal and the yeast cells were more viable and metabolically active. Our results suggest that the yeast strains released cell wall polysaccharides via different mechanisms, and that the cell wall integrity pathway may account for some of the differences in polysaccharide release among the strains.