Solid-state fermentation by Rhizopus oryzae improves flavor of wheat bran for application in food

Effects of different drying methods on physicochemical, textural, flavor, and sensory characteristics of yak jerky

The work aimed to study the effect of four drying methods, namely constant temperature hot air drying (HD), microwave drying (MD), hot air microwave drying (HMD), and gradient hot air drying (GHD), on quality characteristics of dried yak meat. The analyses of physicochemical, textural, flavor, and sensory characteristics were carried out based on these four drying methods. The results revealed that microwave dried yak jerky exhibited better color and received the highest sensory score. Hardness of samples were affected by the drying methods, which showed significant differences. There were 21 free amino acids (FAAs) detected in dried yak samples. The samples treated by microwave drying showed the highest total free amino acid content (73.30 mg/100 g) and the EUC value was significantly higher than other methods, indicating the sample displayed greater flavor. A total of 153 volatile compounds were identified in dried yak meat samples, primarily including aldehydes, ketones, and esters. Moreover, the sensory evaluation indicated that the drying methods could significantly affect on color, flavor, and overall acceptability of different samples. Microwave drying samples scored higher than other drying methods. Overall, considering aspects of quality, time savings, and energy efficiency, microwave drying of yak jerky emerges as a more satisfactory option. This study could provide important theoretical support for the application of drying methods to improve the quality of yak jerky and enhance production efficiency.

Fermentation biotechnology applied to wheat bran for the degradation of cell wall fiber and its potential health benefits: A review

Consumption of wheat bran is associated with health benefits. However, the insoluble cell layer fiber and considerable levels of anti-nutritional factors limit bioavailability of wheat bran, which can be effectively improved through fermentation. To comprehensively elucidate the precise biotransformation and health benefits mechanisms underlying wheat bran fermentation. This review investigates current fermentation biotechnology for wheat bran, nutritional effects of fermented wheat bran, mechanisms by which fermented wheat bran induces health benefits, and the application of fermented wheat bran in food systems. The potential strategies to improve fermented wheat bran and existing limitations on its application are also covered. Current findings support that microorganisms produce enzymes that degrade the cell wall fiber of wheat bran during the fermentation, releasing nutrients and producing new active substances while degrading anti-nutrient factors in order to effectively improve nutrient bioavailability, enhance antioxidant activity, and regulate gut microbes for health effects. Fermentation has been an effective way to degrade cell wall fiber, thereby improving nutrition and quality of whole grain or bran-rich food products. Currently, there is a lack of standardization in fermentation and human intervention studies. In conclusion, understanding effects of fermentation on wheat bran should guide the development and application of bran-rich products.

Solid-state fermentation using wheat bran to produce glucose syrup and functional cereal bars

Wheat bran is one of the most abundant by-products from grain milling, which can be used as substrate for solid-state fermentation (SSF) to obtain enzymes able to convert this agro-industrial waste into glucose syrup, which in turn can be applied for the production of different food products. The present study aimed to determine centesimal composition of wheat bran, obtain enzymatic extract that converts wheat bran into wheat glucose syrup (WGS), produce rice flakes cereal bars (RFCB), and evaluate their nutritional composition and the presence of functional compounds, as well as their antioxidant potential. Determination of centesimal composition of wheat bran demonstrated its nutritional potential. Enzymatic extract was obtained and it converted wheat bran into WGS, which were applied to rice flakes producing RFCB. These cereal bars proved to be a source of dietary fiber (1.8 g) and soluble protein (7.2 g) while RCFB produced with corn glucose syrup did not present these nutritional components. In addition, RFCB produced with WGS showed polyphenolic compounds, among them flavonoids, which exhibited antioxidant activity by DPPH and ABTS radical scavenging (47.46% and 711.89 μM Trolox Equivalent/g, respectively), and iron ion reduction (71.70 μM Trolox equivalent/g). Final product showed a decrease in caloric value and sodium content. Therefore, the present study showed that the bioprocess of SSF yields a nutritional, ecological, and functional food product, which might be of great interest for food industry, adding nutritional and functional value to a well-stablished product.

Fungal dynamic during apricot wine spontaneous fermentation and aromatic characteristics of Pichia kudriavzevii for potential as starter

Microbial activity during spontaneous fermentation in alcoholic beverages have driven in developing the chemical and aromatic characteristic of products but not clear in apricot wines. We have characterised the composition of fungal communities and volatile metabolites in apricot wine spontaneous fermentation among two Shaanxi regions. Results showed that Aureobasidium, Alternaria, Pichia and Saccharomyces, were the dominant fungi in apricot wine fermentation. A total of 80 volatiles including esters, alcohols, acids and terpenes were detected from two apricot wines. Their correlations suggested that apricot wine aroma was mainly affected by Pichia kudriavzevii, rather than Saccharomyces cerevisiae we commonly considered. Furthermore, reinforced inoculation of P. kudriavzevii LQD20 has exhibited the commendable potential in enhancing sensory qualities. The results of this study provide fundamental information of the indigenous microbiota in microbial dynamic during apricot wine fermentation, which would be helpful in exploiting the strains with potential for industrial use as starter cultures.

Microbial proteases and their applications

Proteases (proteinases or peptidases) are a class of hydrolases that cleave peptide chains in proteins. Endopeptidases are a type of protease that hydrolyze the internal peptide bonds of proteins, forming shorter peptides; exopeptidases hydrolyze the terminal peptide bonds from the C-terminal or N-terminal, forming free amino acids. Microbial proteases are a popular instrument in many industrial applications. In this review, the classification, detection, identification, and sources of microbial proteases are systematically introduced, as well as their applications in food, detergents, waste treatment, and biotechnology processes in the industry fields. In addition, recent studies on techniques used to express heterologous microbial proteases are summarized to describe the process of studying proteases. Finally, future developmental trends for microbial proteases are discussed.

Effect of Adding Fermented Proso Millet Bran Dietary Fiber on Micro-Structural, Physicochemical, and Digestive Properties of Gluten-Free Proso Millet-Based Dough and Cake

The increasing demand for functional foods has pushed the food industry to produce fiber-enriched products. In this study, rheological, microstructural, physicochemical, and functional characteristics were investigated for whole proso millet dough and cake, fortified with fermented proso millet bran dietary fiber flour (F-DF). Results showed that proso millet flour is less absorbent and stable than the control group. Adding proso millet flour and F-DF reduced the elasticity of the dough and increased its hardness, but had no significant effect on viscosity, cohesion, and resilience. The microstructure analysis exhibited an unformed continuous network formation in proso millet dough. Analyses suggested that proso millet flour combined with the fermented dietary fiber group had significantly higher total phenol content (0.46 GAE mg/g), DPPH• scavenging activity (66.84%), and ABTS•+ scavenging activity (87.01%) than did the other group. In addition, F-DF led to a significant reduction in the predicted released glucose contents of reformulated cakes. In summary, cakes prepared with the involvement of whole proso millet flour and F-DF exhibited less adverse sensory impact and possessed the potential to decrease postprandial blood glucose levels resulting purely from cake consumption.

The dynamics of physicochemical properties, microbial community, and flavor metabolites during the fermentation of semi-dry Hakka rice wine and traditional sweet rice wine

The dynamics of physicochemical properties, microbial community and flavor metabolites during fermentation of two typical Hakka rice wine were investigated. Results showed that total sugar content was 136.83 g/L in sweet rice wine, which almost 8 times higher than that in semi-dry rice wine. Its amino acid contents especially bitterness amino acids were also higher than those in semi-dry rice wine. Most organic acids in Hakka rice wine had the tendency of increase in initial stage of fermentation, following a decrease and finally being almost stable. A total of 131 volatiles including esters, alcohols, aldehydes, acids, ketones were detected. Pediococcus, Bacillus, Acinetobacter, Pantoea, Enterobacter and Lactobacillus were the dominant bacterial genera and Monascus, Saccharomyces, Rhizopus were the dominant fungal genera, which are strongly associated with the significant changes in flavor metabolites during Hakka rice wine fermentation. The obtained findings provided reference data for the optimization of Hakka rice wine fermentation.

Technology characteristics and flavor changes of traditional green wheat product nian zhuan in Northern China

Nian zhuan has its aroma as one of the perceived principal characteristics. The current study was aimed mainly to investigate the potential to include the aroma of nian zhuan as a new target criterion into the green wheat product chain. By improving the conditions for the traditional processing of nian zhuan, the optimal processing conditions were determined as green wheat (GW) 14 d, steaming the green wheat with the skin (SGWS) 26 min and cooked green wheat peeled (CGWP) 280 min, to evaluate the feasibility of using electronic nose (E-nose) and gas chromatography mass spectrometry (GC-MS) to discriminate nian zhuan in different stages. E-nose was used to recognize nian zhuan odors in different processing stages, and GC-MS to identify the individual volatile compounds. A total of 139 volatile compounds were detected by GC-MS, of which 71 key were screened by t-test (P < 0.01). The W1W, W1S, W2W and W2S sensors of E-nose gave higher responses to all samples, and effectively discriminated the samples. The most volatile compounds were produced in the millstone milling (MSM) stage of nian zhuan, and millstone could promote the release of volatile compounds from cooked green wheat by milling.