Changing the polyphenol composition and enhancing the enzyme activity of sorghum grain by solid-state fermentation with different microbial strains.

BACKGROUND: Solid-state fermentation (SSF) has been widely used in the processing of sorghum grain (SG) because it can produce products with improved sensory characteristics. To clarify the influence of different microbial strains on the SSF of SG, especially on the polyphenols content and composition, Lactiplantibacillus plantarum, Saccharomyces cerevisiae, Rhizopus oryzae, Aspergillus oryzae, and Neurospora sitophila were used separately and together for SSF of SG. Furthermore, the relationship between the dynamic changes in polyphenols and enzyme activity closely related to the metabolism of polyphenols has also been measured and analyzed. Microstructural changes observed after SSF provide a visual representation of the SSF on the SG. RESULTS: After SSF, tannin content (TC) and free phenolic content (FPC) were decreased by 56.36% and 23.48%, respectively. Polyphenol oxidase, ß-glucosidase and cellulase activities were increased 5.25, 3.27, and 45.57 times, respectively. TC and FPC were negatively correlated with cellulase activity. A positive correlation between FPC and xylanase activity after 30 h SSF became negative after 48 h SSF. The SG surface was fragmented and porous, reducing the blocking effect of cortex. CONCLUSION: Cellulase played a crucial role in promoting the degradation of tannin (antinutrient) and phenolic compounds. Xylanase continued to release flavonoids while microbial metabolism consumed them with the extension of SSF time. SSF is an effective way to improve the bioactivity and processing characteristics of SG. © 2024 Society of Chemical Industry.

Effects of different solid-state fermentation ratios of S. cerevisiae and L. plantarum on physico-chemical properties of wheat bran and the quality of whole wheat bread.

BACKGROUND: The addition of wheat bran (WB) could improve the nutritional quality of whole wheat bread (WWB); however, it also caused many negative effects on the quality of bread. To improve the physico-chemical properties of WB and the quality of WWB, WB was solid-state fermented with different ratios of commercially available S. cerevisiae and L. plantarum, and utilized to prepare WWB. RESULTS: The physico-chemical properties of WB including dietary fiber content and its components, amino acid composition, and antioxidant activities were determined. After solid-state fermentation, the physico-chemical properties of WB were improved. WBSac:Lac = 2:1 showed higher antioxidant activity (only the total antioxidant activity was slightly lower than WBSac:Lac = 1:1 ), and greater concentration of soluble dietary fiber (9.22%) and essential amino acids / total amino acids (42.04) than the other WB samples. Whole wheat bread quality was investigated by measuring specific volume, porosity, texture, aroma, and volatile compounds. The WWB made with WBSac:Lac = 2:1 showed a higher specific volume, more uniform porosity structure, better texture, and more volatile compounds than the other samples. CONCLUSION: Using a ratio of yeast and lactobacilli of 2:1, the solid-state fermentation maximally improves the processing properties of WB, and prepares WWB with the best quality. © 2021 Society of Chemical Industry.

Effect of Proofing on the Rheology and Moisture Distribution of Corn Starch-Hydroxypropylmethylcellulose Gluten-Free Dough.

Dough rheology, mainly enabled by gluten in the traditional dough, determines the end-products' quality, particularly by affecting gas production and retention capacities during proofing. Gluten-free dough has quite different rheological performance compared with gluten-containing dough. To deepen the understanding of gluten-free dough, variations of rheology and moisture distribution of corn starch-hydroxypropylmethylcellulose (CS-HPMC) gluten-free dough in the process of proofing were studied. Significant differences were found in terms of soluble carbohydrate composition, moisture distribution, and rheology. Arabinose, glucose, fructose, and mannose were the main composition of soluble carbohydrates in CS-HPMC dough, out of which glucose was preferentially utilized during proofing. Non-freezable water content and third relaxation time decreased from 44.24% and 2171.12 ms to 41.39% and 766.4 ms, respectively, whereas the amplitudes of T23 increased from 0.03% to 0.19%, indicating reduced bounded water proportion and improved water mobility with proofing time. Frequency dependence and the maximum creep compliance increased, whereas zero shear viscosity reduced, suggesting decreased molecular interactions and flowability, but improved dough rigidity. In conclusion, the reduced soluble carbohydrates and improved water mobility decreased molecular entanglements and hydrogen bonding. Furthermore, yeast growth restricted a large amount of water, resulting in declined flowability and increased rigidity.

Nutrition and Sensory Evaluation of Solid-State Fermented Brown Rice Based on Cluster and Principal Component Analysis.

Consumption of brown rice (BR) contributes to the implementation of the grain-saving policy and improvement of residents' nutrient status. However, the undesirable cooking properties, poor palatability, and presence of anti-nutritional factors limit the demand of BR products. To enhance its quality, BR was solid-state fermented with single and mixed strains of Lb. plantarum, S. cerevisiae, R. oryzae, A. oryzae, and N. sitophila. Effects of solid-state fermentation (SSF) with different strains on the nutrition and sensory characteristics of BR were analyzed by spectroscopic method, chromatography, and sensory assessment. Contents of arabinoxylans, ß-glucan, γ-oryzanol, phenolic, and flavonoid were significantly increased by 41.61%, 136.02%, 30.51%, 106.90%, and 65.08% after SSF, respectively (p < 0.05), while the insoluble dietary fiber and phytic acid contents reduced by 42.69% and 55.92%. The brightness and sensory score of BR significantly improved after SSF. Furthermore, cluster analysis (CA) and principal component analysis (PCA) were employed to evaluate BR quality. Three clusters were obtained according to CA, including BR fermented for 30 h and 48 h, BR fermented for 12 h, and the control group. Based on PCA, the best SSF processing technology was BR fermented with Lb. plantarum (0.5%, v/w) and S. cerevisiae (0.5%, v/w) at 28 °C for 48 h (liquid-to-solid ratio 3:10).

Comparative study of solid-state fermentation with different microbial strains on the bioactive compounds and microstructure of brown rice.

The effects of solid-state fermentation (SSF) with Lactiplantibacillus plantarum, Saccharomyces cerevisiae, Rhizopus oryzae, Aspergillus oryzae, and Neurospora sitophila were determined on the bioactive compound content and grain microstructure of brown rice (BR). After SSF, the ß-glucan, arabinoxylans, γ-oryzanol, thiamine, riboflavin, phenolic, and flavonoid contents increased by 147, 11.2, 30.5, 16.9, 21.1, 76%, and 49.6%, respectively, indicating a marked increase in bioactive compound content. In addition, the water-soluble dietary fiber and arabinoxylan contents, and free phenolic and flavonoid contents significantly increased (p < 0.05). These changes were consistent with the microstructural changes observed after SSF, i.e., the outer cortex was rough, cracked, porous and separated from the starch endosperm, which was also cracked and porous; this should increase the dietary bioavailability of the bioactive compounds. SSF, especially with A. oryzae and Lb. plantarum, greatly enhanced the bioactive compound content in BR and has great potential in BR processing.

Effects of different high hydrostatic pressure-treated potato starch on the processing performance of dough-like model systems.

In this study, potato starch (PS) was processed by high hydrostatic pressure (HHP) at 200, 350 and 500 MPa for 30 min at 25 °C. Effects of HHP-treated PS on the processing performance of PS-gluten and PS-hydroxypropylmethylcellulose (HPMC) dough-like model systems were investigated. For PS-gluten doughs, as HHP pressure increasing, total gas production (from 85 to 204 mL), elasticity (from 43.73 to 59.95%) and relaxation time of loosely bond water (from 20.73 to 25.53 ms) increased significantly (P < .05), while retrogradation rate (from 2.65 to 1.15 Nm) decreased, indicating that HHP-treated PS delayed dough retrogradation and increased active yeast metabolism, recovery capacity and water mobility. For PS-HPMC doughs, in addition to the decreased retrogradation rate and increased total gas production and relaxation time of loosely bond water, the retention coefficient (from 89.9 to 95.4%) and amplitude of tightly bond water (from 15.95 to 20.71%) increased, indicating that HHP-treated PS increased gas holding capacity and tightly bond water content of the dough. In conclusion, HHP-treated PS improved the processing performance of PS-gluten and PS-HPMC doughs.

Effects of starch from five different botanical sources on the rheological and structural properties of starch-gluten model doughs.

Wheat, corn, tapioca, sweet potato and potato starches were independently mixed into starch-gluten model doughs containing 15% (w/w) vital gluten. Rheological properties, including linear viscoelasticity region, frequency dependence and recovery capacity, were studied by strain sweep, frequency sweep, and creep and recovery measurements. Structural properties were also investigated by measuring the disulfide bonds (-SS-) content, SDS-PAGE and low-resolution 1H nuclear magnetic resonance. Wheat starch (WS)-gluten dough had the greatest linear viscoelasticity region (0.190%), lowest frequency dependence (0.128) and greatest recovery capacity (67.39%), while potato starch-gluten dough had the smallest linear viscoelasticity region (0.126%), greatest frequency dependence (0.195) and lowest recovery capacity (54.97%). Furthermore, WS-gluten dough showed the highest disulfide bonds (-SS-) content (3.47µmol/g), lowest intensity of extracted glutenin bands and highest bond water content (23.20%). This suggested that WS-gluten dough formed stronger starch-gluten interactions compared with those of the other four starch-gluten model doughs.

Comparative study of the effect of starches from five different sources on the rheological properties of gluten-free model doughs.

We investigated the effect of wheat (WS), corn (CS), tapioca (TS), sweet potato (SS) and potato (PS) starches on the rheological properties of starch-hydroxypropylmethylcellulose (HPMC) model doughs. Significant differences were found among model doughs made with different starches in terms of water absorption, development time, and strength. The PS-HPMC dough presented higher maximum creep compliance, followed successively by SS-, TS-, CS-, and WS-HPMC doughs, and the same order was found for the degree of dependence of G' on frequency sweep, suggesting that the resistance to deformation depends on network structure stability. More water distributed between hydration sites of HPMC and starch surface, leading to more hydrogen bonds and the formation of stable network. In conclusion, the rheological properties of model doughs are largely due to variation in structural and physicochemical properties of different starches, as well as varying interactions between different starches and HPMC.