Rheological properties of indica rice determined by starch structure related enzymatic activities during after-ripening.

The processing quality of indica rice must undergo ripening after harvest to achieve stability and improvement. However, the mechanism underlying this process remains incompletely elucidated. Starch, the predominant component in indica rice, plays a crucial role in determining its properties. This study focused on analyzing the rheological properties and starch fine structure, as well as the related biosynthetic enzymes of indica rice during the after-ripening process. The results showed that after-ripened rice exhibited increased elastic modulus (G') and viscous modulus (G″), accompanied by a decrease in the loss tangent (Tan δ), indicating an enhancement in viscoelasticity and the gel network structure. Moreover, the proportions of amylopectin super long chains (DP 37-60) decreased, while those of medium chains (DP 13-24 and DP 25-36) or short chains (DP 6-12) of amylopectin increased. Additionally, the activities of starch branching enzyme (SBE) and starch debranching enzyme (DBE) declined over the after-ripening period. Pearson correlation analysis revealed that the rheological properties of after-ripened rice were correlated with the chain length distribution (CLD) of starch, which, in turn, was associated with its related endogenous enzymes. These findings provied new insights into understanding the quality changes of after-ripened indica rice.

Production and characterization of recrystallized linear α-glucans at different temperatures for controllable thermostability and digestibility.

Molecular structure of linear α-glucans (LAGs) and crystallization temperature have great effects on the thermostability and digestibility of recrystallized LAGs, but the recrystallization behaviors of LAGs in response to temperature remain unclear. Here LAGs with different lengths were prepared from amylopectin via chain elongation and debranching. Recrystallization of LAGs at 4 °C yielded B-type crystalline structure with relative crystallinity ranged from 23.7% to 46.1%. With a chain length of 40.2, an A-type allomorph was observed for a slow recrystallization at 50 °C. Differential scanning calorimetry suggested that A-type crystal had a higher thermostability than the B-type crystal, and increasing LAGs' chain length improved the dimension of double helices, whose assembly produced starch crystallites that enhanced the thermostability and decreased the in vitro digestibility of recrystallized LAGs. An improved thermostability of recrystallized LAGs preserved their ordered structures and kept the resistance to digestive enzymes, with a RS content up to 75.4%.

Manufacture and characterization of a novel dairy-free quinoa yogurt fermented by modified commercial starter with Weissella confusa.

Non-dairy yogurt is increasingly thought to be healthy food. However, no suitable starters limit its development. This study aimed to develop a novel and functional quinoa yogurt with a modified commercial starter. Compared with the other lactic acid bacteria (LAB), Weissella confusa showed a better fermentation performance of quinoa utilization. The synergistic effect of W. confusa and the commercial starter promoted the growth of LAB. It increased the fermentation rate of quinoa yogurt, further improving its texture, rheological properties, and storage stability. The modified starter significantly increased the nutritional qualities of the quinoa yogurt, including polyphenol content, antioxidant activity, digestive enzyme inhibition, and reduced postprandial blood glucose ability. Additionally, the modified starter enhanced the digestibility and bioaccessibility of polyphenols, protein, and fat in fermented quinoa yogurt. Overall, the commercial starter with W. confusa showed great potential for possible application in quinoa yogurt development.

Physicochemical Properties of the Rice Flour and Structural Features of the Isolated Starches from Saline-Tolerant Rice Grown at Different Levels of Soil Salinity.

Three varieties of saline-tolerant indica rice were grown in soils with salinities of 0.0-0.6% (w/w). The rice grown at salinities of 0.3 and 0.6% had a smaller grain dimension than its counterpart. Salinity stress altered the physiology of plants, leading to changes in the basic chemical compositions for all rice varieties, e.g., increasing the soil salinity improved the content of rice protein (RP). The pasting and rheological properties of the rice flour highly depended on its chemical compositions. An increase of RP inhibited the swelling of starch granules and accordingly decreased the peak viscosity of rice flour, while the aggregation of RP weakened the gel structure of the cooked rice flour. The isolated starches showed polyhedral granules, and they all had an A-type crystalline structure with relative crystallinity varying from 34.16 to 45.40%. Moreover, increasing the soil salinity enhanced the lamellar order and periodic length of the isolated starches.

Identification and evaluation of spoilage potential of four Bacillus strains isolated from slimy rice noodles.

This study isolated four strains of Bacillus from slimy fresh rice noodles (FRN) and preliminary identified them as B. cereus, B. amyloliquefaciens, B. altitudinis, and B. subtilis, respectively, using morphological, physiological, and genetic analyses. The spoilage potential of each of these strains was then evaluated in FRN. The results indicated that both B. amyloliquefaciens and B. subtilis can cause FRN to become sticky and smelly, accompanied by an increase of acidity and high amylase activity. B. cereus and B. altitudinis mainly caused odor deterioration of FRN. There were 29, 20, 25, 25, and 27 volatile organic compounds (VOCs) identified from control FRN and FRN samples inoculated with B. cereus, B. amyloliquefaciens, B. altitudinis, and B. subtilis, respectively. The compositions of VOCs in the samples inoculated with B. amyloliquefaciens and B. subtilis were similar; esters, volatile organic acids, and acetoin were the main volatile compounds in the FRN. For B. cereus and B. altitudinis, the main adverse flavor substances were acetic acid and ammonia. This study provides a theoretical basis for quality control in the production, storage, and sale of FRN.

Extrusion processing: A strategy for improving the functional components, physicochemical properties, and health benefits of whole grains.

Whole grains (WGs) contain a variety of bioactive components and have a proven role in the control of chronic diseases. Worldwide dietary guidelines recommend increasing the intake of WGs in the diet. Extrusion is a versatile and advanced technology that is often used to develop foods with high nutritional and sensory quality. This technology is widely used in the production of WG foods, and the extrusion process can leads to a series of changes in the properties and composition of WGs. In this review, we introduce the composition of WGs and describe how extrusion affects their physicochemical properties, including their chemical composition, expansion properties, pasting properties, hydration properties, texture, color, and microstructure. Extruded WG foods (EWGFs) can significantly inhibit chronic diseases such as diabetes and obesity, as well as reducing oxidation and inflammation due to the changes in the physicochemical properties of WGs during extrusion. Therefore, extrusion is an effective method to improve the functional properties of WG foods.

Volatile compounds, bacteria compositions and physicochemical properties of 10 fresh fermented rice noodles from southern China.

To clarify the discrepancy in characteristic flavor and bacteria composition of 10 fresh fermented rice noodles from southern China, the volatile and bacteria composition were determined by headspace-gas chromatography ion mobility spectrometry and 16SrRNA sequencing methods. The potential relationship between volatile compounds and bacterial composition has also been further revealed using spearman's correlation analysis. The contents of proximate composition, cooking properties and texture properties of 10 fresh fermented rice noodles exhibited significant different among them (p ＜ 0.05). The flavor analysis showed that a total of 54 compounds were detected. 1-Octen-one, ethyl 3-methylbutanoate, 3-methylbutanal, n-nonanal, hexanal, amyl acetate, ethanol and 2-pentyl furan were the key volatiles among them. The bacterial analysis showed that Leuconostoc and Lactococcus were the core bacteria at the genu level of all samples. Amyl acetate, 2-butanone and methyl-2-methylpropanoate were positively related to Lactococcus while ethanol was negatively correlated with Lactococcus. And Leuconostoc was positively related to 3-methylbutanal and acetone, while was negatively correlated with hexanal. Results indicated that key volatiles and textural properties of different fresh fermented rice noodle samples were associated with bacterial composition.

Antidiabetic Function of Lactobacillus fermentum MF423-Fermented Rice Bran and Its Effect on Gut Microbiota Structure in Type 2 Diabetic Mice.

Rice bran is an industrial byproduct that exerts several bioactivities despite its limited bioavailability. In this study, rice bran fermented with Lactobacillus fermentum MF423 (FLRB) had enhanced antidiabetic effects both in vitro and in vivo. FLRB could increase glucose consumption and decrease lipid accumulation in insulin resistant HepG2 cells. Eight weeks of FLRB treatment significantly reduced the levels of blood glucose and lipids and elevated antioxidant activity in type 2 diabetic mellitus (T2DM) mice. H&E staining revealed alleviation of overt lesions in the livers of FLRB-treated mice. Moreover, high-throughput sequencing showed notable variation in the composition of gut microbiota in FLRB-treated mice, especially for short-chain fatty acids (SCFAs)-producing bacteria such as Dubosiella and Lactobacillus. In conclusion, our results suggested that rice bran fermentation products can modulate the intestinal microbiota and improve T2DM-related biochemical abnormalities, so they can be applied as potential probiotics or dietary supplements.

Effect of Soy Protein Isolate on Textural Properties, Cooking Properties and Flavor of Whole-Grain Flat Rice Noodles.

To investigate the effect of soy protein isolate on the quality of whole-grain flat rice noodles, the texture as well as the cooking properties and flavor of flat rice noodles, whole-grain flat rice noodles and whole-grain flat rice noodles with soy protein isolate were investigated. Among the three tested rice noodles, whole-grain flat rice noodles with soy protein isolate showed the highest cohesiveness, adhesiveness, resilience, and springiness. Compared to the flat rice noodles and whole-grain flat rice noodles, whole-grain flat rice noodles with soy protein isolate increased their moisture content and water absorption, whereas the opposite trend was observed for their cooking loss. The electronic nose analysis showed stronger response values at W5S, W1W, and W2W. Solid phase micro extraction and gas chromatography-mass spectrometry results showed that aldehydes are the main volatile compounds in whole-grain flat rice noodles and whole-grain flat rice noodles with soy protein isolate. Moreover, seven more volatile compounds were detected in whole-grain flat rice noodles with soy protein isolate compared to flat rice noodles and whole-grain flat rice noodles. The whole-grain flat noodles with the addition of SPI are more sensory acceptable. Thus, soy protein isolate, as a natural and safe additive, could be used to improve the quality and enrich the flavor of whole-grain flat rice noodles.

New insights into the structure-activity relationships of antioxidative peptide PMRGGGGYHY.

The sequence and structure of antioxidant peptides play fundamental roles in their antioxidant functions. However, the structural mechanism of antioxidant peptides is still unclear. In this study, we used quantum calculations to reveal the antioxidant mechanism of the peptide PMRGGGGYHY. PMRGGGGYHY has multiple antioxidant active sites, and two tyrosine residues were determined to be the major active sites. Based on the structure-activity relationships of PMRGGGGYHY, the antioxidant activity of the modified peptide significantly improved by 4.8-fold to 9.73 ± 0.61 µmol TE/µmol. In addition, the removal of glycine residues from PMRGGGGYHY would increase the energy of the HOMOs and simplify the hydrogen bonding network, causing a significant increase in antioxidant activity. The intracellular ROS scavenging ability gradually decreased with decreasing glycine content. This same peptide has very different effects in vitro versus as a cellular antioxidant. This paper provides new insights into the structural mechanism and rational design/modification of novel antioxidant peptides.

Chemical composition, structure, physicochemical and functional properties of rice bran dietary fiber modified by cellulase treatment.

Rice bran dietary fiber (ERBDF) subjected to pre-water-washing and complex enzyme treatment using heat-stable α-amylase, alcalase, and glucoamylase had significantly higher (p < 0.05) proportions of cellulose, hemicellulose, lignin, and lower proportions of lipid, protein, and starch than rice bran dietary fiber subjected to complex enzyme treatment without pre-water-washing. Cellulase modification of ERBDF significantly decreased (p < 0.05) cellulose, hemicellulose, starch, and protein contents while the relative lignin content increased. Cellulase modification significantly improved (p < 0.05) water-holding capacity, oil-holding capacity, swelling capacity, cholesterol absorption capacity, and glucose adsorption capacity, while decreasing the emulsifying capacity and glucose dialysis retardation index. The changes of physicochemical and functional properties of fiber samples after cellulase modification were attributed to the increased porosity of the fiber surface, greater exposure of binding sites caused by reduced crystallinity, and changes to the chemical composition.

Impact of Lactobacillus plantarum 423 fermentation on the antioxidant activity and flavor properties of rice bran and wheat bran.

Rice bran (RB) and wheat bran (WB) fermented with L. plantarum 423 had enhanced odor intensity, especially for sulfides and aromatics. The hydroxyl radical-scavenging activity (73.28 ± 3.18%) and oxygen radical-scavenging activity (2.12 ± 0.08 mmol·TE/g) of RB fermentation broth were better than those of WB fermentation broth. Even at 2 µg/ml, the purified antioxidant fractions from the WB fermentation broth showed strong intracellular ROS-scavenging activity in human umbilical vein endothelial cells (HUVECs), and the purified antioxidant fractions (200 µg/ml) from the RB fermentation broth had a good antiaging effect. The dominant antioxidant components in the RB and WB fermentation broths were acids (70.21%) and ketones (10.64%), these components jointly give the RB and WB fermentation broths a variety of antioxidant properties. These results are beneficial for developing RB and WB deep-processing technology and laid the foundation for the preparation of antioxidant fractions with L. plantarum 423.

Genome Sequencing of Mesonia algae K4-1 Reveals Its Adaptation to the Arctic Ocean.

The special ecological environment of the Arctic has brought about a large number of salt-tolerant and psychrotolerant microorganisms. We isolated two culturable bacterial strains of the genus Mesonia; one from the Arctic ocean, Mesonia algae K4-1, and one from the tropical sea, Mesonia sp. HuA40. Our genome analysis and phenotypic experiments indicated that Mesonia algae K4-1 is a moderately halophilic and psychrophilic bacterium. Mesonia algae K4-1 can tolerate 3-14% NaCl and grow at a wide range of temperatures from 4 to 50°C. Mesonia sp. HuA40 is a mesophilic bacterium that can only grow with 3-9% NaCl. In addition, the salt adaptation strategy of Mesonia algae K4-1 accumulates organic osmolytes in the cell. RNA helicases, glutathione and organic compatible solutes may play important roles in maintaining the metabolism and physiological function of Mesonia algae K4-1 under cold stress. Moreover, the ability of Mesonia algae K4-1 to adapt to an oligotrophic marine environment is likely due to the synthesis of a large number of extracellular polysaccharides and the secretion of various families of extracellular proteases. This study systematically analyzed the relationship between genomic differentiation and environmental factors of the Mesonia genus and revealed the possible adaptation mechanism of Mesonia algae K4-1 in the extreme Arctic marine environment at the genomic level.

Volatile profiles of fresh rice noodles fermented with pure and mixed cultures.

The volatile profiles of fresh rice noodles (FRN) fermented with pure and five commercial mixed cultures were studied by using solid phase micro extraction/ gas chromatography-mass spectrometry, electronic nose, and sensory evaluations. The main volatile compounds of FRN by pure culture included aldehydes represented by nonanal, octanal, and 2,4-Pentadienal, and alcohols represented by hexanol and 1-nonanol. Its aroma profiles showed remarkable changes during the storage time from 0 to 30 h, indicating the reduction in aldehydes and the increase in alcohols and isoamyl alcohol. Significant variations such as the types, relative amounts, and category distributions of volatile compounds were observed in FRN by five mixed cultures. The bacterial compositions of these mixed cultures were quite different, which might be responsible for the significant variations in volatile profiles. Principal component analysis on E-nose data demonstrated that FRN by Culture A, B, and C shared similar flavor, while FRN by Culture D and E possessed different aroma compared to the above three. FRN produced with pure fermentation showed the highest score in sensory evaluation, whereas FRN by mixed cultures indicated rice fragrance, light fragrance, peculiar smell, or foul smell.

Germination of sorghum grain results in significant changes in paste and texture properties.

The changes in sorghum [Sorghum bicolor (L.) Moench] proteins during germination and the resultant effects on the physicochemical properties of sorghum flour were studied using non-germinated grains as a control. Results showed that flour obtained from germinated sorghum grains had lower protein levels, higher protease levels, and higher free amino nitrogen content compared with the control. There was an increase in the albumin and globulin protein fractions and a decrease in kafirin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that this decrease was the result of a decrease in γ-kafirins, while microscopy found that a continuous protein network was formed. Following the germination-associated protein changes, the viscosities of sorghum paste decreased with germination from a peak viscosity value of 1,324 rapid visco units (RVU) down to 727 RVU in white sorghum (WS), and from 1,549 RVU to 1,295 RVU in red sorghum (RS). The hardness of the sorghum gels was significantly enhanced after germination, with WS increasing from 1,640 g to 5,374 g and RS from 970 g to 5,529 g. Thus, the study revealed that germination decreased the viscosity of sorghum paste and increased the strength of sorghum gel by changing the content and structure of sorghum protein, making it possible to design new foods that require thickening and gelling using germinated sorghum. PRACTICAL APPLICATIONS: Germination triggers the protease system of sprouting seeds, leading to the breakdown of proteins into simpler forms that decrease the viscosity of sorghum paste and improve the strength of sorghum gel, allowing the use of germinated sorghum to design new foods that require thickening and gelling.

Effect of whole wheat flour on the quality, texture profile, and oxidation stability of instant fried noodles.

The effects of whole wheat flour (WWF) on pasting properties of instant fried noodle dry mix and quality of final product were investigated in this research. Refined wheat flour in the recipe for instant-fried noodle was replaced by WWF at different levels. The peak and final viscosities were significantly and negatively correlated to WWF substitution level. With increasing WWF level, the hardness, cohesiveness, adhesiveness, and resilience values of instant fried noodles decreased by 11.63, 16.23, 16.67, 20.00%, respectively. WWF darkened noodle's surface color and increased its oil content (26.63%). A porous and less uniformed structure of the WWF instant fried noodles was observed by a scanning electron microscope. Moreover, the WWF incorporation lowered peroxide values of the instant fried noodles during storage. In conclusion, even though the oil content increased, WWF was helpful to inhibit the oil oxidation and produce instant fried noodles with softer texture and less sticky surface. PRACTICAL APPLICATIONS: Refined wheat flour in the recipe for instant-fried noodle was replaced by whole wheat flour (WWF), which is rich in dietary fibers, vitamins, and other bioactive compounds. The addition of WWF delayed the retrogradation tendency of starch in the dry mix. WWF-added instant noodles had softer texture, less sticky surface, and lower peroxide value. Based on the results of this study, the refined wheat flour in the recipe for instant-fried noodle could be partially replaced by WWF to make noodles with better texture profile and higher consumer acceptance.