Milling degree affects the fermentation properties of rice:perspectives from the composition of nutrients and gut microbiota via in vitro fermentation

Fermentation substrates of rice with different milling degrees(MDs) were prepared and fermented with human feces to compare their fermentation properties and effects on gut microbiota.MD 0s,MD 5s and MD 60s represented brown rice,moderately-milled rice and white rice,respectively.After in vitro fermentation,the MD 5s group showed higher starch utilization,compared with the MD 0s and 60s groups evaluated by Fourier transform infrared spectrometer,and confocal laser scanning microscope.Effects of fermentation substrates of rice with different MDs on gut microbiota were evaluated by 16S rDNA sequencing.All the sample groups reduced the pH and produced short-chain fatty acids(SCFAs) and branched-chain fatty acids.The MD 5s group exhibited higher α-diversity than the MD 0s and 60s groups.Abundances of Phascolarctobacterium,Blautia and norank_f_Ruminococcaceae were higher in the MD 0s and 5s groups,compared with the MD 60s group.These bacteria were also positively correlated with the SCFAs production via Spearman correlation analysis.In vitro culture assay revealed that fermentation substrates of MD 0s and 5s promoted the growth of two probiotics(Akkermansia muciniphila and Bifidobacterium adolescentis).Our results showed that moderate milling might be an appropriate way to produce rice products with richer nutrients and better fermentation properties.

过氧化二异丙苯硫化制备增强耐热聚乳酸

聚乳酸的链段结构对其热力学性能有重要影响。过氧化二异丙苯(DCP)作为自由基引发剂,通过反应性共混可以诱导聚合物分子链支化、交联,进行功能化改性。文中制备了一系列不同DCP添加量的PLA/DCP共混物,重点研究了DCP含量对聚乳酸(PLA)熔融结晶行为、流变行为、耐热性能和力学性能的影响。结果表明,DCP可以诱导PLA的分子链支化和交联。当DCP质量分数大于0.5%时,交联反应占据主导作用,共混扭矩显著升高、复数黏度增大。DCP引发PLA分子链自交联,不熔的PLA链段可以作为成核中心,大幅提高了PLA成核密度,进而提高其结晶速率和结晶度。DCP的添加可以有效地提高聚乳酸的拉伸强度,但对断裂伸长率和冲击强度的影响较小。经过退火,共混物的力学性能保持不变,共混物的耐热性能大幅提高。当DCP质量分数大于0.5%时,共混物的维卡软化温度可以提高到155℃。

Effect of germinating quinoa flour on wheat noodle quality and changes in blood glucose

Germinated quinoa flour has been proven to be rich in a variety of nutrients,in order to improve the nutritional value and reduce the glycemic index of wheat noodle,20%(w/w)of white quinoa(WQ),red quinoa(RQ),black quinoa(BQ)powder with different germination time were added to wheat noodle.The gemination rate,sprout length,digestion ratio and microstructure of WQ,RQ,and BQ were determined.Also,the characteristics of cooking,texture,digestion and blood glucose of noodles were studied.It was found that the addition of quinoa flour(WQ-0,WQ-1,RQ-0,RQ-1,BQ-0,BQ-3)maintained the cooking and texture characteristics of wheat noodle.Meanwhile,WQ-1,RQ-1,BQ-3 reduced the optimal cooking time and starch digestibility compared with wheat noodle.At the same time,it showed that the addition of WQ-1,BQ-3 significantly reduced the area under the blood glucose curve(AUC)to 132.17,126.83(mmol/L)⋅h,respectively.The correlation analysis verified that the digestion ratio was significantly positively correlated with AUC(p<0.01).It will provide the theoretical basis for the development of new quinoa foods that lower blood sugar.

Intelligent Identification of Rotating Stall for Centrifugal Compressor Based on Pressure Pulsation Signals and SDKAE Network

Most accidents of centrifugal compressors are caused by fluid pulsation or unsteady fluid excitation.Rotating stall,as an unstable flow phenomenon in the compressor,is a difficult point in the field of fluid machinery research.In this paper,a stack denoising kernel autoencoder neural network method is proposed to study the early warning of rotating stall in a centrifugal compressor.By collecting the pressure pulsation signals of the centrifugal compressor under different flow rates in engineering practice,a double hidden layer sparse denoising autoencoder neural network is constructed.According to the output labels of the network,it can be judged whether the rotation stall occurs.At the same time,the Gaussian kernel is used to optimize the loss function of the whole neural network to improve the signal feature learning ability of the network.From the experimental results,it can be seen that the flow state of the centrifugal compressor is accurately judged,and the rotation stall early warning of the centrifugal compressor at different speeds is realized,which lays a foundation for the research of intelligent operation and maintenance of the centrifugal compressor.

Biotransformation of quinoa phenolic compounds with Monascus anka to enhance the antioxidant capacity and digestive enzyme inhibitory activity

This research aims to change the phenolic fractions and the bioactivities of quinoa by solid-state fermentation(SSF)with the edible fungus Monascus anka(M.anka).The contents of protein and fat increased in the fermented product,while the carbohydrate decreased.After 6-day fermentation with M.anka,the amount of phenolic compound reached the highest level.The majority of phenolic forms in fermented quinoa were phenolic acids,mainly ferulic acid,protocatechuic acid and p-hydroxybenzoic acid.Ultrahigh-performance liquid chromatography-mass spectrometry(UHPLC-MS)results showed that SSF was an effective method to transform quinoa phenolic compounds.Free fractions could be rapidly absorbed in the small intestine,suggesting that SSF with M.anka was a useful method to enhance bioavailable antioxidants.Antioxidant ability in vitro results showed that phenolic fractions from fermented quinoa were greater than the unfermented quinoa,and a significant cellular antioxidant activity(CAA)increment of 135%was obtained in the free phenolic fraction of fermented quinoa.Moreover,α-amylase andα-glucosidase inhibition activities were enhanced with fermentation.Correlation matrix analysis revealed that most of the free phenolic compounds showed strong positive correlations with antioxidant activities and digestive enzyme activities.Consequently,fermentation with M.anka was a particularly promising method to enhance the bioactivity of quinoa.

High-level production of𝛾γ-aminobutyric acid via efficient co-expression of the key genes of glutamate decarboxylase system in Escherichia coli

Biosynthesis of the functional factor𝛾γ-aminobutyric acid(GABA)in bacteria involves two key proteins an intra-cellular glutamate decarboxylase(GadB)and a membrane-bound antiporter(GadC).Efficient co-expression of suitable GadB and GadC candidates is crucial for improving GABA productivity.In this study,gadBΔC11 of Lacti-plantibacillus plantarum and gadCΔC41 of Escherichia coli were inserted into the designed double promoter(P T7lac and P BAD)expression system.Then,E.coli Lemo21(DE3)was chosen as the host to minimize the toxic effects of GadCΔC41 overexpression.Furthermore,a green and high-efficiency GABA synthesis system using dormant engineered Lemo21(DE3)cells as biocatalysts was developed.The total GABA yield reached 829.08 g/L with a 98.7%conversion ratio within 13 h,when engineered E.coli Lemo21(DE3)cells were concentrated to an OD 600 of 20 and reused for three cycles in a 3 M L-glutamate solution at 37℃,which represented the highest GABA productivity ever reported.Overall,expanding the active pH ranges of GadB and GadC toward physiological pH and employing a tunable expression host for membrane-bound GadC production is a promising strategy for high-level GABA biosynthesis in E.coli.

Formulation of plant-based yoghurt from soybean and quinoa and evaluation of physicochemical,rheological,sensory and functional properties

The aim of this study was to develop a novel plant-based yoghurt with high sensory acceptance and nutrition value.Soybean and quinoa were used as the substrates,and all formulations with different substrate ratios were inoculated with lactic acid bacteria(LAB).Fermentation modified the proximate composition,and a higher content of soybean accentuated the growth of LAB.Formulated yoghurts presented a weak post-acidification,and the viability of LAB was higher than 10^(6-7)CFU/g during a 21 days storage.Quinoa addition significantly improved the water holding capacity(WHC)and decreased the yellowness,and an increase of lightness and a decrease of WHC occurred during the storage.Compared with the plain substrate yoghurt,mixed formulation had no significant impact on textual parameters,whereas increased the liking scores in sensory evaluation.Furthermore,fermentation improved the total phenolic content(TPC),which showed a dose-dependent relationship between soybean content.Results obtained from DPPH,ABTS,hydroxyl radical scavenging assay,FRAP assay,andα-amylase,α-glucosidase and pancreatic lipase inhibition assay showed that fermentation enhanced the antioxidant capacities and digestive enzyme inhibitory activities.TPC increase and phenolic biotransformation may explain the enhancement of the nutritive values.Based on the sensory and function evaluation,the ratio of quinoa against soybean at 8:2 and 2:8 presented the best formulations.

Effect of storage conditions on the textural properties and in vitro digestibility of wheat bread containing whole quinoa flour

This research aimed to clarify the evolution of textural characteristics and in vitro digestibility under different storage conditions.Quickly increasing hardness and decreasing resilience was observed in quinoa bread after 5d cold(4℃)storage.However,when stored at􀀀18℃for 5d,bread crumb still maintains a dense alveographic with 52.33%of cell density and 33.76%area fractions.In addition,the starch digestion rate decreased with increasing retrogradation degree.Scanning electron microscope(SEM)characterizations illustrated that the chunky matrix gradually disappeared with digestion.However,quinoa starch(QS)granules were the most difficult to digest owing to the relative intactness and wrapping in the protein-starch bulk.Meanwhile,X-ray diffraction(XRD)showed that the crystal structure of starch remained 21.09%stored in frozen conditions,and wheat type-A(WA)starch was mainly involved in gelatinization.The results of water migration proved that water participated in the retrogradation of starch and affected the quality of quinoa bread.Overall,bread stored in frozen conditions can maintain good texture characteristics and slow starch digestion rate.This study indicates that quinoa flour fortified bread has the potential to be developed as staple food with both low glycemic index values and storage stability.