查看更多>>摘要：For a long time, the abuse of antibiotics and the excessive use of synthetic preservatives have caused harm to human health. Bacteriocins produced by lactic acid bacteria (LAB) are nontoxic and exhibit potential as natural preservatives. In this experiment, the bacteriocin 1.0320 produced by Lactobacillus rhamnosus 1.0320 screened from traditional koumiss was used as the research object. The main purpose of the experiment was to purify bacteriocin 1.0320 and study its antimicrobial mechanism. Bacteriocin 1.0320 exhibited antimicrobial activity against gram-positive and gram-negative bacteria. Bacteriocin 1.0320 in cell-free fermentation supernatant (CFS) was purified by ethyl acetate extraction and anion exchange chromatography. The molecular mass of bacteriocin 1.0320 was 1-3.3 KDa as assessed by dialysis and Tricine sodium dodecyl sulphate-polyacrylamide gel electrophoresis (Tricine-SDS-PAGE). The minimum inhibitory concentration of bacteriocin 1.0320 on E scherichia coli UB1005 was 0.072 mg/mL. Bacteriocin 1.0320 can form pores on the surface of cell membrane, increase the permeability of cell membrane, dissipate the cytoplasmic membrane potential and transmembrane pH gradient, and destroy the integrity of cell membrane, causing cell content to flow out and cell death. The effect is related to the concentration of bacteriocin 1.0320. This information provides the theoretical basis for the antimicrobial mechanism of L. rhamnosus bacteriocin.
查看更多>>摘要：The effects of incubation on the nutritional and antioxidant properties of defatted adlay bran (DAB) were investigated in the current study. The results revealed that the incubation process significantly decreased pH, while increased the total titratable acidity and reducing sugar content of DAB. The DAB proteins were significantly degraded after incubation. During the 12-h incubation, the proportions of low molecular weight peptides increased gradually, and total free amino acid concentration increased 9.84-fold. Additionally, seven phenolics were detected in free and bound forms, and the incubation led to increased levels of most phenolics. Moreover, both the two phenolic fractions from incubated DAB, particularly the free fraction, demonstrated greater total phenolic content and antioxidant properties than those of non-incubated DAB. Consequently, incubation was an efficient approach to biologically modify DAB, which further enhanced the health benefits and utilization of the bran.
Lopez-Moreno, Hector S.Ramirez, KarinaRochin-Medina, Jesus J.
7页
查看更多>>摘要：The coffee beverage market produces large amounts of waste as spent coffee grounds (SCGs). This by-product contains a high concentration of bioactive compounds that could be more accessible after bioprocessing. In this study, we identified the compounds present in Bacillus clausii-fermented SCG extract and determined the phenolic content and antioxidant activity of the extract. Additionally, in a macrophage model, we measured nitric oxide (NO) production and bactericidal activity against Salmonella enterica Typhimurium. The fermented SCG extract exhibited increased phenolic and flavonoid contents and antioxidant activity as compared to nonfermented SCG extract. The main compounds detected in fermented SCG extracts were cryptochlorogenic, caffeic, and chlorogenic acids. Macrophages RAW264.7 treated with 10, 50, or 100 mu g/mL of fermented SCG exhibited significantly (P < 0.001) reduced NO production and showed no cytotoxic effects. Salmonella-infected macrophages treated with 50, 100, or 300 mu g/mL of fermented SCG extracts exhibited 100% bactericidal efficacy after the first hour of infection up to 24 h. These results suggest that B. clausii-fermented SCG extract has a high antioxidant activity and may favor and enhance activation of macrophages against bacterial infections such as Salmonella enterica Typhimurium.
查看更多>>摘要：The effects of different dual frequency ultrasound treatment (DFUT) times (0, 2, 4, 6 and 8 min) on the structure of myofibrillar protein (MP) were investigated. Moreover, the effects of MP structure changes after DFUT on the stability and distribution of baicalein (BN) in emulsion were also evaluated. Results indicated that mild DFUT (<= 6 min) promoted the unfolding of MP, thus increasing active sulfhydryl content (ASC), zeta-potential, and surface hydrophobicity (SUH). Moreover, secondary structure results showed that mild DFUT transformed MP from an a-helix to a beta-sheet. Notably, the change of MP structures promoted the formation of stable emulsion, thus increasing the encapsulation efficiency (EEC) of BN in continuous phase. Also, BN in emulsion showed better storage stability and thermal stability after treatment. Overall, DFUT-modified MP can be used to establish a stable emulsion system, and it can be applied in embedding hydrophobic BN.
Victoria Alvarez, MariaFlorencia Bambace, MariaQuintana, GabrielGomez-Zavaglia, Andrea...
8页
查看更多>>摘要：The increased popularity of vegetarianism, lactose intolerance, and the high cholesterol content of dairy products are all factors that have recently increased the demand for non-dairy probiotic foods. This study aimed to evaluate the effect of probiotic supplementation of fresh-cut apple coated with alginate-prebiotic on its nutritional, safety, and sensory characteristics. Also, probiotic viability during refrigerated storage and after simulated gastrointestinal digestion (GID) was evaluated. A new non-dairy probiotic food was developed by adding prebiotics (oligofructose and inulin) and probiotic cultures (Lactobacillus rhamnosus and Bifidobacterium animalis subsp. lactis) to fresh-cut apple. Both probiotics successfully remained above 9.0 log CFU/g in the product after 8 days of storage. Also, high viability retention was achieved after GID with 7.8 and 8.0 log for L. rhamnosus and B. lactis, respectively, without significant effect of prebiotic addition. Microbiological and nutritional quality were maintained, however only those samples with prebiotics and B. lactis remained sensorially acceptable after 8 d. Furthermore, both probiotics exerted bactericidal effect against L. innocua inoculated on apple cubes with reductions higher than 1.8 log meanwhile, the effect on E. coli O157:H7 was less pronounced. Thereby, apple pieces coated with prebiotic-alginate solution constitute a promising alternative to design new carriers for probiotic bacteria.
查看更多>>摘要：gamma-Amino butyric acid (GABA)-producing Lb. brevis 145 solely or as a co-culture with Streptococcus thermophilus 1275 was used to ferment 4% soy protein isolate (SPI) medium supplemented with glucose, fructose, galactose, lactose, sucrose or maltose to understand the mechanism of GABA production in the presence of mono-sodium glutamate (MSG). GABA production, remanent MSG, sugar utilization by the two organisms, lactic acid production at different fermentation time points (0 h, 7 h, 24 h, 48 h) were determined. Moreover, pH in mono-culture and co-culture groups was monitored during 48 h of fermentation. Further, HCl, lactic acid, or acetic acid was added separately to adjust the pH of the medium to 4.5 to determine whether pH was a crucial factor for GABA synthesis. S. thermophilus 1275 and Lb. brevis 145 showed different preference to various sugars in SPI medium. The co-culture exhibited enhanced sugar utilization, lactic acid production, improved GABA production and a decrease in MSG level during soymilk fermentation. Importantly, there was a weak correlation between GABA production and sugar utilization, rather it was the acidic environment created by lactic acid production by S. thermophilus from carbohydrate catabolism that influenced gadA activity in Lb. brevis 145 in order to improve GABA production.
查看更多>>摘要：The influence of relative humidity of hot air on the finger citron slices drying characteristics, properties and aroma during microwave drying process was investigated. A new microwave drying system with relative humidity control was developed. Three levels of relative humidity of hot air, 20%, 40%, 60% of material with the temperature of 70 degrees C were set in the experiments, with comparation under temperature of 70 degrees C without fixed relative humidity for hot air. Results showed that Page and Midilli et models were selected to predict the drying behavior within the experimental range with the highest R-2. Samples dried under relative humidity 20% of hot air had the shortest drying time, highest rehydration ratio and porous structure. Samples dried under relative humidity 40% of hot air had the best color and aroma. Relative humidity 40%, 60% of hot air could provide better product quality than drying without relative humidity, followed by 20% and 60% of hot air. The relative humidity 40% of hot air should be a compromise proposal.
查看更多>>摘要：This study aimed to investigate the effect of oxidation on free amino acids and their derivatives in tea. Oolong tea samples, oxidized for 0, 10, 30, and 60 min, green tea, and black tea were produced from the same batch of fresh tea leaves. Effects of shooting periods on free amino acids and their derivatives were also evaluated in this study. Free amino acids and their derivatives were extracted with water and analyzed by LC-MS/MS. It was observed that total amino acid content of teas in the first shooting period (16231 +/- 241 mu g/g-31391 +/- 2034 mu g/g) was higher than the second (9635 +/- 379 mu g/g-11665 +/- 426 mu g/g) and third (13937 +/- 360 mu g/g-17661 +/- 1359 mu g/g) shooting periods. Content of most amino acids including gamma aminobutyric acid (GABA) in black and oolong teas were higher than those of green tea. However, theanine contents of black and oolong teas were lower than that of green tea. Kynurenine, kynurenic acid, quinolinic acid, dopamine, tyramine, phenylethylamine and tryptamine were found in all tea samples. Kynurenic acid content was the highest (1 + 0.1 mu g/g-3+0.4 mu g/g) in green, oolong and black tea samples. Concentrations of kynurenine, kynurenic acid, quinolinic acid, and dopamine were mostly found to be higher in green tea than black tea.
Kim, Yoon-SuLee, JungminHeo, SojeongLee, Jong-Hoon...
5页
查看更多>>摘要：Bacillus coagulans can be used as a probiotic or starter strain in fermented foods if it meets certain safety and phenotypic requirements. Here, we assessed the presence of toxin genes, the hemolytic activity, and the anti-biotic resistance of 31 B. coagulans strains isolated from rice straw. No toxin genes were found in any of the strains, and none exhibited alpha- and beta-hemolytic activity. Antibiotic resistance was determined using the minimum inhibitory concentration test and all the strains were susceptible to ampicillin, chloramphenicol, clindamycin, erythromycin, gentamicin, streptomycin, tetracycline, and vancomycin. Most of the strains showed protease and lipase activities and acid production on agar in the absence of added NaCl, and showed antibacterial activity against six common foodborne pathogens. Through these assessments, three strains-ASRS110, ASRS214, and ASRS217-were selected as the most applicable in terms of their functional properties. Among them, 95.7% of cells of strain ASRS217 formed spores after heat treatment. All the B. coagulans strains used in the current study have safe status, but we confirmed the necessity of characterization of functional properties of B. coagulans for starter development because the functional properties are strain-specific.
查看更多>>摘要：Predictive models describing the kinetics of fungal growth and thus the risk of mycotoxin formation in mass of grain are promising prognostic tools that may be used in postharvest management systems. In the study an artificial neural network (ANN) based on the multilayer perceptron (MLP) topology was used to evaluate the fungal population in barley grain stored under different temperature and water activity conditions (T = 12-30 degrees C and a(w) = 0.78-0.96). The impact of the number of neurons in the hidden layer and the type of activation functions in neurons of the hidden and output layers on the model prediction quality were analysed. The best architecture was the network containing five neurons in the hidden layer and the hyperbolic tangent function in neurons of the hidden layer and the linear one in the output. Statistical criteria used to evaluate the model performance showed its high precision and prediction accuracy. The results indicate that ANNs may be useful tools in predictive modelling of fungal development in a bulk of stored grain that may be used in postharvest management systems.
NSTL
Elsevier