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1.
J Dairy Sci ; 103(1): 220-227, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31704015

RESUMO

This study was conducted to analyze the effect of milk types on the attributes of the glutinous rice wine-fermented yogurt-like product named Kouwan Lao (KWL). Four types of raw milks were used in this study, including high temperature, long time (HTLT: H milk), HTLT milk supplemented with 3% skim milk powder (S milk), pasteurized milk (P milk), and ultra-high temperature milk (U milk). Microbiological compositions of the fermented glutinous rice and KWL at different stages were analyzed using PCR-denaturing gradient gel electrophoresis and gene sequencing based on 16S rRNA and 26S rRNA. The physicochemical properties of KWL samples were determined, and textural properties of those were analyzed using a texture analyzer (Jiawei Innovation and Technology Co. Ltd., Zhejiang Province, China). The microstructure of KWL samples was observed using scanning electron microscopy. The results showed that the milk types had significant influences on the bacterial composition of KWL. In the curdling process, the predominant bacteria of H, S, P, and U KWL samples were Lactobacillus brevis, Janthinobacterium sp., Lactobacillus casei, and Streptococcus agalactiae, respectively. In the ripening process, the main strains in H KWL were Enterococcus faecium and Pediococcus pentosaceus. Lactobacillus casei and Lactobacillus paracasei were the dominant bacteria of U KWL. Lactobacillus casei was the main strain of P KWL, and no bacteria were detected in S KWL. Saccharomyces cerevisiae was the dominant fungus of KWL, and no significant effect of milk types on fungal composition of KWL was found. The results of physicochemical properties showed that significant differences in protein contents were found in the KWL samples, and P KWL had the highest protein content. The fat content of U KWL was significantly higher than that of samples from the other 3 groups. The U KWL and P KWL showed lower moisture than that of the other 2 KWL samples. In addition, no significant difference in pH value was found in all samples. The results of texture analysis and microstructure showed that compared with other 3 types of KWL samples, the related mass parameters of U KWL were more advantageous and improved significantly with the increase of the heat treatment temperature of raw milk and the addition of skim milk powder. Our findings revealed the effects of milk types on microbial composition, physicochemical properties, textural properties, and microstructure of KWL, and provided a basic theory for the optimization and industrial production of KWL.

2.
Foodborne Pathog Dis ; 2019 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-31755743

RESUMO

Polyphenols are a group of active ingredients in olive oil, and have been reported to exhibit antioxidant activity. Salmonella enterica subsp. enterica serovar Typhimurium (Salmonella Typhimurium) and Staphylococcus aureus are common foodborne pathogens causing serious infections and food poisoning in humans. This study was conducted to analyze the antibacterial activity of olive oil polyphenol extract (OOPE) against Salmonella Typhimurium and S. aureus, and reveal the possible antibacterial mechanism. The antibacterial activity was estimated using minimum inhibitory concentration (MIC) values and bacterial survival rates when treated with OOPE. The antibacterial mechanism was revealed through determinations of changes in intracellular ATP concentration and cell membrane potential, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and transmission electron microscopy analysis. The results showed the MICs of OOPE against Salmonella Typhimurium and S. aureus were 0.625 and 0.625-1.25 mg/mL, respectively. The growth of Salmonella Typhimurium and S. aureus (∼8 log CFU/mL) was completely inhibited after treatments with 0.625 mg/mL of OOPE for 3 h and 0.625-1.25 mg/mL for 5 h, respectively. When Salmonella Typhimurium and S. aureus were exposed to OOPE, the physiological functions associated with cell activity were destroyed, as manifested by reduction of intracellular ATP concentrations, cell membrane depolarization, lower bacterial protein content, and leakage of cytoplasm. These findings suggested a strong antibacterial effect of OOPE against Salmonella Typhimurium and S. aureus, and provided a possible strategy of controlling contamination by these two pathogens in food products.

3.
Front Microbiol ; 10: 1586, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31396167

RESUMO

Olive oil polyphenol extract (OOPE) has been reported to have antibacterial activity; however, its effect on Listeria monocytogenes is less studied so far. This study, thus, aimed to reveal its antimicrobial activity and action approach against L. monocytogenes via evaluating the minimum inhibitory concentration (MIC) as well as the changes of intracellular adenosine 5'-triphosphate (ATP) concentration, cell membrane potential, bacterial protein, DNA, and cell morphology. The results showed that OOPE could inhibit the growth of L. monocytogenes with a measured MIC of 1.25 mg/ml. L. monocytogenes cells treated by OOPE showed significant reduction in intracellular ATP concentrations, bacterial protein, or DNA (p < 0.05), in comparison with those without any treatment. In addition, OOPE was observed to depolarize strain cells and alter cell morphology, resulting in damaged cell membrane and, thereby, leakage of cell fluid. These findings demonstrated that OOPE had inhibition on L. monocytogenes via its action on cells, suggesting its potential as a natural preservative.

4.
Front Psychol ; 10: 612, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30971977

RESUMO

The present study tested whether students' autonomous motivation mediated the association between adult support (parental autonomy support, teacher support) and students' homework effort. A sample of 666 Chinese middle school students was recruited to complete the parental autonomy support questionnaire, teacher support questionnaire, homework autonomous motivation questionnaire and homework effort questionnaire. Structural equation modeling showed that both parental autonomy support and teacher support positively predicted mathematics homework effort, and mathematics homework autonomous motivation was a mediator in these associations. The present study reveals the importance of adult support and autonomous motivation, and has theoretical and practical implications.

5.
J Dairy Sci ; 102(5): 3894-3902, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30852028

RESUMO

This study was conducted to analyze the antibacterial effect of olive oil polyphenol extract (OOPE) against vegetative cells of Bacillus cereus isolated from raw milk and reveal the possible antibacterial mechanism. The diameter of inhibition zone, minimum inhibitory concentration, minimum bactericidal concentration, and survival counts of bacterial cells in sterile normal saline and pasteurized milk were used to evaluate the antibacterial activity of OOPE against B. cereus vegetative cells. The changes in intracellular ATP concentration, cell membrane potential, content of bacterial protein, and cell morphology were analyzed to reveal possible mechanisms of action. Our results showed the diameter of inhibition zone, minimum inhibitory concentration, and minimum bactericidal concentration of OOPE against B. cereus vegetative cells were 18.44 ± 0.55 mm, 0.625 mg/mL, and 1.25 mg/mL, respectively. Bacillus cereus GF-1 vegetative cells were decreased to undetectable levels from about 8 log cfu/mL after treatments with 0.625 mg/mL of OOPE in normal saline at 30°C for 3 h and in pasteurized milk at 30°C for 10 h. The antibacterial mechanisms of OOPE against B. cereus GF-1 vegetative cells may be due to the reduction of intracellular ATP concentrations, cell membrane depolarization, decrease of bacterial protein content, and leakage from cytoplasm. These findings illustrated that OOPE could be used to prevent the growth of contaminating B. cereus cells in dairy products.


Assuntos
Antibacterianos/farmacologia , Bacillus cereus/efeitos dos fármacos , Leite/microbiologia , Azeite de Oliva/química , Extratos Vegetais/farmacologia , Polifenóis/farmacologia , Animais , Bacillus cereus/fisiologia , Microbiologia de Alimentos , Testes de Sensibilidade Microbiana , Polifenóis/isolamento & purificação
6.
J Food Prot ; : 456-460, 2018 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-29474142

RESUMO

Cronobacter species (formerly Enterobacter sakazakii) are emerging opportunistic bacterial pathogens that can infect both infants and adults. This study was conducted to isolate and genotype diverse Cronobacter species from drinking water, chilled fresh pork, powdered infant formula, instant noodles, cookies, fruits, vegetables, and dishes in Northeast China and to evaluate the antibiotic resistance and susceptibility of the isolates. Thirty-four Cronobacter strains were isolated and identified: 21 C. sakazakii isolates (61.8%), 10 C. malonaticus isolates (29.4%), 2 C. dublinensis isolates (5.9%), and 1 C. turicensis isolate (2.9%). These isolates were further divided into 15 sequence types (STs) by multilocus sequence typing. C. sakazakii ST4 (10 isolates, 29.4%), ST1 (3 isolates, 8.8%), and ST8 (3 isolates, 8.8%) and C. malonaticus ST7 (four isolates, 11.8%) were dominant. Antibiotic susceptibility testing indicated that all 34 Cronobacter isolates were susceptible to ampicillin-sulbactam, cefotaxime, ciprofloxacin, gentamicin, meropenem, tetracycline, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole, 88.2% were susceptible to chloramphenicol, and 67.6% were resistant to cephalothin. The results of this study enhance knowledge about genotyping and antibiotic resistance of these Cronobacter species and could be used to prevent potential hazards caused by these strains in drinking water and various food products.

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