Food nanoparticles from rice vinegar: isolation, characterization, and antioxidant activities

Abundant nanostructures have been constantly found in various foods, like vinegar, tea, coffee, and milk. However, these structures largely remain unexplored and even been eliminated for stability reasons in food industry. Here we report the isolation, characterization, and antioxidant activities of food nanoparticles (NPs) carrying polyphenols from Chinese rice vinegar. Using a gel-chromatography-based isolation protocol, the vinegar was separated into three major fractions. They were identified as spherical NPs (P1), lollipop-like NPs (P2) and spherical microparticles (P3) with average hydrodynamic diameter of 210, 245,1643 nm, separately. The former two fractions accounted for the major parts of dry matter in the vinegar. The P1-NPs fraction was composed of proteins, carbohydrates, and a high number of polyphenols (15 wt%), demonstrated potent antioxidant activity as determined by ABTS and ORAC assays. Moreover, they effectively quenched peroxyl free radicals in peritoneal macrophages and promoted cellular growth. The P2 fraction contained majority of organic acids, esters and mineral elements of the vinegar. It demonstrated the NPs are bioactive units of the rice vinegar, inspiring the development of novel functional nanomaterials with nutraceutical and pharmaceutical applications.

Rice vinegar removes Candida albicans from denture acrylic resins

Denture stomatitis, mainly caused by Candida albicans, often affect denture wearers. To manage these patients, denture hygiene is of utmost importance. There is a need for low cost, easily accessible denture disinfectants. To investigate the efficacy of rice vinegar and other disinfecting solutions in removing C. albicans from acrylic resins. Hundred and eighty acrylic resin plates were contaminated with C. albicans strains and divided into five groups. These were immersed in apple cider vinegar (ACV), white wine vinegar (WWV), rice vinegar (RV), chlorhexidine (CHX), and sterile distilled H2O (control). The plates were incubated at room temperature for 30 minutes, 1 hour and 8 hours. Candida removing ability of the disinfecting solutions was evaluated, and data was analyzed using two-way ANOVAwith Tukey post-test. Significance level of p< 0.05 was used. RV, ACV, WWV and CHX showed the highest efficacy (100%) in removing both C. albicans strains at 8 hours (p>0.05). CHX was the most effective disinfectant in removing both C. albicans strains at 30 minutes, 1 hour, and 8 hours (99%-100%). RV was as effective as ACV, WWV and CHX in removing C. albicans from acrylic plates at 8 hours.

Exercise or Dietotherapy Is Not Better than Returning to a Regular Diet to Rebuild Lipid Homeostasis of Rats

Our aim was to explore the effects of dietary and behavior interventions on lipometabolism caused by an unhealthy high-fat diet and the best method to rebuild lipid homeostasis of this lifestyle. Apart from normal diet rats, 34 rats were fed with high-fat emulsion for 4 weeks and then intervened for another 4 weeks. Eight of them were classified into high-fat control group, and 9 were sorted into high-fat diet with rice vinegar group. Meanwhile, 10 were put into high-fat diet in swimming group, and 7 were just for refeeding normal diet group. Then, the data of body weight was recorded and analyzed. Indexes of serum samples were tested by kits. AMPKα, HNF1α, and CTRP6 in pancreas, liver, cardiac, and epididymis adipose tissues were detected by western blot. According to our experiments, swimming and refeeding groups reflected a better regulation on lipid homeostasis mainly by upregulating the expression of pancreas AMPKα. To be more specific, the refeeding rats showed lower T-CHO ( P < 0.001 ) and LDL-C ( P < 0.05 ), but higher weight gain ( P < 0.001 ), insulin level ( P < 0.01 ), and pancreas AMPKα ( P < 0.01 ) than high-fat control rats. Compared with rats intervened by swimming or rice vinegar, they showed higher weight gain ( P < 0.001 ), insulin level ( P < 0.01 ), and HNF1α, but lower of CTRP6. In summary, refeeding diet functioned better in regulating the lipometabolic level after high-fat diet. Whatever approach mentioned above we adopted to intervene, the best policy to keep the balance of lipid homeostasis is to maintain a healthy diet.

Thai Rice Vinegars: Production and Biological Properties

Four types of traditional Thai rice—polished, black fragrant, glutinous and black glutinous rice—were separately used as raw material for vinegar production. During alcohol fermentation, using enriched baker’s dried yeast (S. cerevisiae) as a starter culture gave the highest ethanol content over 7 days of fermentation. The conversion of ethanol to acetic acid for vinegar production by Acetobacter pasteurianus TISTR 102 was performed for 25 days. The highest amount of acetic acid was detected with glutinous rice fermentation (6.68% w/v). The biological properties of Thai rice vinegars were determined, including the total phenolic content, antioxidant activity, antibacterial activity and cytotoxicity. Black glutinous rice vinegar exhibited the maximum total phenolic content of 133.68 mg GAE/100 mL. This result was related to the antioxidative activity findings, for which black glutinous rice vinegar exhibited the strongest activity against both ABTS•+ and DPPH• radicals. Cytotoxicity against the human colon cancer cell line (HT-29) provided an IC50 value of 74.02 μg/mL and weak activity in a mouse fibroblast normal cell line (L929) with an IC50 value of 171.06 μg/mL. Glutinous rice vinegar was the most effective vinegar for inhibiting pathogenic bacterial growth of both Gram-negative and Gram-positive bacteria. These results suggested that the value of total phenolic content corresponded to the anticancer activity and antioxidant activity results, while antibacterial activity depended on the acidity of rice vinegar.

Food-grade γ-aminobutyric acid production by immobilized glutamate decarboxylase from Lactobacillus plantarum in rice vinegar and monosodium glutamate system

Objectives γ-Aminobutyric acid (GABA) is a non-protein amino acid, considered a potent bioactive compound. This study focused on biosynthesis of food-grade GABA by immobilized glutamate decarboxylase (GAD) from Lactobacillus plantarum in the rice vinegar and monosodium glutamate (MSG) reaction system.Results The gene encoding GadB from L. plantarum has been heterologously expressed in Lactococcus lactis and biochemically characterized. Recombinant GadB existed as a homodimer, and displayed maximal activity at 40℃ and pH 5.0. The Km value and catalytic efficiency (kcat/Km) of GadB for L-Glu was 22.33 mM and 1.04 L/(mmol·s), respectively, with a specific activity of 24.97 U/mg protein. Then, purified GadB was encapsulated in gellan gum beads. Compared to the free enzyme, immobilized GadB showed higher operational and storage stability. Finally, 9.82 to 21.48 g/L of GABA have been acquired by regulating the amounts of catalyst microspheres ranging from 0.5 to 0.8 g (wet weight) in 0.8 mL of the designed rice vinegar and MSG reaction system. Conclusions The method of production GABA by immobilized GadB microspheres mixed in the rice vinegar and MSG reaction system is introduced herein for the first time. Especially, the results obtained here meet the increased interest in the harnessing of biocatalyst to synthesize food-grade GABA.