Production of benzoic acid as a natural compound in fermented skim milk using commercial cheese starter.

In this study, we investigated the production of natural benzoic acid (BA) in skim milk fermentation by 5 kinds of commercial cheese starters. Five kinds of starter were inoculated into 10% reconstituted skim milk, and then the culture was incubated at 2-h intervals for 10 h at 30, 35, and 40°C. In fermentation by MW 046 N+LH 13, the starter for making raclette, BA was highly detected after 8 h at 30 and 35°C. In fermentation by LH 13, the starter for making berg, BA steadily increased and was highly detected at 40°C. In fermentation by TCC-3+TCC-4, the starter for making Caciocavallo and mozzarella, BA was detected after 2 h at 40°C. Also, BA was detected after 4 and 8 h at 35 and 30°C, respectively. In fermentation by Flora-Danica, the starter for making Gouda, BA was increased until 6 h and decreased after 6 h at all temperatures. Among the 5 kinds of fermentation, the level of BA was the highest in fermentation by Flora-Danica at 6 h at 35°C, at 14.55 mg/kg.

Short communication: Change of naturally occurring benzoic acid during skim milk fermentation by commercial cheese starters.

This study sought to investigate the change of naturally occurring benzoic acid (BA) during skim milk fermentation by 4 kinds of commercial cheese starters used in domestic cheese. The culture was incubated at 3-h intervals for 24h at 30, 35, and 40°C. The BA content during fermentation by Streptococcus thermophilus STB-01 was detected after 12h at all temperatures, sharply increasing at 30°C. In Lactobacillus paracasei LC431, BA was detected after 9h at all temperatures, sharply increasing until 18h and decreasing after 18h at 30 and 35°C. In the case of R707 (consisting of Lactococcus lactis ssp. lactis and Lactococcus lactis ssp. cremoris), BA increased from 6h to 15h and decreased after 15h at 40°C. The BA during STB-01 and CHN-11 (1:1; mixture of S. thermophilus, Lc. lactis ssp. lactis, Lc. lactis ssp. cremoris, Lc. lactis ssp. diacetylactis, Leuconostoc mesenteroides ssp. cremoris) fermentation was detected after 3h at 35 and 40°C, sharply increasing up to 12h and decreasing after 15h at 35°C, and after 6h, increasing up to 9h at 30°C. After 3h, it steadily decreased at 40°C. The highest amount of BA was found during the fermentation by R707 at 30°C; 15h with 12.46mg/kg.

Evaluation of Natural Food Preservatives in Domestic and Imported Cheese.

In milk and milk products, a number of organic acids naturally occur. We investigated the contents of some naturally occurred food preservatives (sorbic acid, benzoic acid, propionic acid, nitrite, and nitrate) contained in domestic and imported cheeses to establish the standard for the allowable range of food preservatives content in cheese. 8 kinds of domestic precheeses (n=104), 16 kinds of domestic cured cheeses (n=204) and 40 kinds of imported cheeses (n=74) were collected. Each domestic cheese was aged for a suitable number of months and stored for 2 mon at 5℃ and 10℃. No preservatives were detected in domestic soft and fresh cheeses, except cream cheese. In case of semi-hard cheeses, 2-5 mg/kg of benzoic acid was detected after 1-2 mon of aging. In imported cheeses, only benzoic acid and propionic acid were detected. The average benzoic acid and propionic acid contents in semi-hard cheese were 8.73 mg/kg and 18.78 mg/kg, respectively. Specifically, 1.16 mg/kg and 6.80 mg/kg of benzoic acid and propionic acid, respectively, were contained in soft cheese, 3.27 mg/kg and 2.84 mg/kg, respectively, in fresh cheese, 1.87 mg/kg and not detected, respectively, in hard cheese, and 2.07 mg/kg and 182.26 mg/kg, respectively, in blended processed cheese.

Benzoic Acid Production with Respect to Starter Culture and Incubation Temperature during Yogurt Fermentation using Response Surface Methodology.

Benzoic acid is occasionally used as a raw material supplement in food products and is sometimes generated during the fermentation process. In this study, the production of naturally occurring yogurt preservatives was investigated for various starter cultures and incubation temperatures, and considered food regulations. Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus paracasei, Lactobacillus reuteri, Lactobacillus plantarum, Bifidobacterium longum, Bifidobacterium lactis, Bifidobacterium bifidum, Bifidobacterium infantis, and Bifidobacterium breve were used as yogurt starter cultures in commercial starters. Among these strains, L. rhamnosus and L. paracasei showed the highest production of benzoic acid. Therefore, the use of L. rhamnosus, L. paracasei, S. thermophilus, and different incubation temperatures were examined to optimize benzoic acid production. Response surface methodology (RSM) based on a central composite design was performed for various incubation temperatures (35-44℃) and starter culture inoculum ratios (0-0.04%) in a commercial range of dairy fermentation processes. The optimum conditions were 0.04% L. rhamnosus, 0.01% L. paracasei, 0.02% S. thermophilus, and 38.12℃, and the predicted and estimated concentrations of benzoic acid were 13.31 and 13.94 mg/kg, respectively. These conditions maximized naturally occurring benzoic acid production during the yogurt fermentation process, and the observed production levels satisfied regulatory guidelines for benzoic acid in dairy products.

A new specific BACE-1 inhibitor from the stembark extract of Vitis vinifera.

A new resveratrol dimer, (+)-vitisinol E (1) which demonstrated inhibitory activity on BACE-1 (beta-site APP-cleaving enzyme 1) in vitro, was isolated from the stembark extract of Vitis vinifera (Vitaceae) together with four known resveratrol oligomers, (+)-epsilon-viniferin (2), (+)-ampelopsin A (3), (+)-vitisin A (4) and (-)-vitisin B (5). The chemical structure of 1 was established by MR spectroscopic analyses, including HMBC. All isolated resveratrol derivatives (1-5) demonstrated significant inhibition on baculovirus-expressed BACE-1 in a dose-dependent manner, which was assessed with the FRET assay using Rh-EVNLDAEFK as a substrate in vitro.

Sesquiterpenoids isolated from the flower buds of Tussilago farfara L. inhibit diacylglycerol acyltransferase.

Inhibition of acyl CoA:diacylglycerol acyltransferase (DGAT), which is a key enzyme in triglyceride synthesis in eukaryotic organisms, has been proposed as one of the drug targets for treating obesity, type II diabetes mellitus, and metabolic syndrome. Bioassay-guided fractionation of EtOH extract of the flower buds of Tussilago farfara , using an in vitro DGAT enzyme assay, resulted in the isolation of four known sesquiterpenoids, tussilagonone (1), tussilagone (2), 7beta-(3-ethyl-cis-crotonoyloxy)-1alpha-(2-methylbutyryloxy)-3,14-dehydro-Z-notonipetranone (3), and 8-angeloylxy-3,4-epoxy-bisabola-7(14),10-dien-2-one (4). DGAT1 inhibitory activity was studied by in vitro DGAT assay using rat liver microsomes and HepG2 cell microsomes. They showed DGAT1 inhibition with IC(50) values of 99.2 (1), 18.8 (2), 47.0 (3), and 211.1 (4) microM (for rat liver microsomes) and >1 mM (1), 49.1 (2), 160.7 (3), and 294.4 (4) microM (for HepG2 cell microsomes), respectively. Compound 2 showed the most potent inhibition against microsomal DGAT1 derived from rat liver and human hepatocellular carcinoma HepG2 cells and also significantly inhibited triglyceride synthesis by suppressing incorporation of [(14)C]acetate or [(14)C]glycerol into triglycerides in HepG2 cells. These findings suggest that tussilagone is a potential lead compound in the treatment of obesity and type 2 diabetes.

Vasorelaxant effect of stilbenes from rhizome extract of rhubarb (Rheum undulatum) on the contractility of rat aorta.

The vascular relaxant effect of the rhizome extract of Rheum undulatum was evaluated with isolated rat thoracic aorta preparations. The methanol extract of the rhizome induced a concentration-dependent relaxation of aortic preparations precontracted with 0.3 microm phenylephrine (EC50 value: 5.8 microg/mL). The activity-guided fractionation of the extract led to the isolation of seven hydroxystilbene components as active principles, i.e. piceatannol, resveratrol, desoxyrhapontigenin, rhapontigenin, piceid, rhaponticin and epsilon-viniferin. Of these, piceatannol, a tetrahydroxystilbene, exhibited the most potent vascular relaxant effect in rat aortic preparations (EC50 value 2.4 microm). The vasorelaxant effect of piceatannol on endothelium-intact aorta rings was diminished completely by the removal of functional endothelium or by pretreatment of the aortic tissues with N(G)-nitro-l-arginine methyl ester. These results suggest that piceatannol may be the major mediator responsible for the vasorelaxing properties of the rhizome extract of Rheum undulatum and the vasorelaxant effects of the piceatannol may be mediated via endothelium-dependent nitric oxide signaling pathway.

Vasorelaxant effect of the rootbark extract of Paeonia moutan on isolated rat thoracic aorta.

The vascular relaxant effect of the rootbark extract of Paeonia moutan was evaluated in isolated rat thoracic aorta. The methanolic extract of the rootbark showed a vasorelaxant activity in rat aortic preparations precontracted with 0.3 microM phenylephrine (IC50 value: 16.8 microg/mL). The activity-guided fractionation of the extract led to the isolation of five active principles such as paeoniflorin (1), paeonidanin (2), methylpaeoniflorin (4), tetragalloylglucose (5) and pentagalloylglucose (6), and these active ingredients potently relaxed phenylephrine-induced contraction of rat aortic preparations in a concentration-dependent manner (IC50 values: 19.4, 7.9, 10.1, 5.1 and 3.6 microM, respectively). These results suggest that pinane glycosides and galloylglucoses might be the components responsible for the vasorelaxant properties of the rootbark extract of P. moutan, and their vasorelaxant effects may be mediated through increases in the release of nitric oxide from endothelial cells.

Prevalence, antibiotic susceptibility, and virulence factors of Yersinia enterocolitica and related species from ready-to-eat vegetables available in Korea.

A total of 673 ready-to-eat vegetable samples were collected in Korea from 2001 to 2002 and analyzed for the presence of Yersinia spp. We analyzed biotypes, serotypes, and susceptibility to 12 antibiotics and tested for virulence genes of pathogenic Yersinia enterocolitica isolates by PCR assay. Among the samples, 27 (4.0%) were found to be contaminated with Yersinia spp. Among the 27 strains of Yersinia spp. isolates, 18 strains (66.7%) of Y. enterocolitica, 5 strains (18.5%) of Y. frederiksenii, 3 strains (11.1%) of Y. intermedia, and 1 strain (3.7%) of Y. kristensenii were identified. According to the serotypes of Y. enterocolitica isolates, O:3 (11.1%) and O:5 (11.1%) were the most predominant, followed by O:8 (5.6%) and others (72.2%). For biotypes of Y. enterocolitica isolates, 1A (77.8%) was the most predominant, followed by 3B (11.1%), 3 (5.6%), and 5A (5.6%). Also, an antibiotic susceptibility test showed that Y. enterocolitica isolates were very susceptible to the antibiotics tested but highly resistant to ampicillin (94%), cephalothin (100%), and carbenicillin (83%). PCR assays with specific primers derived from yst and ail genes of Y. enterocolitica were applied to confirm the presence of pathogenic Y. enterocolitica. Among the 18 strains of Y. enterocolitica isolates, only 3 strains (O:3/1A, UT/3B, and UT/1A isolated from Chinese cabbage, onion, and spinach, respectively) were shown to have a virulence gene.