Acyl ascorbates were synthesized through the condensation of L-ascorbic acid with various fatty acids using an immobilized lipase in water-miscible organic solvent, and their antioxidative properties on lipid oxidation in bulk, disperse and microcapsule systems were examined. The optimal conditions for enzymatic synthesis in a batch reaction were determined and the continuous production of acyl ascorbate was conducted using a continuous stirred tank reactor and a plug flow reactor. The oxidative stability of lipid with saturated acyl ascorbate in bulk system increased with increasing acyl chain length, whereas that in the oil-in-water emulsion and microcapsule system depended on the acyl chain length and the concentration of the ascorbate.
Esterases are biocatalysts in food industry aimed for nutrition improvements, formation of flavor, and food fermentation. Two esterases EstGX1 and EstGX2 were identified based on function-based screening of a soil metagenomic cosmid library. Enzyme properties including optimum pH, optimal temperature, tolerance to organic solvents and metal ions were measured, respectively. The activity of EstGX2 could maintain about 40% after incubated at 99°C for 55 min, and could be increased in presence of 15% ethanol. The unique properties of EstGX2, high thermostability and stability in the presence of several organic solvents, may make it a promising enzyme candidate in food industry.
A convenient and environmentally friendly method was developed for extraction and enrich of Sudan I from tomato sauce and chilli products. The method is based on an ultrasound-assisted dispersive liquid-liquid microextraction with solidification of floating organic drop (UADLLME-SFO) after a preliminary QuEChERS procedure, which was followed by high performance liquid chromatography with photodiode array detection (HPLC-PAD). The several parameters involved in the UADLLME-SFO step was optimized. The optimal variables obtained were 30 µL of 1-dodecanol as the extraction solvent, 1.0 mL of acetone as disperse solvent, ultrasonic irritation for 15 min, and no salt addition. Under the optimum conditions, the limit of detection for Sudan I was as low as 1.5 µg kg−1. The recoveries obtained was between 79% and 92% (RSD, 4.8% – 7.1%, n = 7). The proposed method was successfully applied to the determination of Sudan I in four kinds of real samples.
Two rhamnogalacturonan acetylesterase genes, designated as Asrgae1 and Asrgae2, were isolated from a shoyu koji mold, Aspergillus sojae KBN1340, and characterized. Asrgae1 comprised 793 bp, encoding 248 amino acids with a predicted molecular mass of 26,092 Da, interrupted by a single putative intron of 46 bp in length. The mature AsRgae1 of 232 amino acids had a calculated molecular mass of 24,415 Da. The coding region of Asrgae2 was determined to be 777 bp in length with no introns. The predicted protein of 258 amino acids had an estimated molecular mass of 26,902 Da. The mature AsRgae2 of 238 amino acids had a calculated molecular mass of 25,015 Da. Utilizing the A. oryzae taaG2 gene promoter and the A. oryzae taaG3 gene terminator, AsRgae1 and AsRgae2 were successfully expressed in A. oryzae and secreted into the culture medium. AsRgae1 and AsRgae2 had a molecular mass of 28.0 kDa and 33.0 kDa, respectively.
In this study, an optimized method was developed to detect Salmonella by using immunomagnetic separation coupled with culture to selective agar (IMS/culture). To test the effectiveness of the methods and develop a rapid and sensitive detection procedure, direct culture, IMS/culture, and multiplex PCR (mPCR) were compared for the detection of Salmonella in 700 food samples. After selective enrichment, all samples were (I) subjected to direct culture, plated on xylose-lysine-tergitol 4 agar, and identified as Salmonella via biochemical and serological methods; (II) subjected to IMS then identified as (I); and (III) subjected to DNA extraction and mPCR analysis. A total of 83, 95, and 104 samples were found positive for Salmonella by direct culture, IMS/culture, and mPCR, respectively. Results suggested higher sensitivity in mPCR than in direct culture and IMS/culture methods. IMS/culture increased the detection rate of Salmonella and compared well with mPCR. This study demonstrated that the use of mPCR in pre-screening of samples and further identification by IMS/culture should enhance the positive identification and increase the number of isolates of Salmonella.
The present study demonstrated the anti-diabetic activities of Chinese purple yam flesh and peel extracts. Results showed that the ethyl acetate fraction of purple yam extracts could efficiently inhibit the activities of two key diabetes-related enzymes, α-amylase and α-glucosidase, and the non-enzymatic glycation which might lead to the pathogenesis of diabetic complications. On the other hand, the extracts exhibited excellent ability in alleviating free fatty acid-induced oxidative stress and insulin resistance in HepG2 cells. In addition, purple yam peel exerted better effects than the flesh, and more attention should be payed for its value in the prevention and treatment of diabetes and related diseases.
The study aimed to isolate and characterize probiotic strains with potential cholesterol degrading activity. Fourteen lactic acid bacteria isolated from lamb meat were screened on mineral salt agar supplemented with 0.2% cholesterol (MSC agar). Cell-free supernatants (CFSs) of these isolates were used as a crude source of extracellular cholesterol degrading enzymes. CFSs of GMK01, GMK02 and GMK03 isolates displayed high ability to degrading cholesterol (86.4, 86.1 and 84.6%, respectively). These isolates were identified as Lactobacillus sakei GMK01, Lactobacillus rhamnosus GMK02 and Leuconostoc mesenteroides GMK03. Strains were resistant to low acidity (pH 2.5) and bile salts (0.3%), able to adhesion to Caco-2 cells and have low rate of antibiotic resistance. Living cells of these strains were able to degrade cholesterol in MSC broth even after treatment with simulated gastrointestinal juice. The maximum cholesterol degradation (about 90%) was obtained on the third day. 4-cholesten-3-one was detected as a degradation product of cholesterol by Leuconostoc mesenteroides GMK03. The studied strains degrade cholesterol by different mechanisms and may suggest a new possibility for the mechanism underlying cholesterol degradation by LAB. In conclusion, the isolated strains could be suggested as potential pharmaceutical probiotic strains for food industry and human nutrition.
Free radical scavenging activities of two series of tripeptide libraries were investigated using ABTS, DPPH, and ORAC assays. Two Tyr-containing tripeptides showed higher scavenging activities against the hydrophilic ABTS and AAPH radicals than two His-containing tripeptides, showing that Tyr residues play important roles in free radical scavenging activity. Higher concentrations of tripeptides were required to reveal apparent DPPH radical scavenging activity. The antioxidant activities of the tripeptide libraries obtained from this study were compared with previous results obtained using several assays, including antioxidant activity against the peroxidation of linoleic acid, FRAP assay, and peroxynitrite (PN) scavenging activity. The antioxidant activity of the tripeptides against the peroxidation of linoleic acid showed high correlations with the ABTS and ORAC assays (correlation coefficients (R) = 0.725 and 0.731, respectively), and low correlations with FRAP, PN scavenging, and DPPH assays. The highest correlation was found between the ABTS and ORAC assays (R = 0.905).
Deterioration of swallowing function leads to the risk of aspiration pneumonia mortality. In elderly persons, decreased secretion of substance P (SP) from the oral and bronchial mucosae can lead to reduced swallowing function. Capsaicin has been reported to increase SP secretion and enhance swallowing function. We formulated orally disintegrating (OD) tablets consisting primarily of ginger, which contains the same vanillin derivatives as capsaicin, and performed pharmaceutical evaluation and a clinical study to assess the effect of ginger on swallowing function. OD tablets containing ginger increased the amount of SP in saliva immediately after oral ingestion, and showed a significantly higher concentration of SP in saliva between 15 and 120 min after oral ingestion as compared to placebo. Our results suggest that OD tablets containing ginger are likely to increase the amount of SP in saliva after oral ingestion and enhance swallowing function.
Texture characteristics and antioxidant activities (AOA) of extrudates were stored under different conditions that were detected by texture profile analysis (TPA) and DPPH* method in this study. The physicochemical properties of extrudates were significantly affected by storage time and temperature. The hardness values of extrudates stored at 0°C were the highest, while the crispness values of it were the lowest. The AOA decreased significantly from 20.23% to 14.87% with temperature increasing from −10°C to 25°C. The back propagation Artificial Neural Network (bp-ANN) was used to predict the AOA from hardness and crispness. The optimized model structures had two hidden layers, one with ten neurons per layer (R2 ≥ 0.999) and another one with eight neurons per layer (R2 ≥ 0.993). The ANN model was a better predictor of AOA from texture characteristics than linear fitting model (AOA vs. hardness: R2 = 0.913; AOA vs. crispness: R2 =0.952).
Soy β-conglycinin (βCG) consumption has been shown to improve insulin resistance and suppress diet-induced obesity. These physiological effects seem to be mediated by the normalization of adiponectin and insulin sensitivity. Here, we show that artificial enzyme-hydrolyzed βCG peptides promote uptake of 2-deoxyglucose, a glucose analogue, accompanied by translocation of glucose transporter 4 in skeletal L6 myotubes. Inhibition of AMP-activated protein kinase (AMPK) attenuated βCG peptides-induced glucose uptake activity, while inhibition of both insulin and nitrogen monoxide signaling did not affect the glucose uptake activity. Taken together, these results indicate that βCG peptides directly induced glucose uptake through the AMPK signaling pathway in muscle cells and might function to prevent insulin resistance.
The rutin content of dough made with ‘Manten-Kirari’, a new Tartary buckwheat variety with trace-rutinosidase activity and minimal bitterness, was assessed in a time course study of rutin hydrolysis in doughs with various water contents and blending ratios of Tartary buckwheat flour. In the normal rutinosidase variety, ‘Hokkai T8’, the majority of rutin was hydrolyzed within 30 min of water addition, whereas about 90% of rutin remained in ‘Manten-Kirari’. We also investigated the residual rutin ratio in white bread, butter enriched roll, pound cake and galette. With ‘Hokkai T8’, rutin was hydrolyzed almost completely in all foods tested, whereas 88.5%, 49.8%, 31.0% and 26.2% of rutin remained in ‘Manten-Kirari’-containing pound cake, white bread, butter enriched roll and galette, respectively. Also, ‘Hokkai T8’ bread exhibited strong bitterness, whereas ‘Manten-Kirari’ foods showed minimal bitterness. These results indicate that ‘Manten-Kirari’ is a promising material for the production of rutin-rich food products without bitterness.
Protease from lactic acid bacteria is of great importance to flavor and texture quality of fermented foods. An acidic protease from Pediococcus pentosaceus 220 was purified to homogeneity with a 11.5-fold increase in specific activity and 13.4% of recovery by precipitation with ammonium sulfate (20 – 60%, w/v), DEAE-Sepharose CL-6B ionic exchange chromatography, and Sephadex G-75 gel filtration chromatography. The molecular weight of the purified protease was estimated to be 37 kDa by Sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The optimum pH and temperature for protease activities were around pH4.0 and 35°C, respectively. The enzyme was stable at 20 – 40°C and showed pH stability between 4.0 and 7.0. The protease was activated by Ca2+, but inhibited by Zn2+, Mg2+ and Fe3+. The enzyme activity was also strongly inhibited by Sodium dodecyl sulfate and EDTA. It could be deduced that the purified enzyme was an acidic metalloprotease.
We have reported that the inactivation effect of carbonation with heating (CH; 80°C, 5 MPa, 30 min) on Bacillus subtilis spores was enhanced by the addition of monoglycerol-caprate (MC10). The aim of this study was to obtaine aspects of the mechanism of this enhanced inactivation. The addition of MC10 (0.05%) to spores suspended in nutrient broth (NB) at pH 3.2 increased the inactivation of spores by heating (HT, 80°C) alone and with pressurization (5 MPa nitrogen gas). However, no inactivation effect was observed in NB at pH 6.8. The results showed that MC10 increased the number of spores with decreased resistance to heat and pressure under acidic conditions. The addition of MC10 also enhanced the ratio of spores germinated by CH. The bacteriostatic effect of MC10 was enhanced when combined with CH. This enhanced bacteriostatic effect might be responsible for inducing the high inactivation effect of CH with MC10.
Soy-seasoned salmon roe products are commonly eaten in Japan; long-term preservation of these items requires refrigeration. However, salmon roe products are often contaminated with Listeria monocytogenes, which can potentially cause outbreaks of listeriosis. This study focused on developing a method to inhibit the growth of L. monocytogenes in salmon roe products by treating these foodstuffs with a combination of nisin and commercial pectin-hydrolysate, Neupectin L. We determined that treatment with 0.5 mg g−1 nisin completely inhibited the growth of L. monocytogenes in raw salmon roe. However, treatment with nisin alone did not inhibit L. monocytogenes in soy-seasoned salmon roes. Further work showed that combined treatment with 0.5 mg g−1 nisin and 0.5% Neupectin L completely inhibited the growth of L. monocytogenes during incubation at 12°C. Therefore, this combination is an alternative way to control L. monocytogenes growth in salmon roe products.