Enhancing safety and quality of shrimp by nanoparticles of sodium alginate-based edible coating containing grapefruit seed extract.

Edible coatings are safe and effective in extending the shelf life of foods. In this study, a nanoparticle-based edible coating solution was prepared, containing alginate as a coating agent and grapefruit seed extract as an antibacterial agent to improve the safety and quality of shrimp during storage. Shrimp coated with this formulation were maintained at 4°C for 8 days, and periodically analyzed for changes in sensory, chemical [total volatile basic nitrogen (TVB-N) and pH] and microbial parameters. The uncoated shrimp exceeded the microbiological limits at 7.87 log CFU/g on Day 4 of storage, whereas the nanoparticle-based coated shrimp did not exceed the limit by Day 8 of storage. In addition, uncoated shrimp tended to maintain their quality, while uncoated shrimp deteriorated due to increased TVB-N values, pH values, and off-flavors. Nanoparticles are easily dispersed in food to minimize flavor impact and enhance diffusion and bioactivity. We concluded that the nanoparticles coating extended the shelf life of shrimp by more than 5 days. Therefore, the use of nanoparticle-based coatings could be a new and effective way to maintain shrimp quality.

Enhancing the antimicrobial activity of ginseng against Bacillus cereus and Staphylococcus aureus by heat treatment.

This study evaluated the antimicrobial activities [diffusion inhibition zone, minimum inhibitory concentration (MIC), and minimum bactericidal concentration], of heated ginseng extracts (ethanol and methanol). The extract yields, ginsenoside compositions, growth inhibitory effects against Bacillus cereus and Staphylococcus aureus and bacterial cell membrane potential changes, were also investigated. Methanol extracts of heated ginseng, showed higher antimicrobial activity than ethanol extracts. B. cereus was more easily inhibited than S. aureus. Ginseng heated at 100 °C for 2 and 16 h, showed maximum antimicrobial activity against B. cereus and S. aureus, respectively. In the growth inhibitory test, S. aureus and B. cereus were completely inhibited after 2 and 8 h culture at the MIC. The cell membrane potential decreased with increasing concentration of extract, indicating cell metabolism disruption. Ginsenosides Rg3, a potent antibacterial substance, which were absent in non-heated ginseng, were produced by heating ginseng at 100 °C for 4 and 8 h, respectively.

Effect of layer-by-layer antimicrobial edible coating of alginate and chitosan with grapefruit seed extract for shelf-life extension of shrimp (Litopenaeus vannamei) stored at 4 °C.

The effect of a layer-by-layer (LbL) electrostatic deposition coating of alginate and chitosan with grapefruit seed extract was investigated on the shelf life of shrimp (Litopenaeus vannamei) stored for 15 days under refrigeration (4 °C). The shrimp were periodically analyzed for changes in microbiological parameters (total aerobic mesophilic bacteria and total aerobic psychrotrophic bacteria counts), chemical parameters, melanosis, and sensory characteristics. The chitosan-alginate coating had the advantage of reducing the bacterial count by 2 log CFU in combination with the antimicrobial activity of the grapefruit seed extract. The bilayer coating reduced the off-flavor of shrimp during the storage period by preventing the odor of acetic acid that was used to dissolve chitosan. In conclusion, chitosan and chitosan-alginate treatments could prolong the shelf life of shrimp.

Preparation of Highly Purified Stearidonic Acid from Echium Oil via an Enzymatic Method Combined with Preparative High Performance Liquid Chromatography.

Stearidonic acid (SDA), an n-3 polyunsaturated fatty acid (PUFA), can be obtained from plant origin oils and it can be a good source of PUFA for vegetarians. SDA can be easily converted to longer PUFA such as docosahexaenoic acid and eicosapentaenoic acid. Highly purified stearidonic acid (SDA) was prepared successfully from echium oil via an enzymatic method combined with preparative high performance liquid chromatography. In the 1(st) step, SDA enrichment was accomplished using Candida rugosa lipase and 39.5% of SDA was obtained in the fatty acid fraction. Subsequently, the 1(st) reaction mixture was used for the 2(nd) enzymatic esterification without any separation process. The 2(nd) esterification was conducted for further SDA enrichment in a packed-bed reactor using Lipozyme RM IM from Rhizomucor miehei and the SDA content increased in a very short residence time. Ethanol was selected as an appropriate alcohol to react as an acyl receptor, and the other conditions for SDA enrichment were optimized at 20°C of temperature, and 1:4 of molar ratio (i.e., fatty acid to ethanol). Under these conditions, 51.6% of SDA was obtained in the fatty acid fraction after a residence time of 15 min. Finally, highly purified SDA (purity, >99%) was obtained by prep-HPLC using the SDA-rich fraction obtained from the two-step lipase-catalyzed esterification.

Evaluation of Genotoxicity of Water and Ethanol Extracts from Rhus verniciflua Stokes (RVS).

Rhus verniciflua Stokes (RVS), one of traditional medicinal plants in Asia, was found to have pharmacological activities such as antioxidative and antiapoptotic effects, raising the possibility for the development of a novel class of anti-cancer drugs. Thus, potential genotoxic effects of RVS in three short-term mutagenicity assays were investigated, which included the Ames assay, in vitro Chromosomal aberration test, and the in vivo Micronucleus assay. In Ames test, the addition of RVS water extracts at doses from 313 up to 5000 mg/plate induced an increase more than 2-fold over vehicle control in the number of revertant colonies in TA98 and TA1537 strains for detecting the frame-shift mutagens. The similar increase in reversion frequency was observed after the addition of RVS ethanol extracts. To assess clastogenic effect, in vitro chromosomal aberration test and in vivo micronucleus assay were performed using Chinese hamster lung cells and male ICR mice, respectively. Both water and ethanol extracts from RVS induced significant increases in the number of metaphases with structural aberrations mostly at concentrations showing the cell survival less than 60% as assessed by in vitro CA test. Also, there was a weak but statistically significant increase in number of micronucleated polychromatic erythrocytes (MNPCEs) in mice treated with water extract at 2000 mg/kg while ethanol extracts of RVS at doses of up to 2000 mg/kg did not induce any statistically significant changes in the incidence of MNPCEs. Therefore, our results lead to conclusion that RVS acts as a genotoxic material based on the available in vitro and in vivo results.