Potential antioxidant and lipid peroxidation inhibition of Phyllanthus acidus leaf extract in minced pork.

OBJECTIVE: This study investigated the effect of extraction solvents on antioxidant bio-active compounds as well as potential antioxidant and lipid peroxidation inhibition of Phyllanthus acidus (P. acidus) leaf extract in minced pork. METHODS: The effect of various solvent systems of water, 25%, 50%, 75% (v/v) ethanol in water and absolute ethanol on the extraction crude yield, total phenolic content, total flavonoid content and in vitro antioxidant activities of P. acidus leaves was determined. In addition, antioxidant activities of the addition of crude extract from P. aciuds leaves at 2.5 and 5 g/kg in minced pork on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical cation decolorization, reducing power and inhibition of lipid peroxidation (thiobarbituric acid reactive substances; TBARS) were determined. Moreover, sensory evaluation of the samples was undertaken by using a 7-point hedonic scale. RESULTS: The results showed that the highest crude yield (2.8 g/100 g dry weight) was obtained from water which also had the highest recovery yield for total phenolic content, total flavonoid content and the strongest antioxidant activity. The addition of crude water extract from P. acidus leaves was more effective in retarding lipid peroxidation and higher antioxidant activity than control and butylated hydroxytoluene in minced pork. In particular, the samples containing P. acidus extract had no significant effect on the sensory scores of overall appearance, color, odor, texture, flavor, and overall acceptability compared to the control. CONCLUSION: Water solvent was an optimally appropriate solvent for P. acidus leaf extraction because of its ability to yield the highest amount of bio-active compounds and in vitro antioxidant property. Particularly, P. acidus crude water extract also strongly expressed the capacity to retard lipid oxidation, radical scavenging, radical cation decolorization and reducing power in minced pork. The results of this study indicated that P. acidus leaf extract could be used as natural antioxidant in the pork industry.

Purification and characterization of a novel plantaricin, KL-1Y, from Lactobacillus plantarum KL-1.

Three bacteriocins from Lactobacillus plantarum KL-1 were successfully purified using ammonium sulfate precipitation, cation-exchange chromatography and reverse-phase HPLC. The bacteriocin peptides KL-1X, -1Y and -1Z had molecular masses of 3053.82, 3498.16 and 3533.16 Da, respectively. All three peptides were stable at pH 2-12 and 25 °C and at high temperatures of 80 and 100 °C for 30 min and 121 °C for 15 min. However, they differed in their susceptibility to proteolytic enzymes and their inhibition spectra. KL-1Y showed broad inhibitory activities against Gram-positive and Gram-negative bacteria, including Salmonella enterica serovar Enteritidis DMST 17368, Pseudomonas aeruginosa ATCC 15442, P. aeruginosa ATCC 9027, Escherichia coli O157:H7 and E. coli ATCC 8739. KL-1X and -1Z inhibited only Gram-positive bacteria. KL-1X, KL-1Y and KL-1Z exhibited synergistic activity. The successful amino acid sequencing of KL-1Y had a hydrophobicity of approximately 30 % and no cysteine residues suggested its novelty, and it was designated "plantaricin KL-1Y". Plantaricin KL-1Y exhibited bactericidal activity against Bacillus cereus JCM 2152(T). Compared to nisin, KL-1Y displayed broad inhibitory activities of 200, 800, 1600, 800, 400 and 400 AU/mL against the growth of Bacillus coagulans JCM 2257(T), B. cereus JCM 2152(T), Listeria innocua ATCC 33090(T), Staphylococcus aureus TISTR 118, E. coli O157:H7 and E. coli ATCC 8739, respectively, whereas nisin had similar activities against only B. coagulans JCM 2257(T) and B. cereus JCM 2152(T). Therefore, the novel plantaricin KL-1Y is a promising antimicrobial substance for food safety uses in the future.

Peppermint essential oil enhances the vase life of Dendrobium orchids.

To extend the vase life of cut flowers, there is now a trend of using plant essential oils in place of synthetic chemicals, as they are fully biodegradable, more eco-friendly, and safer. The objective of this study was to examine the possible application and postharvest quality effects of three plant essential oils namely, ginger (Zingiber officinale Roscoe), peppermint (Mentha piperita L.), and citronella (Cymbopogon nardus Rendle), as natural vase solution for cut Dendrobium flowers. Peppermint essential oil showed promise as a holding solution for extending the vase life of Dendrobium orchids. To confirm vase life extension, emulsions containing peppermint essential oil at concentrations of 50 and 100 µg mL-1 combined with 4 % glucose to formulate holding solutions applied to Dendrobium orchids. Vase life, some biochemical changes, electrolyte leakage, total microbial count in the holding solution, and physical condition via scanning electron microscopy (SEM) were evaluated over a period of 25 days. The three major compounds in peppermint essential oil were identified as menthol (33.24 %), 1-menthone (18.91 %) and menthofuran (14.85 %). The essential oil was applied in emulsion form as a holding solution. Treatment with 4 % glucose and either 50 or 100 µg mL-1 peppermint essential oil prolonged the vase life of Dendrobium orchids to up to 28 days. Scanning electron microscopy on Day 7 showed that the xylem vessels of treated orchids remained clear, suggesting reduced microbial plugging at the stalk end. Similarly, on Day 20, a reduced microbial cell count was observed for treated orchids (<1 log CFU mL-1) in comparison with controls (7.20 ± 0.04 log CFU mL-1). Finally, the essential oil improved flower quality by helping preserve petal membrane stability and petal anthocyanin content. Our results suggest the application of peppermint essential oil as a novel alternative to chemicals used in holding solutions for extending the vase life of Dendrobium orchids.

Effects of Humectant and Roasting on Physicochemical and Sensory Properties of Jerky Made from Spent Hen Meat.

This study was carried out to develop jerky product utilizing spent hen meat. Manipulation of water activity (aw) of semi-dried meat with the addition of humectants (glycerol and sorbitol at the concentration of 0, 10, and 15%) and roasting process were applied to enhance quality of jerky product. After spent hen meat was ground, formulated, reformed and then dried in convection oven at 85℃ for 2 h followed by 60℃ for 1 h, all jerky samples showed values of aw ≤0.85 with total aerobic bacteria, yeast and mold and Staphylococcus aureus counts were reduced to undetectable levels. Moreover, the results showed that the 15% glycerol added jerky showed superior quality, indicated by the lowest aw, low protein aggregation as evaluated by sorption isotherm and the lowest shear value as compared to sorbitol added and control samples (p<0.05). Regardless effect of humectant, roasting could improve the quality of the jerky via enhanced sensory attributes by increasing color, appearance, flavor and overall acceptability scores (p<0.05). Therefore, spent hen meat could be used as a potential raw material for jerky in which soft product texture obtained by the addition of glycerol and intense flavor resulted from roasting process after drying, leading to sensory acceptance.

Characterization of antimicrobial substance from Lactobacillus salivarius KL-D4 and its application as biopreservative for creamy filling.

Lactobacillus salivarius KL-D4 isolated from duck intestine produced bacteriocin which was stable at high temperature and a wide pH range of 3-10. Its cell free supernatant at pH 5.5 exhibited wide inhibitory spectrum against both G+ and G- bacteria. The highest bacteriocin production was obtained in MRS broth supplemented with 0.5 % (w/v) CaCO3 at 6 h by gentle shaking. PCR walking using specific primers at the conserved region of class-II bacteriocin resulted in 4 known genes of kld1, kld2, kld3 and kld4 with 100 % similarity to genes encoding for salivaricin α, ß, induction peptide and histidine protein kinase of Lb. salivarius GJ-24 which did not previously report for bacteriocin characterization, while showing 94, 93, 59 and 62 % to other salivaricin gene cluster, respectively. The high activities of 25,600 AU/ml indicated a strong induction peptide expressed by kld3 which has low similarity to previous inducer reported. Based on operon analysis, only kld1, kld3 and kld4 could be expressed and subsequently elucidated that only salivaricin α like bacteriocin was produced and secreted out of the cells. Using protein purification, only a single peptide band obtained showed that this strain produced one bacteriocin which could be salivaricin α namely salivaricin KLD showing about 4.3 kDa on SDS-PAGE. Partial purification by 20 % ammonium sulfate precipitation of the product was tested on the artificial contamination of creamy filling by Bacillus cereus, Enterococcus faecalis, Pseudomonas stutzeri, Staphylococcus sp. and Stenotrophomonas sp. resulting the growth inhibitory efficiency of 4.45-66.9, 11.5-100, 100, 0-28.1 and 5-100 % respectively. Therefore, salivaricin KLD can be a tentative biopreservative for food industry in the future.

In vitro Characterization of Bacteriocin Produced by Lactic Acid Bacteria Isolated from Nem Chua, a Traditional Vietnamese Fermented Pork.

The aim of this study was to screen and In vitro characterize the properties of bacteriocin produced by lactic acid bacteria isolated from Vietnamese fermented pork (Nem chua). One hundred and fifty LAB were isolated from ten samples of Nem chua and screened for bacteriocin-producing lactic acid bacteria. Antimicrobial activity of bacteriocin was carried out by spot on lawn method against both gram positive and gram negative bacteria. One isolate, assigned as KL-1, produced bacteriocin and showed inhibitory activity against Lactobacillus sakei, Leuconostoc mesenteroides and Enterococcus faecalis. To characterize the bacteriocin-producing strain, optimum temperature, incubation period for maximum bacteriocin production and identification of bacteriocin-producing strain were determined. It was found that the optimum cultivation temperature of the strain to produce the maximum bacteriocin activity (12,800 AU/mL) was obtained at 30℃. Meanwhile, bacteriocin production at 6,400 AU/mL was found when culturing the strain at 37℃ and 42℃. The isolate KL-1 was identified as L. plantarum. Antimicrobial activity of cell-free supernatant was completely inhibited by proteolytic enzyme of trypsin, alpha-chymotrypsin and proteinase K. Bacteriocin activity was stable at high temperature up to 100℃ for 10 min and at 4℃ storage for 2 d. However, the longer heating at 100℃ and 4℃ storage, its activity was reduced.