Navam Hettiarachchy

Alkali-modified soy protein with improved adhesive and hydrophobic properties

Adhesive and hydrophobic properties of alkalimodified soy protein (AMSP) and trypsin-modified soy protein (TMSP) on wood were investigated. Modifying soy protein (i) under moderate alkaline conditions (pH 10.0 at 50°C) and (ii) with trypsin, enhanced adhesive strengths (730 and 743 N, respectively) compared with unmodified soy protein (340 N). Hydrophobicities of AMSP, TMSP, and unmodified soy protein isolate by sodium dodecyl sulfate binding and 1-anilino-8-naphthalene sulfonate methods were 7.6, 6.4, 5.0 and 39, 27, 13, respectively. Modified soy protein adhesives with higher hydrophobicities (AMSP and TMSP) had enhanced water-resistance properties.

Evaluation of Antibacterial Activity of Whey Protein Isolate Coating Incorporated with Nisin, Grape Seed Extract, Malic Acid, and EDTA on a Turkey Frankfurter System

The effectiveness of whey protein isolate (WPI) coatings incorporated with grape seed extract (GSE), nisin (N), malic acid (MA), and ethylenediamine tetraacetic acid (EDTA) and their combinations to inhibit the growth of Listeria monocytogenes, E. coli O157:H7, and Salmonella typhimurium were evaluated in a turkey frankfurter system through surface inoculation (approximately 10(6) CFU/g) of pathogens. The inoculated frankfurters were dipped into WPI film forming solutions both with and without the addition of antimicrobial agents (GSE, MA, or N and EDTA, or combinations). Samples were stored at 4 degrees C for 28 d. The L. monocytogenes population (5.5 log/g) decreased to 2.3 log/g after 28 d at 4 degrees C in the samples containing nisin (6000 IU/g) combined with GSE (0.5%) and MA (1.0%). The S. typhimurium population (6.0 log/g) was decreased to approximately 1 log cycles after 28 d at 4 degrees C in the samples coated with WPI containing a combination of N, MA, GSE, and EDTA. The E. coli O157:H7 population (6.15 log/g) was decreased by 4.6 log cycles after 28 d in samples containing WPI coating incorporated with N, MA, and EDTA. These findings demonstrated that the use of an edible film coating containing nisin, organic acids, and natural extracts is a promising means of controlling the growth and recontamination of L. monocytogenes, S. typhimurium, and E. coli O157:H7 in ready-to-eat poultry products.

Modification of soy proteins and their adhesive properties on woods

Adhesive properties of trypsin-modified soy proteins (TMSP) on woods were investigated. A simple method developed in our laboratory, consisting of measuring the force required to shear the bond between glued wood pieces in the Instron universal testing machine, was used to examine adhesive strength of modified soy proteins on wood. Adhesive strength of TMSP was measured for cold-pressed (ambient temperature for 2 h) and hot-pressed (60, 80, 100, and 120°C for times varying from 0.5 to 2.5 h) woods. Of the woods examined, soft maple gave the highest strength [743 Newtons (N) at a protein glue concentration of 2 mg/cm2]. For soft maple and cold-pressing, TMSP at 2 mg/cm2 gave twice the adhesive strength of unmodified protein controls, 743 vs. 340 N. Also, the adhesive strength of TMSP increased from 284 to 743 N as glue concentration was increased from 1 to 2 mg/cm2. However, hot-pressing of wood pieces beyond 1 h at 120°C and 30% relative humidity resulted in decreased adhesive strengths of TMSP compared to controls. Further, adhesive strengths of hot-pressed glued wood samples decreased when the relative humidity at which they were kept for curing increased from 30 to 60%. This negative effect of increased humidity on adhesive strengths of glued wood pieces was not observed with cold-pressed TMSP.

Human Colon and Liver Cancer Cell Proliferation Inhibition by Peptide Hydrolysates Derived from Heat-Stabilized Defatted Rice Bran

Rice bran, an economical, underutilized coproduct of rough rice milling, was used to produce peptide hydrolysates, which were investigated for anticancer activity. Protein hydrolysates prepared by Alcalase hydrolysis under optimized conditions were treated further to obtain gastrointestinal (GI)-resistant peptide hydrolysates. They were fractionated into >50, 10-50, 5-10, and <5 kDa sizes and evaluated for inhibitory activity on proliferation of human colon (Caco-2) and liver (HepG2) cancer cell lines by Trypan blue dye exclusion assay. GI-resistant <5 and 5-10 kDa sized peptide fractions inhibited growth of Caco-2 cells by 80%, and the <5 kDa fraction inhibited growth of HepG2 cells by approximately 50% compared to controls and nonresistant fractions. An MTS cell titer assay confirmed antiproliferative effects of the peptide fractions. The results demonstrated that 5-10 and <5 kDa sized GI-resistant fractions promoted significant (p < 0.05) inhibitory activities on both cancer cell lines compared to controls. More investigations are needed to show such value-added effects on the technofunctional and sensorial properties of the food protein and peptide matrices.

Alkali-modified soy proteins: Effect of salts and disulfide bond cleavage on adhesion and viscosity

Soy protein isolates were treated with NaCl, Na2SO4, or Na2SO3 (disulfide bond-cleaving agent) at a pH of 10.0 and 50°C, and the effects of these salts on viscosity, adhesive strength on woods, and water resistance of the treated isolates were investigated. Viscosity and adhesive strength decreased with increasing concentrations of these salts. At a concentration of 0.1 M, these three salts reduced the viscosity of soy proteins with no significant adverse effects on adhesive strength and water resistance. Addition of 0.1 M NaCl, Na2SO4, or Na2SO3 reduced adhesive strength insignificantly from 1230 N to 1120, 1060, or 1013 N, respectively. The viscosity of protein isolate modified at pH 10.0 and 50°C in the absence of salts was >30,000 cP. Treatment with NaCl or Na2SO4 resulted in viscosity reductions to 6000 or 1050 cP, respectively. The Na2SO3 treatment yielded an isolate with the lowest viscosity of 110 cP and which retained adhesive and water-resistive properties. The water resistance of modified soy proteins with and without 0.1 M Na2SO3 treatment was not significantly different with 3.3 and 6.6% cumulative delaminations occurring after four water soaking cycles. Treatment with 0.1 M Na2SO3 resulted in an isolate with a 28% decrease in disulfide linkages.

Effect of Organic Acids and Plant Extracts on Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium in Broth Culture Model and Chicken Meat Systems

Foodborne illness due to consumption of products contaminated with Salmonella Typhimurium (S.T.), Listeria monocytogenes (L.m.), and Escherichia coli O157:H7 (E.c.) results in many deaths and significant economic losses each year. In this study, acetic (AA), citric acid (CA), lactic acid (LA), malic acid (MA), and tartaric acid (TA) and grape seed (GS), green tea (GT), bitter melon seed (BMS), rasum, and fenugreek (FG) extracts were investigated as inhibitors against S.T., L.m., and E.c. in both broth-culture and meat systems. Brain Heart Infusion solutions containing 18.7, 37.5, and 75.0 mM organic acids and 5, 10, 20, and 40 mg/mL extracts were challenged with approximately log 6 CFU/mL S.T., L.m., and E.c. A pH-adjusted control was included to determine pH effect on exhibited antibacterial activity. For the meat system, 1 to 2 g chicken breast pieces were vacuum-infused with CA/MA/TA acid at 75 and 150 mM and GS and GT at 3000, 6000, and 9000 ppm in a partial factorial arrangement. GT and GS showed considerable activity in broth-culture. All organic acids were effective in broth-culture at 75 mM after 24 h (P < 0.05). CA and TA were effective at 37.5 mM. CA/MA/TA at 150.0 mM were the most effective in the meat system, reducing E.c., L.m. and S.T. by >5, >2, and 4-6 log CFU/g, respectively, although all organic acids showed some antibacterial activity at 75.0 and 150.0 mM. These findings demonstrate the effectiveness of organic acids and plant extracts in the control of S.T., L.m., and E.c. O157:H7.

Human cancer cell proliferation inhibition by a pentapeptide isolated and characterized from rice bran

Food-derived bioactive peptides promote functional activity against diseases and present as nutraceutical agents. The purpose of our research was to isolate and fully characterize peptide(s) derived from rice bran having anti-cancer properties. Gastrointestinal juices resistant peptide fractions were initially generated from heat stabilized de-fatted rice bran from which <5 kDa fraction was shown to inhibit proliferation of cancer cells. Based on these published findings the <5 kDa peptide fraction was selected for further characterization to obtain single pure peptide(s) with enhanced anti-cancer properties. Purification and characterization from the fraction was done employing chromatography and mass spectrometric techniques. Cancer cell viability was measured using a cell titer assay that uses a tetrazolium dye [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt; (MTS)] and the electron coupling reagent, phenazine methosulfate. Ion-exchange chromatography elutes that showed anti-cancer properties were further purified to liberate pure peptide. The pure peptide at 600-700 microg/mL dose caused 84% inhibition to colon cancer cells (Caco-2, HCT-116) growth, 80% to breast cancer cells (MCF-7, MDA-MB-231) growth and 84% to liver cancer cells (HepG-2) growth. Mass spectrometry analysis and de novo sequencing revealed the sequence of Glu-Gln-Arg-Pro-Arg for the peptide with a molecular mass of 685.378 Da. A novel pentapeptide was isolated from rice bran to possess cancer growth inhibitory properties on colon, breast, lung and liver cancer cells. This peptide could serve as a nutraceutical agent against cancer.

Extraction, quantification, and antioxidant activities of phenolics from pericarp and seeds of bitter melons (Momordica charantia) harvested at three maturity stages (immature, mature, and ripe).

Bitter melon (Momordica charantia) is an exotic vegetable used for consumption and medicinal purposes mainly throughout Asia. Phenolics were extracted from pericarp (fleshy portion) and seeds of bitter melons harvested at three maturation stages (immature, mature, and ripe) using ethanol and water solvent systems. Total phenolic assessment demonstrated 80% of ethanol to be the optimal solvent level to extract phenolics either from pericarp or seed. Main phenolic constituents in the extracts were catechin, gallic acid, gentisic acid, chlorogenic acid, and epicatechin. Free radical scavenging assay using 2,2-diphenyl-1-picrylhydrazyl (DPPH) demonstrated the bitter melon extracts as slow rate free radical scavenging agents. There were low correlations between the total phenolic contents and antiradical power values of the extracts, suggesting a possible interaction among the phenolic constituents occurred. Bitter melon phenolic extracts contain natural antioxidant substances, and could be used as antioxidant agents in suitable food products.

Electrostatic Sprays of Food-Grade Acids and Plant Extracts are More Effective than Conventional Sprays in Decontaminating Salmonella Typhimurium on Spinach

About 40000 people fall victim to Salmonella infections every year in the United States. Recent occurrences of Salmonella contaminated spinach and its recalls have accelerated the need for efficient antimicrobials targeting these pathogens. Our study was aimed at evaluating the inhibitory properties of malic, tartaric, and lactic acids, and grape seed extract (GSE) alone and in combinations and their application methods against Salmonella Typhimurium-inoculated spinach using a response surface method. Fresh spinach leaves were washed, disinfected with sodium hypochlorite solution (0.04% v/v), rewashed with sterile deionized (DI) water, and inoculated with a 2nd-day culture of S. Typhimurium (7.0 log CFU/mL). Adhered S. Typhimurium population on day 0 were 7.5 log CFU/g. These were treated with individual and combinations of organic acids with GSE or DI water (control) adjusted to the same pH as that of the test solutions with both the modes of application and leaves were refrigerated at 4 °C. Malic acid (2%) in combination with GSE (3%) or lactic acid (3%) sprayed electrostatically showed reductions of 2.6 to 3.3 log CFU/g compared to lower log reductions (0.0 to 0.3 log CFU/g) by day 14 if sprayed conventionally. These findings indicate that malic acid in combination with GSE/lactic acid solutions applied by electrostatic spraying exhibited higher inhibition of pathogens than conventional spraying and can be used for commercial applications to enhance food safety.

Effect of lipids on soy protein isolate solubility

Reduced-lipid soy protein isolate (SPI), prepared from soy flour treated so that most of the polar lipids have been removed, exhibited an increase in protein solubility of 50% over that of the control SPI prepared from hexane-defatted flour. Adding lipids from a commercial SPI during processing of reduced-lipid SPI decreased SPI solubility by 46%. The 19% decreased solubility caused by the lipids (primarily phospholipids) was largely recovered by treating the protein with a reducing agent (2-mercaptoethanol). The balance of protein insolubility, caused by the lipids, was attributed to a smaller lipid fraction (approximately 5% of the total lipids). Adding lipids during SPI processing contributed to both the formation of oxidized protein sulfhydryls, incapable of being reduced by 2-mercaptoethanol, and to oxidative deterioration of protein as determined by protein carbonyl contents.