Antimicrobial Treatments for Minimally Processed Cantaloupe Melon

ABSTRACT: Efficacy of decontamination treatments in reducing endogenous microbial populations on cantaloupe and in extending fresh-cut shelf-life were investigated. Composite rind plug samples were washed with water or solutions of sodium hypochlorite, H₂O₂, commercial detergent formulations containing dodecylbenzene sulfonic acid and phosphoric acid, or trisodium phosphate, and surviving microbial populations determined. Fresh-cut cubes were prepared aseptically from whole melons given similar treatments, and their visual appearance and bacterial population determined during storage at 4 °C. Population reductions on washed rind plugs were < 1 log with water, 1 to 2 logs with washing and sanitizing agents applied individually, and 3 logs with some sequential treatments with H₂O₂. H₂O₂ applied at 50 °C was superior to other whole-melon treatments, yielding a fresh-cut shelf-life of > 2 weeks.     

Effects of Hot Rehydration in the Presence of Hydrogen Peroxide on Microbial Quality, Texture, Color, and Antioxidant Activity of Cold-stored Intermediate-moisture Sun-dried Figs

ABSTRACT: Pectin methylesterase (PME) causes considerable softening in intermediate-moisture (IM) figs rehydrated at 30°C and cold stored at 28% to 29% moisture content. Rehydration of figs at 80°C for 16 min inactivated PME partially (25–30%), but this did not prevent the softening over 3 mo of cold storage. Also, heating did not reduce the microbial load of figs significantly and increased their browning. In contrast, rehydration of figs 1st in 2.5% H₂O₂ at 80°C for 8 min and then in water at 80°C for 8 min reduced the microbial load of IM figs significantly, turned their brown color to yellow-light brown, and maintained their desired textural properties. The residual H₂O₂ in IM figs decomposed in 3 or 1.5 wk by the in situ catalase or by application of the iron (II) sulfate-ascorbic acid residue elimination method, respectively. Hot rehydration did not affect the antioxidant activity of IM figs, but treatment of figs with H₂O₂ increased their antioxidant activity slightly. These results indicate that the hot rehydration of figs in the presence of H₂O₂ and cold storage may be applied to obtain safe and SO₂-free light-colored IM fig products.     

Desulfiting Dried Apricots by Hydrogen Peroxide

ABSTRACT: Removal of sulfites from excessively sulfited dried apricots using hydrogen peroxide (H₂O₂) was studied. Dried apricots were dipped into 0.5, 1.0, and 1.5% H₂O₂ solutions at 20 °C and 40 °C for various times. At 60 °C, apricots were also treated with 1% H₂O₂ solution. Removal of sulfites by H₂O₂ followed a 1st-order kinetic model. At 20 °C to 60 °C and 1% H₂O₂ concentration, the E_a value was 22.46 kJ mol⁻¹. H₂O₂ treatment caused lighter, more yellow, and less red dried apricots. Critical factors for H₂O₂ application are choosing the appropriate H₂O₂ concentration, temperature, and exposure time and without bleaching the natural color of dried apricots.     

Antimicrobial Activity of Lactoperoxidase System Incorporated into Cross-Linked Alginate Films

ABSTRACT:  In this study, the antimicrobial effect of lactoperoxidase (LPS) incorporated alginate films was investigated on Escherichia coli (NRRL B-3008), Listeria innocua (NRRL B-33314), and Pseudomonas fluorescens (NRRL B-253) in presence of different concentrations of H₂O₂ (0.2, 0.4, and 0.8 mM) and KSCN (1, 2, and 4 mM). The incorporation of 70 nmol ABTS/min/cm² LPS into alginate films gave 0.66 to 0.85 nmol ABTS/min/cm² enzyme activity at 0.2 to 0.8 mM H₂O₂ concentration range. The antimicrobial activity of LPS system on target bacteria changed according to the concentrations of KSCN and H₂O₂. The growth of all tested bacteria was prevented for a 6-h period by applying LPS system in presence of 0.4 or 0.8 mM H₂O₂ and 4 mM KSCN. At 0.8 mM H₂O₂ and 4 mM KSCN, the LPS system also inhibited growth of L. innocua and P. fluorescens for a 24-h incubation period, whereas E. coli growth could not be inhibited for 24 h under these conditions. At 0.2 mM H₂O₂ and 1 to 4 mM KSCN, a considerable inhibitory effect was obtained only on P. fluorescens . The decreasing order of the resistance of studied bacteria to LPS system is as follows: E. coli , L. innocua , and P. fluorescens . The developed antimicrobial system has a good potential for use in meat, poultry, and seafood since alginate coatings are already used in these products. Further studies are needed to test the LPS incorporated edible films in real food systems.     

Comparative Flavonoids Contents of Selected Herbs and Associations of Their Radical Scavenging Activity with Antiproliferative Actions in V79-4 Cells

ABSTRACT:  To elucidate the health benefit of herbal teas on the cytotoxicity induced by H₂O₂ in V79-4 cells, herbal extracts and its flavonoids were tested using lactate dehydrogenase release and determining intracellular reactive oxygen species generation and antioxidant activity with superoxide radical scavenging assay. Significant decrease in cell viability was observed on V79-4 cells treated with H₂O₂ (1 mM), while herbal extracts and its flavonoids including catechin and epigallocatechin gallate prevented the LDH release from H₂O₂ cytotoxicity. Total catechin contents of green tea (65.6 mg/g of dry matter) were significantly higher than other herbal teas (35.8 to 1.2 mg/g of DM). The relative concentration of the 4 major tea catechins ranked EGCG > EGC > EC > C. Green tea exhibited the lowest IC₅₀ values (2 g fresh herb/100 mL) of superoxide radical scavenging activity among the tested herbal tea, which indicates powerful antioxidant activity in O₂^·− radicals scavenging, followed by black tea, dandelion, hawthorn, rose hip, chamomile.     

Factors Limiting the Efficacy of Hydrogen Peroxide Washes for Decontamination of Apples Containing Escherichia coli

Factors limiting efficacy of H₂O₂ washes and alternative decontamination strategies were investigated with Golden Delicious apples, inoculated with nonpathogenic Escherichia coli. Post-treatment rinsing decreased efficacy by eliminating residual H₂O₂. A 2-stage wash incorporating a rinse to remove surfactant residues prior to H₂O₂ application was developed. Rapid attachment of E. coli to apples prevented effective removal by washing with water. Surviving E. coli following a 5% H₂O₂ wash were concentrated in stem and calyx areas. Survival was independent of the time interval between inoculation and washing. E. coli inoculation of punctured apple surfaces resulted in growth at 20 °C and greater survival after washing with 5% H₂O₂. Improved decontamination methods are needed.     

Improved Sanitizing Treatments for Fresh Tomatoes

ABSTRACT:  Fresh tomatoes repeatedly have been associated with major outbreaks of salmonellosis; however, efforts to disinfect them with chlorine or other sanitizing agents have had only mixed success. Our objective was to determine whether hydrogen peroxide (H₂O₂) treatments would be more efficacious than conventional methods in disinfecting tomatoes containing human pathogens and, at the same time, be noninjurious to quality. Tomatoes were dip inoculated with Escherichia coli NRRL B-766 or a Salmonella cocktail and then held for 0, 24, or 48 h at 4 or 24 °C prior to treatment. Treatments included 200 ppm chlorine (Cl₂) at 20 °C for 3 min, water at 20 °C for 3 min or at 60 °C for 2 min, 1% H₂O₂ at 20 °C for 15 min or at 60 °C for 2 min, and 5% H₂O₂ at 60 °C for 2, 3, or 5 min. In tomatoes held 48 h postinoculation, the chlorine treatment was only marginally more effective than an equivalent water rinse in reducing the target bacterial population, while the hot water and 1% H₂O₂ treatments achieved reductions no greater than 1.3 logs. However, application of 5% H₂O₂ at 60 °C resulted in larger reductions. Efficacy of all treatments decreased as the time interval between inoculation and treatment increased. Greater reductions could not be achieved with 5% H₂O₂ at 60 °C by increasing the contact time or addition of surfactants, and these treatments caused some quality loss.     

Chemiluminescent determination of hydrogen peroxide in water

A method for determining low concentrations of hydrogen peroxide (H₂O₂) in water, based on the chemiluminescent oxidation of 3-aminophthalhydrazide (luminol) by H₂O₂ in the presence of a copper ion catalyst, is described. Levels of H₂O₂ down to 3 × 10^-8 mol/1 (1 ppb) can be determined. The method may be used to monitor the amount of residual H₂O₂ in aseptically filled packages sterilized with H₂O₂ before filling.     

Production of Hydrogen Peroxide by Lactobacillus delbrueckii subsp. lactis as Influenced by Media Used for Propagation of Cells

ABSTRACT: Cells of Lactobacillus delbrueckii subsp. lactis I were grown in several media to determine the most suitable medium for production of H₂O₂ during refrigerated storage. H₂O₂ was detected from cells that were resuspended in phosphate buffer containing variable amounts of glucose. Cells grown in MRS broth produced more H₂O₂ during refrigerated storage than those grown in LBS pr PTM. Cells grown in LBS produced more H₂O₂ then those grown in PTM. For both MRS and LBS, cells inoculated in phosphate buffer containing 0% glucose produced significantly more H₂O₂ than those containing 1% or 10% glucose. MRS medium appears to be the best medium for growing cells for the production of H₂O₂.     

Degradation Kinetics of Anthocyanins from Sour Cherry, Pomegranate, and Strawberry Juices by Hydrogen Peroxide

ABSTRACT: Degradations were studied at different hydrogen peroxide (H₂O₂) concentrations (9.31 to 27.92 mmol. L¹) over a range of 10° to 30 °C. Degradation of anthocyanins by H₂O₂ was described by first-order function. Comparison of t_1/2 values revealed that sour cherry anthocyanins were the most resistant to H₂O₂, followed by pomegranate and strawberry anthocyanins. Thus, the removal of residual H₂O₂ from the juice contact surfaces of aseptically packaged strawberry juices should be controlled more carefully to prevent anthocyanin degradation. Respective E_a values were between 9.4 to 11.1, 9.5 to 11.4, and 11.4 to 12.2 kcal.mol¹; and Q₁₀ values between 1.59 to 2.22, 1.62 to 2.05, and 1.76 to 2.36 for strawberry, sour cherry, and pomegranate anthocyanins.     

INACTIVATION AND REGENERATION OF IMMOBILIZED CATALASE

Catalase was immobilized on collagen membrane. The inactivation of immobilized catalase by 0.01M and 0.1M H₂O₂ was reported. After the initial stage of inactivation, a stable catalatic activity as measured in a continuous flow of 0.01M H₂O₂ through a modular reactor was observed for longer than 20 days (2.6 min residence time). The regeneration of catalatic activity from the O.1M H₂O₂ inactivated catalase occurred after incubating the inactivated modular reactor with 0.01M phosphate buffer, pH 6.8. The amount of activity regenerated is directly proportional to the time of incubation.     

Efficacy of Sulfuric Acid Scarification and Disinfectant Treatments in Eliminating Escherichia coli O157: H7 from Alfalfa Seeds Prior to Sprouting

ABSTRACT: E. coli O157:H7 reduction on inoculated alfalfa seeds was investigated using acid scarification treatments with or without subsequent application of sanitizers. Scarification with 0.1 to 2N H₂SO₄ for 2.5 to 45 min did not affect (p ≤ 0.05) seed viability. E. coli O157:H7 was reduced by 2.1 to 5.0 logs after treating with 0.1 to 2N H₂SO₄ for 5 to 20 min. Combined scarification (0.5N H₂SO₄) and H₂O₂ or CH₃COOH treatments enhanced microbial destruction by less than 1 log compared to sanitizer alone. Chlorine, Na₂CO₃, or Na₃PO₄ treatments preceded by scarification did not significantly increase microbial destruction compared to sanitizer alone. Appreciable reductions in seed germination were only observed with chlorine treatments.     

Shelf-Life Extension of Fresh Mushrooms (Agaricus bisporus) By Application of Hydrogen Peroxide and Browning Inhibitors

ABSTRACT: An experimental washing process for fresh mushrooms entailing immersion in 5% H₂O₂, followed by application of a sodium erythorbate-based browning inhibitor, was optimized, scaled up, and made continuous. The laboratory process described previously was modified by adding a pre-wash step using 0.5% to 1% H₂O₂, increasing the wash solution H₂O₂ concentration from 3% to 5%, and substituting 4% sodium erythorbate + 0.1% NaCl for the more complex browning inhibitor formulation used previously. A continuous, commercial-scale washing facility was built to test the new process. Mushrooms washed by this process were free of adhering soil, less subject to brown blotch than conventionally washed mushrooms, and at least as resistant to enzymatic browning as unwashed mushrooms during storage at 4 °C. Storage at 10 °C accelerated development of brown blotch and browning.     

Reaction characteristics of a tooth-bleaching agent containing H2O2 and NaF: in vitro study of crystal structure change in treated hydroxyapatite and chemical states of incorporated fluorine

This in vitro study was performed to elucidate the reaction mechanism of sodium fluoride (NaF), which is added to tooth-bleaching agents to lessen the adverse effect of hydrogen peroxide (H₂O₂) on teeth. Both hydroxyapatite (HAP) and dihydrated dicalcium phosphate (DCPD), model substances for dental hard tissues, dissolved easily in a simple H₂O₂ solution. In the H₂O₂/NaF solutions, however, fluorine compounds that could not be identified by X-ray diffraction (XRD) due to the smallness of the products were formed on the surface of the HAP. X-ray photoelectron spectroscopy (XPS) studies demonstrated that fluoridated hydroxyapatite (FHAP) was formed on HAP, and that calcium fluoride (CaF₂) formation was accelerated by increasing the concentrations of fluorine and H₂O₂ along with the partial dissolution of HAP. In H₂O₂/NaF solution, DCPD also transformed easily to FHAP and CaF₂, which are favorable to the remineralization process on the tooth surface. Thus, the mechanism of NaF was elucidated, and its use together with H₂O₂ for tooth bleaching was proved to be effective. Methodologically, the XPS two-dimensional plot made it possible for the first time to directly estimate the ratio of FHAP and CaF₂ in the reaction products, in contrast to the conventional wet-analytical method, which is simply based on the difference in solubility of the two components.     

Reaction characteristics of a tooth-bleaching agent containing H2O2 and NaF: in vitro study of crystal structure change in treated hydroxyapatite and chemical states of incorporated fluorine

This in vitro study was performed to elucidate the reaction mechanism of sodium fluoride (NaF), which is added to tooth-bleaching agents to lessen the adverse effect of hydrogen peroxide (H₂O₂) on teeth. Both hydroxyapatite (HAP) and dihydrated dicalcium phosphate (DCPD), model substances for dental hard tissues, dissolved easily in a simple H₂O₂ solution. In the H₂O₂/NaF solutions, however, fluorine compounds that could not be identified by X-ray diffraction (XRD) due to the smallness of the products were formed on the surface of the HAP. X-ray photoelectron spectroscopy (XPS) studies demonstrated that fluoridated hydroxyapatite (FHAP) was formed on HAP, and that calcium fluoride (CaF₂) formation was accelerated by increasing the concentrations of fluorine and H₂O₂ along with the partial dissolution of HAP. In H₂O₂/NaF solution, DCPD also transformed easily to FHAP and CaF₂, which are favorable to the remineralization process on the tooth surface. Thus, the mechanism of NaF was elucidated, and its use together with H₂O₂ for tooth bleaching was proved to be effective. Methodologically, the XPS two-dimensional plot made it possible for the first time to directly estimate the ratio of FHAP and CaF₂ in the reaction products, in contrast to the conventional wet-analytical method, which is simply based on the difference in solubility of the two components.     

Food Deprivation Promotes Oxidative Imbalance in Rat Brain

ABSTRACT:  The present study was aimed to evaluate the effect of food deprivation in brain oxidative status of Wistar and Goto-Kakizaki (GK) rats. For this purpose, we evaluated several oxidative stress parameters: lipid peroxidation (thiobarbituric acid reactive substances [TBARS]) and protein oxidation markers, hydrogen peroxide (H₂O₂) levels, nonenzymatic (reduced [GSH] and oxidized glutathione [GSSG] and vitamin E) and enzymatic (glutathione peroxidase [GPx], glutathione reductase [GRed], and manganese superoxide dismutase [MnSOD]) antioxidant defenses. Four-mo-old Wistar and GK rats were divided into 2 groups. One group of each rat strain was maintained under normal diet and the other groups were maintained under 50% food deprivation during 2 mo. GK rats under normal diet presented lower levels of vitamin E and higher GRed activity and GSH/GSSG ratio when compared with Wistar control rats. In Wistar rats, food deprivation induced a significant decrease in vitamin E levels and a significant increase in GPx activity, H₂O₂ production, and TBARS formation in the presence of the prooxidant pair ADP/Fe²⁺. However, GK rats under food deprivation presented a significant decrease in vitamin E levels and GRed activity and a significant increase in H₂O₂ production when compared with GK under normal diet. In summary, our results indicate that food deprivation affects brain oxidative status, which could predispose brain cells to degeneration and death.     

Effect of some thermal and chemical pre-treatments on smoked oyster mushroom quality

The effect of different thermal and chemical pre-treatments on quality and enzyme activities of smoked mushroom was investigated. Mushrooms were blanched (water and steam) and dipped in different concentrations of SO₂, H₂O₂, ethylenediaminetetraacetic acid (EDTA) and citric acid for 10 min before smoking. Enzyme activities, colour characteristics, microbiological and sensory examinations were carried out every 2 weeks up to 8 weeks of storage at 4 °C. Smoked mushroom pre-treated with sulphites (SO₂), H₂O₂ and steam blanching had the best colour values, better scores for all sensory characteristics and lower non-enzymatic browning compared with the other pre-treatments. Pre-treatment against total aerobic bacteria, yeast and moulds was the most effective when using citric acid, EDTA and steam, followed by smoking of mushroom. The most effective pre-treatments on quality and safety of smoked mushrooms were those using H₂O₂ and steam. It can be concluded that thermal and chemical treatments followed by smoking of mushroom reduce enzyme activities and are suitable for preserving mushrooms.     

Use of hydrogen peroxide detection strips to determine the extent of pasteurization in whole milk

Commercially available hydrogen peroxide (H₂O₂) detection strips were shown to be effective in determining known levels of H₂O₂ in milks where the lactoperoxidase system (LPS) had been inactivated. In addition, the strips were evaluated for determination of residual H₂O₂ in LPS-activated milks, following a range of heat treatments. The detection of residual H₂O₂ corresponded with results of zero lactoperoxidase activity. Hence, the detection strips offer a simple and accurate method for detecting the absence of lactoperoxidase, and therefore can be used to determine whether the milk has been subjected to overpasteurization. The technique provides a more convenient method than the standard procedure based on oxidation of 1,4-phenylenediamine.     

Effect of Antioxidants on the Oxidative Stability of Chicken Breast Meat in a Dispersion System

ABSTRACT: The antioxidant efficiency of ascorbic acid, α-tocopherol, Trolox C, and catechin were evaluated for chicken breast meat in a dispersion system at 37 °C. Peroxidation was induced by adding different kinds of initiators. The initiators exhibited the following order of catalytic action: ascorbic acid/Fe²⁺ > hemoglobin > Cu⁺/H₂O₂ > 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH). The antioxidant efficiency of the antioxidants tested depended on their phase distribution and their reactivity to the radicals in various initiation systems. Among the antioxidants tested, catechin was the most effective antioxidant for chicken breast meat oxidation under the experimental conditions.     

Inhibition of Oxidant-Induced Biochemical Changes of Pork Myofibrillar Protein by Hydrolyzed Potato Protein

ABSTRACT:  The objective of the study was to investigate the role of hydrolyzed potato protein (HPP) in protecting myofibril protein isolate (MPI) from oxidative modification. MPI prepared from pork muscle was suspended (30 mg protein/mL) in 15 mM piperazine- N , N -bis(2-ethane sulfonic acid) buffer (pH 6.0) with 0, 0.3, 0.75, and 1.5 mg/mL of antioxidative HPP (1-h Alcalase hydrolysate). Oxidation was induced by incubating the protein suspensions at 4 °C for 24 h with (1) an iron-catalyzed oxidizing system (IOS: 0.01 mM FeCl₃, 0.1 mM ascorbic acid, and 1.0 mM H₂O₂) and (2) a metmyoglobin-oxidizing system (MOS: 0.1 mM metmyoglobin and 0.1 mM H₂O₂). Changes in oxidized MPI were measured as thiobarbituric acid-reactive substances (TBARS), protein carbonyl content, Ca- and K-ATPase activities, and ultraviolet (UV) spectra. Oxidation increased the production of TBARS and protein carbonyls by 2.9- and 0.24-fold in IOS and 5.6- and 2.2-fold in MOS, respectively. The 2 oxidizing systems altered the Ca- and K-ATPase activities and exposed hydrophobic groups buried in MPI. The presence of HPP reduced the extent of MPI oxidation in all physicochemical categories tested. Therefore, HPP may be used as a potential functional ingredient in meat products to enhance their oxidative stability.