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.     

Effect of hydrogen peroxide on quality of fresh-cut tomato

ABSTRACT:  The effect of hydrogen peroxide (H₂O₂; 0, 0.1, 0.2, and 0.4 M) on selected nutritional quality of fresh-cut tomato was investigated. Microbial population of tomato slices stored at 10 °C and treated with H₂O₂ was lower than the control by 1-(0.2 and 0.4 M) and 5-log (0.4 M), 3 and 7 d after processing, respectively. Dipping fresh-cut tomato into H₂O₂ resulted in reduced phenolic and antioxidant levels after 7 d in storage by at least 5% and 20%, respectively, and produced an initial decline in vitamin C and lycopene. Change in color values in the H₂O₂ treatments were associated with reduced carotenoid content. Our results confirmed antimicrobial benefits of H₂O₂ but revealed a compromise in antioxidant and carotenoid contents of fresh-cut tomatoes.     

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.     

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.     

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.     

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 Antimicrobial Wash Treatments for Decontamination of Apples

ABSTRACT: We investigated means of improving efficacy of hydrogen peroxide washes in reducing Escherichia coli populations on inoculated apples by increasing contact between attached bacteria and the wash solution. Golden Delicious apples were inoculated with E. coli and treated with heated 5% H₂O₂ with or without agitation, by spraying and simultaneous brushing or abrading calyx and stem areas, or by vacuum infiltration. Samples were homogenized, diluted, and plated to enumerate surviving bacteria. Population reductions were greater when apples were treated with agitation, by targeted spraying with abrasion, by vacuum infiltration with stem removal, and by application of treatments at 80 °C. However, discoloration occurred at temperatures above 60 °C.     

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.     

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.     

Efficacy of two acidic sanitizers for microbial reduction on metal cans and low-density polyethylene film surfaces

ABSTRACT:  This study investigated 2 sanitizer formulations and compared them with hydrogen peroxide (H₂O₂). Formulation number 1 contained citric acid and sodium dodecylbenzene sulfonate (SDBS). Formulation number 2 contained SDBS, citric, lactic, phosphoric acids, and benzoic acid. Low concentration levels of the sanitizers (1.0% for formulation 1 and 0.5% for formulation 2) were compared with 35% H₂O₂ for their efficacies on Escherichia coli , Listeria innocua, and Saccharomyces cerevisiae inoculated onto low-density polyethylene (LDPE) films and metal cans at room temperature (23 ± 1 °C) and 40 °C. The results showed that both formulations 1 and 2 required >120 s to sanitize both materials from microbial populations at room temperature, while <15 s was needed for the H₂O₂. Except for formulation 1 on the E. coli inoculated LDPE film surface, the sanitizers completely eliminated the bacterial populations on both materials in 60 s at 40 °C. In general, the formulations were more effective for reduction of the microbial numbers on the can material when compared with the LDPE film. The E. coli showed greater tolerance for the sanitizers when exposed to the process conditions in this study. All sanitizers completely eliminated the test organisms in ≤36 s at 40 °C when tested on a commercial Benco Aseptic packaging machine.     

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.     

Effectiveness of Individual or Combined Sanitizer Treatments for Inactivating Salmonella spp. on Smooth Surface, Stem Scar, and Wounds of Tomatoes

ABSTRACT: Unwaxed, green tomatoes ('Florida 47' cultivar) were contaminated with Salmonella and then treated with aqueous solutions of sodium hypochlorite (HOCl; 200 ppm), acidified sodium chlorite (ASC; 1200 ppm), peroxyacetic acid (PAA; 87 ppm), or chlorine dioxide gas (ClO₂; total 100 mg). Additionally, a combined treatment of immersion in HOCl, followed by immersion in ASC and then exposure to ClO₂ gas was investigated. Tomatoes were spot inoculated with a 5-strain Salmonella cocktail on smooth surfaces, stem scar tissue, or puncture wounds. A 3 replicate set of each of the sample groups was stored at 20 °C and 95% relative humidity (RH) and retested after 5 d. Greater than 4.0-log unit reductions of Salmonella spp. inoculated on the smooth surface of the tomatoes were seen for all aqueous sanitizer treatments, with Salmonella populations below the detection limit after 5 d of storage. All aqueous treatment groups showed > 1.0-log unit reductions in Salmonella at the stem scar and >2.0-log unit reduction at puncture wounds. The ClO₂ gas treatment reduced Salmonella to undetectable levels at the stem scar, but had no apparent effect on populations inoculated in puncture wounds. The combined treatment resulted in a 3.0-log unit reduction of inoculated Salmonella at puncture wounds. In all cases except for treatment with chlorine, surviving Salmonella populations did not increase after the 5 d of storage. Results of this study suggest the combined treatment was most effective for minimizing the risk of Salmonella contaminated on tomatoes.     

Improved Firmness in Calcified Diced Tomatoes by Temperature Activation of Pectin Methylesterase

ABSTRACT: The effects of temperature and calcium on pectin methylesterase (PME) activity and texture in tomato pericarp material were examined. Heating thin slices of pericarp to temperatures between 50°C and 75°C led to the rapid evolution of methanol from the material, indicating an activation of PME. This activity was further stimulated when CaCl₂ (up to 2.0% w/v) was added. When applied to half-inch diced tomato pericarp, the same conditions that led to the activation of PME also improved firmness. Diced tomatoes treated for 5 min with 0.5% CaCl₂ at 70°C were 2.5 times firmer than diced tomatoes treated with CaCl₂ at room temperature. This improvement in texture by treating with CaCl₂ at elevated temperatures was only apparent when the tomatoes received a subsequent 100°C treatment. Heating tomatoes to 70°C either before or after the CaCl₂ treatment also improved firmness through a subsequent high-temperature treatment, but to a lesser extent than heating during the CaCl₂ treatment. These results are consistent with the model that heating to 70°C greatly increases PME activity, leading to extensive pectin de-esterification and increased calcium cross-linking of the pectins in the middle lamella. Production of thermally processed diced tomatoes with improved firmness should be possible by increasing the temperature during and after calcium treatment.     

Decontamination Efficacy of Combined Chlorine Dioxide with Ultrasonication on Apples and Lettuce

ABSTRACT:  The bacterial reduction of Salmonella and Escherichia coli O157:H7-inoculated apples and lettuce by ClO₂ at 0, 5, 10, 20, and 40 ppm with and without 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, have been studied. The treatments of ClO₂ at 20 and 40 ppm for 3, 6, and 10 min or at 5 and 10 ppm for 6 and 10 min with 170-kHz ultrasonication caused 3.115 to 4.253 log reductions in Salmonella and 2.235 to 3.865 log reduction in E. coli O157:H7 on inoculated apples. Using combined ClO₂ and ultrasonication to treat 4.48 × 10⁴ CFU/g Salmonella and 1.07 × 10⁵ CFU/g E. coli O157:H7-inoculated lettuce, the bacterial reductions were 2.257 to 2.972 and 1.357 to 2.264 log, respectively. The residual ClO₂ decreased with increasing treatment times, over 80% of ClO₂ was detected after the 3-min treatment, and more than 70% remained after the 10-min treatment time. No bacteria were recovered from the posttreatment solutions of ClO₂ or ClO₂ combined with ultrasonication. The temperature of the ClO₂ treatment was 20.1 °C, and it increased to 40.1, 44.9, and 50.3 °C, with 170-kHz ultrasonic treatments for 3, 6, and 10 min, respectively, on apples.     

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.     

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.     

EFFECTS OF LOW CONCENTRATIONS OF H2O2 ON LIPID OXIDATION AND OF STORAGE AND pH ON NONHEME IRON CONTENT OF RAW BEEF MUSCLE

Ground beef samples were prepared from semimembranosus muscles, and beef muscle residue devoid of heme pigments was prepared by repeated washing of the ground muscle with distilled-deionized water. When ground muscle, or muscle residue samples treated with metmyoglobin-H₂O₂ (4 mg metmyoglobin/g muscle residue; 1:0.1 to 1:1 for molar ratio of metmyoglobin to H₂O²) were stored at 4°C for 0 or 6 days, no changes in nonheme iron content were observed. Similarly, nonheme iron content of stored samples was not affected by pH (5.5, 6.0 or 6.5). While metmyoglobin-H₂O² added to water-extracted beef muscle residue catalyzed the oxidation of the indigenous lipids, treatment of the residue with H₂O² alone had no effect on the oxidation.     

Texture of rehydrated dried bell peppers modified by low-temperature blanching and calcium addition

Diced green bell pepper was blanched twice, once at 51–79 °C for 19–61 min, and once at 95 °C for 3 min, and dried. The firmness of rehydrated samples was measured by puncture, and optimum conditions assessed by response surface methodology. The optimized model showed that, blanching at 65 °C for 49 min gave a 64% increase in puncture force over the control. The optimum temperature was used to evaluate the effect of adding CaCl₂. The dices were blanched twice, once at 65 °C for 3 min in either 0 or 4% CaCl₂, secondly in either 0 or 2% CaCl₂ solution at 95 °C for 3 min. In the second case the dices had been held at room temperature for 0–30 min before treatment. Adding CaCl₂ increased puncture force significantly ( P  ≤ 0.05). The best results, those which gave greatest firmness, were obtained by blanching at 65 °C for 3 min in 4% CaCl₂, holding for 16 min after blanching, followed by a secondary blanching at 95 °C in 2% CaCl₂.     

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.     

Use of microemulsions as vehicles for nucleophilic reagents in cosmetic formulations

The modifications of chemical reactivity induced in the human hair during its treatment with oxidative (H₂O₂) or reductive (HSO₃Na) agents via a micellar or a microemulsion system have been investigated. For this purpose, phase diagrams of micellar solutions and microcmulsions with H₂O₂ or NaSO₃H have been made in order to find out the corresponding areas of solubility. The properties of conductivity, surface tension and light scattering of various monophasic compositions as a function of their water content, have been studied.
As a result of the chemical reactivity data of human hair obtained through the reaction of H₂O₂ or HSO₃Na via a micellar or a microemulsion system, it appears reasonable to predict a more effective reaction of such agents with cystine residues existing in keratinic substrates, particularly when they are applied via a microemulsion. The decrease of the water content of the compositions considered, increases chemical reactivity of the keratinic proteins favouring the formation of cysteine and of cysteic acid in the reductive or oxidative treatments respectively.