Inactivation of microbiota and selected spoilage and pathogenic bacteria in milk by combinations of ultrasound,hydrogen peroxide,and active lactoperoxidase system

Ultrasound has the potential for numerous applications in the dairy industry, as it is possible to inactivate microorganisms while causing minimal changes to the natural properties of milk. This study evaluated the inactivation of microbiota and selected spoilage and pathogenic bacteria in milk using combinations of ultrasound and hydrogen peroxide (H₂O₂) or the active lactoperoxidase system (LP-s). The effect of ultrasound alone or in combination with H₂O₂ or sodium thiocyanate (NaSCN):H₂O₂ ratio (LP-s) was influenced by amplitude, sonication time, type of microorganism and concentration of H₂O₂ or NaSCN:H₂O₂ ratio (LP-s). Sonication in the presence of H₂O₂ or the active LP-s was more effective as higher microbial reduction was obtained at lower amplitude and shorter treatment time compared with sonication alone. These results suggest that ultrasound combined with H₂O₂ or the active LP-s has a potential to ensure the microbial quality and safety of milk.     

Activation of Lactoperoxidase System in Milk by Glucose Oxidase Immobilized in Electrospun Polylactide Microfibers

ABSTRACT: In this study, glucose oxidase (GOX) was immobilized in polylactide (PLA) fibers that were used to activate the lactoperoxidase (LP) system in milk. The GOX‐containing microfibers were electrospun from emulsions prepared by dispersing aqueous GOX in PLA dissolved in a chloroform and N,N‐dimethylformamide blend, using sorbitan monopalmitate as an emulsifier. The enzymatic activity of GOX‐in‐PLA fibers (1100 ± 400 nm diameter) was more than 19 times higher than that of the GOX‐in‐PLA membrane formed by direct casting, due to the larger surface area of the electrospun fibers. The activation of LP in model solutions using GOX‐in‐PLA fibers provided a more sustained generation of antimicrobial OSCN^? than direct activation using H₂O₂. Preliminary evaluation on milk samples showed that the electrospun GOX‐in‐PLA microfibers are capable of activating the naturally present LP system, indicating that they may be promising for active food packaging applications to extend the shelf life of milk.     

Lactose oxidase: A novel activator of the lactoperoxidase system in milk for improved shelf life

The lactoperoxidase system (LS), an antimicrobial system naturally present in milk that is activated by H₂O₂, has been used to inhibit microbial outgrowth in raw milk in areas where refrigeration is not viable. This study evaluated lactose oxidase (LO) as a novel activator of the LS. Lactose oxidase oxidizes lactose and produces H₂O₂ needed for the activation of the LS. The antimicrobial effect of different concentrations of LO with and without components of the LS, thiocyanate (TCN) and lactoperoxidase (LP), was evaluated in model systems and then applied in pasteurized milk and raw milk. In general, an increase in LO caused greater reductions of Pseudomonas fragi in the model systems and treatments were more effective at 6°C than at 21°C. At 6°C, the LO solution at 0.12 and 1.2 g/L showed significantly higher microbial reduction than the control when both added alone and combined with LS components. At 21°C, treatments with 1.2 g/L of LO solution achieved a reduction of >2.93 log cfu/mL in 24 h, but at lower levels there was not a significant reduction from the control. Higher concentrations of TCN led to a greater P. fragi reduction at both temperatures when LO was added alone but not when combined with LP. In pasteurized milk, the LO solution at 0.12 g/L caused a reduction of approximately 1.4 log of P. fragi within 24 h when added alone and a reduction of approximately 2.7 log when combined with LP and TCN. Bacterial counts remained at significantly lower levels than the control during storage, and the TCN-supplemented milk exhibited an approximately 6-log difference from the control by d 7. In raw milk, the total bacterial growth curve showed a longer lag phase when the LS was activated by LO (11.3 ± 1.4 h) compared with the control (4.0 ± 1.0 h), but it was not different from the recommended method (9.4 ± 1.0 h). However, the total bacterial count after 24 h for the sample treated with LO and TCN (5.3 log cfu/mL) was significantly lower compared with the control (7.2 log cfu/mL) and the recommended method (6.1 log cfu/mL). Results from this study suggest that LO is an alternative source of H₂O₂ that enhances the microbial inhibition achieved by the LS. Lactose oxidase could be used to develop enzyme-based preservation technologies for applications where cold chain access is limited. This enzymatic approach to improving the shelf life of dairy products also represents a novel option for clean label spoilage control.     

The use of lactoperoxidase for the bleaching of fluid whey

Lactoperoxidase (LP) is the second most abundant enzyme in bovine milk and has been used in conjunction with hydrogen peroxide (H₂O₂) and thiocyanate (SCN^–) to work as an antimicrobial in raw milk where pasteurization is not feasible. Thiocyanate is naturally present and the lactoperoxidase system purportedly can be used to bleach dairy products, such as whey, with the addition of very little H₂O₂ to the system. This study had 3 objectives: 1) to quantify the amount of H₂O₂ necessary for bleaching of fluid whey using the LP system, 2) to monitor LP activity from raw milk through manufacture of liquid whey, and 3) to compare the flavor of whey protein concentrate 80% (WPC80) bleached by the LP system to that bleached by traditional H₂O₂ bleaching. Cheddar cheese whey with annatto (15 mL of annatto/454 kg of milk, annatto with 3% wt/vol norbixin content) was manufactured using a standard Cheddar cheesemaking procedure. Various levels of H₂O₂ (5–100 mg/kg) were added to fluid whey to determine the optimum concentration of H₂O₂ for LP activity, which was measured using an established colorimetric method. In subsequent experiments, fat-separated whey was bleached for 1 h with 250 mg of H₂O₂/kg (traditional) or 20 mg of H₂O₂/kg (LP system). The WPC80 was manufactured from whey bleached with 250 mg of H₂O₂/kg or 20 mg of H₂O₂/kg. All samples were subjected to color analysis (Hunter color values and norbixin extraction) and proximate analysis (fat, protein, and moisture). Sensory and instrumental volatile analyses were conducted on WPC80. Optimal LP bleaching in fluid whey occurred with the addition of 20 mg of H₂O₂/kg. Bleaching of fluid whey at either 35 or 50°C for 1 h with LP resulted in >99% norbixin destruction compared with 32 or 47% destruction from bleaching with 250 mg of H₂O₂/kg, at 35 or 50°C for 1 h, respectively. Higher aroma intensity and increased lipid oxidation compounds were documented in WPC80 from bleached whey compared with WPC80 from unbleached whey. Monitoring of LP activity throughout cheese and whey manufacture showed that LP activity sharply decreased after 30 min of bleaching (17.01 ± 1.4 to <1 U/mL), suggesting that sufficient bleaching takes place in a very short amount of time. Lactoperoxidase averaged 13.01 ± 0.7 U/mL in unpasteurized, fat-separated liquid whey and 138.6 ± 11.9 U/mL in concentrated retentate (11% solids). Lactoperoxidase may be a viable alternative for chemical whey bleaching.     

Effect of thiocyanate and hydrogen peroxide on the keeping quality of ovine,bovine and caprine raw milk

The preservation of raw ovine, bovine and caprine milks by the activation of their natural lactoperoxidase (LP) systems was investigated. The LP system of the samples was activated by adding different amounts of sodium thiocyanate and sodium percarbonate to give three different concentrations of thiocyanate and hydrogen peroxide: 7, 14 and 28 mg/L and 15, 30 and 60 mg/L, respectively. Each type of raw milk, ovine, bovine and caprine, was analysed after being treated as follows: Control (C), LP inactivated (T0), LP activated with different concentrations of thiocyanate (7, 14 and 28 mg/L) and hydrogen peroxide (15, 30 and 60 mg/L) and stored at 4°C for 72 h. The results indicated that concentrations of 28 mg/L (SCN^?) and 60 mg/L (H₂O₂) would be adequate for preserving milks of different mammals at 4°C, but we should take into consideration the international norm – 14 mg/L of SCN^? and 30 mg/L of H₂O₂, respectively. Overall, the results have shown that, by activation of the LP system in raw milk, it was possible to store ovine, bovine and caprine milks at 4°C for several days. Changes in titratable acidity, total colony counts, psychrotrophic bacteria, coliforms, moulds and yeasts of the milk samples were followed during storage at low temperature with increasing dose. The effect of doses was greater in bovine milk than in caprine milk and finally in ovine milk.     

Changes in physical and sensory characteristics of marinated broiler drumsticks, treated with nisin and lactoperoxidase system

The lactoperoxidase system (LPS) and nisin have been shown to inactivate some micro‐organisms in foods. However, further studies were needed to evaluate whether these treatments had any influence on the physical and sensory characteristics of broiler drumsticks. In this study, a solution that contained 1% acetic acid and 3% salt with pH adjusted to 4 was developed as a standard marinade. The LPS consisted of 1‐μg mL^?1 lactoperoxidase, 5.9‐mm potassium thiocyanate (KSCN), and 2.5‐mm H₂O₂ was added to the marinade, followed by nisin at 100 IU mL^?1. The results showed that the physical characteristics, including raw and cooked drumstick pH, percentage incorporation of marinade solution, cooking loss, skin and muscle L*, a*, b* values, and sensory characteristics, including skin and muscle sensory colour, aroma and flavour, off aroma, off flavour, juiciness and tenderness of the broiler drumsticks, treated with 100‐IU mL^?1 nisin and LPS were not impaired.     

Enhanced Chemiluminescence Determination of Hydrogen Peroxide in Milk Sample Using Metal–Organic Framework Fe–MIL–88NH<Subscript>2</Subscript> as Peroxidase Mimetic

The presence of hydrogen peroxide (H₂O₂) in milk is a major concern because it constitutes a public health hazard. Here, a sensitive flow injection chemiluminescence method was established for the detection of H₂O₂. As a peroxidase mimetic, metal–organic framework Fe–MIL–88NH₂ was found to significantly enhance the chemiluminescence of luminol–H₂O₂ reaction. The enhancement mechanism could be attributed to peroxidase-like activity of Fe–MIL–88NH₂, which effectively catalyzed the decomposition of H₂O₂ into hydroxyl radical. The experimental conditions for the chemiluminescence reaction were thoroughly investigated. The chemiluminescence intensity was proportional to the concentration of H₂O₂ in the range of 0.1–10.0 μmol/L. The detection limit was 0.025 μmol/L H₂O₂, and the relative standard deviation was 2.6 % for 11 replicated measurements of 1.0 μmol/L H₂O₂ solution. The practicability of this method was demonstrated by determining H₂O₂ in milk samples.     

Colour improvement of common carp (Cyprinus carpio) fillets by hydrogen peroxide for surimi production

The preferred colour for surimi is white, but surimi prepared from light fillets of common carp (Cyprinus carpio) is slightly pink. Hydrogen peroxide (H₂O₂; 1–3% v/v) with and without sodium tri‐polyphosphate (STP; 1–2% w/v) was added to a sodium carbonate bath (pH 7.0–11.5) resulting in a final pH range of 4.4–10.1 which was injected into carp fillets. After soaking and tumbling for 30 min at 4–10 °C, the fillets were evaluated for colour and water holding capacity (WHC). Fillets tumbled with treatment solution with different pH levels (7.0–11.5), but with no H₂O₂ or STP added, had improved colour with significantly (P < 0.05) higher L* compared with untreated fillets as the control. However, the colour improvement [(L* and colour deviation (ΔE)] was not significantly different (P > 0.05) within the pH levels (7.0–11.5) trialled. With increasing H₂O₂ levels (1–3%), fillets became lighter and ΔE increased significantly (P < 0.05), especially with a 3% H₂O₂ treatment at pH of 10.5 (adjusted pH before H₂O₂ addition, actual pH after H₂O₂ addition was 8.2). The whiteness (L*?3b*) of kamaboko produced from treated (3% H₂O₂, pH 10.5) common carp light fillets was not significantly different to that of kamaboko from Alaska pollock and threadfin bream. Treatments combining H₂O₂ (3%) with STP (1–2%) significantly reduced the L* value obtained in comparison with fillets treated with only H₂O₂ (3%). Similarly, fillets treated with STP (1%) alone, resulting in lower L* values, irrespective of treatment pH (7.0–11.5). WHC, an indicator of the quality of the fillet texture, increased from 816 g/kg at pH 7.0 without STP to 841 g/kg at pH 11.5 with 1% STP. Treatment with H₂O₂ (without STP) decreased the WHC of the fillets.     

The use of hydrogen peroxide for the digestion and determination of total nitrogen in chickpea (Cicer arietinum L.) and pigeonpea (Cajanus cajan L.)

The use of hydrogen peroxide as an alternative to catalysts in the determination of nitrogen in plant materials has been investigated. Nitrogen determination in leaf, stem and seed samples of chickpea and pigeonpea was carried out by three digestion procedures, using hydrogen peroxide (H₂O₂ digestion) without a catalyst, and with mercury or selenium as catalysts (catalyst digestions). The nitrogen values obtained by the three digestion procedures did not differ significantly from each other when examined by microKjeldahl (MKJ) using mercury as a catalyst, and by a Technicon auto analyser (TAA) using selenium as catalyst. The gradual addition of H₂O₂, as recommended previously, was found to be unnecessary. In view of the cost and health hazards implicated with the use of mercury and selenium for digestion, the procedure based on H₂O₂ digestion is preferable for large scale N determinations in plant tissue and seed samples of these pulse crops. The results sugest that the H₂O₂ digestion technique can be conveniently adapted for total N analysis in plant tissues and grain samples by either TAA or MKJ method.     

Interaction between nitric oxide and hydrogen peroxide in postharvest tomato resistance response to Rhizopus nigricans

BACKGROUND: Nitric oxide (NO) and hydrogen peroxide (H₂O₂) are signal molecules involved in the disease response of plants, and there is a close relationship between them. To investigate the interaction of NO and H₂O₂ during disease resistance response in postharvest fruits and vegetables, tomato (Lycopersicon esculentum cv. Lichun) fruits were treated after harvest by vacuum infiltration with NO donor and H₂O₂ scavenger. RESULTS: The resistance of tomato fruits to Rhizopus nigricans Ehrenb. invasion and the activities of defensive enzymes phenylalanine ammonia‐lyase, chitinase and glutathione S‐transferase were enhanced by NO. However, these effects of NO on resistance were weakened by H₂O₂ scavenger, which showed that H₂O₂ was required in NO‐mediated disease resistance in harvested tomato. Meanwhile, the endogenous H₂O₂ level was dual‐regulated by NO. During the earlier period of storage the H₂O₂ peak was advanced by NO, but during the later period of storage, when the concentration of H₂O₂ was relatively higher, H₂O₂ accumulation was delayed by NO. The activities of superoxide dismutase, ascorbate peroxidase and catalase were involved in this regulation. CONCLUSION: The results imply that application of exogenous NO can enhance the disease resistance of postharvest tomato; NO may interact with H₂O₂ and exert its effect by modulating the endogenous H₂O₂ level. This result is useful for the further investigation and application of NO in postharvest disease control. Copyright © 2008 Society of Chemical Industry     

Immobilization of Glucoamylase on Silanized Aluminium Oxide

The possibility of immobilization of glucoamylase (GA) on silanized Al₂O₃ was examined using adsorption and covalent bonding via glutaric aldehyde. Both methods yield active unsoluble enzymes, which however gradually lose their catalitic activity in cyclic operation. Various agents aiming to improve the stability of immobilized GA were tested. It has beer found that the enzyme bound covalently to the carrier retains its activity to the higher degree while kept in the substrate solution.     

Accumulation of Iron in Lactic Acid Bacteria and Bifidobacteria

Lactobacillus acidophilus, L. delbrueckii var. bulgaricus, L. plantarum and Streptococcus thermophilum, all used extensively in the food industry, were tested for their ability to internalize and/or oxidize ferrous iron (Fe²+). For comparison some experiments were performed with bifidobacteria, B. thermophilum and B. breve. All organisms except L. bulgaricus could transport Fe²⁺ into the cell, where it was partially oxidized to the ferric form (Fe(III)). In addition, L. acidophilus and L. bulgaricus could oxidize Fe²⁺ to Fe(III) extracellularly through the elaboration of H₂O₂ into the medium when the experiments were carried out in air. L. bulgaricus elaborated H₂O₂ only in the presence of glucose, whereas L. acidophilus released H₂O₂ in absence of glucose. We concluded that lactic acid bacteria, like bifidobacteria, can exert some beneficial effects in animal organisms, or in food processing and storage, by making Fe²⁺ unavailable to harmful microorganisms.     

Absorption spectra of gelatin copper complexes and copper (II) sulfate and their impact on cotton peroxide bleaching

A gelatin copper complex was synthesized with gelatin and copper (II) sulphate. The previous study had indicated that the gelatin copper complex could improve peroxide bleaching effectiveness of cotton in low-temperature. By measuring the spectra absorption abilities of gelatin, copper (II) sulphate and gelatin copper complex respectively, it proved that gelatin copper complex was formed. The catalytic bleaching effectiveness of H₂O₂/gelatin copper complex system and H₂O₂/copper (II) sulphate system were compared. The results show that the gelatin copper complex and copper (II) sulphate can catalyze hydrogen peroxide decomposition and improve the whiteness of bleached cotton. Whiteness and capillary effects of the cotton fabric bleached in H₂O₂/gelatin copper complex system and in H₂O₂/copper (II) sulphate system at 70℃ are close to the conventional high-temperature bleaching. Besides, the strength retention of the fabric bleached in H₂O₂/gelatin copper complex system at 70℃ is the biggest among the three samples. The strength retention of the fabric bleached in H₂O₂/copper (II) sulphate system at 70℃ is the smallest among the three samples. So gelatin copper complex is a more effective catalyst than copper (II) sulphate in low temperature peroxide bleaching of cotton fabric.     

Covalent Immobilization of a α-Amylase onto Poly(methyl methacrylate-2-hydroxyethyl methacrylate) Microspheres and the Effect of Ca2+ Ions on the Enzyme Activity

α-Amylase was covalently immobilized onto poly(methyl methacrylate-2-hydroxyethyl methacrylate) microspheres, which were activated by using either epichlorohydrin (ECH) or cyanuric chloride (C₃N₃Cl₃). The properties of the immobilized enzyme were investigated and compared with those of the free enzyme. For the assays carried out at 25 °C and pH 6.9, the relative activities were found to be 73.0% and 90.8% for epichlorohydrin and cyanuric chloride bound enzymes, respectively. Upon immobilization, the maximum activities were obtained at lower pH values and higher temperatures as compared with the free enzyme. Kinetic parameters were calculated as 2.51 g/L, 28.54 g/L and 15.50 g/L for K_m and 1.67 × 10⁻³ gL⁻¹ min⁻¹ 2.89 × 10⁻⁴ gL⁻¹ min⁻¹ and 1.89 × 10⁻³ gL⁻¹ min⁻¹ for V_max for free, epichlorohydrin and cyanuric chloride bound enzymes, respectively. Enzyme activities were found to be ca. 32.7% for ECH and 41.1% for C₃N₃Cl₃ activated matrices after storage for one month. On the other hand the free enzyme lost its activity completely within 20 days. Immobilization, storage stability and repeated use capability experiments carried out in the presence of Ca²⁺ ions demonstrated higher stability in the presence of these ions. The enzymes immobilized in the presence of Ca²⁺ ions retained 90.6% and 90.8% of the original activities even after 30 days in the case of ECH and C₃N₃Cl₃ activations, respectively. In repeated batch experiments, i.e., 20 uses of the enzyme in 3 days; in the absence of Ca²⁺ ions retentions of 79.2% and 77.1% of the original enzyme activities were observed for ECH and C₃N₃Cl₃ immobilized enzymes, respectively, whereas, in the case of addition of Ca²⁺ ions to the assay medium, these values were enhanced to 95.3% and 92.2%.     

Immobilized alcalase alkaline protease on the magnetic chitosan nanoparticles used for soy protein isolate hydrolysis

An efficient immobilization of Alcalase 2.4L alkaline protease has been developed by using chitosan-coated magnetic nanoparticles as support via glutaraldehyde cross-linking reaction. The Fe₃O₄ nanoparticles, Fe₃O₄-chitosan, and immobilized Alcalase 2.4L alkaline protease were characterized by X-ray diffraction, transmission electron microscope, Fourier transform infrared spectroscopy, electron spin resonance, and vibrating sample magnetometry. Results showed that the binding of chitosan and Alcalase 2.4L alkaline protease on Fe₃O₄ through cross-linking was successful. In addition, the Alcalase 2.4L alkaline protease immobilized with chitosan-coated magnetic nanoparticles enhanced the activity, the optimum reaction temperature and pH value for the immobilized enzyme were 55 °C and 10, respectively, compared with the free enzyme, and the optimal temperature and pH profile range were considerably broadened. Similarly, the thermal stability was enhanced by immobilization, and the kinetic parameters of free and immobilized Alcalase 2.4L alkaline protease were determined. Then, from our hydrolysis experiments, we found that immobilized Alcalase 2.4L alkaline protease uses Fe₃O₄-chitosan had a greatest hydrolytic activity, and the DH of soy protein isolate (SPI) can reach to 18.38 %, against 17.50 % with the free enzyme after 140 min. Furthermore, the immobilized Alcalase 2.4L alkaline protease could maintain about 86 % of its original activity after ten consecutive operations. Thus, Fe₃O₄-chitosan immobilized Alcalase 2.4L alkaline protease a good candidate for the continuous hydrolysis of SPI.     

Cytoprotective activity of lotus (Nelumbo nucifera Gaertner) leaf extracts on the mouse embryonic fibroblast cell

This study was conducted to evaluate the cytoprotective activity of lotus (Nelumbo nucifera Gaertner) leaf extract (LLE) on mouse embryonic fibroblast (MEF) cells. The 2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radical scavenging activities of LLE increased in a concentration dependent manner. The cells, damaged by oxidative stress, decreased their viability following increasing concentration of H₂O₂, but the co-treatment of n-butanol fraction of LLE and H₂O₂ resulted in an increase in cell growth, by about 25%, compared to the cells treated with H₂O₂. The n-butanol fraction of LLE inhibited the cytotoxicity induced by H₂O₂ in a concentration dependent manner. The oxidative damage to the cells, measured by apoptotic and necrotic cell accumulation, was similar with the addition of the n-butanol fraction of LLE to H₂O₂. Taken together, these results suggest that LLE inhibited the cytotoxicity which is induced by H₂O₂, and has a protective effect on MEF cell against oxidative stress.     

Efficacy of Hydrogen Peroxide as a Bactericide in Poultry Chiller Water

Hydrogen peroxide (H₂O₂) as a bactericide in poultry chiller water reduced aerobic organisms by 95–99.5% with 6,600 ppm or higher H₂O₂, and E. coli by 97–99.9% with 5,300 ppm or higher. Even higher concentrations were required for similar bacterial reductions on carcasses; aerobic organisms on carcasses were reduced by 94% with 11,000 ppm and E. coli were reduced by 80% with 12,000 ppm. However, the reaction of H₂O₂ with catalase from the blood resulted in a bleached and bloated carcass which would be commercially undesirable for fresh or frozen retail sales, but may not be objectionable when used for deboned meat.     

Challenge testing the lactoperoxidase system against a range of bacteria using different activation agents

Lactoperoxidase (LP) exerts antimicrobial effects in combination with H₂O₂ and either thiocyanate (SCN⁻) or a halide (e.g., I⁻). Garlic extract in the presence of ethanol has also been used to activate the LP system. This study aimed to determine the effects of 3 LP activation systems (LP+SCN⁻+H₂O₂; LP+I⁻+H₂O₂; LP + garlic extract + ethanol) on the growth and activity of 3 test organisms (Staphylococcus aureus, Pseudomonas aeru-ginosa, and Bacillus cereus). Sterilized milk was used as the reaction medium, and the growth pattern of the organisms and a range of keeping quality (KQ) indicators (pH, titratable acidity, ethanol stability, clot on boiling) were monitored during storage at the respective optimum growth temperature for each organism. The LP+I⁻+ H₂O₂ system reduced bacterial counts below the detection limit shortly after treatment for all 3 organisms, and no bacteria could be detected for the duration of the experiment (35 to 55 h). The KQ data confirmed that the milk remained unspoiled at the end of the experiments. The LP + garlic extract + ethanol system, on the other hand, had no effect on the growth or KQ with P. aeruginosa, but showed a small retardation of growth of the other 2 organisms, accompanied by small increases (5 to 10 h) in KQ. The effects of the LP+SCN⁻+H₂O₂ system were intermediate between those of the other 2 systems and differed between organisms. With P. aeruginosa, the system exerted total inhibition within 10 h of incubation, but the bacteria regained viability after a further 5 h, following a logarithmic growth curve. This was reflected in the KQ indicators, which implied an extension of 15 h. With the other 2 bacterial species, LP+SCN⁻+H₂O₂ exerted an obvious inhibitory effect, giving a lag phase in the growth curve of 5 to 10 h and KQ extension of 10 to 15 h. When used in combination, I⁻ and SCN⁻ displayed negative synergy.     

Impact of Some Avermectins on Lactoperoxidase in Bovine Milk

Many macrocyclic lactones, including avermectins, are known to be used as a veterinary drug, agricultural pesticides, and insecticides. Lactoperoxidase (EC 1.11.1.7) is one of the peroxidases found in milk. Lactoperoxidase has a natural host defense system against micro-organisms and a natural antimicrobial system. In this study, some macrocyclic lactones, including emamectin-benzoate, doramectin, eprinomectin, abamectin, moxidectin-vetranal, and ivermectin were investigated for in vitro inhibitory effects on the bovine lactoperoxidase enzyme, which was purified using amberlite CG-50 H⁺ resin and sepharose 4B-L-tyrosine-sulphanamide affinity chromatography 344.6-fold, with a yield of 61.1% and a specific activity of 39.11 EU/mg protein. Emamectin-benzoate, doramectin, eprinomectin, abamectin, moxidectin-vetranal, and ivermectin are also known strong antiparasitary properties. In this study, we demonstrated that avermectins have strong lactoperoxidase inhibitory effects. Of these, the emamectin-benzoate was shown to have the most inhibiting effect against lactoperoxidase with Ki value of 6.82 ± 2.60 µM.     

Efficacy of 1% Hydrogen Peroxide Wash in Decontaminating Apples and Cantaloupe Melons

Efficacy of 1% hydrogen peroxide (H₂O₂) in decontaminating apples and cantaloupes containing human pathogens was investigated. Apples inoculated with Escherichia coli (ATCC 25922) were washed with 1% H₂O₂ at 20 or 40 °C for 15 or 30 min. Population reductions approaching 3 logs were obtained with all treatments. Comparable reductions were obtained with apples inoculated with 3 strains of E. coli O157:H7, associated with cider outbreaks, and a 5‐strain cocktail. The 1% H₂O₂ treatment was ineffective against E. coli 766 (ATCC 9637; similar to Salmonella Poona) on inoculated cantaloupes. Treatment of apples with 1% H₂O₂ was carried out successfully in a wet dump tank.