Lactoperoxidase System Research Articles

The Effect of Sodium Alginate Coating Incorporated with Lactoperoxidase System and Zataria multiflora boiss Essential Oil on Shelf Life Extension of Rainbow Trout Fillets During Refrigeration

The present study is aimed at evaluating the effect of functional alginate coating incorporated with Lactoperoxidase (LPOS) and Zataria multiflora Essential Oil (ZEO) or both as natural additives on microbial and chemical characteristics of rainbow trout fillets. Firstly, Different treatments of trout fillets were prepared using ZEO (0.5 and 1%) and LPOS (5%) individually and in combination. Then stored in the refrigerator for 16 days and were analyzed for chemical (pH and Total Volatiles Base-Nitrogen (TVB-N)) and microbial (Total mesophilic viable count, psychotropic count, Shewanella putrefaciens count, and Pseudomonas spp. count) characteristics at 4-day intervals. Results indicated that the combination of ZEO and LPOS had the strongest effect on chemical spoilage parameters (TVN, pH) and spoilage microbial flora of trout fillets during storage; however, samples with the individual use of ZEO or LPOS also had statistically significant(P<0.05) effects on preserving the chemical and microbial quality of trout fillets. According to the results, the application of sodium alginate coating impregnated with LPOS and ZEO especially in combination can control undesirable chemical and microbial changes of fish and extend its shelf life during refrigeration.

Catalyzed Oxidation of Carotenoids by Lactoperoxidase in the Presence of Ethanol.

The discovery of the lactoperoxidase system as a biocatalyst in milk was a landmark finding. The activation of this system using hydrogen peroxide (H2O2) raised hopes for oxidation of various organic substrates. The involvement of lactoperoxidase system in the catalyzed-oxidation of carotenoids in the whey proteins, and the effect of various solvents on carotenoids' oxidation reaction rate has been studied. However, there is no evidence for this reaction without the addition of oxidizing agents, such as peroxides. Here, we reveal that carotenoids are oxidized through the addition of just ethanol in the presence of lactoperoxidase. The oxidation of carotenoids through this exquisite strategy is ∼360 times faster than harnessing the lactoperoxidase system in whey proteins via the addition of hydrogen peroxide. Bearing in mind that ethanol is not an oxidizing agent, this observation suggests a potential paradigm shift in our understanding of lactoperoxidase and catalyzed oxidation in biochemical systems.

Effect of the Nature and Relative Concentration of Substrate, Water Mineralization, and Storage Temperature on the Oxidants Produced by Lactoperoxidase and on Their Antifungal Activity against Penicillium expansum and Botrytis cinerea

Lactoperoxidase is an enzyme that generates oxidants with antimicrobial activity in presence of a (pseudo)halogen and hydrogen peroxide, but various factors can drastically reduce the antimicrobial activity of the lactoperoxidase system. Spectroscopic, ionic chromatography, and 13C-NMR methods showed that the oxidants generated by lactoperoxidase are OSCN− in the presence of SCN− and I2 in the presence of I−. Neither of them, however, inhibited Penicillium expansum, one of the causal agents of fruit mold. When a mixture of SCN− and I− was used, no OSCN−, OCN−, I2, or interhalogen I2SCN− was produced. However, its long-term stability, NH2-oxidizing capacity, and antifungal activity against P. expansum argue in favor of an I−-derived oxidant. Strongly mineralized water optimized enzyme-catalyzed reactions with higher oxidant production. Storage at 4 °C resulted in long-term stability and extended antifungal activity against P. expansum. The relative iodide/thiocyanate concentrations turned out to be important, as better in vitro inhibition of Botrytis cinerea, the causal agent of apples’s grey mold, was obtained with a high KI + KSCN concentration, a KI/KSCN ratio of 4.5, and a (KI + KSCN)/H2O2 ratio of 1. The nature of the substrates, their relative concentrations, the medium, and the storage temperature modifed the antifungal activity of lactoperoxidase.

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.

Effects of Lactoperoxidase System Activation-Oregano Essential Oilor Chlorine on the Quality of Modified Atmosphere Packaged Fresh-Cut Iceberg Lettuce

The present work focused on the effects of the Modified Atmosphere Packaging (MAP) 1 (5% O2 and 10% CO2) or 2 (2% O2 and 5% CO2) and the previous addition of Lactoperoxidase System (LPS) and Oregano essential oil or chlorine washing on the quality of fresh-cut lettuce during refrigerated storage at +4˚C. Our results showed the significant effect of this combined treatment on quality improvement during storage. Thus, mesophilic bacteria was reduced in treated samples compared to those untreated with number which not exceeded the critical of 5 × 107 UFC∙g-1 (p 0.05). Brightness of lettuce samples was significantly reduced during storage. Thereafter, the PCA data showed the effect of combined treatment on the preservation of hygienic, physico-chemical and sensory quality up to the 7th day of refrigerated storage of these treated samples. The results obtained draw attention to modified atmosphere packaging lettuce and the addition of bio-preservatives which could be an alternative of choice to replace chlorine to preserve the sanitary quality of green products.

The antibacterial efficacy of a foam mouthwash and its ability to remove biofilms

Objectives/AimsTo evaluate the antimicrobial activity of a newly developed foam mouthwash containing a modified lactoperoxidase system in vitro.Materials and methodsBiofilms of five bacterial species were developed on hydrophobic and hydrophilic surfaces whilst salivary-based biofilm was grown on tooth enamel. Each surface was exposed to the foam mouthwash or saline in vitro. Optical density and scanning electron microscopy (SEM) was used to determine retention of the biofilm following 5 or 30 s exposure time.ResultsThe foam mouthwash was active against biofilms formed by S. aureus, K. rhizophila, M. thailandicus, E. coli, and C. violaceum and eliminated significant amount of biofilm from each surface; immature 4 h biofilm was less resistant than 24 h biofilm. A 30 s rinse showed best performance, with removal of up to 66% of biofilm from the hydrophilic surface. SEM imaging confirmed oral biofilm removal from the enamel surface after a 5 s rinse with the foam mouthwash.DiscussionFoam mouthwash demonstrated a significant impact on growing biofilm when compared against saline solution. Growing biofilms were more susceptible to the action of the foam mouthwash, which justifies after-meal use of the mouthwash when traditional dentifrices may not be accessible.ConclusionsFoam mouthwash can be a convenient on-the-go format of oral care products that can be used after meals or when needed to reduce the risk of biofilm-associated oral conditions.

ACTIVATION OF LACTOPEROXIDASE (LP) SYSTEM IN MILK AND ITS EFFECT ON THE QUALITY OF KAREISH CHEESE

In the present study, Lactoperoxidase system (LPS) was activated in fresh cow’s milk. The pH and acidity of treated milk were followed during storage at room (32°C), incubator (37°C) and refrigerator (5 ±1°C) temperatures. The activation was done using SCN ◌and H2O2 or SCN ◌and Na2CO3.1.5 H2O2. The effect of activation on microbiological quality was also investigated. All the treatments greatly improved the keeping quality of milk at room or higher temperatures compared to the untreated samples. The best results were achieved by adding 14mg SCN /L: 2mL H2O2/L to cow’s milk. In addition, slight improvement in the keeping quality of the LP-activated milk was observed when the milk was kept in a refrigerator. kareish cheese was made from cow's milk preserved by the LPS and the effect of the LPS on the chemical, microbiological and sensory properties of kareish cheese storaged for 30 days was investigated. Kareish cheese made from LPactivated cow's milk was low in the total bacterial count when compared to cheese made from the untreated one (control). The LP treatment did not affect the overall chemical composition of the cheese. Activation of LP system allowed to produce of kareish cheese with high and keeping quality.

Lactoperoxidase immobilization on silver nanoparticles enhances its antimicrobial activity.

Lactoperoxidase (LPO) is an antimicrobial protein present in milk that plays an important role in natural defence mechanisms during neonatal and adult life. The antimicrobial activity of LPO has been commercially adapted for increasing the shelf life of dairy products. Immobilization of LPO on silver nanoparticles (AgNPs) is a promising way to enhance the antimicrobial activity of LPO. In the current study, LPO was immobilized on AgNPs to form LPO/AgNP conjugate. The immobilized LPO/AgNP conjugate was characterized by various biophysical techniques. The enhanced antibacterial activity of the conjugate was tested against E. coli in culture at 2 h intervals for 10 h. The results showed successful synthesis of spherical AgNPs. LPO was immobilized on AgNPs with agglomerate sizes averaging approximately 50 nm. The immobilized conjugate exhibited stronger antibacterial activity against E. coli in comparison to free LPO. This study may help in increasing the efficiency of lactoperoxidase system and will assist in identifying novel avenues to enhance the stability and antimicrobial function of LPO system in dairy and other industries.

The combined effects of lactoperoxidase system and whey protein coating on microbial, chemical, textural, and sensory quality of shrimp (Penaeus merguiensis) during cold storage (4±1°C).

Growth and reproduction of gram‐negative bacteria has a pivotal role in spoilage of seafood products. In order to identify the effect of lactoperoxidase system (LPOS), an antimicrobial activity was added to whey protein solution at the levels of 0 (control group), 1.25%, 2.5%, 5%, and 7.5%. Then, the shrimp samples were coated with immersion method and stored in the refrigerator for 16 days. In this period, the microbial tests of psychrotrophic bacteria, mesophilic bacteria, Pseudomonas fluorescens, Pseudomonas spp., and Shewanella putrefaciens, chemical tests of total volatile basic nitrogen, thiobarbituric acid, and pH, and sensory evaluation were carried out on the days of 0, 4, 8, 12, and 16. Adding LPOS in the coating resulted in a decrease in the total specific spoilage organisms and TVB‐N. There was no significant effect for the TBA test. The levels of LPOS showed a positive correlation with the acceptable measurement in the sensory evaluation.

Extending Shelf Life of Indonesian Soft Milk Cheese (Dangke) by Lactoperoxidase System and Lysozyme.

Dangke, a type of fresh soft cheese made of bovine and buffalo milk, is a traditional dairy product used in South Sulawesi, Indonesia. It is prepared from fresh milk using the conventional method, which easily destroys the quality. This study was conducted to assess whether using lactoperoxidase system and lysozyme as preservative agents could suppress the growth of bacteria in dangke. The pH value, total microbial count, and hardness of dangke were determined to measure the quality. Lactoperoxidase and lysozyme were purified from fresh bovine milk, and their purity was confirmed using SDS-PAGE. The combination of lactoperoxidase system and lysozyme was able to remarkably suppress the total microbial count in dangke from 7.78 ± 0.67 to 5.30 ± 0.42 log CFU/ml during 8 h of storage at room temperature. Preserving dangke in this enzyme combination affected its hardness, but there was no remarkable change in the pH value. Results of this study may provide knowledge to utilize a new method to preserve the quality of dangke.

Effects of alginate coating incorporated with Bunium persicum essential oil and Lactoperoxidase system on inoculated Listeria monocytogenes in chicken breast fillets

Effects of alginate coating incorporated with Bunium persicum essential oil and Lactoperoxidase system on inoculated Listeria monocytogenes in chicken breast fillets

The antibacterial effect of whey protein-alginate coating incorporated with the lactoperoxidase system on chicken thigh meat.

Nowadays, the environmental problems due to the use of synthetic films and packages have caused the production of natural edible coatings or films. The aim of this study was to produce an edible whey protein–alginate coating with different concentrations of lactoperoxidase system to control the microbial load and increase the shelf life of chicken thigh meat stored in refrigerated condition (4 ± 1°C). So, after the provision of the alginate–whey protein coating incorporated with the lactoperoxidase system (at concentrations of 2%, 4%, and 6% in alginate–whey protein solution), microbial experiments were conducted for the period of 8 days. Three batches of organisms, including total aerobic mesophilic bacteria, Enterobacteriaceae, and Pseudomonas aeruginosa in samples, were tested by culturing in appropriate conditions. Results indicated that the coating had a substantial inhibitory effect on all lots. Also, the antimicrobial activity of coating increased with increase in lactoperoxidase system concentration in alginate–whey protein coating.

Reaction Product Variability and Biological Activity of the Lactoperoxidase System Depending on Medium Ionic Strength and pH, and on Substrate Relative Concentration.

The potential of ions produced in water by the lactoperoxidase system against plant pests has shown promising results. We tested the bioactivity of ions produced by the lactoperoxidase oxidation of I- and SCN- in several buffers or in tap water and characterized the ions produced. In vitro biological activity was tested against Penicillium expansum, the causal agent of mold in fruits, and the major cause of patulin contamination of fruit juices and compotes. In buffers, the ionic concentration was increased 3-fold, and pathogen inhibition was obtained down to the 1:15 dilution. In tap water, the ionic concentration was weaker, and pathogen inhibition was obtained only down to the 1:3 dilution. Acidic buffer increased ion concentrations as compared to less acidic (pH 5.6 or 6.2) or neutral buffers, as do increased ionic strength. 13 C-labelled SCN- and MS showed that different ions were produced in water and in buffers. In specific conditions the ion solution turned yellow and a product was formed, probably diiodothiocyanate (I2 SCN- ), giving an intense signal at 49.7 ppm in 13 C-NMR. The formation of the signal was unambiguously favored in acidic media and disadvantaged or inhibited in neutral or basic conditions. It was enhanced at a specific SCN- : I- ratio of 1:4.5, but decreased when the ratio was 1:2, and was inhibited at ratio SCN- >I- . We demonstrated that the formation of the signal required the interaction between I2 and SCN- , and MS showed the presence of I2 SCN- .

Effects of lactoperoxidase system‐alginate coating on chemical, microbial, and sensory properties of chicken breast fillets during cold storage

AbstractThe main aim of this study was to investigate the effect of alginate coating samples without lactoperoxidase system (A‐L 0) and alginate coating samples containing lactoperoxidase system (LPOS) at levels of 2% (A‐L 2), 4% (A‐L 4), and 6% (A‐L 6) on the shelf‐life of chicken breast fillets. Chemical tests, including total volatile basic nitrogen (TVB‐N), peroxide value (PV), pH, thiobarbituric acid reactive substances (TBARS), and free fatty acids (FFA), bacteriological tests of aerobic mesophilic bacteria (AMB), lactic acid bacteria (LAB), Pseudomonas aeruginosa, and Enterobacteriaceae and sensory analyses, including odor, transparency, color, and overall acceptability were performed. These coatings (especially A‐L 6), despite the effect on decreasing the formation of TVB‐N compounds (27.82 for control samples, and 21.72 mg N/100 g for A‐L 6 samples) had no significant impact (p &gt; .05) on FFA, PV, and TBARS. The LPOS‐alginate coating was effective against Enterobacteriaceae, Pseudomonas aeruginosa, and aerobic mesophilic bacteria (AMB). Also, A‐L 6 samples got acceptable sensory results. Overall acceptability of A‐L 0 and A‐L 6 samples were 3.21 ± 0.36 and 6.23 ± 0.38, respectively on the last day. These scores are significantly different (p &lt; .05). Generally, results demonstrated a positive effect of alginate‐LPOS coatings on shelf‐life extension of chicken breast fillets during cold storage.Practical applicationsConcerning the effect of alginate coating incorporated with lactoperoxidase system on controlling the bacterial growth and improving the shelf‐life of chicken breast fillets, such coating could has practical applications in increasing the food safety in meats and meat products.

Synergistic Effect of the Lactoperoxidase System and Cinnamon Essential Oil on Total Flora andSalmonellaGrowth Inhibition in Raw Milk

Despite its antibacterial and antipathogenic effects, the heat treatment of milk induces undesirable changes that can be noted in the overall properties of ultrahigh temperature (UHT) milk, such as changes in nutritional and organoleptic properties. Our goal is to find new nonthermal antibacterial technologies for the preservation of raw milk (RM). This study investigates the possible synergistic effect of using a combination of the lactoperoxidase system (LS) and 3 μg mL−1of cinnamon essential oil (cinnamon EO) to inactivate the total flora of milk andSalmonellaHadar (S. Hadar). The LS was activated with 30 mg L−1sodium percarbonate and 14 mg L−1of sodium thiocyanate. Using this approach, we obtained a synergistic effect with a complete inhibition of the activity of the total flora of the milk andS.Hadar after 12 hours at 25°C. In addition, the attainment of synergy was defined when the inhibitory effect of the two compounds together was greater than the effect observed by each compound added alone. Moreover, the monitoring of the synergistic effect at 4°C for 5 days showed complete inhibition of total flora for 3 days and forS. Hadar it was up to 5 days. To summarize, the current study clearly identified a new inhibitory combination that may be used in food-based applications.

In-Vitro Inhibition of Pythium ultimum, Fusarium graminearum, and Rhizoctonia solani by a Stabilized Lactoperoxidase System alone and in Combination with Synthetic Fungicides

Advances in enzyme stabilization and immobilization make the use of enzymes for industrial applications increasingly feasible. The lactoperoxidase (LPO) system is a naturally occurring enzyme system with known antimicrobial activity. Stabilized LPO and glucose oxidase (GOx) enzymes were combined with glucose, potassium iodide, and ammonium thiocyanate to create an anti-fungal formulation, which inhibited in-vitro growth of the plant pathogenic oomycete Pythium ultimum, and the plant pathogenic fungi Fusarium graminearum and Rhizoctonia solani. Pythium ultimum was more sensitive than F. graminearum and R. solani, and was killed at LPO and GOx concentrations of 20 nM and 26 nM, respectively. Rhizoctonia solani and F. graminearum were 70% to 80% inhibited by LPO and GOx concentrations of 242 nM and 315 nM, respectively. The enzyme system was tested for compatibility with five commercial fungicides as co-treatments. The majority of enzyme + fungicide co-treatments resulted in additive activity. Synergism ranging from 7% to 36% above the expected additive activity was observed when P. ultimum was exposed to the enzyme system combined with Daconil® (active ingredient (AI): chlorothalonil 29.6%, GardenTech, Lexington, KY, USA), tea tree oil, and mancozeb at select fungicide concentrations. Antagonism was observed when the enzyme system was combined with Tilt® (AI: propiconazole 41.8%, Syngenta, Basel, Switzerland) at one fungicide concentration, resulting in activity 24% below the expected additive activity at that concentration.

Control of Listeria Monocytogenes and Escherichia coli O157:H7 Inoculated on Fish Fillets Using Alginate Coating Containing Lactoperoxidase System and Zataria multiflora Boiss Essential Oil

ABSTRACTThe present study was conducted to investigate the inhibitory effect of alginate coating incorporated with Zataria multiflora Boiss essential oil (ZEO) and lactoperoxidase system (LPOS), individually and in combination, in order to control inoculated Listeria monocytogenes and Escherichia coli O157:H7 in rainbow trout fillets during 16days of storage at 4°C. The antibacterial activity of ZEO was evaluated against Listeria monocytogenes and E. coli O157:H7 through determination of minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). In vivo study was performed by inoculating four strains of L. monocytogenes as culture cocktail and one strain of E. coli O157:H7 on trout fillets for their survival evaluation during the 16-day storage. Results indicated that ZEO and LPOS, when used in combination in alginate solution, had a stronger effect on the control of mentioned bacteria in trout fillets; however, their individual use could significantly inhibit their growth, when compared to the control. Moreover, it has been implicated that alginate coating, when used with no antimicrobial agent, had a supportive effect on the growth of these pathogenic bacteria. Therefore, the application of alginate coating containing ZEO and LPOS is recommended in foods, especially fish and fish products.

The effect of bleaching agents on the degradation of vitamins and carotenoids in spray-dried whey protein concentrate

Previous research has shown that bleaching affects flavor and functionality of whey proteins. The role of different bleaching agents on vitamin and carotenoid degradation is unknown. The objective of this study was to determine the effects of bleaching whey with traditional annatto (norbixin) by hydrogen peroxide (HP), benzoyl peroxide (BP), or native lactoperoxidase (LP) on vitamin and carotenoid degradation in spray-dried whey protein concentrate 80% protein (WPC80). An alternative colorant was also evaluated. Cheddar whey colored with annatto (15 mL/454 L of milk) was manufactured, pasteurized, and fat separated and then assigned to bleaching treatments of 250 mg/kg HP, 50 mg/kg BP, or 20 mg/kg HP (LP system) at 50°C for 1 h. In addition to a control (whey with norbixin, whey from cheese milk with an alternative colorant (AltC) was evaluated. The control and AltC wheys were also heated to 50°C for 1 h. Wheys were concentrated to 80% protein by ultrafiltration and spray dried. The experiment was replicated in triplicate. Samples were taken after initial milk pasteurization, initial whey formation, after fat separation, after whey pasteurization, after bleaching, and after spray drying for vitamin and carotenoid analyses. Concentrations of retinol, a-tocopherol, water-soluble vitamins, norbixin, and other carotenoids were determined by HPLC, and volatile compounds were measured by gas chromatography-mass spectrometry. Sensory attributes of the rehydrated WPC80 were documented by a trained panel. After chemical or enzymatic bleaching, WPC80 displayed 7.0 to 33.3% reductions in retinol, β-carotene, ascorbic acid, thiamin, α-carotene, and α-tocopherol. The WPC80 bleached with BP contained significantly less of these compounds than the HP- or LP-bleached WPC80. Riboflavin, pantothenic acid, pyridoxine, nicotinic acid, and cobalamin concentrations in fluid whey were not affected by bleaching. Fat-soluble vitamins were reduced in all wheys by more than 90% following curd formation and fat separation. With the exception of cobalamin and ascorbic acid, water-soluble vitamins were reduced by less than 20% throughout processing. Norbixin destruction, volatile compound, and sensory results were consistent with previous studies on bleached WPC80. The WPC80 colored with AltC had a similar sensory profile, volatile compound profile, and vitamin concentration as the control WPC80.

Efficacy of whey protein coating incorporated with lactoperoxidase and α-tocopherol in shelf life extension of Pike-Perch fillets during refrigeration

Efficacy of whey protein coating solution (WPS) incorporated with lactoperoxidase system (LPOS, 2.5%) and α-tocopherol (1.5% and 3%) on the shelf life of Pike-Perch fillets during refrigeration storage (4 °C) was studied. Treated batches with α-tocopherol showed lower changes in color, odor, and TBA (Thiobarbituric Acid) compared with WPS batches (P < 0.05). WPS+2.5% LPOS treatment exhibited better quality about bacterial load, TVB-N (Total volatile basic nitrogen), texture, and overall acceptability compared to WPS (P < 0.05), while color, odor, and TBA were not significantly affected by LPOS (P > 0.05). Although interaction between LPOS and α-tocopherol in some cases led to the mutual antagonistic effect in both cases, WPS+2.5% LPOS+1.5% α-tocopherol and WPS+2.5% LPOS +3% α-tocopherol treatments had higher qualities than other treatments. Thus, it can be concluded that the combination of LPOS and α-tocopherol can donate antibacterial and antioxidant properties to WPS, and could have a high potential to be applied in the shelf life extension of Pike-Perch fillets during cold storage.

N2 Gas Flushing Limits the Rise of Antibiotic-Resistant Bacteria in Bovine Raw Milk during Cold Storage.

Antibiotic resistance has been noted to be a major and increasing human health issue. Cold storage of raw milk promotes the thriving of psychrotrophic/psychrotolerant bacteria, which are well known for their ability to produce enzymes that are frequently heat stable. However, these bacteria also carry antibiotic resistance (AR) features. In places, where no cold chain facilities are available and despite existing recommendations numerous adulterants, including antibiotics, are added to raw milk. Previously, N2 gas flushing showed real potential for hindering bacterial growth in raw milk at a storage temperature ranging from 6 to 25°C. Here, the ability of N2 gas (N) to tackle antibiotic- resistant bacteria was tested and compared to that of the activated lactoperoxidase system (HT) for three raw milk samples that were stored at 6°C for 7 days. To that end, the mesophiles and psychrotrophs that were resistant to gentamycin (G), ceftazidime (Ce), levofloxacin (L), and trimethoprim-sulfamethoxazole (TS) were enumerated. For the log10 ratio (which is defined as the bacterial counts from a certain condition divided by the counts on the corresponding control), classical Analyses of Variance (ANOVA) was performed, followed by a mean comparison with the Ryan-Einot-Gabriel-Welsch multiple range test (REGWQ). If the storage “time” factor was the major determinant of the recorded effects, cold storage alone or in combination with HT or with N promoted a sample-dependent response in consideration of the AR levels. The efficiency of N in limiting the increase in AR was highest for fresh raw milk and was judged to be equivalent to that of HT for one sample and superior to that of HT for the two other samples; moreover, compared to HT, N seemed to favor a more diverse community at 6°C that was less heavily loaded with antibiotic multi-resistance features. Our results imply that N2 gas flushing could strengthen cold storage of raw milk by tackling the bacterial spoilage potential while simultaneously hindering the increase of bacteria carrying antibiotic resistance/multi-resistance features.