Antibacterial interactions of pulegone and 1,8-cineole with monolaurin ornisin against Staphylococcus aureus

The aim of this study was to investigate the antibacterial interactions of pulegone and 1,8-cineole with monolaurin ornisin against Staphylococcus aureus. The individual and combined antibacterial activities of the compounds were evaluated using minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), fractional inhibitory concentration index (FICi), and time-kill methods. Furthermore, the mechanism of the antibacterial action of the compounds was tested by measuring the release of cell constituents. The MIC values of pulegone, 1,8-cineole, nisin, and monolaurin were 5.85 µl/ml, 23.43 µl/ml, 6.25 µg/ml, and 0.031 mg/ml, respectively. A synergistic antibacterial activity (FICi = 0.5) was found between 1,8-cineole and nisin. The time-kill assay showed that the populations of S. aureus exposed to 1,8-cineole, nisin, and their combination were decreased by 5.9, 5.3, and 7.1 log CFU (colony-forming units)/mL, respectively. The combination of 1,8-cineole and nisin also induced the highest release of cell constituents. It was concluded that the combination of 1,8-cineole and nisin could be considered as a novel and promising combination which may reduce the required dose of each antibacterial compound.

Antibacterial Effects of Ultrasound, Cinnamon Essential Oil, and Their Combination Against Listeria monocytogenes and Salmonella Typhimurium in Milk

The antibacterial effects of ultrasound (US) and cinnamon essential oil (CEO), individually and combined, were investigated against Listeria monocytogenes and Salmonella Typhimurium in low- and high-fat milk during 6-day storage. At the end of storage, CEO alone decreased 2 and 2.2 log cycles of Salmonella Typhimurium and 2.5 and 3 log cycles of L. monocytogenes populations in low- and high-fat milk, respectively. US alone reduced 1.6 log cycle of Salmonella Typhimurium and 0.7 log cycle of L. monocytogenes in both milk type. The combined treatment could reduce 2.7 log cycle of Salmonella Typhimurium in low-fat milk and 3.8 log cycle in high-fat milk. The combined treatment also achieved 4.3 and 4.5 log cycle reductions of L. monocytogenes in low- and high-fat milk, respectively. The results of this study showed that the combination of CEO and US could be used as an effective antibacterial treatment in milk. PRACTICAL APPLICATIONS: Due to adverse effects of thermal processing on the sensory and nutritional properties of food and the potentially harmful effects of chemical preservatives, nonthermal preservation methods and natural antimicrobials have been gained much attention. In this study, the antibacterial effects of ultrasound (US) and cinnamon essential oil (CEO), individually and combined, were investigated against Listeria monocytogenes and Salmonella Typhimurium in low- and high-fat milk. The results indicated that combination of US and CEO could significantly decrease L. monocytogenes and Salmonella Typhimurium populations in milk. Then, this combined treatment may be used as an effective alternative method to microbial inactivation in milk.

Gouda cheese spoilage prevention: Biodegradable coating induced by Bunium persicum essential oil and lactoperoxidase system

This study aimed to prepare an inhibitory edible coating for Gouda cheese based on whey protein containing lactoperoxidase system (LPOS) and Bunium persicum essential oil (EO) in order to control postpasteurization contamination. Using a full factorial design, the effects of LPOS and EO on microbiological characteristics and chemical indices of manufactured Gouda cheeses were evaluated during 90 days of storage time. Listeria, lactic acid bacteria, Enterobacter, Escherichia, and Pseudomonas species were considered as potential pathogenic and spoilage indicators of produced Gouda cheese samples. Chemical properties of cheeses were assessed using the free fatty acid, peroxide value, and thiobarbituric acid experiments. The results showed that bacteria counts remained constant in cheese samples coated with EO and also EO-LPOS. However, the survival of gram-positive lactic acid bacteria and Enterobacter spp. was more pronounced in LPOS-based coating. The most effective treatments on oxidation stability parameters in cheese samples were EO- and EO-LPOS coatings. By the addition of B. persicum EO and LPOS, further inhibition of the lipid oxidation of the cheese samples was achieved. Lipolysis, as a result of lipid degradation, was more pronounced in the control, whey-coated, and whey-LPOS-coated samples in comparison with whey-EO- and whey-EO-LPOS-coated samples during the final days of storage time. These results indicate that antibacterial, lipid oxidation, and oxygen barrier properties of the coatings were developed by the addition of B. persicum EO and LPOS.

Antibiotic resistance and biofilm formation ability of Salmonella serotypes isolated from beef, mutton, and meat contact surfaces at retail

In this study, Salmonella isolates recovered from meat (beef and mutton) and meat contact surfaces at retail were investigated to determine their serotype, antibiotic resistance, and biofilm formation ability. Salmonella was found in 29 (24.17%) samples out of 120 samples including 14/50 (28%) of beef, 10/40 (25%) of mutton, and 5/30 (16.67%) of meat contact surfaces. Seven isolates were identified as S. Enteritidis, three as S. Typhimurium, and two as S. Typhi, while the rest of the isolates were considered as other Salmonella spp. All of the isolates were resistant to at least one antimicrobial agent and 48.27% of them were identified as multidrug-resistant (MDR) Salmonella. All (100%) of meat contact surfaces isolates, 42.8% of beef isolates, and 30% of mutton isolates were found to be MDR Salmonella. Resistance to nalidixic acid (100%), tetracycline (79.3%), and sulphamethoxazole/trimethoprim (44.8%) were observed. The gyrA gene was detected in 19 of 29 isolates, but tetA was found in one isolate. All of the serotypes were able to form biofilm (75.86 % moderate and 24.14 % strong) and S. Enteritidis was the strongest biofilm producer. The findings indicated that the majority of Salmonella isolates in this study were MDR and biofilm producer. Then, safety measures such as cleaning and disinfection must be taken to control Salmonella and promote public health. PRACTICAL APPLICATION: The present study provides useful information on the prevalence of Salmonella serotypes in meat and meat contact surfaces and their antibiotic resistance patterns as well as biofilm formation capacities. Improving hygiene practices in livestock, slaughterhouses, and at retails may reduce the risk of meat contamination to Salmonella. Meanwhile, high levels of antibiotic resistance in Salmonella isolates emphasized on the improper use of antibiotics.

Application of composite coating of Nostoc commune Vauch polysaccharides and sodium carboxymethyl cellulose for preservation of salmon fillets

The spoilage of fish products and the growth of pathogenic bacteria cause great economic loss and serious harm to human health, so fish preservation is very important issue. In this study, Nostoc commune Vauch polysaccharides (NVP) was added into sodium carboxymethyl cellulose (CMC) to form a mixed coating to prepare an active packaging material. The antibacterial and antioxidant activities of NVP, physicochemical properties of the mixed coating, and preservative effects of the coating on salmon fillets were evaluated. The results showed that NVP had good antibacterial and antioxidant activities. Physical characterization of the coating solution showed that when the ratio of NVP to CMC was 1:3, the coating had the best dispersion, denser structure and strongest hydrogen bond. On this basis, NVP/CMC coating can significantly prolong the shelf life of salmon fillets during cold storage by reducing pH, improving the color and texture, delaying the oxidation of fat and protein, inhibiting the growth of microorganisms. At the same time, the coated salmon fillets had good sensory acceptance. The results showed that the edible coating has a broad application prospect in the preservation of fish products.

Effect of extraction conditions on antioxidant activity of barberry (Berberis vulgaris L.) fruit extracts

Barberry fruit is consumed in different forms including dried fruit, juice, jam and marmalade in Iran. This fruit is also used as a food additive (flavoring and colorant) in soup and rice dishes. In present study, antioxidant activities of acetone, ethanol and water (infusion and decoction) extracts of barberry (Berberis vulgaris) fruit were investigated using 2,2-azinobis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and reducing power methods. Total phenolic contents of the extracts were also estimated using Folin-Ciocalteu assay. In ABTS assay, acetone and ethanol extracts showed the highest radical scavenging activity, while in DPPH and reducing power methods, acetone extract and decoction exhibited the strongest antioxidant activity. Meanwhile, the antioxidant potential of water extracts increased with increasing heating time (antioxidant activity of decoction was higher than that of infusion). The highest total phenolic content was found in the acetone extract (92.75 mg GAE per g). It was concluded that the acetone extract and decoction of barberry fruit can be used as an effective natural antioxidant in food industry.

Effects of Thymus vulgaris and Mentha pulegium on colour, nutrients and peroxidation of meat in heat-stressed broilers

This study was designed to investigate the effects of Thymus vulgaris (thyme) and Mentha pulegium (mentha) powders on meat colour, nutrient composition and malondialdehyde (MDA) where broiler chickens were under heat stress. Two hundred one-day-old male chicks were used in a completely randomized design with four treatments and five replicates each (10 birds per replication). Treatments were the control diet, 0.5% mentha, 0.5% thyme and 0.5% mixture of the two plants. The results showed no effect of dietary supplements on thigh meat redness and yellowness. Both plant products diminished the thigh lightness significantly compared with the control. No significant differences between treatments were observed for the ash, ether extract and crude protein content of the thigh muscle. Supplementation of thyme and mentha separately or together increased the moisture of the thigh muscle significantly, compared with the control. The combination of the plant products resulted in a higher thigh pH and significantly lower malondialdehyde (MDA) concentration in the thigh muscle compared with the control. In conclusion, dietary supplementation of thyme and mentha separately or in combination improved the meat quality of broiler chickens under heat stress through decreasing the MDA concentration and increasing the pH and moisture content of the thigh muscle

Effect of season on microbial and chemical characteristics of milk and yoghurt from sheep

The quality and hygienic status of milk are of importance for both dairy industries and consumers. In the present study, the effect of season on the quality and microbial properties of sheep milk and yoghurt produced from sheep milk were surveyed. In total, 30 sheep-milk samples were collected from January to August 2011, and yoghurt was produced from these samples. The fat content, titratable acidity and pH showed changes across the year. Seasonal variation was found to have a significant (P < 0.05) effect on nitrogen components, particularly crude protein, non-casein protein and non-protein nitrogen contents, fat content, pH and titratable acidity. Sensory analysis showed that the quality of yoghurt samples produced in winter was higher than that of yoghurt produced in summer (P < 0.05). This work showed the effect of season on chemical and sensory properties of sheep milk and yoghurt in Qazvin, Iran.

Antioxidant potential and fatty acid profile of fish fillet: effects of season and fish species

The objectives of the present study were to investigate the effect of season and fish species on the antioxidant capacity, fatty acids profile, and vitamin E content of fish fillets from Aras River. The antioxidant potential of hydrophilic and lipophilic extracts of fish fillets was evaluated. The fillet extracts of zander and bream in summer and common carp in winter had the highest antioxidant activity. Palmitic and oleic acids were the major saturated (SFA) and monounsaturated (MUFA) fatty acids, respectively. The fatty acids C22:6n3 and C20:5n3 were the most abundant polyunsaturated (PUFA) fatty acids in all the fishes. In summer, the highest levels of SFA (44.09), total PUFA (25.97), n3 PUFA (20.71) and n3/n6 ratio (4) were found in zander. In winter, the highest amounts of total PUFA and n3 PUFA were determined in silver carp, followed by zander. The highest n3/n6 ratio was also found in silver carp. The ratio of PUFA/SFA was higher in winter than in summer for all the fishes. Vitamin E content of fishes was largely varied. In conclusion, seasonal variation changed the antioxidant potential and fatty acid composition of fish fillets. Aras River fishes, especially zander, possess excellent antioxidant activity and high nutritional quality.