Sodium benzoate and potassium sorbate preservatives in food stuffs in Iran

A high-performance liquid chromatography method was applied for the determination of the levels of benzoate and sorbate in 400 food samples, including pickled cucumbers, canned tomato pastes, sour cherry jams, soft drinks, fruit juices and dairy products (UF-Feta cheeses, Lighvan cheeses, lactic cheeses, yogurts and doogh). The results showed that 270 (67.5%) of all samples contained benzoate ranging from 11.9 to 288.5 mg kg⁻¹ in lactic cheese and fruit juice, respectively. The levels of sorbate in 98 (24.5%) of the samples were 20.1 to 284.3 mg kg⁻¹ in doogh and fruit juice, respectively. Moreover, benzoate was detected in all dairy products ranging from 11.9 mg kg⁻¹ in lactic cheese to 91.2 mg kg⁻¹ in UF-Feta cheese. A low concentration of benzoate could originate naturally, due to specific biochemical mechanisms during cheese, yogurt and doogh maturation. In conclusion, a minimum level for benzoate in dairy products should be defined in the legislation. © 2015 Taylor & Francis

New approaches to modeling Staphylococcus aureus inactivation by ultrasound

Abstract Ultrasound (US) is an effective technology to inactivate vegetative microorganisms in foods. In this study, the effect of amplitude levels (0.4, 7.5, and 37.5), duty cycles (0.3:0.7 s, 0.7:0.3 s, and 0.9: 0.1 s) and time (0, 2, 4, 6, 8, 10, 12, and 14 days) of US on inactivation of Staphylococcus aureus were investigated. In addition, genetic algorithm-artificial neural network (GA-ANN) and adaptive neuro-fuzzy inference system (ANFIS) models were used to predict inactivation of S. aureus. The GA-ANN and ANFIS were fed with three inputs of amplitude levels, duty cycles, and time. The inactivation rate of S. aureus was increased by increasing the amplitude levels, and the best inactivation was obtained at a 37.5 μm amplitude for which the S. aureus population was reduced to 2.59 CFU/mL. The high inactivation of S. aureus was achieved under a duty cycle of 0.7:0.3 s with reduction of the population to 1.49 CFU/mL. The developed GA-ANN, which included 17 hidden neurons, could predict the S. aureus population with a coefficient of determination of 0.986. The overall agreement between ANFIS predictions and experimental data was also very good (R 2  = 0.979). Sensitivity analysis results showed that the amplitude level was the most sensitive factor for prediction of S. aureus. Keywords Fuzzy inference Inactivation Staphylococcus aureus Ultrasoun

High-efficiency anti-enterotoxigenic activity of Lactobacillus on staphylococcal enterotoxins biosynthesis

Staphylococcal enterotoxins (SEs) are the main reason for the pathogenicity of Staphylococcus aureus, and finding a suitable inhibitory agent against their production is necessary for the food industry. The aim of this study was the finding a mixture of Lactobacillus strains with the highest anti-enterotoxigenic activity (AEA) against the production of A and B enterotoxins from S. aureus grown on medium including sub-minimum inhibitory concentrations of cell-free supernatant (CFS) of three Lactobacillus species using by real-time PCR and statistical method of mixture design. Results showed the antibacterial activity (AA) of CFS of Lactobacillus strains on S. aureus was higher than their microbial suspensions. Among the Lactobacillus isolates evaluated in this study, CFS of L. brevis isolated from fermented olive had higher AA against S. aureus and its A and B enterotoxins production. A synergistic inhibitory effect was observed between CFSs of L. brevis isolated from fermented olive, L. plantarum isolated from fermented olive and L. brevis isolated from pickled garlic. The highest AEA was observed by treatment with a mixture containing 45 CFS of L. brevis isolated from fermented olive, 27 CFS of L. plantarum isolated from fermented olive, and 28 CFS of L. brevis isolated from pickled garlic. © 2020 Elsevier Lt

New approaches to modeling Staphylococcus aureus inactivation by ultrasound

Ultrasound (US) is an effective technology to inactivate vegetative microorganisms in foods. In this study, the effect of amplitude levels (0.4, 7.5, and 37.5), duty cycles (0.3:0.7 s, 0.7:0.3 s, and 0.9: 0.1 s) and time (0, 2, 4, 6, 8, 10, 12, and 14 days) of US on inactivation of Staphylococcus aureus were investigated. In addition, genetic algorithm-artificial neural network (GA-ANN) and adaptive neuro-fuzzy inference system (ANFIS) models were used to predict inactivation of S. aureus. The GA-ANN and ANFIS were fed with three inputs of amplitude levels, duty cycles, and time. The inactivation rate of S. aureus was increased by increasing the amplitude levels, and the best inactivation was obtained at a 37.5 μm amplitude for which the S. aureus population was reduced to 2.59 CFU/mL. The high inactivation of S. aureus was achieved under a duty cycle of 0.7:0.3 s with reduction of the population to 1.49 CFU/mL. The developed GA-ANN, which included 17 hidden neurons, could predict the S. aureus population with a coefficient of determination of 0.986. The overall agreement between ANFIS predictions and experimental data was also very good (R2 = 0.979). Sensitivity analysis results showed that the amplitude level was the most sensitive factor for prediction of S. aureus. © 2015 Springer-Verlag Berlin Heidelberg and the University of Mila

High efficiency pigment production from Micrococcus roseus (PTCC 1411) under ultraviolet irradiation

The present study reports on the production of natural pigment from Micrococcus roseus under ultraviolet (UV) irradiation treatment. Response surface methodology (RSM) was used to evaluate the effect of process variables on the production of natural pigment. The four independent variables including irradiation time (10–80 s), irradiation distance (5–45 cm), incubation temperature (5–35 °C), and incubation time (12–72 h) were studied. According to the results, the optimal production of natural pigment condition was obtained with an irradiation time of 15.67 s, irradiation distance of 30.45 cm, incubation temperature of 21.36 °C, and incubation time of 47.76 h. At the optimum condition, total carotenoid (TC) and the biomass dry weight (BDW) was determined 7.20 mg/L and 7.17 g/L, respectively. The experimental values under optimal condition were in good consistent with the predicted values, which suggested UV irradiation is an efficient treatment to enhance the production of pigment from M. roseus. © 2016 Elsevier Lt