Reduction of microbial population of fresh vegetables (carrot, white radish) and dried fruits (dried fig, dried peach) using atmospheric cold plasma and its effect on physicochemical properties

Non-observance of hygiene principles during storage causes excessive growth of microorganisms in these products and the return of export products to the manufacturer. The purpose of this research is to examine the antimicrobial effects of the jet cold plasma device and its impact on the physicochemical and sensory characteristics of a carrot, white radish, dried fig, and dried peach. For this purpose, the samples were inoculated with Escherichia coli O157:H7, Enterococcus faecalis, and Aspergillus niger. Then samples were treated with atmospheric cold plasma in the form of a jet probe and DC pulse source with 17 KV and 2.26A for 0, 3, 6, 9, and 12 min. The results showed that the rate of inactivation of microorganisms increases with increasing exposure time to atmospheric cold plasma. The maximum reduction of the microbial load was observed at 17 kV and 12 min. The resistance of microorganisms in dried fig and dried peach was higher than in carrot and white radish due to lower humidity. Also, A. niger showed the highest resistance to cold plasma compared with E. coli O157:H7, and E. faecalis. By comparing the average indices of a, and b, no significant change was observed between the treated and the control samples (p > 0.05). The texture structure remained intact after plasma application, and the plasma had no destructive effect on the texture. The samples treated with cold plasma did not show a significant effect on the physicochemical and sensory characteristics of different food products. Therefore, atmospheric cold plasma technology can be used as an efficient maintenance technique to enhance the shelf life of food products

Technological characteristics of Lactobacillus spp. isolated from Iranian raw milk Motal cheese

Lactobacilli produce large amounts of bioactive metabolites, which makes them suitable for numerous technological applications. The objective was to evaluate the technological characteristics of 16 Lactobacillus isolates from Iranian raw milk Motal cheese, including acidifying ability, production of extracellular polysaccharides (EPS), gamma-amino butyric acid, proteolytic, lipolytic, autolytic, and amylolytic activity, resistance to acid conditions as well as biogenic amine production and susceptibility to antibiotics. Most of the examined strains presented high proteolytic and autolytic activity. Low acidifying ability was observed for all isolates, except for L. plantarum (M19) which reduced pH to 4.6 after 12 h. The highest proteolytic activity (30-mm clear halo) was observed for L. brevis (M4). Lipolytic activity was never observed and most of the isolates did not produce biogenic amines. The highest percentage of antibiotic resistance (87%) was recorded for kanamycin. All isolates were sensitive to chloramphenicol except L. brevis (M11). EPS production was detected in all strains, most strains (90%) produced mucoid EPS and 10% secreted EPS with a “ropy” character. Acid resistance showed all isolates were able to grow at pH 3.0 and 4.0. L. brevis (M4) presented the best technological characteristics and is proposed for inclusion as co-culture in the production of Motal Cheese.Peer reviewe