Microbial pathogens are the cause of many foodborne diseases after the ingestion of contaminated food. Several preservation methods have been developed to assure microbial food safety, as well as nutritional values and sensory characteristics of food. However, the demand for natural antimicrobial agents is increasing due to consumers’ concern on health issues. Moreover, the use of antibiotics is leading to multidrug resistant microorganisms reinforcing the focus of researchers and the food industry on natural antimicrobials. Natural antimicrobial compounds from plants, animals, bacteria, viruses, algae and mushrooms are covered. Finally, new perspectives from researchers in the field and the interest of the food industry in innovations are reviewed. These new approaches should be useful for controlling foodborne bacterial pathogens; furthermore, the shelf-life of food would be extended.

Lactic acid bacteria (LAB) play a critical role in food production and health maintenance. There is an increasing interest in these species to reveal the many possible health benefits associated with them. The actions of LAB are species and strain specific, and depend on the amount of bacteria available in the gastrointestinal tract. Consumers are very concerned of chemical preservatives and processed foods. However, products with or processed with LAB are accepted as a natural way to preserve food and promote health. This paper aimed to review the recent data in regard to the role of probiotic LAB in the preservation of foods, in the immunomodulation in the gastrointestinal tract, and in its health benefits.The hypothetical first niche of the ancestral LAB is considered soil and plants and, subsequently, the gut of herbivorous animals [6]. The mammalian intestine is colonized by 100 trillions of microorganisms (called "microbiota") that are essential for health [7] [8]. The transition from soil and plants to the animal gut has three areas of genomic adaptation [9]: resistance to host barriers, adhesion to intestinal cells, and fermentation of some substrates in the gut. The membrane lipid composition is affected by low pH and bile salts. Microarray analysis has shown the expression of a glycerophosphatase in Lactobacillus reuteri after an acid shock, and an increase in the sensitivity to acid in Lactobacillus acidophilus [10]. Extracelullar lipopolysaccharides (LPS) also play a role in the resistance, but it is unclear [6]. The adhesion of LAB to intestinal cells is associated with the peristaltic flow, a good adherence capacity and the presence of mucins to protect and lubricate the epithelial surfaces [11]. Resident intestinal bacteria are able to inhibit the adherence of pathogenic bacteria to intestinal epithelial cells as a result of their ability to increase the production of intestinal mucins [12]. Lactobacillus plantarum increases the levels of expression of the mRNA of some mucins, inhibiting the cell attachment of enteropathogenic Escherichia coli [13] [14]. LAB have access to simple sugars and complex carbohydrates, so bacteria with genes involved in its degradation are probably in better condition to multiply in the gut [6].The resident gastrointestinal microbiota provide a microbial barrier against microbial pathogens [12]. Lactobacillus and Bifidobacterium spp. of human intestinal origin produce antimicrobial substances that are active in vitro and in vivo against enteropathogenic microorganisms involved in diarrhea [15]; both genera have the capacity for interfering with or block the pathogenic process of enteric bacterial pathogens [12]. Strains of Lactobacillus acidophilus, L. johnsonii, L. rhamnosus, L. casei, L. acidophilus, and L. rhamnosus interfere with a wide range of pathogens, such as enteropathogenic Escherichia coli, enterohemorrhagic E. coli, Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and S. flexneri [16]-[22]. Blocking the process of pathogenicity of enteric pat...

The behavior of E. coli O157:H7 strains during the storage of plain live yogurt at 4, 8, 17, and 22 ºC was investigated. Lactic acid bacteria and pH were also studied. Linear regression analysis was carried out to obtain the specific death rate, the death rate and time of death. During the 1st 24 h, the pathogenic strains decreased slightly at 4 and 8 ºC. This decrease was greater at 17 ºC, and even greater at 22 ºC. E. coli O157:H7 was not detected after 312, 168, 28, and 16 h at 4, 8, 17, and 22 ºC, respectively. Counts of Lactobacillus and Streptococcus were about 9 log CFU/g during the study. An increase was detected in the values for time of death from refrigeration to room temperatures. A decrease in the values of both the specific death rate and the death rate related with the increase of temperature was observed. Counts of E. coli O157:H7 were higher than those of nonpathogenic E. coli during the storage period at 4 and 8 ºC, showing a better and a higher adaptation capacity to acid pH environments at refrigeration temperatures. This behavior was not observed at room temperatures.

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Six batches of Oaxaca cheese (a Mexican pasta filata cheese) from 3 dairy plants were sampled and vacuum-packaged at 8°C up to 24d. Counts of principal microbial groups, pH, levels of sugars, organic acids, lipolytic and proteolytic indices, and texture, color, and meltability values of cheeses were studied at d 1, 8, 16 and 24 of storage. A descriptive sensory analysis of selected taste, odor, and texture characteristics was also carried out. The main changes in the cheeses during the storage were decreases in pH, hardness, elasticity, and whiteness, and an increase in meltability. Neither lipolytic nor proteolytic activities were evident during the storage of cheeses. Storage time resulted in a gradual quality loss of unmelted cheeses. This loss of quality might be related to the decrease of hardness and the appearance off-flavors.