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CHAPTER 20. INDEXADO SCOPUS, SCIENCE DIRECT.-------------------------------------------------------------------------------------------------------------------- Food products can be subjected to contamination by bacteria, yeast, and fungi. Most of these microorganisms can cause undesirable reactions that may deteriorate flavor, odor, color, sensory, textural properties of food as well as produce its spoilage. Thus, protection of food is necessary during their preparation, storage, and distribution giving to them desired shelf life(Lucera et al., 2012).The food spoilage is currently a relevant concern because some microorganisms can potentially cause foodborne illness and economic loss associated with food loss. This has prompted the food industry to look for alternative preservatives that could enhance the safety and quality of foods (Tajkarimi et al., 2010).Microorganisms can contaminate food in various ways, including at farm level (irrigation water, field workers, insects, fecal contamination from wild animals) as well as postharvest sources (handled by workers), transport vehicles, processing equipment, wash water, and cross-contamination from other foods (Davidson et al., 2014).The demand for minimally processed, easily prepared, and ready-to-eat fresh foods, as well as globalization of food trade, and distribution from centralized processing pose major challenges to food safety and quality (Lucera et al., 2012).It has been estimated that approximately 48 million cases of foodborne illness occur in the United States annually, and has been estimated that 31% of the available food supply at the retail and consumer levels in 2010 was not consumed, which is equivalent to an economic loss of approximately USD 161.6 billion (Scallan et al., 2011; Buzby et al., 2014).Control of food spoilage and pathogenic bacteria is mainly achieved by chemical control and several preservation techniques which all together (heat treatment, salting, acidification, and drying) have been traditionally used in the food industry. Nevertheless, the use of synthetic chemicals is limited due to undesirable aspects including carcinogenicity, acute toxicity, teratogenicity, and slow degradation periods, which could lead to environmental problemssuch as pollution (Davidson et al., 2013).The negative public perception of industrially synthesized food antimicrobials has generated interest in the use of more naturally occurring compounds, receiving a good deal of attention in extensive searches, for potential use of natural food additive that could retain a broad spectrum of antioxidant and antimicrobial activity, by either decreasing the development of antibiotic resistance by pathogenic microorganisms or strengthening immune cells inhumans, while possessing the ability to improve the quality and shelf life of perishable foods (Fratianni et al., 2013).Antimicrobials are chemical compounds that are naturally present in or added to foods, food packaging, food contact surfaces, and food-processing environments to inhibit microbial growth or to kill microorganisms.The primary functions of antimicrobials in food are: (1) to control natural spoilage processes (food preservation), and (2) to prevent/control growth of microorganisms, including pathogenic microorganisms (food safety) (Davidson et al., 2013).An ideal naturally occurring antimicrobial should (1) be effective at low concentrations in its natural form, (2) be economical, (3) cause no sensory changes to the product, (4) inhibit a wide range of pathogenic and spoilage microorganisms, and (5) be nontoxic.Compounds derived from natural sources have the potential to be used for food safety due to their antimicrobial properties against a broad range of foodborne pathogens. They can be obtained from different sources including plants (e.g., essential oils of basil, thyme, oregano, cinnamon, clove, and rosemary), animals (e.g., enzymes), microbial (e.g., nisin, natamycin, bacteriosin), natural polymers (e.g., chitosan), organic acids (e.g., sorbic, propionic, citric acid),algae, and fungi (Tajkarimi et al., 2010; Ramesh and Pattar, 2010; Bhagavathy et al., 2011).Other possible antibacterial products are by-products from fruits and vegetables which could be a low-cost source of natural antimicrobials (Baydar, 2006).The use of natural or controlled microbiota to extend the shelf life and enhance the safety of foods is defined as biopreservation or biocontrol (Sobrino-Lopez and Martin-Belloso, 2008).Lactic acid bacteria (LAB) occur naturally in many food systems and have a long history of safe use in fermented foods, thus they were classed as generally regarded as safe (GRAS), and have a great potential for being used in biopreservation. On this basis, they have been approved as a food additive with GRAS status in over 50 countries worldwide.Nowadays, there are several emerging biotechnologies for natural food preservation, such as nanoparticles, bacteriophages, endolysin, quorum-sensing inhibitors. These aspects will be widely described throughout this chapter.