Antimicrobial Natural Products

Natural antimicrobials are secondary metabolites that can be found in plants, animals, and microorganisms.Plants, especially herbs and spices, are been given more attention in natural antimicrobial research, however; this chapter focuses on the newly discoveries in fruits and vegetables. Microorganisms that are been used in food fermentation also produce different antimicrobial metabolites including organic acids, hydrogen peroxide, ethanol, and diacetyl in addition to bacteriocins. Products of animal origin such as tissues, milk, and eggs contain different antimicrobial agents that are mainly in the form of peptides (polypeptides). In most cases natural antimicrobials are extracted and purified to be tested or applied to food products. Extraction and purification may alter the chemical structure of natural antimicrobials and affect their functionality. Thus, an extraction method with minimal processing such as juice or mechanical direct extraction seems to be more promising to avoid possible alteration or destruction of active ingredients. Activity of natural antimicrobials could be also influenced by the original source, time of harvesting, and stage of development. In food applications, these natural antimicrobial compounds could be influenced by food components, processing, and storage. On the other hand, increasing level of consumer concerns on chemical antimicrobials and increasing resistance of pathogenic microbes have turned the attention of the scientific communities towards studies on the potential antimicrobial activities of natural products. Natural antimicrobials are generally recognized as safe and they appear to be the most promising solution for microbial resistance and could best meet with consumers’ demands for healthier foods. This chapter discussed the recent insights regarding the antimicrobial activities of natural products, extraction methods, mechanism of action, and factors influencing the antimicrobial activity.