Notes - Chemical Preservatives and Natural Antimicrobial Compounds

Notes - Chemical Preservatives and Natural Antimicrobial Compounds

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CHEMICAL PRESERVATIVES AND NATURAL ANTIMICROBIAL COMPOUNDS Food antimicrobials are chemical compounds added to or present in foods that retard microbial growth or kill microorganisms thereby resisting deterioration in safety or quality. Chemical Preservatives /Natural Antimicrobial Compounds Most food antimicrobials are only bacteriostatic or fungistatic not cidal. Cellular targets of food antimicrobial include the cell wall, cell membrane, metabolic enzymes, protein synthesis systems and genetic systems. Factors Affecting Activity The effectiveness of food antimicrobials depends on factors associated with the food product such as its storage environment, its handling, and the target microorganisms. Microbial factors such as inherent resistance, initial number and growth rate, interaction with other bacteria, cellular composition and injury affect activity Factors Affecting Activity Intrinsic factors affecting activity include composition, pH, buffering capacity, oxidation reduction potential, and water activity. pH is the most important factor influencing the effectiveness of most food antimicrobials. Another important factor affecting activity is polarity. Antimicrobials must be lipophilic to pass through the cell membrane and also soluble in aqueous phase. Traditional Antimicrobials Antimicrobials are classified as traditional when they have been used for many years or they have been approved for many years by many countries, or they are produced by synthetic means or are inorganic (as opposed to natural extracts or organic compounds). Many synthetic antimicrobials ironically are found in nature. Organic Acids and Esters Many organic acids are used as food additives but not all have antimicrobial activity. The most active antimicrobials are acetic, lactic, propionic, sorbic and benzoic acids. Citric , malic, and fumaric have limited activity and are used a favorings. THE ACTIVITY OF ORGANIC ACIDS IS HIGHLY pH DEPENDENT. Organic Acids and Esters The activity of organic is related to pH and that the undissociated form of acid is primarily responsible for antimicrobial activity. Therefore, in selecting an organic acid for use as an antimicrobial food additive, both the product pH and the pK a of the acid must be taken into account.
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Organic Acids and Esters In the undissociated form, organic acids can penetrate the cell membrane lipid bilayer more easily. Once inside the cell, the acid dissociates because the cell interior has a higher pH than the exterior. Since protons generated by the organic acid inside the cell must be extruded by using energy in the form of ATP, the constant influx of these protons depletes cellular energy. Organic Acid and Esters
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Notes - Chemical Preservatives and Natural Antimicrobial Compounds

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