Food preservation

• Currently, there are various types of chemicals that can be utilized to prolong the shelf life of food products.
• Sodium aluminum sulfate, potassium aluminum sulfate, ammonium aluminum sulfate and aluminum sulfate are among the commonly used forms of aluminum sulfate.
• For citrus fruits and vegetables, aluminum ions are used to enhance texture.
• These chemicals react through diverse functions.
• Most of these chemicals are categorized as food additives.
• According to Food Act 1983, Food Regulations 1985, food additives are safe ingredients that are intentionally added to food to influence the characteristics of the food.
• Preservative is any substance that, when added to food, can inhibit or prevent the process of decomposition, fermentation, or acidification of such food.
• Antioxidant is any substance that, when added to food, can slow or inhibit the development or rancidity or other deterioration in food caused by oxidation.
• Based on its functionality, the main categories of preservation using chemical preservatives are antimicrobial substances and quality-improving substances.
• Antimicrobial substances act to reduce the microbial threat to the shelf life of the product.
• Sulfites or sulfur dioxide, nitrite & nitrate salts, sorbic acid, propionic acid, acetic acid, and benzoic acid are commonly used antimicrobial substances.
• Sulfite/ Sulfur dioxide has been used as a general food preservative for a long time.
• The form used is SO2 gas, and salts of Na or K Sulfide, bisulfite or metabisulfite.
• In aqueous solution, sulfur dioxide and sulfite salts will form (H2SO3) (sulfurous acid) and bisulfite (hydrogen sulfite) and sulfite ions.
• The percentage of the presence of ionic forms in the solution depends on the pH.
• At pH 4.5 or lower, sulphuric acid and HSO3- forms are the major forms.
• The antimicrobial effect of SO2 is by sulfuric acid.
• SO2 is more effective when the pH is lower than 3.0.
• Sulfuric acid is better able to penetrate the cell wall.
• Sulfuric acid inhibits yeast, fungi and bacteria at different degrees.
• Sulfuric acid also has other preservative effects besides antimicrobials.
• Sulfite/ Sulfur dioxide can inhibit non-enzymatic browning.
• Sulfite also inhibits enzymatic browning.
• Nitrite & nitrate salt can inhibit the growth of microorganisms including Clostridia.
• Nitrite in meat will form nitric oxide.
• Nitric oxide will react with heme to form nitrosomyoglobin.
• Nitrosomyoglobin is pink in color, preferred for meat products; example - cured meat.
• Nitrosomyoglobin also contributes to the taste of pickled meat.
• Sorbic acid and its salts (example: potassium and sodium sorbate) are often used as antifungal substances.
• Examples of antioxidant agents include Butylated Hydroxyanisole (BHA), Butylated Hydroxytoluene (BHT), tert-Butylhydroquinone (TBHQ), and ascorbic acid.
• Examples of antibrowning substances include citric acid, malic acid, and phosphoric acid.
• Metal ions, especially iron and copper, will catalyze oxidation.
• Another mechanism of oxidation inhibition is by preventing metal ions from catalyzing oxidation.
• Some processing methods negatively affect the texture of the product, for example, the canning process produces soft and less hard plant tissue.
• Orthokuinone will form a polymer and produce brown melanin.
• Chelating agents or sequestrants, such as citric acid and EDTA (ethylene diamine tetra acetic acid), are used to avoid metal ions catalyzing oxidants.
• Antioxidant agents act with free radicals, reducing the number of free radicals available for oxidation and the production of other free radicals.
• The factors that need to be considered during the selection of antioxidants for a food system are effectiveness, convenience, and cost.
• SO2 and sulfites can also inhibit PPO activity.
• The first three types of browning are non-enzymatic, while PPO browning is enzymatic and often occurs in fruits and vegetables.