Venture | Chemical Food Preservatives

_We receive a lot of questions from people who want to introduce new products without any "bad chemicals" or, perhaps, natural products with a clean label. There are certainly options to avoid the use of antimicrobial agents, either via processing techniques or by formulation, but, in some cases, the use of chemical preservatives is necessary to ensure the safety of a food product. We will review the characteristics and applications of two very common, safe, FDA-approved antimicrobial compounds available for food use.

Sodium Benzoate and Benzoic Acid: These two compounds are related because sodium benzote produces benzoic acid once it is dissolved in water. Benzoic acid is the compound with the antimicrobial properties, and is found naturally in cranberries, prunes, greengage plums, cinnamon, ripe cloves and apples.

Sodium benzoate is the sodium salt of benzoic acid and is preferred over benzoic acid in many food applications because it is 180 times more soluble in water. There is a marked pH effect for this preservative: the lower the pH, the more effective it is. Sodium benzoate will only work if the food product has a pH below 4.5; that is, if the food is naturally acidic or has been acidified.

For example, at pH 3.0 you only need approximately 0.05% of the compound to achieve the same antimicrobial effect as pH 4.0 and 0.1% benzoate. Optimum functionality occurs when the pH is between 2.5 and 4.0.

Sodium benzoate is used in fruit products, jams, relishes, beverages, dressings, salads, pie and pastry fillings, icings, olives and sauerkraut, and is against yeasts, some bacteria (foodborne pathogens but not spoilage bacteria) and some molds. Sodium benzoate is a white granular or crystalline powder, odorless, inexpensive (at the usage level) and should be stored in a cool, dry place in watertight containers, if possible. It should be used at low levels to avoid possible off-flavors in some products. The maximum level allowable by law is 0.1%.

Sorbates: This family of compounds is available as sorbic acid, potassium sorbate, sodium sorbate or calcium sorbate. Sorbic acid is the compound with the antimicrobial properties but its salts (sorbates) are used in many cases due to differences in solubility.

Potassium sorbate is the potassium salt of sorbic acid, and is much more soluble in water than the acid. Potassium sorbate will produce sorbic acid once it is dissolved in water and is the most widely used food preservative in the world. It is effective up to pH 6.5 but effectiveness increases as the pH decreases.

Potassium sorbate has about 74% of the antimicrobial activity of the sorbic acid, thus requiring higher concentrations to obtain the same results that pure sorbic acid provides.

Potassium sorbate is effective against yeasts, molds, and select bacteria, and is widely used at 0.025 to 0.10 % levels in cheeses, dips, yogurt, sour cream, bread, cakes, pies and fillings, baking mixes, doughs, icings, fudges, toppings, beverages, margarine, salads, fermented and acidified vegetables, olives, fruit products, dressings, smoked and salted fish, confections and mayonnaise.

Potassium sorbate is a white crystalline powder, inexpensive (at the usage level), with basically no noticeable flavor at normal usage concentrations. In wine processing, sorbates are used to prevent refermentation. Maximum level allowable by law is 0.1%.

It is important to know that the addition of sodium benzoate and/or potassium sorbate to a food product will raise the pH by approximately 0.1 to 0.5 pH units depending on the amount, pH, and type of product. Additional adjustment of the pH might be needed to keep the pH at a safe level.

In many food products, sorbate and benzoate are used together to provide greater protection against a wider variety of microorganisms. This only makes sense if the pH of the product is below 4.5.

If preservatives are used in a food, they must be declared in the list of ingredients on the label, along with a short explanation of intended use, such as "preservative," "mold inhibitor," or "to retard spoilage," etc.

NOTE: Benzoate and sorbate at the levels used in food products will not control the growth of high levels of microorganisms. Therefore, always use good quality ingredients and follow good manufacturing practices to keep the microbial load to a minimum.

Igoe, R. S and Hui, Y.H. 1996. Dictionary of Food Ingredients - 3rd ed. Chapman & Hall, New York.

Branen, L.A. and Davidson, P.M. 1983. Antimicrobials in Food. Marcel Dekker, New York.

Chemical Food Preservatives: Bonzoate & Sorbate