Antioxidants are substances able to prolong the shelf life of foods by protecting them against deterioration caused by oxidation, such as fat rancidity and colour changes (Regulation UE 1333/2008).

The lipid oxidation causes significant changes in foods such as structure, appearance, nutritional profile, as well as worsening and decreasing shelf life. In some foods, for example in cheeses, lipid oxidation is limited and sometimes wanted, as it provides flavoring compounds that give cheese its characteristic taste and fragrance. In most food lipid oxidation is harmful because it develops off-flavors (rancidity)—for example, from the milk fat could be released butyric acid, which has a typical nauseating smell and acrid taste followed by sweetish aftertaste.

There are different rancidity processes of fatty substances that can be distinguished by origin and type of produced compounds. They can be caused by reaction of oxygen present in air, by enzymatic activities (oxidase, decarboxylase, lipoxidase), or by enzymatic and oxygen activities.

Considering all factors described before, a complete antioxidant should be composed of one or more primary antioxidants (able to fix oxygen preferentially), one synergist (or secondary antioxidant, especially acids widely present in nature as citric, lactic, and tartaric acid), one sequestering metal traces agent (chelates like EDTA). The combined action of these antioxidants would permit the use of lower concentrations of each individual antioxidants.

Among the antioxidants most widely used in the dairy industry there are ascorbic, lactic, citric, tartaric and phosphoric acids, tocopherols, or vitamin E, gallates.

There are some types of rancidity, like the hydrolitic rancidity due to lipase, which cannot be prevented by adding antioxidants. If the correct application of good manufacturing practices and production processes, like heat treatments and water separation (e.g., anhydrous butter) are not enough to prevent the appearance of this type of rancidity, then antimicrobial agents could be added. To achieve even better results, the processed food should be marketed protected from light.

Antioxidants are very susceptible to environmental conditions such as light, temperature, and extreme pH levels. Advanced microencapsulation technology solutions, protecting ingredients, such as lipids, from light and temperature, by coating and forming small capsules, which permit a longer shelf life and more stable final product, are now available.

Spray drying is the most common method for encapsulating antioxidants in hydrocolloid matrices and is commonly paired with gum arabic as a wall material.

Furthermore, encapsulation is used to mask unpleasant feelings during eating, such as bitter taste and astringency of polyphenols and other compounds that show high antioxidant activities.

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