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The ability to extend shelf life is important for not only the consumer, but also food manufacturers, retailers, and restaurants.
The Oxidation Process
It takes only a small amount of oxygen to initiate oxidation of a food item. The overall mechanism of lipid oxidation consists of three phases:
- Initiation: the formation of free radicals; and
- Propagation: the free-radical chain reactions; and
- Termination: the formation of non-radical products.
When auto-oxidation starts, free radicals or chemical by-products, such as peroxides, aldehydes, and ketones form. These by-products that are formed can cause off odors or alter flavors in a food product.
Oxidation can also negatively impact the appearance of food, resulting in browning or pigment loss. It also can cause the reduction of nutrients such as essential fatty acids and vitamins.
Combating oxidation is where antioxidants come into play. They help prolong the process before oxidation of food sets in. As hydrogen donors, antioxidants donate a hydrogen to quench the free radicals being formed and delay or slow down the next phase of the reaction, propagation. This ultimately can delay rancidity.
Several factors or catalysts can drive oxidation in a complex food matrix. They include the presence of oxygen, light, heat, metal ions (such as copper and iron), enzymes, water activity, chlorophyll, or simply time.
Different food products will vary in their susceptibility to oxidize, whether faster or slower. For example, baked goods that are high in polyunsaturated fatty acids are more susceptible to oxidation than baked goods that contain hydrogenated fats. Additionally, baked items that contain seeds and nuts, particularly if they have been chopped or sliced, would be more susceptible to oxidation. This is due to the increased surface area, which allows more opportunity for oxygen to propagate the harmful oxidation cycle.
Besides antioxidants, there are other mechanisms to help fight rancidity in food. These include novel packaging, processing, or changes in distribution conditions, like refrigeration. Additionally, minimizing light, heat, and exposure to air can aid in increasing the shelf life of a food product.
With that said, there are a few issues with these other methods: the alternatives are more expensive, can be difficult to implement, and may not provide the desired shelf life. Whereas, antioxidants can be added at very low concentration levels, are easy to incorporate into food, and can be better and more cost-efficient solutions.
Evolution of Shelf Life Extenders
Traditional antioxidants such as BHA, TBHQ, and BHT have been the antioxidants of choice for use in fats and oils for many years. They remain benchmarks for their ease of use, effectiveness, and acceptable cost. Vitamin-based antioxidants, such as ascorbyl palmitate, are generally perceived by the public as natural, but are actually synthetically produced.
Today’s focus on clean label solutions have challenged the antioxidant industry to ideate new solutions such as extracts high in antioxidant activity, like rosemary, green tea, and the use of tocopherols.
The selection of an antioxidant must be considered carefully relative to the functionality of the lipid system as well as the desired attributes of the finished food product. The shelf life required for long distribution, storage conditions, and packaging could determine which antioxidant is recommended.
Natural vs. Traditional Shelf Life
The modern producer enjoys a wide range of ingredient and packaging solutions designed to help control oxidation. Antioxidants, both natural and traditional, are just one proven solution that can be used in conjunction with other shelf life solutions.
Natural. Natural shelf life solutions can be an advantage for food producers who are trying to market their products to a certain demographic or make certain label claims. While the FDA does not define the term “all natural,” consumers have varying ideas on what a cleaner label means to them.