Food manufacturers want their products to meet internal quality standards while conforming to rules and regulations set by regulatory agencies. They also desire that their products are stable during storage and capable of resisting breakdown and spoilage. Several factors may contribute to product deterioration which may fall under three main categories, i.e., physical, chemical, and microbiological changes. Understanding these changes will help food manufacturers design strategies to extend the shelf life of their food products.  

Physical Changes

Changes related to the physical properties of stored foods include absorption of moisture, separation, growth of ice crystals, and mechanical damage (Kong and Singh, 2016). 

  1. Moisture Absorption  

If your business is concerned with dehydrated products such as dried fruits and powders, moisture absorption is one of the critical factors to consider. Moisture will negatively affect product stability by attracting microbial contaminants and is likely to cause caking and loss of flow properties in flour products.

2. Separation

The separation of food components may produce an off-putting appearance and texture. This problem is common in emulsified foods that undergo breakdown. For example, the cream may separate from the liquid, producing separate layers (Hu et al., 2016).

Chemical Changes

Browning and changes in flavor, aroma, and nutrient loss indicates that chemical changes have occurred. 

3. Browning

This change is due to the oxidation of enzymes such as polyphenol oxidase, or non-enzymatic browning due to Maillard reaction. Maillard browning reaction (reaction of proteins and reducing sugars) is a leading cause of nutritional loss, degradation of compounds, off-colors, and flavor damage in foods (Singh and Cadwallader, 2003). 

4. Lipid Oxidation

For meat-based products, lipid oxidation remains the primary concern during storage. It occurs when polyunsaturated fatty acids react with free radicals to form hydroperoxides and secondary rancid-smelling by-products (Vercelloti et al., 1992). 

5. Retrogradation

In foods rich in starch, such as bread, the most common determinant of wholesomeness is texture. Have you ever wondered why your bread hardens or becomes rubbery after you’ve left it on the table or more so when you put it inside the refrigerator? This phenomenon is called staling. It is the migration of moisture from gelatinized starch, allowing the starch molecules to revert to a more ordered form (Wang et al., 2015). The result is a product with a hard and crumbly texture. Waxy and high-amylopectin starch ingredients are used to reduce staling due to their retrogradation-resistance properties. 

Microbial Changes

The presence of microbes significantly alters the physical and biochemical composition of food products. Changes may include a lowering of pH, formation of off-odor, and changes in color and texture. 

6. Bacteria

Bacteria such as Salmonella spp., Staphylococcus aureusClostridium botulinum, and other pathogens are major food safety concerns (Steele, 2004). They are particularly problematic because they are often undetectable unless they produce sensory changes. For example, in canned foods, C. botulinum can cause bulging of cans.

7. Yeast and Mold

If you have ever experienced opening a bottle of non-carbonated juice and felt a gush of gas escaping, there is a chance that the product has gone through unwanted fermentation. Yeast and molds are the known culprits responsible. They are used to formulate cheeses and wines, but in other products where they are unwanted, they cause spoilage (Steele, 2004). Spoilage by fermentation is associated with the production of organic acids and carbon dioxide.

Summing it Up

Several factors affect food product shelf life. I have highlighted the most important ones for you to keep in mind. Learning which ones are critical to your niche will help you design new products that meet your consumers’ needs and standards set by regulatory agencies.  

References

Fu, B., & Labuza, T. P. (1997). Shelf-life testing: procedures and prediction methods. In Quality in frozen food (pp. 377-415). Springer, Boston, MA.

Hu, Y. T., Ting, Y., Hu, J. Y., & Hsieh, S. C. (2017). Techniques and methods to study functional characteristics of emulsion systems. Journal of food and drug analysis, 25(1), 16-26.

Kong, F., & Singh, R. P. (2016). Chemical deterioration and physical instability of foods and beverages. In The stability and shelf life of food (pp. 43-76). Woodhead Publishing.

Singh, T. K., & Cadwallader, K. R. (2003). The shelf life of foods: an overview. Department of Food Science and Human Nutrition, 1302 West Pennsylvania Avenue, University of Illinois.

Steele, R. (Ed.). (2004). Understanding and measuring the shelf-life of food. Woodhead Publishing.

Vercellotti, J. R., St. Angelo, A. J., & Spanier, A. M. (1992). Lipid oxidation in foods: An overview. Agricultural Research Service, U.S. Department of Agriculture, Southern Regional Research Center

Wang, S., Li, C., Copeland, L., Niu, Q., & Wang, S. (2015). Starch retrogradation: A comprehensive review. Comprehensive Reviews in Food Science and Food Safety, 14(5), 568-585.

Kline Umali
Kline Umali is an avid food science writer from the Philippines. He has a master's degree in food science with a minor in microbiology.
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