Irradiation impacts microbial, sensory properties of marinated steaks.

A good marinade can contain a variety of flavorings, spices or herbs. Because a marinade is also acidic, it is able to carry these flavors into foods. When we cook meats over a direct flame, heterocyclic amines (HCAs) are created. These potentially cancer-causing agents can be reduced by as much at 99% when foods are placed in an acidic marinade.

An acidic marinade acts by keeping HCAs from forming on meats. The acids in a marinade that contains vinegar, citric juices or other acidic liquids act to break down the protein chains in meats, making them more tender. Also, injecting phosphate into meat products can improve their quality. However a decrease in shelf life may result.

The objective of researchers at Texas A&M University was to evaluate the microbial, physiochemical and sensory properties of irradiated phosphate-injected beef and pork steaks during cold storage. Researchers evaluated meat quality by measuring aerobic plate count (APC) levels, lactic acid bacteria (LAB) concentrations, pH, moisture levels and color. They also engaged trained sensory panelists. Phosphate-injected samples were vacuum-packaged, frozen and irradiated to 0.0 kGy, 1.7 kGy and 3.0 kGy levels.

Irradiation extended the shelf life of phosphate-injected beef and pork. The technology resulted in a 2-log reduction in APC and LAB levels. It also stabilized the color, pH and moisture of the irradiated samples during their storage. The overall acceptance sensory scores (OASS) of irradiated raw beef were much higher than those of non-irradiated stored product.

The sensory scores of cooked beef were the same for all the treatments, however the non-irradiated samples tasted more sour than the irradiated ones. While the OASS of irradiated raw pork were relatively high during 30 days of storage, a sharp decrease in OASS of non-irradiated raw pork occurred between 10 to 30 days of storage. The OASS of raw pork slightly declined with the development of sliminess and off-odors during product storage.

The research team was able to identify cardboard-toasted odors, as well as painty-putrid odors, respectfully, in irradiated and non-irradiated raw pork samples. Although the OASS of cooked pork were the same for all treatments, the juiciness of irradiated samples was greater than that of non-irradiated product.

Overall, researchers found that irradiation was an effective way to preserve the quality of marinated meat products, extend their shelf life and cause minimal sensory and physiochemical changes in the product.

Further information. Timothy Knight, Department of Animal Science, Texas A&M University, 2471 TAMU, College Station, TX 77843; phone: [phone]; email: [e-mail].