The Effect Of Distillers Grains On Beef Quality

Beef quality is determined by carcass maturity, firmness, texture, and color of lean, as well as the distribution of marbling within the lean. Ultimately, however, beef quality is determined by the consumer.

The consumer investigates each meat product to ensure the product they will purchase is fresh.

Quality attributes related to visual appearance of fresh beef have the most immediate impact on consumers’ purchasing decision. Consumers prefer a bright cherry red color as an indicator of freshness as compared to brown, a color often associated with spoilage.

Consumers may also look at marbling, which is an indicator of palatability.

When muscle color deteriorates, it can cause economic loss due to consumer disapproval. It is estimated that 5.4 percent of fresh meat is lost during retail display due to color related issues.

Additional factors that can affect the quality of meat, aside from genetics, are fatty acid profile, fat content, and packaging systems, all of which affect flavor and lipid oxidation.

Oxidation of lipids is one of the primary culprits of quality deterioration in meat. Lipid oxidation primarily targets unsaturated fatty acids. Animals with diets containing increased concentrations of polyunsaturated fatty acids (PUFA), such as in forage systems or alternative feed sources, may produce carcasses with altered beef quality and shelf life.

Unsaturated fats tend to be more like oils and less like solid fats, as fat becomes softer with increasing degree of unsaturation. Soft fat is undesirable as it affects product appearance and texture.

In fresh and ground beef products, soft fat causes the texture and appearance to be greasy. When cooked, the product is dryer, as the fat melts at a lower melting point. In emulsified products, such as bologna and hotdogs, greater unsaturation leads to a greasy product.

When included in the diet, distillers grains (DGs) alter the fat composition of the beef carcass. Research has shown an 18 percent increase in PUFA when comparing diets containing DGs to diets containing no DGs. As the percentage of DGs increases in the diet, so does the percentage of PUFA.

It is said that DGs alter the ability to visualize fat present in the ribeye in the beef carcass, and due to the relationship between lipid content and marbling score, this can negatively affect marbling score and thus USDA quality grade.

Finishing cattle with diets containing DGs may negatively impact color stability in retail display due to increased PUFA.

Research observing beef attributes from cattle fed DGs has shown no significant effects on fat and moisture content, sensory attributes, and shear force values of strip steaks. High levels of DGs inclusion in feedlot diets have not led to negative effects on sensory attributes, however, high levels of DGs inclusion can lower the red color values in strip loin steaks.

As mentioned by Jolene Kelzer from the U of M Beef Team in a previous Minnesota Farm Guide article, DGs are usually more cost-effective and have an equal or greater feeding value compared to corn. However, several concerns exist when feeding high levels of conventional DGs in finishing diets, such as the ones mentioned above. As a result, “next generation” ethanol co-products have received great attention as a way to alleviate some of the potentially negative meat quality effects associated with conventional DGs.

One method implemented by some ethanol companies is pre-fermentation fractionation of the corn kernel. In this process, the endosperm is separated from the corn germ and bran prior to fermentation.

Ethanol plants not only obtain greater efficiencies, but they also gain novel co-products that can be marketed for human or livestock consumption to improve their overall profitability and sustainability.

One co-product derived from this process is dried DGs containing lower fat and higher protein concentrations compared to conventional DGs. Typically, low fat DGs (LFDG) contains 39 to 44 percent crude protein and 4 to 5 percent fat, compared with conventional DGs which will contain approximately 25-30 percent crude protein and 10-14 percent fat.

Contrary to conventional DGs, no solubles are added back to LFDG. Although some research has examined the effects of feeding LFDG on cattle performance and carcass characteristics, a better understanding is needed regarding visual appearance and eating satisfaction of beef from cattle fed LFDG.

In 2010, researchers at the University of Minnesota completed an experiment involving feeding LFDG to cattle. This experiment consisted of 48 steers fed either a corn-based control diet with no distillers co-products, or diets replacing portions of dry-rolled corn with either 35 percent conventional DGs or 35 percent LFDG.

Along with traditional carcass evaluation and meat quality analysis, consumer acceptance was evaluated on fresh loin steaks and cooked sausage. Scores for overall liking, texture liking, toughness, and off flavor did not differ significantly among the steaks; however, there was a trend for consumers to give higher liking ratings for the beef from animals fed the traditional corn-based diet than for diets containing LFDG.

Consumers also liked the flavor of the steaks from steers fed the corn-based diet better than those from the LFDG treatment, however, LFDG steaks were rated the highest for juiciness.

For cooked sausage, the corn-based diet treatment group was rated the highest for overall liking and flavor liking. Sausage from steers fed the corn-based diet and LFDG diet were rated higher for texture liking and for toughness than the DGs diet.

Results of this experiment suggest LFDG may successfully replace up to 35 percent of dry-rolled corn or conventional DGS in feedlot cattle diets.

Consumer acceptability will continue to drive the beef industry. Modern feeding techniques have the potential to be detrimental to consumer acceptability. However, with the production of “next generation” DGs, such as low fat distillers grains, producers may be able to produce a product that can address visual and texture detriments. Research from the U of M has shown thus far that this product may improve appearance without any negative effects on sensory characteristics.

For more information on this or any other beef-related topic, visit the Beef Team’s web page at www.extension.umn.edu/beef

Source: University of Minnesota Beef Team