Modified distillers grains, glycerin in finishing diets reduce oxidation in meat

Jul 29, 2011
by DTN

Research has shown that adding distillers grains to livestock diets can cause quicker oxidation or brownish discoloration of meat.

Since appearance of meat is the major influence on consumer purchasing decisions at the grocery store, some University of Minnesota (U of M) researchers set out to determine whether the addition of crude glycerin to beef diets can counteract the effect of distillers grains on meat color.

Much research has been done on the change in fatty acid profile in swine fed distillers grains, according to Kaitlyn McClelland, graduate research assistant for the U of M’s Department of Animal Science. Little research has been done, however, on the effect in beef cattle.

Distillers grains change the amount of saturated versus unsaturated fat within the animal, McClelland said.

“One of the problems with distillers grains is that it will increase the unsaturated fat in swine and beef, though it’s not as noticeable in beef,” she said. “When you feed glycerin, it increases some of the saturated fat, so it will bring the levels back to normal.”

When animals are fed something that causes them to deposit more saturated fat, it can potentially increase the rate at which the meat will oxidize or turn brown, which in turn reduces the meat’s shelf life.

“Unsaturated fats have double bonds, two bonds linking carbons. Saturated fats have just one,” McClelland explained. “Double bonds are more likely to oxidize, so foods with a lot of unsaturated fat, even though unsaturated fat is healthier, will go rancid more quickly.”

The goal of the research was to evaluate the use of modified distillers grains (MDGs) and crude soybean glycerin to see how that affected beef cattle performance and growth in finishing diets, and also to determine how that affected beef quality, McClelland said.

The U of M research team conducted a feed trial using 48 cross-bred steers and heifers. The experimental diets replaced steam-flaked corn with 35 percent MDGs, 10 percent glycerin or a combination of both. The researchers evaluated strip steaks, ground beef and bologna produced from the cattle carcasses for moisture loss, meat color and consumer sensory acceptability.

The team observed no differences in hot carcass weight, ribeye area, backfat, USDA yield or quality grade or marbling score. Also, no differences were observed in objective tenderness scores of the steaks, and no differences in lightness, redness or yellowness in the color values for steaks or ground beef. Consumer color scores for lean color, surface discoloration and overall appearance were also not affected.

The research indicated that the addition of MDG and glycerin did not negatively affect beef quality or color. Since the team was able to achieve the same color scores feeding modified distillers and glycerin, that means beef producers can feed those products in place of corn and get the same result.

“You can feed 35 percent MDG and 10 percent glycerin and still have a very consistent beef product, the same as feeding a traditional corn or soybean diet,” McClelland said. “We found no differences between the control treatment and the experimental treatment.”

McClelland said the researchers will be continuing similar research, pending funding, and would like to further research fat and fat oxidation. She said the U of M research team is in talks with the Minnesota Soybean Council for research funding. — DTN