Studies on factors affecting beef taste and the effects of dietary glycerin on growth performance and carcass characteristics in Korean cattle steers

Abstract

Beef marbling score and quality grade positively affect meat sensory characteristics, including tenderness, juiciness, flavor, and overall palatability. Korean cattle beef is well known for good palatability because of the high quality grade and thus high marbling. Limited information is available and variability exists in data on the associations among marbling score/quality grade, meat characteristics, and sensory traits in Korean cattle beef. Korean consumers prefer Korean cattle beef to domestic Holstein and imported beef because they believe that the palatability of Korean cattle beef is superior to that of other breeds. Limited information is available on the factors that affect the preference of Korean consumers for Korean cattle beef over other breeds. Two studies (study 1 and 2) were conducted to elucidate 1) the associations among quality grade/marbling and various carcass characteristics and sensory traits in Korean cattle beef, and 2) the factors that contribute to differences in the sensory traits of longissimus thoracis of different breeds. Glycerol, a by-product with biodiesel, also known as glycerin, serves as gluconeogenic substrate in the liver and kidney, and it has an energy value similar to corn on a pound-for-pound basis in dairy and feedlot cattle. Although many studies were conducted for the effect of glycerin on carcass composition and characteristics in various animal diets, the outcomes were not consistent. Also, limited information is available for effects of glycerin supplementation on meat characteristics in Korean cattle steers. Two studies (study 3 and 4) were conducted to identify 3) the effects of dietary glycerin replacement on growth performance, carcass characteristics and sensory traits in Korean cattle steers fed diets based on the similar TDN level between experimental diets, and 4) the effects of crude glycerin supplementation on growth performance and carcass characteristics in Korean cattle steers fed diets based on the different TDN level between experimental diets.

1. Comparison of carcass and sensory traits, fatty acid profiles and volatile compounds among quality grades in longissimus dorsi and semimembranosus muscles of Korean cattle steer This study was performed to compare carcass traits, sensory characteristics, physicochemical composition, nucleotides and collagen content, free amino acids, content and composition of fatty acids (FA), and volatile compounds among four quality grades (QG1++, 1+, 1, and 2), and to understand their association with carcass characteristics in longissimus dorsi (loin) and semimembranosus (rump) cuts of Korean cattle steers. This study confirms that marbling score (MS) and intramuscular fat (IMF) content are major positive determinants of QG in Korean cattle beef. Numeric values of tenderness, juiciness, and overall acceptability in loin tended to be highest in QG1++, and those of juiciness and overall acceptability tended to be lowest in QG 2. Juiciness and overall acceptability were strongly correlated with QG. Our results demonstrated that QGs are linked to sensory traits. However, the nucleotide contents including inosine monophosphate (IMP) may not be major factors determining meat palatability of Korean cattle beef in this study. Glutamic acid and proline were significantly associated with tenderness, juiciness, and overall acceptability, although they did not differ significantly among QGs. In addition, beef QGs affected the compositions and contents of FAs and volatile compounds in loin and rump. Loin FA percentages, especially those of oleic acid (C18:1n9) and monounsaturated FA (MUFA), generally increased with increasing QGs. Some volatile compounds in loin and rump varied with QGs and were positively or negatively correlated with flavor.

2. Comparison of reducing sugar content, sensory traits, and fatty acids and volatile compound profiles of longissimus thoracis among Korean cattle, Holsteins, and Angus steers This study was performed to compare intramuscular fat (IMF) and reducing sugar contents, sensory traits, and fatty acid (FA) and volatile compound profiles in longissimus thoracis (LT) among Korean cattle (KC), Holstein (HO), and Angus (AN) steers. The IMF, reducing sugar content, and sensory traits of the LT varied among KC, HO, and AN steers. The KC LT had the highest IMF and reducing sugar contents, and the best sensory traits (flavor, tenderness, juiciness, and overall acceptance). The IMF and reducing sugar contents were positively correlated with all of the sensory traits, suggesting that these factors may positively affect beef flavor. Palmitic acid (C16:0), oleic acid (C18:1n9), and monounsaturated FA (MUFA) may positively affect sensory traits, whereas linoleic acid (C18:2), and polyunsaturated FA (PUFA) may negatively affect sensory traits. The percentages of different volatile compounds in the LT also varied among the three breeds. The KC had the highest percentage of volatile compounds, including acetaldehyde, 3-methyl butanal, and 3-hydroxy-2-butanone, and these compounds were positively correlated with flavor. Our results demonstrated that variations in IMF, reducing sugar content, and FA and volatile compound profiles may contribute to differences in the sensory characteristics of the LT among breeds. The results of this study enhance our understanding of the association of reducing sugar and volatile compound contents with the sensory traits of beef. This information may help in determining beef palatability.

3. Effects of dietary glycerin replacement on growth performance and rumen and carcass characteristics in Korean cattle steers The study was performed to evaluate the effect of 3% dietary glycerin replacement on growth performance, blood metabolites, ruminal fermentation characteristics, carcass characteristics and sensory traits, hepatic gluconeogenic gene expression, and muscle glycogen contents in Korean cattle steers. Glycerin replacement in the finishing diet of Korean cattle steers had no impact on weight gain, average daily gain, and feed efficiency except for increase in average daily concentrate intake. This increased intake may be attributed to the sweet taste of glycerins property. Glycerin replacement did not affect carcass characteristics, chemical and physico-chemical composition, reducing sugar, glycogen, collagen, nucleotides, fatty acid, volatile compounds, and sensory traits in the longissimus thoracis. These results indicate that the glycerin inclusion level (3%) may be not enough to improve animal performance and carcass characteristics. In addition, feeding concentrate containing 3% of glycerin did not result in detrimental effects on growth performance, ruminal fermentation, animals physical condition, and metabolism. This is important not only on animal performance and carcass characteristics but also for sustainable and economic aspects because glycerin is a biodiesel residue and it can potentially partially replace some expensive ingredients such as corn, molasses, distillers dried grains with solubles as an energy source for beef cattle.

4. Effect of dietary crude glycerin supplementation on performance, blood metabolites, ruminal fermentation parameters, and carcass characteristics in Korean cattle steers This study was performed to evaluate the effect of dietary glycerin supplementation on growth performance, blood metabolites, ruminal fermentation characteristics, carcass characteristics and sensory traits, glycogen content in liver and muscle, and hepatic gluconeogenesis gene expression in Korean cattle steers finished in feedlot. This study confirms that dietary glycerin supplementation at 6.4% of DM did not lead to detrimental effect on feed intake in Korean cattle steers. Both glycerin and corn starch supplementation did not improve average daily gain and feed efficiency in Korean cattle steers. Glycerin supplementation also did not affect rumen fermentation characteristics, carcass characteristics, IMF content, reducing sugar content, glycogen content in both liver and muscle, and sensory traits of Korean cattle steers. Both glycerin and corn starch supplementation did not affect serum glucose concentration at initial and 8th week, but glycerin supplementation slightly increased the average serum glucose concentration at 16th week. Although glycerin supplementation had no impact on carcass and meat quality, glycerin could be potentially considered as a good energy source to maintain the animals metabolism in finishing Korean cattle.