Effect of muscle type and food deprivation for 24 hours on the composition of the lipid fraction in muscles of Large White pigs.

The present study was designed to examine the lipid composition of a predominantly glycolytic (M. longissimus lumborum, LL) and a predominantly oxidative (M. semispinalis capitis, SC) muscle sampled at slaughter from Large White pigs fed or deprived of food for 24 h. The intramuscular lipid content was almost four-fold higher in the red SC than in the white LL. When expressed on a muscle tissue basis, the results indicated that the LL had significantly lower amount of tri-, di- and monoglycerides, free fatty acids, cholesterol and phospholipids than the SC. In both muscles, phosphatidylcholine represented the major constituent of the phospholipid fraction. The difference in phospholipid content between the LL and the SC was significant only for cardiolipin, phosphatidylethanolamine and phosphatidylinositol. When expressed on total lipid basis, the results showed that the SC contained significantly lower amount of phospholipids and higher amount of triglycerides than the LL, thus suggesting that the influence of muscle type on the content of intramuscular lipid was primarily due to a difference in the amount of triglycerides. Food deprivation for 24 h resulted in a significantly higher content of free fatty acids, as expressed on a muscle tissue basis, in both muscles. Relative to total lipid, food deprivation resulted in increased levels of free fatty acids and monoglycerides only in the LL. These results suggest that food deprivation for 24 h induced lipolysis in muscle, as evidenced by a modification in the relative composition of the neutral lipid fraction, but that this effect was muscle-dependent.