Changes in the Lipids of Pork and Beef during Heat Treatment at High Temperature

Abstract

Changes in the lipids of pork and beef, sliced and ground, were studied during heat treatment at higher temperature. Fat portions of the samples were trimmed, then they were sliced about 8 mm in thickness, vacuum-packed in flexible retort pouches (13×17cm), and cooked to a core temperature of 124°C at the F values ranging from 4.6 to 32. Finely ground pork and beef were also cooked in the same manner. TBA value of pork increased during the heat treatment and was higher in the ground meat than in the sliced one. However, there was no relationship between the degree of increase in TBA value and the increase of F value. Contrary, TBA value of beef decreased during the heat treatment. The contents of total lipids (TL) in pork and beef were 3-4% and 8-10%, respectively, and almost unchanged during the heat treatment, while those of polar lipid (PL) slightly increased. In the PL of pork and beef lysophosphatidylcholine (LPC) and lysophosphatidylethano- lamine (LPE) were formed during the heat treatment and increased with the increasing of F value. LPC and LPE were found at higher levels in beef than pork. Free fatty acid (FFA) both in pork and beef decreased during the heat treatment, though some of PC and PE were hydrolysed to LPC and LPE, respectively. No outstanding change was found on triglyceride (TG) composition on the basis of total carbon number of acyl chain during the heat treatment at the F values of less than 8.6 for pork and 12 for beef. However, when the samples were cooked at the F values of 21 or higher, TG of C-52 and C-54 decreased, while those of C-48 and C-50 increased. This observation suggests that intra-and/or inter-molecular rearrangement of TG occurs during the heat treatment. Little change was observed in the fatty acid compositions of TL, PL, and non-polar lipid (NL) in pork and beef during the heat treatment, with the exception of C20:4 in PE which decreased.