Proteolytic Modifications in Pork Fillet and Shank during Storage

V. TSVETKOVA, L. GEORGIEVA, L. ANGELOV and T. MARINOVA
Institute for Cryobiology and Food Technologies, BG - 1404 Sofia, Bulgaria

Abstract

TSVETKOVA, V., L. GEORGIEVA, L. ANGELOV and T. MARINOVA, 2005. Proteolytic modifications in pork fillet and shank during storage. Bulg. J. Agric. Sci., 11: 405-410

Investigations are made on pork fillet and shank, produced by two metabolically different types of muscle tissue, respectively musculus longissimus dorsi (mld) and musculus triceps brachii (mtb). The selective solubility of protein in both products is monitored when stored in aluminum vacuum packages at 2°C for a period of 20 days after the date of production. The contents of total protein, lipids, moisture and pH-values were determined for the fillet and shank in fresh condition, as well as after storage for 10 and 20 days. It is established, that the salt soluble proteins (fraction 1) in the fillet and shank have similar contents and remain unchanged when stored in a refrigerator. The relative share of the urea soluble protein (fraction 2) in both products is the highest, significantly decreasing (P < 0.01) on the 10th and 20th day of storage of the fillet, whereas for the shank the decrease (P <0.01) is established on the 20th day after the date of production. The results show that the fraction of insoluble proteins (fraction 3) significantly increases in pork fillet and shank after a storage period of 20 days, mainly on the account of the decrease of the share of fraction 2. The different rates of decomposition of proteins in both products after technological treatment and refrigerated storage can be referred to the different structural contents of glycolytic and (mld) oxidative (mtb) type of muscles.

Key words: salt soluble proteins, urea soluble proteins, fillet, shank