CHANGES IN THE ULTRASTRUCTURE OF LAMB MUSCLES AS INFLUENCED BY FREEZING AND SODIUM TRIPOLYPHOSPHATE (STPP)
Abdel-Aal, H. A., Mohamed, H. M. A.
Three lamb muscles from shoulder, Supraspinatus (SS); lion, Longissimus dorsi (LD) and leg, Biceps femoris (BF) were kept in refrigerator at 4°C for 24 hr, dipped in 10% sodium tripolyphosphate (STPP) solution for 1 min and frozen at -18°C or at - 40°C for 48 hr. Proximate composition, phosphorus, drip loss, cooking loss, pH and water holding capacity (WHC) were determined. Ultrastructure of treated and untreated muscles was studied using transmission electron microscopy (TEM). No significant (p<0.05) differences were found between moisture, protein and fat content of the three lamb muscles. Muscles treated with STPP had higher phosphorus content than that of untreated muscles. Treated or untreated frozen lamb muscles at -40°C had lower drip losses and cooking losses than those frozen at -18°C. All three lamb muscles treated with STPP had lower drip losses and cooking losses and higher pH and WHC than those of untreated ones. Results of the study suggested that STPP increased the pH, improved the WHC and decreased drip loss and cooking loss of frozen lamb muscles. Freezing at -40°C and STPP treatment maintained the well-defined all sarcomere components of lamb muscles compared to untreated muscles and frozen at -18°C.
Key words: Lamb meat, water-holding capacity, sodium tripolyphosphate, transmission electron microscopy