No abstract

Rheological parameters of viscosity, gel strength, and elasticity were determined on heat-set egg albumen gels over various treatment combinations ranging from 65-9O"C, pH 6.4-9.6, and NaCl concentrations of O.O-O.lM added NaCl. Maximum viscosity was measured at a treatment combination of 77.5"C, pH 8.00, and O.lM NaCl. Elasticity and gel strength were highest in gels with a treatment combination of 85.2'C, pH 9.0, and 0.08M NaCl. Temperature had the greatest effect on all three rheological parameters. Gels heated above 80°C were of unusual character, exhibiting syneresis and shrinkage.

TWO groups of eggs were stored at 15°C for 0, 5 and 10 days. One group was stored, with the shell removed, in sterile Whirl-Pak bags. A second group was stored as intact whole -eggs. Viscosity index, apparent elasticity, and initial penetration force were determined for heat-induced (8O"C, 80 min) gels of the thick, thin and mixed albumens from each group. The rheological parameters increased with storage time, with the greater increase exhibited by the gels of the albumens that were stored as shell eggs. Solution pH was a major factor controlling these rheological properties of heated egg albumen.

Bile salt-stimulated lipase activity was monitored in fresh human milk and skim milk during refrigerated (4°C) and frozen (−20°C) storage, and in the lyophilized milks stored at −20°C and at room temperature. Following a sharp initial drop to approximately 77% of the original lipase activity, lipase was relatively stable in frozen or freeze-dried milks during 180 d of storage at −20°C. Activity losses were greatest (P < .05) in freeze-dried whole milks and skim milks stored at room temperature, approximating a 30% loss during 30 d of storage. Lipase activity was stable during refrigerated (4°C) storage of whole milk for 1 week.

Lipolysis was quantitated during storage of fluid and freezedried human whole and skim milks. Fatty acid accumulation was faster in whole fluid milk stored for 1 week at 4°C than in frozen (−20°C) samples stored for 180 d. The rapid accumulation of fatty acids during 24 h of storage at 4°C was enhanced in previously frozen milk samples. While freeze-dried whole milk showed no lipolysis when stored at −20°C, accumulation of free fatty acids was rapid in samples stored at room temperature. Fluid and freeze-dried skim milk samples exhibited no appreciable lipolysis.