Food Structure


The effects of different pH's (4 .5 , 5.5, 6.5 and 7.5) and temperatures (30-80 •c) on the functional properties and microstructure of chicken breast salt soluble protein (SSP) in 0.6 M NaCI were investigated. Protein solubility decreased from 98% at pH 6.5 to less than I% at pH 4.3 and below. Salt soluble protein at pH 4.5 produced a discontinuous gel which could not be measured by back extrusion and had an expressible moisture above 80% at all heating temperatures . Aggregated globular microstructures were observed at pH 4.5 by scanning electron microscopy (SEM). Thin-sectioned images as seen by tran smi ssion e lectron microscopy (TEM) suggested th e glob ules were composed of loosely packed long protein filaments approximately 20 nm in diameter. Gels at pH 5.5 had the highest viscosity index between 45-80 •c and thickest SSP st rands as viewed by SEM and TEM, but expressible moisture approached 80% when they were heated to 70 °C or above. Gels at pH 6.5 and 7.5 ex hibited similar expressible moisture (approximately 40%), viscosity index and a regular, con tinuous network of lin ear globular st rands at 65 °C by SEM. Mi crost ructures at pH 5.5, 6.5 and 7.5 changed with temperature, with maximum strand diameters observed at 65 •c. Changing pH altered SSP solubility which influenced gel texture, water retention and microstructure.

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