Protein-Water Interaction

Solubility of proteins depends on the Ph. Caseins precipitates at ph of 4, caseins then are unsoluble. Why? Because At 4.5 the caseins reach the isoelectric point (ph at which the proteins have a neutral charge zero). The results is that phosphate groups are neutralized, and calcium bridges fall out of  each other, and the caseins  micelle fall out of each other, and the prteins will start to act differently until they precipitate.

It is possible to enhance the protein solubility by decreasing the ph. Why? Because we give them strong charge. When we protonate, by giving acid, we get positive charge. For casein it is not possible because when the micelles are disintegrated, then it is irreversible.

Water binding capacity: amount of water that can be bound in an amount of protein. Very important for meat products (weight is money). If you cook ham (pink or purple in color), during boiling we lose water binding capacity of the product because of protein denaturation. The apolar group is exposed so the water goes away. If I boil a pig leg the water will be evaporated, so we need to reduce this water loses. For this we need to increase the water binding capacities. It depends on the ph, at high ph we will have more water binding capacity (more water, but less quality)