Influence of phosphorylation on the foamability and stabilityof bovine serum albumin and citrus peel pectin (CPP) mixed foams

Bubbles are the vital component of many aerated food products which improves the properties like texture, flavour, appearance, shelf life etc. The foam stability of the food product is controlled by the protein polysaccharide complexes at the air-water interface. The biopolymers studied are Bovine serum albumin (BSA) as protein and citrus peel pectin (CPP) as polysaccharide. When this biopolymers are mixed together they give rise to complex formation which depends on different controlling parameters like pH, concentration of biopolymer and their ratios, temperature, stirring speed etc. In this study we found the effect of change in pH and the biopolymer ratio on the stability of foam. The pH levels considered here gives the idea about the interaction between protein and polysaccharide near isoelectric point (pI), below and above isoelectric point. The concentration ratios considered here are when BSA concentration is equal to that of CPP and also when it is more and less than that of CPP. Comparison performance study of native BSA and structurally modified phosphorylated BSA (pBSA) is done with measurement of foam stability and foam capacity. Our results shows that pBSA gives more stable foam as compared to BSA. Also effect of addition of CPP on stability is studied. BSA-CPP complexes shows improved stability which is further enhanced by replacing BSA with pBSA. Microscopic study of bubbles gives the qualitative nature of foam. Change in bubble size with time is observed to get size distribution of bubbles. Also surface tension experiments are carried out to confirm the interfacial stability. Rate of surface tension decrease is then correlated with foaming capacity. Proteins help to stabilize the interface by lowering the surface tension. The interfacial stability suggest that the formation of complex stabilizes the air-water interface by reducing the destabilizing phenomena of drainage, disproportionation and coalescence. This is further supported by the most stabilized concentration and pH which shows less variation in the size of bubbles.