Phospholipids and poly(glutamic acid)/hydrolysed gluten: Interaction and kinetics

The effect of poly(glutamic acid) (PGA) and hydrolysed wheat gluten (HG) on the thermal and kinetics properties of lysophosphatidylcholine (LPC) was determined using DSC. A model system containing PGA or HG was added to 40% LPC aqueous suspension. The results from the study showed reduced ΔH values as a function of PGA molecular weight, which signified some kind of penetration of PGA or HG into the LPC bi-layer but not enough to minimise the order of LPC vesicle structure. The ability of LPC molecules to rearrange itself into a bi-layer again was evident in the emergence of crystallisation profiles in the course of the cooling cycle. The calculated activation energy (Ea) of pure LPC vesicle disruption (heating) and formation (cooling) was 696.6 and 520.4 kJ/mol, respectively. Overall, the trend of lower Ea as a function of PGA molecular weight was apparent during both heating and cooling cycles. Although, both PGA and HG reduced the Ea, HG was less effective in reducing Ea. The purported molecular interaction between phospholipids and gluten has been confirmed using FT-IR spectroscopy. The FT-IR results indicated that interactions occurred in LPC/HG blends and in model mixtures consisting of LPC/PGA with different molecular weight.