Comparative studies of structural and thermal gelation behaviours of soy, lentil and whey protein: A pH-dependency evaluation

A growing global concern about human health, environment, and sustainable food supplies has motivated researchers to find new alternatives to dairy proteins. To investigate the effects of pH and protein varieties on the thermal gelation behaviors, plant protein (soy and lentil) and dairy protein (whey) were subjected to a variety of pH treatments. SDS-PAGE showed that only partial subunits of soy and lentil protein were involved in disulphide bonded aggregate formation regardless of pH, and that of whey protein was inhibited at acidic conditions and facilitated at higher pH. Both soy and lentil protein did not form self-standing gels at pH 5.0, while whey protein did, and all proteins displayed different morphologies as pH moved away from 5.0, from white, opaque, and heterogeneous to relatively transparent and homogeneous. Soy protein exhibited its optimal gel performance at pH 9.0 (storage modulus of 946.05 Pa) with the highest content of alpha-helix, intramolecular beta-sheet, and intermolecular/aggregated beta-sheet, while whey protein demonstrated its peak gel performance at pH 7.0 (storage modulus of 26271.90 Pa). Lentil protein displayed the best gel performance at pH 3.0 and was comparable to that of whey protein (storage modulus of 5366.00 and 4965.00 Pa, respectively). These findings confirmed that lentil protein has the potential to substitute whey and soy protein in formulations of diversified food products in some specific pH systems. This work highlighted the importance of pH control to achieve desired gelation performance and offered valuable insights for selecting suitable protein alternatives in formulating plant-based food products.