Rheological properties of acid-induced soy protein-stabilized emulsion gels in the absence and presence of N-ethylmaleimide

The storage modulus (G') and fracture properties of the non-treated and NEM-treated emulsion gels were investigated in the absence and presence of unadsorbed soy protein aggregates (USPA). In the absence of USPA, a decrease in the G' of emulsion gels was observed after NEM treatment. However, in the presence of USPA, the addition of NEM only slightly decreased the G' (p < 0.05). For both non-treated and NEM-treated emulsions, a similar to 63-folds higher G' value was obtained after the USPA addition. These results revealed the presence of sulphydryl group - disulfide bond interchange reactions at ambient temperature and under acidic conditions. In the absence of USPA, the sulphydryl group - disulfide bond interchange reactions was the main interactions responsible for the higher G' values of non-treated emulsion gels, but for the emulsions with USPA presented, the large quantity of non-covalent interactions (e. g. hydrophobic group & hydrogen bonds) is the main interactions responsible for the aggregation and gelation of emulsion droplets. In the presence of USPA, the sulphydryl group e disulfide bond interchange reactions formed in the non-treated emulsion gels did not increase the final G' but increased the stability of network. A power law relation was observed between the USPA concentration and the final G', as well as between the oil volume fraction and the fracture stress/strain. (C) 2012 Elsevier Ltd. All rights reserved.