Abstract:

【Objective】 The effect of different concentrations of calcium chloride (0.05, 0.10, 0.15, 0.20, 0.25 mol?L-1, pH 7.0) on emulsifying properties of sweetpotato protein (SPP) was investigated. 【Method】 Droplet average size (d4,3), emulsifying activity index (EAI), creaming index (CI), interfacial properties and rheological properties were respectively determined. 【Result】 The EAI of SPP emulsions decreased significantly from 30.3 m2?g-1 to 27.6 m2?g-1 after the addition of 0.05 mol?L-1 calcium chloride, while the d4,3 increased from 4.2 μm to 4.42 μm (P＜0.05). Nevertheless, with the further increase in concentrations of calcium chloride (0.10-0.25 mol?L-1), the EAI had no obvious difference (P＞0.05), but the d4,3 had a marked increase (P＜0.05). In addition, the CI, interfacial adsorbed protein concentration and initial apparent viscosity were increased markedly by adding higher concentrations of calcium chloride (P＜0.05). Furthermore, SDS-PAGE showed that Sporamin A was not easy to be adsorbed at oil/water interface, and that the high molecular polymers (＞66 kD) formed by S-S bonding existed both in oil/water interface and continuous phase of emulsions. 【Conclusion】 The binding of calcium ions to SPP could change its structure thereby affecting the emulsifying properties of SPP.

Key words: calcium chloride, sweetpotato protein, emulsifying activity, emulsifying stability, mechanism