Stabilization of soybean oil body emulsions using ι-carrageenan: Effects of salt, thermal treatment and freeze-thaw cycling

Soybean oil bodies and oleosins are known to be useful in foods and other emulsion systems. The influence of NaCl addition (0–500 mM), thermal processing (30, 60, 90 and 120 °C, 30 min), and freeze-thaw cycling (−20 °C, 24 h/30 °C, 2 h) on the stability of uncoated and ι-carrageenan coated soybean oil body emulsions at pH 3 and 7 was analyzed using particle electrical charge, particle size distribution, creaming stability and confocal laser scanning microscopy measurements. The stability of the uncoated emulsions to NaCl addition depended on pH, which was attributed to electrostatic screening effects. For NaCl, the uncoated emulsions were relatively stable from 0 to 150 mM at pH 3, but aggregated at ≥ 50 mM at pH 7; however, the ι-carrageenan coated emulsions at pH 3 and 7 were stable at all NaCl concentrations. The thermal stability of uncoated and ι-carrageenan coated emulsions may be relative to pH and holding temperature. Both uncoated and ι-carrageenan coated emulsions were stable at pH 7, whereas the uncoated emulsions at pH 3 became unstable when heated above 90 °C, but the ι-carrageenan coated emulsion droplets at pH 3 only extensively coalesced at 120 °C. The ι-carrageenan coated emulsions at pH 3 and 7 exhibited little droplet aggregation after three freeze-thaw cycles in the presence of sucrose. These results suggest that ι-carrageenan coated soybean oil body emulsions have similar or improved stability compared to uncoated emulsions and may be utilized as functional soy products in the food and other industries.