Impact of freeze-thaw treatment on the stability of calcium-fortified soy beverages

Abstract

The objective was to study the freeze-thaw stability of soy beverages (SB) obtained from active defatted soy flour and fortified with calcium at the level of bovine milk. Calcium chloride or calcium lactate was used to fortify the SB, and a third sample without calcium was prepared as control. Sunflower oil was added as lipid phase and high pressure homogenization was performed to obtain the systems. SB were prepared without or with sucrose (5.0 and 10.0 g/100g) as cryoprotectant. In the absence of sucrose, freeze-thawing produced important aggregation of particles, observing a higher particle size increase (PSI) after 30 days of frozen storage in both SB with calcium (~700) than without addition of the cation (~500). Only the SB with 10.0 g/100 g sucrose presented an acceptable stability to freeze-thawing, and at that concentration of cryoprotectant the systems with calcium showed a lower PSI (~30) than in the absence of the cation (~100). In this case, because initial protein aggregation was favored in presence of calcium, new aggregation might have been limited during frozen storage at the conditions given by the cryoprotectant. The apparent viscosity of the samples decreased after freeze-thawing, probably because of the dehydration and compaction of aggregates.