Effects of soy proteins and hydrolysates on fat globule coalescence and meltdown properties of ice cream

The effect of soy protein isolate and its hydrolysates on ice cream mix stability and melt-down properties of ice cream were investigated. Ice creams were made with 10% milk fat, 3.5% protein and 34.3% total solids, and all contained 0.15% added monoglycerides. The proteins used were native soy protein isolate (NSPI), commercial soy proteins isolate (CSPI), soy protein hydrolyzed by pepsin (SPHPe), soy protein hydrolyzed by papain (SPHPa) and skim milk powder (SMP). Ice cream with SPHPe containing the highest relative composition of beta-subunit showed good mix emulsion stability and rapid melting rate because beta-subunit cannot be displaced by the monoglycerides, leading to lack of fat partial coalescence in the ice cream. SPHPa ice cream exhibited comparable functionality to SMP in rheological and meltdown properties. SDS-PAGE results indicated that alpha subunit, alpha' subunit, acidic subunit, basic subunit and small molecule polypeptide were displaced by monoglycerides during ice cream aging. Selective hydrolysis of soy protein can be used for ice cream with sufficient fat partial coalescence and good melt-down rates.