| Abstract: | The effect of starch chemical modifications and hydrocolloids on the proportion of freezable water in starch gels at various moisture contents was studied. The proportion of freezable water increased with moisture content, from less than 6.1% to 84.9% (w/w) of the water fraction between 30% and 70% moisture content (wet weight basis, wwb). A transition between limited and excess water conditions was identified in the range 30‐40% moisture content (wwb), whereby the proportion of freezable water markedly increased from 6.1% to 40.4% (w/w) of the water fraction, in the case of the non‐modified starch control. At 30 and 40% moisture content (wwb), gels made of acetylated starch and hydroxypropylated starch had a significantly lower amount of freezable water than the control, in particular at 40% moisture content (wwb) the amount of freezable water was reduced from 40.4% to 15.3‐25.7% (w/w) of the water fraction. In systems with 50% moisture content (wwb) or higher, modified starches did not show a significant reduction in freezable water compared to the control. Two hydrocolloids, xanthan and carboxymethyl cellulose (CMC) used in a 40% moisture content (wwb) starch system significantly reduced freezable water from 40.4% to 23.9‐24.1% of the water fraction (w/w), at a hydrocolloid: starch ratio of 1:14 (w/w). The linear decrease in the freezable water proportion with xanthan and CMC concentration pointed to the absence of interactions between the starch and hydrocolloid fractions. Therefore, combinations of hydroxypropylated or acetylated starches and xanthan or CMC may be used to control freezable water, particularly in frozen food products with moisture contents around 40% (wwb). |
