Effect of maltodextrin addition on moisture sorption properties of khoa

Khoa is a popular traditional Indian milk product. It is used as the base material for preparation of variety of popular sweetmeats. The shelf life of this product is limited due to its high water activity (> 0.96). In the present investigation, an attempt was made to lower the a(w) of khoa (25.62% moisture, 31.25% fat, 18.21% protein, 3.65% total ash and 21.29% lactose) by using maltodextrin (DE-16) as a humectant (concentration: 0, 2, 5 and 10%; wt/wt). It was observed that the desorption curves of the product exhibited a sigmoid shape corresponding to type II, typical of many foods. At higher concentrations of maltodextrin, the isotherms shifted to the left compared to control. Among the several models chosen to test the fitness of sorption data, Guggenheim, Anderson and De Boer (GAB) and modified Mizrahi models showed the best fit as indicated by the smallest percentage root mean square values. The monolayer moisture content increased with increasing maltodextrin level, the range being 2.85-3.29 and 3.03-3.81 g/100 g solids for the two models, respectively. Caurie's slope also increased from 0.38 to 0.44, whereas nonfreezable water decreased from 4.98 to 4.01% as the maltodextrin level increased from 2 to 10%. Other critical water sorption parameters such as number of adsorbed monolayers, density of sorbed water and surface area of sorption were also obtained.