Optimization of probiotic edible coating formulation and evaluation of physical and textural properties for rock candy coating

During the last decade, application of edible coatings as efficient carriers for the transfer of bioactive compounds including probiotic microorganisms has become more prominent for production of food products with stressful condition for these bacteria. In this study, the effect of optimizing a coating formulation based on carboxymethylcellulose and sucrose as carrier of probiotic strain for rock candy coating was evaluated.  Surface response method based on the central composite design was applied to evaluate the coating movement on the rock candy, the amount of coating remaining on the product after immersion and texture characteristics of the coating, such as adhesion. In addition, the textural and rheological properties of the coating solution under different concentrations of carboxymethyl cellulose and sucrose were investigated. The optimized formulation for rock candy coating was obtained with 97.9% carboxymethyl cellulose and 46.5% sucrose. The results showed that by increasing carboxymethyl cellulose concentration (from 0.8 to 1.2%) and sucrose (from 40 to 50%), the viscosity of the coating solution ranged from 9.27 to 82.62 Pa.s. Also, the flow behavior index of the coating solution confirmed the pseudoplastic behavior of the coating at carboxymethyl cellulose concentrations of 0.8 and higher. While, increasing the concentration of sucrose at a constant concentration of carboxymethyl cellulose had a greater effect on the textural parameters of the coating solution. In addition, the use of Bacillus coagulans spores in this product showed high viability of this strain (more than 90%) under product storage conditions (ambient temperature and dry place).