Effect of lipid edible coating (Glyceryl monoestearate and Carnauba wax) on shelf life of raisin

Raisin is a principal traditional export product of Iran and has occupied a special position in the foreign trade of the country. During storage period, the product turns sticky and hard due to exudates syrup and moisture loss. To overcome this problem the application of edible coating suggests being of proper assistance. Edible coating may enhance the boundary layer resistance resulting enhanced shelf life of product. In this research the method of Accelerated Shelf Life Testing (ASLT) used for evaluation of storage and sensory properties (texture, colorو taste and overall acceptability) of raisin. Raisin was treated with coating materials based on lipid (glyceryl monoestearate and carnauba wax) with 150 ppm essential oil of thyme (thymus vulgaris) and stored at 20, 35 and 50oC for 12 weeks. During this period of storage sensory properties were evaluated and estimate the modeling shelf life of raisin. Results showed that coating, affect on texture and color significantly and caused increasing shelf life of raisin. Temperature and storage time also showed significant effects on total sensory attributes. Maximum shelf life (394 days) determined at 20 oC for carnauba wax coating with essential oil of thyme based on overall acceptability and linear regression and second order function had best fit with R2≥0. 94 for all of treatments.