Optimization of Hemicellulose Coating as Applied to Apricot Drying and Comparison with Chitosan Coating and Sulfite Treatment

Abstract

AbstractDrying of hemicellulose‐coated apricots was compared to sulfuring and chitosan coating. Air velocity, temperature and hemicellulose concentration were optimized using the Box–Behnken response surface methodology against total color change (ΔE*), yellowness (Δb*) and final moisture content. Drying kinetics were evaluated by Newton, Page and Logarithmic models. Diffusion coefficient, activation energy and rehydration rate were calculated. The optimal drying conditions were found as 1 m/s of air velocity, 80C of air temperature and 3% (w/v) hemicellulose coating, which gave values of 15.2, −8.3 and 26% for ΔE*, Δb* and final moisture, respectively. The hemicellulose‐coated apricots indicated better color values than the uncoated and chitosan‐coated samples, while sulfuring still attained the best color values. Drying kinetics were best described by the Logarithmic model at 60 and 70C and Page model at 80C for 2% hemicellulose coating. Effective diffusion coefficients ranged from 2.499 to 5.742 × 10−9 and the activation energy was calculated as 33.78 kJ/mol. The hemicellulose‐coated apricots had slightly higher rehydration rate than the uncoated and sulfured samples. In conclusion, hemicellulose coating showed a promise for use in fruit drying.Practical ApplicationsTreatment of fruits with sulfur compounds (sulfur dioxide gas, sulfite solutions, etc.) prior to drying is a common practice to minimize loss in the quality of the dried fruit. In fact, use of these chemicals in foods is limited and the allowed concentration varies with countries worldwide in the range of 300–2,000 mg/kg. Because sulfur compounds can cause health problems, use of natural, renewable and abundant preservatives will be a viable alternative. In this respect, hemicellulose extracted from agricultural and food wastes can provide a low‐cost preservative and can be utilized to preserve fruits during drying. The results of this study will also provide a basis to utilize hemicellulose in various fruits other than apricots during drying and meanwhile will help reduce the concentration of sulfur compounds in foods.