Comparison of the non destructive acoustic and the mechanical destructive methods to assess the storage life of bruised apple var. Golab coated with methyl cellulose

In this research the storage life and quality of sound and bruised apple var. Golab Kohanz coated with methyl cellulose were assessed using non-destructive ascoustic and destructive mechanical methods. Apples were received a controlled impact by destructive pendulum. Half of the sound and bruised apples were coated with methyl cellulose. Coated and uncoated apples were stored at 2oC and 85%RH for 10 weeks. The elastic modulus, acoustic index, dominant frequency of the acoustic spectrum, flesh firmness, weight loss, total soluble solid, titrable acidity, pH, respiration rate based on the amount of CO2 produced and skin and flesh color of the stored apples were measured during ten weeks of storage at one week intervals. The results showed that there is a good correlation between all the mechanical and acoustic indexes, representing the reduction of apple firmness during storage. Applying methyl cellulose coating decreased weight loss of bruised apples up to 40%. The respiration rate of coated sound and bruised apples decreased significantly and the respiration peak was not observed. The color differences and the browning index of the flesh were much lower in coated samples after the respiration peak, while coating had no significant effect on the skin color of the samples. The discoloration of the flesh due to the bruise and the volume of the bruise were lower significantly in the coated samples. The overall results showed that the ripening of the sound and bruised apples was slower in coated samples compared to the uncoated fruit and acoustic index is a low cost destructive method for evaluating the quality of fruit and an appropriate substitute for the destructive qualification methods.