Quality Evaluation by Using Laser of Red Grapes during Microwave Drying

Abstract

Raisins are one of the methods of preservation of grapes to increase the shelf life of fruits. The present study focused on the microwave drying of grapes, to produce raisins and determine its effect on Physico-chemical and optical properties of raisins during the drying process. To measure the main dimensions, mass, acidity, and total soluble solids as Physico-chemical, while the optical properties such as reflection and absorption of grapes using laser technique. Also, to find the relationship between the laser reflection of grapes during microwave drying and changes in shrinkage, moisture content, mass, acidity, and total soluble solids during the grape drying process. Obtained results showed that there is an inverse relationship between the percentage of reflection of the laser beam from the surface of the grape fruits and the percentage of loss moisture, TSS, pH, and volume of fruits. Relationship between laser reflection of grapes and physic-chemical properties at drying time of 10, 20, 30, 40 and 50 min, the percentage laser reflected from the surface decreases, of about 38, 32, 23, 21, and 15%, due to the moisture loss percentage of 14, 32, 63, 75, and 80%., increasing the TSS percentage of 6, 18, 37, 49, and 61%, increasing the pH percentage of 4, 11, 15, 21 and 26%, and increasing the volume percentage of 16, 41, 55, 67 and 74%, respectively. The microwave drying showed a better quality profile. This can be useful for farmers and small-scale farmers to produce good quality raisins.