The influence of berry perforation on grape drying kinetics and total phenolic compounds

Abstract

BACKGROUND: Drying is one of the traditional methods used for the conservation of fruits. In recent years, different methods have been developed to obtain higher quality products. Chamber-drying methods with hot air at controlled temperature are reliable and easy to use. The effect of piercing the structure of grape berries on their drying time was studied experimentally during convective drying within a temperature range of 30-50 ∘ C. Experimental moisture loss results were fitted to different mathematical models, evaluated for goodness of fit by comparing their respective R 2 , 2 , and root mean square error. RESULTS: TheMidilli et al. model provided a better prediction to describe the drying of whole grapes than the other models evaluated. However, punched grapes showed a better fit for the two-term model at 30 and 40 ∘ C, and the approximation of diffusion model at 50 ∘ C. The values of effective moisture diffusivity fluctuated between 8.04 × 10 −12 and 7.31 × 10 −11 m 2 s −1 . Activation energy was 56.49 and 54.43 kJ mol −1 for whole and punched grapes, respectively. All the drying processes produced an increase of total phenolic compounds and antioxidant activity in grapes, these increases being higher in whole grape drying. CONCLUSION: The drying of punched grapes was faster and the activation energy higher than with drying of whole grapes; however, whole grapes presented more total phenolic compounds and antioxidant activity.

Effect of Intermittent Microwave Volumetric Heating on Dehydration, Energy Consumption, Antioxidant Substances, and Sensory Qualities of Litchi Fruit during Vacuum Drying

“…Litchi fruit has recently attracted the interest of processors and customers. If the concentrated fruit is transported as bulk, there is chance of massive losses due to spoilage and quality degradation [6,7,8,9]. Enhanced storage to facilitate transshipment could be achieved by dehydration, using methods such as sun drying, air drying, freeze drying, and microwave drying [7,8,9].…”

“…If the concentrated fruit is transported as bulk, there is chance of massive losses due to spoilage and quality degradation [6,7,8,9]. Enhanced storage to facilitate transshipment could be achieved by dehydration, using methods such as sun drying, air drying, freeze drying, and microwave drying [7,8,9]. Sun-drying features the pollution of pests, microbes, and dust in an uncontrollable environment [8,9,10].…”

“…Enhanced storage to facilitate transshipment could be achieved by dehydration, using methods such as sun drying, air drying, freeze drying, and microwave drying [7,8,9]. Sun-drying features the pollution of pests, microbes, and dust in an uncontrollable environment [8,9,10]. Whereas controlled dehydration such as freeze drying and air drying involve high costs and longer processing times, respectively [9,10].…”

“…Sun-drying features the pollution of pests, microbes, and dust in an uncontrollable environment [8,9,10]. Whereas controlled dehydration such as freeze drying and air drying involve high costs and longer processing times, respectively [9,10]. On the other hand, microwave-assisted drying contributes to reducing time and cost; however, it may devaluate products in case of non-uniform heat, impairing product quality [5,11].…”

Kinetics Drying of Blackberry Bagasse and Degradation of Anthocyanins and Bioactive Properties

“…TPC was estimated from a standard curve of gallic acid (y = 0.0447x + 0.0381, R 2 = 0.9953). The TPC was expressed on a wet basis as mg gallic acid equivalents (GAE)/100 gfw [22] to demonstrate the concentration-effect resulting from water evaporation.…”