GHAZALEH HEDAYATI*, ALI MOHAMADI SANI
*Corresponding author
Department of Food Science and Technology, Quchan Branch, Islamic Azad University, Quchan, Iran

Abstract

The aim of this study was to optimize proteolytical activity of melon juice by concentration using response surface methodology. Melon juice concentrates (40±1, 52.5±1, 65±1°Bx) at three different temperatures (40, 50, 60°C) were studied for their proteolytic activity by the milk clotting activity (MCA) and gelatin digestion unit (GDU) analytical methods. Results showed that the MCA and GDU increased by increasing concentration rate and decreasing temperature. The maximum MCA (511U/ml) and GDU (162/gm) was obtained at 40°C and 65°Bx. The data generated from the experiments was analyzed by regression analysis. Linear and square effects of temperature were significant (p<0.05). Concentration had no square effect (p>0.05) on the proteolytical activity. The coefficients of determination (R2) for the fit were 99.38% and 99.27%.

INTRODUCTION 

Fruit juices in the market generally exist as two types: fresh juice and juice concentrate (25). Production of juice concentrate is a suitable method for consistent product quality. Concentration is achieved via several methods such as evaporation, freezing and osmotic techniques. Concentration of fruit juices not only provides microbiological stability, but also leads to economical packaging, transportation and distribution of the final products. However, the concentration of fruit juices is a susceptible process. Evaporation is probably the oldest method of concentration. Furthermore, it is considered to be the best developed, economical and widely used method for concentration of liquid foods. Heat sensitivity of the product is of particular importance in selecting the evaporator, as it affects the quality of the concentrate (17). So the concentration is mainly carried out worldwide by vacuum evaporation (12).
Melon (Cucumis melo L. 2n=24) is an economically important vegetable which is subdivided into six cultivar groups Cantaloupensis, Inodorus, Flexuosus, Conomon, Chito-Dudaim and Momordica (10). In Iran, the Cantaloupensis a ...