Optimization of concentrating process using rotary vacuum evaporation for pineapple juice

Abstract

Pineapple juice has high water content which limits the storage duration and increases the transportation cost. This work was aimed to optimize the concentrating process of pineapple juice using a rotary vacuum evaporation statistically. The concentrating process was varied at temperatures (50–70 °C) and time (30–120 min) at the fixed pressure, 200 mbar in 13 experimental runs. The results found that rotary vacuum evaporation was able to reduce 44.3 % water content and increase total sugar content from 7.70 to 14.65 °Brix. The significant increment of total acidity from 4.43 to 10.91 g/100 mL could be due to the presence of citric acid and other organic acids in concentrated pineapple juice. The browning index of concentrated juice was also increased from 0.101 to 0.344 with the formation of hydroxymethylfurfural (1.55 mg/mL) as byproduct. Hydroxymethylfurfural is a carcinogenic substance which usually produced automatically in carbohydrate rich foods during thermal processing. Nevertheless, the content of hydroxymethylfurfural is still far below the permittable limit of 40 mg/kg as specified for table honey. Based on the response surface methodology, the optimized concentrating parameters were 60 °C for 75 min at 200 mBar using a central composite design.