Effect of combined treatments of ultrasound and ultraviolet radiation for preservation of pineapple juice

Abstract

Ultraviolet (UV) treatment is an alternative tool for food preservation. UV radiation inactivates microorganisms by DNA denaturation and is widely used for disinfect water and liquid food products. The application of UV radiation is limited due to its low penetration depth. Ultrasound (US) is another promising technique which can be employed for preservation of fruit food products. The microbial inactivation in US is mainly due to cavitation. Cavitation leads to destruction of cells, production of free radicals, formation of shock waves and denaturation of enzymes.US preserve the organoleptic and nutritional qualities of food products. Even though UV radiation and US treatment has their own potential as a preservative method, but application of any single treatment would not be competent enough to kill all microorganism. Therefore, a new concept has been extensively evaluated to combine ultraviolet and ultrasound. This combined treatment would optimize the strength of each individual treatment and reduce each of their individual weaknesses. This present study envisages development of US assisted UV radiation treatment system for pineapple juice and evaluation of developed system in retaining the quality characteristics and microbial safety. The system consists of ultrasonic bath with chiller (Sonicator), storage tank, ultraviolet treatment system and recirculation system. The treatments were carried out with three different US time intervals 10 min, 20 min and 30 min and three different UV dosages 1000 mJ/cm2 , 1300 mJ/cm2 , and 1600 mJ/cm2 . Combined US and UV treatments with US exposure 20 min and UV dosage 1600 mJcm-2 were found to be superior based on physicochemical, microbiological and organoleptical characteristics.