Studies on Ceramic Membrane, Sonication and Hybrid Processes for the Clarification of Vegetable Juices and Extracts

Abstract

Functional fruits and vegetables are important sources to provide bioactive compounds and natural phytochemicals and thereby nurture human metabolism and enhance immunity. Thus, significant emphasis is required towards the production of fruit and vegetable juices and extracts to serve as health and nutritional supplements.

Among alternate methods of fruit and vegetable juice/extract processing, enzymatic pretreatment, centrifugation, membrane separation, mechanical and ultrasound assisted agitation could be regarded to be the most inexpensive methods in comparison with the expensive technologies such as freeze processing, thermal processing, supercritical extraction etc.. Therefore, among the non-thermal processing methods that are gradually gaining popularity, microfiltration (MF), ultrafiltration and ultrasound-assisted extraction (UAE) could be considered as highly competitive due to their inherent advantages such as high efficiency, low cost, easy operation, low temperature requirement, low solvent requirement (for extraction), low pressure (for membrane separation) and ease of cleaning (for membrane separation). Further, few studies elaborate towards hybrid processes (such as centrifugation-MF and UAE-MF) to achieve the desired targets of better clarification, enhanced yield etc..

Considering these issues, the Ph.D. thesis devotes towards the development of microfiltration and ultrasound assisted extraction methods for the clarification and production of vegetable juices and extracts. The optimality of microfiltration system has been addressed in terms of alternate membrane morphologies, variable trans-membrane pressure and feed constitution. Similarly, a design of experiments approach has been followed to address optimality of ultrasound assisted extraction systems. Among many varieties of vegetables available for such investigations, the thesis devotes towards bottle gourd juice and bitter gourd extracts due to their excellent nutritional supplement and medicinal applications. Further, the thesis gains its prominence due to the potential to achieve clarified bottle gourd juices and bitter gourd extracts as viable products in the commercial arena.