Pink guava juice pasteurisation: Fouling deposit and cleaning studies

Abstract

Pasteurization is a common sterilization process in food industry to prolong the shelf life of the food product. However, fouling deposit problem is one of the major problems of the pasteurisation. This work provides fundamental studies on fouling deposition of pink guava juice (PGJ) and cleaning of it. A basic tubular heat exchanger set-up was used to perform pasteurization and cleaning. Pasteurisation was operated under industrial pasteurisation temperature of PGJ, which was at 93°C. Alkaline-based cleaning solution was utilised for ex-situ cleaning at different concentrations (0.2, 0.3, 0.4%v/v Na2O), 65°C and 1 l/min. Microstructure study of the deposits before and after cleaning was carried out using ESEM. Proximate analyses were performed to determine the composition of PGJ. A study on the hardness and stickiness of the fouling deposit was done using a texture analyser. The presence of seedstone in pink guava juice was analysed using a particle analyser. Cleaning performance was monitored via the changes of remaining deposit and clarity of the cleaning outlet. The findings shown that seedstone from pink guava juice ranging from 168 to 200μm and carbohydrate was found to be a major composition (47.7% of fouling deposit consists of carbohydrate). Comparison between the hardness and stickiness of the deposits at two different flow rates showed that fouling deposits were harder and denser at higher flow rate. Findings from this work provide basis knowledge for further study on fouling and cleaning of PGJ.