Optimisation of concentration of cucumber juice using progressive freeze process as a non-thermal process

Abstract

Concentration process of cucumber juice is an essential step in cucumber extracts and juice production in the industry in order to minimise the volume and weight for storage and handling purposes. Progressive freeze concentration (PFC) is a non-thermal concentration process that can be used in which water content in the juice will be frozen out in the form of an ice block layer by layer. The ice crystallisation process forms ice crystal lattice that rejects all impurities and in turn will leave behind highly concentrated cucumber juice. This research aimed to optimise the operating parameters involved in concentration of cucumber juice via PFC. The operating parameters involved were operation time, initial concentration, coolant temperature and speed of stirrer. Optimization of the PFC process was carried out with the effective partition constant, K as the indicator of the performance by using Response Surface Methodology (RSM) in STATISTICA software. Highest total phenolic content (TPC) increment achieved was 38.83 % with operating condition at -12 °C of coolant temperature, 413 rpm of stirrer speed, 37.8 min of operation time, and 11 mg/mL of initial concentration and lowest effective partition constant, K value obtained was 0.261 with operating condition at - 13.8 °C of coolant temperature, 435 rpm of stirrer speed, 30 min of operation time, and 10.5 mg/mL of initial concentration. The results were supported with good value of R-squared obtained which was 0.85899 for K-value and 0.79365 for TPC increment. The linear effect of operation time was found to be the most significant factor to the response in this study. This work has clearly shown that PFC has potential to be used in concentration of cucumber juice as a non-thermal operation.