Albedo hydrolysis modelling and digestion with reused effluents in the enzymatic peeling process of grapefruits

Abstract

Until now, the optimisation of enzymatic peeling of grapefruit in the reactor has been obtained as the result of the semi-qualitative effects of enzyme activity. This work is an attempt to obtain quantified data. The reuse of enzymes to reduce costs in this process is unprecedented in the literature and is the aim of the present work. The optimal conditions determined for the maximum albedo degradation were a temperature of 40.6 °C and a time of 13.1 min in an enzymatic concentration of 0.067 mL enzymatic preparation per gram of peel in each litre of citrate buffer solution. The decrease in relative enzymatic activities in reused effluents was determined, as was the increase in activity when the enzymes were purified. These increases were 15.5% for polygalacturonase and 15.4% for cellulase activity. Optimal temperature, time and the ratio between peel mass and the enzymatic preparation volume were the best conditions for obtaining good peeling efficiency. The effluents from the enzymatic peeling process of the grapefruit still contain appreciable enzymatic activity after the digestion process. Thus, reusing these effluents while maintaining peeling efficacy and a subsequent recovery of the active enzymes by ultra-filtration of the effluents is the way to improve the efficiency of the process.