Insights to the Clarification of Sugar Cane Juice Expressed from Sugar Cane Stalk and Trash

Abstract

Processing of juice expressed from green sugar cane containing all the trash (i.e., tops and leaves, the nonstalk component) of the sugar cane plant during sugar manufacture has been reported to lead to poor clarified juice (CJ) quality. Studies of different liming techniques have been conducted to identify which liming technique gives the best clarification performance from juice expressed from green cane containing half of all trash extracted (GE). Results have shown that lime saccharate addition to juice at 76 °C either continuous or batchwise gives satisfactory settling rates of calcium phosphate flocs (50-70 cm/min) and CJ with low turbidity and minimal amounts of mineral constituents. Surprisingly, the addition of phosphoric acid (≤ 300 mg/kg as P₂O₅), prior to liming to reduce juice turbidity (≤ 80%), increased the Mg (≤ 101%) and Si (≤ 148%) contents particularly for clarified GE juices. The increase was not proportional with increasing phosphoric acid dose. The nature of the flocs formed, including the zeta potential of the particles by the different liming techniques, has been used to account for the differences in clarification performance. Differences between the qualities of the CJ obtained with GE juice and that of burnt cane juices with all trash extracted (BE) have been discussed to provide further insights into GE processing.