STARCH IN THAI CANE SUGAR MANUFACTURING PROCESS

摘要

A presence of starch in the sugar manufacturing process can detrimentally affect the production efficiency of sugar factories by lowering the boiling house recovery and quality of sugar products. The situation of starch contamination in the Thai sugar industry was evaluated by estimating the starch content in raw sugars using the starch-iodine method. Around 70% of produced raw sugar contained starch in the range of 200 to 500 mg/kg sugar, which could be troublesome to the sugar industry, especially sugar refineries. To effectively minimise this problem, the starch balance in the manufacturing process of sugar factories during the milling season 2002-2003 was conducted. The contents of starch in process materials including raw materials, intermediates and products were estimated. Our studies show that several cane varieties commonly grown in Thailand contained starches in juice at approximately 150 to 1300 mg/kg brix, depending on variety, harvest time and the millable cane portions. These starches with round-shaped granules (3 to 5 microns in diameter) could be mainly found in first expressed juice. During the manufacturing process, there was no significant removal of starch; the contents of starch found in mixed juice, clarified juice, filtered juice and raw syrup were similar and around 30-40% of starch present in mixed juice was occluded within the sucrose crystal of raw sugars. This ratio could be used to establish the critical limit of starch in mixed juice (to be less than 800 mg/kg brix) for controlling the product quality (starch content in raw sugar ≤ 250 mg/kg sugar). Canes with higher starch content should be rejected unless appropriate treatment for starch removal has been implemented.