Deterioration of cane juice—sources and indicators

Abstract

Laboratory tests, comparing microbial, enzymic, and chemical deterioration of sucrose in factory cane juice, were undertaken. Heat (boiling temperature) and biocide treated juice, as well as untreated juice, were deteriorated at 27 °C (to simulate factory ambient temperature) in an incubator over 71 h. The biocide-treated juice retained its dark brown colour, fresh odour, initial pH and °Brix levels over 71 h. In strong contrast, after 71 h the untreated juice was light brown, had a strong alcohol odour and markedly lower pH and °Brix levels. The colour of the heated juice decreased only after 23 h, and the juice was viscous after 71 h and had neither a fresh nor alcoholic odour. Sucrose, glucose, and fructose were analyzed using gas chromatography. Over the first 14 h of deterioration, 93.0% of sucrose losses were microbial, 5.7% enzymic and 1.3% were chemical (acid degradation). Ion chromatography with integrated pulsed amperometric detection (IC–IPAD) was used to simultaneously determine ethanol, mannitol, and oligosaccharides in deteriorated cane juice. The rate of formation of mannitol, produced from the reduction of fructose by mannitol dehydrogenase in dextran forming Leuconostoc bacteria, was much higher than associated oligosaccharides or ethanol formation. A further investigation of the use of mannitol as a sensitive indicator of future dextran-related processing problems at the cane factory is warranted. Ethanol was shown not to be very useful as an indicator of Leuconostoc bacterial cane deterioration.