Assessment of microbial degradation in factory mixed juice and filtrate

Undetermined sucrose loss is a serious problem in raw-sugar manufacturing. Laboratory deterioration experiments were conducted at ambient temperature using factory mixed juice (MJ) and filtrate (FIL). Well-known metabolic products, including mannitol, lactic acid, polysaccharides, oligosaccharides and organic acids, were detected. Unexpectedly, methanol was found in both the untreated and deteriorated juices and is suspected to be caused by the action of micro-organisms on the pectin present in sugarcane juice. The deterioration rate of filtrate was generally slower than that of mixed juice, but the formation of exocellular polysaccharides was significantly higher. The mannitol concentration was a good indicator to predict sucrose loss in MJ, but not in FIL. It is suggested that an evaluation of the use of biocides, particularly in the filter station to reduce the negative impact of polysaccharides due to filtrate recycling to mixed juice, should be undertaken. Key words Mixed juice, filtrate, microbial deterioration, sucrose