Microwave modifications of sugar cane to enhance juice extraction during milling

Abstract

Mechanical shredders are used to rupture the storage parenchyma cells in the pith of the sugar cane stalk to facilitate extraction of the cane juice through the milling tandem. The cane shredder accounts for approximately 20% of the total energy balance in a sugar mill. Shredder hammers also wear quickly during the crushing season and need to be regularly maintained or replaced. These maintenance events interrupt the production schedule of the mill. Studies reported in the literature have revealed that applying intense microwave energy to wood can significantly reduce other processing energy requirements such as pulping or drying. Depending on the amount of energy applied, microwave treatment can reduce the density of Eucalyptus obliqua wood by up to 12%. This change in density reduces wood hardness by about 54% compared to untreated wood, resulting in substantial energy savings for processes such as reducing logs to wood pulp for paper manufacture. Other published studies have shown that microwave treatment significantly enhances the extraction of terpenes from caraway seed. Microwave treatment also increases essential oil yields (up to 30%) from peppermint and rosemary and reduces processing time. Cell rupture during microwave treatment was shown to playa significant role in enhancing extraction. This paper reports scoping studies in which microwave treatment was applied to small samples of sugar cane. Sugar juice diffusion was significantly enhanced by the microwave treatment and juice yields from crushing cane billets in a custom built press increased by a factor of 3.2 compared to the untreated control samples.