Studies were undertaken to ascertain the relative contribution of polysaccharide formation and inversion losses responsible for quality deterioration in cane juice after extraction. These included mixing of effective biocide (sodium azide, l% w/v) to destroy all microbes and heating of juice (at 100°C for 2 min) just after milling. The juice was heated to inactivate acid invertase(s) present in milled juice. The addition of biocide in freshly milled cane juice, sustained the quality with not much change in recoverable sugars and juice pH after 96 h of storage, while in the untreated juice there was a drop of over 2.0 units in recoverable sugars and a sharp decrease in juice pH. The dextran, reducing sugars and specific activity of acid invertase were significantly low in biocide treated juice as compared to the untreated control. Although the contents of reducing sugars and acid invertase activity were low in initially heated juice after 96h of storage, the formation of dextran was quite high with more decrease in recoverable sugars, increase in juice viscosity and drop in juice pH as compared to the biocide treated juice. Microbial infections which lead to formation of dextran and consequently increased viscosity, are largely responsible for post-harvest quality deterioration of cane juice.