Effects of seasonal variations of sugarcane stalk and extraneous matter quantity and quality as they affect recoverable sugar, starch and fiber: Part Ⅰ

摘要

There are presently worldwide trends to manufacture high quality raw sugars for supply to refineries, e.g., very high pol and very low color (VHP/VLC) raw sugars, and to use sugarcane extraneous matter (trash or leaves and tops) as a source of biomass. Raw sugar quality is dependent on the quality of the incoming cane supply across the processing season which, in turn, is greatly affected by the quantities and types of non-stalk tissues present. Strategies to improve the quality of raw sugar will require attention to seasonal cane quality factors as well as process manipulations. This study was undertaken to ascertain seasonal cane supply variations in juice quality parameters that affect raw sugar manufacture across the Louisiana (LA) 3-month processing season (late Sept to Dec) in 2009 and 2010. Across both seasons, maximum daily air temperature decreased with little difference in the average values (av. 23.3℃), but there was consistently higher daily rainfall in 2009 (av. 13.7 mm) than 2010 (av. 1.8 mm). Juice was extracted from separated stalk (S), growing point region (GPR or top), green leaf (GL) and brown leaf (BL) tissues of three commercial sugarcane varieties: HoCP 96-540, L 99-226, and L 99-233, at least five times between Sept and Dec. For all three varieties across harvest dates, the average total trash value (GPR + GL + BL) was 20.6% on wet weight. The most popular LA variety HoCP 96-540, still had relatively high levels of total trash until late Nov. There was a significant (P<.05) harvest date by varietal interaction for theoretical recovery of sugar in stalk. The maturity characteristic of the variety played a critical role in seasonal variation of quality parameters, especially starch. Compared to early and mid-maturing varieties, L99-226 and HoCP 96-540, respectively, which mostly delivered starch to the factories in green leaves, the later maturing variety L99-233 delivered starch mostly in the stalk after mid Oct. Thus blowing off extraneous matter in the field or at the factory for L99-233 would help little to control starch levels after mid Oct. The greatest (P<.05) variation in harvest date effect on starch concentration was in the stalk, and there was also a very strong varietal effect on starch. In contrast, the least varietal variation in juice quality parameters occurred in the GPR. Fiber did not vary considerably across the season for all varieties. Overall, for all parameters studied the type of tissue had the strongest effect, followed by variety, then date of harvest; the varietal effect was greatest in the stalk than other tissues. This suggests that breeding programs could include quality parameters as selection criteria.