Evaluation of techniques and suitable sample number for soluble carbohydrate extraction in stem bases of elephantgrass

Methods for extracting soluble carbohydrates were compared, aiming at optim izing sample number and size, for level determination using Teles' reagent. Oven-dried ground stem basal segments of elephantgrass (Pennisetum purpure um, Schum.) cv. Napier, carbohydrate standards (glucose, maltose, sucrose, and starch), and sample-standard combinations (CSs) were extracted through the following procedures: (a) REF: reflux for 180 min (in 0.6N HCl); (b) SH A: orbital shaking for 60 min (in 50% ethanol), followed by an acidic hydro lysis (1.2N HCl) in water bath (90-100 degrees C) for 60 min, and neutraliz ation with 5% NaOH; (c) HET: 80% ethanol overnight and water bath for 180 m in; (d) ETH: 0.6N HCl tin 80% ethanol) overnight and water bath for 180 min ; and (e) DIG: 80% ethanol overnight, addition of 1.2N HCl, and water bath for 60 min. REF yielded the highest extraction level in the elephantgrass s ample, followed by ETH and SHA. Levels with HET and DIG were the lowest. Ho wever, REF was excessively time consuming and effected starch extraction, b eing not the best choice for soluble carbohydrate evaluations. HET showed n o sucrose extraction and DIG did not perform well with the sample, both bei ng considered not applicable. ETH, although exhibiting a marked sample extr action, showed the poorest standard results, specially with glucose. SHA wa s found to be the best method, because it was the only one that effected to tal sugar (except for maltose) and no starch extraction. Results pooled for all treatments revealed non-significant paired-mean contrasts between sepa rate and combined (CSs) sample-standard associations. This indicates that t he strategy of carrying out comparisons with standards was appropriate. For the SHA method, the Student's t distribution of the means revealed that th e minimum number of samples for maintaining the highest possible precision was 5 replications. On the other hand, increasing sample number up to 9 rep lications did not improve data precision.