Hydrolytic Methods for the Quantification of Fruct

Authors: Stefanie K Nguyen Supaporn Sophonputtanaphoca Eugene Kim Michael H Penner

Publish Date: 2009/03/31

Volume: 158, Issue: 2, Pages: 352-361

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Abstract

A low but significant fraction of the carbohydrate portion of herbaceous biomass may be composed of fructose/fructosylcontaining components “fructose equivalents” such carbohydrates include sucrose fructooligosaccharides and fructans Standard methods used for the quantification of structuralcarbohydratederived neutral monosaccharide equivalents in biomass are not particularly well suited for the quantification of fructose equivalents due to the inherent instability of fructose in conditions commonly used for hemicellulose/cellulose hydrolysis 80 degradation of fructose standards treated at 4 sulfuric acid 121°C 1 h Alternative time temperature and acid concentration combinations for fructan hydrolysis were considered using model fructans inulin β21 and levan β26 and a grass seed straw tall fescue Festuca arundinacea as representative feedstocks The instability of fructose relative to glucose and xylose at higher acid/temperature combinations is demonstrated all rates of fructose degradation being acid and temperature dependent Fructans are shown to be completely hydrolyzed at acid concentrations well below that used for the structural carbohydrates as low as 02 at 121°C for 1 h Lower temperatures are also shown to be effective with corresponding adjustments in acid concentration and time Thus fructans can be effectively hydrolyzed under conditions where fructose degradation is maintained below 10 Hydrolysis of the β21 fructans at temperatures ≥50°C at all conditions consistent with complete hydrolysis appears to generate difructose dianhydrides These same compounds were not detected upon hydrolysis of levan sucrose or straw components It is suggested that fructan hydrolysis conditions be chosen such that hydrolysis goes to completion fructose degradation is minimized and difructose dianhydride production is accounted for

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