When evaluating the effect of pretreatment and especially enzymatic hydrolysis of biomass, we normally measure the monomeric sugar produced. At most time, quite a lot of soluble oligomers existing in the hydrolyzates that could not be measured by the standard HPLC analysis, which will lead to lower hydrolysis yield. This can be confirmed by post-dilute acid hydrolysis, showing several fold increase in monomeric sugars (glucose and xylose) yield. The reason for this is that most of the commercial enzyme cocktails are not for global use and need customization for a specific biomass substrate. Some new technology ends up with strains than can work on low DP soluble sugars. Therefore, measurement of the degree of biomass solubilization after pretreatment or/and enzymatic hydrolysis will be useful information for the estimation of the treatments. A weight loss is rough, but quick method.