Liquefaction concentration impacts the fine structure of maltodextrin

Abstract

Designing a high-concentration (45%, w/w) corn starch liquefaction process is a challenge, as more than just the rate of enzymatic hydrolysis must be considered. Maltodextrins with the same dextrose equivalent value were produced in an industrial liquefaction process using normal corn starch suspensions at low (10%, w/w), normal (30%), and high (45%) concentration. The starch concentration noticeably influenced the fine structure of the starch hydrolysate. Increasing the starch concentration from 10% to 45% limited the cleavage of long chains and enhanced the generation of linear maltooligosaccharides and the survival of large molecules. These effects contributed to a bimodal molecular size distribution and high iodine binding by the product maltodextrin. We propose that high starch concentration may induce a higher level of multiple enzyme attack, in which α-amylase attack of external chains is enhanced. As a result of its structural heterogeneity, maltodextrin derived from 45% starch exhibited higher viscosity and was a poorer substrate for amyloglucosidase. This led to lower saccharification efficiency even though this maltodextrin was diluted to conventional concentration (30%, w/w). Thus, further work is needed to produce maltodextrins suitable for saccharification through the liquefaction of corn starch at high concentration.