Functional and microstructural aspects of soluble corn starch in pastes and gels

Soluble starch plays an important role in the rheology of starch pastes and gels. However, some functional aspects and the microstructural basis of it s contribution are still not clear. In this study, commercial corn starch w as pasted in a Rapid Visco Analyzer to peak viscosity, and separated into s oluble starch (clear of granules and primarily amylose) and insoluble starc h (gelatinized starch granules and primarily amylopectin). When the insolub le starch was reconstituted at different levels with soluble starch, paste viscosity profiles in the Rapid Visco Amylgram decreased with addition of i ncreasing amounts of soluble starch. Cold stage scanning electron microscop y (SEM) of pastes revealed a continuous cellular structure of the, sample w ithout soluble starch and a denser fibrous structure of the one with solubl e starch. Texture analysis of gels formed from pastes showed that the firmn ess of the gel increased, while gel stickiness decreased. with increasing a mounts of added soluble starch. Curd stage SEM of gels revealed a fibrous s tructure of the gels with the addition of soluble starch and a cellular str ucture of the gels consisting of insoluble starch alone. Decrease in gel st ickiness with addition of the amylose-rich soluble portion implies a large contribution by amylopectin or starch remnants to sticky gel texture. The m icrostructural comparison or pastes and gels with and without soluble starc h provides a structural explanation for the function of soluble starch in p astes and gels.