Submitted to: Colloids and Surfaces A: Physicochemical and Engineering Aspects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 27, 2006
Publication Date: January 1, 2007
Citation: Shogren, R.L., Biresaw, G. 2007. Surface properties of water soluble starch, starch acetates and starch acetates/alkenylsuccinates. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 298(3):170-176. Interpretive Summary: Finding new, high value uses for corn starch will depend on a better understanding of the physical behavior of starch. Specifically, the surface tension of starch in water or its tendency to spread over other surfaces is critical to applications as coatings, adhesives and dispersing agents. However, previous studies of the surface properties of starch and chemically modified starches have been conflicting and incomplete. This work has used a newer technique to determine values for the surface tension of starch and modified starches which are probably much closer to the correct values than previous studies. In addition, one of the modified starches acted as a good emulsifier for soybean oil. This work should help scientists and engineers in the food and industrial sectors predict how to improve the effectiveness of starch coatings, adhesives and dispersants.
Technical Abstract: Surface and interfacial tensions with hexadecane were measured for starch and water soluble starch ester solutions in order to determine their potential as stabilizers or emulsifiers. The surface tension for an acid hydrolysed starch (maltodextrin) initially declined with concentration and then reached an equilibrium value of 56 dyn/cm at 20-40 wt. %, suggesting that hydrated starch has this surface energy. Surface and interfacial tensions of starch acetates decreased more rapidly with concentration reaching values of 41-44 and 11-13 dyn/cm, respectively at 40 wt. %. There was little dependence of surface or interfacial tensions on DS between 0.3-0.8 and amylose content of starch acetates. Surface and interfacial tensions for starch acetate/alkenysuccinates were lower than those for starch acetates, particularly at low concentrations. Soybean oil/water mixtures were emulsified for more than 1 day by waxy starch acetate/OSA and acetate/DDSA but not starch acetates. In summary, these starch esters may represent biodegradable, economical alternatives to some emulsifiers and coating polymers currently in use.