ARS | Publication request: Pressurized solvent extraction of pure food grade starch

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 7, 2011
Publication Date: March 20, 2012
Citation: Eller, F.J., Peterson, S.C., Sessa, D.J. 2012. Pressurized solvent extraction of pure food grade starch. Carbohydrate Polymers. 87(4):2477-2481.

Interpretive Summary: Cornstarch is commonly used as a thickening agent in the food industry. Minor components present with the starch can have a very large effect on the thickening properties of the cornstarch. This research investigated the use of a commercial pressurized solvent extractor was for separating both fatty and non-fatty materials from cornstarch using mixtures of water with two different alcohols (n-propanol and ethanol). The effects of the two solvents on the extraction yields and the chemical composition of the extracts fractions were determined. In addition, the physical properties of the cornstarch both before and after extraction were also studied. The n-propanol/water mixture extracted slightly higher amounts of both fatty and non-fatty materials than did the ethanol/water mix. The lipid fractions from both solvents were found to contain mostly free fatty acids. The non-lipid fraction was found to contain mostly protein in the form of zein. The cornstarch extracted with either the n-propanol/water mixture or the ethanol/water mix had lower viscosities than did the unextracted starch. The samples extracted with the n-propanol/water, regardless of whether it was used first, last or alone, all had lower shear storage modulus values than did the unextracted starch. On the other hand, the samples extracted with ethanol/water had shear storage modulus values higher than the unextracted starch. It is hypothesized that even the very low amounts of zein remaining on the starch granules is responsible for this observed effect. This study found the use of a commercial pressurized solvent extractor a convenient method to remove both fatty and non-fatty materials such as free fatty acids and zein from cornstarch. The unique gelling properties of the extracted cornstarch may have useful physical properties and food processors may be able to generate new products because of these novel properties.

Technical Abstract: A commercial pressurized solvent extractor was used to remove lipid and non-lipid material from cornstarch using n-propanol/water and ethanol/water mixtures. Yields and chemical composition of the extract fractions were determined. Cornstarch samples were characterized using pasting properties and shear storage modulus measurements. The n-propanol/water extracted slightly higher amounts of both lipids and non-lipids. The lipid fractions contained mostly linoleic, palmitic and oleic free fatty acids. The non-lipid fraction contained mostly protein in the form of zein. The extracted starch had lower peak and setback viscosities than did the unextracted starch. The starch extracted with n-propanol/water had the lowest shear storage modulus values. Conversely, the samples extracted with ethanol/water had the highest shear storage modulus values. It is hypothesized that low amounts of zein on the starch is responsible for this observed effect. Both lipid and non-lipid materials can be conveniently removed from cornstarch using a commercial pressurized solvent extractor.