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Title: OXIDATION OF SOYBEAN OIL DURING STORAGE OF STARCH-OIL COMPOSITES

Author
item GARZON, GLORIA - FORMER ARS EMPLOYEE
item Warner, Kathleen
item Felker, Frederick
item Palmquist, Debra
item Eller, Fred

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2004
Publication Date: 11/1/2004
Citation: Garzon, G.A., Warner, K.A., Felker, F.C., Palmquist, D.E., Eller, F.J. 2004. Oxidation of soybean oil during storage of starch-oil composites. Journal of the American Oil Chemists' Society. 81(9):861-866.

Interpretive Summary: Starch-oil composites are prepared by passing starch, water, and oil through an excess steam jet cooker. This new environmentally friendly, bio-based technology can be used for a wide variety of food and industrial applications. Many uses require that the cooked composite be drum dried and milled to a powdered form, which can be incorporated into other manufacturing processes or shipped more efficiently. Since the oil droplets in the dried powder are very small (1 to 10 micrometers in diameter), oxidation of the oil phase may be a problem. The purpose of this study was to determine the rate of oxidation of the oil in a drum-dried starch-oil composite. Both chemical determination of an oil oxidation product and sensory anaylysis by a trained panel were used to quantify oil oxidation. Metal contamination from the drum drier caused the first run of product to oxidize significantly faster than subsequent runs, in which the oxidation rate was much lower. These findings will be used by manufacturers of starch-oil composites to improve the shelf life of the products. Procedures developed to minimize oil oxidation will expand the range of potential applications for this technology.

Technical Abstract: Oxidative deterioration of dry starch-oil composites was investigated by chemical and sensory methods. The composites were stored at 37 degrees C for 63 days and changes in hexanal content and odor attributes were monitored. Analysis of extracted oil showed that the first run through the drum drier presented higher hexanal concentrations than the subsequent runs. Starch-oil composites from the first run though the drum drier showed higher metal concentration and higher odor ratings during storage time than the subsequent runs. There was a significant correlation between odor attributes and hexanal concentration in the first run. Since both the oxidation and the metal content was higher in the first run and decreased in further runs, we concluded that oxidation might have been induced by the presence of metal from the drum dryer. It is likely that during drum drying, metal drum and knife surfaces become coated with soy oil, reducing both abrasion and metal contact with the product. Since many applications of the starch-oil composite technology require drum drying, it will be necessary to take measures to minimize metal contamination of the product, perhaps by discarding the initial portion of product which contains the most metal.