A comparison of the levels of oil, carotenoids, and lipolytic enzyme activities in modern lines and hybrids of grain sorghum

Authors: Moreau, Robert; Harron, Andrew; Powell, Michael; Hoyt, Jonathan

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2016
Publication Date: 2/10/2016
Publication URL: http://handle.nal.usda.gov/10113/62221
Citation: Moreau, R.A., Harron, A.F., Powell, M.J., Hoyt, J.L. 2016. A comparison of the levels of oil, carotenoids, and lipolytic enzyme activities in modern lines and hybrids of grain sorghum. Journal of the American Oil Chemists' Society. 93:569-573.

Interpretive Summary: Grain sorghum (also called milo) is an ancient grain that is similar in many ways to corn but it is receiving new interest because it can be used in gluten free food applications, requires less water and fertilizer than corn and thus can be grown more sustainably. The oil content in sorghum and corn is comparable with a range of approximately 3-4 wt%. Carotenoids are an important antioxidant found in high levels in yellow corn. In the current study the levels of carotenoids in the eighteen sorghum samples were all much lower than in the two yellow corn samples. Previously, several common grains have been reported to contain lipolytic enzymes which degrade the edible oil during storage and produce free fatty acids which are very susceptible to oxidation and cause rancidity. After two weeks of storage of milled sorghum kernel samples the levels of free fatty acids in the fourteen samples ranged from 14.37 to 55.40 wt% in oil, compared to 10.43 and 17.77 wt% in the two corn samples. This data suggests that when milled sorghum flours are stored they should either be refrigerated or frozen or stabilized by heat treatment to prolong shelf life.

Technical Abstract: Thirteen modern commercial grain sorghum hybrids and five sorghum lines were extracted and the levels of oil and carotenoids were analyzed and compared. The same samples were also evaluated for lipolytic enzyme activity. The oil content in all eighteen samples ranged from 3.21 to 4.29 wt%. Beta carotene and zeaxanthin were the predominant carotenoids and the levels of total carotenoids ranged from 3.82 to 19.5 ppm in the oil, which was much lower than the levels of total carotenoids in two yellow corn samples (70.8 and 103 ppm). Lipolytic enzyme activity was estimated by storing milled kernel samples for two weeks at 25 degrees C, extracting the oil, and measuring the levels of total free fatty acids. After two weeks the levels of free fatty acids in oil from the eighteen samples ranged from 14.37 to 55.40 wt%, compared to 10.43 and 17.77 wt% in the oil from the two corn samples. This new data will be useful for persons using grain sorghum for food, biofuels and other industrial applications.