|Using steam treatment to enhance storage stability of grains from perennial intermediate wheatgrass|
A. MATHIOWETZ (1), C. Tyl (1), B. Ismail (1) (1) University of Minnesota, St. Paul, MN, U.S.A..
<i>Thinopyrum intermedium,</i> or intermediate wheatgrass (IWG), is a novel perennial crop with grains that have a competitive nutritional profile and advantageous environmental attributes. With strong agronomic and industrial appeal, IWG has potential to be marketed on a larger scale; however, such an effort requires more information about the grain, including its shelf life. Heat treatment has been shown to be an effective means of elongating storage life of grains by inactivating problematic enzymes responsible for hydrolytic and oxidative rancidity, namely lipase and lipoxygenase respectively. Preliminary studies indicated that these enzymes could be more problematic in IWG than in wheat. IWG and hard red wheat (HRW) control were subjected to six treatments consisting of two steam treatments (present/absent) and three incubation temperatures (4°C, 23°C, and 45°C). Antioxidant activity pre- and post-steam treatment was analyzed using 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging and leucomethylene blue (LMB) assays. Lipoxygenase activity was measured by the ferrous oxidation-xylenol orange (FOX) assay, and lipase activity was determined spectrophotometrically. Throughout storage, samples were analyzed for indicators of hydrolytic and oxidative rancidity, including free fatty acids, hydroperoxides, malondialdehydes, and hexanal. Lipoxygenase activity in IWG subjected to 60 min of steam treatment significantly decreased after two weeks of accelerated storage (<i>P</i><0.05). The antioxidant activity was not significantly affected (<i>P</i>>0.1). Also, compared to our HRW control, IWG has a higher content of ferulic acid, an active antioxidant commonly found in wheat. The interruption of enzymatic activity by steam treatment coupled with the preservation of antioxidants could help prolong the shelf life of IWG, ultimately protecting its properties and rendering it marketable.