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Title: Effect of extrusion cooking of lesquerella seeds on the quality of the extracted oil

item Evangelista, Roque

Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Abstract Only
Publication Acceptance Date: 10/10/2007
Publication Date: 10/10/2007
Citation: Evangelista, R.L. 2007. Effect of extrusion cooking of lesquerella seeds on the quality of the extracted oil [abstract]. Association for the Advancement of Industrial Crops. p. 47.

Interpretive Summary:

Technical Abstract: Lesquerella fendleri is an oilseed crop belonging to the Brassicaceae family that is native to the desert southwestern United States. The seed has 28% oil, which contains about 64% hydroxy fatty acid (HFA). HFA is used in a variety of industrial applications such as lubricants, corrosion inhibitors, engineering plastics, plasticizers, emulsifiers, and coatings. Production of Lesquerella is currently being scaled-up for commercialization. The seeds also contain glucosinolates that, upon hydrolysis by thioglucosidase (TGSase), produce undesirable sulfur-containing compounds in the meal and may end up in the oil during extraction. Inactivation of TGSase is an important step in preparing seeds for oil extraction. This study investigated the use of extrusion cooking in inactivating TGSase and its effect on the quality of the crude oil. Whole Lesquerella seeds with 6% (as is) and 11% moisture were extruded at 270 and 470 rpm screw speeds. The temperature of the extrudate was recorded and its moisture content was determined. The extent of seed cooking was evaluated by measuring the protein solubility and TGSase activity in the extrudate. Uncooked and extrusion-cooked seeds were screw pressed and the crude oils obtained were analyzed for solids, free fatty acid, sulfur, and phospholipid contents and color. Running the extruder at 270 and 490 rpm provided residence times of 110 and 80 sec, respectively. The exit temperature of the extrudate ranged from 255 deg F to 289 deg F, with the latter obtained from 6% MC seed extruded at 490 rpm. Seeds with 6% initial MC dried down to 2.3%, while seeds with 11% initial MC came out at 7% MC. The protein solubility decreased by 55% and 70% for seeds with 6% and 12% initial MC, respectively, when extruded at 270 rpm. All extruded seeds tested negative for TGSase activity. Extruded seeds with 6% initial MC resulted in much higher solids (6.4-9.4%) in the oil compared with that of the 11% MC seeds (1-1.7%). Free fatty acid content increased with increasing moisture, but was not affected by cooking. After cooking, sulfur content significantly increased from 9-33 ppm to 102-112 ppm. Cooking also increased the phosphorus content (a measure of total phospholipids) from 3 ppm to 16 ppm. This higher phosphorus content is still less than the values for good water-degummed oils (60-200 ppm), indicating that degumming may be unnecessary. Crude oil from extruded seeds was darker (13-14 Gardner) than the oil from uncooked seeds.