Assessment of the main sources of variability of soybean (Glycine max) expeller composition and quality: a field study

Abstract

Pairs of soybean seeds and their correspondent expeller samples were collected from ten extrusion-expelling processing plants in Argentina. Seeds were analyzed for proximal composition, bulk moisture content (MC) and individual seed MC. Soybean expeller (SBE) samples were e analyzed for proximal composition, bulk MC, protein solubility in KOH, expeller urease activity and free fatty acid content. Results indicated that average soybean composition was 136 g kg-1 MC, 207 g kg-1 oil and 391 g kg-1 crude protein (CP), while the oil extraction efficiency (OEE) of the process was 60.7%. The expeller composition was 928 g kg-1 dry matter (DM), 81 g kg-1 oil and 442 g kg-1 CP. In soybean seeds, coefficient of variation (CV) of MC was 17.2%, 3.0% for CP and 5.1% for oil, while in SBE, CV for DM was 2.9%, 3.9% for CP and 19.7% for oil. A relationship among soybean seed MC, OEE and expeller composition was found. The findings indicate that conditioning the soybean MC prior to processing is important not only to maximize OEE, but also to achieve uniform expeller composition and to assure deactivation of anti-nutritional factors