Drying Seeds High in Polyunsaturated Fatty Acids Can Lead to Erroneous Results When Drying to Constant Weight.

Drying Seeds High in Polyunsaturated Fatty Acids Can Lead to Erroneous Results When Drying to Constant Weight

Maythem AL-Amery, Shreya Patel, Murong Ma, Mauricio Sanches, Tim Phillips, Paul Armstrong and David Hildebrand

Univ. of Kentucky

Abstract

Oilseeds are important sources of oils high in polyunsaturated fatty acids that are useful for edible and industrial purposes. For health and nutrition there is particular interest in oils high in ω-3 fatty acids. It is useful to determine the moisture content of oil sources for total material analysis and to calculate levels of oil, specific fatty acids. A standard method for determining moisture content and dry weight is to place samples at temperatures > 100˚C until the weights stop changing. We find with both soybean and chia (Salvia hispanica) seeds extensive lipid oxidation can occur with such drying resulting in weight increases with oxygen incorporation into lipid oxidation products and weight loss from volatile secondary lipid oxidation products along with aberrant oil measurement. This problem is greater with ground than whole seeds. Carefully following AOCS and NIST seed drying protocols can minimize such erroneous results when drying is stopped at the prescribed times. Drying in an atmosphere of nitrogen (N₂) with constant N₂ flow can eliminate lipid oxidation but results in lower final dry weights and correspondingly 1- 2% higher estimated moisture contents than drying in regular atmospheres with normal oxygen levels.

Key Words: Analysis, Biobased Products, Enzyme & Chemical Reactions, Health, Nonfood Uses, Nutrition