Measurement of fatty acids in whole soybeans with near infrared spectroscopy

Abstract

Improvement of nutritional and/or functional properties of soybean oil by modification of soy fatty acid composition is one of the objectives of plant breeders. A major element of breeding is rapid identification and tracking of traits in seed samples. This discussion summarizes the progression of whole‐soybean fatty acid calibration developments at Iowa State University. Emphasis was placed on linolenic acid (18:3) and total saturates (16:0 + 18:0). Normal soybeans have 12–20% (of the oil) saturated fats; modified low saturate soybeans have 6–8% saturated fats. Normal soybeans have 6–12% linolenic acid; modified low linolenic soybeans have 1–3% linolenic acid. Infratec 122x/1241 and Bruins OmegaG NIRS units were calibrated to measure fatty acid levels as a percentage of total oil content, in whole soybeans. The first Infratec calibrations (in 1998) did not remain accurate as soybean genetics changed. Iterations of the calibration process yielded calibrations for total saturates and linolenic acid with standard errors of prediction (on 2005 crop samples not included in the calibration pool) of 1.0% percentage points and 0.8% points, respectively. These were sufficient to classify modified versus normal concentrations of the two fatty acids. The NIRS units could not determine the specific percentages within the classes of modified and normal soybeans.