Using NIR to Predict Palmitic Fatty Acid in Peanut Seeds.

Fatty acid composition of peanut oil is an important consideration in peanut breeding.  The University of Florida peanut breeding program uses Near Infrared Reflectance Spectroscopy (NIR) to predict oleic and linoleic fatty acid composition of intact peanut seeds.  Compared to gas chromatography NIR prediction of fatty acid in peanut is quicker is nondestructive.  Oleic, linoleic and palmitic acids make up about 90% of peanut oil, so prediction of palmitic acid would be useful.  This research was conducted to develop an NIR prediction of palmitic acid in peanut seeds.  To verify the relationship among fatty acids, correlations between eight fatty acids in peanut (oleic, palmitic, stearic, linoleic, arachidic, eicosenoic, behenic, and lignoceric) were determined from 13,947 samples analyzed from 1995 through 2007.   Oleic acid was negatively correlated with palmitic acid (-0.92,P>r<0.0001), and linoleic acid (-0.99,P>r<0.0001).   Correlations with between oleic and stearic, arachidic, eicosenoic, behenic and lignoceric were statistically significant (<0.0001) even though the correlation coefficients was as low as -0.04 for lignoceric and as high as 0.33 for eicosenoic.  This indicates that the change in these fatty acids in response to oleic acid was minor or that statistical significance was spurious due to the large number of samples involved.  An NIR calibration equation for palmitic acid was developed using 243 individual seeds.  The calibration equation predicted palmitic acid with an R-squared of 0.724 and a slope of 0.793.   Five individual seeds from each of 19 cultivars were used to externally validate the calibration equation.  The NIR system predicted palmitic acid from the external validation set with an R-squared of 0.799 and a slope of 0.76.   The NIR calibration for palmitic acid provides a new tool for predicting palmitic acid from single, intact peanut seeds making it possible to rapidly evaluate breeding material for oleic, linoleic and palmitic fatty acids.