Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 4/7/2014
Publication Date: N/A
Interpretive Summary: The peanut industry has the need to keep lots of high-and normal-oleic peanuts separated. Due to the fact that peanuts on the plants are maturing at different times even at harvest dates, mixed lots are found. Peanut plants of normal- and high-oleic varieties were planted in North Carolina and whole plants were sampled early, mid season and at the end of the growing season. All the pods were removed from the plants and the seeds were tested for their fatty acid profiles, moisture and total fat contents. At the final harvest, a lot of 35 kg from each variety was sorted according to maturity using the hull scrape method. Normal oleic seeds showed slightly increased ratios of oleic to linoleic acid but no values above 3. High oleic seeds had a range of ratios throughout the growth periods. Early samples were all in the normal oleic range. Closer to maturity, seeds about the high oleic determination threshold (9) were found, but even at harvest up to 35% of the high oleic seeds were still immature and tested to be normal-oleic. This study indicates that unless immature seeds can be removed regardless of size from high-oleic peanut lots, lots will be mixed normal- and high-oleic.
Technical Abstract: Oleic (O) and Linoleic (L) are the main fatty acids in peanut oil. Peanuts with an O to L ratio (O/L) above 9 are defined as High-oleic (HO). Processors prefer HO peanuts to Normal Oleic (NO) due to increased storage stability. Various sources of mixing of NO and HO seeds exist in the peanut supply chain resulting in impure lots. Determination of mixing due to fatty acid development during maturation of NO and HO seeds was the basis of this study. Fresh, uncured seeds were sampled at early, mid, and late maturity stages (120, 134, and 148 days after planting (DAP)). 5 plants each of NO and HO virginia type peanuts were sampled at each time point and the O/L of each seed from each plant was determined. At 120 DAP, O/L for NO was found to be 0.72 ± 0.15 and 2.0 ± 0.76 for HO. O/L was 1.6 ± 1.02 for NO and 9.1 ±8 .80 for HO at 134 DAP. At 148 DAP, O/L for NO was found to be 1.5 ± 0.59 but O/L for HO was found to range from 0.2 to 60.9 showing at harvest 50.76 % of the HO seeds were below 9. At harvest, a bulk lot of 35 kg from both varieties was sorted into maturity classes and 39.1 % of the NO and 35.0 % of HO were found to be immature. O/L ratios of the individual seeds in each maturity class were determined and immature seeds and found to be below 9 for HO seeds, but did not vary from 1.5 ± 0.89 in NO. Based on these findings, verification of maturity especially of HO lots will reduce mixed lots.