Effects of Maturity on the Development of Oleic Acid and Linoleic Acid in the Four Peanut Market Types

The commercialization of high oleic peanut varieties with the fatty acids, oleic and linoleic present in a ratio greater than 9 has increased the shelf stability of many products containing peanuts significantly. With no visual traits to determine levels of the fatty acids present, mixing of the high oleic peanut types from the normal oleic types has been a problem in the peanut supply chain. This study investigated the effect of the development of the fatty acids in peanuts over their maturation with respect to the different market types (Runner, Viriginia, Spanish, Valencia) to determine if the maturation stage of the peanut could be responsible for the presence of normal oleic peanuts in lots of high oleic peanuts and thus decreasing the purity of the lots. Peanuts had different levels of the main fatty acids present as the oil content increased with maturation. Due to the presence of a natural desaturase enzyme in peanuts, oleic acid is converted to linoleic as the peanut develops resulting in a ratio of oleic acid to linoleic acid of 3 or lower in normal oleic peanuts. In peanuts from high oleic cultivars, the genes encoding for this enzyme are mutated or slow to develop. As this gene is activated in the later stages of peanut maturity, this study proves immature peanuts of the high oleic type may not have the proper ratios of oleic to linoleic to ensure shelf stability despite being from high oleic cultivars. This study describes how the concentrations of oleic and linoleic acid changed with maturation of the peanut seeds and affects the purity of individual lots of high and normal oleic types of peanuts. This effect of maturity was seen to be greater in the large seeded Virginia cultivars compared to the smaller seeded market types.