The effect of different roasting processes on the total phenol, flavonoid, polyphenol, fatty acid composition and mineral contents of pine nut (Pinus pinea L.) seeds

Abstract

In this study, the effects of roasting at different times in hot air and microwave oven on the bioactive properties, fatty acid compositions, mineral contents and phenolic components of pine nut kernels and oils were investigated. According to the results obtained, the moisture quantity of pine nuts generally decreased due to roasting. The lowest moisture content belongs to the sample roasted for 17 min in a microwave oven with 2.66%. Roasting processes on oil content gave positive results, and the sample that provides the highest content (48.4%) is the sample that was roasted for 7 min in hot air. Roasting processes increased the protein content in general, and the samples with the highest protein content were roasted in a microwave oven for 17 min (26.16%). When the ash content is examined, it has been determined that the oven and microwave oven roasting processes reduce the amount of ash. While the total phenol content of the kernels increased inversely with the roasting times, the total phenol content of the oils increased unevenly depending on the roasting times compared to the control sample. Gallic acid is the most frequently detected phenolic component in pine nut kernels and oils. The highest flavonoid content in the kernels was measured with 9 min roasting (12.81 mgqE /100 g) in the microwave oven, while roasting for 7 min in the oven gave the lowest value (7.86 mgqE /100 g). On the other hand, the highest value in oils with 20.6 mgqE /100 g belongs to the samples roasted in an oven for 7 min. In general, the antioxidant activity value of pine nut kernels roasted in an oven and microwave oven showed a partial increase compared to the control. The antioxidant activity values of the oils gave similar results and it was seen that the results were not affected by the roasting times. The most frequently detected minerals in pine nut samples were N, P, K, Mg, S, Ca, Fe, Zn, Mn, Cu and B, in decreasing order. The most abundant fatty acids in pine nut oils were linoleic and oleic acids, and roasting had a slight negative effect on the fatty acid composition.