Changes associated with post-harvest ageing in almond seeds

Four different varieties of almond seeds (Prunus dulcis (Mill.) D. A. Webb, syn. P. amygdalus Batsch, and P, communis (L.)) aged over two years in the dark at room temperature were analysed for changes in total lipid content, fatty acid profiles, soluble protein concentration, lipoxygenase activity, malondialdehyde and hydroperoxide production, and alpha -tocopherol content. Twenty-four months storage resulted in degradative changes in almond taste. Ageing induced accumulation of hydroperoxides and malondialdehyde, suggesting that seed deterioration was associated with lipid peroxidation. In aged seeds the lipid content dropped; the levels of linoleic and alpha -linolenic acids in total and polar lipid fraction also decreased. Lipoxygenase activity and protein content remained more or less unchanged; conversely antioxidant alpha -tocopherol which was constitutively at high concentration (25-84 mg/100 g of dry weight (d.w.)) in all four varieties showed a marked decline after ageing. A possible relationship between alpha -tocopherol and lipid peroxidation is discussed. (C) 2000 Academic Press.