Influence of storage conditions on antioxidants content of einkorn and bread wheat flours

The kinetics of tocols and carotenoids degradation in wholemeal and white flours of einkorn Monlis and bread wheat Serio, stored at -20, 5, 20, 30 and 38 °C, was assessed by NP-HPLC. Both antioxidants decreased as a function of time and temperature, following a first order kinetics. Carotenoids degradation rates were similar in wholemeal and white flour, but loss of lutein and total carotenoids was faster in Serio than in Monlis, possibly because their concentration in bread wheat was eight-fold lower than in einkorn (1.0 and 1.1 vs. 8.1 and 9.8 mg/kg DM). The activation energy (Ea) of degradation reaction ranged from 35.2 to 52.5 kJ/mol. Tocols degradation rates and their dependence from temperature were similar for the two Triticum species studied. The decrease was quicker in white flour than in wholemeal flour (for total tocols at 38 °C k = 7.79 x 10-3 vs. 3.15 x 10 3 days-1, respectively). Temperature-dependent degradation was similar for all homologues (Ea = 34.3 – 49.4 kJ/mol) except for -tocopherol, less thermostable in white flours. The results indicate that storing flours at temperatures not exceeding 20 °C better preserve carotenoids and tocols content.