Influences of stir-frying and baking on flavonoid profile, antioxidant property, and hydroxymethylfurfural formation during preparation of blueberry-filled pastries

Bakery products with fruit fillings are growing fast. Blueberry-filled pastries are widely consumed in China. This study aimed to investigate the effects of two thermal processing procedures (stir-frying and baking) on flavonoid profile, antioxidant property, and hydroxymethylfurfural (HMF) formation during preparation of blueberry-filled pastries. Stir-frying contributed the most to the variations in these values in blueberry filling. Anthocyanins (48%–53% reduction in total) were more susceptible to thermal processing than flavonols (11%–16%). Among anthocyanins, delphinidin glycosides (61%–67% reduction) were the most unstable, followed by malvidin (52%–58%), petunidin (40%–45%), and cyanidin (38%–41%). A high level of HMF (300 mg/kg) was formed during stir-frying. Except for anthocyanins, baking did not significantly influence HMF formation, flavonol degradation, and antioxidant property in the fillings. Stir-frying processing conditions rather than baking must be further investigated for nutrient retention and HMF inhibition.