Comparison of the level of selected antioxidative compounds in frozen broccoli produced using traditional and modified methods

The investigation concerned frozen broccoli produced using a traditional method, i.e. from the raw material blanched before freezing, and a modified method of freezing cooked broccoli. In comparison with blanched broccoli the material cooked before freezing contained more dry matter, carotenoids and beta-carotene and less vitamin C and polyphenols; its antioxidative activity was also poorer. In frozen products stored for 0, 4, 8 and 12 months at − 20 or − 30 °C and then cooked, a steady decrease was observed in the content of all the constituents. Compared with the raw material cooked broccoli stored for 12 months contained 29–33% of vitamin C, 54–66% of polyphenols, 80–97% of carotenoids, 69–80% of beta-carotene and showed a 29–35% decrease in the antioxidative activity. A higher or similar level of the above properties was found in samples cooked before freezing as compared with blanched goods; a higher level was ascertained in samples stored at − 30 °C compared with those stored at − 20 °C. The same sensory quality was found for frozen goods obtained with both methods. Frozen products and ready-to-eat frozen products stored at − 30 °C had higher sensory quality.Industrial relevanceReady to eat vegetable products are more and more popular among individual consumers and catering services. The present work compared quality of traditional frozen broccoli and ready to eat frozen broccoli, both prepared for consumption. After long term frozen storage a higher or similar level of antioxidants was found in ready to eat type as compared with traditional type, and sensory quality of both types was at least good. Products stored at − 30 °C retained more antioxidants and revealed better sensory quality than ones stored at − 20 °C.