The investigation covered broccoli, green cauliflower and Brussels sprouts. The evaluation concerned the raw material; the material after blanching; the material after cooking; and frozen products from blanched (traditional method) and cooked (modified method) material, stored at –20°C and –30°C then prepared for consumption using water-cooking in the traditional method and thawing by microwave in the modified method after 0, 4, 8 and 12 months of frozen storage. Depending on the investigated sample, the vegetables prepared for consumption after 12 months of frozen storage retained total chlorophylls as follows: broccoli, 45-66% of the content in the raw material; green cauliflower, 30-45%; and Brussels sprouts, 66-78%. In comparison with the traditional method, the mean content of chlorophylls in Brussels sprouts obtained using the modified method was 16% higher; however, in broccoli the content was lower by 23% and in cauliflower by 21% on average. Lower storage temperature resulted in higher content of chlorophylls in all investigated vegetables.

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