EFFECT OF PRELIMINARY AND TECHNOLOGICAL TREATMENTS ON THE CONTENT OF CHLOROPHYLLS AND CAROTENOIDS IN KALE (BRASSICA OLERACEAL. VAR.ACEPHALA)

Abstract

ABSTRACT The level of chlorophylls and carotenoids was measured in fresh kale leaves, and in those after blanching, cooking, freezing, canning or drying. Fresh materials contained 121 mg chlorophylls, 28.1 mg carotenoids and 5.77 mg β-carotene in 100 g fresh matter. Blanching kale leaves did not significantly affect the content of these pigments, while cooking decreased only the level of chlorophylls. The highest losses of chlorophylls and carotenoids occurred in canned kale leaves and the lowest in frozen leaves. After 12-month storage, frozen products contained on average 100 mg chlorophylls and 26.3 mg carotenoids in 100 g fresh matter, while in canned products the above values were 42.1 and 22.1 mg, respectively. The content of chlorophylls and carotenoids in air dried leaves was 646 mg and 158 mg/100 g, respectively. Compared with air-dried leaves, the average levels of chlorophylls and carotenoids in freeze-dried products were 15 and 9% higher, respectively. PRACTICAL APPLICATIONS Chlorophylls and carotenoids are important components of vegetables because they give specific coloration and, as phytochemicals, show protective activity against a variety of degenerative diseases. The results of the investigation showed that of the processes preceding the actual preservation of kale, a significant loss of total chlorophylls was found only after cooking. The processes involved in the thermal preservation of kale leaves, particularly in an aquatic environment, brought about pronounced losses of chlorophyll pigments. Carotenoid pigments, however, proved more stable. Of the evaluated methods used in the preservation of kale leaves, the least loss of pigment was found after freezing and the greatest after canning. Results of this study would have practical applications in kale processing to obtain a product in which a considerable proportion of chlorophylls and carotenoids contained in raw kale leaves are retained.