Contents of chlorophylls and carotenoids in frozen dill: effect of usable part and pre-treatment on the content of chlorophylls and carotenoids in frozen dill (Anethum graveolens L.), depending on the time and temperature of storage

The aim of the work was to compare the contents of chlorophylls, total carotenoids, and beta-carotene in the leafy part and in whole plants (leaves with petioles and stems) of dill harvested at the 25 cm stage of growth. Changes in the levels of these compounds in the technological process of freezing and refrigerated storage were also determined. The investigation concerned two kinds of raw material (leafy parts and whole plants), different treatments before freezing (blanching or non-blanching of the raw material), differentiated temperature of storing frozen products (−20 °C and −30 °C), and a storage time of 12 months. Analyses of the frozen products were conducted every 3 months. In 100 g fresh matter of dill leaves the content of dry matter was 12.89 g and of chlorophylls was 144 mg with a ratio of chlorophyll a to b of 1:0.33, that of carotenoids, 30.3 mg and of beta-carotene, 5.00 mg. In whole plants, the contents of comparable components were 26, 40, 38, and 41% smaller, respectively, the ratio of chlorophyll a to b being slightly lower (1:0.39). Blanching, freezing, and in storage of refrigerated products, irrespective of temperature, did not change the contents of components analysed in the first 3 months. During the successive months of storage, blanching favourably affected the preservation of total carotenoids and beta-carotene while the lower temperatures of storage had a beneficial effect on chlorophyll content. The components analysed were preserved in leaves to only a slightly higher extent than in whole plants. If good (90%) preservation of chlorophylls, carotenoids, and beta-carotene were to be used as a criterion of valuation, the dill could be stored for up to 6 months at −20 °C without blanching. For storage periods above 6 months, blanching is necessary, the preservation of analysed components being better at a lower temperature of storing.