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Einfluß von Reifedauer, Temperatur und Sauerstoffversorgung auf die Bildung von ungesättigten Fettsäuren und Tocopherolen in Sonnenblumenfrüchten
Author(s) -
Dompert W. U.,
Beringer H.
Publication year - 1976
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19761390204
Subject(s) - polyunsaturated fatty acid , linoleic acid , tocopherol , sunflower oil , sunflower , chemistry , ripening , food science , horticulture , fatty acid , vitamin e , botany , antioxidant , biology , biochemistry
Influence of ripening, temperature and oxygen supply on the synthesis of unsaturated fatty acids and tocopherols in sunflower seeds The ratio of vitamin E (tocopherol)/polyunsaturated fatty acids (T/PUFA) is of importance in the storage and consumption of oils and diets. In previous experiments low temperature and cool climate during seed development of sunflowers were found to decrease the T/PUFA in the seeds ( Beringer and Saxena , 1968; Dompert et al., 1975). This may be due to a) a prolonged „filling period” at low temperatures and/or b) a direct effect of temperature on the synthesis of oil and tocopherol in the seeds. Harvesting sunflower seeds, grown in a climate‐chamber at 22°C, at 1, 8, 15, 25, 31 and 40 days after pollination revealed an intensive lipid synthesis in the seeds between 8 and 31 days after pollination, thereafter a small decline of total lipids occured. Total tocopherols, with α‐tocopherol dominating, were synthesized nearly parallel to total lipids. Accordingly a ratio of 1 mg tocopherol/g seed‐oil and approximately 3–4 mg tocopherol/g linoleic acid respectively from 8 days after pollination till maturity was found. Increased growth temperatures (day and night same) from 10 to 22 up to 35°C from flowering till maturity caused a decrease in oil content and linoleic acid percentages. An attempt to compensate the stimulating effect of low temperatures on fatty acid desaturases by flushing sunflower‐heads with gas mixtures of 21% O 2 (10°C plants), of 28% O 2 (22°C plants) and 38% O 2 (35°C plants) according to Harris and James (1969) resulted in only slight increases of linoleic acid, which were with 23,5% at 35°C and 40,7% at 22°C still much lower than at 10°C, where linoleic acid was linoleic acid was 62,8% of total fatty acids. Under natural conditions a direct influence of growth temperature seems therefore more likely in determining the fatty acid composition than temperature dependant rates of O 2 ‐diffusion into the seed tissue. Unlike fatty acid synthesis the synthesis of tocopherols was not significantly influenced by the growth temperature. But due to decreasing oil content and linoleic acid percentages at higher temperatures the α‐Tocopherol/g oil as well as the α‐tocopherol/g linoleic acid was continuously raised. The latter increased from 0,9 at 10°C up to 7,8 at 35°C i. e., the ratio of 1 I. U. vitamin E/g PUFA required in animal and human nutrition was achieved at all temperatures tested. The parallelism of oil‐ and tocopherol‐content in developing sunflower seeds on the one side and the large, temperature dependant variability of the T/PUFA‐ratio on the other side suggest, that no „stoichiometric” relation exists between the synthesis of tocopherols and fatty acids in sunflower seeds. Fatty acid desaturases in oil seeds are membrane‐bound enzymes and tocopherol might be involved as an antioxydative stabilizer of the membrane as it is known from animal tissues ( McCay et al., 1971).