Abstract
The objective of this study is to compare the influence of genotype, environmental conditions and processing methods after maturation and harvesting of four varieties of flaxseed (Altess, Biltstar, Niagara and Oliwin) on the levels of tocochromanols, carotenoids and chlorophyll in flaxseed oil. Samples were produced by cold pressing of dry seeds and seeds heated for 30 min at 60 °C. Temperature, sunshine and rainfall were primary environmental conditions included. Grand mean of mass fraction of γ-tocopherol was (522±29), of plastochromanol-8 (305±2) and total tocochromanols (831±3) mg per kg of oil. The highest levels of these compounds and strongest antioxidant activity were found in cold- -pressed oil of Biltstar variety. During seed maturation, levels of γ-tocopherol and plastochromanol-8 increased with average temperature and total sunshine and decreased with total rainfall. Fifth week after flowering was identified as the maturation period with best climate conditions to achieve optimal tocochromanol content. Grand mean of mass fraction of carotenoids expressed as β-carotene was (1.83±0.01) and of chlorophyll expressed as pheophytin a (0.43±0.10) mg per kg of oil. Altess variety had the highest levels of pigments. Antioxidant activity decreased with the increase of chlorophyll, while correlations with carotenoids were not determined. Generally, oil obtained by cold pressing had higher levels of tocochromanols and lower levels of pigments but similar antioxidant activity to the oil after seed conditioning. The results of this study contribute to identifying the flaxseed variety that is the best for oil production with the highest antioxidant activity and nutritive value, and provide better understanding of tocochromanol biosynthesis depending on different climate conditions.
Highlights
Flaxseed oil contains more than 50 % of α-linolenic acid and more than 13 % of linoleic acid, which makes it very susceptible to oxidation and taste deterioration [1]
The results showed flaxseed oil as a rich source of natural vitamin E that changes significantly with different climate conditions during maturation, variety and type of oil production (Table 1)
To provide better understanding of the influence of climate on the studied bioactive compounds, we calculated climate index based on Principal component analysis (PCA) analysis with combining all annual values of temperature, sunshine and rainfall for maturation period of flaxseed starting from the moment of flowering until harvesting
Summary
Flaxseed oil contains more than 50 % of α-linolenic acid and more than 13 % of linoleic acid, which makes it very susceptible to oxidation and taste deterioration [1]. As reported in other studies, quantities of tocopherols in flaxseed oil significantly differ from 154 to 934 mg/kg of oil with the main representative γ-tocopherol [1,2]. Such big variations could be a result of different harvesting locations and varieties, extraction technologies or storage time of packed flaxseed oil. Other important antioxidants in flaxseed are carotenoids, which are members of a larger group of plant pigments with 750 different structures [8] They function as hormone precursors, colourants and essential elements in photosynthetic cycle [8]. Both carotenoids and tocochromanols are synthesized partially or entirely as plastidic isoprenoids during biosynthetic pathway [8]
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