Flaxseed oil - baking/storage, Flax Council of Canada
Baking effects:
ALA in whole and milled flaxseed also appears to be stable to heat equal or greater than the temperatures involved in baking batters and doughs such as muffins and yeast bread. Thermal stability was shown in 1992 by the absence of significant changes in peroxide values and fatty acid composition when both forms of flaxseed were heated for 60 minutes at either 100°C (212°F) or 350°C (662°F).
Furthermore, gas liquid chromatography showed no signs of new trans isomers of ALA or of cyclic fatty acid formation in samples subjected to these degrees of heat5. In a follow-up study the proportion of ALA in the fat of a muffin mix, where 28.5% of the formula was milled flaxseed, was virtually unchanged after baking at 178°C (350°F) for 2h (45.1% ALA before:45.0% after). This stability was observed even though oxygen consumption of the flaxseed muffin mix was considerably greater than that of the control muffin mix6. A subsequent study confirmed the stability of ALA in baked muffins containing the same amount of milled flaxseed and noted that thiobarbituric acid values, as estimates of ALA oxidation were also unaffected by baking9.
On reflection, the baking stability of ALA should not be surprising considering that the internal temperature of a muffin approaching doneness would not be expected to exceed the gelatinization temperature of starch. Wheat flour in the presence of sugar, or honey in this instance, would gelatinize around 95°C (203°F), much lower than the temperature of hot air in the oven from which heat is transferred to the baking product. A further margin of safety for the ALA-conscious consumer is the fact that muffins are usually baked for only 20-25 min. at 204-208°C (400-425°F) in contrast to some experimental conditions4.
Biological evidence also supports the stability of ALA to baking temperatures. Nine college women included 50g flaxseed in their daily diet for four weeks in one of two ways. Five of them added milled flaxseed, uncooked, to the food of their choice such as breakfast cereal, soup, juice or yogurt. The other four consumed bread baked with milled flaxseed (250g/kg) rather than their usual bread. Plasma fatty acid profiles during the four-week study were not significantly different between the women eating raw milled flaxseed and those eating the same amount of flaxseed baked in bread. Both subject groups exhibited a lowering of serum total cholesterol and low-density-lipoprotein cholesterol10. The implication is that baking had no effect on the bioavailability of flaxseed fatty acids.
