The invention comprises 6-(O-alkenoyl) derivatives of ascorbic acid wherein the alkenoyl group is derived from an olefinically unsaturated fatty acid containing 8 to 20 carbon atoms. The compounds are obtained by esterifying ascorbic acid with the unsaturated fatty acid in the presence of boron trifluoride. In examples, esters are prepared from ascorbic acid and isoascorbic acid with oleic acid. Other fatty acids mentioned are elaidic acid, linoleic acid, linolenic acid and arachidonic acid.ALSO:Fats and vegetable oils are stabilized by adding an ester of ascorbic acid with an unsaturated fatty acid containing 8 to 20 carbon atoms. The ester may be mixed with an edible carrier e.g. a partial glyceride, and added to the fat or vegetable oil. In an example 6-(O-oleoyl)-ascorbic acid is mixed with L-proline, gamma tocopherol and glycerine monooleate and added to sunflower oil and lard.ALSO:Foodstuffs and animal feeds are stabilized by adding an ester of ascorbic acid with an unsaturated fatty acid containing 8 to 20 carbon atoms. An example of the ester is 6-(0-oleoyl)-ascorbic acid. Foodstuffs mentioned are milk, sausages, salad cream and potato powder.