Emulsifying and Anti-Oxidative Properties of Proteins Extracted from Industrially Cold-Pressed Rapeseed Press-Cake.

One of the functional proteins in rapeseed-the amphiphilic protein oleosin-could be used to stabilize emulsions. The objectives of this study were to extract oleosins from cold-pressed rapeseed press-cake, optimize the extraction process, and investigate their emulsifying and anti-oxidative capacity. The proteins were recovered from industrially cold-pressed rapeseed press-cake at different alkali pHs. Emulsifying properties and oxidation rates were assessed. Oleosin extracted at pH 9 stabilized smaller emulsion droplets than oleosin extracted at pH 12, although the protein yield was higher at pH 12. Emulsions were formulated from flaxseed oil and corn oil and were stabilized by oleosin, bovine serum albumin, de-oiled lecithin and Tween 20,h and the emulsions were stored in accelerated conditions (30 °C) for 12 days. Oleosin stabilized emulsions to the same extent as commercial food-grade emulsifiers. Flaxseed oil emulsions stabilized by oleosin had a significantly lower concentration of malondialdehyde (MDA) which indicates a lower oxidation rate compared to BSA, de-oiled lecithin and Tween 20. For corn oil emulsions, oleosin and BSA had a similar capacity to delay oxidation and were significantly more efficient compared to de-oiled lecithin and Tween 20. Rapeseed oleosin recovered from cold-pressed rapeseed press-cake could be a suitable natural emulsifier with anti-oxidation properties.

Sex-specific mutation rates in salmonid fish.

If germline mutations arise because of replication errors, the mutation rate may differ between males and females given that they differ in their number of germ cell divisions. As males of many higher organisms produce more gametes than females, this has led to the idea of "male-driven evolution." The extent of such male bias to the mutation rate is currently debated. For human some recent data suggest a very low bias, at a factor 1.7 only, while other approaches have given values of alpha(m) (the male-to-female mutation rate ratio) of 5, which is more close to what might be expected from male and female germ cell biology. Comparative analyses of sex-specific mutation rates in other organisms may be necessary for understanding the generality of an effect of sex and the number of germline DNA replications on the mutation rate. In this study we estimate for the first time sex-specific mutation rates in fish. Comparing the intronic substitution rates of the autosomal GH- 2 gene and its duplicated Y-linked and male-specific copy GH- 2Y (447-468 bp of each gene), we estimate alpha(m) to be 5.35-6.60 in salmonid fish of the genus Oncorhynchus. To the observations previously made among mammals and birds, this adds evidence from another class of vertebrates showing that a majority of mutations are of paternal origin. This would suggest that replication errors play a major role for the generation of new mutations.