I have been doing some more research on rapeseed/ canola. For those who are beekeepers, and some who might just be interested here is some interesting information. Rape is a brassica and is from the same family as mustard. The are two type of rape. The biofuel type is high in erucic acid and is generally regarded as not suitable for human consumption. The other type is referred to as canola ( from Canada ola) which was developed in Canada and has a lower erucic acid content.
Here is a link to a very interesting scientific paper which gives an insight into the composition of the rape/canola nectar and why bees may or may not be attracted to it. It is pretty heavy reading, so be warned.
https://pdfs.semanticscholar.org/4a89/a ... b18324.pdf
Two main points.
The glucose content of rape nectar(using this generically) is richer in glucose over fructose and this leads to the rapid crystallisation in the comb ( and jar).
The presence of certain amino acids will make the nectar more or less attractive to honey bees. One amino acid, proline, is found in lower than typical levels and it is possible that bees can taste this acid, whilst a range of other amino acids are found in quite high levels, sometimes in excess of the ideal carbohydrate : amino acid ratio. The nectar composition combined with the amino acid distribution may make the nectar more or less desirbale to bees.