Heard it during a beekeepers' question time at Epping Forest many years ago, and the beekeeper described in detail, but all has eluded me. I'll ask around.
[/Q
Found it! erucic acid.
https://en.wikipedia.org/wiki/Erucic_acid
Originally, Rapeseed was reserved purely for machinery oil and occasionally fed to cattle, as it was largely unpalatable and contained a toxic substance called erucic acid.
However, in 1973 Canadian scientists bred strains that were low in erucic acid and glucosinolate – the bitter substance that made it unpalatable – making it edible and safe for humans and cattle. Rapeseed innovation largely originated in Canada and, in 1978 Canadian company ‘Western Canadian Oilseed Crushers Association’ registered a product called
‘Canola’ – a contraction of
‘CANada’ and
‘OLA’ – from
‘Oil Low Acid’.
