Processing of astaxanthin‐rich Haematococcus cells for dietary inclusion and optimal pigmentation in Rainbow trout,Oncorhynchus mykiss L.

A range of physical cell disruption techniques have been evaluated to aid the processing of astaxanthin‐rich haematocysts of Haematococcus pluvialis for inclusion in salmonid feeds. Cell disruption by a scalable pressure treatment system was shown to be effective in breaking open the haematocysts without altering the content or isomeric composition of carotenoids in the algal cells. Storage of disrupted cells was optimal at ?20°C in the dark under nitrogen. Disrupted cells were spray‐dried, incorporated into commercial diets and fed to rainbow trout (Oncorhynchus mykiss L.). A marketable level of pigmentation in fish muscle was achieved after 10‐week dietary supplementation. The geometric and optimal isomer composition of the astaxanthin deposited in the muscle was nearly identical to that seen in Haematococcus. Changes were observed in the chirality of the astaxanthin deposited in the skin in comparison with that isolated from both the white muscle and the alga.