Astaxanthin derivatives of the general formula (I) wherein R is in each
case group --NH--CH(R.sup.1)--COOR.sup.2, --OR.sup.3 or --(Y).sub.n-Z and
R.sup.1, R.sup.2, R.sup.3, Y, Z and n are significances given in detail
in the description, are novel compounds with improved stability during
extrusion at the elevated temperatures as required in feed manufacture
and during the storage of the manufactured feed and which accordingly are
useful as pigmenting carotinoids for feed for aquatic animals. The
derivatives are produced by reacting astaxanthin with the pertinent acid
RCOOH as such or as its acid chloride RCOCl or acid anhydride
(RCO).sub.2O, or, in the cases where R signifies a group
--NH--CH(R.sup.1)--COOR.sup.2, with the appropriate N-carbonyl-amino acid
ester of the formula OCNCH(R.sup.1)COOR.sup.2. The invention also
concerns a formulation containing such an astaxanthin derivative as the
pigmenting carotenoid for use in a feed for aquatic animals, a process
for producing such a formulation by dissolving the astaxanthin derivative
in a plant or vegetable oil or fat, or in an organic solvent, or in a
mixture of both a plant or vegetable oil or fat and an organic solvent,
emulsifying the solution with an aqueous solution of a protective
colloid, at least partially removing the solvent and water to afford a
concentrated emulsion, and spray-drying the concentrated emulsion to
finally produce a formulation suitable for incorporation in a feed for
aquatic animals, and a feed for aquatic animals containing such a
pigmenting carotenoid. 1
