Stability of astaxanthin from red yeast, Xanthophyllomyces dendrorhous, during feed processing: effects of enzymatic cell wall disruption and extrusion temperature

Sammendrag

The effect of different degrees of enzymatic cell wall disruption (45%, 70%, and 97%) of red yeast (Xanthophyllomyces dendrorhous, formerly Phaffia rhodozyma) and extruder temperatures (102, 121, and 137 °C) on astaxanthin stability and formation of astaxanthin Z-isomers was determined during extruded fish feed production. Enzymatic cell wall disruption was expressed as acetone extractable carotenoids in percent of total amount of carotenoids. The recovery of added astaxanthin in the feeds was high (range 90–99%). The recovered amount of astaxanthin during feed production was 8% higher in the diets containing red yeast with 45% enzymatic cell wall disruption than in the diets containing 97% disrupted yeast cells. Extruder temperatures in the range 102–137 °C did not significantly affect astaxanthin recovery. The proportion of astaxanthin Z-isomers of total astaxanthin increased during feed production. The proportion of all-E-astaxanthin was higher in the mash and feeds containing yeast with 45% cell wall disruption than in the ones with 70% and 97% disrupted yeast cells. Extruder temperature had little influence on the astaxanthin E/Z isomer composition. Significant interactions (P<0.05) were observed for process unit operation (P) and enzymatic cell wall disruption (D) (P∗D), and D and extrusion temperature (T) (D∗T) for astaxanthin concentration of the feeds and recovery, and for P∗D and P∗T for the proportions of all-E-, 13Z-, and 15Z-astaxanthin. The decrease in astaxanthin stability caused by increased enzymatic disruption of the cell wall was of less importance than the improvements in bioavailability of astaxanthin for pigmentation of rainbow trout.