Milks pigmentation with astaxanthin and determination of colour stability during short period cold storage

Astaxanthin has been used as a colorant and antioxidant with excellent results, its application and stability in food matrices to human consumption has been little studied. The aim of this work was the incorporation of astaxanthin oleoresin to milks with different fat content, simulating the red-orange color that can impart apricot fruit. For astaxanthin determination by HPLC, a methodology was implemented for its extraction from the food matrix, followed by saponification with KOH. Milk samples were stored (5 ± 2 °C) and stability of color and astaxanthin content were determined by colorimetry and high performance liquid chromatography each 24 h for a week. Pigment degradation followed first-order kinetic with a constant degradation of 0.259 day⁻¹ and 0.104 day⁻¹, in whole and semi-skimmed milk, respectively. Chromaticity coordinates L*, a*, b* for different types of milk showed a low dispersion of their values during the storage time, indicating high stability of astaxanthin within the matrix.