Effect of storage, light and homogenization on the colour of ultra heat treated and sterilized milk

Abstract

SummaryThe rates of change in light reflectance and in CIELAB tri-stimulus colour values were compared for direct and indirect ultra heat treated (UHT) and sterilized milk in glass and polyethene bottles stored under different conditions. The rate of change of milk reflectance was higher at shorter wavelengths and the milk colour changed more rapidly at 30 and 37 °C than at room temperature. Sterilized milk in polyethene bottles was bleached when stored in an illuminated cabinet. The colour of skimmed milk changed more rapidly than that of whole milk. The rate of change in reflectance of direct UHT milk above 590 nm was found to be higher than in other milks. A statistical interaction was found between the fat content and the storage temperature for the CIELAB values. The homogenization pressure used in processing UHT milk samples did not affect the rate of change of the milk colour. The main implication of these findings may be that milk colour cannot be used to assess the heat treatment of a milk when the age or storage conditions of the milk are unknown.