Effect of Light on Alteration of Nutritional Value and Flavor of Milk: A Review

Abstract

Milkin glass,polycarbonate,highdensitypolyethylene, blow-molded polyethylene, plastic bags and paperboard containers, whenexposedto fluorescent light or sunlight, will develop a characteristic off-flavor described synonomously by many researchers as activated, sunlight or oxidized flavor. The extent of flavor development is related to the exposure interval, strength of the light and amount of milk surface exposed. Paperboard containers, particularly those with large printed areas of dark ink or foil in the laminate, offer the best protecton to milk,while the remainingcontainersofferedlimitedprotectionat best. Characteristic flavor is produced prinicipally by conversion of methionine to methional. Partial loss of vitamins B2 and C and some amino acids parallel dwelopment of light-induced off-flavor. Loss of other constituents is minimal. Manyresearchersofferedsuggestionsto improve the flavorjstability of milk held in display cases illuminated with fluorescent lights. Amongthese are changes to more protective packaging,reductionof radiant energyto 538lux, use of gold or "bug light" types of fluorescent lights and more dark ink areas on exposed parts of paperboardcartons (gables and maindisplay panels). Perhaps grocersshould bag all containers of milk to afford adequate protection fromsunlight betweenpoints of refrigeration.