Effect of different wavelength of light on the formation of photo-oxidation in Gouda-like cheese

Norvegia cheese samples were packed in air and nitrogen atmospheres and exposed to light of different colours, blue (350-560 nm), green (450-620 nm) and red (580-700 nm). After 7 days of light exposure, each cheese was sliced, from the exposure surface and down, into eight slices of 3 mm thickness. The slices were analyzed by sensory analysis and fluorescence spectroscopy, enabling studies of how photo-oxidation progressed as a function of depth of the cheese. Green light gave the most oxidation at the surface for air stored samples. Oxidized flavours at depths down to 9 mm were more intense for exposure to red and green light. Blue light degraded riboflavin in the two upper layers (0-6 mm), whereas red and green light affected hematoporphyrin, protoporphyrin IX and chlorophyll as far as 21 mm into the cheese. The results suggest that tetrapyrroles are responsible for photo-oxidation at the surface and the interior of the cheese.