Light-induced changes in grated Graviera hard cheese packaged under modified atmospheres

Grated Graviera cheese was stored for up to 9 weeks under both fluorescent light and in the dark, packaged aerobically and under modified atmosphere packaging (MAP) of (a) 100% CO2, (b) 100% N2 and (c) 50% CO2/50% N2. Cheese samples stored under fluorescent light showed a higher degree of lipid oxidation (P < 0.05) (ca. 3–4 times higher for MAP samples and 20 times higher for aerobically packaged samples) and suffered a gradual discolouration compared with samples stored in the dark. Chemical composition did not produce statistically significant changes (P > 0.05) as a function of storage time. Solid phase microextraction–gas chromatography/mass spectroscopy was used to determine volatile compounds produced under specific packaging treatments. Free fatty acids, esters, aldehydes, ketones and alcohols were recorded for all treatments, with aerobic packaging and exposure to light giving higher concentrations of volatile compounds compared with other treatments. Sensory analysis showed that light, gas composition and storage time significantly affected (P < 0.05) taste and odour attributes of grated Graviera cheese. The best sensory attributes were obtained using 100% N2 or 50% N2/50% CO2 and storage in the dark. That is, samples packaged in either 100% N2 or 50% N2/50% CO2 retained acceptable taste for 9 weeks stored in the dark vs. 4 weeks under light. For aerobically packaged samples, respective shelf life was 2.5 weeks vs. 2 weeks.