Wavelength dependence of light-induced lipid oxidation and naturally occurring photosensitizers in cheese.

Degradation of the potential photosensitizers, riboflavin, chlorophyll, and porphyrin, in Danbo cheese by monochromatic light of wavelength 366, 436, or 546 nm was studied. Three cheeses were investigated, two conventional (16% fat and 25% fat) and one "organic" (25% fat). The effect of illumination was measured by fluorescence spectroscopy and analyzed using multiway and multivariate data analysis. Riboflavin was found to degrade only by 436 nm light, whereas chlorophylls and porphyrins also were influenced by 436 and 546 nm light. The organic cheese had the largest chlorophyll content both before and after similar light exposure, and no change in chlorophyll of this cheese was observed for any of the illumination wavelengths. Upon light exposure of the cheeses, volatile compounds were formed, as analyzed by gas chromatography-mass spectrometry (GC-MS). The relative concentrations of methyl butanoate, 1-pentanol, benzaldehyde, 2-butanone, 2-heptanone, and butyl acetate were found to weakly correlate with the surface fluorescence intensity. 1-Pentanol and the ketones are secondary lipid oxidation products, consistent with a chemical coupling between photosensitizer degradation and formation of volatile lipid oxidation products.

Chemical and sensory characterisation of pan-fried pork flavour: Interactions between raw meat quality, ageing and frying temperature.

The effect of raw meat quality and cooking temperature on flavour generation in pork was investigated. The semimembranosus muscle was varied through genetics (carrier (HLY) and non-carrier (DLY) of the RN(-) allele) and ageing at 2°C (2, 15, and 22 days), whereas the pan-frying temperatures were 150°C and 250°C. HLY gave more pronounced 'fried' and 'burnt' notes than DLY after frying. This could partly be explained by a significantly higher concentration of glucose and glucose 6-phosphate in HLY after 22 days of ageing. HLY was generally perceived as more sour, which correlated well with the measured pH of HLY, but not to the l-lactate concentration. HLY was furthermore perceived as more tender and juicier than DLY, both attributes increased during ageing. Lipid-derived aroma volatiles dominated the samples fried at 150°C, while those from Maillard reactions mostly prevailed in the aroma profile at 250°C.