Chemiluminescence of cereal products II. Chemiluminescence spectra

Spectra of ultraweak chemiluminescence (CL) accompanying auto-oxidation and hydration of cereal products have been measured using single photon counting and cut-off filters. The spectra cover the 380-880 nm spectral range with maxima centred around 600 nm. Analytically pure air-dried carbohydrates like agar, cellulose and nitrocellulose give emission too weak for spectral measurements. The emission from water pure carbohydrates is on average 4-12 times higher and emission spectra are similar to those from cereal products. The effect of free radical scavengers, SOD and O2* (1 delta g)-quenchers on CL spectra indicates a contribution of radical reactions with the participation of excited carbonyls, O2- and excited molecular oxygen dimoles. Moreover, possible mechanisms of chemi-excitation due to a cooperative H-bond formation during the hydration of carbohydrates and/or recombination of trapped radicals and electron-holes are discussed. It is also postulated that the excitation energy transfer to natural sensitizers occurring in cereal products may account for non-specific broad spectra and differences in the intensity of CL.