LIGHT FROM MAILLARD REACTION - PHOTON-COUNTING, EMISSION-SPECTRUM, PHOTOGRAPHY AND VISUAL-PERCEPTION

Several authors have reported on high-sensitivity measurement of oxyge n-dependent low-level chemiluminescence (CL) from Maillard reactions ( NIR), i.e. nonenzymatic amino-carbonyl reactions between reducing suga rs and amino acids (also referred to as nonenzymatic browning). Here w e report for the first time, that light from Maillard reactions can be seen by the human eye and also can be photographed. In parallel with visual perception and photography CL was monitored by means of a CL-de tection programme of a liquid scintillation counter (LSC, single photo n rate counting). CL emission spectrum was recorded by a monochromator -microchannel plate photomultiplier arrangement. CL intensity from rea ction of 6-aminocaproic acid with D-ribose (200 mg each) in 5 mt H2O a t pH 11 at 95 degrees C was high enough for visual perception after ad aptation to absolute darkness. Reaction in dimethylsulphoxide (DMSO) e xhibited strongly enhanced CL (10 mg each in 5 mL were sufficient for visual detection) and could be photographed (15 minutes' exposure, ASA 6400); all characteristics of Maillard specific CL (O-2-dependence. n o CL from nonreducing sugars, inhibition by sulphur compounds) remaine d. Visual detection of CL and measurement by LSC were in full concorda nce. The CL emission spectrum showed two broad peaks at around 500 nm and 695 nm. Fluorescence emission of the brown reaction mixture matche d the blue-green part of the CL emission spectrum. Emission of visible light during Maillard reactions may partly originate from oxygen-depe ndent generation of excited states and energy transfer to simultaneous ly formed fluorescent products of the browning reaction.