Browning reactions between oxidized vegetable oils and amino acids Parkányiová, E. B. Hutapea, L. Parkányiová, M. Miyahara, H. Sakurai, J. Pokorný (2004): Browning reactions between oxidized vegetable oils and amino acids. Czech J. Food Sci., 22: 113-115.
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Browning of stored food products, not exposed to heat treatment, is generally considered as a negative
process. The formation of brown pigments at a temperature close to storage temperatures was followed in mixtures
of either free fatty acids or vegetable oils with amino acids, deposited on cellulose fibres. The mixtures were
studied at 50°C at free access of oxygen, and the browning process was monitored by reading the absorbance of
brown products at 430 nm. Mixtures of free fatty acids and amino acids were turning brown in relation to their
unsaturation degree. Mixtures of vegetable oils deposited on cellulose fibres were less coloured than if they were
oxidized in presence of amino acids. The rate of browning increased with the degree of unsaturation in case of
vegetable oils similarly as in case of free fatty acids. The browning degree was nearly the same in mixtures of
oxidized fatty acids or vegetable oils with alanine, valine, lysine, serine or cystine, the browning was intermediate
in mixtures with cysteine or methionine, but it was substantially more intensive in mixtures with proline or
tryptophan. No significant difference was observed among different oils, but the discolouration was less rapid in
case of low unsaturated peanut oil and more rapid in case of highly unsaturated linseed oil. The browning rate
increased to a substantial degree with increasing cupric ion content, but decreased after addition of both synthetic
and natural antioxidants, which decrease the oxidation rate.

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