Non‐enzymic browning of lemon juice

Abstract The effect of various treatments on the non‐enzymic browning of lemon juice and model systems under aerobic conditions has been studied. Because of the high acidity (pH 2.5) of this product, it was unlikely that browning was due to sugar‐amine condensation and the results showed that ascorbic acid was the main precursor. Browning of lemon juice and model systems was proportional to the level of ascorbic acid; the presence of amino‐acids in model systems increased the intensity of browning. The investigation showed that the degree of non‐enzymic browning was influenced by the pH value of the product and was maximal at pH 4.5. Model systems demonstrated that ascorbic acid exhibited maximal browning at this pH value in the presence of citric acid and the part played by organic acids is considered to be important. There was evidence that although furfural was formed in the course of browning it was not an active compound in the development of coloured complexes.