Abstract
The effect on color of the initial pH employed in dulce de leche (DL) production was evaluated through physicochemical and spectroscopical characterization of the melanoidins formed in the process. Melanoidins originated at pH values of 6.5, 7.0, and 7.5, and they were released by the enzymatic hydrolysis of the protein backbone and purified by gel filtration. They showed a significant degree of polydispersity, in general, with molecular weights (MWs) below 1,800 Da. DL produced at a higher pH released melanoidins with higher average MW after the enzymatic hydrolysis. They also presented darker colors (dE*ab, C*), more closely resembling those typical of the commercial product. Analysis of the fractions isolated by gel filtration using HPLC-DAD and multinuclear NMR showed an heterogeneous and complex composition. Even though structurally related, the 1H NMR spectra of melanoidins showed a higher degree of aromaticity at higher pH values. In conclusion, the pH employed in DL production affects the amount and structure of the colored products originated by MR reactions, and thus the color of the final product.
Highlights
Dulce de leche (DL) is a brownish, viscous concentrated dairy product with a high sucrose content
Melanoidins in DL are found forming high molecular weights (MWs) melanoproteins, mainly in the water-insoluble component that is formed at advanced stages of processing in the analyzed pHi range
The main colored compounds released by enzymatic hydrolysis had low MW ≤ 1,800 Da and were more abundant in the melanoproteins from DL prepared at higher pHi
Summary
Dulce de leche (DL) is a brownish, viscous concentrated dairy product with a high sucrose content. Mainly due to the occurrence of the nonenzymatic browning Maillard Reaction (MR), are highly valuated by consumers. DL is an extremely popular confectionary product, in South America. In Uruguay alone the industrial production of DL reaches 7,000 tons per year. Taking into account informal production, which is estimated to reach comparable levels, leads to a yearly consumption of nearly 4 kg per capita [1]. DL is Melanoidins in Dulce de Leche: pH Effect consumed in a variety of ways, including pastry and bom bom filling, toast and cookie spread, and ice cream preparation [2]
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