Assessment of the influence of vanillin, vanilla extract and sodium metabisulfite on Maillard reaction in sweetened condensed milk and doce de leite

Abstract

The Maillard reaction (MR) is driven by the glycation of proteins with reducing sugars available in different food matrices, followed by various oxidation-reduction reactions. Therefore, it is expected that molecules with antiglycant properties or antioxidant activity could interfere with the progress of this reaction. The literature reports that vanillin, an aldehyde synthesized or extracted from two vanilla fruits is a common flavoring, with antiglycant activity and, therefore, could modify the evolution of MR. The objective of this study was to evaluate the influence of vanilla extract (VE) and its main component, vanillin (V), the RM into condensed milk (SCM) heated to force MR. Sodium metabisulfite (SMB) is used as a positive MR retarding agent. The progress of the reaction was measured by the profile of free furfurals 5-hydroxymethyl-2- furaldehyde (HMF), 2-furaldehyde (F), 2-furyl-methyl ketone (FMK), and 5-methyl-2- furaldehyde (MF), pH and color (Browning Index, BI). Samples of SCM were added with SMB, VE, and V, separately, with concentrations of 0.05 to 1.0% (w/w) and stored at 40°C for 21 days, and compared as profiles for the same parameters of samples only with SMB in these concentrations, heated at 121 °C/15 min. The concentration profile of two free furfurals F, MF, and FMK was lower than the quantification limit of the method (0.125, 0.128, and 0.066 µg/mL, respectively), and only free HMF was quantifiable. The SCM showed a pH of 6.3 ± 0.02, a BI of 14.3 ± 0.7, and a concentration of 63.2 ± 0.5 μmol HMF/kg. SMB was added at 1.0% (w/w) to the SCM, or HMF decreased to 40.8 μmol HMF/kg. It was also observed that our SCM, adding 0.05% and 1.0% (w/w) of SMB, would present only a slight increase of 20.1 and 15.2 of BI after heating, respectively. As SCM samples with the addition of 1.0% SMB, V and VE reached 311.4 ± 47.7 μmol HMF/kg, 205.7 ± 41.0 μmol HMF/kg, and 286.7 ± 97.9 μmol HMF /kg, respectively, being that the last two samples show darkening. In samples with 0.05% and 1.0% (p/p), we verified respectively an increase in BI to 35.0 and 83.0 for V and a smaller increase of 29.5 and 29.6 for VE. The SMB reduced the initial pH of the SCM to 5.7 ± 0.1, keeping it constant, while V and VE did not alter the initial pH and kept it constant. Tests using different acids to obtain a pH of 5.7 ± 0.1 as the samples of SMB 1.0% (w/w) showed darkening, suggesting that the retarding effect of RM due to SMB is not just a consequence of the diminution do pH. Contrary to what was expected, V favored RM, presenting a darkening of samples. However, VE did not favor RM, presenting HMF, pH, and BI values like the SCM control, becoming a promising natural additive and an alternative to artificial additives.