Impact of starch gelatinization on the kinetics of Maillard reaction in potato dehydrated systems

The non-enzymatic browning (NEB) reaction plays an essential role in food acceptance and quality. There has been increased interest in revealing the role that water plays in native and gelatinized starch. However there is a lack of information on the relationship between the water dynamics of water–starch interactions and the kinetics of NEB reaction in native and gelatinized starch systems. The objective of the present work was to analyze the changes in water-distribution and water-solids interactions that take place after starch gelatinization and to elucidate their influence on the kinetics of the Maillard reaction in low moisture potato starch systems. Freeze-dried native (NS) and gelatinized (GS) potato starch systems containing glycine and glucose were prepared. H NMR relaxation times (T2), thermal transitions and water sorption isotherms were analyzed. Maillard reaction was studied at 70oC. In NS Maillard rate was inversely dependent on RH. In GS the rate increased up to RHs between 75 and 84 % and then decreased at higher RHs. In the NS matrix, which is almost inert towards Maillard reaction, reactants are concentrated in the inter-granule spaces. NS has also lower tendency to retain water than GS, and the water formed during Maillard reaction is not retained by the matrix, being available to act as inhibitor. This explains the high Maillard rate at low RHs and the continuous inhibiting effect of water observed in NS. GS presents a more homogeneous distribution of Maillard reagents within the matrix, which renders a more dilute system regarding browning reagents, and also less water availability for the reaction. The “dilution” of the reagents makes this system more diffusion dependent. This can explain the low Maillard rate at the lower RH values in the GS matrix, which increases above the glass transition temperature (Tg) value and decreases when solvent water appears.