Effect of roasting parameters on the physicochemical characteristics of high-molecular-weight Maillard reaction products isolated from cocoa beans of different Theobroma cacao L. groups

Abstract

This study explored the effects of roasting parameters on the yield, proximal composition, free phenolic compounds content, CIE L*a*b* color characteristics, browning index, fluorescence intensity, and molecular weight distribution of high-molecular-weight (HMW) melanoidin fractions isolated by dialysis (> 12.4 kDa) from cocoa beans of three Theobroma cacao L. types. The beans were roasted at four temperatures (110, 120, 135, and 150 °C) and two relative air humidity levels (RH 0.3 and 5.0%). To understand how roasting conditions affect the physicochemical properties of HMW fractions, changes in the content of carbohydrates, proteins, lipids, and phenolic compounds were determined for the tested cocoa beans. The yields of HMW products decreased after thermal processing at 110 and 120 °C, but increased at 135 and 150 °C. It was found that the applied roasting temperatures and RH levels caused a significant decline in carbohydrates, proteins, and free phenolic compounds in all HMW fractions obtained from cocoa beans. Roasting led to a considerable decrease CIE lightness. In addition, degree of browning and fluorescence intensity of HMW fractions tended to increase with increasing thermal treatment temperature. High-performance size-exclusion chromatography revealed that roasting led to significant changes in the molecular weight distribution of HMW fractions.