Influence of microwave, the combined microwave/hot air and only hot air roasting on the formation of heat-induced contaminants of carob powders.

This study aims to investigate the effects of microwave, combined microwave/hot air treatment and hot air-only roasting on the formation of heat-induced contaminants of carob powders. Moisture content, water activity and pH values of the product decreased with the increasing roasting time and microwave power, while browning index (BI) and ultraviolet absorbance (UV-A) values were increased. While L and b values of carob powders decreased with increasing the roasting time and microwave power, a and ΔE values were increased. Varying roasting conditions also significantly affected the content of Maillard reaction products (MRPs): 5-hydroxymethylfurfural (HMF) (0.69-28.32 mg/kg dry matter), furfural (<LOD-10.44 mg/kg dm), furan (6.65-10.26 mg/kg dm) and acrylamide (78.69-122.87 µg/kg dm). MRPs contents increased with increasing the roasting time and microwave power. The highest MRPs were found in the samples roasted at 140°C for 20 min by hot air. Significant correlations between the amount of MRPs and colour values were found, especially with a and b values.