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Impact of roasting conditions (time and temperature) on Maillard reaction indexes and antiradical capacity of carob

The main goal of this study was to investigate the effect of roasting conditions on antioxidant and browning properties of carob. The formation of Maillard reaction products (MRPs) during roasting was investigated by monitoring changes in browning index, free fluorescence and UV absorbance at 294 nm. The changes of the antioxidant activity were monitored using the ORAC–FL antioxidant assay that was expressed as Trolox equivalent (TE). Kibbled carob pods were roasted for 0, 5, 10, 15, 30, 60 and 90 minutes at 130, 150 165, 180 and 200 °C. Generally, antioxidant activity and MRP formation increased with the increasing roasting temperature and time. In comparison to the raw carob (52, 311 µmole TE/g dry matter), the highest antioxidant activity (91, 442 µmole TE/g dry matter) was found in carob powder processed at 200˚C. Since that sample was found to be organoleptically unacceptable, 30 minute roasting at 165˚C (73, 809 µmole TE/g dry matter) and 60 minute roasting at 150˚C (74, 633 µmole TE/g dry matter), were found to be ideal for carob processing due to preserved organoleptic texture and increased antioxidant activity. The content of UV-A absorbing products, melanoidins and the MRPs formed during roasting correlated positively with measured ORAC values but at different roasting temperatures, different subclasses of MRPs showed the most significant correlations. In samples roasted at 150°C the most significant correlation was found between the ORAC values and the content of pentosidines, pentodilysines, cross links and the pyropiridines while theargpyrimidines and AGEs in general reported the strongest antiradical potential in the processing at 200˚C and 165˚C. Obtained results present additional guidelines in choosing proper processing conditions with remark that final choice should primarily depend on the target purpose and desired characteristics of carob derived product and should take into account possible biologically harmful and antinutritive effects of derived MRPs.

Maillard reaction products; carob; roasting; ORAC antioxidant activity

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