Roasting temperature impact on bioactive compounds and PAHs in Carob powder (Ceratonia siliqua L.)

The impact of roasting temperatures (100, 120, 150 and 180° for 25 min) on the bioactive compounds, sensory and physicochemical properties of carob pods powder as well as the polycyclic aromatic hydrocarbons content (PAHs) were studied. The study also investigated whether roasting the dried carob pods (PO) or dried carob powder (CPW) is better used in the food industry. Increasing roasting temperatures resulted in several changes in the chemical composition of carob pods powder, as evidenced by significantly lower water content, protein, fat, total sugar and pH values. This increase also was accompanied by a significant increase in ash, fibers, total polyphenols, total flavonoids, and condensed tannins contents. Raw carob powder and roasted powder at 180°C showed the least acceptable organoleptic properties while roasting powders at 120 and 150°C showed the best results in terms of taste, color, odor, texture, and overall acceptability. PAHs ranged from 3.37 to 22.59 µg/kg, and carcinogenic PAHs ranged from 1.38 to 10.16 µg/kg of roasted carob powder. The difference among the detected levels in different roasting degrees was significant ( P ≤ 0.5). Carob powder roasted at 180°C had a total PAHs content higher than other samples roasted at lower temperatures. Roasting at higher temperatures was not acceptable and not applicable due to the occurred partial carbonization and undesired sensorial characteristics formation.