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The effect of extraction conditions on the total phenolic content, tannin content and antiradical activity of carob extracts

The main goal of conducted study was to enhance extraction rates of phenolics from carob pods. Namely, carob fiber is rich in amount and variety of phenolic antioxidant substances, and therefore, could be used as the source of natural antioxidants in everyday nutrition or in creating novel functional foods with increased content of antioxidative bioactive compounds. Four extraction procedures described in literature (reflux cooking, shaking overnight at room temperature, shaking at 37 °C, ultrasound extraction) and three types of solvents (water, 50% ethanol, 80% ethanol) were evaluated regarding total phenolic content, tannin content and antiradical activity of obtained extracts. The procedures with the highest extraction yields were modified in order to additionally increase extraction efficiency. Reflux cooking and ultrasound extraction were found to be the most efficient procedures for extraction of antioxidants from milled carob pods resulting in the highest total phenolic content and the highest antiradical activity of obtained extracts. In order to additionally increase the yields, duration of mentioned procedures was extended several times until maximum yields were achieved. Finally, 60-minute reflux cooking of carob pods with water was found to be the most efficient way for extraction of phenolic antioxidants from carob, resulting in the following yields: total phenols/tannins: 993.32±49.95/539.30±32.93 g tannic acid equivalents/100g dry matter ; Trolox equivalent antioxidant capacity: 15631.62±369.10 mg Trolox equivalents/100 g dry matter. Application of high temperature in combination with polar solvent was found to be the most efficient way for extraction of antioxidants from carob pods, probably due to the fact that the majority of carob phenolics are bound to the dietary fiber fraction and cannot be extracted when mild extraction conditions are applied. The extension of extraction time was stopped at 60 minutes since further prolongation did not significantly influence obtained extraction yields.

carob; antiradical activity; extraction; phenols

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