ROASTING EFFECT ON THE CAFFEINE CONTENTS AND ANTIOXIDANT POTENTIAL OF DIFFERENT COFFEE GRADES AVAILABLE IN THE SAUDI MARKET

In the Saudi market different grades of coffee (Coffee arabica) are available based on the degree of roasting. However, some unique grades subjected to very mild roasting are available for the preparation of the popular “Arabic Coffee”. Caffeine contents were quantified by HPTLC method in the five available grades of coffee and coffee seed shells “Coffee Husks”. Caffeine contents were estimated in both hydro-alcohol and aqueous extracts of the coffee grades using silica gel 60 F₂₅₄ plates and ethyl acetate: methanol 85:15 (%, v/v) as mobile phase. A good linear relationship between peak area and caffeine concentration in the range of 100-600 ng/band was obtained. The proposed HPTLC method was validated following the ICH guidelines. The antioxidant activity using DPPH radical scavenging and Ferric-reducing power assays to explore the effect of roasting on the phenolic contents. The results indicated that increase roasting decrease both caffeine contents and antioxidant activity.

Key words: Arabic coffee; Husks; Roasting; Caffeine; antioxidant; HPTLC