Bitterness masking effects of carob syrup in bitter orange (Citrus aurantium) jam production

Abstract

Pre-processes such as blanching, which cause time, labor and economic losses, are carried out to remove the peel bitterness during bitter orange (Citrus aurantium) jam production. During these processes, many flavonoids and tannins in the fruit peel are lost. In this study, it was aimed to mask the bitterness without blanching of the peel by using carob syrup in different concentrations (0%, 25%, 50%, 75%, 100%) instead of granulated sugar. Samples were examined in terms of compositional properties (pH, titratable acidity, Brixº, moisture, total sugar and crude fiber contents), total phenolic compounds and antioxidant activity, color (L*, a*, b*) and sensory properties (appearance, color, odor, texture, taste, bitterness, fluidity). The interaction of gallic acid and tannic acid with naringin was also analyzed sensorially and spectrophotometrically to determine the source masking the bitterness. As a result, the total sugar content of jams reduced and the crude fiber, total phenolic compounds and antioxidant activity increased with use of carob syrup. The use of carob syrup also improved the sensory properties of the jams such as brightness, texture, odor, taste and bitterness. In particular, no bitterness was detected in jams produced with 100% carob syrup. Thus, it was observed that the bitterness from the bitter orange peel could be masked by using only carob syrup without the need for blanching. It was determined that phenolic compounds (especially gallic acid) found in high amounts in carob syrup formed a complex with naringin, which causes bitterness, so naringin was suppressed and bitterness was masked.