PHYTOCHEMICAL CONTENTS AND ANTIOXIDANT ACTIVITIES OF PASTEURIZED CITRUS AURANTIUM L. (BITTER ORANGE) JUICE

Abstract

Bitter orange (Citrus aurantium L.) is an ancient therapeutic plant. Normally, peels of bitter orange fruit are used as a food ingredient in Thailand, leaving the pulp as waste. This research aimed to develop pasteurized bitter orange juice by studying the effect of dilution and pH on phytochemical contents and antioxidant activity. The bitter orange juice concentrations were prepared at 50, 75, and 100% w/v by DI water and adjusting pH at 2.5, 3.0, and 3.5 by using potassium chloride. The bitter orange juices were pasteurized at 70°C for 5 min. The result showed that 100% w/v pasteurized bitter orange had the highest contents of titratable acidity, ascorbic acid, and total phenolic, approximately 41.60 to 48.67 g/L, 31.26 to 32.26 mg/100 mL, and 54.80 to 57.08 mg GAE/100 mL of juice, respectively when compared to other concentrations. Likewise, antioxidant activity results (DPPH, ABTS, and FRAP) of 100% w/v pasteurized bitter orange juice gave the highest values about 390.58 to 458.15 GAE/100 mL of sample 546.20 to 503.33 µg Trolox/100 mL of sample, and 525.55 to 422.48 µg Trolox/100 mL of sample.

The pH variation did not affect the alteration of phytochemical and antioxidant activities in 100% w/v pasteurized bitter orange (p<0.05). Conversely, pH adjusting of 50 and 75% w/v pasteurized bitter oranges showed significant differences in the ascorbic acid and total phenolic contents (p≤0.05) but non-significant differences in citric and ascorbic acid contents. All pasteurized bitter orange juice microbiological resulted showed that the total coliform counts was <2.2 MPN/ 100 mL of sample and yeast and molds were not detected initially and after 5 days of storage, confirming the safety of the pasteurization process.