Wort Processing Using Pitaya (dragon fruit) Juices and its Effects on the Quality of Low-malt Beer

Abstract

　In this work, we evaluated the use of different pitaya fruits in the preparation of malt wort used in the subsequent production of low-malt beers with characteristic colours. Pitaya extracts and juices were obtained from the fruits of Hylocereus polyrhizus (red pitaya) and H. undatus (white pitaya). Preparation procedures were modified to optimize the influence of natural light and temperature on pitaya betacyanins during pitaya sterilization and storage. Our results showed that a sterilization temperature of 70℃, time of 30 min, and growth in the shade resulted in improved wort sterilization, with the characteristic colour of pitaya juice. Under identical culture conditions, using the wort containing sterilized whole and red flesh pitaya juice with an initial betacyanin concentration of 164 mg/ℓ, the ethanol concentration was greater than 5.9%, with betacyanin retention of over 50% at the end of maturation. Additionally, sensory evaluation of the obtained low-malt beers showed that the use of juice from red flesh pitaya was preferred to that of whole red pitaya by most testers. This is the first report describing the processing of low-malt beer using pitaya juice.