Dragon fruit freshness detector based on methyl red colour indicator

Abstract

Dragon fruit is kind of non-climacteric fruit that is difficult to know its freshness. Smart label based on methyl red colour indicator can be used to determine the freshness of this non climacteric fruit. This study aimed to develop smart labels with methyl red indicator in, and to apply the label to detect the freshness of the dragon fruit. The colour of the label changed from yellow to red due to CO 2 presence in the package while the test showed that there was an increasingly significant colour change along the storage of the dragon fruit. The changing of colour was seemly affected by volatile acid compound from fruit respiration. Application of label on dragon fruit showed the relationship between the changing of label colour with the declining of fruit quality. The ?hue values of label on days 0 th to 4 th showed from yellow to orange, while on the day 5 th to 7 th the label have changed to red. The decrease of fruit quality during storage could be seen from pH value, weight loss, hardness and total titrated acids content. It was concluded that the methyl red compound could be used as colour agent in label to show the freshness of dragon fruit.