R ESEARCH ARTICLE doi: 10.2306/scienceasia1513-1874.2016.42.332 ScienceAsia 42 (2016): 332–339 Antioxidant properties and fruit quality of selected papaya breeding lines Kritsanee Iamjud a , Supornpan Srimat a , Peerapong Sangwanangkul b , Sirikul Wasee c , Kriengsak Thaipong a,d,* a Department of Horticulture, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140 Thailand b Postharvest Technology Centre, Department of Horticulture, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kampaeng Saen Campus, Nakhon Pathom 73140 Thailand c Tropical Vegetable Research Centre, Department of Horticulture, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140 Thailand d Tropical Fruit Research and Development Centre, Department of Horticulture, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom 73140 Thailand * Corresponding author, e-mail: kriengsak.t@ku.ac.th Received 26 Jul 2015 Accepted 24 May 2016 ABSTRACT: Nine selected S 3 papaya breeding lines were evaluated for their antioxidant properties and fruit quality. The 14 antioxidant properties and fruit quality traits measured in this study showed significant genotypic differences. KK80 showed the highest ascorbic acid content (114 ± 20 mg/100 ml), antioxidant activity (8.0 ± 1.3 μmol ascorbic acid equivalents/g fresh weight [FW]), and total phenolic compounds (72.2 ± 5.8 mg gallic acid equivalents/100 g FW). KD7 contained the highest amounts of total flavonoid (21.0 ± 5.8 mg catechin equivalents/100 g FW), lycopene (11.0 ± 1.7 mg/100 g FW), and β-carotene (10.0 ± 1.7 mg/100 g FW). The significant variation in antioxidant properties and fruit quality clearly shows the potential value of selected papaya breeding lines as new cultivars and parents in a breeding programme. Lycopene had a positive correlation with β-carotene ( r = 0.62). Fruit size showed a negative correlation with total phenolic compounds ( r = -0.64), antioxidant activity ( r = -0.45), and ascorbic acid ( r = -0.44). Flesh colour as hue angle was negatively correlated to lycopene ( r = -0.67), suggesting that lycopene may be estimated indirectly by using the hue angle. KEYWORDS: papaya breeding, antioxidant compounds, carotenoids INTRODUCTION Currently, there is an increasing interest in the se- lection of crops with higher antioxidant contents. Phenolic and flavonoid compounds and lycopene are effective antioxidants, while β-carotene is a pre- cursor of vitamin A. They have become widely stud- ied due to their free-radical scavenging properties which confer them potentially beneficial properties to human health 1 . Several epidemiological studies suggest that diets high in carotenoid pigments are associated with a reduced risk of cardiovascular diseases, prostate cancer, and lung cancer. Papaya (Carica papaya) fruit is a good source of carotenoids and an excellent source of vitamins that are power- ful antioxidants 2 . Several studies have reported the relationship between fruit quality and the antioxidant content of different fruits, for instance, the correlation of the fruit size and antioxidant contents of guava 3 , inter- nal fruit colour and carotenoid contents of mango 4 , and flesh colour and lycopene content of tomato 5 . The knowledge of the relationship between fruit quality traits and antioxidants is a useful tool to estimate whether selection for one trait will have an effect on another trait and so it can be used for indirect selection. In Thailand, papaya is an important commercial crop. However, the existing commercial papaya varieties of Thailand, such as ‘Khaek Dam’ and ‘Plug Mai Lai’ are not homozygous varieties and have some undesirable characters for both fresh consumption and processing. The papaya breeding program was therefore established in 2009 by the www.scienceasia.org