73 Measurement of Mango Firmness by Non-Destructive Limited Compression Technique P. Penchaiya, A. Uthairatanakij, L.M.M. Tijskens V. Srilaong and S. Kanlayanarat Horticulture and Plant Physiology Postharvest Technology Program Wageningen University School of Bioresources and Technology The Netherlands King Mongkut’s University of Technology Thonburi Bangkok A. Tansakul Thailand Department of Food Engineering Postharvest Technology Innovation Center Faculty of Engineering Office of the Higher Education Commission King Mongkut’s University of Bangkok Technology Thonburi Thailand Bangkok Thailand Keywords: mango, non-destructive quality evaluation, firmness, compression Abstract Thai mango ‘Nam Dok Mai Si-Thong’ has an attractive golden yellow skin colour even in immature fruit, not ready for consumption. Firmness becomes an important quality attribute to assess the ripening stage of the fruit during storage. In this study, the possibility of a non-destructive method using a texture analyser for assessing the firmness behaviour during storage was investigated in three different experiments for (1) probe selection, (2) distance selection using the selected probe and (3) evaluation of the selected probe and distance on mango quality. The results revealed that an aluminium flat probe with 35 mm diameter is a suitable probe for measurement. Limited distance compression at 1 mm was selected since that combination did not leave any compression marks on the fully ripened mangoes. Evaluation of mango quality attributes obtained by this technique could be used to assess non-destructively the firmness behaviour of the mango fruit during storage. The technique can be used to monitor the firmness of mango fruit on an individual basis, using the same fruit in successive assessments. Non-linear indexed regression can be applied to extract information on the behaviour and variation of firmness of individual mangoes. Obtained explained parts (R 2 adj ) frequently are well over 90%. INTRODUCTION In Thailand, mango ‘Nam Dok Mai Si-Thong’ is one of the most popular cultivars for export. The attractive golden yellow skin is the major characteristic, (Si-Thong in Thai means golden colour). The fruits are grown in carbon bags during 45 days after fruit set to protect them from the oriental fruit fly and reduce an anthracnose incidence (Sangchote, 2013). Fruit bagging enhanced their appearance by reducing development of chlorophyll and by increasing carotenoid content (Chonhenchob et al., 2011). Therefore, the skin colour of ‘Nam Dok Mai Si-Thong’ becomes yellow even when the fruit is still immature. ‘Nam Dok Mai Si-Thong’ is recommended for consumption at the fully ripen stage. Their juiciness and sweetness will highly satisfy the consumers. Due to only slight changes in skin colour during storage, texture or firmness becomes the only one quality attribute to assess the ripening stage of this cultivar. Experienced sorters can classify fruits at different maturity to reduce the variation at harvest. Less experienced sorters or buyers could have difficulties in assessing the maturity stage, which leads to an improper maturity and inedible fruits. Many researchers developed various techniques for maturity classification using acoustic or spectroscopic techniques based on fruit firmness (Jarimopas and Kitthawee, 2007; Jha et al., 2005; Polderdijk et al., 2000). Some studies introduced the simple compression techniques to classify mango maturity (Sirisomboon et al., 2008). Most firmness studies in mango usually worked with destructive techniques Proc. II nd Southeast Asia Symp. on Quality Management in Postharvest Systems Eds.: A.L. Acedo Jr. and S. Kanlayanarat Acta Hort. 1088, ISHS 2015