Sensors 2012, 12, 6023-6048; doi:10.3390/s120506023 sensors ISSN 1424-8220 www.mdpi.com/journal/sensors Article Improved Maturity and Ripeness Classifications of Magnifera Indica cv. Harumanis Mangoes through Sensor Fusion of an Electronic Nose and Acoustic Sensor Ammar Zakaria *, Ali Yeon Md Shakaff, Maz Jamilah Masnan, Fathinul Syahir Ahmad Saad, Abdul Hamid Adom, Mohd Noor Ahmad, Mahmad Nor Jaafar, Abu Hassan Abdullah and Latifah Munirah Kamarudin Centre of Excellence for Advanced Sensor Technology (CEASTech), Universiti Malaysia Perlis (UniMAP), 01000, Kangar, Perlis, Malaysia; E-Mails: aliyeon@unimap.edu.my (A.Y.M.S.); mazjamilah@unimap.edu.my (M.J.M.); fathinul@unimap.edu.my (F.S.A.S.); abdhamid@unimap.edu.my (A.H.A.); mohdnoor@unimap.edu.my (M.N.A.); mahmad@unimap.edu.my (M.N.J.); abu.hassan@unimap.edu.my (A.H.A.); latifahmunirah@unimap.edu.my (L.M.K.) * Author to whom correspondence should be addressed; E-Mail: ammarzakaria@unimap.edu.my; Tel.: +604-979-8931. Received: 22 April 2012; in revised form: 3 May 2012 / Accepted: 3 May 2012 / Published: 10 May 2012 Abstract: In recent years, there have been a number of reported studies on the use of non-destructive techniques to evaluate and determine mango maturity and ripeness levels. However, most of these reported works were conducted using single-modality sensing systems, either using an electronic nose, acoustics or other non-destructive measurements. This paper presents the work on the classification of mangoes (Magnifera Indica cv. Harumanis) maturity and ripeness levels using fusion of the data of an electronic nose and an acoustic sensor. Three groups of samples each from two different harvesting times (week 7 and week 8) were evaluated by the e-nose and then followed by the acoustic sensor. Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were able to discriminate the mango harvested at week 7 and week 8 based solely on the aroma and volatile gases released from the mangoes. However, when six different groups of different maturity and ripeness levels were combined in one classification analysis, both PCA and LDA were unable to discriminate the age difference of the Harumanis mangoes. Instead of six different groups, only four were observed using the LDA, while PCA showed only two OPEN ACCESS