The sulphur volatile data set included integrated PFPD peak
area values (ChromPerfect software version 5.0) from the three rice
types. Principal component analysis (PCA) was carried out using
Unscrambler version 10 from Camo (Woodbridge, NJ). In order
not to overemphasise the larger peaks, the data from all peaks
were normalised by setting mean values to zero and scaling on
the basis of one standard deviation.