The optimisation of fresh fruit bunch (FFB) sterilisation process was studied using different degree of FFB ripeness (i.e. under-ripe, ripe, overripe) and loose fruits. This study was carried out with the application of Response Surface Methodology (RSM), based on the interrelation between process temperature (X1; 100 to 120oC) and time (X2; 20 to 80 min) used for FFB sterilisation process on Free Fatty Acid, FFA (Y1,underripe FFB; Y2,ripe FFB; Y3,Overripe FFB; and Y4,loose fruits). Thirteen experimental runs were conducted per degree of ripeness using laboratory scale steriliser with varying sterilisation temperature and time, as generated by Central Composite Rotatable Design (CCRD). Raw experimental data trend showed substantial FFA increment with the increment of FFB maturity. Four polynomial models were found appropriate to predict the responses within experimental regions. Analysis regarding factor influences on each response was performed using Analysis of Variance (ANOVA) and graphical analysis. For under-ripe and ripe FFB, the temperature exerted higher and significant (p