Modification of resistant starch content in banana flour using response surface methodology

Green banana contain an excellent amount of resistant starch. Over the last two decades, resistant starch has drawn a huge attention due to its benefits on human's health. For the last 20 years, Malaysia has recorded one of the highest levels of obesity rate across South East Asia. The green banana flour is an alternative way to help in controlling the number of obesity rate in Malaysia. In this study, the percentage of crystallinity index of banana starch was studied. Experimental design was carried out to study the interaction effects among the parameters on system responses with minimal experimental runs. Three parameters were studied, which are the autoclave time (10 to 60 minutes), addition of palm oil (1 to 10 wt%) and cooling hours (18 to 28 hours) while the responses in this study are crystallinity index (%). Optimisation studies were performed using response surface methodology (RSM). Linear model was chosen for the response and studied using central composite design (CCD). The correlation coefficient, R2 for the linear model of crystallinity index (%) was 0.7544. The interaction effect of parameters were studied using 3D response surface graph and 2D contour plot. The optimum crystallinity index predicted by RSM was found at 47.52% with condition of 10 minutes of autoclave time, 1wt% of addition of palm oil and 18 h of cooling hours at desirability of 0.982. Addition of palm oil has the most significant effect towards the crystallinity index, followed by autoclave time and cooling hours. The structures and crystallinity of the resistant starch sample were characterized using scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy (FTIR-ATR). The starch showed a C-type crystallinity. Investigation of FTIR spectra of starch helps in successive interpretation and characterization of the key bands.