The physicochemical properties of banana starches

Abstract

The main objective of this study was to establish the physicochemical properties of native banana starches with particular reference to key granular and molecular characteristics. The design was targeted to provide for a comparison of landrace cultivar varieties (AAA-EA) with three hybrid varieties with particular reference to Gonja (AAB), Musa Kayinja (ABB) and Sukhali Ndizi (AB). Starch samples extracted from the study samples using a modified sedimentation technique. All banana starches were established to be of exceptional high purity. The determined characteristics included: amylose content using an amperometric technique, crystallinity and crystal type using X-ray diffraction characterisation, granular size using a laser beam technique, gelatination endotherms using differential scanning calorimetry (DSC) and pasting viscosity using brabender viscomaygraph.

The amylose content ranged between 8 – 21%. The X-ray diffraction measurements showed difference in the crystallite structure and although the crystallinity was unusually high for B*crystals, all the banana starches conformed to the latter crystallype. The starch grainule shape ranged between 6 -60µm in size. The DSC results showed the range for the maximum endotherm temperature (70.4 -72.8°C). The results also indicated a relationship between molecular composition and unique cooked characteristics of the AAA-EA varieties while the high endotherm values and broad ranges concurred with the level of crystallinity obtained. The Brabender cycle curves were characterised by a two stage- swelling phenomenon, very high peak viscosities (1780 -1910 VE), low cook stability and extremely high setback (2080 -2940 VE). The physicochemical properties helped to explain the extensive shelf life of banana flours besides, rendering the banana starches potentially useful in a wide range of application in the food industry.