Morphological and Molecular Studies of Banana Starch L.A. Bello-Pérez, 1, * A. De Francisco, 2 E. Agama-Acevedo, 1 F. Gutierrez-Meraz 1 and F.J.L. García-Suarez 1 1 Centro de Desarrollo de Productos Bióticos del IPN. PO Box 24, 62731 Yautepec, Morelos, México 2 Universidad de Santa Catarina, CERES Cereals Lab, Food Science and Technology Dept, UFSC. Florianopolis, SC, Brazil Molecular and morphological characteristics of banana starch were determined by different spectro- scopic techniques. Light and scanning electron microscopy showed the molecular order, shape and size of starch granules. Banana starch granules had a lenticular shape with an average size of 39 m. The X- ray diffraction study showed starch granules with a pattern of a mixture between the A- and B-type polymorphs, also referred to as C-type. The absorbance ratio (1045/1022 cm 1 ) measured by infrared spectroscopy was 1.12, suggesting that the crystalline component was higher than the amorphous regions. Gelatinisation temperature assessed by differential scanning calorimetry was 77.6 °C with a gelatinisation enthalpy of 23.4 J/g. These data stated that banana starch had a high crystallinity level, which might be important in several food applications. Key Words: banana, starch, X-ray diffraction, microscopy, differential scanning calorimetry INTRODUCTION Starch is one of the most important biopolymers. It is a polymeric mixture of essentially linear (amylose) and branched (amylopectin) α-glucans. Starch owes much of its functionality and physical organisation to a granular structure of these macromolecules (French, 1984). It is of great importance to understand the mole- cular and structural characteristics of starches so as to suggest possible applications of these polymers in diverse systems. There are different techniques to elu- cidate these characteristics. These include X-ray dif- fraction (XRD), which measures the long-range order in a sample, i.e. the level of crystallinity. Another tech- nique is Fourier transform infrared (FTIR) spec- troscopy, which can determine the short-range order in a sample obtaining information on the molecular bond vibrations, such as the prominent C—O and C—C stretching vibrations for carbohydrates, yielding both qualitative and quantitative information, such as that on the amorphous and crystalline regions of the starch granule. A destructive technique, such as differential *To whom correspondence should be sent (e-mail: labellop@ipn.mx). Received 3 September 2004; revised 10 January 2005. Food Sci Tech Int 2005; 11(5):367–372 © 2005 Sage Publications ISSN: 1082-0132 DOI: 10.1177/1082013205058409 scanning calorimetry (DSC) has been used to monitor changes occurring upon heating to the bulk of the sample. In the case of native starches, it is possible to obtain a phase transition due to the gelatinisation process which depends on the order and chain length distribution of the amylopectin chain (Yuan et al., 1993). The current tendency is to look for alternative sources for obtaining starch with better physicochemi- cal and functional characteristics. In recent years, sub- stantial progress has been made in obtaining starches from these sources, and study into their functional and physicochemical properties have also been made (Hoover, 2001). Bananas are grown extensively in tropical and subtropical regions and are an important food crop. Although the composition of banana fruit has been carried out on starch (Kayisu et al., 1981; Lii et al., 1982) there are no studies about its molecular characteristics. Banana is a climacteric fruit and in Mexico it is consumed when the fruit is ripe, for this reason many fruits are lost during commercialisation due to inefficient postharvest handling. Starch is the principal component of green bananas and this polysaccharide undergoes important changes during ripening (Lii et al., 1982). Unripe banana starch is very resistant to digestion in rats and men. Faisant et al. (1995a, 1995b) studied the digestibility of banana starch granules in the human small intestine and reported the starch breakdown and also the structural features of resistant starch (RS). However, there are no reports describing the molecular characteristics of banana starch. Therefore, it was the aim of the authors