Determination of the Molecular and Structural Characteristics of Okenia, Mango, and Banana Starches

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Abstract
Starches were isolated from nonconventional sources (banana, mango, and okenia) and their characteristics were examined using polarized light microscopy, X-ray diffraction pattern, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). Banana starch granules were of an ellipsoidal shape with size between ∼8 and 20 μm; okenia had the smallest granule size, between ∼2 and 5 μm. The three starches showed the Maltese cross, indicative of an intact granule structure. Okenia and mango starches had the A-type X-ray diffraction pattern, common to native cereal starches, whereas banana starch showed a mixture between A- and B-type pattern. Banana starch had the highest temperature (77.6 °C) and enthalpy (23.4 J/g) of gelatinization in excess water conditions; okenia had the lowest temperature (71.2 °C) and enthalpy (15 J/g), which may be related to the X-ray diffraction pattern and its small granule size. Both the okenia and mango starches had a higher molar mass and gyration radius than banana starch, which may be related to the differences determined in their crystalline structures. Keywords: Starch; molar mass; light microscopy; X-ray diffraction; infrared spectroscopy; differential scanning calorimetry