NMR and X-Ray Studies of Starches Derived from Tropical Fruit Seed Gelatinization Process

Abstract

Gelatinization of the starch obtained from fruit seed such as mango and cumbaru was investigated applying an analytic methodology developed in the polymer nuclear magnetic resonance (NMR) laboratory at IMA/UFRJ, employing high resolution nuclear magnetic resonance spectroscopy in the solid state for hydrogen nucleus, using 1H HR-MAS pulse sequence. The results showed that NMR can be used instead of some techniques normally applied to study the gelatinization process, because 1H HR-MAS and relaxation time allow the evaluation of this process at the molecular level. NMR was also able to indicate the best gelatinization conditions. To start this study the glass transition (Tg) determination was a first step, because the Tg of seed starches are different than the Tg of starches derived from cereal, for example. The 1H HR-MAS NMR showed some useful information on the fruit seed starches gelatinization process. X-ray measurements were also used to support the data obtained from NMR technique. It was verified, from X-ray, that mango starch exhibits crystallinity in the A form and cumbaru showed a predominant amorphous phase. The use of 1H HR-MAS was shown to be a new, powerful method to follow the gelatinization process, because this process can be understood at the molecular level.