Layse do Prado Cordoba

Brazilian Dioscoreaceas starches

Abstract Determination of the characteristics of native starches is crucial in order to select their best application in various industrial fields. Thus, two different types of non-traditional native starches from the Dioscoreaceas species (Dioscorea sp. and Dioscorea piperifolia Humb. var. Wild) were studied regarding their thermal, structural and rheological properties. The results were contrasted with traditional commercial starch sources (potato, cassava and corn). From the thermogravimetric results (TG/DTG), D. piperifolia starch obtained the highest thermal stability of the samples, except for potato starch. Furthermore, using differential scanning calorimetry and viscoamylograph profiles (RVA), it was found that the Dioscoreaceas starches presented a higher onset (To) temperature and susceptibility to retrogradation. They also showed lower values in relation to relative crystallinity, which was calculated from their X-ray patterns and tendency to white (L*) colour. The shapes of the Discoreaceas starch granules were determined using electron microscopy; it was found that as the potato starch the Dioscoreaceas starches showed a wide range of particle size.

Brazilian green banana

Banana is a fruit largely consumed in the world. Unripe banana contains a great quantity of starch, which is in majority the resistant starch type. This biopolymer has several health benefits, and it can be applied in food products and biofilms. The starch properties can vary according to its botanical origin. The aim of this study was to investigate the green banana starch structure obtained from three fruits of two genotypes of genomic groups of banana: Terra Plátano (AAB), Caturra Cavendish (AAA) and Prata Anã (AAB). The samples were studied for resistant starch content using differential scanning calorimetry (DSC), thermogravimetric analysis, viscosity analysis (RVA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy. By the DSC analysis, it was observed that the gelatinization phenomenon occurred at lower temperatures for Caturra Cavendish (AAA) and Prata Anã (AAB) in comparison with Terra Plátano (AAB). Thermogravimetric curves showed three mass losses to Terra Plátano (AAB) and four losses for Caturra Cavendish (AAA) and Prata Anã (AAB). By RVA it was observed that the starch from Terra Plátano (AAB) showed higher viscosity and retrogradation. The XRD indicated that the Caturra Cavendish (AAA) and Prata Anã (AAB) presented the C-type profile and the Terra Plátano (AAB) exhibited profile B-type and significantly higher relative crystallinity. SEM analysis and optical microscopy revealed that the granules have ellipsoidal and flattened shape. Considering the thermal and rheological characteristics presented, the use of banana starch in biofilms production and in food exposed to a cooking process is suggested.