Caracterização de konjac em pó e elaboração de gel

Abstract

The tuber Amorphophallus Koch Konjac is still not well known in Brazil, but well utilized by the oriental people for the preparation of a firm and soft gel. Its also very appreciated because it contains a polysaccharide known as Glucomannan with high water holding capacity and considered as a dietary fiber. Because of its high water activity, the shelf life of the tuber and the gel is limited, which affects its commercialization. The tubers dehydration for the formation of a powder allows the extension of its shelf life and obtain a more practical product for its consumption. The objective of this work was to dehydrate the konjac tubers to obtain a powder, characterize it and elaborate a gel with it. The proximal composition of the tuber and powder, its water activity, as well as the water activity, color, fibers and texture of gels were determined. The proximal composition of the gels showed that the tubers humidity was 82,37%, whereas for the powder, 9,53%, which demonstrates the efficiency of the dehydration process. This is also confirmed by the low water activity of the powder which was 0.483 against 1.000 of the tuber, probably due to its low water retention capacity. There are considerable differences on the values of the chemical composition of the tubers and powder, which can be due to the dehydration. Moreover, there is a great difference according with species for the chemical composition of the konjac tubers, especially for protein composition. The chemical composition of ash, proteins, lipids and carbohydrates were 1,32%, 2,09% 3,63% and 10,59%, respectively for the tuber, and 6,23%, 8,83%, 0,98% and 74,43% for the powder. Gels fiber content was expressive, showing values of insoluble fibers of 73.41% and 3.43 % of dietary fibers. Texture analysis showed that the gel obtained with the powder had similar properties as the gels obtained by tubers. The drying process allowed the formation of a powder with low water activity, which favors its storage at ambient temperatures, compared to the natural tuber. By the drying conditions of konjac tubers used in this work, it was possible to obtain a powder which could be used to elaborate a gel with similar properties to the gel of the natural tuber, that contains considerable amounts of fibers, and it’s an interesting food for those who follow a healthy diet.