Effect of Processing on Structure and Morphology of Amaranth Starch

ABSTRACT The structure of Raw and Processed Amaranth Grains starch was studied by using Scanning Electron Microscopy (SEM). In this study, starch morphological differences were observed between raw and processed (Boiled, Roasted and popped) grains derived from the same cultivar. Among food carbohydrates, starch occupies a unique position. It is the major carbohydrate storage material in many higher plants and is considered the second largest natural biopolymer next to cellulose. Starch contributes to the physicochemical properties of food products made from cereals, tubers, roots, legumes, and fruits. It is the basic source of energy for the majority of the world's population. In human nutrition, starch plays a major part in supplying the metabolic energy that enables the body to perform its different functions. In this study SEM revealed that starch granules of grains were much smaller in size that many of them were not separated from amyloplasts. Cooked grains have wider, more defined cracks, suggesting that they serve as channels for water migration into the grain during cooking. Water penetrates unequally into the grain during cooking, low water penetration produces dense regions with minimal starch gelatinization, and high water penetration produces large voided areas. The voids occur in the transverse orientation of the grain and are the main of cause grain expansion during cooking than the other processing such as roasting and popping. But the structural changes at micro and nano-scales can be dramatic, as revealed by scanning electron microscopy. Especially when water traces are present, a very rich network of polymer chains can be observed, remaining after the granule structure collapses. This is considered a suitable structural basis for different new products were interactions could be modeled, such as carriers for nutritional interesting substances