Variação na composição química em grãos de arroz submetidos a diferentes beneficiamentos

Abstract

Rice is a good source of energy in diets, consumed by 2/3 of the global population. In spite of it, this cereal is classified based on industrial and commercial parameters, not considering its nutritional value, which is the most important parameter needed to compose a balanced diet. Previous research has shown the existence of factors that can affect the composition and nutritional value of this grain, such as phenotypic variation and processing. Based on these facts, the objectives of this research were to determinate the chemical composition of different white rice cultivars, in order to categorize them, according to the nutritional value, into groups with distinct nutritional characteristics and verify differences in chemical composition when the cultivars are submitted to different processes. To attain these objectives, were determinate the content of mineral matter, crude fat, crude protein, digestible and resistant starch, total, insoluble and soluble fiber, amylose and minerals (Mg, K, P, Na, Fe, Mn, Zn) of nine rice cultivars indicated to production in the South region of Brazil, processed to obtain brown, parboiled and white rice. The obtained results show differences in chemical composition among cultivars what made possible to categorize them according to values of digestible starch, crude protein, insoluble and soluble fiber, considered important nutrients to evaluate nutritional value of rice. The groups formed were significantly different and some characteristics were persistent between cultivated years. This results, although they are preliminary; show that rice can be explored in different ways in nutrition, according to genetic variability and not just as a unique food with no variability. In the same way, the processes also greatly influenced the nutrient content, fact that can be used to optimize the use of this cereal in human nutrition. Brown rice showed higher values for some nutrients (crude fat, insoluble fiber) and minerals (Mg, K, P, Na, Mn, Zn). In spite of it, these results are not indicative of nutritional superiority, because antinutritional factors that exist in the grain outer layers, can influence absorption and utilization of mineral as also decrease proteins and energy digestibility. In the other hand, this rice can be a good source of fiber, which is an important nutrient to treat constipations, hipercolesterolemia and diabetes. Parboiled rice showed higher mineral content (K e P) then white, opening possibilities to indicate it to people who are in nutritional risk of micronutrients deficiency. In the same way that genetic variability, the results obtained to process influence showed that rice from different processes can also be used in specific diets according to individual needs