Methods used to determination thes constituents of the fibrous fraction, a review

The estimation of the chemical-bromatological composition of foods involves a series of studies that mainly evaluate the fibrous fraction, since it presents great variability when compared to the other components. The growing number of publications on the analytical techniques available for determining the nutritional value of food end up generalizing the use of poorly defined terms. There are several techniques for evaluating forage components, the detergent system being the most used, although there are more modern methods. However, the accessibility and cost of these modern methods are factors that limit their use in various laboratories. Moreover, some of these methods are not recognized as an official method of analysis. In this context, the objectives of this review were: to highlight the most important concepts in determining the nutritional value of foods; improve the use and difficulties of interpretation of analytical results. It was concluded that the use of analytical methods allows to estimate the composition and availability of different fractions of the cell wall. But variability of cell wall constituents requires knowledge of the different analytical methodologies available. Analytical methods, traditional or alternative, are still empirical as they present different results for the same analysis. These variations are mostly generated by the differences between the steps of the analytical procedures. It is clear that the improvement of analytical methods is extremely important for estimating the nutritional value of foods. A estimativa da composição quimíco-bromatológica dos alimentos envolve uma série de estudos que avaliam principalmente a fração fibrosa, uma vez que apresenta grande variabilidade quando comparada aos demais componentes. O crescente número de publicações sobre as técnicas analíticas disponiveís para a determinação do valor nutritivo dos alimentos acabam generalizando o uso de termos mal definidos. Existem diversas técnicas de avaliação dos componentes da forragem, sendo o sistema de detergente o mais utilizado, embora existam métodos mais modernos. Contudo, a acessibilidade e os custos destes métodos modermos são fatores que limitam o uso dos mesmos em diversos laboratórios. Ademais, alguns destes métodos não são reconhecidos como método oficial de análise. Nexte contexto, os objetivos desta revisão foram: evidenciar os conceitos mais importantes na determinação do valor nutrivo dos alimentos; melhorar o uso e as dificuld