Relações granulométricas no processo de brunimento de arroz Granulometry relationship in the rice milling process

O brunimento é uma das etapas de beneficiamento do arroz que tem grande importância sobre o rendimento de engenho. Neste trabalho, analisaram-se relações granulométricas de frações de grãos na massa de arroz e seus efeitos sobre o rendimento de engenho, durante o processo de brunimento. As amostras usadas foram 78 g de arroz descascado, tendo essas partido de amostras originais de 100 g. Foram testadas cinco relações de composição de amostras a serem brunidas, variando as quantidades de grãos quebrados e de quirera que acompanhavam a massa de grãos inteiros, que foram: 1) somente grãos inteiros; 2) 6,16 g de quebrados e 1,04 g de quirera, conforme amostra original; 3) 3,60 g de quebrados e 3,60 g de quirera adicionados aos inteiros; 4) 7,20 g de quebrados adicionados aos inteiros, e 5) 7,20 g de quirera adicionada aos inteiros. Os procedimentos foram executados com uso de engenho de provas e com classificação manual. O rendimento de engenho foi significativamente superior, após a operação de brunimento de arroz, quando existem, na massa a ser brunida, grãos quebrados e quirera, variando entre 3,60 g a 7,20 g e 1,04 g a 7,20 g, respectivamente, comparada ao brunimento da massa composta por 100% de grãos inteiros.
Milling yield using five different rates of broken and head rice was tested. The samples were arranged to have different amounts of big and small broken kernels in the mass of grains. The size of each fraction of broken grains was established according to the Brazilian Rules of Rice Classification. The paddy sample had 100 g and the brown rice sample had 78 g. The brown rice was milled by adding different proportions of broken kernels to make five treatments as follows: 1) only whole kernels; 2) 6.16 g of big broken kernels and 1.04 g of small broken kernels were used as they appear in the original lot; 3) 3.6 g of big broken kernels and 3.6 g of small broken kernels were added to the whole kernels; 4) 7.2 g of big broken kernels were added to the whole kernels and 5) 7.2 g of small broken kernels were added to the whole kernels. A laboratory mill was used. The classification was made manually. The percentages of broken kernels varied from 3.6% to 7.2% in the fraction of big broken kernels and from 1.04% to 7.2% in the fraction of small broken kernels, respectively. The results showed that, in the milling process using broken kernels in the mass, the head rice yield was significantly higher than when 100% of head kernels were milled.