Desenvolvimento de um processo de moagem de sorgo (sorghum bicolor, L., Moench) e de produção de farinhas pre-gelatinizadas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1984

RESUMO

Sorghum (Sorghum bicolor L. Moench) is the cereal with the greatest production of energy per hectar for arid and semi - arid tropical areas, but its consumption has been limited by a lack of technology for the development of products. The present investigation was undertaken with the aim of obtaining sorghum flour using the milling system traditionally used for other cereals and preparing pre-gelatinized flours with physical and chemical properties appropriate for human consumption and industrial use. The milling process was effected with a roller mill. The grain was conditioned to 14, 15, 16 and 17% humidity, but the flour yield was greatest with non-conditioned grain (12.87% moisture). The flours showed ash contents of 0.85 - 0.96% and lipids of 1.14-1.22%, making it necessary to polish the grain. This process also made possible greater separation germ. The polishing was effected in a rice polisher (using abrasion) for both conditioned and non-conditioned grains. The greatest yield was again obtained with the non-conditioned grain (92%). Grain that had been polished and milled in a roller mill produced a yield of 80%. The ash and lipid contents were 0.53 and 0.36% respectively. For the production of pre-gelatinized sorghum flour using a hydrothermal process, the polished grains were soaked in water at temperatures of 27, 40 and 60º C for periods of 90, 45 and 40 minutes, respectively. The hydrated grains were then treated with steam at 113º C for 1, 5, 10 or 15 minutes, dried in an oven at 45ºC to approximately 10% moisture, and then miiled to a size of less than 200 um. In the pre-gelatinized flours, all viscosity characteristics decreased as time of thermal treatment increased. The water absorption index increased as the soaking temperature and thermal treatment time increased; the index of solubility in water was only slightly affected by the hydrothermal treatment. It was concluded that, for all soaking conditions tested, one minute of steam treatment was adequate to produce modifications in the starch granule structure and to obtain a pre -gelatinized flour. For the production of pre-gelatinized sorghum flour by extrusion, the flour was extruded with 15.0, 17.5, 20.5, and 22.5% moisture at 160, 180 and 200ºC using a compression ratio of 1:4 and a 3 mm die. The effects of the extrusion conditions on the extruded product and the characteristics of the flour produced were evaluated using response surface methodology with a second order model. The torque developed was greater for the lowest moisture level (15%) and increased as temperature decreased. All conditions studied produced expansion. The density was lower for products obtained from flours with inicial moisture of 17 and 20% extruded and temperatures about 180º C. Initial viscosity, viscosity at 95% and viscosity in the cooling cycle at 50º increased when the extrusion temperature increased. The water absorption index increased from 7 to 12, and the index of solubility in water increased up to 27.8%. During the extrusion process and hydrothermal treatment, there was a decrease in the content of certain essencial amino acids and vitamins, although the digestibility increased. It was shown that, with conventional milling equipment and all of the processes studied, it is possible to obtain pre-gelatinized flours with properties suitable for use in the production of instant food and in industry.

ASSUNTO(S)

farinhas sorgo cereais

ACESSO AO ARTIGO

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