Umidade inicial dos grãos e parâmetros hidrotérmicos sobre a água de encharcamento e o desempenho industrial do arroz na parboilização

Abstract

The operational difficulties at the time of the harvesting, due to the production seasonality, the product’s wastefulness and the bad distribution of the harvested quantity with a broad moisture line in a short term, make difficult the drying process and the storage of the rice, making the industries, in the harvest, subject part of the grains to parboilization operations without previous drying and storage; although it does not have enough technical basis to a sure decision making in this aspect. In this paper, it was studied the influence of the initial humidity of the hydrothermal grains and parameters in the operation of soaking about the industrial performance of the parboilized rice and about the water characteristics used in the hydration. It has been used grains of rice, long fine class, Supreme I cultivar, harvested with about 21% of moisture, cleaned in air machine and sieve, being put in groups in the moisture lines of 20 ± 0,5%, 18 ± 0,5%, 16 ± 0,5% and 13 ± 0,5% and subjected to the soaking at 60, 65 and 70 o C for 6 hours. In each 30 minutes, it has been collected samples, being evaluated the humidity degree to determine the hydrothermal behavior, followed by an immediate autoclaving at 110 o C, 0,45Kgf.cm -2 for 10 minutes, making the drying with heated air at 45 ± 5 o C. The variables studied were subdivided in two groups: a) analysis of the soaking water (total solids; total dissolved solids; pH and cloudiness); b) industrial performance (husk opening rate, entire grains income; defects incidence; non-gelatinized grains percentage). It is concluded that: a) the initial humidity of the grains interferes more in the hydration time and in the defects incidence, while the temperature of the water and the soaking time interfere more in incomes of the entire grains and of the entire without defects; b) the parboilization of the rice without previous drying allows reductions of 30 to 60 minutes in the soaking done in the same temperature used to dried grains at 13% of moisture; c) the initial humidity of the grains in the parboilization process does not interfere in the lixiviation of the total solids and the total dissolved solids, or in the variations of cloudiness and the water’s pH during the soaking; d) the raising of the temperature and of the time of the soaking provides an increasing in the content of the total solids, of total dissolved solids and in the cloudiness, with reduction in the water’s pH values during the soaking; e) in the process of parboilization, raisings of time and temperature in the soaking provide increasing in the husk opening rate, provoking deforming in the rice grains; f) to the Supreme I cultivar, the combination of temperature and time of soaking that allows a better potential of industrial performance occurs in operations the 65 o C for 5 hours and 30 minutes the 6 hours.