Preventing Spoilage of Raw Rice Bran Used As a Feedstuff
Heat Treatment
The heating device consists of two heated tubes, each of which has a screw conveyor running through it (Fig. 1). The tubes are connected in a series, so that bran which has passed through the first tube then enters the second tube. The second tube is connected to a "cyclone" at one end (a rotation air blower cooling system). At the other end of the equipment is an engine which produces steam to heat the bran (Fig. 1 and Fig. 2). The bran is heated while it is moving through the tubes, propelled by the screw conveyors. The heated bran is then cooled by the cyclone after it exits from the second heating tube.
The heating tubes are designed so that the steam can be fed, not only to the outer cylinders, but also to the screw shaft. Therefore, all metallic surfaces in contact with the bran are able to transfer heat to the bran (Fig. 3 Patent Pending).
The heating device needs steam at a pressure of 3 kg/cm2 (138?) to 4 kg/cm2 (148?). If the feed rate of bran is 1.5 to 2.5 kg/min (90 to 150 kg/h), the temperature of the bran reaches 90 - 93? at the outlet of the second heating tube. The water content of the bran then falls to around 8% after the bran has passed through the cyclone. As a result, the activity of the lipase (fat) drops to about half of that of raw rice bran (Table 1).
Storage Life of Treated Bran
The acid value (AV) of the heat-treated bran stored for 8 weeks at 35? was less than 50. In contrast, the AV of the bran of raw rice was 121. This indicates that the heat treatment is nearly as effective as preservation by freezing in preventing deterioration of the bran over time. (Table 1). The components of the heat-treated bran are the same as those of raw rice bran.
Heat-treated bran can be stored at normal temperatures without any deterioration in quality. The cost of the heat treatment is aroundUS$45/mt, assuming that 90 mt of bran are treated in a year.
Some Important Points
- Rice bran is readily available locally in most parts of Asia. The treated bran can be used as a feed for livestock even in summer i.e. nearly one year after the rice harvest.
- Further study is needed on the proper treatment of bran in rice screenings, and from rice used to brew "sake" (rice wine).
Index of Images
Figure 1 Apparatus Seen from the End
Figure 2 Side View of Apparatus
Figure 3 Part of Screw
Table 1 Effect and Preservability of Heat Treatment with a Bran Heating Device Designed for Practical Use
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