6.1.
Definition 6.2.
How is it formed 6.3.
Processing blood water 6.1.
Definition 6.2.
How is it formed 6.3.
Processing blood water Blood water is defined as the liquid material that separates from the fish during storage.
In experiments with cod, redfish and herring stored at different temperatures for different lengths of time it was found that: at 10 centigrades cod stored for 0 to 17 days showed weight losses equal to 10% after 3 days, redfish 3-7% after 3 days, and herring 5-6% after 3 days. At 25 centigrades the cod lost 11% after 3 days, the redfish 6% and the herring 12-18%.
In another experiment, 4 tons of fish offal (trimmings) were stored in a hopper and allowed to drain over a period of time. All the liquid was collected, weighed and analyzed. The results indicated that after 24 hours of storage, 5% of the weight of the raw material was lost.
Studies with cod and herring stored at different temperatures over a period of time showed that the daily loss in weight of the fish doubled for each 5 centigrades rise in temperature.
A Norwegian study reported that the bloodwater contains about 10-15% of fat free dry solids in stored capelin.
German studies put the loss at about 3.6% of the raw material, while Danish calculations indicated that the annual loss of weight in the blood water was almost equal to the average monthly catch of fish. Polish researchers reported that the blood water ranges from 10-15% of the original weight of the fish. To improve the yields of meal and maintain quality, it is essential to process the blood water at the same time that the fish are being processed. The best solution is to avoid as far as possible the formation of the blood water, by having suitable storage conditions and adequate processing capacity. The drainage of blood water to waste, in any event must be prevented for reasons of hygiene, since it results in great contamination of streams or harbors. In
Figure 39 we have calculated the amount of fishmeal that is being lost if blood water is not recovered. We have done this for each of the ports in Peru, making the assumption that 20 kg/ton of fish is being lost in the bloodwater (equivalent to 2% of the catch, a very low estimation).Blood water is a mixture of suspended, and dissolved solids plus oil that is released from the fish in storage. There are three options for handling this fraction; discharge overboard, meter back to the cooker for processing with the fish or processing by coagulation of the proteins, separation of the oil and solids and evaporation of the water phase.
Figure 40 shows the two alternative treatments for the blood water.Comentarios al Webmaster |
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