Sensory judgment of the quality of pellet feed for fish

With the rise of intensive aquaculture, the use of fish pellet feed has been very common. But at present, there are many feed brands on the market. There are also great differences in quality and grade. Some farmers may feel at a loss about this and can only choose according to the advertising of the manufacturer or the evaluation of a certain feed by their peers, or even try it by constantly changing different brands of feed, and so on. to some extent, these practices have a certain degree of blindness. A simple method for judging the quality of fish pellet feed by using senses summed up in practical experience is recommended, which can be summarized as one look, two smells, three twists, four bubbles and five chews. For your reference.

First, look at the color, the grain size, the luster and the speed of submerged water. Fish feed is granulated by mixing several main raw materials such as fish meal, soybean meal, cottonseed meal, rapeseed meal and secondary meal according to a certain proportion. The color of the raw material can be shown in the finished feed to a certain extent. For example, the feed color is slightly yellow when the content of fishmeal and soybean meal is high; when the content of miscellaneous meal (cotton meal, rapeseed meal and other low-quality meal) is more, the material color is black and red; when the secondary powder content is more, the material color is slightly white, and so on. The amount of some raw materials can be judged by observing the feed color.

The high-quality fishing material should be of uniform grain size, with a neat cross-section, a particle length of about 1.5-2 times the diameter, and a pulverization rate not exceeding 1%. If we see the coarse grain size and uneven cross section of fish, it may be caused by the following reasons: the fineness of ① raw material is not enough; the formula of ② raw material is not reasonable; the quenching and tempering process of ③ is uneven; the improper matching of ④ cutter and ring die, etc. This kind of fish has a certain effect on palatability and digestibility.

The surface of the particles of high quality fish is smooth, uniform and shiny. The surface of inferior feed is rough and has no gloss. The reasons for poor glossiness may be insufficient crushing fineness of ① raw materials, insufficient compression ratio in ② granulation process, insufficient addition of oil in ③ feed, and so on.

After entering the water, the granular fish is generally swallowed by fish in the water surface layer. Therefore, it is required that the feed must have a certain buoyancy and should not settle too fast.

Second, smell. Pellet feed is a kind of ripening material after steam quenching and tempering of mixed raw materials, and high-quality feed emits a maturing flavor. If moldy flavor, scorched flavor, synthetic fishy flavor, flour flavor, raw fish powder flavor or other peculiar smell are found, it shows that there are some problems in raw material quality, feed processing or feed storage. Attention should be paid to it.

Third, twist. Fish material is scattered in the water for fish feeding, which objectively requires that it must have a certain mechanical hardness so that it will not disperse as soon as it enters the water. In general, twist it a few times by hand without breaking it. A twist and crushing shows that the feed hardness is not enough, the pulverization rate is high in transportation, and the feed is easy to be dispersed into the water, resulting in feed waste.

Fourth, bubble. Throw the fish into a water container and soak it. On the one hand, you can test the stability and settling speed of the feed in the water. On the other hand, we can observe the general composition of the raw material after the feed is opened. The stable time of high-quality feed in water is 3-5 minutes.

Fifth, chew. Put the pellet feed in the mouth and chew it through your own sense of taste and touch, you can feel whether the feed has gone bad, whether there is a peculiar smell, and whether it contains impurities.