Study On The Rapid Detection Of Water Stability In Aquatic Feed

Water stability is an important quality index of aquatic feed, which exerts direct influence onthe effect and environment of aquatic breeding. However, little research has been done about thedetection of water stability. These existing methods mostly are unscientific, complicated orsubjective, unsuitable for wide use. In this paper, the factors affecting water stability and thediffusion of nutriment in water were discussed, different methods of determining water stabilitywere compared, and a rapid new turbidity detection were established and its application weretested.(1) The influential factors were studied. Single–factor test indicated that water temperature,salt content,water environment and operational conditions have great effects on feed diffusionrate, as well as the time of manual manipulation. Orthogonal test showed that manualmanipulation is the most important factor. with different indexes, the influences of conditionsabove were different. According to the experiment, the maximal diffusion rate occured when thecondition was: weigh of sample:5g, stirring with pumping in 2h, water temperature: 45℃,1000mL non-ionic water. So it's better to crumple.(2) Feed were soaked in water to study its diffusion and dissolution. The result showed that:Feed diffused quickly after being put into water. The diffusion rate was 12.67% in 5 min, and13.38% in 20 min, which is the main part of feed diffusion. Water –soluble nutriments in feeddissolved quickly and completely during the steeping process. For example, content of Cl-descended by 79.77% in 20 min, but content of some water-soluble organic substances such asprotein decreased a little. The prime time to measure water stability is 20min in steeping process.(3) Three existing methods were compared. The result showed: LDM measurement (losspercentage of dry matter)is relatively accurate and reliable and has some practical use, but it needssome time .COD measurement is too complicated. Turbidity is one of new method which can beused widely if the method and condition is improved to some extent .The results from threemethods have good relativity.(4) A rapid turbidity detection of water stability was established. The crumpling machine wasused to accelerate feed scattering;then the relative ratio of turbidity can be tested. The resultsshowed that the relative ratio of turbidity has significant positive correlation with the traditionalmethod(r=0.9902) and better repeatability and accuracy. So it can be regarded as a rapid way tomeasure the water stability of shrimp and crab feed.(5) Applied trials were done on aquatic feeds of different shapes and breeds to study thepractical use of this method. It is not only reliable and feasible, but also rapid, convenient, andsuitable for wide use. It only took 30-40min to detect sample. Through these trials, the crumplingtimes of different feed were made sure :common fish feed:10 min;feed of shrimp and crab:30min;flexible turtle feed:8min;expanded feed:10min. the crumpling process is simple, fast, and easy tocontrol. The reliability studies suggested: relative turbidity has good correlation withLDM(r=0.9867). The repetition studies suggested it has fine repeatability and reliability.