Determination Of Polyphosphates In Aquatic Products By Ion Chromatography And Basic Study On Non-Phosphate Additive

Polyphosphates as a kind of important water-holding additive were widely applied to the processing of aquatic products. However, polyphosphates can be hydro lydzed after being added to the muscle, which brings about weaking its functionality and the difficult of detection. In this paper, we aimed at solving problems about detection of polyphosphates in seafood and easy hydrolysis. So we established a method of detecting polyphosphates in aquatic products, and used UHP to make polyphosphatase inactivate in order to block hydrolysis of polyphosphates in pre-treatement, especially grinding and weighing sample process, so that we could avoid the false negative results. In addition, in order to better control the problem of excessive polyphosphates, we not only established the effective detection method, but also did some initial research on non-phosphophate water-holding additive. Specific results are as follows:1,An reagent-free ion chromatography method was established for detection of orthophosphate, pyrophosphate, tripolyphosphate and three metaphosphate, and we used Dionex ICS-1500, AS11-HC anion exchange column, elution with KOH gradient program and suppressed conductivity detector to do qualitative and quantitative analysis. The method was linear for phophates concentration raging from 0.1 mg/L to 100 mg/L, all the correlation coefficents were over 0.999, and the average recoveries from 95% to 103% in shrimp, it was satisfying the need of detection. The method was applied for 19 kinds of seafood and their products that came from different markets, we detected the content of polyphosphates and evaluated their safety.2,Polyphosphates were stable in water at 25℃, their concentration had no significant change within four hours. However, when added polyphosphate into minced shrimp, though the content of three metaphosphate had no significant change within fours hours, the content of pyrophosphate and tripolyphosphate gradually decreased as time prolonging, especially their content sharply decreased in half an hour. The content of pyrophosphate and tripolyphosphate in frozen shrimp sharply declined in the initial storage time, sequentially they were stable, their content had no obvious change. Additionally, the frozen temperature lower their contents higher. Three metaphosphates was more stable during frozen storage time. In addition, UHP made hydrolysis enzyme inactivate, so it could inhibit the hydrolysis of pyrophosphate and tripolyphosphate in shrimp. Especially when UHP was up to 400 MPa,10 min, their stability was the best.3,The results indicated that shrimps were soaked in solution of 55 mPa-s 1%(w/w) the alginate oligosaccharides whose comprehensively water-holding capacity was the best among deionized water, trehalose, sodium alginate and alginate oligosaccharides (15 mPa-s) and whose weight increasing yield was up to 11.7% which was significantly higher than 3% compound phosphate whose was 6.2%(p<0.05), and its drip loss yield was sharply lower than shrimps dealt with compound phosphate (p<0.05), although the loss yield was higher than compound phosphate, it was still lower than other groups, and there were no obvious difference in cooking yields. We chose the better concentration ranging from 0.5% to 1.0% and soaking time ranging from 1 h to 2 h. The LF-NMR results showed that the bound water content and quasi-bound water content in muscle of shrimp soaked in the alginate oligosaccharides (55 mPa-s) solution increased, while bound water content of shrimps marinated in phosphate compound solution mainly increased in muscle. Shrimps which were marinated in the alginate oligosaccharides (55 mPa·s) whose myofibrils were wrapped by a layer on the surface and whose internal structure was no significant change, however, which were marinated in compound phosphate solution whose myofibrils took on lateral expansion, A band became narrower, I band became wider. The structure of Z disk became weak, maybe there were many small myofibril fragmentations. The size of the gap of frozen shrimp marinated in different marinades raging from big area to small area was compound phosphate, deionzied water, without marinating, alginate oligosaccharides (55 mPa·s), fresh sample, respectively, which was in conformity with the principle of drip loss yield changing. The profile of myofibrillar proteins SDS-PAGE had no significant difference after frozen shrimp marinated different marinades, which indicated that myosin heavy chain and actin had no significant changes under the experimental conditions.