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Phosphates in Seafood: Proper usage levels and analytical methods for evaluating usage

Posted by Gillian Dagan on Thu, Sep, 26, 2013 @ 17:09 PM

Phosphates in shrimp and seafoodIn a previous post I discussed how phosphates are used as moisture retention agents in seafood, some terms associated with phosphated products, and how phosphates are properly used and abused in the food industry.  In this post I would like to delve more deeply into suggested usage levels and how we test products for phosphate usage.

The overall recommendation for phosphate usage in seafood products is "more is not better."  Although a number of phosphate and phosphate blends exist, the recommended applications on shrimp based on product performance and consumer acceptability are below, cited from The Global Aquaculture Advocate, Phosphates and Shrimp, 2002, article by Laura Garrido and Steve Otwell, Ph.D., University of Florida.



Target Uptake

Peeled Shrimp, peeled and deveined shrimp

Soak in 2-4% phosphate 20 min to 2 hours at <4C


Peeled shrimp for value-added products (i.e. butterfly)

Soak in 2-4% phosphate 10-25 min <4C


One of the most common questions we are asked as food testing experts is, "Has this product been treated [with phosphates]?"  Believe it to not, this is not a straight forward question to answer.  Because of the number of different phosphates used in the food industry (sodium tripolyphosphate, hexametaphosphate, etc) each and every possible variant of phosphates would need to be quantified. 

Rather than guessing at what compounds may or many not have been used in processing, we answer this question by quantifying total phosphorus in the sample and performing a moisture analysis.  These values are then compared to industry standards for the type of seafood in question and trained food scientists then decide whether or not the product was treated and if the product was over-soaked.  (For a review of terms associated with phosphating agents please see part 1 here.)

For some types of seafood, shrimp especially, a significant amount of research has been done on the effect of phosphating agents total phosphorus levels and moisture values.  When testing shrimp for phosphating agents, we compare total phosphorus levels and moisture values to industry standards, first published by the extensive seafood research group in the Food Science and Human Nutrition Department at the University of Florida.  (Go Gators!)  Depending on whether or not the shrimp is shell on or off, different values exist for total phosphate and moisture, however in both cases we can tell with great certainty if the shrimp has been phosphated and whether or not the level of phosphating agent used was appropriate. 

In other seafood, the comparison of phosphorus level, moisture value, and industry standards doesn't exist.  In these cases we can use 2 different approaches to evaluating the product.  If we can get a sample of the same type of seafood that we know has not been phosphated, we can do a direct comparison between the known and unknown samples. We will look for an elevated phosphorus and moisture value to indicate treatment with phosphates and our food scientists use their experience to evaluate the extent of the increase to determine whether or not the product was over-soaked.

In most cases, however, a comparable non-phosphated sample is not available.  In this case we compare phosphorus and moisture values with reputable databases like the USDA Nutrient Database here and our extensive collection of seafood data collected over years as food testing experts.  In most cases, the comparison is straightforward and results in an easy judgment call for an experienced food scientist. 

In the cases where the values are only slightly different, or there is no historical data available for a specific type of seafood, our food testing experts have one last trick up their sleeves---the cooking performance test.  I'll discuss cooking performance tests, non-phosphate moisture retention agents, and avoiding over-soaked product  in part 3 of this series on Phosphates in Seafood.

Topics: seafood safety, gillian dagan, seafood testing, phosphates in seafood, shrimp

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