Understanding prawns: buying tips for chefs

Prawns are as common on a chef's table as they are difficult to buy well in bulk. So we asked our producer GEM Seafood for their top tips for professional kitchens, helping you to know what's what when it comes to buying prawns.

What is the most common type of prawn chefs ask you for?

That would be the Raw Peeled & Deveined. The most common grade for big prawns is 8/12. The 16/20 grade is most common when buying mid sized prawns from wholesalers, and 26/30 from retailers.

Grades can be quite daunting when buying prawns: they show how many prawns will be found in a pound, the higher the number the smaller the prawns. Beware though: this system works only for head-off prawns. If they are head-on, then the count is per kilo rather than per pound.


How does IQF work?

With Individual Quick Freezing (IQF) the product goes through a freezing belt. It will first pass through a freezing tunnel and then through either a dip glaze system or spray glaze system. One pass will normally give a 10% glaze. More passes, the higher the glaze level.

A 30% glaze is the most popular in today's market but a 10% glaze is perfectly adequate to protect the quality of the prawn. We see that prawns with a lower percentage of glaze are a smarter buy because you get more product (and less ice) for your money and you spend less time defrosting it.

The alternative to IQF is freezing blocks. This is done with cheaper machinery and is less labour intensive hence prices are probably lower than IQF, but you get a lot of unnecessary ice around the product.

If IQF is so convenient, why do chefs buy prawns in blocks?

Block format is popular only with Asiatic customers. This is more of a buying habit set in time than a real business decision. In our opinion, IQF is better for controlling usage because IQF prawns can be defrosted in smaller portions depending on what is needed on the day. They just go in a sink with tap water for a few minutes, while blocks take over an hour to defrost — that is if EU standards for defrosting are properly followed.

Are there significant price fluctuations throughout the year?

Prices are higher in January and outside the season periods of April/ May and October/November.

The weather is a very big factor: the product is mostly farmed but the conditions still need to be perfect for the growth cycles so harvest does not take place at the hottest and coldest temperatures.

Demand from markets such as the US and China also influences the price for all the other markets. SeafoodSource.com is a good resource to keep on top of price trends.


Is there a way to know if we are buying "sustainable" prawns?

Yes, for farmed prawns look out for the BAP (Best Aquaculture Practice) and the ASC (Aquaculture Stewardship Council) accreditations.

BAP is the most common aquaculture certification and rates the environmental, social, food safety and animal welfare grade in the production chain. ASC certifies seafood that has been farmed in an environmentally and socially responsible way.

Accredited prawns are 5% to 10% more expensive per kg than those not accredited but they are nevertheless important to look out for.

For wild prawns, scan for the Marine Stewardship Council (MSC) accreditation. This shows that a fishery has been independently assessed according to the MSC Fisheries standards for good management, environmental impact and health of stocks.

Surprisingly, transport is one key factor not captured in prawn accreditations. Prawns are shipped along long global routes, ranking up the products' environmental impact. This is another reason why IQF prawns make more sense than frozen block prawns: we are basically shipping less water around the world.


What else is worth taking note of on the packaging?

You might notice "E223" in the ingredient list. This is Sodium Metabisulphite, a synthetic preservative in which the products are soaked for two to three hours after being fished out. This preservative helps extend shelf life and prevents the heads from going black due to oxidation. Watch out for prawns that look too "bulky" though: it means they have been left in the soaking solution overnight to artificially increase their weight.

Another thing to look out for is their approved number: this means that the supplier is EU approved and the product is allowed to be imported into the UK. Every approved product has this number so if you don't see it, you should not trust what has been sold to you.

Last but not least, look out for the expiry and freezing dates. It's now mandatory that labels give you an indication of when the prawn was first frozen. As for expiry, frozen prawns that have dates near the end of their life mean that they are from stock nearly two years old. A eye opener for an often lower-than-current market price.

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