By Walter Trupp, Chef
The history of the prawn as a food source is an interesting but short one, as it was not a big part of the human diet until the 1950s, when the discovery of deep-water prawns in the Gulf of Mexico had a dramatic impact on the world of cooking. Before this, only the smaller cold-water prawns of the north Atlantic had been fished, mainly around Greenland and Scandinavia.
Today, approximately 30 different species of prawn are commercially fished. The largest, best-quality crustaceans are found in the coldest waters of the Pacific and the south Atlantic, down to a depth of about 800 metres. With their sweet, nutty flavour, they can attract higher prices than lobsters. The variety most commonly offered in Australia is the black tiger prawn, which is both caught in the wild and farmed. King prawns and leader prawns are the most expensive wild varieties, while banana, endeavour, red spot king and red tail prawns are generally cheaper.
Prawns are reproduction machines, with females producing up to 80,000 eggs yielding 3000 baby prawns at one time. The youngsters grow quickly and moult their shells at the monthly full moon, and some of these offspring reach a length of 35 centimetres. Because prawns reproduce so strongly, they do not fall into the category of unsustainable seafood, although the methods used to catch them result in huge amounts of by-catch (refers to the animals that are ‘mistakenly’ caught in nets along with the targeted species). Some commercial fishing operations use specialised nets known as turtle excluder devices, which allow these marine creatures to escape—if this is the case, it will be stated on the packaging of frozen prawns. Promisingly, a new type of net is being trialled in Spencer Gulf off South Australia that apparently results in no by-catch at all.
Farmed versus wild prawns
My opinion is that you should only eat wild, sustainably fished prawns, and here are some reasons why.
A few years ago, there was a ban in Australia on the importation of farmed prawns, which are bred in enormous water tanks here and in the Americas, as well as in the rice fields of tropical Asian countries. This was because they were said to be one of the most chemically polluted foods you can eat. The irony of this story is that acceptable Australian-farmed prawns that had been sent to Asia for processing (peeling etc.) were then not allowed back into the country, which makes you wonder why they weren’t just banned as well to begin with.
At the time, I came to know a local quarantine officer and I asked him to explain the ban. He told me that highly toxic chemicals such as antifungal/antifoaming agents were being used by cheaply run prawn farms to stop the tanks or rice fields from foaming up, which is what happens when prawns are forced to live in extremely cramped conditions. The quarantine officer also mentioned the use of sodium metabisulphite (or E223) to prevent the oxidisation and discolouration of the prawn shells. According to Asthma Australia, this agent is one of the most common chemical triggers for asthma, and has also been linked to cases of dermatitis and hay fever. Another preservative that can legally be added to prawns is 4-hexylresorcinol (E586), which is suspected of causing bowel irritation and harming organs such as the heart and liver.
All prawns contain at least one of the aforementioned preservatives, so I suggest that you always wash green (uncooked) prawns thoroughly under running water before peeling and cooking them, to get rid of any chemicals. I also suggest that, before buying uncooked prawns, rub some of them softly between your fingers—if they feel soapy (just imagine having some soap on your fingers), then they are covered with preservatives. Cooked prawns, on the other hand, often contain few or even no preservatives; I talk more about precooked prawns a little later on.
Getting back to the ban, importers quickly found a loophole they could exploit. The ban did not apply to marinated prawns, so companies simply added a bit of garlic, vegetable oil etc. to their product and so managed to get around the regulation. The whole thing quickly turned into a farce, with consumers never being told exactly what had happened.
Another reason why farmed prawns can be considered one of the dirtiest foods we eat is that the creatures are fed foodstuffs made mostly from fish and soy flours, similar to what is given to poultry and farmed fish. Some prawn farms also use large quantities of antibiotics, hormones and other chemicals such as food colouring—added to cooked prawns to give them a natural-looking bright red colour—which in many cases have serious adverse effects on local waterways, not to mention the prawns themselves. And because these farms are often located around agricultural operations, the prawns can be exposed to chemical run-off, which leads to the accumulation of heavy metals in their bodies.
This does not mean that all prawn farms are horrible, nor can it be said that farmed prawns from any particular country are worse (or better) than those that come from another country. It really comes down to the individual grower—Crystal Bay prawns based outside Port Douglas in Queensland, for example, grow a premium and clean product.
Buying and defrosting prawns
So how can you tell the difference between wild and farmed prawns? Firstly, there will be a huge price difference, as wild prawns often cost up to three times as much as farmed ones. Secondly, you will be left in no doubt as to which is the more natural product when you compare flavour and texture. Wild prawns are best described as crunchy, nutty, sweet and clean-tasting, whereas badly farmed prawns will remind you of well-chewed gum, lacking texture and with a soapy/plastic flavour.
When you are shopping for prawns, also keep in mind that size does not really matter. Generally, the larger prawns are more expensive simply because they are easier to peel and cook. Some people say they have a better texture and taste, but I don’t share this view. The taste will depend more on the prawn’s freshness and how you cook it. That said, it is true, as I mentioned earlier, that the larger prawns from deeper ocean waters are generally of better quality.
The catch date is an interesting issue. As prawn fishing seasons have short catch windows, you will often find that the pricey prawns you buy at Christmas are actually several weeks or months old. You can save yourself a bit of money by buying frozen prawns well before the festive season. Legally, frozen prawns can sit in the retailer’s freezer for up to 18 months. Also pay attention to the other information on the packaging, which can include details of whether a sustainable or non-sustainable catching method was used.
Wild prawns are mostly offered frozen—even the best restaurants in the world often have to use frozen product. This is because prawn trawlers often stay out at sea for long periods of time, until they have caught their quotas or filled their holds, and they immediately freeze their catch so it won’t spoil. This makes it extremely unlikely that you will ever be offered fresh wild prawns. Rather, any unfrozen wild prawns that you buy will already have been defrosted, which means you should not freeze them again. My advice is that if you aren’t going to eat the prawns straight away, buy them frozen and then defrost them yourself—you will end up with a much fresher product.
The secret to great-tasting prawns lies in how they have been defrosted. It is not a good idea to thaw prawns at room temperature as the outer cell tissue will defrost first and encourage the growth of bacteria, as well as drying the shell out. The best method is to cover the prawns and let them defrost slowly in your fridge over a period of between 36 to 48 hours. Of course, this is a very long time, and I know from my own experience that this is hardly ever feasible at home. So as an alternative, I suggest that to speed up the process, you wash the prawns really well under lukewarm water and then spread them over an oven tray and turn them over once or twice to stop them from drying out. This all takes around 2 to 3 hours and is perfectly safe.
You will find that a wild prawn will turn blackish within a few hours of being washed, but this is not really a problem. This is due to a lack of preservatives and does not mean the crustacean has gone ‘off’. The discolouration will more or less disappear once you cook the prawn.
A more unconventional but extremely effective method of defrosting is to wash and dry frozen prawns, then boil or roast them while they are still frozen. This minimises the defrosting process but means that you have to increase the cooking time to compensate.
Peeling and cooking prawns
Did you ever wonder where the real flavour of a prawn is hidden? It is in the head and shell and blossoms during cooking. If you’ve ever eaten a lobster or prawn bisque (a soup made only from shells), you will have experienced the flavour potential of crustacean shells.
This is why you should not peel prawns before cooking them. And in case you need further convincing, just imagine being spared the tedious job of peeling all those prawns yourself! After serving prawns, I always find it quite amusing when suddenly the whole table goes silent as everyone focuses on peeling them, usually followed by the sound of people licking that delicious shell taste off their fingers. If you really do not want to serve your prawns unpeeled, then strip off most of the tail shell—break the shell where the little feet sit, as it’s at its softest there—but leave the tail end and the head untouched. This means you will not lose too much flavour during the cooking process, and it’s also a nice way of presenting the prawns.
Here’s an extra tip: do not wash peeled prawn meat, whether it’s raw or uncooked, as you’ll only end up washing away a lot of the meat’s flavour. We don’t do this with steaks, but for some reason we think it’s okay to do it with fish fillets and peeled prawns!
As for deveining, it’s good to do this with larger prawns. Their veins can harden during cooking and often contain lots of poo and sand, which can be quite disgusting when eaten—a full vein can add a very unpleasant flavour to your prawn experience! The best way to devein a prawn is to straighten it out and make a little incision on the top side from just below the head down to the tail. Then get hold of the digestive tract with the tip of a small knife and carefully lift the vein out. (As an aside, wild prawns are hardly ever peeled and deveined, while farmed prawns are almost always peeled and deveined.)
A word on precooked prawns. These can be a bit of a lottery. They are often overcooked, and if frozen for too long they can end up being rubbery or chewy when reheated, with a blunt flavour. Precooked prawns are really only suitable for consumption when they are cold.
When roasting or otherwise cooking green (raw) prawns, you need to remember that overexposure to heat can make the meat dry and chewy. Perfectly cooked prawn meat will have a glossy centre—think about medium-cooked steak—and a bright, shiny colour. This will guarantee the uniquely delicious and crunchy ‘prawn bite’.
How to boil prawns
The following recipe is for approximately 20 large frozen prawns.
Bring 4 litres of water to the boil and season with a teaspoon of salt.
Add the frozen prawns and cover the pan.
Bring to the boil again as quickly as possible, then turn the heat straight off.
Let the prawns sit in the water for 18–20 minutes, then strain and peel or serve whole.
Note: if you use defrosted prawns, decrease the resting time in water to 4–5 minutes. Cooked prawns will last for up to three days when stored in the fridge.
How to grill frozen prawns
Wash the ice coating off the frozen prawns and dry them on kitchen paper.
Warm some butter or coconut oil on medium heat.
Add the prawns and cook for 3 minutes on each side.
Cover the pan and let it sit for 10 minutes.
Move the prawns onto a warm plate, add some aromatics (garlic, chilli etc.) to the pan and cook until ready.
Put the prawns back into the pan together with fresh herbs or liquids like coconut milk, honey, palm sugar, sherry vinegar etc., and reheat under constant stirring.
Prawns glazed with honey and sweet sherry
Preparation time: 20 minutes
Completion time: 30 minutes
Makes: 4 serves
1 kg prawns
3 tablespoons butter
1 large shallot, finely chopped
1 carrot, cut brunoise
1 white leek, cut brunoise
2 tablespoons honey
1 cup sweet sherry wine (or port wine)
¼ cup sherry vinegar (or white balsamic vinegar)
3–4 tablespoons double cream
salt and pepper for seasoning
2 tablespoons parsley, chopped
Clean the prawns, leaving the tails on.
Heat 1 tablespoon butter.
Add shallot, carrot and leek and cook for 2–3 minutes.
Add prawns and roast until cooked through.
Remove prawns from pan, add honey, wine and vinegar, and reduce to a glaze.
Once a thick consistency is achieved, add remaining butter and cream and bring to the boil.
Add prawns and glaze with sauce.
Season, sprinkle with parsley and serve with steamed rice.
For more on the selection and preparation of prawns, as well as other seafood, have a look at Trupps’ Wholefood Kitchen, our new book on eating well, living well and feeling great.