Wendyl wants to know: All red and 'tomatoey'

Leggo's Tomato Paste (pottle) 2 x 140g for $2.90.

Each week, Wendyl Nissen takes a packaged food item and decodes what the label tells you about its contents.

Tomato paste is an essential part of any cook's arsenal to perk up a spaghetti bolognese, casserole or spread on a pizza base. It's an easy way to bring in the taste of tomatoes without having to use too many actual tomatoes.

I was first asked to look into tomato paste by well-known chef Tony Astle from Auckland's Antoine's restaurant. He found that when he cooked with the paste it didn't behave as tomato paste should.

"It was very bitter, seemed to thicken rather than give any flavour other than salt and bitterness," he said. "There's something not quite right about it."

I had a cursory glance at a tin of it in the supermarket and could see nothing added so put it down to Tony having a bad day.

Then a friend whose son has to watch his salt intake asked me to look at the sodium content of tomato pastes which she found differed dramatically between brands. So I picked up three different types and was amazed at what I found:

Watties Tomato Paste (tinned) 310g for $2.65

Concentrated tomatoes
This simply involves cooking tomatoes for a long time until the water is reduced and you are left with an intensely flavoured paste.

Adding tomatoes into your cooking brings with it lycopene. Lycopene has been the subject of many health studies which claim that a high intake can help reduce the incidence of cancer, cardiovascular disease and macular degeneration. However, there is no firm evidence this is the case.

And the studies concentrated on tomato intake rather than lycopene supplements which means that the other nutrients found in tomatoes such as Vitamin C, folate and potassium might be giving benefits rather than the lycopene.

One thing everyone agrees on is that tomatoes are very good for you.

Food acid (citric acid)
This will be in here either as a natural preservative or a pH balancer.

There is no salt mentioned as an ingredient in this paste yet the nutrition label tells us there is 40mg of sodium per 100g. This will be because tomatoes naturally contain sodium - one large tomato contains 9g of sodium.

Label says:
No added salt or sugar.
No added colours, flavours or preservatives.
99 per cent fat free
Rich in lycopene.

Leggo's Tomato Paste (pottle) 2 x 140g for $2.90

Salt
The nutrition label tells us there is 460mg per 100g of this paste. That is 11 times the amount found in the Wattie's paste.

Label says:
No artificial colours.
No artificial flavours.
No added preservatives.
99 per cent fat free.

Leggo's Tomato Paste (squeeze bottle) 400g for $4.39

Salt
The nutrition label tells us that there is a massive 765mg of sodium per 100g. This is 19 times more than the Wattie's paste and just over 1.5 times the sodium in the pottle version of this product.

Because there is 400g of this product it may be that extra salt is required to stop it going off in the fridge as you would be unlikely to use a whole bottle in one sitting. However, as we see below, there are also preservatives added.

Antioxidant (ascorbic acid)
This will be in here as a preservative.

Preservatives (202,234 (contains barley).
These are potassium sorbate (202) which is neutralised sorbic acid and nisin (234) which is produced by fermentation of substances such as milk but in this case probably barley. Neither preservatives have known adverse health effects.

Label says: Rich in lycopene. A powerful antioxidant.
99 per cent fat free.
No artificial colours.
No artificial flavours.

My recommendations: Who would have thought there was so much sodium lurking in some of these pastes?

For most people this won't be a problem but for people with health issues which require close monitoring of sodium levels this could really catch them out.

It is recommended that adults eat between 920mg and 1600mg per day.

And for home cooks adding a salty tomato paste would mean that a casserole or bolognese could end up a lot saltier than intended.

I was relieved to see online that the two Leggo's salt-laden tomato pastes do come in "no added salt" varieties but they weren't in evidence at the supermarket I shop at.

So look out for products which clearly state no added salt when buying tomato paste.

And avoid any which lists preservatives.

I've swapped to the Wattie's 310g tin and any I don't use gets put into ice cubes and stored in the freezer to pop into my cooking or defrosted in time to smear on pizza.

In summer you can also make your own tomato paste for use over winter. Look online for recipes.