Thursday, August 12, 2010

More on Salt in Foods

It’s generally accepted that we eat too much salt in New Zealand – up to 150% of the maximum recommended intake (see Sodium in Food, 13 July 2010). Excessive consumption of sodium raises blood pressure and may increase the risk of cardiovascular disease. Bread is the greatest contributor to our sodium intake, followed by sausages and processed meats.

One of the concerns of manufacturers of foods that contain added salt is that the consumer will detect the change if salt content is reduced and refuse to buy that brand.

In 2003, I took part in a trial in which we tested three commercially baked breads with varying levels of salt, from the standard content at that time of 550 mg/100g, 5% reduction (530 mg/100g) and 10% reduction (490mg/100g). We performed controlled trials in which 60 consumers were given three samples - two identical and one different - and asked to pick the odd one out. This is called a triangle test. Twenty eight percent of the panellists correctly identified the 5% reduced sample and 37% identified the 10% reduced salt bread. This relatively small trial showed that these differences in perception of salt content were not statistically different i.e. that the consumers could not detect the lowered salt breads. Recent figures show that some breads now have 20% less salt than equivalent products in 2003.

As I wrote in “Sodium in Food”, July 2010, sodium chloride has many functions in foods besides flavouring. What are the alternatives to salt? We can replace some sodium with other ions, such as potassium, magnesium and calcium. We can purchase reduced sodium table salt, though the UK Food Standards Agency does not recommend the use of salt substitutes, as they don’t reduce consumers’ taste for salt. Replacement of 40% of sodium by potassium in manufactured foods may result in detectable flavour changes and there may be problems for people with kidney conditions. We could use other preservatives, but consumers have been fed the line that preservatives are bad for them, so there is likely to be resistance to this approach. We could target other sources of sodium in the diet, such as monosodium glutamate (MSG, a flavour enhancer), or water binding agents, such as sodium tripolyphosphate.

How will we know if reducing salt in our food will result in safe food? We can conduct computer-based modelling experiments, using the vast resources of microbial growth models stored in databases. Some of these databases are freely available and allow us to predict such things as “time to spoil” or “time to toxicity” or simply “how long will it take this initial level of contamination to grow to an unacceptable population?” We can vary the formulation of the food and run the model again to see how it performs. In a matter of minutes, we can do extensive trials of alternative formulations.

Unfortunately, these models are not real foods. Once we have modelled the likely shelf life etc. we have to make samples and test them under normal storage and abuse conditions. This is not straightforward and can be very costly. The likelihood therefore is that we will not see rapid reductions in salt content of our manufactured foods, but rather a progressive reduction, as was the case with bread. We can, however, make a start on personal salt intake reduction by using other seasonings and spices in our homes.

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