Sandwiches sold from sandwich bars, garage forecourts, bakers or newsagents were highest risk, confirming fears that 'cowboy operators' who prepare sandwiches in domestic kitchens and sell them cheaply to individual outlets are a growing threat to public health.
Sandwiches are now more popular than fish and chips, pizza, and hamburgers and the market has doubled in value since 1985, to pounds 1.5bn annually, according to the British Sandwich Association. About one-third of the population eat them every day, with 94 per cent eating them at least once a month. Precise sales figures are not available but the average cost is pounds 1, which means more than a billion are sold each year.
Most of the bigger food stores have added sandwiches to their range and on the whole came out of the survey well. Tesco and Asda supermarkets, however, were singled out for criticism in the Which? report published today. Listeria was found in 4 out of 10 sandwiches from one branch of Tesco. 'Levels were low, but ideally we shouldn't have found it at all,' the report said.
At an Asda branch, 4 out of 10 sandwiches contained Staphylococcus aureus, and 3 had 'unacceptable levels' of the microbe which may be present on dirty hands or an uncovered boil or septic wound.
Which? researchers bought 132 sandwiches - one every day for 10 days - from outlets in Hertfordshire, choosing the most popular fillings of prawn, chicken or ham. According to the report ' . . . over half contained more bacteria than you'd expect, had they been prepared following good hygiene practices'. Food poisoning bacteria were found in 21 sandwiches. The researchers concluded that 'in most cases, the level of contamination was low and none of these sandwiches was of immediate danger but ideally we shouldn't have found these levels . . .'
The survey also compared fillings and found sandwich bars gave the best and worst value for money - one used 86gm of prawns while another averaged only 23gm per sandwich. Four out of five sandwiches from Boots gave fewer prawns for the money than Marks & Spencer, Tesco or Sainsbury.