The Microbiological Quality of Pre‐packed Sandwiches

Abstract

A survey of the bacteriological quality of pre‐packed sandwiches on sale in the UK is reported. A total of 91 sandwiches, of which 46 had been on display at ambient temperature, were analysed. Total viable counts were high: 38 per cent of all sandwiches had counts greater than 10⊃7. Coliforms were isolated from 37 per cent of the samples and at levels greater than 10⊃7 in 10 per cent. Listeria monocytogenes was isolated from 17 per cent of all sandwiches. Sandwiches that had been on display at ambient temperature had higher total viable counts and were more likely to contain listeria (28 per cent compared to 7 per cent for those stored at chilled temperatures). A small follow‐up study of sandwich ingredients found high counts in salad. The significance to the public health of the high contamination rate by listeria is unclear. Nevertheless, it would seem appropriate to ensure that sandwiches are always adequately refrigerated.

Isolation of Food Spoilage Yeasts from Salads Purchased from Delicatessens

“…Nevertheless, the isolation of E. coli at a count of 500 cfu/g shows that the possibility of contamination does exist. The generally low bacterial, coliform and Listeria counts found in this study contrast with the much higher counts found in other foods such as sandwiches and cooked meats[7]. This is despite the fact that delicatessen salads are frequently subject to repeat handling as they are spooned from the display containers into smaller pots for sale.…”

The Quality of Schoolchildren’s Packed Lunches

“…Manvell [7] reported that over half of the sandwiches surveyed were unsatisfactory. Hunter et al [8] also found that the microbial quality, as indicated by both total viable counts and coliform counts was generally poor. This was particularly notable in sandwiches displayed at ambient temperatures.…”

“…(7) Always use the foods within the recommended dates. (8) Do not cook fillings, e.g. chicken, too long in advance.…”