Education caterer Innovate Services' recent research into packed lunches found that just 7% complied with the food-based standards for school dinners.
The caterer's Lunch Box Amnesty study group also found that just under a quarter (24%) of lunch boxes analysed achieved the food-based standard of a minimum two portions of fruit and vegetables, while the majority (77%) contained a type of food or drink that was not permitted.
Public health nutritionist Robert Hobson, who carried out the analysis, said that the audit showed that a majority of the lunch boxes failed to meet the food and nutrient-based standard for school lunches, suggesting that lunches offered in the school canteen could instead offer a far healthier alternative.
Professor Lisa Ackerley, chartered environmental health practitioner, said the findings also highlighted a need to look at the microbiological safety of foods.
"From the initial findings it is clear that many lunch boxes are kept for several hours at room temperature, potentially allowing food poisoning bacteria to grow," she explained.
Derick Martin, co-founder and chief executive of Innovate Services, said: "From our sample, it is clear that producing a lunch box that includes the right nutrients, that is not exposed to potentially harmful bacteria and offers variety at an affordable price is a difficult balance to achieve.
"At Innovate, we have launched an onsite packed lunch option, which means students can choose a freshly made, temperature-controlled lunch box for the equivalent price of the school's 'free school meal'."
In total, 120 year 7 and year 8 students from four secondary schools took part in the study, providing a sample of 70 packed lunches to analyse from a nutritional standpoint.
Of these, 49 lunch box samples were subsequently tested from a food safety and hygiene perspective and 80 students also completed written questionnaires.
By Janie Stamford
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Published by: The Caterer