Food safety practices used by food handlers are often monitored for research, inspection and regulatory purposes.
However, if surveillance is not concealed, it can result in unintended behavioural changes, according to Catherine Cutter, professor at the Pennsylvania State University in US.
Those changes - known as the Hawthorne Effect - can render such observations meaningless.
"Direct concealed observations have been used to minimise the Hawthorne Effect during observational data collection in various settings, but some limitations can include the need to memorise observations or take notes out of sight of those being observed," said Cutter.
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The researchers worked with a smartphone app developer to create an app that includes features needed to document direct concealed observations of food handlers, including the creation of checklists to record aspects such as hand hygiene, the adequacy of hand-washing facilities, the temperature in coolers holding ready-to-eat foods and the presence of potentially hazardous foods.
The app allows observers to easily add photos, audio, videos and open-ended notes to their reports.
To evaluate the use of smartphones as inconspicuous data collection tools, the researchers developed and disseminated a short survey to assess public perceptions of smartphone use in a retail setting.
Ninety-five per cent of participant responses indicated that images of clipboard use in a retail setting suggested evaluative activities - research, inspection, and so forth - whereas none of the participants indicated that images of smartphone use in the same environment suggested evaluative activities, said Robson Machado, a doctoral candidate in food science at Pennsylvania State University.
Smartphones are so ubiquitous, and text messaging and social media activities so common in public places, that no one questions what anyone does with their phone.
"This study should be of interest to researchers, regulatory personnel and food industry professionals who are seeking ways to evaluate the food safety behaviours of food handlers," he said.
The study was published in the journal Food Protection Trends.