This version is not peer-reviewed
Injury Threshold of Mouth Contact with Hot Solid or Paste-Like Foods and Sensory Evaluation of Consumption Temperatures
: Received: 6 August 2018 / Approved: 6 August 2018 / Online: 6 August 2018 (14:53:22 CEST)
: Received: 9 August 2018 / Approved: 9 August 2018 / Online: 9 August 2018 (12:50:40 CEST)
A peer-reviewed article of this Preprint also exists.
Journal reference: Safety 2018, 4, 38
Epidemiological studies indicate an increased risk of cancer from the consumption of very hot foods and beverages. The International Agency for Research on Cancer (IARC) has already recommended threshold values for the maximum drinking temperature of very hot beverages. The contact time and the contact temperature are decisive for the risk of injury when hot media come into contact with human skin. However, measuring the contact temperature is not easily possible in practice. In the present study, a numerical simulation based on the solution of the heat conduction equation was initially used to investigate whether and for what period of time a constant contact temperature is to be expected under oral conditions. For small circular 3-cm food samples (e.g., cooked potatoes) with 2.5 mm thickness in contact with the tongue, the simulation results in a constant contact temperature of 10 s before cooling. With a thickness of 0.5 mm, the contact temperature is only maintained 1 s. Hot drinks, which spread as a thin film and thereby increase their surface area, can therefore be consumed at higher temperatures than solid foods. Furthermore, a simple test technique with a "measuring spoon" was developed. A hot sample is placed on the tongue. Orientating measurements were used to determine which contact temperature was considered to be just comfortable for any period > 10 s and for which period of less than 10 s it was still just bearable. The contact temperature, which was still perceived as tolerable for periods > 10 s, was 46.5 °C. The time spans for the higher contact temperature 48 °C were between 2 and 4 s and for 49 °C between 1 and 2 s. The course of the contact temperatures determined in the experiment over the contact time allows to calculate the corresponding threshold values of consumption temperatures for various foods such as potatoes, vegetables, cheese or fish. Consumption temperatures of about 56 °C for potatoes and 60 °C for cheese are still perceived as tolerable. In view of the fact that the contact temperature is obviously the determining factor for the risk of injury from burns in the oral cavity in addition to the contact time, it makes sense to reference threshold values to the contact temperature rather than to the surface or consumption temperature of a food product, which is the customary practice up to now. If this contact temperature is defined as a threshold value, the surface or consumption temperature for any other food can be calculated.
hot foods; temperature; esophageal cancer; thermosensing; sensory thresholds; methodological study
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