Food selled as hot is widespread in retail stores, gas stations, convenience stores, and small catering establishments. They are prepared using devices that simultaneously heat the product, maintain its appropriate temperature and present it in an attractive way. It is popular because it meets the needs of consumers who are looking for warm, readily available products suitable for consumption outside the home.
Temperature control and microbiological safety
Simultaneous heating, keeping the product warm and its commercial display makes temperature control especially important. The term “temperature of consumption” primarily has practical and sensory significance, as it means the temperature at which the consumer judges the product as sufficiently warm, tasty and ready for consumption. However, this temperature should not be equated with the temperature that ensures the microbiological integrity of the food. Namely, the product can have an appropriate sensation of heat when consumed, and at the same time represent a microbiological risk if there was a break in the cold chain, subsequent contamination, insufficient heating or prolonged stay at temperatures suitable for the growth and reproduction of microorganisms.
From a food safety perspective, process temperature parameters are critical, including heating temperature and heat holding temperature, as they determine the effectiveness of heating the product throughout its volume and limiting microbial growth during retail display. The temperature inside the product, not just its surface temperature, is particularly important. Products intended for sale as hot are usually heat treated during production, then cooled, packaged, transported and reheated at the point of sale. This means that their safety depends on maintaining appropriate conditions at every stage of distribution: from production and transport, through cold storage and preparation for sale, to heating, display and personnel hygiene.
Main bacterial risks
Although the process of preparing and selling these products may seem simple, they can represent a potential source of microbiological hazards. The presence of these risks is related to the composition of the product, high water activity (high content of available water), the presence of proteins, the possibility of subsequent contamination, as well as the extended time of exposure during sale. Listeria monocytogenes, Salmonella spp., Escherichia coli, Staphylococcus aureus, Bacillus cereus and Clostridium perfringens are among the most important pathogenic microorganisms that can pose a risk. In addition to pathogenic microorganisms, indicator microorganisms, especially the total number of aerobic mesophilic bacteria and bacteria from the Enterobacteriaceae family are important in the assessment of hygienic and microbiological correctness.
Of particular importance is the bacterium Listeria monocytogenes, which is able to reproduce even at refrigeration temperatures, as well as to survive in production and retail conditions, among other things thanks to the ability to form biofilms. Staphylococcus aureus can also be a risk, the appearance of which is often linked to inadequate maintenance of staff hygiene. This microorganism can produce enterotoxins that are resistant to high temperatures, so subsequent heating of the product does not always eliminate the risk of poisoning. Also, sporogenic bacteria, including Bacillus cereus and Clostridium perfringens, can pose a danger if the product is stored for a long period at temperatures suitable for their development.
Control procedures and Good Hygiene Practices (GHP)
The basic condition for the safety of products intended for sale as warm is to maintain the continuity of the cold chain. Products should be transported and stored in accordance with the conditions specified by the manufacturer, usually in a refrigerated environment. Control should include temperature measurement at delivery, assessment of packaging condition, check of expiry date and monitoring of refrigeration equipment. Applying the FIFO (First In-First Out) or FEFO (First Expired-First Out) principle is also important. After opening the packaging, the product remains without part of its protective barriers, which increases the possibility of secondary contamination of its surface due to contact with personnel, equipment or the external environment.
Internal procedures should define the minimum temperature of the product after heating, the temperature of keeping warm, the maximum exposure time and the way to handle products that do not meet the established criteria. In practical terms, for food that is kept warm, a temperature of at least 63 °C during the exposure period can be considered as a reference value. Special attention should be paid to achieving the appropriate temperature in the very center of the product, because heating only its surface is not enough. Products that have not reached the prescribed internal temperature or have been exposed to temperatures outside the permitted range for a long period of time must be excluded from serving.
One of the key elements of the food safety system is the validation of the process of heating and maintaining the product at the appropriate temperature. It implies documented confirmation that the applied process parameters ensure a microbiologically safe product under reproducible conditions during sale. As part of the validation, it is necessary to include measuring the temperature inside the product, determining the time required to reach the target temperature, assessing the uniformity of heating, testing the operation of the device at maximum load, as well as monitoring the products that need the longest time to reach the appropriate temperature. The validation procedure should be supplemented by continuous verification, which includes regular temperature control, keeping records of product exposure time, checking equipment settings, regular calibration of thermometers and application of appropriate corrective measures in case of deviations.
Good hygiene practices must be applied during all stages of product distribution. During delivery, it is necessary to control the temperature of the product, the hygienic correctness of the means of transport, the preservation of the packaging and the compliance of the delivered products with the defined specifications. During the preparation process, employees should use hygienic utensils and disposable gloves. The use of the same utensils for handling raw and finished products, disposal of equipment on contaminated surfaces, as well as combining products from different batches with unequal exposure time, represent unacceptable hygienic procedures. Equipment and work surfaces, including roller grills, trays, lids, containers and tongs, should be covered by a pre-defined cleaning and disinfection plan.
Laboratory verification
Microbiological analysis play a significant role in the control and verification of product safety. The intensity and scope of the test should be defined on the basis of risk assessment, product characteristics, previously obtained results and the conditions under which the product is placed on the market. As part of the microbiological examination, the total number of microorganisms, Enterobacteriaceae, Escherichia coli, coagulase-positive staphylococci, Salmonella spp. and Listeria monocytogenes should be analysed. When interpreting the results, it is necessary to take into account the moment of sampling, whether the sample was taken after opening the packaging, after the heating process or after a certain period of product exposure.
Safety of products – ready-to-eat food that is sold heated is conditioned by proper maintenance of the cold chain before preparation, adequate heating process, continuous maintenance of appropriate temperature and control of the length of the sales period, as well as consistent application of good hygiene practices by employees. An effective control system should include product receiving and storage procedures, clearly defined instructions for handling and using the heating utensils, regular temperature monitoring, cleaning and disinfection plans, employee training, process validation and periodic microbiological testing.
References:
- European Food Safety Authority. Scientific opinions and reports on Listeria monocytogenes in ready-to-eat foods. EFSA Journal.
- Food and Drug Administration. FDA Food Code 2022. U.S. Department of Health and Human Services.
- Regulation (EC) No 852/2004 on the hygiene of foodstuffs.
- UK Health Security Agency. Guidelines for assessing the microbiological safety of ready-to-eat foods placed on the market.
- Food Standards Agency. Safer Food, Better Business: Hot holding and temperature control guidance.
