When the temperature of food reaches the danger zone between 40 degrees Fahrenheit and 140 degrees Fahrenheit, bacteria like Staphylococcus aureus, Salmonella enteritidis, Escherichia coli, and Campylobacter can grow to dangerous levels and cause illness. At those temperatures, bacteria can double in number in as little as 20 minutes. For these reasons, food manufacturers, distributors, warehouses, and retailers must make sure that refrigerated and frozen foods stay cold until they are purchased or served.
The cold chain refers to the succession of refrigeration steps along the supply chain used to keep perishable food in a healthy temperature range. The chain analogy is used to make clear that food quality is only as strong as its weakest link. If food temperatures fall out of range at any step along the way, that food can be compromised.
Food suppliers need to use proper refrigeration throughout the entire cold chain and implement a Hazard Analysis and Critical Control Points strategy to manage the cold chain and ensure food safety. Temperature monitoring, recording, and data logging technologies make that job a lot easier and provide an additional layer of protection.
Remote Temperature Monitoring Systems
Although commercial refrigerators and freezers come equipped with thermometers, many don’t have a way to alert users if the temperature strays out of the safe zone or if the power goes out. Having personnel check and record the temperature around the clock is impractical and unreliable. Just because the air and products inside of the unit feel cold, that doesn’t mean it is the appropriate temperature to maintain food safety.
A remote monitoring system can help companies in the food industry comply with FDA regulations, maintain accurate records, and, most importantly, keep food safe. These systems have alarms that send notification via phone call, text, or email to designated contacts when a temperature falls outside a preset range.
The base unit is the heart of the monitoring system. It pulls data (like temperature, humidity levels, etc.) from the sensors that are placed in key areas in a refrigerator or freezer. Users can select a base unit that communicates via a phone landline, Ethernet, or cellular connectivity. The system’s internal rechargeable battery backup ensures continuous monitoring and alerts in the event of a power outage.
When a monitoring system identifies a change in status outside of the preset range, it immediately sends alerts to people on the contact list. If users don’t want all of their personnel to receive notifications at the same time, some devices can be programmed to send alerts in a tiered fashion or on a schedule. Multiple communications methods like phone, email, and text provide extra assurance that the alert will be received.
It’s a good idea to check the number of people the system can reach and if the system automatically cycles through the contact list until someone responds. Some systems allow for flexible scheduling, so that off-duty personnel don’t receive alerts.
Programming and Status Check
For optimal performance, select a cloud-based system that delivers real-time status of all monitored conditions and sensor readings on demand. Options to access sensor readings include calling to check status, viewing a web page, or accessing it via an app on a mobile device. If a cloud-based system isn’t selected, users will be limited to logging in through a local area network. Both allow for programming changes, access status conditions, and review of data logs.
Temperature Probes and Buffers
There are different methods that measure temperature inside a refrigerator or freezer. The most basic instrument is the thermometer, which reads and displays temperature in the same simple device, while probes and sensors connect the environment or items being measured to more complex monitoring devices.
Temperature sensor probe. Sensors are basic devices that detect or measure temperature or other physical properties. A temperature probe is a metal sensing rod that can be inserted into a refrigerator or freezer. Sensor probes inside the cool storage unit detect or measure temperature or other physical properties. They are connected via wires or wirelessly to the monitoring device, which continually displays and records the temperature readings.
An important distinction between a sensor and a probe is that a probe is much more resistant to harsh conditions. A temperature probe is able to withstand temperatures that are too cold for most sensors or contact-type switches. Because they are so hardy, temperature probes can be placed in cold and wet environments that could ruin electronics or be inappropriate for a thermometer.
Most commercial-grade refrigerators have access ports to allow for third-party temperature probes, which is best practice. However, users can drill a hole in the side, insert the probe and then seal the hole, or simply place the probe in the refrigerator and run the wire through the door opening. The gasket around the door should make a strong enough seal around the wire to keep the outside air from seeping in.
Temperature buffer. A sensor probe can be used with or without a temperature buffer, which acts as a cushion against temperature fluctuations in a freezer or refrigerator. A typical buffer is a bottle filled with glycol solution or glass beads. A probe is then inserted into the bottle. Buffers help to mimic the temperature of the food in your refrigerator or freezer. Without a buffer, the probe or sensor measures the atmosphere inside the storage unit, which can change rapidly with defrost cycles, door openings, or fans circulating the air. The air temperature of the storage unit changes much more quickly than the temperature of food products, so a buffered probe reading more accurately represents the temperature of the stored goods.
Buffers also reduce false alarms caused by slight changes in the air temperature inside the unit. False alarms are not only a nuisance, they can cause the data logs to record misleading information, which can make it seem like a facility is not maintaining compliance.
Wireless probes. A hardwired monitoring system connects sensors to the base device with wires. A wireless system uses built-in radio transmitters to communicate data readings to the monitoring system. A wireless temperature probe allows for greater flexibility in the placement of the probe, sensor, and remote monitoring system.
Automatic Data Logging
Because it is important to keep an ongoing record of temperatures to document that food is stored properly, select a monitoring system that logs and stores data. This data history is also valuable in identifying trends in temperature fluctuations. Recognizing unusual patterns could provide insight regarding potential equipment complications.
Monitoring systems record tens of thousands of data points, dates, and times. Cloud-based logging provides an unlimited number of records for users to view, graph, print, and export data trends. More advanced systems allow users to log both the highest and lowest temperatures over a set period of time. This provides a snapshot showing whether the temperatures were within range that day, which is especially convenient when the person responsible for temperatures is not the same as the person designated to receive alarm notifications.
A simple measure to help maintain safe food temperatures is to monitor the power at each refrigerator or freezer’s outlet with a power-out sensor. If a breaker trips and power is lost at the cooling unit, monitoring the power will provide ample time to take corrective action, rather than waiting until the food temperature limits are at a dangerous point.
Depending on the situation, users might want to monitor the room or building that houses their cold storage units or the refrigerators and freezers themselves. Magnetic reed switches are used with monitoring systems to detect unauthorized entry or intrusion. They are usually installed on doors or windows to detect opening and closing. Placing them on the doors of cold storage units can let users know when they are opened during off hours or if they have not been closed at the end of a work day or shift.
It’s vital for public health to keep perishable food products within the recommended safe temperature range throughout the cold chain. Remote monitoring systems and data loggers protect food inventory 24/7 and provide an audit trail documenting storage at proper temperatures. Because these devices are inexpensive and easy to install and maintain, they are a cost-effective way to prevent a potentially devastating problem.
Fusco is director of business development with Sensaphone, a developer and manufacturer of remote monitoring and alerting systems. Reach him at firstname.lastname@example.org or 877-373-2700.