A batch of frozen food being rejected for acceptance due to cross-contamination from a dirty measuring device is a real risk in many factories today. This situation poses a significant challenge for quality control professionals.

Optical sensors offer superior speed and effectively prevent the risk of organic contaminants adhering to the surface. However, does an infrared thermometer that only monitors the upper layer meet the technical and legal requirements?

This article is based on the document “General Principles of Food Hygiene CXC 1-1969” of the International Food Standards Committee (Codex Alimentarius). We will analyze the narrow-band mechanical aspects to help you establish an optimal control process.

1. Codex Standards on Time and Temperature Control

1.1 Temperature Management Regulations in the Production Chain

Controlling temperature dynamics plays a crucial role in suppressing microbial outbreaks. According to the technical regulations in Section 13.2.1 (Time and Temperature Control) of document CXC 1-1969, we must operate the temperature control system effectively. The monitoring process must take into account temperature variations affecting product safety.

These criteria require a thorough assessment of the physicochemical nature of each substrate. Specifically, characteristics such as water activity (aw), pH, and the pre-existing microbial community need to be controlled within a narrow range. This understanding helps prevent the growth of biological agents in hazardous zones.

1.2 Requirements for verification and calibration of measuring equipment

All tools for recording temperature data streams in the factory must ensure measurement consistency. International standards stipulate that temperature monitoring devices must be checked for narrow-band accuracy. In addition, the HACCP Team is responsible for performing periodic calibration or when technical needs arise.
This process helps to detect early errors in the resolution of long-band optical sensors. Therefore, the extracted results always maintain objective evidentiary value for post-audit work. This is a mandatory condition to affirm the management capacity of the testing laboratory.

2. Principle of optical radiation of infrared rays

2.1 Mechanism of surface energy absorption and emissivity coefficient

Long-range calorimetry devices operate based on the mechanism of receiving electromagnetic radiation emitted from the sample. The sensor focuses this energy flow through an optical lens to convert it into an electrical signal displayed on a digital scale. However, the accuracy of food temperature measurement depends entirely on the material’s emissivity.

Emissivity represents the radiant energy of a surface compared to an ideal black body at the same heat level. Highly reflective substrates such as stainless steel trays or aluminum foil often produce large optical errors. Conversely, the rough surface of fresh meat or narrow-strip plastic packaging allows for more accurate infrared absorption.

2.2 Significance of the Optical Distance-to-Spot Ratio D:S

The distance-to-spot ratio (D:S) determines the geometric structure of the actual measurement area. This mechanical index dictates the diameter of the infrared convergence area according to the operator’s standing distance. If you stand too far from the standard slope, the measurement area will be unintentionally expanded.
In that case, the probe will also pick up thermal radiation from the surrounding environment, distorting the displayed results. Therefore, food QA engineers need to calculate the optimal measurement distance for each workshop. This helps eliminate interfering factors and ensures the repeatability of the data.

When measuring temperature with an infrared thermometer, the correct measurement distance must also be adhered to in order to ensure accurate results

3. SATO SK-8700II Infrared Thermometer Specifications

3.1 Wide Temperature Measurement Range and Pulse Response Speed

To standardize screening work in factories, we need a synchronized system of high-end handheld hardware. Currently, the SATO SK-8700II infrared thermometer supplied by Duc Duong is a device that meets these requirements well. The product has a wide measurement range from -20°C to 315°C, ensuring optimal mechanical durability.
In particular, the optical pulse response time of this Japanese-made device is super fast, taking only 0.5 seconds. The display resolution with a slope of 1°C allows QC technicians to continuously record data. This compact configuration optimizes work progress on large production lines.
3.2 Permissible Error Limits and Fixed Emissivity Coefficient
The SK-8700II model boasts an extremely low measurement tolerance of ±2°C or ±2% of the measured value. Furthermore, the device is equipped with a fixed emissivity coefficient of 0.95 by the manufacturer SK SATO. This narrow-band configuration is ideally compatible with the vast majority of industrial food sample substrates.

The optimized emissivity coefficient eliminates complex manual adjustments by the tester. You can measure directly on plastic packaging or fresh meat without fear of error. This hardware solution delivers high performance and superior data consistency.
To establish a standardized SOP for controlling critical limits (CCP) and to receive guidance on calibrating the handheld optical thermal range, please leave your information in the Contact Us form at Duc Duong Company for the fastest assistance from our specialists.

SK SATO infrared thermometers are distributed by Duc Duong

4. Risks of Surface Temperature Measurement at Food Heating Control Points

4.1 Physical Limitations of Surface Temperature Measurement Only

The core physical limitation of spectroscopic sensor technology is that it only captures energy from the outer layer. The device is completely unable to penetrate the substrate to measure the core temperature of solid food. At the critical control point of a cooked control point, this biosecurity risk needs to be carefully considered.
The outer layer may report a safe temperature range, but the geometric core region remains within the danger range. Slow internal heat transfer will create conditions for the survival of toxic gut bacteria. Therefore, relying entirely on far-infrared measurement easily leads to pathogen leakage errors.

4.2 Strategy for Coordinating Rapid Screening and Penetration Measurement Devices

The HACCP Team needs to establish a standard operating procedure (SOP) for coordinating intelligent devices. We use the SATO SK-8700II device as a high-frequency wide-range screening tool on the conveyor belt. This solution helps you quickly detect batches showing signs of deviating from the permissible temperature range.

For the equivalence point determination step at the sterilization checkpoints, you must use an additional penetration probe. The thermal clamping needle will directly check the effective central core of the organic matter mass. This combination provides a perfect closed-loop biosafety protection network for the factory.

5. Lens Cleaning Procedure to Prevent Cross-Contamination

5.1 Controlling the Risk of Microbiological Contamination of the Measuring Instrument’s Upper Layer

If the optical receiving glass wall is obscured by dust and dirt, it will deflect the wavelength transmission. According to the guidance in Section 13.2.4 (Microbiological Contamination) of the Codex document, indirect contact surfaces must be thoroughly cleaned. Fine dust or droplets from raw food pose a risk of dangerous reverse cross-contamination.
The accumulation of high-frequency vapor in the processing workshop also degrades the sensor’s resolution. The measuring device itself, if not regularly maintained, will become a breeding ground for mold. Therefore, hardware hygiene control plays a crucial role in protecting the accuracy of measurement results.

5.2 Standard Optical Lens Cleaning Procedures

The periodic cleaning procedure for the lens requires high caution from quality control personnel. Use a soft cotton swab soaked in a specialized diluted alcohol solution to gently wipe the lens surface in a circular motion. Technicians must absolutely not use strong corrosive cleaning chemicals that will dull the SATO lens coating.
After each shift, remember to place the high-frequency thermometer in its shockproof protective case. The device should be stored in a dry tool cabinet, away from areas with high humidity. These practical SOP procedures help maintain consistently high infrared wavelength reception sensitivity.

6. Calibration of Temperature Measuring Equipment According to ISO 17025

6.1 Measurement Calibration Chain via Blackbody System

All data recorded at critical control points must demonstrate calibrated accuracy. This standard requires the equipment to be linked to a reference point through an unbroken series of calibrations. For infrared sensors, the verification process is performed via a standard radiation blackbody system.

The blackbody system provides absolutely stable temperature levels to correct the error range of the electronic circuit. This digitization process ensures that the measurement capabilities fully meet the requirements of the quality documentation. As a result, the lab’s data always has solid legal validity before regulatory authorities.

6.2 Establishing a Suitable Periodic Calibration Frequency for Operation

Based on the intensity of factory operations, we need to develop a scientific hardware inspection schedule. Experts recommend a periodic calibration frequency of once every 12 months. The temperature gradient range requiring calibration must be fully compatible with the actual operating temperature range of the machine shift.
Duc Duong Company provides a comprehensive after-sales solution certified to ISO 17025 measurement standards. Our team of engineers supports probe error range checks and replacement battery components are readily available. This synchronization ensures your quality management cycle runs continuously and stably.

Conclusion

In summary, the application of handheld spectrophotometer technology fully meets Codex requirements if you establish a synchronized solution. We need to strictly adhere to the temperature control regulations in Section 13.2.1, using models with a normalized emissivity of 0.95 such as the SATO SK-8700II for rapid screening, and flexibly combine them with penetration probe thermometers at heating endpoints to completely eliminate microbiological risks. Duc Duong Science and Technology Company is proud to be a strategic partner distributing genuine high-end food temperature measurement equipment from the global brand SATO Japan, ready to accompany businesses in enhancing their quality management capabilities.

To receive the complete technical specifications catalog and optimal price quote for the SATO SK-8700II infrared thermometer configuration meeting HACCP quality management standards, please fill out the information at Duc Duong Company Contact or contact our analytical equipment project hotline for the most in-depth support.

 

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Address: 1014/67 Tan Ky Tan Quy, Binh Hung Hoa Ward, Binh Tan District, Ho Chi Minh City

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Email: ducduong@ducduongco.com

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FAQ

1. Can infrared thermometers completely replace contact probe thermometers at cooking control points (CCPs)?

The answer is No. Infrared optical devices only capture radiation energy from the outer shell; they cannot measure the geometric core temperature of a solid sample. At critical control points for sterilization heating, the core of the food may still be in the microbiological hazard zone even if the surface temperature is within the safe range. Therefore, you must combine infrared technology for rapid wide-range screening and use a penetration probe to pinpoint and verify the core temperature.

2. Why does the Emissivity coefficient significantly affect the accuracy of food temperature measurements?

Emissivity represents the amount of infrared radiation that a material surface can emit into the environment. Shiny metal substrates such as stainless steel trays or aluminum foil packaging have low emissivity coefficients and high reflectivity, easily interfering with the sensor of the measuring instrument. The SATO SK-8700II series has a fixed emissivity coefficient of 0.95, the optimal level for absolutely accurate measurement of raw food groups or plastic film packaging without optical errors.

3. What are the requirements of the Codex HACCP standard regarding the calibration of factory temperature measuring equipment?

According to Section 13.2.1 of the Codex guidelines, all systems and equipment used to monitor time and temperature parameters affecting food safety must be checked for measurement accuracy. You need to perform periodic calibration of the measuring instrument’s hardware according to the schedule. All calibration records must be kept in written form as evidence for controlling significant hazards.

4. How to handle condensation or dirt blurring the optical lens of an infrared thermometer?

Condensation or dirt adhering to the glass surface will deflect the infrared wavelength transmission path, causing significant measurement errors. You need to establish a weekly maintenance SOP: use a soft cotton swab dipped in specialized alcohol to gently wipe the lens in concentric circles from the inside out; and always place the thermometer in its protective case after each shift to eliminate the risk of cross-contamination by adhering microorganisms.

5. How is the standard standing distance for measuring food temperature (D:S ratio) of the SATO SK-8700II instrument calculated?

The SATO SK-8700II model features a standard optical focal distance ratio suitable for close-range handheld operation. When performing non-contact food temperature measurements on a conveyor belt, QA technicians need to base their measurements on the actual standing distance so that the conical area of ​​the infrared focal point is entirely within the surface of the sample object, preventing the inclusion of ambient temperature which could lead to inaccurate digital display results.