Understanding Near-Infrared (NIR) Spectroscopy in food testing

Near-Infrared (NIR) spectroscopy is a powerful tool for rapid, non-destructive analysis of food products, helping to ensure quality, safety and accurate labelling across the food industry. © Shutterstock

Near-Infrared (NIR) spectroscopy has become an essential tool for rapid and precise food quality analysis. Widely used across the food and beverage industry, as well as in agriculture, NIR offers a fast, cost-effective alternative to traditional chemical testing.

In this article, New Food explores the fundamentals of Near-Infrared spectroscopy — how it works, what it measures, and why it’s crucial for food safety and quality.

Why food quality analysis matters

Food safety and quality are top priorities for manufacturers, retailers, and consumers alike. Contamination and adulteration — particularly in products like meat, dairy, and alcoholic beverages — remain significant concerns across the supply chain. To maintain consumer trust and comply with regulations, producers must ensure that food products are authentic, safe, and properly labelled.

Near-Infrared spectroscopy has become a critical tool to help the industry achieve this, enabling companies to:

• Verify ingredients and additives
• Analyse product composition for labelling compliance
• Detect signs of food fraud
• Optimise production processes in real time

Understanding Near-Infrared energy

Near-Infrared energy is part of the electromagnetic spectrum, emitted through molecular vibrations that are invisible to the human eye. Like visible light, infrared energy spans a range of wavelengths. Near-Infrared waves, found closest to visible light on the spectrum, do not generate heat detectable by humans but interact with materials in ways that can be measured.

How NIR spectroscopy works

NIR spectroscopy measures how Near-Infrared light interacts with a sample, typically within a wavelength range of 700 to 2,500 nanometres. Light is either reflected off or transmitted through the sample, and the resulting signal provides detailed information about its composition.

One of NIR’s key advantages is that it requires little or no sample preparation and can analyse multiple components simultaneously. This makes it an ideal method for non-destructive testing of a wide range of food products, from grains and dairy to meat and oils.

What can NIR measure in food?

Near-Infrared spectroscopy is widely used to quantify important components in food and agricultural products, including:

• Protein
• Carbohydrates
• Moisture content
• Fats and oils
• Polymers and other compounds

It is also used to assess ingredients and additives for purposes such as colouring, thickening, and flavour enhancement. Commonly analysed substances include:

• Nutrients and vitamins
• Enzymes
• Amino acids
• Emulsifiers
• Preservatives
• Sweeteners

The science behind NIR measurements

Different molecules absorb specific wavelengths of Near-Infrared light, creating a unique spectral ‘fingerprint’. By interpreting these patterns, NIR instruments can determine the concentration of key substances — for instance, moisture or fat content — within a sample.

Reflectance vs. transmission in NIR

There are two main methods of Near-Infrared measurement:

• Reflectance: Measures light reflected from the sample surface. Suitable for powders, grains, and solid foods.
• Transmission: Measures light that passes through the sample. Useful for liquids or whole foods where internal composition is key.

The method chosen depends on the product and the information required.

Non-destructive testing benefits

NIR’s non-destructive nature means that food samples remain intact during testing — an essential feature when analysing high-value or bulk products. It’s especially useful for screening unprocessed grains for gluten content or evaluating meat and fish for quality without cutting or altering them.

Calibration and accuracy

For NIR devices to deliver reliable results, they must be carefully calibrated. Calibration compares NIR readings with known reference values to create a model that the instrument uses to predict future measurements.

Techniques used for calibration include:

• Multi-linear regression (MLR)
• Partial least squares (PLS)

Although no method is completely free from variability, NIR spectroscopy typically achieves accuracy levels around 1.5 times higher than the variability of the reference methods used. Modern devices further improve precision using extensive databases and advanced prediction models.

Advances in NIR technology

NIR spectroscopy has advanced rapidly, with modern devices becoming smaller, faster, and easier to use. Handheld and portable NIR instruments now allow in-line and at-line testing, enabling real-time monitoring on production lines.

These developments offer several benefits:

• Minimal waste due to limited sample prep
• Faster results compared to traditional lab testing
• Reduced human error
• Versatility across different food matrices
• Simultaneous analysis of multiple components
• Simple operation with minimal training required

The future of Near-Infrared spectroscopy in the food industry

As food safety regulations tighten and consumer expectations rise, Near-Infrared spectroscopy is set to play an even greater role in food production and quality control. Its ability to deliver quick, accurate, and non-invasive analysis makes it an indispensable technology for modern manufacturers.

Looking ahead, we can expect to see:

• Further miniaturisation of NIR devices for in-line and at-line testing
• AI-enhanced calibration models for even greater accuracy and reliability
• Broader adoption across sectors, from agriculture to ready-to-eat meals

By using Near-Infrared spectroscopy, food producers can improve product consistency, meet safety standards, and respond more effectively to the growing demand for transparency in the food supply chain.