Understanding Near Infrared (NIR) Spectroscopy in food testing

Near Infrared (NIR) spectroscopy has emerged as a pivotal technique for rapid and precise food quality analysis. Its application is prevalent across the food and beverage industry, as well as in agriculture, providing a cost-effective alternative to traditional chemical analysis methods.

New Food examines the fundamentals of NIR, its function, what it measures, and its significance in ensuring food safety and quality.

Ensuring Food Quality

Food safety and quality are paramount concerns in the food industry. Contamination and adulteration, particularly in meat and alcoholic beverages, continue to pose significant challenges. Suppliers, retailers, and consumers alike require unwavering assurance about the integrity of food products.

NIR spectroscopy serves as a robust quality control tool that can:

• Identify ingredients and additives
• Analyse compositions for labelling accuracy
• Detect potential food fraud
• Optimise production processes

The Nature of Infrared Energy

Infrared energy comprises electromagnetic radiation emitted through molecular vibrations. Although indetectable to our own eyes, all substances emit a degree of infrared radiation. When atoms absorb energy, they release it in the form of infrared waves.

The infrared spectrum is akin to that of visible light, spanning various wavelengths. NIR waves, situated closer to visible light, do not produce heat detectable by humans.

Applications of Infrared Sensing

The infrared spectrum has diverse applications in sensing and detection. Infrared cameras and night-vision devices utilise electronic sensors to interpret infrared emissions. NIR spectroscopy analyses these emissions by measuring light that is either scattered or transmitted through materials.

In NIR analysis, instruments harness specific wavelengths of infrared light to evaluate the properties of various samples without changing their composition.

Mechanism of NIR Measurement

NIR operates within a wavelength range of approximately 700 to 2500 nanometers. This technique involves measuring the light scattered from or transmitted through a sample, allowing for quick determination of material properties. One significant advantage of NIR is that it requires minimal to no sample preparation and can evaluate multiple components in a single scan.

This non-destructive analysis approach makes NIR particularly suitable for analysing a wide array of food products.

Key Measurements in Food Testing

NIR spectroscopy is primarily employed to quantify key components in food and agricultural products, including:

• Protein levels
• Carbohydrates
• Moisture content
• Fats and oils
• Various polymers

In food manufacturing, NIR aids in assessing the quality of ingredients, additives, and stabilisers used for diverse purposes such as colouring, thickening, and flavour enhancement.

Commonly analysed substances include:

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

Insights Gained from NIR Measurement

NIR spectroscopy can reveal the concentration of various substances in food products by interpreting the unique infrared emissions from these compounds. The intensity of these emissions corresponds to the concentration levels of different components, such as moisture and fat content.

Different compounds display distinct infrared signatures due to specific molecular bonds that absorb wavelengths of infrared light.

NIR Measurement Techniques

There are two principal methodologies for NIR analysis: reflectance and transmission. The choice of technique depends on the type of food being examined.

• Reflectance involves measuring light reflected off the sample, providing insight into its absorptive properties.
• Transmission requires the infrared light to pass through the sample, measuring how much light is absorbed.

For example, transmission is particularly effective for whole foods to assess ripeness or detect defects, while reflectance is suitable for analysing whole grains.

Non-Destructive Analysis Capabilities

A significant challenge in food analysis is ensuring that testing does not impact the integrity of the sample. NIR measurement excels in non-destructive analysis, allowing for thorough evaluations of bulk food items, including grains, fruits, meat, and seafood.

This capability is especially beneficial in gluten screening for unprocessed grains, enabling comprehensive internal composition analysis without affecting the food items analysed.

Calibration and Accuracy in NIR

Accurate NIR measurements necessitate proper calibration of the devices. Calibration involves establishing a baseline by comparing initial infrared absorption data with reference analysis data, typically formulated into a mathematical equation.

Calibration techniques can include basic multi-linear regression (MLR) and advanced partial least squares (PLS) methods, depending on the specific food compound and the instrument used.

Despite the inherent variability in all analytical methods, NIR technology boasts an accuracy level approximately 1.5 times greater than the variability of the reference methods it utilises. Modern NIR devices leverage extensive databases and predictive equations to enhance accuracy in analysis.

Advancements in NIR Technology

NIR measurement technology continues to evolve, with the advent of portable, user-friendly devices. Handheld NIR analysers, like the Spectrolytic Oil Seed Analyser, provide convenient, precise analysis of both solid and liquid food samples.

These advancements facilitate large-scale analysis throughout the supply chain, from raw materials to finished products. The benefits of NIR include:

• Significant reduction in waste due to minimal sample preparation
• Elimination of errors associated with traditional laboratory testing
• Versatility across a wide range of food compounds
• Rapid analysis of multiple components
• User-friendly operation requiring no specialised skills

NIR spectroscopy plays a crucial role in modern food testing, offering a reliable, efficient, and non-invasive means of ensuring food quality and safety. Its application across various stages of food production underscores its significance in addressing the challenges faced by the food industry today. As technology progresses, NIR will likely become even more integral to maintaining food integrity and consumer confidence.