Near-Infrared Spectroscopy (NIR) in the Dairy Industry

Introduction to NIR Spectroscopy

Near-Infrared Spectroscopy (NIR) is a powerful analytical technique used to measure the absorbance of light in the near-infrared region (780 nm to 2500 nm). It is based on the principle that molecular bonds in organic compounds absorb specific wavelengths of light in the near-infrared range. This absorption is related to the vibrations of molecules such as O-H, N-H, and C-H bonds, which are prevalent in organic materials, including dairy products. NIR spectroscopy is particularly valued for its speed, accuracy, and non-destructive nature, making it suitable for analyzing a variety of components in the dairy industry.

Value of NIR Spectroscopy in the Dairy Industry

1. Rapid and Non-Destructive Analysis: NIR spectroscopy enables real-time analysis without the need for complex sample preparation or destruction of the sample. This speed allows for in-line or at-line analysis during production processes, reducing downtime and increasing efficiency.
2. Cost-Efficiency: While initial investments in NIR equipment can be significant, the long-term savings from reduced use of chemical reagents, decreased labor costs, and minimal sample preparation make NIR spectroscopy a cost-effective solution for routine analysis.
3. Sustainability: NIR is an environmentally friendly method as it does not rely on chemicals or solvents for testing. This reduces waste and aligns with the increasing focus on sustainable practices in the dairy industry.
4. Multi-Component Analysis: NIR spectroscopy allows for the simultaneous measurement of multiple components, such as moisture, fat, protein, and lactose, in dairy products. This comprehensive capability streamlines quality control processes.
5. Real-Time Monitoring: The integration of NIR in production lines enables continuous monitoring, allowing producers to make adjustments in real-time. This can prevent wastage, enhance consistency, and optimize product quality.
6. Compliance and Quality Assurance: NIR technology helps dairy manufacturers meet stringent regulatory standards, as it offers highly accurate and reliable data. This is particularly valuable for compliance with food safety regulations, such as those from the FDA and EU, which demand precise measurement of nutritional and compositional content.

Applications of NIR Spectroscopy in Dairy

NIR spectroscopy is applied at various stages of dairy production, from raw milk analysis to finished product quality control. The technique can be used for:

1. Milk Composition Analysis: One of the primary applications of NIR spectroscopy in the dairy industry is the analysis of raw milk. NIR can quickly determine key components like fat, protein, lactose, and solids-non-fat (SNF) content. This information is crucial for producers to ensure the quality and consistency of the milk they receive and for pricing, as the payment to dairy farmers often depends on the composition of the milk delivered.
   • Fat Content: NIR can measure fat content with high precision, which is vital for products like cream, butter, and cheese.
   • Protein: Monitoring protein levels is critical for milk intended for cheese production, as it impacts the yield and texture of the final product.
   • Lactose: Lactose measurement is important for producing lactose-free or low-lactose dairy products.
2. Cheese Production: NIR spectroscopy is widely used in cheese manufacturing to monitor the composition of milk and the cheese-making process. During cheese production, controlling the moisture, fat, and protein content is essential to ensure the desired texture, flavor, and shelf life of the final product. It is a topic that deserves its own article. NIR can help:-
   • Monitor the coagulation process to optimize yield and texture.
   • Control the moisture content in cheeses like mozzarella and cheddar to achieve the desired consistency.
   • Assess fat-to-protein ratios, which influence the taste and texture of cheese.
3. Butter and Cream Analysis: Butter and cream manufacturers use NIR spectroscopy to monitor fat, moisture, and salt content. In butter production, ensuring the right balance between fat and moisture is crucial to producing a product with the correct spreadability and mouthfeel. NIR can rapidly assess:
   • Fat content in cream, ensuring the proper fat-to-water ratio in butter.
   • Salt levels in butter, which is crucial for flavor and preservation.
4. Yogurt Production: In yogurt production, the consistency, protein content, and moisture levels are key factors influencing product quality. NIR spectroscopy can provide real-time feedback on these parameters during the fermentation process, allowing manufacturers to:
   • Control the fermentation process by monitoring lactose content, which is consumed by bacteria to produce lactic acid.
   • Optimize protein levels to achieve the desired texture, especially in Greek yogurt, which requires a higher protein content.
5. Milk Powder Manufacturing: Milk powder is a vital product in the dairy industry, used as an ingredient in infant formulas, baked goods, and other food products. The production of milk powder requires precise control over the moisture and fat content to ensure product quality and shelf life. NIR spectroscopy is used to:
   • Monitor moisture content to prevent spoilage and ensure compliance with moisture specifications.
   • Control fat content, which influences the reconstitution properties of milk powder.
   • Detect any adulteration or contamination, ensuring product safety.
6. Dairy Ingredient Analysis: NIR is also used to analyze ingredients derived from dairy, such as whey protein concentrates, casein, and butterfat. The composition of these ingredients can vary, and NIR allows manufacturers to:
   • Measure the concentration of proteins and fats in whey powder, which is crucial for its use in sports nutrition and infant formula.
   • Assess casein levels, which are vital in the production of cheese and other dairy products.
7. Fermentation Monitoring: In cultured dairy products like yogurt and kefir, fermentation is a key process. NIR spectroscopy can monitor the levels of lactose and other sugars, as well as acidity (pH) during fermentation, enabling producers to optimize the process for flavor and texture development.
8. Adulteration Detection: The detection of adulterants in milk and dairy products is crucial for ensuring food safety and protecting consumer health. NIR can be employed to detect:
   • The presence of water or other non-dairy substances added to milk.
   • Substitutes like vegetable fats in products that should contain only milk fat.
   • Contaminants such as melamine, which caused a notorious food safety scandal in China in 2008.
9. Quality Control in Final Products: NIR spectroscopy is used in quality control to ensure that the final products, whether they are milk, butter, cheese, or yogurt, meet specified standards for composition, texture, and flavor. This includes ensuring the consistency of batches and detecting any deviations in moisture, fat, or protein content from the desired levels.

Examples of NIR Spectroscopy in Dairy Applications

1. Milk Fat Measurement: Several dairy processors employ NIR spectroscopy for the rapid determination of fat content in milk. For instance, a milk processor might use an in-line NIR system to measure the fat content as milk enters the production facility. If the fat content is too high or low, adjustments can be made on the spot, ensuring the milk meets specifications for products like skimmed or whole milk.
2. Cheese Production Optimization: During the production of cheddar cheese, a cheese manufacturer might use NIR spectroscopy to continuously monitor the moisture and fat content in curds. This allows the manufacturer to adjust the production process in real-time to ensure that the final cheese has the desired texture and flavor.
3. Yogurt Fermentation Monitoring: A yogurt producer might use NIR to measure lactose levels in milk before and during fermentation. As the fermentation process progresses, the lactose content decreases, and NIR provides real-time feedback on when the desired acidity and flavor profile have been reached.
4. Milk Powder Quality Control: A milk powder plant might use NIR spectroscopy to monitor moisture and fat levels in milk powder during drying. This ensures that the final product has a long shelf life and meets the moisture and fat content specifications required by customers.
5. Sugar Content In Dairy Foods: One project, the NIR4Dairy has been set up to quantify the lactose content in milk protein concentrate (MPC) and generate very high quality and repeatable spectra. That technology used a Near Infrared (NIR) transflectance probe connected to a Fourier Transform-Near Infrared (FT-NIR) instrument (Pu et al., 2021).

Suppliers of Inline NIR Analytical Equipment

A number of dairy plants are beginning to move to continuous inline technology for both process measurement and control. This is a critical step in the full automation of dairy plant.

The primary suppliers of inline NIR analytical equipment to the dairy industry include several companies known for their advanced technology and extensive industry experience.

1. FOSS: One of the leading suppliers of inline NIR equipment, FOSS offers the ProFoss™ 2 series, designed for continuous, real-time analysis of dairy products. This system is commonly used to monitor moisture, protein, and fat levels in products like cheese and butter, improving production efficiency and reducing process variation​ (FOSS Food Solutions).
2. Polytec: This company provides process spectrometers specifically tailored for food industries, including the dairy sector. Their NIR systems can measure fat, protein, lactose, and total solids in milk and dairy products directly within the production line​ (Polytec).
3. Q-Interline: Known for their DairyQuant GO and InSight Pro systems, Q-Interline specializes in fast and accurate FT-NIR technology for inline and at-line analysis. They cater to a wide range of dairy products, offering flexible solutions for butter, cheese, cream, and other dairy ingredients​ (Q-Interline).
4. Bruker Optics – Bruker provides several FT-NIR spectrometers tailored to dairy analysis, such as the MPA II Dairy Analyzer and the MATRIX-F II. These systems can handle a wide range of dairy products from milk and cream to cheese and yogurt. Their solutions are versatile, performing both in-line and at-line analyses for improved control throughout production.
5. Thermo Fisher Scientific – Known for its Antaris MX FT-NIR spectrometers, Thermo Fisher offers robust solutions for inline analysis. Their systems are used at a number of sites to monitor fat, protein, lactose, and solids in real time, optimizing production and ensuring that dairy products meet stringent quality standards. These spectrometers are used across various dairy processes, including milk, cheese, and yogurt production.

Inline technology is highly sophisticated but it only operates effectively if there is frequent calibration and adjustment and a dedicated team ensuring the system is maintained well. Unfortunately fouling is one of the main drawbacks when developing such a system.

Bruker developed the Matrix-F FT-NIR system to measure six points with 3-A probes in the process to measure fat, protein, casein, total solids (TS).

Fouling Of NIR Probes

 NIR probes in any food application are prone to fouling. When probes foul they produce biased spectra from which the wrong interpretation is made. Steps have been taken to overcome this phenomenon using antiadhesion coatings on the probes themselves which stops proteins, fats and calcium phosphate deposits adhering to the surface.

Manufacturers have also produced physical counter measures which include self-cleaning probes as well as designs with geometrical consideration. Physical measures include setting up air jets and water jets to routinely wash the window..

Another approach has been to build in a mathematical solution to window fouling by designing software to account for the loss of signal with time. Scheibelhofer et al., (2014) designed a software program which could determine the distance to particles in a hot-melt coating application for a fluidized bed. they found the part of the signal that went missing because of accumulation of coating on the probe window. They were able to monitor coating build-up on substrate particles even with the probe window being fouled.

The application of NIR spectroscopy in the dairy industry has revolutionized the way producers analyze, monitor, and control the quality of dairy products. Its value lies in its ability to provide rapid, accurate, and non-destructive analysis of critical components such as fat, protein, moisture, and lactose. By integrating NIR spectroscopy into their production processes, dairy manufacturers can improve efficiency, reduce waste, enhance product consistency, and meet regulatory requirements. As the dairy industry continues to evolve and face new challenges, NIR spectroscopy will remain an essential tool for maintaining high standards of quality and safety in dairy products.

References

Pu, Y., Marín, D. P., O’Shea, N., & Garrido-Varo, A. (2021). A methodological approach to acquire high-quality spectra on milk protein concentrate using a Near Infrared (NIR) transflectance probe. NIR News, 32(3-4), pp. 14-20

Scheibelhofer, O., Hohl, R., Salar-Behzadi, S., Haack, D., Koch, K., Kerschhaggl, P., Sacher, S., Menezes, J. C., & Khinast, J. (2014). Automatic correction for window fouling of near infrared probes in fluidised systems. Journal of Near Infrared Spectroscopy, 22(3), pp. 229-238 (Article).