Moisture is a ubiquitous component in nearly everything in our world.
It is an essential part of the natural environment. From biological organisms like plants and animals to inanimate objects such as food, textiles and construction materials, moisture permeates almost every aspect of our daily lives.
The presence of moisture can significantly impact the physical, chemical and biological properties of materials. This can influence factors such as texture, stability, quality and durability.
Understanding and managing moisture content is crucial in numerous industries. In agriculture, food processing, pharmaceuticals and manufacturing, it plays a vital role in product integrity and performance.
So, how is the moisture content measured within these industries? In this blog, discover everything you need to know about non-contact moisture measurement using the science of near infrared (NIR) spectroscopy.
What Is Non-Contact NIR Measurement Technology?
NIR spectroscopy is a non-destructive analytical technique to analyse the composition of substances based on their interaction with near infrared light. It relies on the principle that molecules absorb and scatter light at specific wavelengths in the near infrared region of the electromagnetic spectrum, which spans from approximately 0.78 to 2.5 microns(µm).
This region of the spectrum contains lower-energy photons compared to visible light but higher-energy photons compared to mid infrared and far infrared radiation.
In NIR spectroscopy for moisture content measurement, it is crucial to choose specific wavelengths of NIR light for analysis. These wavelengths are carefully selected based on the properties of the target material and the desired sensitivity of the measurement.
Typically, two wavelengths are chosen:
- One wavelength is a reference wavelength and another wavelength is for measurement. The reference wavelength will not be absorbed by the sample material but instead serves as a stable reference mark for the measurement, as its intensity should remain relatively constant regardless of changes in the material’s properties.
- The second wavelength is chosen to specifically absorb moisture so that by measuring the level of absorption, you can determine the moisture content in the sample.
The choice of the specific measurement wavelength can be adjusted based on the expected moisture range in the sample. If the moisture content is expected to be high, a less absorbing NIR wavelength may be chosen to ensure the device has the required sensitivity. Conversely, for low moisture levels, a more sensitive NIR wavelength might be selected.
A white light source, which emits a broad spectrum of visible and NIR wavelengths, is used as the light source. This white light is then passed through an optical filter wheel, which contains a set of special optical filters. These filters are designed to selectively allow only the desired NIR wavelengths to pass through. The optical filter wheel rotates at a high speed (typically around 7,500 revolutions per minute) which allows for rapid switching between the different wavelengths of NIR lights. The specific wavelengths of light that have been determined as suitable for the intended application are pulsed from the device at a high frequency. As the NIR light passes through the sample, it interacts with it and the intensity of the light will be reduced due to absorption by water molecules. The reference wavelength, on the other hand, should remain relatively unchanged.
The device collects data on the intensity of light at both the reference and measurement wavelengths. By comparing the intensities and possibly using additional mathematical modelling or calibration curves, the device can calculate the moisture content of the sample. This approach allows for precise and rapid measurement of moisture content using NIR spectroscopy, making it valuable for quality control and monitoring applications in industries where moisture levels are critical.
NIR technology is a non-contact method of analysis, meaning materials can be examined without being altered or damaged. This is particularly useful when analysing a fast-moving manufacturing line or valuable or sensitive materials. NIR technology also offers the advantage of speed as NIR measurements can be performed quickly, often in real-time, allowing for fast decision-making.
The technology is also a relatively cost-effective system compared to other analytical techniques. The equipment tends to be relatively simple and compact, reducing the need for a complex set-up.
The Benefits of Non-Contact NIR Measurement
In the realm of moisture analysis, non-contact NIR technology stands out as a revolutionary method offering a myriad of advantages. From ensuring product quality to optimising manufacturing processes, NIR technology has transformed how industries measure and manage moisture content.
Non-destructive Analysis
NIR moisture analysis is non-destructive, limiting product waste. It also means there is scope for quick and repeated measurements without damaging any of the material being measured.
Energy Saving
Many products require drying during processing; this takes a lot of energy. Using an NIR gauge allows precise control of this and avoids over-drying, which can be detrimental to the product quality and wastes energy.
Real-Time Measurements
NIR measurements can be performed in real-time or near real-time, providing instant moisture content readings for quality control or process optimisation without the need to wait for lab results
Online or At-line measurement
The measurement of moisture can be done either on-line or at-line. In many manufacturing processes, the product will be transported on a conveyor belt above which an NIR moisture gauge can be mounted that will continuously measure the moisture content without contact. Alternatively, an at-line NIR gauge can be used where samples from multiple process lines can be taken for immediate moisture analysis.
Cost-Effectiveness
NIR moisture analysers are generally more cost-effective compared to traditional methods as they require minimal sample preparation and offer faster analysis times.
Real-World Applications of Non-Contact NIR Measurement
There are a considerable number of applications of NIR moisture measurement technology. As leaders in this technology provision, here are a few examples of how we have helped manufacturers keep moisture content at precisely the right level
Crisps (potato chips)
Moisture is a critical factor in determining the shelf life and quality of crisps. Too little moisture and crisps will be hard; too much, on the other hand, can cause crisps to lose their crunch. The right moisture level strikes a perfect balance with the fat and other ingredients, helping to prolong the shelf-life. Therefore, ensuring crisps remain fresh and tasty requires precise control over the moisture content during production.
Available at Control Metrix
Manufacturers achieve this by using NIR moisture gauges. Advanced food processing equipment such as the Nordson NDC Moisture Analyzer allows producers to maintain optimal freshness and taste by measuring moisture levels in real time.
When the NIR light reaches the crisps, they absorb some of it and reflect the rest. The light absorbed by the water molecules in the crisps depends on the moisture concentration, with high-moisture crisps absorbing more light than those with less water. Then, a detector measures the intensity of the reflected light, which is used to accurately, quickly and continuously calculate the moisture content of the crisps.
From here, manufacturers can adjust cooking times or temperatures to ensure optimised moisture levels, consistent quality and the right balance of crunch and flavour.
Related Reading: Crisp Secrets Revealed! Locking in Freshness and Analysing Oil and Moisture Content
Clay Bricks
Ensuring the right amount of moisture in the clay that is used for manufacturing bricks is essential for various reasons.
An accurate moisture level ensures better compaction and bonding of the clay particles, resulting in bricks with optimal strength and durability. Incorrect moisture content can lead to all kinds of defects such as warping, cracking, crumbling and blistering; overall, a weak and useless brick.
For brick manufacturers, there is a choice of NIR technology, either the PrediktIR for measuring moisture only or the Series 9, which measures both the moisture and the colour of clay or the finished bricks. These measurement tools ensure the manufacturer can offer their customers a truly consistent product.
There’s also an added benefit to brick manufacturers of using NIR technology as an integral part of their production line. By controlling moisture levels, brick manufacturers can reduce their energy consumption and environmental footprint by optimising the drying of bricks before the firing process. This means that alongside better quality bricks, there’s also a financial benefit of using NIR technology.
Coffee
Moisture measurement and control are critical at almost every stage of coffee processing. It is vital to ensure optimal product quality, taste, yield and operating efficiency. In a world where food yields from manufacturing processes have become ever more important, improved moisture control minimises production waste. Similarly to the brick manufacturing industry, it offers financial benefits through energy and time savings.
NIR technology is now used widely amongst coffee manufacturers, be they specialists in:
- Bean processing
- Coffee roasting
- Ground coffee
- Instant coffee
- Freeze-dried coffee.
The time saved by utilising an online NIR gauge is of enormous benefit. During production, moisture and colour are continuously measured in process. This means there’s no need to wait for the results of off-line sample moisture testing.
Alongside that, NIR readings are instant and continuous, meaning they will detect any variance and allow for corrective action to be taken. This helps to avoid any lost production or wastage. The non-destructive nature of NIR analysis minimises product waste even further as the entire production line is measured rather than taking periodic manual samples.
Related Reading: 5 Ways Moisture Measurement Supports Lean Manufacturing Methods
Moisture Management Made Easy with NIR Technology
As technology continues to advance, the applications of NIR moisture measurement are likely to expand further, providing even greater efficiency and accuracy to various industrial processes.
Many of our customers have benefited from this non-contact, real-time and cost-effective solution, enabling them to stay competitive, enhance product quality and reduce their environmental impact.
To learn more about NIR technology and the products available that can offer you a competitive edge through process optimisation, why not get in touch with one of our product specialists ?
Working with companies such as Birds Eye and Ibstock Brick, we are one of the UK’s leading suppliers of NIR technology and would be delighted to help.
For more information or to speak to one of our product specialists, get in touch today at hello@control-metrix.com or call us on 01823 761 309.
