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Measuring and managing the production of consistent quality pet foods with NIR

Article reproduced with permission from Ben Helm, Commercial Manager at Premier Pet Nutrition

Ben Helm considers the challenges for pet food manufacturers faced with variations in the raw materials used to manufacture consistent and palatable pet food and discusses the uses and benefits of NIR to help achieve consistent quality pet food through accurate, quick and repeated measurement.


Pet food manufacturers produce pet food from a range of raw materials. By their nature, raw materials vary in their composition and quality between deliveries – even when harvested from the same field. This is to be expected and is a feature of the normal biological variation, even in commodity items such as cereals and grains.

A typical dry pet food might have up to 20 different raw materials which are specified in the formulation to achieve a final pet food that must meet the declared levels. There are permitted tolerances across declared parameters to reflect both the variability in raw materials – but also the agreed tolerances within the methods of analysis. Even so, these are small margins and represent a constant challenge for pet food manufacturers.

Pet food manufacturers who produce consistently excellent food deserve great respect when you consider the variations in raw materials they must use to manufacture pet food that is consistent in appearance, performance and palatability. Ultimately, it is the pet (and most likely the cat!) that will detect any changes between batches of a pet food. But the manufacturer must know before the food is packed that it meets all of the quality criteria.

So how does a pet food manufacturer manage to achieve such consistency with the goal posts of raw materials moving while the target is set in stone on the label of every pack? And how do they know they are achieving the target specification in real time? They are able to manage their raw materials and production methods to achieve consistency and conformance by measuring key parameters of their incoming ingredients and finished pet food. It is only possible to manage something if you can measure it – accurately, quickly and repeatedly.

How does a pet food manufacturer ‘measure’ raw materials and pet food?

Pet food manufacturers operate with limited raw material stores (for efficient use of space and inventory) and so cannot afford the luxury of taking delivery, quarantining raw materials, sampling and then sending samples away for external analysis that may take several days to complete. Raw material suppliers will deliver to an agreed specification (with tolerances) – for example, meat and bone meal will be supplied with minimum and maximum protein and ash levels. Raw materials will also be supplied with a certificate of conformance – but this does need to be verified, or the finished pet food may not conform to target. Making non-conformant pet food is expensive, wasting raw materials, factory time, energy and even packaging. A pet food manufacturer then has the task of making the batch again to meet the delivery date, assuming you have sufficient raw materials in stock. So there’s really only one viable option – get it right first time, which means measuring the quality of your raw materials.

On-site analysis

Due to the need for real-time verification of the quality of incoming raw materials and finished pet food, most pet food manufacturers use NIR (Near Infrared Reflectance) as their preferred method of analysis. This is quite a remarkable technology that is able to be operated by non-technical staff to give reliable, accurate and speedy analysis of both incoming raw materials and finished pet food. It is a proven technique for rapid, on-site multi-component analysis of raw materials and pet foods. Samples require little or no preparation, making NIR a quick, clean and chemical-free way of analyzing for key quality parameters in pet food. The NIR system is ideal for rapid analysis and it lowers the cost of achieving quality, being able to increase testing frequency at no extra cost. A busy pet food manufacturer may use an NIR 100 times a day to measure multiple samples of ingredients and dry pet food.

There are 2 key parts to a successful NIR system: Hardware & software.

NIR Machine.

An NIR machine delivers the light at the required wavelength onto the sample and records how much light is absorbed by the material. There are different makes of NIR machine available (Bruker, Buchi, Foss, Perten, Thermofisher, Unity etc) – each producing light within 350nm and 2500nm, with some covering wider spectra than others and using different methods of analysis. When irradiated by energy, the chemical bonds in a molecule (raw material, dry pet food) vibrate at a frequency characteristic of that bond. These vibrations can be accurately related to nutritional, chemical and physical properties. So when a sample is placed on the NIR machine, it produces a spectrum (or fingerprint) that represents that sample.


Software is then required to interpret what that fingerprint represents – typically a quantitative analysis of the sample, although qualitative analysis is also used at times to verify that a sample is as expected eg. Sampling single Vitamins and Minerals. This relies on a calibration factor that then relates the fingerprint from the NIR to a result of a wet chemistry analysis. The greater the number of calibrations, the more accurate the analysis. So once an NIR machine is calibrated well, anyone can operate the machine, confident in it delivering instant and accurate results.

The more common parameters measured using an NIR machine will include: protein, oil, fibre, ash and moisture content of both raw materials and dry pet food. This gives the pet food manufacturer the information required on raw material and pet food quality, enabling them to make the decision on how to adapt, amend and proceed in a way that will enable them to hit their target.

3 new pet food NIR innovations

1. Cook Value.

The Cook Value calibration measures how well a dry pet food has been cooked, stating the level of starch gelatinisation (%). The cook level of a pet food affects its palatability and digestibility and the new calibration informs the pet food manufacturer instantly how well a pet food has been cooked. It also provides instant feedback to the extruder operator if they are putting too much or too little energy into the pet food – offering significant energy cost savings at the extruder. Previously, measuring cook value has meant lengthy and costly wet chemistry analysis, with results often arriving days after the pet food has been packed. With this new calibration, it is now available at the push of a button.

2. Peroxide Value (PV)

PV is a measure of the level of oxidation in fats in a pet food which has a massive influence on the palatability and shelf-life of a dry pet food. By measuring the PV using NIR it is now possible to assess quickly how oxidised the fats are and if the palatability or shelf-life are going to become issues for that batch of pet food. Using NIR to measure PV now saves both time and money compared with conventional PV analysis methods.

3. Water Activity (aw).

Water activity is one of the most critical factors determining the quality and safety of a dry pet food. If it is too high, the dry pet food will mould and spoil due to microbial growth. The new aw calibration gives instant feedback on how likely a pet food is to spoil once packed.

NIR is limited to detecting certain levels, below which it cannot deliver reliable results. For example, Mycotoxins, which are the by-product of mould growth on cereals and can be toxic to pets at certain levels occur in the ‘parts per billion’ level so NIR cannot be used reliably to measure them. So pet food manufacturers must still rely on easy-to-use desktop wet chemistry kits to measure them in incoming cereals.

What next?

An NIR machine does represent a significant investment and as the majority of progressive pet food manufacturers own one, it is clear how it is seen as a vital piece of equipment to help achieve consistent quality pet food. An NIR machine is also a massive resource and opportunity for a pet food manufacturer (with the appropriate calibration factors) to be able to test for new parameters that have previously been impractical due to the expense and time involved. I believe that in 5 years time, we will have seen an explosion in the use of NIR to test for novel parameters, enabling pet food manufacturers to put further pressure on suppliers to deliver consistent raw materials and to make even better quality pet food for the market.

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