How to measure the colour of oil

How to measure the colour of oil

Measuring the colour of oil

With many different types of oil and oil of many different visual qualities, keeping a consistent level of physical characteristics can be a hard task, particularly for manufacturers that produce vast amounts of oil on a daily basis.

There are many different types of oil used in different types of industries made from a variety of different ingredients including vegetables, nuts and a mixture of chemicals for products such as engine oil and other industrial oils. Whether the end product is to be used in cooking, as a beauty product or as a mechanical lubricant, clarity and colour is an indicator of quality and this is precisely what can be measured to ensure a top quality product every time.

Most oils possess similar physical characteristics in that they are viscous liquids, more commonly than not in a yellow hue and with translucent qualities. As a result, the methodology for analysing oils does not differ significantly between oils made of different ingredients.

The stages for analysing colour and appearance depend on the processes of individual manufacturers but at the very least, a measurement should be taken of the final product before it is shipped to customers.

The Production Processes

Cold pressing: Oil produced in this way should be kept below 40°C to create an oil that is not as thick, has a lighter colour and is more nutritional. Hot pressing: Whilst yielding more oil from the seeds, the end product can be thicker and darker in colour than that of cold pressing.

What to measure

With these two methods, the end products have individual physical characteristics that make determining quality easier. The main indicator of a satisfactory production would be the colour of the oil at the end of the process. If using the cold pressing method, a darker colour oil could indicate an error in the process and a resulting high temperature that affects the quality of the oil.
Colour measurements can also be taken to ensure that UV light has had no effect on the oil, causing it to alter appearance and become undesirable.

Whether measuring coconut oil or walnut oil, vegetable oil or engine oil, the best quality should always be aimed for and, whatever the method, the oil produced should conform to the standard expected. A variety of different physical attributes can be analysed using different colour scales. For example, L, a, b, yellowness indices, haze, APHA and any other deemed necessary depending on individual manufacturer’s requirements and standards.

Different types of oil may need to be measured in a different way, depending on their physical qualities. If the oil, such as most oils used in the food industry, end up being transparent or clear in appearance, they will need to be tested using transmission measurements and the transmitted colour used for analysis.

If the sample of oil is translucent, that is one cannot see through it but can still determine light and some shape, then either transmitted or reflected colour can be measured. For measuring the reflected colour, the sample must be as thick as is able to ensure it is as opaque as possible to receive the most accurate results.

In order to receive the necessary data, an instrument should be used that can accommodate the type of sample needed for analysis. An instrument should be used that can measure the transmitted colour of a sample. For manufacturers that produce more than one type of consistency of oil, it may require both transmitted and reflected colour measurements. Having an instrument that can do both can allow for any changes in product or for the production of different products. Having an instrument that can accommodate both measurements can also allow for analysis at different stages of production; to ensure processes are working as they should, samples could be measured to make sure all seeds and oil are reacting the same.

As an example, a suitable instrument would be an UltraScan Vis Spectrophotometer. The certain characteristics to look for, evident in this instrument, would be both a reflectance port and transmission compartment to allow for both types of measurements. Accessories could be acquired that would allow for sample cells to be held at both transmission and reflectance ports, keeping the process as simple as possible.

With the combined use of this instrument with software, standards can be set that are the best representation of a perfect particular oil and operators can then compare samples from a batch to these standards. It can even be as simple as operators receiving a pass or fail notification to inform them if a batch is suitable to be shipped.

Whatever the product and whatever the need for appearance analysis, having an instrument that is capable of analysing a variety of samples and giving a range of data to suit individual needs is a must.

Content Written by Rachael Stothard

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How to measure the colour of oil

HunterLab UltraScan VIS Spectrophotometer

UltraScan VIS is a visible-range high-performance colour measurement spectrophotometer that measures the full range of human colour perception. It can be used in production and in the laboratory for inspecting raw materials, evaluating finished product or developing methods for colour analysis.

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