How to measure the colour of fruit juice

How to measure the colour of fruit juice

Measuring the colour of fruit juice

Regardless of the type of fruit being harvested for fruit juice, the same principles apply for the end result. The juice produced at the end should be of consistently good quality, batch after batch. To be able to achieve this, quality, colour and appearance measurements should be among the tests completed during quality inspections. The appearance of the juice can be a key indicator of an issue during processing.

The stages at which measurements can be taken depend on the manufacturing processes for each type of fruit being processed for juice but as a general rule, at least one measurement should be taken of the final product before it is packaged.

The fruit can be measured right at the start before processing to make sure that there is no issue with the fruit itself as this would prevent any time or money being wasted on processing produce that was sub-par. The juice at the end of processing should also be analysed before being shipped to ensure the presence of a juice with all the characteristics it should possess. Of course, to be as accurate as possible, testing could be done after any additional ingredients are added. These measurements would ensure consistent quality all throughout processing. Depending on the ingredients added, these could also be analysed prior to use to make sure they are up to standard before they have any effect on the juice.

Taking measurements of colour and appearance at any stage needn’t be difficult but it does rely on an instrument that can excel at measurement of a great deal of samples and be comfortable with the difference in structure. An instrument would be needed that can accommodate opaque, translucent and transparent samples, in short, one would need an instrument that is capable of taking measurements of samples of varying physical characteristics.

The ColorQuest XE is a bench-top spectrophotometer that can measure reflectance, transmission and haze of solids and liquids, meaning that the liquid juice can be tested as well as the solid fruit before it has been processed. With the use of software, different standards can be set for a perfect example of fruit or juice and all subsequent samples can be compared to this. With EasyMatch QC software it is very easy to change from measuring the reflected colour of an opaque sample to the transmitted colour of a translucent or transparent sample.

A sample of the solid fruit can be prepared for measurement and placed at the reflectance port to receive the necessary data for quality tests. The fruit juice, however, may need to be measured in a different way, depending on its physical qualities. If the juice, such as some apple juice, ends up being transparent or clear in appearance, it will need to be tested in the transmission compartment of the instrument and the transmitted colour used for analysis. If the sample of juice 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 and backed with a white tile to ensure reflected data is received. The method for such measurements is similar for juice samples of any fruit so if the instrument is being used by a manufacturer of a variety of flavours, the method can remain the same. As stated, software is needed for keeping the data of all products and making comparisons of one batch to another. Once setups have been made for each product, it can be as simple as loading the sample, selecting the setup, reading the sample and receiving a pass or fail notification. This can be especially useful if the instrument is being used by operators that simply need to know if a batch is ok to ship. The ability to measure the haze of a product is also a helpful feature. Haze can be an indicator of the presence of impurities or error with filtration process so a haze measurement is another index worth using.

Whatever the purpose of appearance analysis, having the right tool for the job is a must. A versatile spectrophotometer that can accurately measure the reflected and transmitted colour of a sample and, with the use of easy to use software, provide comparisons between batches and pre-determined standards should make any quality control and production process a simple and cost-effective task.

Content Written by Rachael Stothard

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How to measure the colour of fruit juice

HunterLab ColourQuest XE Spectrophotometer

ColorQuest XE is a colour measurement spectrophotometer at an economical price. It can be used in production or in the laboratory for inspecting raw materials and evaluating finished product. Use it to measure opaque, transparent and translucent solids and liquids for properties such as reflected colour, opacity, strength, transmitted colour, APHA and haze.

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