Colour determination of nuts – from the raw material to the end product
The colour of nuts is an important indicator of their quality, freshness and processing. Since nuts are a natural product, their colour varies depending on the variety, origin, degree of ripeness and storage conditions. Colour changes can occur during production and processing for various reasons.
On the one hand, the different types of nuts naturally have different shades of colour. For example, hazelnuts are light brown to dark brown, almonds are creamy white without skin or reddish-brown with skin, walnuts can be light brown to dark brown with some gray or black spots, cashews are usually ivory to slightly yellowish.
On the other hand, colour changes also occur during processing:
- Drying
- After harvesting, nuts are often dried to extend their shelf life.
- This process can lead to slight darkening, especially when high temperatures are used.
- Roasting – too light or too dark, too short or too long?
- During roasting, natural sugars in the nuts caramelize, which leads to browning.
- Depending on the degree of roasting, the colour can vary from light golden to deep brown.
- The Maillard reaction (a chemical reaction between amino acids and sugar) also contributes to colour intensification.
- Seasoning & processing
- Salt, spices or caramel coatings can also change the colour.
- Honey or sugar glazed nuts often have a darker, shiny layer.
- The skin is removed from blanched nuts (e.g. almonds), making them appear lighter in colour.
- Storage & Oxidation
- Nuts can oxidize over time, especially if they are exposed to light, oxygen or moisture.
- This can lead to uneven darkening or the appearance of gray spots, which indicates a loss of quality.
Colour measurement for quality control of nuts
In summary, the colour of a nut depends on various factors, from the variety to processing and storage. A uniform, fresh colour is generally regarded as a sign of quality and leads to greater consumer acceptance.
Colour is an important quality indicator and is measured in the food industry using spectrophotometers. These devices, such as the Aeros spectrophotometer from HunterLab, enable objective and precise colour analysis, even for irregular surfaces such as nuts and other snack foods.
Read our application report “Colour measurement of nuts” to find out in detail how manufacturers and producers can ensure the colour of nuts, what the challenges are in sample handling and how HunterLab can support you with its product portfolio to determine your product colorimetrically.
Colour measurement of other nut products such as spreads
Manufacturers of spreads made from nuts, such as peanut butter, almond butter and other nut butters, face similar challenges. However, as the sample tends to be pasty, i.e. semi-solid and spreadable, but can become more liquid or solid with temperature fluctuations, other quality assurance requirements play a role.
Here, the colorimetry experts at HunterLab recommend either the new compact ColorFlex L2 colorimeter: the cream or paste is spread into a cuvette, placed on the device and measured. Or the Aeros measuring device can also be used here. Depending on the size of the opening of the end product container, the Aeros sensor can measure the sample in its packaging from above without contact.
Our experienced application engineers will advise you on which of the two variants to use. Contact the HunterLab Europe team, we look forward to hearing from you!
