Meet the Expert
Who: Dan Hall
What: Product technologist
Where: Campden BRI
Colour is one of the most important sensory aspects of food and drink. As well as indicating likely freshness and flavour, it can also influence consumer choice and enjoyment of a product.
Colour and perceptions of flavour
Colour can affect the perception of flavour. In one study, the addition of red colouring to an otherwise clear solution was shown to reduce the detection threshold for bitterness. In another study, members of a consumer test panel incorrectly identified a cherry-flavoured beverage as having a lime flavour after it was coloured green.
Why does colour change over shelf life?
While artificial colours generally have a high tolerance to pH, light, temperature and oxidation, clean label colours can be less stable. Thermal processing used to sterilise and preserve food can have a big effect, as can the impact of natural UV light. If you understand the factors that affect natural colours during thermal processing and throughout the product’s shelf life, you will be able to achieve brighter and more stable colours without the need for artificial ingredients.
Measuring food colour
A consistent and objective approach to colour measurement is essential to determine whether a product’s colour changes after processing or throughout its shelf life. The chosen technique also needs to be suitable for the colour testing being undertaken. Chromameters and spectrophotometers are widely used for food colour measurement in the food industry.
Product images are also widely used as a visual reference when determining specifications for appearance, but care is required to ensure reliable colour reproduction. At Campden BRI, we use a DigiEye imaging system for this. The DigiEye is a digital imaging system that captures colour-calibrated images under standardised lighting conditions. It takes consistent images with precision, providing a faithful reproduction of the original product appearance. The DigiEye can also be used to describe the variations in colour of a product.
Case study: colour stability during shelf life
Maintaining colour stability and integrity during shelf life is one of the main challenges for surimi seafood stick manufacturers. Paprika and carmine can be used, but paprika can affect the taste, whilst carmine, which is derived from insects, can be controversial with consumers and causes product discolouration as it migrates into the white mass of the seafood stick.
Lycored approached us to help with shelf life trials. Our research showed that Lycored’s natural colour blends remain stable with little to no migration or fading in surimi seafood sticks for up to three months – much longer than other colouring options tested.
Lycored produces food colourings including Tomat-O-Red, which is made using lycopene extracted from tomatoes, and Lyc-O-Beta, which is made from beta-carotene. Lycored wanted to compare the stability of several different Lycored colours with other colouring options.
Campden BRI developed a method to compare 10 different colour blends on their manufactured surimi seafood sticks. These were then stored in chilled conditions and exposed to light levels significantly higher than typical food display conditions – simulating a ‘worst case scenario.’
The findings showed that the blends of Lycored’s Lyc-O-Beta and Tomat-O-Red colours remained stable, with minimal to no migration in the surimi seafood sticks for at least 66 days, and in some cases over 90, whereas the carmine and paprika samples all changed in colour and showed visible migration within 31 days. Colour stability and migration was measured using DigiEye imaging.