Medium and low-fat mayonnaises usually require reduced oil content and increased starch content along with an emulsifier such as dairy protein or egg yolk.
Previous studies looking at the fat-replacing potential of beta-glucan, a non-starch polysaccharide found in oats and barley, reported that the glucan adversely affected the colour, flavour, and overall impression of the finished reduced-fat (RF) product.
While the researchers note that this is not the first time that beta-carotene has been used to colour low-fat mayonnaise and salad dressing, they do state that it is the first report the incorporation of both beta-glucan and carotenoids in the mayonnaise.
"Therefore, an improvement in colour of the RF mayonnaise containing beta-glucan could not only further increase the acceptability of the product but also possibly increase the extent of fat replacement by the beta-glucan," wrote Rujirat Santipanichwong and Manop Suphantharika from Mahidol University in Bangkok.
For many years, beta-carotene has been used as a food colouring, but growing knowledge about the health promoting antioxidative properties of carotenoids is pushing growth and applications for a range of these colourants, from lycopene to astaxanthin.
Market researchers BCC pitched the global market of all commercially used carotenoids to rise annually by 2.9 per cent for the next years, growing from $887 million (EUR722m) to $1 billion. The beta-carotene market at $242 million in 2004, a rise of $30 million on 1999, and representing over a quarter of the entire carotenoid market.
Writing in the Elsevier journal Food Hydrocolloids, the researchers report the results of testing beta-carotene or lutein in concentrations ranging from 25 and 75 mg/kg in reduced fat mayonnaise, prepared by replacing 50 per cent of the oil content with beta-glucan.
Santipanichwong and Suphantharika state that the colour characteristics of the reduced fat mayo samples were improved mainly by an increase in yellowness as a function of increasing colorant concentrations.
They also report that lutein appeared to destabilise the mayonnaise emulsion.
"On the contrary, the stability of the emulsions was almost unaffected by beta-carotene addition as evidenced by a greater decrease in the [storage modulus] value than the control only after a prolonged storage," they wrote.
The reason behind these observations, said the researchers, is that the lutein initially localised at the oil droplet's surface was spontaneously transferred to aqueous phase and destabilised the emulsions. On the other hand, beta-carotene was initially localised in the droplet's centre and needed longer time to be transferred oil droplet surface and then to the aqueous phase.
The colorants also had not effect on the overall textural properties of the reduced fat mayonnaise, compared to a full-fat control.
"Incorporation of both beta-glucan and carotenoids in the mayonnaise could provide both nutritional and health benefits and is appealing to health-conscious consumers," said the researchers.
Widely used as food colourings, carotenoids are organic pigments naturally occurring in plants. Their colour, ranging from pale yellow, through bright orange, to deep red, is directly linked to their structure: the double carbon-carbon bonds interact with each other in a process called conjugation.
Most of the carotenoids on the market are currently produced by chemical synthesis and partly by extraction from plant material. Fermentation does not yet play a role, although this method is expected to play a more important role in the future.
Source: Food Hydrocolloids Volume 21, Issue 4, Pages 565-574 "Carotenoids as colorants in reduced-fat mayonnaise containing spent brewer's yeast beta-glucan as a fat replacer" Authors: R. Santipanichwong and M. Suphantharika