The study – published in Food Chemistry – explored the possibilities of using commercial sugar beet pectin (SBP) for the stabilisation of anthocyanin-based blue pigments, by evaluating their potential use in low acid liquids and gelled food models.
The research team, led by Dr Dietmar Kammerer of Hohenheim University, Germany, found that SBP and a low molecular pectic polysaccharide fraction (PPF) isolated from sugar beet were suitable hydrocolloids for the stabilisation of anthocyanin- based soluble food colorants.
“The promising application of SBP and fractions thereof [PPF] as additives to anthocyanin-based food colorants has been demonstrated for the first time,” said Kammerer and his colleagues.
“However, further studies considering alternative anthocyanin sources, optimization of colour retention, interactions with other food ingredients and thermal processing aiming at the improvement of shelf life are still required,” they explained.
Until recently, synthetic colorants were commonly used in the food industry. However, recent studies’ linking certain artificial colours to health problems, coupled with increasing consumer demand for natural ingredients, has led to many manufacturers cutting out synthetic colours.
The recent Southampton study reported that consumption of mixtures of additives including sunset yellow (E110), tartrazine (E102), carmoisine (E122), ponceau 4R (E124), allura red (E129) and sodium benzoate led to increased hyperactivity in children.
As a consequence, since July 2010, the European Commission Directive 1333/2008 (EC) stipulates labelling of foods containing synthetic colorants with a warning.
However, in contrast with reds, yellows, and oranges, only few natural blue colorants are commercially available, say the researchers.
“Hence, substitution of synthetic colorants by their natural but less stable counterparts is a major challenge,” they noted, adding that data regarding the formation and stability of anthocyanin-based blue pigments suitable for food application “are scarce.”
In the new research, Kammerer and his team investigated the ability of sugar beet isolates to stabilise the colour shift of anthocyanins to a stable blue hue in model foods.
The researchers revealed that colour changes resulting from the addition of PPF to anthocyanin containing solutions were much more pronounced than in model solutions based on commercial SBP – noting that this may be due to higher contents of aluminium and iron which help to catalyse and stabilise the colour shift.
Systematic evaluations of the food models revealed that the colour shift and stabilisation effects strongly depended on anthocyanin purity and pH conditions.
“Highly purified anthocyanin extracts being devoid of colourless polyphenols and citric acid, exhibited strongest … shifts and moderate blue colour stability at pH 5.0 in model solutions containing PPF,” reported Kammerer and his co-workers.
They noted that citric acid hindered the formation of intensely blue coloured hues, and non-anthocyanin phenols with vicinal hydroxyl groups reduced the formation and stability of blue colours.
Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodchem.2011.12.034
“Characterization of sugar beet pectin fractions providing enhanced stability of anthocyanin – based natural blue food colorants”
Authors: M. Buchweitz, A. Nagel, R. Carle, D.R. Kammerer