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Polar charges may play important role in aroma release: Study

By Nathan Gray , 14-Jan-2011

The polar charges of food ingredients may play an important role in the retention and release of aroma compounds in a food matrix, according to new research.

The study, published in Flavour and Fragrance Journal, investigated the effects of different thickening agents (pectin and carrageenan) on the release of thirteen aroma compounds; finding that whilst carrageenan has little effect on aroma release compared to water, the polar effects of pectin lead to altered aroma release.

“The nature and the amount of the different components in the food matrix, such as lipids, proteins and polysaccharides greatly influence aroma retention and thus aroma perception,” said the researchers, led by Dr Anne Tromelin from the Université de Bourgogne, France.

“This result highlights that ι-carrageenan does not modify the nature of interactions between aroma and water molecules, but suggests that interactions with pectin are somewhat different,” they added.

By better understanding the way components of a food matrix influence aroma release, they suggested that it may be possible to optimise consumers sensory perceptions of food products through reformulation.

Sensory properties

Tromelin and colleagues said the acceptability of foods by consumers is highly governed by their sensory properties – among which aroma perception plays an important role.

In order to be perceived during the consumption of food, aroma compounds first have to be transferred from food to a gas phase, and secondly must reach olfactory receptors, said Tromelin.

The researchers said that aroma compounds are found in the gas phase in a concentration that depends on their gas/matrix partition coefficient. This coefficient varies depending on both the aroma compound and the composition and the structure of the food matrix.

They said that because many aroma compounds are hydrophobic, the presence of lipids highly influences the partitioning of aroma compounds. They also noted that polysaccharides can lead to the retention of aroma compounds within a food matrix.

However, few studies have reported the molecular interactions involved between aroma compounds and polysaccharides such as pectins and carrageenans – which are commonly used as thickeners in foods.

The new study investigated the effects of pectin and carrageenans (specifically ι-carrageenan) on aroma release in comparison to water.

Study details

The release of 13 aroma compounds was analysed in pure water, ι-carrageenan and pectin gels.

“Our present aim was first of all to identify some relevant structural properties related to the retention and then to propose a qualitative interpretation,” said the researchers.

Tromelin and co workers reported that release of the aroma compounds was the same in all three media, and from computational modelling described a repulsive effect based on positively charged surface areas between aroma compounds and water or polysaccharide gel.

“Our results highlight the role of polar effects on the retention of odorant molecules, and suggest that retention/release properties are not determined by the chemical classes but by an assembly of chemical properties,” concluded the researchers.

Source: Flavour and Fragrance Journal
Volume 25, Issue 6, pages 431–442, doi: 10.1002/ffj.2000
“Retention–release equilibrium of aroma compounds in polysaccharide gels: study by quantitative structure–activity/property relationships approach”
Authors: A. Tromelin, Y. Merabtine, I. Andriot

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