Grape extract gives sourdough rye bread antoxidant shot in the arm, study

By Jane Byrne

- Last updated on GMT

The addition of a red grape by-product to sourdough mixed rye bread increased the antioxidant content of the increasingly popular bakery product but formulators need to ensure strict dosage control, finds new research.

Writing in the International Journal of Food Science and Technology​, the Polish researchers found that grape powder-enhanced sourdough mixed rye breads showed considerably higher dietary fibre contents than in the control, and had significantly higher antioxidant activity linked to their phenolic compound content.

However, the authors siad the hardness and gumminess of the supplemented bread significantly increased with the addition of the grape by-product and they recommend it be incorporated into rye bread formulations at a level of up to 6 per cent to ensure breads of acceptable quality.

Dietary fibre

The food industry, note the authors, are continually seeking new sources of dietary fibre (DF) as functional components as DF promotes beneficial physiological effects, including gastrointestinal function, moderation of postprandial insulin response and reduction in total and LDL cholesterol content.

According to the researchers, fruit DF are good sources of flavanols, flavonols, anthocyanins and phenolic acids. They have “better nutritive value than those derived from cereals, because there are also known to contain significant amounts of bioactive compounds such as polyphenols and carotenoids.”

Masking benefits

The team notes that sourdough fermentation allows for the addition of functional ingredients as it has a generally accepted role in improving both flavour and structure of rye and wheat breads and thus might be helpful in masking eventually negative effects of physiologically active plant ingredients on bread quality.

And, to their knowledge, no studies exist on the use of grape by-products as the source of both DF and polyphenols in the literature. Furthermore, said the authors, there is no documented research on the use of sourdough mixed rye bread as a matrix for bioactive compounds.

The study

Evaluating the effect of grape by-products (GP) on the chemical composition, soluble (SDF) and insoluble (IDF) dietary fibre, phenolic compounds, antioxidant activity (AA) and organoleptic characteristics of sourdough mixed rye bread, the team prepared samples of sourdough mixed rye bread: a control bread (BC) and breads with GP at four different levels: at 4, 6, 8 and 10 per cent.

The team said their results showed that the addition of GP significantly improves dietary fraction contents, as bread with a 10 per cent addition of GP accounts for 39 per cent and 37 per cent higher contents of IDF and SDF than the control.

“The assay of radical-scavenging activity and reducing ability showed that GP addition greatly enhanced antioxidant properties of mixed rye breads. Profiles of phenolic compounds of supplemented breads were dominated by procyanidin B1 and B2, catechin, epicatechin, caffeic acid and myricetin,”​ concluded the authors.

With an increase in the level of GP, the hardness and gumminess of the bread significantly increase, and, as such, sensory evaluation of GP-enhanced breads revealed that a maximum of 6 per cent GP could be incorporated “to prepare acceptable products.”

Source: International Journal of Food Science and Technology
Published online ahead of print: DOI:10.1111/j.1365-2621.2011.02643.x
Title: Use of grape by-product as a source of dietary fibre and phenolic compounds in sourdough mixed rye bread
Authors: S. Mildner-Szkudlarz, R. Zawirska-Wojtasiak, A. Szwengiel, M. Pacyński

Related topics Research Gut/digestive health

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