A combination of enzymes and fermentation modifies bran structure and changes the bioavailability of the bioactive compound, according to new studies forming part of the European Union's large-scale HEALTHGRAIN project. Bioprocessing of bran has potential for making it a better ingredient for use in manufacturing nutritionally boosted cereal foods with high sensory quality.
The health benefits of whole grain and grain dietary fibre are well documented, and dietary reecommendations worldwide urge an increase in the intake of foods containing more of these healthy ingredients. The intake of both dietary fibre and whole grain foods is clearly less than recommended. This is in part due to the technological challenge of achieving sensory properties that appeal to consumers.
The presence of hard and strong-tasting outer grain layers (bran) containing most of the healthpromoting compounds demands new processing techniques to improve the quality of cereal food. Bread is a staple food consumed in large quantities throughout Europe, and is therefore a suitable food item for the purpose of increasing European grain fibre intake. The purpose of this study was to pre-treat cereal bran using bioprocessing techniques to make it better suited for baking bread. A further objective of using these bioprocesses was to improve the availability of healthy compounds of cereal bran, which involved a study of the effects of processing on the bioavailability of phenolic compounds.
The bioprocessing techniques studied included fermentation of wheat bran by using specific yeast and lactic acid starter cultures and enzymatic treatments using different cell-wall degrading enzymes. The most effective technique included a combination of cell-wall degrading enzymes and fermentation. Fermentation of bran with yeast prior to baking resulted in a higher bread volume and softer crumb of the samples of bread fortified with bran. Moreover, bioprocessing of bran by enzyme-aided fermentation increased the content of soluble fibre and the level of phytochemicals, the potentially bioactive compounds in bran. An increase was observed in the in vitro bioaccessibility of ferulic acid, the major phenolic acid in wheat, along with a change in the profile of its human metabolites. The significance to human health of these types of changes requires further study.
This way of bioprocessing of bran will create opportunities for making it a better ingredient for use in cereal foods, as well as in other food categories, thus aiding the manufacture of nutritionally boosted cereal foods (bread, biscuits, cereals, snacks, yoghurts) with high sensory quality.
Besides improvements in the technological quality and applicability of bran, the fact that bioprocessing changes both the amount and uptake of biologically active compounds in the body opens up new possibilities for tailoring the health effects of grain-based foods.