Modern bread can keep for a long time – but it does not taste so good when it is old. New ingredients that can change this can be developed.
Many modern people do not have the time to bake or buy fresh bread daily. It is therefore a big relief to be able to buy bread that can last for days or even weeks. Even though bread that keeps for a long time does not dry out or get a furry, green mould growing on it the first two to three weeks, it can still get a somewhat strange taste after a while.
A recently completed PhD project carried out at the Faculty of Agricultural Sciences, Aarhus University, in collaboration with Copenhagen University and Novozymes has investigated why bread flavour deteriorates even though the bread keeps well otherwise and what can be done about it. The results from the studies can lead to commercial development of new ingredients that can be added to the bread to maintain its good flavour.
- Continual developments in baking technology have made it possible to produce bread in which microbial spoilage and textural changes are postponed considerably, says postdoc Sidsel Jensen from the Department of Food Science at the Faculty of Agricultural Sciences, who has carried out the bread studies.
- Other reactions in the bread, such as changes in smell, taste, and how the bread feels in the mouth, become the determining factors for how long the bread can keep, she continues.
Rancidity and off-flavour
Sidsel Jensen first looked at which processes in long-life bread affect taste, smell and other sensory qualities in bread. In her studies she used white bread and wholegrain bread. The bread was packed in bags and stored at room temperature for up to five weeks.
The results showed that evaporation and oxidation are the two most important mechanisms affecting the sensory qualities. Volatile compounds in the bread evaporate with the result that the pleasant bread aroma disappears. This also affects taste. Oxidation means that the fat in the bread turns rancid, which gives the bread an off-flavour.
- The wholegrain bread was particularly affected in a negative direction by long-term storage. This can have major practical importance because in the Western world the recommendation is to eat more wholegrain products instead of highly refined cereal products. Increasing consumption of wholegrain is said to have several health benefits, Sidsel Jensen points out.
The next step in the studies was to investigate if adding various additives to the bread can prevent rancidity and development of off-flavour. Rosemary extract, α-tocopherol and antioxidants were some of the things that were tried but none of them had sufficient effect.
- Addition of antioxidants is apparently not the easy way out of the problem, says Sidsel Jensen.
Concurrent studies have shown more promising results in connection with reducing the development of off-flavour in long-life bread.
- The results are still tentative and we cannot draw any final conclusions from these studies. More studies regarding off-flavour in long-life bread and in using new and untried ingredients, perhaps in combination with antioxidants, are necessary if we want to prevent the development of off-flavour in bread. Since the actual process of baking has been shown to have a great influence on oxidation, studies on and optimisation of the baking process may also lead to interesting and useful results, says Sidsel Jensen.
The PhD project was carried out in collaboration with Novozymes.
