Making delicious cereal foods still better
In addition to wheat-based products, the flavour of oat and rye products may be optimised by using sophisticated processing methods.
Bread and cereal products made from oat and rye flour are healthy and they taste good, especially when they are fresh. The flavour of these products results from a mixture of many different volatile compounds. These compounds develop mainly during fermentation of the dough and through heat reactions during baking. They can be analysed best by a combination of sensory analysis and gas chromatographic methods. Bread flavour is a very delicate characteristic that changes and degrades during storage.
In cereal products made from oat flour some of the volatile compounds are positively perceived. However, many of them will soon disappear and other, undesired off-flavours will develop. Due to the high lipid content of oats, slightly bitter or rancid off-notes will affect the flavour.
The typical strong and slightly bitter flavour of rye bread is formed during the processing. Sourdough fermentation is the most common processing method for rye. Not all consumers in Europe are familiar with the resulting relatively intensive flavour, however. Therefore, in some regions this style of bread is less popular. Raija-Liisa Heiniö, a researcher in flavour composition and modification at VTT Biotechnology in Espoo, Finland, states: "Presumably the rye consumption in Europe would increase, if the specific rye-like flavour could be slightly modified to have a milder taste, without decreasing the high fibre content and other positive health effects of rye".
- milling fractionation (a milling process where the kernel is separated into endospermic, shorts and bran fractions)
- sourdough fermentation
- germination and subsequent heat treatment processes
- extrusion cooking (a continuous process using both temperature and pressure to expand the kernel)
Germination and the subsequent heat-treatment process have a major influence on the sensory profile of oats. The germinated oats dried at high temperatures were identified as being roasted, sweet, and nutty. These characteristics were clearly related to such volatile compounds as dimethyl sulphides and isobutanol. Significantly, there was no apparent Maillard reaction. Phenolic compounds had a considerable influence on the oat flavour, whereas lipids had a negligible effect. The accumulation of free fatty acids and volatile compounds caused by lipid oxidation were closely correlated with the development of undesired sensory attributes.
Flavour components in rye grain are unevenly distributed. Even after extrusion the difference in the flavour of sourdough-fermented rye still varied to a great extent from geminated rye. Depending on the wheat to rye ratio, the most important factors affecting the identity and acceptance of rye bread were the acidity and the salt content.
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