Peas have become an important source of protein, particularly in meat substitute products. However, controlling their undesirable beany flavour remains a major challenge. A team led by Christoph Denkel (food process technology) and Christian Trindler (aroma analysis) is investigating ways of controlling concentrations of undesirable aroma molecules in the first phase of protein extraction without compromising on protein properties.
Pea proteins are locally available and hypoallergenic, but are often limited in their use because of their "beany" flavour. The project investigated how targeted thermal treatments or physical methods can reduce undesirable flavour components. While thermal approaches achieved hardly any change in the flavour profile, a physical method reduced relevant flavour components by up to 90 %. Further tests are planned.
Translated with DeepL
Pea proteins are often used as a locally available, hypoallergenic source of protein. However, the isolates often have a typical inherent aroma, which is described as ‘beany’. Since this aroma is sometimes undesirable, it can limit the use of pea protein. Studies suggest that enzymatically catalysed fat oxidation processes based on lipoxygenase (LOX) activity make a significant contribution to the typical aroma, since some fat oxidation products are identical to molecules that are considered to be a characteristic component of a ‘beany’ aroma (Baysal and Demirdöven 2007). During fat oxidation, the fatty acids react with oxygen and break down into smaller molecules in subsequent reactions, which may be relevant to flavour.
From the scientific literature, it can be deduced that less flavour-relevant volatiles are formed by thermal inactivation of the LOX. However, thermal treatments can also lead to a change in the native protein structure, which in turn determines the techno-functional properties, whereby native protein properties are generally preferred. In addition, the protein isolation process apparently also leads to a strong accumulation of undesirable flavour components.
This project investigated whether and at which point in the protein extraction process a thermal treatment would reduce the formation of undesirable flavour components. Pea flour suspensions were heat-treated under different conditions (pH, temperature) and the effect on the concentrations of selected flavour components and the denaturation of the proteins was investigated. The heat treatments of the pea flour suspensions did not lead to the expected reduction in undesirable flavour components. Although LOX was reliably inactivated, there was no change in the flavour profile. The results suggest, on the one hand, that autoxidation plays a greater role than previously assumed compared to enzymatic oxidation, but on the other hand, other components remaining in the pea protein extract with regard to a fat-oxidising effect during storage should be included in future investigations.
The project also investigated a strategy for removing aroma components that had formed from the extract without thermally denaturing proteins. The physical method investigated can be applied in principle to all non-dry media. It was shown that the concentration of important lead molecules for a beany aroma profile could be reduced by up to 90% in some cases. The next step is to translate the method investigated in the laboratory into a continuous process and to examine the effects on the sensory properties in greater depth.
In the Food 4.0 programme, the Swiss Academies of Arts and Sciences, under the leadership of the Swiss Academy of Engineering Sciences SATW, support innovative project ideas that are at the very beginning of development. In particular, the programme supports projects that demonstrate new perspectives for the successful development of the Swiss food system. The selected projects make an important contribution to solving the greatest challenges and address the topics of food waste, sustainability and health.
