Understanding what happens in dough
Frozen pizza, ready-to-bake dough, wholegrain bread or pancakes – nowadays dough products not only have to be tasty, they also need to be more and more healthy, better quality and with improved preservability. When developing new formulations or products, the measurement of a variety of reactions such as the formation of gas caused by bacterial fermentation is a key issue. In cooperation with the Nestlé Research Centre, Dr. Helmut Trautmann with his company abiotec AG has developed a gas volume monitor for the analysis of dough samples. The monitor makes an important contribution to the development as well as to the quality assurance of food. In addition to being used in the food technology sector, the highly sensitive measurement device can also be used in the pharmaceutical and environmental sectors, for example in the field of biogas production. Dr. Helmut Trautmann talked to BIOPRO about the device developed by his company.
Dr. Trautmann, you have developed the gas volume monitor on behalf of Nestlé. What questions do the food technologists have and how can these questions be answered using your apparatus?
Nestlé carries out specific development activities for developing ready-to-bake pizza dough preparations in the form in which they are sold in supermarkets. This concerns both the dough recipe and the applied yeast strains. In contrast to conventional yeast doughs, which have a short fermentation time under warm conditions, the yeast strains we use manifest their gas formation activity very slowly under cool conditions and over a period of several weeks. In comparison to what happens during warm conditions, the speed of gas formation is reduced by several orders of magnitude. This reduced activity has a major influence on the shelf life of products. However, in order to be able to reliably assess diverse formulations, the developers depend on a very sensitive and long-term stable gas volume measurement technique. Commercial fermentographs are far from being able to fulfil these sophisticated requirements. The gas volume monitor developed by abiotec can complete all required tasks. The system is up to 1000 times more sensitive than traditional devices and is thus excellently suited for reliably measuring even minimal gassing activities.
In which other fields of application in the food industry can the device also be used?
There are many ways in which sensitive gas volume monitoring can be used, but I would like to highlight two specific applications, namely in the field of baker's yeast, and in the dairy industry. Yeast producers need to check their product quality, and the raising power of dough is one important quality criterion for any batch that is ready for sale. The yeast producers produce compressed yeast cubes for private households as well as user-friendly liquid yeast preparations that are transported to large-scale consumers in big tanks. In the latter case, the sales price is calculated based on the effective raising power rather than on the weight of the yeast. The exact and high time-resolved measurement of gas formation and related measurement sizes makes it possible for manufacturers to reduce the time currently needed for quality control activities and follow-up checks from one to two hours to around 30 minutes. This leads to a considerable improvement in the throughput of a quality control laboratory. At the same time, the increase in the number of key variables that can be measured make it possible to add further quality criteria and thus increase the reliability when assessing the quality of yeast batches. In this area, we primarily work with the Versuchsanstalt der Hefeindustrie e.V. (Institute of Fermentation Industries and Biotechnology) in Berlin.
And how can the dairy industry benefit from your development?
We have been working with a Swiss research institute for the last few months to test the system for its applicability in the dairy industry. It is known that the typical flavour and characteristic holes of Emmental cheese are the result of a CO2-producing secondary fermentative activity of propionic acid bacteria. This process occurs during the period that the cheese is left to mature in a cellar at a temperature of 5˚C during several months. This process has a considerable effect on the quality of the final product. Therefore, it is important to detect and counteract faulty fermentation processes. Our system can be used to effectively monitor the meticulous ripening process, as comparative tests with the CO2 measuring device that has been used up until now have shown. The monitoring process is also relatively inexpensive and the measurement set-up can easily be multiplied. We are currently expanding the range of the vials used to measure pressure through the addition of a big container into which whole small cheeses can be placed without needing to cut them into smaller pieces.
Which measurement principle does your system use and how big a piece of dough can be used for analysis?
The gas formed is determined in tightly closed units through a precise measurement of the absolute pressure that is stable over the long term. Minimal pressure changes are recorded by sensors during the measurement process and form the basis for calculating the volume of gas produced. When a definable pressure threshold is surpassed, a magnetic valve adjusts the pressure to the environment, at which point the integrated measurement is continued. This principle enables gas formation to be determined at any (sea-level) site and in any weather conditions with the minimum likelihood of failure. The basic device was designed for small amounts of dough (between 10 and 200 g). However, we have already manufactured containers for larger sample amounts on demand - so we have practically no limitations.
How does the device provide information about processes in the dough that change over time?
The measurement set-up not only determines a number of discrete measurement points, but also provides us with a high-resolution measurement curve over time, which allows differentiation between bioyeasts and "normal" yeasts, for example. We can also use the device for baking ferments, which are used to prepare starter doughs and which enable dough processing over long time periods. These natural processes were once standard practice in the preindustrial area when sour dough was used to prepare bread. Such processes usually involve a blend of lactic acid bacteria and yeast and result in bread that can be digested more easily and has a better aroma, taste and shelf life. This is why such breads are becoming more popular again at the moment. They also have better characteristics in terms of nutritional physiology. The monitoring of gas formation in doughs that are left to rise for longer periods of time reveals that a moderate amount of gas is produced at the beginning of the fermentation process, increasing considerably over time. We can also identify polyauxic processes, i.e. the stepwise adaptation of organisms to changing culture conditions, which also leads to stepwise gas formation activity. Pattern recognition then enables the automated detection of interesting patterns.
How can your gas volume monitor help to increase the shelf life of food and how can it help to monitor quality control?
Food decay is often the result of microbial activities. The metabolic processes associated with food decay often lead to the formation of gas. When these processes have been going on for quite a while, inflated packages are a clear indication that the product inside is no longer edible. The early stages of these processes of decay often present only a small number of effects. The formation of gas can also sometimes be preceded by a short phase of gas consumption. We were recently able to show this effect in yoghurt with initial mould attack.
The purely physical online measurement method also allows real-time statements to be made about the underlying reaction kinetics. We therefore envisage that our system will be able to complement time-consuming and selective offline laboratory tests, and maybe at a later stage replace them completely.
How do the fermentative behaviour and metabolic activities at low temperatures (near freezing point) differ from those at higher temperatures (45˚C)?
Like all biochemical reactions, fermentation reactions are also temperature-dependent: Normally, the reaction rate increases exponentially with rising temperatures. This applies for temperatures up to 37° C in normal yeast dough: the warmer it is, the faster the gas formation takes place. At higher temperatures yeasts soon become thermally damaged. This is why for example short-term stress tests with yeasts to simulate a longer storage time are carried out at 45˚C.
The gas volume monitor can also be used in the pharmaceutical and environmental sectors. Can you give me some examples?
Any biochemical reaction that leads to the formation or consumption of gas can be monitored. The device can be used in the alternative energies and environment sectors to measure biogas production or in the field of wastewater management to determine the amount of dissolved oxygen needed by aerobic organisms to break down organic material (BOD; milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20° C) as a measure of the degree of organic pollution of water. I believe that the gas volume monitor can also be applied in the pharmaceutical industry to test the gas tightness of metered-dose inhalers and to monitor the changes of compounds. It can also be used for a sensitive detection of changes in substances and preparations that are sensitive to oxidation. In addition, the device is also suitable for measuring purely physical effects that are based on gas sorption and desorption phenomena. The concept is basically open to all kinds of applications. Additional application ideas from research and industry - including unusual ones - are always welcome.
abiotec AG - advanced bioprocess technologies
Dr. Helmut Trautmann, CEO
Tel. +41 56 633 11 77
Fax +41 56 633 11 84