Agroscope Liebefeld-Posieux ALP
Milk and Meat Processing Research Area Culture Development Research Group
Project Status 2010
1. HNK-ES launched
In 2010, the process to produce the liquid proof-of-origin culture for Emmentaler AOC cheese culture (HNK-ES) was fully standardized. Additionally, the culture was applied in complex practical trials. On January 12, 2011, all Swiss Emmentaler cheese factories were supplied with HNK-ES for the first time ever.
The possibility of determining the authenticity of Emmentaler AOC cheese represents a milestone in the history of traditional cheese production in Switzerland. The proof is based on a molecular-biological method used to identify a specific part of the genome of the lactic-acid bacteria contained in the HNK-ES. The presence of this unique gene sequence in any given cheese verifies that the product is a genuine Emmentaler AOC. Therefore, in the future, imitated and original AOC Emmentaler cheese varieties can be easily identified and distinguished.
Emmentaler AOC proof-of-origin culture HNK-ES, in 90 ml and 60 ml bottles
2. New manufacturing
method for the MK410 Lyo
One of the main objectives of the Culture Development Project is to offer selected cultures in their preserved form.
Lyophilised (i.e., freeze-dried) cultures have proven to be particularly advantageous for both alpine cheese dairies and summer-pasturing farms, whose infrastructure is often very limited. Thanks to the development of a new lyophilisation method, the quality of the MK410 Lyo culture was successfully optimized and standardized. The culture – packed in sachets – is scheduled to be supplied to alpine farms in the Bernese Oberland beginning in July 2011.
Sachet of freeze-dried MK410 Lyo (does not correspond to original packaging)
3. Tracking down the butter flavor
To produce sour cream butter, cream is traditionally inoculated with a starter-culture, containing mesophilic lactic- acid bacteria. These bacteria are responsible for acidification and flavor formation. Their metabolic activity produces different volatile compounds typical for the fresh flavor of butter. Using GC-MS olfactometry, the flavor profiles of selected types of butter from Switzerland, and other countries, were investigated. In agreement with the literature, the results confirm that the flavor of butter is not only characterized by the presence of butyric acid and diacetyl, but also by the group of lactones in particular. Moreover, the results indicate that volatile sulphurous compounds also play a key role. In addition to these basic compounds, specific
flavor-active components account for the special character of butter. The influence of individual flavor components on overall flavor is currently being investigated in so-called recombination experiments. The aim is to be able to deliberately influence the butter flavor by selecting an appropriate starter culture.
Gas chromatogram and corresponding flavor profile of two selected butter samples
4. EPS-forming bacteria yield improved yoghurt texture
Texture is an important quality criterion for yoghurt. The use of exopolysaccharide (EPS)-forming lactic-acid bacteria is one way to deliberately influence the texture of yoghurt.
However, depending upon the cultured dairy product, it is important to insure that EPS formation does not venture too far into the ‘ropy’ or ‘slimy’ territory.
To comply with the concept of ‘Swissness,’ the cultures research group is working on a yoghurt culture of Swiss origin that also exhibits a thickening effect. Consequently, over 100 thermophilic lactic-acid bacteria from the ALP strain collection were tested in the laboratory for EPS formation. Initial application trials with selected EPS-forming strains also showed the desired effect on texture in yoghurt.
Capsule formation (light outline around bacterial chain) in a Lactobacillus delbrueckii ssp. bulgaricus strain
5. Strain collection:
Inhibition of clostridia
In accordance with the strong trend towards natural foods, the production as well as preservation of natural food products is becoming increasingly important. In the search for suitable organic preservation methods, the use of protective bacterial cultures is widely discussed as ways to, for example, inhibit product spoilage resulting from clostridia or prevent the growth of pathogenic germs, such as listeria.
Since selected lactic-acid bacteria can potentially form natural inhibitors, including bacteriocins, these bacteria are suitable components for a future protective culture. In 2010, as part of the development of a protective culture against clostridia, a screening was performed to laboratory-test the inhibitory effect of selected ALP strains of lactic-acid bacteria. The inhibitory effect was assessed using both a modified spot-on- the-lawn method and a turbidity test. The majority of the tested bacteria showed a, more or less, pronounced inhibitory effect on clostridia when the spot-on-the-lawn method was used. In contrast, the Lactobacillus acidophilus strains showed no inhibitory effect whatsoever. The turbidity test confirmed these findings. Moreover, Lactobacillus gasseri strains showed the strongest inhibitory effect on the Clostridium tyrobutyricum strains used.
Cheese trials are planned on the pilot-plant scale and the laboratory results will be tested under practical conditions.
0.0 1.0 2.0 3.0
4.0fresh milk boiled milk Diacetyl
sour cream nutty green oily
fruity cheesy sulphury
fungal
butter 1 butter 2
