Objective
Starter cultures play a crucial role in the fermentation of food products. Not only do they efficiently convert fermentable sugars in food materials, but in the same time they are responsible for a rapid decrease of the ambient ph. Both activities result in efficient protection against growth of undesirable microorganisms in the fermented product. An additional function of the starter organisms is generation of flavour compounds. These are produced, either as by-products during the sugar fermentation (i.e. Diacetyl, acetaldehyde) or as a result of the more gradual protein breakdown. This last process involves a variety of starter enzymes that are located almost exclusively in the cytoplasm of the starter bacteria. Since the activity of these enzymes is generally low, the whole proteolytic breakdown leading to flavour production is a very time-consuming operation. During this time, the starter bacteria will quickly exhaust their energy reserves and the precursors for flavour, peptides and amino acids, are not actively accumulated by the cells anymore. Flavour development can, theoretically, only proceed if the precursors can diffuse into the cells or, by far more likely, when the intracellular enzymes are released by Iysis of the starter bacteria. So, actual flavour development during ripening in fermented dairy products such as cheese can only occur as a result of lysis of the lactic acid bacteria. This project will determine the exact incidence and role of starter Iysis in several popular European cheese production processes. Furthermore, by increasing the incidence of starter lysis, accelerated ripening and improved flavour development will be two of the major achievements of this project.
This project aims to get complete control of the starter Iysis process by obtaining all the relevant scientific and practical data on this process. As starter organism we have chosen for lactococci, since they are the major starter organism in European cheese manufacture and physiology, metabolism and genetics are well described in these organisms. The whole Iysis process will be studied from molecular level to actual occurrence in cheese. On molecular level both the autolysis process and the bacteriophage-related Iysis will be studied on the level of (regulation of) gene expression, on the level of the cell wall-hydrolysing enzymes and on the level of the cell wall composition. For evaluation of lysis, practical and sensitive methods will be developed that will even allow analysis of starter lysis in situ, i.e. In cheese. Lysis efficiency will be compared in different starter cultures, under varying fermentation conditions and in different cheese making processes. The involvement of two cheese industries (Dairygold and Richemont) and three starter production companies (Christian Hansen, Texel and CSK) provides the possibility of R&D on industrial scale and guarantees direct implementation of the results for application. With this overall knowledge, it will be possible to effectively control and achieve increased Iysis of starters during the cheese manufacture and to produce starters with a desired efficacy of lysis. All the descibed objectives can only be achieved by bringing together the most active and succesfull European scientific groups within this research area. NIZO, RUG, UCC/DPC and INRA all have a fruitfull history in participation in previous EU-R&D programmes, in many cases already in some form of collaboration. By arranging a healthy collaboration with the above mentioned industrial partners, results with direct practical relevance are assured. Research on starter Iysis is a complete novel aspect within the EU-funding and will have great impact, not only on food science in general, but also on future developments in food fermentations other than dairy products.
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques.
- natural scienceschemical sciencesorganic chemistryorganic acids
- natural sciencesbiological sciencesmicrobiologybacteriology
- agricultural sciencesanimal and dairy sciencedairy
- natural sciencesbiological sciencesbiochemistrybiomoleculesproteinsenzymes
- engineering and technologyindustrial biotechnologybioprocessing technologiesfermentation
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Topic(s)
Call for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
6718 ZB Ede
Netherlands