IITAA
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PROJECTS
Understanding lactic acid bacteria (LAB) potential: Nutritional benefits and safety advantages in cheeses
Food Science and HealthAgricultura e Produção Animal
2010 - 2013
Summary
This project aims at optimizing the production of cottage-type and soft cheese with new types of lactic acid bacteria (LAB), without chemical additives and with health promoting potential. This project will bring new, important, knowledge to the scientific community on the taxonomy, biochemistry and physiology of lactic acid bacteria, as well as on their role on the microbial ecology of cheeses. Raw milk may be considered as a potential risk food, as milk can contain several types of pathogenic and spoilage micro-organisms. Some of the fungi that contaminate cheese also produce carcinogenic mycotoxins that further deteriorate the cheese quality. Consumers and regulatory officials are becoming increasingly aware of the human health risk of the presence of micro-organisms or chemicals in the food products. LAB occur naturally in foods or are added as pure cultures to dairy products, and may produce a variety of antimicrobial compounds that have a broad activity spectrum against other species including Gram-negative bacteria (Hayes et al., 2007). The elimination of both pathogenic and spoilage microorganisms using natural means is a trend demanded by discriminating customers and the challenging criteria of nutritionists. Some protective LAB strains may also possess probiotic activity. Cheese is effective as a functional food and as a convenient vehicle for the introduction of probiotic cultures into the diet, because (in comparison with yoghurt and other fermented milk products,) it has a solid matrix, a higher pH and, buffering capacity, and greater fat content, all of which help protect the probiotic strain during intestinal transit to the site of action (Ross et al., 2002). Probiotic LAB ingested in the cheese may colonize the intestine and inhibit putrefaction caused by harmful bacteria, thus slowing the ageing process. Nutritionists also recommend cheese consumption for people with lactose intolerance, because most of the lactose is lost in whey during cheese manufacture and hence most cheeses contain only trace amounts of carbohydrate. The contemporary state of knowledge of LAB is considerably high; however studies of the antimicrobial and probiotic activities of LAB and are still far from being completed. Also, little is known about the molecular mechanisms of LAB protective characteristics. To accomplish this mission, the project will employ a wide range of methodologies targeted to obtain LAB with new qualities e.g. protective effect against pathogens and probiotics. The project will start to investigate technologically promising isolates of LAB present on local produced dairy products that may be used as starter or adjunct cultures in cheese production. After isolation of new LAB strains, evaluation of their activity against Listeria monocytogenes, Clostridium tyrobutyricum and spoilage micromycetes will be tested. Isolated LAB strains will be identified at molecular level. Procedures based on molecular biological methods will be also used, in the first part of the project, for testing qualities of LAB strains and their effectiveness towards target spoilage and pathogenic microorganisms. For transcriptomic analysis the RNA expression techniques (gene chip platform, real-time PCR etc.) are proposed. Total and secreted proteins will be compared between new LAB strain and the reference strains. Progressive proteomic methods (2D gel electrophoresis, MALDI-TOF mapping) will be included together with identification of molecular mechanisms of antimicrobial effects. We expect, that, among the project outcomes, will be elucidation of the molecular basis of antibacterial and antifungal efficacy of new LAB strains. In the second part of the project, more effort will be devoted to test technological and nutritional properties of new LAB strains. The protective and probiotic properties of new LAB strains will be evaluate. The immunostimulating activity of LAB will be determined by appropriate methods to assess the effectiveness of nutritive and health promoting properties of new LAB strains in real cheese products. Bioactive peptides will be purified from cheese produced by new LAB strains and identified by comparing their sequences with sequences of known bioactive peptides. With this approach we will gather knowledge on the structure of bioactive peptides produced by the LAB strains under study, having in mind the possibility of patent register. LAB tolerance to traditional starter cultures will be essential for future application in the dairy industry. We assume that laboratory-scale results will be verified in pilot-scale studies. Production of standard semi-hard and fresh cheese will be modified by the new LAB strains. We expected to achieve a prolongation of shelf-life in resulting cheeses, together with improved nutritional and organoleptic qualities. Finally, this project also contemplates the dissemination of the results to their potential end-users (decision-making groups, dairy industry, scientific community, general public).
COORDINATORS
Team
Funding Institution
Fundação da Ciência e Tecnologia (FCT)
Partners
Teagasc - The Agriculture and Food Development Authority (Teagasc)
