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IMPROVING THE QUALITY OF EUROPEAN HARD CHEESES BY CONTROLLING INTERACTIONS BETWEEN LACTIC ACID BACTERIA AND PROPIONIBACTERIA

Objective



The manufacture of over 800.000 tons of highest quality hard/semi-hard cheese in Europe is very much dependent on precise control of the propionic acid fermentation during cheese maturation. Specific strains of propionic acid bacteria (PAB) are responsible for the development of the characteristic eyes in cheeses such as Emmental, Gruyere, Comte, Leerdamer, Maasdamer, etc. PAB play on important role in the formation of aroma in these cheeses and in hard italian cheeses (Grana, Padano, Parmigiano Reggiano). During ripening these bacteria convert the lactates, produced by the starter lactic acid bacteria (LAB), to propionate, acetate and C02. The C02 collects in weak pockets in the cheese curd leading to eyes formation and the propionic acid contributes strongly to the final cheese flavour. Though extremely important, the PAB have not attracted a great deal of research attention and most of the published work on these bacteria has been done with pure cultures. In cheeses however, the PAB must establish a successful symbiosis with the starter LAB. The starter bacteria provide the energy substrate in the form of lactates which the PAB ferment to propionate, acetate and CO2.
The objectives of this project are :
1- to clarify the relationshipsbetweenthe starter LAB and the PAB in the cheese
environment,
2- to determine the factors wihich permit selection of strains of LAB and PAB such
that they interact in a beneficial symbiosis which affords a predictable
consistent propionic acid fermentation in the cheese environment,
3- to define the conditions which bring about a cessation of the propionic acid
fermentation when it has developed to optimum, characteristic of a particular
cheese,
4- to identify combinations of LAB and PAB which are ideal for the manufacture of
specific propionic acid cheeses, leading tohigh quality cheeses,
5- to identify LAB strains which are antagonistic to PAB so as to curtail their
development in cheeses in which the propionic acid fermentation causes
an openess defect.
Organisation of the project :
* Refinement of a model system which simulates as far as possible the cheese
environment,
* Identification of beneficial symbiotic combinations of PAB and LAB,
* Identification of LAB generally antagonistic to PAB, useful for Italian hard cheeses,
* Idenfification as far as possible of the factors responsible for the beneficial and
antagonistic reactions in 3 and 4 respectively,
* Establishment of the significance of the model system by testing the beneficial
combinations of PAB and LAB identified in the model system, in pilot plant and
commercial Emmental-type cheese making. Industrial partners will participate to
these trials,
* Establishment of the significance of the model system by testing LAB identified as
antagonistic to PAB in Italian cheesemaking trials,
* Characterisation of the PAB and LAB strains being used in the project so as to
establish a bank of strains which can be used by cheese makers to make
specific cheese varieties.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

INSTITUT TECHNIQUE DU GRUYERE
Address
Rue De Saint-brieuc, 73 - B.p. 6224
35062 Rennes
France

Participants (6)

AGRICULTURAL UNIVERSITY OF ATHENS
Greece
Address
Iera Odos Str., 75
118 55 Athens - Votanikos
BESNIER BRIDEL
France
Address
Rue Adolphe Beck, 10
53089 Laval
Consiglio Nazionale delle Ricerche (CNR)
Italy
Address
Via Celoria 2
20133 Milano
ENTREMONT S.N.C.
France
Address
B.p. 7 - Foveno
56140 Malestroit
UNIVERSITY COLLEGE CORK
Ireland
Address
Western Road
Cork
VALIO LTD.
Finland
Address
Meijeritie, 4 - P.o. Box 390
00370 Helsinki