Classifications

• • A—HUMAN NECESSITIES
  • A21—BAKING; EDIBLE DOUGHS
  • A21D—TREATMENT, e.g. PRESERVATION, OF FLOUR OR DOUGH, e.g. BY ADDITION OF MATERIALS; BAKING; BAKERY PRODUCTS; PRESERVATION THEREOF
  • A21D8/00—Methods for preparing or baking dough
  • A21D8/02—Methods for preparing dough; Treating dough prior to baking
  • A21D8/04—Methods for preparing dough; Treating dough prior to baking treating dough with microorganisms or enzymes
  • A21D8/047—Methods for preparing dough; Treating dough prior to baking treating dough with microorganisms or enzymes with yeasts
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N1/00—Microorganisms, e.g. protozoa; Compositions thereof; Processes of propagating, maintaining or preserving microorganisms or compositions thereof; Processes of preparing or isolating a composition containing a microorganism; Culture media therefor
  • C12N1/14—Fungi; Culture media therefor
  • C12N1/16—Yeasts; Culture media therefor
  • C12N1/18—Baker's yeast; Brewer's yeast
  • C12N1/185—Saccharomyces isolates
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12R—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES C12C - C12Q, RELATING TO MICROORGANISMS
  • C12R2001/00—Microorganisms ; Processes using microorganisms
  • C12R2001/645—Fungi ; Processes using fungi
  • C12R2001/85—Saccharomyces
  • C12R2001/865—Saccharomyces cerevisiae

Definitions

• the present invention relates to new strains of baker's yeast, also called baker's yeast, performing on sugar-free pasta and slightly sweet pasta.
• yeast strains A glucose repression system for the expression of the genes encoding maltopene and maltase is observed in yeast strains termed "slow strains".
• a reference baker's yeast strain used by the Applicant Company for many years is the strain deposited at the NCYC (National Collection of Yeast Cultures) under the number NCYC995.
• NCYC National Collection of Yeast Cultures
• This strain which is the subject of US Pat. No. 4,396,632, makes it possible in particular to produce baker's yeasts with excellent growth yields.
• a rapid strain the level of induction of maltase activity in the presence of maltose and the fermentative strength of strain NCYC995 are not optimal compared to those of other yeast strains which are, however, slow strains and / or which are not suitable for applications on sugar-free or slightly sweet dough.
• the strain deposited on March 22, 2000 at the CNCM under the number 1-2412 has a high level of induction of maltase activity in the presence of maltose, but it is a slow strain that does not is not suitable for breadmaking on sugar-free dough.
• yeast strains which rapidly ferment the sugars by non-repression of the maltase activity in the presence of glucose and / or an induction of the maltase activity in the presence of optimal maltose, said strains having a strength fermentative improved.
• the subject of the invention is therefore strains of Saccharomyces cerevisiae deposited on August 21, 2007 with the CNCM under the numbers 1-3796, 1-3797 and 1-3798, the strains derived from these strains, the strains obtained by cross-breeding or transformation. by mutation or genetic transformation of the strain (s) above.
• the invention also relates to baker's yeasts that can be obtained by culturing a strain above and baker's pasta containing these yeasts which are according to one embodiment unsweetened or slightly sweetened.
• the invention also relates to a process for preparing bakery dough comprising a yeast fermentation step according to the invention, and the baking process, as well as the bakery product thus obtained.
• the invention also relates to a novel method for selecting yeast strains of breadmaking.
• Figure 1 shows repression of maltase activity in the presence of glucose and induction in the presence of maltose.
• the blank histograms represent the maltase activity in nmol of p-nitrophenol released per minute and per mg of proteins under repression conditions and the histograms in gray under induction conditions, for each strain tested: the strain of NCYC995, the slow osmotolerant strain NCYC996, the 3 slow strain CNCM 1-2412 and the strains according to the invention deposited at the CNCM under the numbers 1-3796, 1-3797 and 1-3798.
• the present invention provides new breading yeast strains having a maltase activity induction level in the presence of maltose and / or a fermentative force better than the reference strain deposited under the number NCYC995, while maintaining non-suppression maltase activity in the presence of glucose characteristic of a fast strain and / or good yields during the production of yeasts (typically a yield greater than or equal to 90% of the yield obtained with strain NCYC995, preferably greater than or equal to at 95%, still preferably greater than or equal to 98%).
• the new yeast strains according to the invention make it possible in particular to obtain yeasts having an improved fermentative activity.
• the advantages of the strains according to the invention are particularly apparent when the baker's yeasts obtained by culturing said strains are used as a fermentation agent in sugar-free or slightly sweet pastes, and optionally containing a mold inhibitor such as an organic acid. low and / or one of its salts.
• the yeast strains, object of the invention were obtained by crosses of strains having different profiles of induction of maltase activity in the presence of maltose and suppression of the maltase activity in the presence of glucose, the objective being to select the strains having the best level of induction in the presence of maltose, a non-repression in the presence of glucose characteristic of a fast strain and the ability to produce yeasts with a good yield, said yeasts having a fermentative force greater than that of yeasts from the reference strain of the applicant company filed under the number NCYC995.
• the sporulation and crossover program was carried out using standard techniques, such as those taught in Chapter 7 "Sporulation and Hydridization of Yeast” by RR Fowell, in the reference book “The Yeasts”, Volume 1, edited by AH Rosé and JS Harrison, 1969- Academy Press.
• yeast strains according to the invention are then selected on the following criteria:
• the preselection of the strains after culture on molasses plate makes it possible to eliminate the strains having a yield too low compared to the reference strain and / or a fermentative force too weak compared to the reference strain. Indeed, the molasses plate culture is more easily implemented than a semi-continuous culture.
• a selection of the preselected strains is carried out on the same criteria, namely the yield and the fermentative force, but after a semi-continuous culture.
• the level of induction of maltase activity is defined here as maltase activity in the presence of maltose and in the absence of glucose.
• maltase activity under induction conditions implies the presence of maltose and the absence of glucose.
• the level of suppression of maltase activity is defined here as maltase activity in the presence of glucose and in the absence of maltose.
• maltase activity under repression implies the presence of glucose and the absence of maltose.
• a level of non-repression of the maltase activity better than the reference strain deposited under the number NCYC995 corresponds to a maltase activity in the presence of glucose greater than that of said reference strain.
• the maltase activity in the presence of maltose yeast strains according to the invention is preferably increased by at least 20%, especially at least 30%, especially at least 40%, especially at least 50%, and especially at least 60%. % compared to that of strain NCYC995.
• the maltase activity in the presence of glucose of the yeast strains according to the invention is greater than or equal to 50%, in particular greater than or equal to 70%, in particular greater than or equal to 90% of that of the strain NCYC995.
• the maltase activity in the presence of glucose of the yeast strains according to the invention is increased by at least 10%, preferably at least 20% and more preferably at least 30% relative to that of strain NCYC995.
• the maltase activity can be measured by assaying the release of a colored product, p-nitrophenol, following the action of maltase on a chromogenic substrate, p-nitrophenyl- ⁇ -D-glucopyranoside, as described in Houghton-Larsen and Anders Brandt, Appl. About. Microbiol., 2006, p 7176-7182.
• the yeasts are incubated, in particular for 4 hours, in a medium containing glucose for the measurement of the suppression of the maltase or maltose-containing activity for the measurement of the induction of maltase activity. maltase activity.
• yield is meant yeast growth yield.
• the yield is obtained by making the ratio of the mass of yeast produced on the mass of sugar consumed.
• the yield can be evaluated after culture on molasses plate or fed-batch culture, as described in the reference book “Yeast Technology", 2nd edition, 1991, G. Reed and TW Nagodawithana, published by Van Nostrand Reinhold, ISBN 0-442-31892-8.
• the strains according to the invention make it possible to produce yeasts with a yield greater than or equal to the yield obtained with the strain NCYC995.
• the fermentative force corresponds to the volume of CO 2 (in ml) produced by the fermenting yeast in dough pieces of flour.
• the fermentative force is measured by conventional techniques known to those skilled in the art, in particular by means of a fermentometer as described by Burrows and Harrison in “Journal of the Institute of Brewing", Vol 65, 1959.
• the force fermentative is measured according to tests described in EPO5111O8 and
• the fermentative force reflects the fermentative activity of glucose, with the understanding that maltose and sucrose are always fermented as glucose or fructose.
• the fermentative force can be measured on yeasts obtained by culture of strains on molasses plate or semi-continuous culture (fed-batch).
• the fermentative force is preferably measured on fresh yeasts.
• the fermentative force of the yeasts obtained after culture of the strains according to the invention on a molasses plate is greater than or equal to that obtained with the strain NCYC995.
• the fermentative strength of the yeasts obtained after semi-continuous cultivation of the strains according to the invention is preferably increased by at least 10%, especially at least 14%, 008/001193
• the yeast strains according to the invention make it possible to produce high performance yeasts on sugar-free or slightly sweet pastes, with or without addition of mold inhibitors, such as weak organic acids and / or their salts.
• a sugar-free dough is a dough in which no sugar has been added. In sugar-free dough, the sugars present come from the flour.
• lightly sweet dough refers to doughs having an added sugar content of less than or equal to 12%, in particular less than or equal to 10%, in particular less than or equal to 6%, in particular less than or equal to 5%, in particular lower or equal to 3% by weight relative to the mass of the flour.
• the sugar is preferably added as sucrose.
• the yeast strains according to the invention make it possible to produce baker's yeasts having a fermentative activity greater than that of yeasts resulting from the strain NCYC995, in the presence or absence of at least one mold inhibitor.
• the fe ⁇ nentative activity can be evaluated in breadmaking by a measurement of the proof time.
• Primer time is a measure commonly used in the field of breadmaking. It is defined as the time required for the baking dough to reach a certain height in the mold corresponding to the development of the desired dough so that it is placed in the oven.
• the primer time measured in different panary recipes, is decreased.
• the yeasts obtained from the yeast strains according to the invention have a drying resistance. Yeasts resistant to drying make it possible to obtain dry yeasts.
• Drying is preferably fast drying in the presence of an emulsifier.
• An emulsifier is in particular sorbitan monostearate at 1, 5%.
• the drying resistance of yeast is defined by a fermentative activity greater than or equal to 70% of the fermentative activity before drying, at constant solids, the fermentative activity being measured with the Burrows and Harrison fermentometer in the Al tests. , A'1, A3, A'3 (in tests A3 and A'3, addition of 2 g of sucrose compared to Al and A '1 tests) and under the drying conditions described in documents EP0511108 and US5741695.
• the strain of Saccharomyces cerevisiae deposited on August 21, 2007 with the CNCM under the number 1-3796 exhibits in particular the following characteristics: a maltase activity in the presence of maltose increased by at least 50% compared with that of the NCYC995 strain, 8 00H93
• the strain of Saccharomyces cerevisiae deposited on August 21, 2007 with the CNCM under the number 1-3797 has in particular the following characteristics: a maltase activity in the presence of maltose increased by at least 60% compared to that of the strain NCYC995, - a maltase activity in the presence of glucose increased by at least 30% compared to that of the strain NCYC995, during the production of yeasts, a yield greater than or equal to 90% of the yield obtained with the strain NCYC995, after plate culture of molasses, a fermentative force of the yeasts on sugarless paste greater than or equal to that of yeasts originating from the strain NCYC995, and after semi-continuous cultivation, a fermentative force of the yeasts increased by at least
• the strain of Saccharomyces cerevisiae deposited on August 21, 2007 with the CNCM under the number 1-3798 exhibits in particular the following characteristics: a maltase activity in the presence of maltose increased by at least 30% compared with that of the strain NCYC995, a maltase activity in the presence of glucose greater than or equal to 50% of that of strain NCYC995, - during the production of yeasts, a yield greater than or equal to 90% of the yield obtained with strain NCYC995, after culture on molasses plate, a fermentative force of the yeasts increased by at least 10% on sugar-free pulp compared to that of yeasts resulting from the strain
• the present invention relates to the three strains described above and all strains belonging to the same family, that is to say all the strains that share the same properties as the three strains described above, as well as all strains that can be derived from this family of strains, and in particular the three strains deposited.
• the present invention particularly relates to a strain of Saccharomyces cerevisiae derived from a strain as defined above, said derived strain being characterized by: a maltase activity in the presence of maltose increased by at least 20%, in particular at least 30%; % relative to that of the strain NCYC995, and / or - a maltase activity in the presence of glucose greater than or equal to 50% of that of the strain NCYC995, and / or during the production of yeasts, a yield greater than or equal to 90% of the yield obtained with the NCYC995 strain and / or after culture on a molasses plate, a fermentative force of the yeasts on sugarless paste greater than or equal to that of yeasts originating from the strain NCYC995, and / or after semi-continuous culture, a fermentative force of the yeasts on sugar-free pulp increased by at least 10%, especially at least 14% relative to that of yeasts originating from the strain NCYC995, and / or after semi-
• the invention also relates particularly to a strain of Saccharomyces cerevisiae derived from a strain as defined above, said derived strain being characterized by: a maltase activity in the presence of maltose increased by at least 20%, in particular at least 30%; %, in particular at least 40%, in particular at least 50%, in particular at least 60% relative to that of the NCYC995 strain, and / or a maltase activity in the presence of glucose greater than or equal to 50%, in particular greater than or equal to 70%, in particular greater than or equal to 90% of that of strain NCYC995, and / or during the production of yeasts, a yield greater than or equal to 90% of the yield obtained with strain NCYC995, preferably greater than or equal to 95%; %, still preferably greater than or equal to 98%, and / or after culture on molasses plate, a fermentative force of the yeasts greater than or equal to that of the strain NCYC995, and / or after semi-continuous cultivation, a
• a strain derived from the 1-3796 strain is preferably characterized by: a maltase activity in the presence of maltose increased by at least 20%, especially at least 30%, especially at least 40%, especially at least 50% relative to NCYC995, and / or a maltase activity in the presence of glucose greater than or equal to 50% of that of strain NCYC995, and / or - during the production of yeasts, a yield greater than or equal to 90% of the yield obtained with the strain NCYC995, preferably greater than or equal to 95% and / or after culture on molasses plate, a fermentative force of yeasts on sugar-free pulp increased by at least 10% compared to that of strain NCYC995, and / or after semi-continuous cultivation, a fermentative force of the yeasts on sugar-free pulp increased by at least 10%, in particular at least 14% relative to that of the stump.
• a fermentative force of yeasts on slightly sweet dough increased by at least 10%, especially at least 14%, especially at least 18%, especially at least 22%, especially at least 26%. % compared to that of yeasts from strain NCYC995.
• a strain derived from the 1-3797 strain is preferably characterized by: maltase activity in the presence of maltose increased by at least 20%, especially at least 30%, especially at least 40%, especially at least 50%, especially at minus 60% relative to that of the strain NCYC995, and / or a maltase activity in the presence of glucose greater than or equal to 50%, especially greater than or equal to 70%, in particular greater than or equal to 90% of that of the strain.
• a yield greater than or equal to 90% of the yield obtained with the strain NCYC995 and / or - after culture on molasses plate a fermentative force of the yeasts on sugar-free dough greater than or equal to with that of strain NCYC995, and / or after semi-continuous cultivation
• a fermentative force of the yeasts on sugar-free pulp increased by at least 10%, in particular by at least 14%, in particular by at least 18%, in particular by at least 22% , in particular at least 26% in relation to that of the strain NCYC995, and / or after semi-continuous cultivation
• a fermentative force of the yeasts on a slightly sweet dough increased by at least 10%, especially at least 14%, especially at least 18%, especially at least 22%, especially at least 26% compared to yeasts from strain NCYC995.
• a strain derived from the 1-3798 strain is preferably characterized by: a maltase activity in the presence of maltose increased by at least 20%, especially at least 30% relative to that of the strain NCYC995 and / or a maltase activity in the presence of glucose greater than or equal to 50% of that of strain NCYC995 and / or during the production of yeasts, a yield greater than or equal to 90% of the yield obtained with strain NCYC995 and / or - after culture on molasses plate a fermentative force of the yeasts on sugar-free pulp increased by at least 10% compared to that of the strain NCYC995, and / or after semi-continuous cultivation, a fermentative force of the yeasts on sugar-free pulp increased by at least 10 %, in particular at least 14% relative to that of the strain NCYC995, and / or - after semi-continuous cultivation, a fermentative force of the yeasts on a slightly sweet dough increased by at least 10%, especially at least 14%, in particular
• derived strain is meant a strain derived from any transformation whatsoever, such as for example by one or more crosses and / or by mutation and / or by genetic transformation.
• a strain derived by crossing can be obtained by crossing a strain according to the invention with the same strain, or another strain according to the invention, or any other strain, for example the strain NCYC995.
• a mutation-derived strain may be a strain that has undergone at least one spontaneous mutation in its genome or at least one induced mutation, for example by mutagenesis. The mutation (s) of the derived strain are silent or not.
• mutagenesis is meant both conventional mutagenesis obtained by radiation, for example by the use of UV, or by mutagenic chemical agents and insertional mutagenesis by transposition or by integration of a fragment of Exogenous DNA.
• Radiation mutagenesis includes the use of UV, X, or gamma radiation.
• the mutagenic chemical agents are, for example, EMS (ethyl-methyl sulfonate), 1ES (ethyl ethyl sulfonate), nitrosoguanidine, nitrous acid, Aflatoxin B1, hydroxyl amine, 5-bromo-uracil, 2-amino-purine , proflavine, acridine orange.
• a strain derived by genetic transformation is a strain into which exogenous DNA has been introduced.
• This exogenous DNA is preferably provided by a plasmid or integrated directly into the genome.
• the invention is further directed to methods of transforming a strain as defined above, said method comprising a step of transforming said strain by mutagenesis or by genetic transformation.
• the present invention relates to strains obtainable by the transformation method defined above.
• the present invention also relates to a novel process for selecting bread-making strains which comprises an original combination of steps and which makes it possible to quickly select yeast strains having the desired profile.
• the Applicant Company has demonstrated that industrial yeast strains have maltase activity profiles that are very different from each other, both under induction and repression conditions.
• the first has an induction level in the presence of very low maltose (much lower than that of the fast strain NCYC995), whereas the level of induction of second is very high (see Figure 1).
• the Applicant Company has demonstrated that a selection process comprising a step of selecting the strains on the basis of the maltase activity makes it possible to select strains which give yeasts with an improved fermentative activity.
• This selection step on the basis of the maltase activity consists in selecting strains whose maltase activity is weakly repressed in the presence of glucose and strongly induced in the presence of maltose.
• the selection process according to the invention allows, in addition, the selection of yeast strains of bread making which have a good yield.
• the present invention thus relates to a method for selecting improved bread yeast strains comprising the following steps: a stage of sporulation and hybridization of yeast strains and / or mutagenesis of yeast strains, to obtain strains of yeast hybrid and / or mutated, a first step of selection of hybrid and / or mutated strains which have: maltase activity in the presence of maltose greater than that of the strain
• NCYC995 and o maltase activity in the presence of glucose greater than or equal to 50% of the maltase activity of the NCYC995 strain, to obtain strains with improved maltase activity, possibly a preselection step, among the strains having an activity.
• yeasts which have: a yield greater than or equal to 90% of the yield obtained with the strain NCYC995, and a fermentative force greater than or equal to that of the strain NCYC995, and a second step of selection, among the strains having an improved maltase activity and / or the strains obtained in the preceding step, strains giving, after semi-continuous culture; , yeasts which show: o a yield greater than or equal to 90% of the yield obtained with the stump
• NCYC995 and o a fermentative force greater than that of the NCYC995 strain, to obtain improved bread yeast strains.
• the mutagenesis of yeast strains is in particular carried out by the techniques described above.
• the mutagenesis is a mutagenesis using UV radiation or using EMS.
• Mutagenesis using UV radiation is, for example, carried out by preparing a culture of the strain to be mutated. The cell culture is then washed before being resuspended in a buffer, for example a 0.9% NaCl solution. The cell suspension is then subjected to UV shocks, for example a radiation of 400 J / cm 2 , depending on the survival curve of the cells. The culture having undergone UV shocks is then spread on nonselective medium and each colony obtained corresponds to a mutated strain.
• UV shocks for example a radiation of 400 J / cm 2
• the selection method advantageously comprises a preselection step.
• This preselection stage is based on an original culture mode of the strains on molasses plates. This step saves considerable time in the selection process. Indeed, the molasses plate culture being more easily implemented than a semi-continuous culture, a larger number of hybrids can be tested over a short time.
• the first selection step comprises the selection of the hybrid and / or mutated strains which have: a maltase activity in the presence of maltose increased by at least 20%, in particular at least 30%, in particular at least 40%, in particular at least 50%, in particular at least 60% relative to that of the NCYC995 strain, and / or o a maltase activity in the presence of higher glucose or equal to 70%, especially greater than or equal to 90% of that of strain NCYC995, and / or the second selection step comprises the selection of strains giving, after semi-continuous culture, yeasts which present: o a fermentative force on sugar-free and / or slightly sweetened pasta increased by at least 10%, in particular by at least 14%, in particular by at least 18%, in particular at least 22%, in particular at least 26% relative to that of strain NCYC995, and / or o a yield greater than or equal to 95% of the yield obtained with the strain
• NCYC995 preferably greater than or equal to 98%.
• the subject of the present invention is also a strain of Saccharomyces cerevisiae that can be obtained by the selection methods as defined above.
• the subject of the present invention is also a strain of Saccharomyces cerevisiae derived from a strain that can be obtained by the selection methods as defined above, said derived strain being characterized by: a maltase activity in the presence of increased maltose at least 20%, in particular at least 30% relative to that of the strain NCYC995, and / or a maltase activity in the presence of glucose greater than or equal to 50% of that of the strain NCYC995, and / or during the production of yeasts, a yield greater than or equal to 90% of the yield obtained with the strain NCYC995 and / or after culture on molasses plate, a fermentative force of the yeasts on sugarless paste greater than or equal to that of yeasts originating from the strain NCYC995 and / or after semi-continuous cultivation, a fermentative force of the yeasts on sugar-free pulp increased by at least 10%, especially at least 14% relative to that of yeasts originating from the strain NCYC995 , and / or
• the invention also relates to baker's yeast obtainable by culturing strains as defined above, derived strains and transformed strains.
• baker's yeasts advantageously have, at the industrial stage: a yield greater than or equal to 90% of the yield obtained with the strain NCYC995, preferably greater than or equal to 95%, still preferably greater than or equal to 98%, and / or drying resistance greater than or equal to that of strain NCYC995, and / or a baking time that is lower than that obtained with baking yeasts originating from strain NCYC995.
• the baker's yeasts according to the invention are produced from yeast strains as defined above, in particular as described in the reference book "Yeast Technology", 2nd edition, 1991, G. Reed and TW Nagodawithana, published by Van Nostrand Reinhold, ISBN 0-442-31892-8. R2008 / 001193
• the manufacture of baker's yeasts generally comprises at least the first two steps and the last stage of all of the following steps: multiplication of a pure strain of baker's yeast in several stages, first in semi-anaerobiosis, then aerobically, - separation by centrifugation of the baker's yeast thus produced from its culture medium, with obtaining a "liquid yeast cream” containing between 12 and 25% of dry matter, or even a higher amount of dry matter if the yeast cream is mixed with osmolytes products, filtration of the liquid yeast cream thus obtained, generally on a vacuum rotary filter and obtaining a fresh dehydrated yeast containing from 26% to 35% of dry matter blending said dehydrated fresh yeast in order to obtain a homogeneous mass, extruding the yeast thus obtained and obtaining a yeast pressed under the fo rms of fresh yeast or crumbled fresh yeast bread, marketed at about 30% solids content, or, if the yeast is to be dried, in the form of particles, generally granules, optionally
• the subject of the present invention is a baker's yeast as defined above, obtained by culturing a yeast strain according to the invention with adaptation to the presence of weak organic acid.
• the adaptation of the yeasts according to the invention to the presence of weak organic acid is especially carried out during their last stage of multiplication by known methods, such as the process described in US Pat. No. 4,318,991, with the addition of 0 1 g to 10 g of short-chain aliphatic carboxylic acids, such as aliphatic carboxylic acids with 2, 3 or 4 carbon atoms, and / or their salts, per liter of must.
• This process of adaptation to the presence of weak organic acid can optionally be combined with a process of the type described in US Pat. No.
• molasses batch in which, during the last yeast multiplication cycle, a casting is applied.
• discontinuous batch being preferably formed by brief interruptions, for example: molasses castings for 5 to 10 minutes followed by casting interruptions of 5 to 10 minutes.
• Bakery yeast can be a yeast selected from yeast creams, pressed yeasts and dry yeasts. 93
• Creams of yeast, pressed yeasts and dry yeasts are obtained in particular by the process as defined above.
• Fresh bakery yeasts are characterized by high water content compared to dry yeasts.
• Fresh bakery yeasts include yeast creams and pressed yeasts.
• Yeast creams are aqueous suspensions of yeast cells having a cream-like viscosity.
• yeast cream preferably bakery, it comprises a liquid suspension, typically an aqueous suspension, living yeast cells preferentially bakery, said suspension having a preferred dry matter content of at least 12% by weight and generally between 12 and 50% by weight (extended definition of yeast cream).
• the cream of liquid yeast meets the definition of yeast cream in the strict sense, that is to say that it has a dry matter content of between 12 and 25% by weight, and even more preferably between 14 and 25% by weight. and 22% by mass.
• the present invention is also useful for creams of yeast preferably bakery with higher solids content, that is to say at least 25% by weight, such as in particular the creams of yeast bakery said to high density containing one or more osmotic agents, such as for example polyhydroxy food compounds and food salts.
• yeasts pressed in compact block also called "yeast breads", characterized by a water content of 65% to 74%, and pressed yeasts in granules characterized by a water content of 63% are distinguished. at 69%.
• Dry yeasts are characterized by a low water content, especially less than 8% water.
• Dry yeasts include active dry yeasts and instant dry yeasts. Active dry yeasts are yeasts that must be rehydrated in warm water before use.
• the present invention more particularly relates to a baker's yeast as defined above, characterized in that the yeast is a dry yeast, preferably an instant dry yeast.
• Bakery yeasts according to the invention are suitable for use in a paste at room temperature and / or a cold paste.
• a paste at room temperature here denotes a paste at a temperature of 22 ° C to 28 ° C, especially 24 ° C to 26 ° C.
• a cold paste here denotes a paste at a temperature greater than or equal to 15 ° C and strictly less than 22 ° C, especially a paste at a temperature of 17 ° C to 18 ° C. 8 00H93
• Bakery yeasts according to the invention are suitable for use in pasta without sugar or slightly sweetened.
• the baker's yeasts obtained with the strains according to the invention can be particularly interesting in bread-making processes of the direct pattern type (NO-TIME DOUGH) and of the indirect pattern type ("SPONGE and DOUGH”) with pastes without sugar or slightly sweetened, with or without mold inhibitor. Their use is however not limited to the specific applications mentioned above and hereinafter.
• a "NO-TIME DOUGH” scheme or “direct scheme” has practically no first fermentation between intensive kneading and the division of the dough, the dough pieces obtained being fermented in a mold between 35 0 C and 40 0 C, and then cooked.
• a "SPONGE and DOUGH” scheme is a bread-making process widely practiced with two fermentation stages: a first stage, or “SPONGE”, which corresponds to the fermentation of a dough comprising 50 to 70% of the total flour used. , part of the water and all the yeast for several hours, usually about four hours, a second stage, or “DOUGH", in which the SPONGE after the fermentation described above is combined with the rest of the flour, the remainder of the water and the other ingredients of the dough (including all the sucrose), the mixture thus formed is kneaded, divided, molded and fermented, then cooked, this second fermentation in mold corresponding to the primer or "proof” and its duration being the time of primer.
• the yeasts resulting from the yeast strains according to the invention give lower primer times than those obtained with yeasts originating from the reference strain in bread-making test in direct pattern (NO-TIME DOUGH).
• the percentages are expressed as percentages of the baker, the so-called baker's percentage being a method of calculation applied to the ratios of the ingredients in which the total mass of the flour is always 100% and the mass of the other ingredients of the dough is calculated in relation to to this mass of flour.
• the invention also relates to a baker's dough containing baker's yeast as defined above.
• the baking dough is an unsweetened or slightly sweet dough.
• the baking dough contains mold inhibitors, preferably in the form of weak organic acids (for example having a pKa of 3 to 6) and / or their salts, and more preferably in the form of propionates.
• the mold inhibitor, or anti-fungal may be chosen from acetic acid, propionic acid, sorbic acid or their salts.
• the mold inhibitor is calcium propionate.
• This inhibitor in particular calcium propionate, is preferably incorporated in the paste at a concentration of 0.2 to 0.5% by weight on the mass of flour, in particular at a rate of 0.4% by weight on the mass of flour.
• the invention also relates to a process for preparing baking dough comprising a yeast fermentation step as defined above.
• the invention also relates to a process for preparing a baked bread product comprising a step of baking a baking dough as defined above.
• the invention relates to a breadmaking product that can be obtained by the process as defined above.
• Example 1 Measurement of the maltase activity Materials and methods The maltase activity is measured by assaying the release of p-nitrophenol following the action of maltase on p-nitro-phenyl- ⁇ -D-glucopyranoside, as described in Houghton-Larsen and Anders Brandt, Appl. About. Microbiol., 2006, p 7176-7182. Pre-culture of yeasts
• the yeasts are cultured in YPG medium containing 2% glucose overnight, at 30 ° C., with stirring.
• the pre-culture obtained above is centrifuged and the cells are washed before being seeded at a rate of 1 mg of dry matter per ml in YPG medium containing 2% glucose or in a YPM medium containing 2% maltose. After 4 hours of incubation, with stirring, at 30 ° C., the cells are harvested and a cell suspension at 20 mg of dry matter of yeast per ml is prepared. 1 ml of said cell suspension is taken to grind the cells. After grinding the cells, the supernatant is then recovered for the assay of the maltase activity. Measurement of maltase activity The supernatant obtained above is diluted between 5 and 400 times for the assay.
• the maltase activity of the strains tested is both expressed:
• the maltase activity measured under induction or repression conditions is shown in FIG.
• Table 1 indicates maltase activity under induction conditions (maltose).
• the strains according to the invention show a strong induction of the maltase activity in the presence of maltose: a 30% increase for the 1-3798 strain, 57% for the 1-3796 strain and 65% for strain 1-3797 is observed relative to the reference strain NCYC995.
• the slow strain NCYC996 exhibits a 37% decrease in maltase activity compared to the activity of the reference strain NCYC995.
• the CNCM 1-2412 slow strain has a particular profile because it exhibits a strong induction of maltase activity in the presence of maltose.
• Table 2 shows the maltase activity under repression (glucose).
• the slow control strains NCYC996 and CNCM 1-2412 show a strong repression of the maltase activity in the presence of glucose, with a maltase activity equal to 26% and 10% respectively of the maltase activity of the reference strain.
• strains 1-3796 and 1-3798 have maltase activity in the presence of glucose equal to respectively 55% and 51% of the maltase activity of the reference strain. Strains 1-3796 and 1-3798 are therefore fast strains.
• the strain 1-3797 has a maltase activity in the presence of glucose greater than that of the reference strain (equal to 134% of the maltase activity of the reference strain) and therefore has excellent non-suppression of the maltase activity in presence of glucose.
• EXAMPLE 2 Yield and Fermentative Strength Materials and Methods Culture on Molasses Plate A preculture of the yeast strains to be tested is carried out by seeding 0.3 mg of the yeast strain on a Petri dish of diameter 90 mm containing 20 ml.
• YEG medium (2% glucose).
• YEG medium contains 20 g / l glucose, 5 g / l yeast extract and 30 g / l agar.
• the yeast cells contained on the Petri dish are harvested.
• the yeast cells harvested at the end of the preculture are seeded on 140 mm diameter Petri dishes containing molasses, at a rate of 2 mg yeast dry matter per dish.
• the molasses medium contains 5 g / l of molasses, 0.5 g of (NHU) 2 HPO 4 , 12.7 g / l of K 2 SO 4 and 5.8 g / l of Na 2 SO 4 . g / 1 agar, pH5-5.5.
• the yeast cells contained on the petri dishes are harvested and washed.
• the yeast cells are resuspended in 20 ml of demineralized water.
• the yeasts are grown in 7 liter fermentors, in a semi-continuous mode, as described in the reference book "Yeast Technology", 2nd edition, 1991, G. Reed and TW Nagodawithana, published by Van Nostrand Reinhold, ISBN 0- 442-31892-8. In this culture mode, the molasses is brought discontinuously into the fermenter. Performance measurement
• the fermentative force is measured on dough pieces consisting of 20 g flour and a yeast suspension, in a Burrows and Harrison type fermentometer, over a period of 2 hours.
• the yeast suspension For the measurement of the fermentative force after culture on molasses plate, the yeast suspension consists of 100 mg of yeast solids in 15 ml of water containing 27 g / l of NaCl and 4 g / l of SO 4 ( NH 4 ) 2 .
• the yeast suspension For the measurement of the fermentative force after semi-continuous cultivation, the yeast suspension consists of 150 mg of yeast solids in 15 ml of water containing 27 g / l of NaCl and 4 g / l of SO 4 (NH 4 ) 2 ,
• the mixture of flour and yeast suspension is kneaded for 40 seconds in a kneader, so as to obtain a paste which is then placed in a water bath at 30 ° C. 13 minutes after kneading, the container containing the dough is hermetically sealed.
• the total amount of gas produced is measured in ml at 2 hours at 30 ° C.
• the fermentative force is measured under different dough conditions: sugar-free paste whose composition is the one mentioned above (PN), sugar-free paste in the presence 0.4% of calcium propionate by mass on the mass of flour (PN +), sweet dough containing 2 g of sucrose per 20 g of flour (PS), and sweet dough containing 2 g of sucrose per 20 g of flour and 0.4% calcium propionate by mass on the mass of flour (PS +).
• PN sugar-free paste whose composition is the one mentioned above
• PS sugar-free paste in the presence 0.4% of calcium propionate by mass on the mass of flour
• PS sweet dough containing 2 g of sucrose per 20 g of flour
• PS + sweet dough containing 2 g of sucrose per 20 g of flour and 0.4% calcium propionate by mass on the mass of flour
• Measurement of yield after culture on molasses plate is used in preselection to eliminate strains that show a yield decrease greater than 10% compared to the reference strain NCYC995.
• Table 4 indicates the difference in fermentative strength on sugar-free pulp (PN) of the strains tested compared to that of the reference strain NCYC995, in percentage, after culture on molasses plate.
• the pre-selection on a molasses plate was intended to eliminate the strains having a fermentative force lower than that of the reference strain NCYC995.
• the three strains according to the invention show many fermentative forces greater than or equal to that of the reference strain.
• the yield of the preselected strains is evaluated after semi-continuous culture, in order to select the strains with yield values approaching those obtained under conditions of industrial production.
• Table 6 indicates the difference in fermentative strength of the strains tested with respect to that of the reference strain NCYC995, as a percentage, after semi-continuous cultivation.
• strain 1-3797 has a very interesting fermentative force on both sugar-free and slightly sweetened pulp (an increase of 28% and 32% respectively compared to the reference strain), which is still improved in the presence of calcium propionate (increase greater than 35% in both types of dough).
• Strains 1-3796 and 1-3798 give a better fermentative force on sweet dough, with an increase in the fermentative strength of 26% for these two strains compared to the reference strain.
• the fermentative strength of these two strains on sugar-free pulp remains very interesting, with an increase of 14% compared to the reference strain.
• Example 3 Fermentation activity in bread-making tests Materials and methods
• the difference in primer time is measured between, on the one hand, a yeast obtained with the strain to be evaluated and, on the other hand, a yeast obtained with the strain.
• reference number NCYC995 the two yeasts being obtained with the same manufacturing process.
• the yeasts are grown in 20 liter fermentors, in a semi-continuous mode, as described in the reference book "Yeast Technology", 2nd edition, 1991, G. Reed and TW Nagodawithana, published by Van Nostrand Remhold, ISBN 0- 442-31892-8.
• yeasts in a 20-liter fermentor makes it possible, after drying, to obtain a quantity of dry yeasts sufficient to carry out bread-making tests.
• Fresh baker's yeasts at 32% solids thus obtained are then dried by fast drying in the presence of an emulsifier, sorbitan monostearate at 1.5%.
• the dry yeasts thus obtained are tested in a direct baking process (No Time Dough) in: sugar-free paste at room temperature, sugar-free paste at 18 ° C, and slightly sweetened paste (at 10%) at room temperature.
• the test protocol applied to the above recipes is as follows: - weigh the 6 or 7 solid ingredients, measure the ambient temperature and the temperature of the flour, adjust the temperature of the water to obtain a paste temperature from 27 0 C +/- 0.5 0 C, place the ingredients in a Mac Duffy® bowl of a HobartA200® kneader, - mix slowly in 1 st speed for 1 min, start the kneading according to the following program: in 1st speed for 5 minutes leave to rest for 5 minutes in 2nd speed for 5 minutes, to obtain a paste having a temperature of 27 ° C.
• Table 7 indicates the difference between the primer time obtained with the dry yeasts resulting from the strains according to the invention and that of the dry yeasts resulting from the reference strain NCYC995, this difference being expressed as a percentage.
• finishing times were measured after a direct baking process, on normal pasta or slightly sweet pasta (containing 10% sugar), at room temperature.
• the yeasts resulting from the strains according to the invention have a primer time decreased from 17% to 22% relative to the yeasts resulting from the reference strain: their fermentative activity is therefore greater than that of yeasts originating from the reference strain.
• the yeasts resulting from the strains according to the invention have a primer time decreased from 14% to 16% with respect to the yeasts resulting from the reference strain: their fermentative activity is therefore greater than that of the yeasts originating from the reference strain.
• CNCM 1-3798 give a lower priming time than that obtained with the yeasts of strain NCYC995 and are therefore faster to achieve the desired bread volume.

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