On the market a variety of different refrigeratable dough products are presently availa- ble to consumers to produce different sorts of baked products. Products containing ordinary baker's yeast may only be stored for quite a limited period of time, since even under conditions of low temperature the yeast shows substantial activity ensuing in a consistent production of carbon dioxide. This continuous development of gas eventually results in a leavening of the dough already during storage, i. e. in the refrigerator.

Moreover, the continued activity of the yeast beyond the desired degree of proofing deleteriously affects the organoleptic and rheological properties of the dough, resulting in unacceptable final baked products.

For this reason most of the commercial dough compositions do not contain yeast to leave the dough, but rather chemical agents, so that they may be stored for a prolonged period of time without occurrence of the known detrimental effects. The advantage of such leavening agents resides in that their behavior is based on a predictable chemical reaction, allowing for a control of the volume of carbon dioxide produced to leaven the dough. Though the storage lifetime of products leavened by means of chemical agents may be extended, the final baked goods obtained therewith are known to be inferior as compared to products leavened by means of baker's yeast. Particularly, the texture of said products is often not acceptable to customers while said products also lack flavorings produced by the yeast during its activity.

Another approach to avoid the problems encountered with the use of yeast in dough compositions under long term storage at refrigeration conditions, was to store the yeast containing dough, optionally in prebaked form, at freezing temperatures of about - 20 °C so as to reduce the activity of the yeast to a minimum. To this end EP-0 442 575 teaches the use of a dough composition that utilizes the substrate limiting concept.

Accordingly a dough is leavened with a maltase negative yeast and is subsequently frozen for long term storage.

However, this approach also showed to be unsatisfactory in that products prepared from frozen dough compositions are not as convenient for the consumer as are refrigerated dough products. The frozen dough has to be thawed and in most instances preproofed prior to baking, which preproofing has to be monitored by the consumer to avoid extensive proofing of the dough. Moreover, the texture of the final baked product derived from frozen doughs has shown to be inferior to products produced from non- frozen doughs and the characteristic flavor associated with yeast leavening is inferior or often lacking at all.

Recently low temperature inactive strains of baker's yeast (Iti-strains) have been developed, that is, yeast strains that are essentially inactive at low temperatures, but retain their activity when brought to higher temperatures.

In EP-0 487 878 there is described a process for constructing yeast strains having Iti- property, wherein a strain of saccharomyces cerevisiae is subjected to a mutagenic treat- ment, at least one mutant having a lti-property is selected and is backcrossed at least once with a wild type haploid strain of saccharomyces cerevisiae having an opposite mating type, wherein at least two backcross segregants having Iti property and opposite mating types are selected and are crossed at least once and a diploid strain thus obtained having a growth potential, a lti-property and the ability to raise a dough is selected.

Further the construction of different lti-derivatives have been described. Thus, in EP-0 663 441 there is described a process for constructing lti-strains that react more sluggishly with the maltose contained in the dough. These strains may be obtained by crossing a haploid saccharomyces cerevisiae having lti-property with a haploid saccharomyces cerevisiae strain having an active maltase gene, that is under catabolic repression, subsequently crossing the segregants and selecting a diploid strain showing Iti-property, an active Mal-phenotype (Mal(+); expressing the gene coding for maltase either inducible (wild-type) or constitutively), and has a growth potential.

For a dough composition to be stored at refrigerator conditions and to eventually result in a baked product having the desired texture and excellent flavoring the activity of the yeast in the dough must be carefully controlled. To this end the activity should not be entirely null during storage, since otherwise no acceptable texture will be formed and no flavorings will be produced. However, an extensive activity of the yeast is known to

lead to an excessive leavening of the dough during storage with the flavor deteriorating with continuing metabolic action of the yeast.

As regards the use of current yeast-strains having lti-property, these strains have been found to produce doughs with good texture and flavor properties only in a time range of refrigerated storage between 2 and 3 weeks, while the dough tend to be underdeveloped in the first week and overdeveloped or even deteriorating between 4 and 5 weeks.

So far scientists have not been able to develop dough compositions that provide the desired properties, that is, to provide a yeast containing dough composition, in which an activity may be achieved necessary to obtain over the entire shelf life baked products having the same or a similar texture and flavor as compared to products prepared from freshly prepared doughs.

An object of the present invention is therefore to obviate the disadvantages of the prior art and to provide dough compositions giving rise to final baked products that show excellent properties as regards the texture and the flavor.

Another object of the present invention is to provide a method for preparing said dough.

During the extensive studies leading to the invention the present inventors have found that if the overall activity of Iti-yeasts is controlled in a particular manner the above problems can be solved. Hence, it has been found that in order to convey the desired properties to the final baked goods a major part of (yeast) activity in the dough composition, as evidenced by the development of CO, should be exerted within a limited time period after preparation of the dough (representing an activity-boost, which should not be too excessive but at the same time not be too low), while during the subsequent weeks of storage the yeast should exhibit only a relatively low activity.

The present invention provides dough compositions capable of being stored at refrigeration temperatures for the preparation of yeast leavened products, comprising at least one strain of a lti-yeast and one or more sugars fermentable by the lti-yeast in an amount, so that the dough compositions show a CO2 production of between about 50 and 250 ml/100 g dough within a time period after preparation not exceeding 1 week, with the total amount of COz-production during 5 weeks after preparation being limited to about 400 ml/100 g dough.

In the following the invention will be described with reference to preferred embo- diments and the figures, in which : Fig. 1 shows a graph, illustrating the production of CO during 28 days, using 0. 1 % by weight dry matter of the lti-strain L500 as yeast and including 1 % by weight glucose into the dough.

Fig. 2 shows a graph, illustrating the production of CO2 during 28 days, using 0. 3 % by weight dry matter of the lti-strain LCG 22 as yeast and including 1 % by weight glucose into the dough.

The strain L500 [NCIMB 40329] and the process of construction is described in detail in EP-0 487 878, which document is included herein by way of reference.

The Iti-yeast LCG22 [NCIMB 40612] utilized is a yeast as described in EP-0 663 441, the content of which is incorporated herein by way of reference.

It has been found that a dough composition with the above mentioned features, giving rise to the particular CO2-profile, provides an excellent texture, which is conveyed to the refrigeratable dough composition already within the first hours or days after its preparation, which texture is maintained and even improved during the shelf life yielding excellent products produced therewith. Since the metabolic activity of the yeast is maintained at a certain, yet low level during storage, the flavor that has developed during the first few days after the preparation of the dough is not deteriorated but rather improved.

The activity boost of the lti-yeast should give rise to a CO2-production of between about 50 to 250 ml Cor/100 g dough preferably about 100 to 250 ml Cl,,/100 g dough and may be carried out at ambient or slightly raised temperatures as are usually utilized in the art. According to a preferred embodiment the activity boost may well be carried out at refrigerated temperatures of about 4 - 13 °C.

The time period for the activity boost varies depending on the amount or type of sugar or yeast utilized and the temperature applied, and may be in the range of from 1 to several hours (in the case of boosting at ambient or higher temperatures) or within 1 week. The skilled artisan may well adjust the appropriate time depending on the factors to be considered. Accordingly the activity boost may well be completed after 1, 2,3, 4, 5,6 or 7 days. The boosting process should be completed after 1 week, so that after this period only a minor activity of the yeast is to be found. It is, however, preferred

that the CO2-production is performed by the yeast in a slow manner, so that an excellent texture of the dough be formed. This may be best achieved by bringing the dough composition immediately after its preparation to refrigerator temperatures of about 4 °C to 13 °C and storing the composition at these temperatures.

According to a preferred embodiment the lti-strains utilized may be strains that express the maltase gene non constitutively or constitutively, as long as the activity of the yeast does not lead to a CO2 production exceeding the limits of CO2-production indicated. On the other hand, in order to avoid an excessive activity of the yeast deriving e. g. from the consumption of maltose present in the dough the Iti-yeast may be selected to be repressed by glucose.

In addition mixtures of Iti-yeast strains having different phenotypes may be employed.

Consequently a mixture of a Mal(~) Iti-strain (a yeast strain that is not capable of metabolizing maltose) together with a Mal(+9 Iti-strain, which is optionally catabolically repressed by glucose, is well within the scope of the invention. The skilled person may select an appropriate mixture from the Iti-strains available, in agreement with the factors influencing the yeast activity, such as the presence of maltose, the temperature, other sugars present etc. , to adapt the dough composition to the CO2-profile according to the present invention.

The sugar to be used in the present dough may be any of the sugars to be metabolized by the yeast strain utilized, such as glucose, saccharose or fructose. Maltose may well be the sugar of choice, if it is contained in the dough composition in an adequate amount so as not to lead to an excessive C02-production. The maltose may for example be provided by the action of amylases present in the dough on the starch of the flour utilized.

In general it is preferred that the amount of sugar fermentable by the lti-yeast to be included in the dough be in a range that the above demands for the CO2 production are met. Thus, as regards the exemplary inclusion of glucose into the dough composition the following equation may be cited, which shows the maximal amount of CO2 to be obtained : 1 Mol Glucose (180 g) - 2 Mol C°2 (44,8 1) 1 g Glucose --> 249 ml CO2 Thus by including e. g. a maximum of 1 g of Glucose into 100 g of dough containing a Iti-yeast the yeast will ferment said sugar to yield an amount of CO ; being maximal

about 249 ml. After consumption of glucose the CO2 production decreases due to lack of an adequate fermentable sugar, with the yeast slowly starting to utilize a different carbon source. In order to arrive at the desired C02-profile the skilled person will select the appropriate amount of the sugar depending on the type of sugar used (e. g. glucose or saccharose) considering other parameters according to ordinary technical skill.

Thus, the total amount of sugar to be included in the dough may be within a range of from about 0. 5 Mol to 5, 6 mMol/100 g dough. For glucose the preferred amount is from about 1 to 5.6 Mol, more preferably about 4 to 5.6 Mol, most preferred about 5 mMol. For e. g. saccharose the preferred amount is from about 0. 5 Mol to 2. 6 mMol, more preferably about 1 to 2.5 Mol, most preferably about 2.5 Mol.

The total amount of CO2-production of the dough for a time period of 5 weeks after its preparation is limited to about 400 ml COz, preferably about 350 ml CO2, more preferably about 300 ml Ci-,/100 g dough.

The method of the present invention comprises mixing water, flour, at least one strain of a lti-yeast and one or more sugars fermentable by the lti-yeast in an amount so that the dough composition will give rise to a CO2 production of about 50 to 250 ml/100 g dough within a time period after its preparation not exceeding 1 week, with the total amount of CO2-production during 5 weeks being limited to about 400 ml/100 g dough.

The flour utilized may be any flour commercially available, though it may be advantageous to use flour, which contains a certain amount of damaged starch, which may serve as a sugar source for the Iti-yeast present. Thus, the activity boost may be carried out by using the maltose present in the flour, in case a Iti-yeast is used that may metabilize maltose. The activity boost may likewise be effected by including a different sort of sugar, e. g. glucose, into the dough composition, wherein the Iti-yeast utilized may have a maltase gene which is repressed by glucose. In this case case the initial boost with glucose also serves to repress the maltase gene of the lti-yeast, while after consumption of the glucose the maltase repression slowly decreases with the yeast slowly starting to ferment maltose.

Water is generally added according to the hydration capacity of the flour and the potential influence of other components contained in the dough, which may increase or decrease this capacity, until a workable dough is formed.

The dough may optionally contain salts, preferably sodium chloride, in an amount of 0 to 8 parts by weight, based on the amount of flour being 100 parts by weight. Further ethanol may be included in an amount of from 0 to 8 parts by weight, again based on the amount of flour being 100 parts.

The yeast may be added as dry yeast, rehydrated in all or a part of the water used for preparing the dough. The use of a press cake, having a dry matter content of about 20 to 40 % or the use of yeast-cream having a dry matter content of about 10 to 20 % may likewise be envisaged, with the water to be added to the flour being adjusted correspon- dingly.

The sugar may be added in amounts so that the requirement with respect to the activity of the yeast under refrigerator conditions are met.

The activity of the yeast in the dough is measured according to the development of C02, of the dough. For measuring the development of CO2 a variety of different apparatuses are known. It is, however, acknowledged that most of the methods available do not give reliable results. The measurements of the CO, -development in the doughs are therefore carried out by means of the"Niesler", an apparatus for reliably determining the amount of gas developed. This apparatus comprises a gas-tight vessel, having integrated therein a pressure sensor for sensing the absolute pressure and a valve for discharging gas. In exercising the apparatus the dough is charged into the vessel, which is sealed in a gas tight manner. The amount of developing gas is detected via the increase of the pressure in the vessel. From time to time the pressure built up in the interior of the vessel is discharged via the valve, which may be effected automatically.

The vessels are kept in an environment having a constant temperature, so that the influence of temperature changes on the sample may be avoided. The sensor is extremely sensitive to pressure changes and may detect any change in pressure of as low as 0. 1 mbar. As regards a vessel having a volume of 500 ml an additional gas volume of 50 il may be detected. Since the present apparatus provides for a measurement of different absolute pressures no reference measurements are required. Consequently the "Niesler"provides for a parallel measurements at different temperatures. The data obtained are fed to a computer, wherein they may be processed so as to provide a suitable display showing the volume of gas produced in the vessel. The"Niesler"is commercially available and may be obtained from Biospectra AG, Schlieren (CH).

The invention will now be described with reference to the following examples which are not to be construed to limit the scope of the present invention.

Example 1 The following recipe has been used to produce yeast doughs with glucose as additional sugar. Invredent parrs bv weghr % Flour (Bruggmiihie, type 400, Goldach, CH) 100 63.84 Salt (NaCl)2,471.58 Ethanol1,631.04 Water50,8132.44 Yeast dry matter (L500 (Iti-strain))0,1570.10 Glucose 1,57 1.00 The dough was divided into aliquots of 100 g and introduced into the vessels of the "Niesler", where the dough composition was held over a time period of 4 weeks at a temperature of about 8 °C. During said time period the development of CO, was measured. The results of these measurements are shown in Fig. 1. When baking the dough prepared in this manner after 1,2, 3,4 or 5 weeks the product showed an excellent texture and flavor that was comparable to that of products prepared from freshly mixed dough compositions.

Example 2 The procedure of example 1 was repeated with the following recipe to produce yeast doughs with glucose as additional sugar. Ingredient parts by weight % Flour (Bruggmuhle, type 400, Goldach, CH) 100 63.84 Salt (NaCl)2'47L58 Ethanol1'63L04 Water49.432-24 Yeast dry matter (LCG22 (lti-strain))0.147 0.3 Glucose 1.57 1.0 The dough was divided into aliquots of 100 g and subjected to a measurement with the "Niesler"over a period of 4 weeks as detailed in example 1. The results of this measurements are shown in Fig. 2. Also this dough composition, when baked after 1, 2,3, 4 and 5 weeks after its preparation yielded products comparable to those made from freshly prepared dough compositions.