Substrate-limited doughs.

The present invention relates to doughs producing a limited and controllable volume of CO₂ gas during the proof period of the bread making process. Doughs used for bread making contain levels of fermentable sugar which are much higher than needed for producing the required volume of CO₂ gas during the final proof of a bread making process. Since both underproofing and overproofing of doughs will result in inferior bread quality (Pyler: Baking Science and Technology, Siebel Publishing company, 1973) it is important to strictly control all the variables which affect the rate of gas production in dough.

The current bread making processes show little tolerance towards small changes in process variables such as proof time, proof temperature and yeast dosage, which affect the rate of gas production during proofing. It is especially difficult to achieve constant gas production when bread is prepared from retarded doughs, which are proofed overnight by increasing the temperature of a cooled dough in a programmable cooling/proofing cabinet.

When frozen dough is used for bread making there are also serious disadvantages due to instability of the yeast during freezing, frozen storage and thawing (B.L. Bruinsma and J. Giesenschlag, Bakers Digest November 13, 1984 p. 6). A reduction in yeast activity causes a reduction in the volume of the baked bread. The proof time therefore has to be increased in order to correct for such a reduction in yeast activity. The necessary adjustment will vary from case to case depending on factors such as freezing rate, frozen storage time and thawing rate. For the baker this variation in the adjustment required is undesirable. Another disadvantage of the frozen dough method is that fast warming up of the dough will cause temperature gradients in the dough, leading to local overproofing of the outside part of the dough piece. This undesirable situation will occur in particular in large dough pieces even when the period of proofing is preceded by an overnight thawing period in a refrigerator (2-4°C). Since temperature gradients due to a fast warming up have to be avoided during proofing of frozen doughs, long proof times are required even when higher amounts of yeast are used.

The present invention provides a dough for the preparation of a yeast-leavened flour product which comprises yeast and sugar(s) fermentable by the yeast, wherein the amount of sugar(s) fermentable by the yeast is limited so that the maximal gas production by the yeast is controlled. The invention also provides a method for producing a dough comprising yeast and sugar(s), which method comprises limiting the amount of sugar(s) fermentable by the yeast so as to control the maximal gas production by the yeast. In one embodiment the method of the invention includes carrying out a prefermentation step on a substantial part of the flour to reduce the amount of fermentable sugar in the dough. The yeast is allowed to consume substantially all available fermentable sugar(s) during the fermentation period of the bread making process. Once this amount of sugar has been consumed, sufficient CO₂ gas will have been produced to fully proof the dough. The dough volume will not substantially increase upon further extending the proof time. The quality of bread obtained from such doughs shows great tolerance towards large variations in factors determining the gas production rate in normal doughs such as dough temperature, yeast dosage or proof time.

Dough according to the present invention may be industrially prepared by methods similar to those used for the preparation of doughs containing conventional ingredients. The dough may be used for the preparation of various lean or rich breads and other farinaceous products which are optionally stored in the frozen state. The dough of the present invention may be used in a conventional manner, and may be baked after purchase, if necessary after thawing.

Yeast which is used in dough exists in several formulations such as cream yeast, compressed yeast or fresh yeast and dried yeast. Dried yeast is available as active dry yeast (ADY) and as instant dry yeast (IDY) having a moisture contents of 6-8% and 3-6% respectively. The yeast used in the present invention may, for example, conveniently be added to the flour in an amount up to 3% dry matter (w/w). Percentages (w/w) are calculated on the weight of the flour (100%). Suitably yeasts selected from the genera <u style="single">Saccharomyces</u> and <u style="single">Kluyveromyces</u> are used in the present invention. Advantageously a strain is used selected from <u style="single">S</u>. <u style="single">cerevisiae</u>, <u style="single">S. unisporus</u>, <u style="single">S</u>. <u style="single">diarensis</u>, <u style="single">S</u>. <u style="single">exiguus</u> and <u style="single">S</u>. <u style="single">kluyveri</u>.

A dough according to the present invention suitably contains 1-3% (w/w) of fermentable sugar, allowing a total maximal gas production of 150-500 ml CO₂ per 100 g of dough.

'Fermentable sugar(s)' as used herein means sugars which may be fermented by the yeast and which may be present in the dough, may be added to the dough or may originate from carbohydrate fractions present in or added to the dough, which are converted during the bread making process into fermentable sugar(s) by enzymes present in or added to the dough.

The flour used in conventional doughs contains about 5% (w/w) of damaged starch, which is convertable by the action of α and β-amylases starch into maltose. If the formed maltose (in a lean dough) is completely fermented by the yeast about 1000 ml of CO₂ gas will be produced in 100 g of dough. This amount is about 5 times as much as is required to obtain a desirable proof height and consequently an optimal loaf volume after baking. Advantageously wheat flour and/or rye flour is used.

According to one embodiment of the invention a flour is used with a level of less than 2%, preferably 0.1-1%, more preferably 0.1-0.5% (w/w) of damaged starch. This flour allows a maximal gas production of about 200 ml CO₂ per 100 g dough, originating from the glucofructosan fraction and the reduced amount of damaged starch.

Another way of reducing the amount of fermentable sugar available is the application of a sponge and dough process, in which the yeast ferments the fermentable sugar in the bulk of the flour at the sponge stage. Subsequently the remainder of the flour is added and mixed into a dough containing a reduced and limited amount of fermentable sugar. This sponge and dough process can advantageously be applied with regular bakers yeast to control the amount of fermentable maltose in the dough.

In one embodiment of the invention the dough comprises a yeast which is not capable of fermenting part of the sugars present in the dough, typically maltose or maltose and sucrose. When the yeast is incapable of fermenting maltose, the maltose originating from the damaged starch fraction of the flour cannot be used by the yeast for the CO₂ production. The amount of gas produced is controlled by fermentation of other sugars present (mainly glucofructosans), or added to the dough.

According to another aspect of the invention the dough comprises added carbohydrate as the only source of sugar(s) that can be fermented by the yeast.

An advantage of the invention is that it allows the volume of a baked product to be chosen in advance and achieved by controlling the (maximal) gas production. Once all fermentable sugars in the dough have been fermented and have produced the desired volume of CO₂ required for fully proofing the dough, the proof time may be extended without causing serious overproofing of the dough. Such doughs provide great flexibility during bread making since the fully proofed doughs can be kept for a considerable length of time in a proofing cabinet before being baked into bread. Moreover the (maximal) amount of CO₂ produced in such dough depends only on the amount of fermentable sugars present in or added to the dough and is hardly influenced by factors controlling the rate of gas production such as yeast dosage or dough temperature.

Another advantage of the invention is that the sweet taste of the baked product can be controlled. Since the entire amount of fermentable sugars present in the dough will, according to the invention, be consumed by the yeast, non fermentable sugars can be used for adjusting the sweetness of the baked product. When, for example, a maltase and invertase deficient yeast is applied, saccharose, maltose and glucofructosans in the dough are not fermented and will contribute to the sweetness of the bread product. When regular bakers yeast is used, artificial sweeteners and non fermentable sweet sugars can be added to improve and adjust the sweetness of the baked product. Examples of useful additives for controlling sweetness are artificial sweeteners like aspartame (Nutrasweet™), lactose (or whey permeate) and isomaltulose (Palatinit™). Generally 0.1-10% of such non-fermentable sugars will be present in or may be added to the dough.

In one embodiment, the method of the invention includes the step of freezing the dough. As an example, the method may comprise the steps of <ul id="ul0001" list-style="none"><li>(a) dividing the unfrozen dough into separate portions of dough,</li><li>(b) moulding each portion of dough into the desired shape and</li><li>(c) freezing each portion of the dough to a temperature of -30°C to -10°C.</li></ul>

Frozen doughs produced in accordance with the invention have additional advantages. First of all a reduction in the yeast activity due to a freeze/thaw cycle will no longer affect the volume of the baked product, provided that sufficient time has been given to the (residual) yeast for a complete conversion of all fermentable sugars in the dough into CO₂ gas. Moreover the conventional method of critical overnight thawing at 2-4°C followed by proofing at 30-40°C, can be replaced by a flexible overnight thawing/proofing method at ambient temperature (20-30°C). By using this method the baker will have fully proofed doughs at his disposal early in the morning and these doughs can be baked into bread products of constant quality at any moment during the rest of the day. It is also possible to obtain fully proofed substrate-limited doughs directly from frozen doughs by using a rapid thawing/proofing method, which is not applicable to normal doughs.

Another embodiment of the method of the invention therefore comprises combining the steps of thawing and proofing in one step by bringing the frozen dough to a temperature of 20°C to 50°C. When normal doughs are rapidly thawed and proofed, temperature gradients will occur, resulting in a local overproofing of the outside part of the dough pieces. This undesirable situation is prevented when using substrate-limited doughs according to the present invention, even when large dough pieces are rapidly thawed and proofed. Also the period of time for the thawing and especially for the proofing is now not critical anymore because the gas production will stop when all the fermentable sugars are converted. Because in this method the volume of CO₂ gas produced depends on a limited amount of fermentable sugar in the dough, the frozen dough method is very flexible and is suited for the home baked goods market.

One embodiment of the method of the invention involves the steps of <ul id="ul0002" list-style="none"><li>(a) thawing the frozen dough at a temperature of 2°C to 50°C,</li><li>(b) proofing the dough for at least 40 minutes at a temperature of 20°C to 50°C, and</li><li>(c) baking the dough.</li></ul>

Another advantage is that the frozen doughs can be thawed and proofed in large numbers at the same time, whereas the fully proofed doughs can be stored and baked later on in smaller quantities at any moment during the rest of the day. In this way it is possible to sell all day long freshly baked goods.

This advantage also applies for fresh doughs which are prepared early in the morning and which can be baked at any moment during the rest of the day as the volume of the fully proofed dough will not substantially increase during the rest of the day.

The present invention may also be used in connection with the retarded dough method. Retarded doughs are applied by some bakers to avoid night work. According to the retarded dough method, cooled doughs are proofed during the night in a programmable cooling/proofing room. The next morning the doughs are ready for baking and fresh bread is therefore available early in the morning. According to the present invention the production of CO₂ gas can be controlled by limiting the amount of fermentable sugar instead of controlling the temperature and time. Moreover the doughs can be stored and baked afterwards at any moment during the rest of the day.

The present invention is useful not only for bread making but also for preparing all kinds of yeast leavened bakery products such as pizzas, croissants and doughnuts.

In the following examples there are described several preferred embodiments to illustrate the invention. However, it is to be understood that the invention is not intended to be limited to the specific embodiments.

Example 1

The flour (Apollo) used in the next Examples (1, 2, 4-8) was obtained from Stolp &amp; Co., Bunschoten, The Netherlands. This American type of flour has been bromated at the mill. Bromate, present in the flour together with ascorbic acid, added to the flour contribute to the stability of the doughs when being subjected to long fermentation periods. Gasproduction, however, is not affected by these oxidants. Table 1 shows how the various carbohydrate fractions contribute to the gasproduction in doughs prepared from Apollo flour. <tables id="tabl0001" num="0001"><img file="EP0442575A1_D0001.tif" /></tables>

During the final proof of the bread making process only about 200 ml CO₂/100 g dough are required to fully proof a dough. When conventional baker's yeast is used, about 5 times as much gas is formed as is necessary (see Table 1: 960 ml CO₂/100 g dough). Using the same dough a smaller amount of gas can be produced by choosing a yeast which ferments only the glucose and fructose and which is not capable of fermenting maltose.

A dough formulation was prepared of the following composition <tables id="tabl0002" num="0002"><img file="EP0442575A1_D0002.tif" /></tables> The yeast strain used for this experiment is a maltose adaptive (MAL^+/-) instant dry yeast strain, which will behave as a MAL⁻ strain (MAL⁻ = not fermenting maltose), when added in dosages above 1.5% to flour. When added in a dosage of 2% (w/w) about 120 ml CO₂ gas was produced mainly from the glucofructosan fraction within 1.5 hours at 30°C. Thereafter the gas production rate drops sharply and only about 8 ml CO₂ was produced per hour in a 50 g dough piece.

In gassing power tests similar results were obtained when replacing the 2% <u style="single">S</u>. <u style="single">cerevisiae</u> V328 CBS 108.90 instant dry yeast (MAL^+/- = maltose adaptive) by 2% compressed yeast of one of the following sucrose (= saccharose) fermenting and maltose non-fermenting (SUC⁺/MAL⁻) yeast strains: <dl id="dl0001"><dt><u style="single">S</u>. <u style="single">cerevisiae</u> D2</dt><dd> (CBS 109.90)</dd><dt><u style="single">S</u>. <u style="single">cerevisiae</u> DS 10638</dt><dd> (CBS 110.90)</dd><dt><u style="single">S</u>. <u style="single">cerevisiae</u> DS 16887</dt><dd> (CBS 111.90)</dd><dt><u style="single">S</u>. <u style="single">cerevisiae</u> V 79</dt><dd> (CBS 7045)</dd><dt><u style="single">S</u>. <u style="single">cerevisiae</u> V 372</dt><dd> (CBS 7437)</dd><dt><u style="single">S</u>. <u style="single">exiguus</u> V 04</dt><dd> (CBS 112.90)</dd><dt><u style="single">S</u>. <u style="single">exiguus</u> 8130</dt><dd> (CBS 8130)</dd><dt><u style="single">S</u>. <u style="single">kluyveri</u> 4798</dt><dd> (CBS 4798)</dd><dt><u style="single">S</u>. <u style="single">kluyveri</u> 6545</dt><dd> (CBS 6545)</dd><dt><u style="single">S</u>. <u style="single">kluyveri</u> 6626</dt><dd> (CBS 6626)</dd></dl>

Example 2

Table 2 shows the results of gassing power tests with 100 g dough pieces containing 2% compressed yeast of a sucrose (= saccharose) and maltose non-fermenting yeast (SUC⁻/MAL⁻) strain <u style="single">S</u>. <u style="single">unisporus</u> 398 (CBS 398). From this Table it can be concluded that hardly any CO₂ gas is produced during fermentation (&lt; 50 ml CO₂ / 100 g dough after 4 hours of fermentation). Addition of 1.1% readily fermentable glucose results in a rapid production of about 130 ml CO₂ gas within 2 hours of fermentation. Hereafter the CO₂ gas production drops sharply. Hardly any additional gas production is observed after the addition of 0.95% saccharose which cannot be fermented by this yeast strain. Therefore readily fermentable glucose (or fructose) can be applied for controlling the amount of gas produced, whereas non-fermentable saccharose can be applied for controlling sweetness of bakery products produced from these doughs. Similar results have been obtained using one of the following SUC⁻/MAL⁻ strains: <dl id="dl0002"><dt><u style="single">S</u>. <u style="single">unisporus</u> 398</dt><dd> (CBS 398)</dd><dt><u style="single">S</u>. <u style="single">diarensis</u> 4309</dt><dd> (CBS 4309)</dd><dt><u style="single">S</u>. <u style="single">diarensis</u> 6463</dt><dd> (CBS 6463)</dd><dt><u style="single">S</u>. <u style="single">cerevisiae</u> DS 16887</dt><dd> (CBS 111.90)</dd></dl><tables id="tabl0003" num="0003"><img file="EP0442575A1_D0003.tif" /></tables>

Example 3

For demonstrating the principle of the invention a model dough with a limited amount of fermentable sugar was prepared by mixing regular bakers yeast (SUC⁺/MAL⁺), gluten, starch and sugar into a dough. <tables id="tabl0004" num="0004"><img file="EP0442575A1_D0004.tif" /></tables><tables id="tabl0005" num="0005"><img file="EP0442575A1_D0005.tif" /></tables> From the results in Table 3 it can be concluded that the limited amount of fermentable sugar in these doughs is consumed within 1 hour when 2% Fermipan is used and within 2 hours when 1% Fermipan is used. The proof heights and loaf volumes are nearly constant and do not depend on proof time or yeast dosage once the fermentable sugars have been converted into CO₂ gas.

Example 4

A sponge and dough procedure can also be applied for reducing the amount of sugars fermentable by regular bakers yeast (SUC⁺/MAL⁺). <tables id="tabl0006" num="0006"><img file="EP0442575A1_D0006.tif" /></tables><tables id="tabl0007" num="0007"><img file="EP0442575A1_D0007.tif" /></tables>

From Table 4 it can be concluded that within 1 hour proof time all fermentable sugars in the dough have been converted into CO₂ gas. Proof heights and loaf volumes remain nearly constant when extending the final proof time up to 3 hours.

Example 5

When using regular wheat flour containing about 5% of damaged starch a maltose non-fermenting yeast strain (MAL⁻) can be applied for reducing the amount of CO₂ gas produced to the desired level. <tables id="tabl0008" num="0008"><img file="EP0442575A1_D0008.tif" /></tables><tables id="tabl0009" num="0009"><img file="EP0442575A1_D0009.tif" /></tables>

From the results given in Table 5 it can be concluded that variation in proof time from 170 to 340 minutes hardly influences proof heights and loaf volumes when using <u style="single">S</u>. <u style="single">cerevisiae</u> V 328 (CBS 108.90) (SUC⁺/MAL⁻ at 2% dosage) or <u style="single">S</u>. <u style="single">cerevisiae</u> D2 (CBS 109.90) (SUC⁺/MAL⁻). When using <u style="single">S</u>. <u style="single">cerevisiae</u> DS 16887 (CBS 111.90) (SUC⁻/mal⁻) hardly any CO₂ gas is produced resulting in a low loaf volume. When supplying this yeast strain with a readily fermentable sugar (1% glucose), proof heights and loaf volumes increase to normal levels and are hardly affected when extending the proof time from 170 to 340 minutes.

Example 6

A dough of the following composition was prepared, and stored in the refrigerator. <tables id="tabl0010" num="0010"><img file="EP0442575A1_D0010.tif" /></tables> The results of the baking tests in Table 6 show that low temperature doughs, which have been stored in the refrigerator for 0-6 hours, gave a constant proof height after proofing for 1.5 hours and a constant loaf volume after baking. Such a procedure allows a baker to prepare bread from doughs which have a long shelf life in the refrigerator, and can be baked into bread of constant quality after a proof time that is not very critical. <tables id="tabl0011" num="0011"><img file="EP0442575A1_D0011.tif" /></tables>

Example 7

Frozen doughs of the following composition were prepared by the following procedure. <tables id="tabl0012" num="0012"><img file="EP0442575A1_D0012.tif" /></tables><tables id="tabl0013" num="0013"><img file="EP0442575A1_D0013.tif" /></tables>

The baking results in Table 7 indicate that a proof time extension from 1 to 3 hours at 30°C hardly affects loaf volume and proof heights of frozen doughs that have been thawed overnight in a refrigerator. When the overnight thawing step was omitted, a constant maximal proof height and loaf volume was attained after a proof time of about 1.5 hours. The rapid thawing/proofing procedure at elevated temperature (40°C) did not result in an irregular proofing of the doughs. Thus the local overproofing of the outside parts of the dough, which is caused by temperature gradients during thawing/proofing, can be avoided when using doughs containing a limited amount of fermentable substrate.

Example 8

Dough formulations of the following compositions were prepared. <tables id="tabl0014" num="0014"><img file="EP0442575A1_D0014.tif" /></tables><tables id="tabl0015" num="0015"><img file="EP0442575A1_D0015.tif" /></tables><tables id="tabl0016" num="0016"><img file="EP0442575A1_D0016.tif" /></tables>

The baking results of the doughs of Table 8 show that the different thawing/proofing procedures do result in a constant bread quality with respect to the bread volume. The bread volume was hardly influenced by the point of time at which the fully proofed doughs were baked. Also the storage time in the freezer did not influence the bread volume. Even if yeast activity would have been partly lost during frozen storage of the dough, all fermentable sugars are still completely converted into CO₂ gas if proof times are long enough. Thus loaf volumes in this bake-off system were hardly affected by variations in the period of storing the frozen doughs in the freezer.

The fully proofed doughs could be kept for a long time (at least 6 hours) but not unlimited at 30°C.

The addition of lactose (composition B) gave the bread a somewhat sweeter taste (lactose is not fermented by the yeast). Xanthan gum (composition B) was added to improve the crumb structure of bread in this bake-off system.