Process for obtaining improved structure build-up of baked...

Details Process for obtaining improved structure build-up of baked... Process for obtaining improved structure build-up of baked...

1999-03-22

2002-06-04

Tran, Lien (Department: 1761)

Food or edible material: processes, compositions, and products

Fermentation processes

Of farinaceous cereal or cereal material

C426S020000, C426S094000, C426S496000, C426S546000

Reexamination Certificate

active

06399119

ABSTRACT:

FIELD OF THE INVENTION
This invention is related to a process for obtaining improved structure build-up of baked products as well as new dextrans and new micro-organisms producing them. The present invention is also related to dough and baked products containing these dextrans.
BACKGROUND OF THE INVENTION
The rheological properties of a dough are determinant for the quality of the baked end product. In order to estimate the quality of bread and baked products in general, the parameters listed hereafter are used: volume, crumb structure softness and shelf life, color of the crumb and the crust, flavor and shape (round, flat).
So called bread improvers are used to enhance the rheological properties of the dough and consequently, to obtain a better baked end product. For this purpose, chemical agents are used, such as: potassium bromate, ascorbic acid, iodates, azodicarbonamide, cysteine. Emulsifiers are used too, such as: diacetyltartaric acid esters, sodium and calcium stearoyllactylate, and if necessary sucrose-esters.
Some enzymes also improve the properties of the dough. The usage of &agr;-amylases and xylanases is now widely spread. There are also oxidases and peroxidases which have a marginal, improving influence on the rheology of the dough, but this does not always means a better end product.
The use of polysaccharides as bread improvers is known and documented. The positive effect on dough rheology and on the total bread quality is always limited to specific cases or to combinations with other additives or ingredients. In most cases, guar gum is used, or locust bean gum, and if necessary carrageen or alginates (Ward F., 1993).
In practice, it is always by combining several of the above mentioned components that a commercial bread improver is created. The formulation of such a bread improver is adapted, according to the type of the end product, bread, rolls, or “Belgian pistolef”, “French baguette”, or according to the applied process: direct processing, retarded fermentation, deep frozen dough.
Although the possible combinations are endless, it is clear that the current additives and ingredients do not always meet the strict requirements of the modern bakery technology. Moreover, the use of certain additives is limited or prohibited by law. For instance, the use of bromate is forbidden in Europe, whereas it is limited in the U.S., on a voluntary basis. New ingredients which can replace existing chemical additives, or which have a new function, besides the currently existing additives are still being researched. Especially when they are based on natural products.
The ingredients mentioned above, and the additives for breads and rolls, are also used in pastry products. (cake, biscuit). In these pastry products, the volume of the baked end product is also one of the quality criteria besides, amongst others, softness and shelf life.
STATE OF THE ART
The use of dextrans in the field of bakery is not widely spread, although a number of applications have been described. The addition of dextrans in wheat doughs and the negative influence of this addition on the end quality of baked bread is known (Ross A. S. et al., J. Sci. Food Agric. 1992, 91-98; Ross A. S.: PhD Thesis, University of New South Wales (Australia), 1994 (XP000610156) & Dissertation Abstracts International, part 56, Nr. 7, p. 3524, 1996).
On the other hand, the Japanese patent application JP-07055124B2, the positive influence of dextrans on the softness and the shelf life of baked products has been proved. In addition, dextrans seem to have a small influence on the gassing power by yeast. This influence is comparable to other components such as locust bean gum, arabic gum, egg white, gelatine (Kolostori M., Elelmezesi Ipar 1978, 32(3), 107-112).
The U.S. Pat. No. 2,983,613 describes incorporating into the dough an amount of dextrans sufficient to soften the gluten content of the dough and to increase the specific volume of the resultant bakery product. This document describes that the bread which contains dextrans was about 20% greater in volume than products which do not contain dextrans.
Said dextrans are prepared by growing the micro-organism
Leuconostoc mesenteroides
B512, resulting in dextrans having a molecular weight from about 2×10
6
to about 4×10
6
dalton.
Dextrans have been described in EP-0153 013-A as bulking agent in formulations, suitable for enteral administration to man. This is mainly for diet reasons (low calorie) and for the treatment of a condition of the gastrointestinal tract in a human.
Dextrans can be synthesized by bacteria. Dextrans are &agr;-D-glucans, which are mainly composed of (1-6) linked &agr;-D-glucopyranosyl residues) They are mainly produced by bacteria which grow on a substrate, the only source of carbon being sucrose. These bacteria mainly belong to the group of lactic acid bacteria, and more specifically to the species of the Lactobacillus, Leuconostoc and Streptococcus. Examples of the producers of dextrans are to be found in the table below.
Lactobacillus
Leuconostoc
Streptococcus
L. acidophilus
L. dextranicum
S. bovis
L. brevis
L. mesenteroides
S. challis
L. casei
L. citreus
S. faecalis
L. pastorianus
S. mitis
L. confusus
S. mutans
L. sanfrancisco
S. sanguis
L. viridiscens
S. viridans
Purified dextrans are generally obtained by deproteinization of polysaccharides, which are isolated from the fermentation fluids.
Further purification is obtained by fractionated precipitation with alcohol or ketones. Dextrans which have a well defined molecular weight are obtained by partial hydrolysis.
The structure (such as length of the chain, degree of branching, type of links) of the dextrans are mainly defined by the bacteria subspecies, and less by the family, the genus, or the species. Some of the bacteria produced soluble and insoluble dextrans at the same time.
The basic structure of dextrans are (1-6) linked &agr;-D-glucopyranosyl residues. Sometimes, there are branchings at C-2, C-3, or C-4. Isolated (1-3) linked &agr;-D-glucopyranosyl residues or sequences of these residues can interrupt the (1-6) regions. All of the dextrans are more or less ramified, and the branching very much depends on the subspecies (Jeans A. et al., J. Am. Chem. Soc., 1954, 76, 5041-5052). Most of the branchings are composed of single &agr;-D-glucopyranosyl residues, although branchings have been found with 2-50 monomers. Some branchings are formed by (1-3) linked &agr;-D-glucopyranosyl residues.
Alternane is composed of glucose entities, which are alternately &agr;(1-6)- linked and &agr; (1-3) linked. It is amongst others produced by
Leuconostoc mesenteroides
NRRL B-1355.
Soluble dextrans are composed of sequences of (1-6) linked &agr;-D-glucopyranosyl residues, on which, at irregular intervals, branchings of single &agr;-D-glucopyranosyl residues are substituted.
Insoluble dextrans are more complex and they often contain more (1-3)linked &agr;-D-glucopyranosyl sequences.
Dextrans are synthesized by dextransucrase (E.C.2.4.1.5). The IUPAC name is sucrose: 1,6-&agr;-D-glucan 6-&agr;-D-glucosyltransferase (IUB, 1984). The enzyme is most frequently extracellular, and is induced by sucrose. The pH-optimum for the Leuconostoc dextransucrase lies between the pH 5.0 and pH 5.5 at the temperature of 29-34° C.
A procedure for the production and the isolation of dextransucrase of
Leuconostoc mesenteroides
is described by Ajongwen N. J. (Biotechnol. Lett., 1993, 9(4), 243-248).
Dextrans can also be synthesized by means of dextrine dextranase (E.C. 2.4.1.2) of for instance Acetobacter capsulatus ATCC 11894 Kazuya Yamamoto (Biosci., Biotech, Biochem. 1993, 57(9), 1450-1453).
The chain length of the dextrans depends on the conditions of fermentation. This means that the presence of acceptors such as maltose will influence molecular weight.
Dextrans form viscous solutions. These solutions show a Newtonian behavior when concentrations <30% w/w for low molecular weight dextrans. Dextrans with a higher molecular weight show a slightly pseudoplastic behavior when concentrations >1.5% w/w (McCurd

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