Food or edible material: processes – compositions – and products – Fermentation processes – Of farinaceous cereal or cereal material
Reexamination Certificate
2001-02-28
2003-12-23
Hendricks, Keith (Department: 1761)
Food or edible material: processes, compositions, and products
Fermentation processes
Of farinaceous cereal or cereal material
C426S549000
Reexamination Certificate
active
06667065
ABSTRACT:
FIELD OF THE PRESENT INVENTION
The present invention relates to proteins, especially proteins that are capable of degrading starch.
In particular, the present invention relates to the use of proteins that are capable of retarding the detrimental retrogradation of starch.
Detrimental retrogradation processes, such as staling, typically occur after the heating and cooling of starch media, in particular aqueous starch suspensions, and are due to transformation of gelatinised starch to an increasingly ordered state.
More in particular, the present invention relates to the use of proteins that are capable of retarding the detrimental retrogradation of amylopectin.
More in particular, the present invention relates to the use of proteins to prepare baked bread products, as well as to the baked bread products themselves.
More in particular, the present invention relates to retardation of staling in baked farinaceous bread products.
More specifically the present invention relates to a process for making a baked farinaceous bread product having retarded or reduced staling, comprising adding a non-maltogenic exoamylase to the bread dough.
The present invention also relates to an improver composition for dough and baked farinaceous bread products comprising a non-maltogenic exoamylase.
BACKGROUND OF THE PRESENT INVENTION
Starch comprises amylopectin and amylose. Amylopectin is a highly branched carbohydrate polymer with short &agr;-(1→4)-D-glucan chains which are joined together at branch points through &agr;-(1→6) linkages forming a branched and bushlike structure. On average, there is one branch point for every 20-25 &agr;-(1→4) linked glucose residues. In contrast, amylose is a linear structure mainly consisting of unbranched &agr;-(1→4)-D-glucan units. Typically, starches contain about 75% amylopectin molecules and about 25% amylose molecules.
More specifically, linear malto-oligosaccharides are composed of 2-10 units of &agr;-D-glucopyranose linked by an &agr;-(1→4) bond. Due to their properties such as low sweetness, high waterholding capacity, and prevention of sucrose crystallisation [1] these compounds have potential applications in the food industry. The preparation of malto-oligosaccharides with a degree of polymerisation (DP) above 3 (i.e. DP>3) in larger amounts is however tedious and expensive.
As background information, DP1=glucose, DP2=maltose, DP3=maltotriose, DP4=maltotetraose, DP5=maltopentaose, DP6=maltohexaose, DP7=maltoheptaose, DP8=maltooctaose, DP9=maltononaose, and DP10=maltodecaose.
The discovery of microbial enzymes, which produce malto-oligosaccharides of a specific length could allow the production of larger amounts of these oligosaccharides [2].
Amylases are starch-degrading enzymes, classified as hydrolases, which cleave &agr;-D-(1→4) O-glycosidic linkages in starch. Generally, &agr;-amylases (E.C. 3.2.1.1, &agr;-D-(1→4)-glucan glucanohydrolase) are defined as endo-acting enzymes cleaving &agr;-D-(1→4) O-glycosidic linkages within the starch molecule in a random fashion [3]. In contrast, the exo-acting amylolytic enzymes, such as &bgr;-amylases (E.C. 3.2.1.2, &agr;-D-(1→4)-glucan maltohydrolase), and some product-specific amylases cleave the starch molecule from the non-reducing end of the substrate [4]. &bgr;-Amylases, &agr;-glucosidases (E.C. 3.2.1.20, &agr;-D-glucoside glucohydrolase), glucoamylase (E.C. 3.2.1.3, &agr;-D-(1→4)-glucan glucohydrolase), and product-specific amylases can produce malto-oligosaccharides of a specific length from starch.
Several amylases producing malto-oligosaccharides of a specific DP have been identified previously including maltohexaose-producing amylases from
Klebsiella pneumonia
[5, 6
], Bacillus subtilis [
7
], B. circulans
G-6 [8
], B. circulans
F-2 [9, 10], and
B. caldovelox
[11, 12]. Maltopentaose-producing amylases have been detected in
B. licheniformis
584 [13] and Pseudomonas spp. [14, 15]. Furthermore, maltotetraose-producing amylases have been reported from
Pseudomonas stutzeri
NRRL B-3389 [16, 17], Bacillus sp. MG-4 [18] and Pseudomonas sp. IMD353 [19] and maltotriose-producing amylases from
Streptomyces griseus
NA-468 [20] and
B. subtilis
[21].
EP-B1-298,645 describes a process for preparing exo-maltotetraohydrolase of
Pseudomonas stutzen
or
P. saccharophila
using genetic engineering techniques.
U.S. Pat. No. 5,204,254 describes a native and a genetically modified exo-maltopentao-hydrolase of an alkalophilic bacterium (DSM 5853).
Very few product-specific amylases active at high pH have been identified. Examples of those that have been identified include amylases from Bacillus sp. H-167 producing maltohexaose [22, 23], from a bacterial isolate (163-26, DSM 5853) producing maltopentaose [24], from Bacillus sp. IMD370 producing maltotetraose and smaller malto-oligosaccharides [25], and from Bacillus sp. GM 8901 that initially produced maltohexaose from starch which was converted to maltotetraose during extended hydrolysis periods [26].
Starch granules heated in the presence of water undergo an order-disorder phase transition called gelatinization, where liquid is taken up by the swelling granules.
Gelatinization temperatures vary for different starches and depend for the native, unmodified starches on their biological source.
Cooling converts the gelatinised phase into a viscoelastic paste or elastic gel, depending on the starch concentration. During this process, amylose and amylopectin chains reassociate to form a more ordered structure. With time, more associations are formed and they become even more ordered. It is believed that associations of amylopectin chains DP 15-20 lead to a thermoreversible, quasi-crystalline structure.
In consequence of detrimental retrogradation, the water-holding capacity of the paste or gel system is changed with important implications on the gel texture and dietary properties.
It is known that the quality of baked bread products gradually deteriorates during storage. The crumb loses softness and elasticity and becomes firm and crumbly. This so-called staling is primarily due to the detrimental retrogradation of starch, which is understood to be a transition of the starch gelatinised during baking from an amorphous state to a quasi crystalline state. The increase in crumb firmness is often used as a measure of the staling process of bread.
Upon cooling of freshly baked bread the amylose fraction, within hours, retrogrades to develop a network. This process is beneficial in that it creates a desirable crumb structure with a low degree of firmness and improved slicing properties. More gradually crystallisation of amylopectin takes place within the gelatinised starch granules during the days after baking. In this process amylopectin is believed to reinforce the amylose network in which the starch granules are embedded. This reinforcement leads to increased firmness of the bead crumb. This reinforcement is one of the main causes of bread staling.
The rate of detrimental retrogradation or crystallisation of amylopectin depends on the length of the side chains of amylopectin. In accordance with this, cereal amylopectin retrogrades at a slower rate than amylopectin from pea or potato, which has a longer average chain length than cereal amylopectin.
This is supported by observations from amylopectin gel systems that amylopectin with average chain length of DP, i.e. degree of polymerisation, ≦11 do not crystallise at all. Furthermore the presence of very short chains of DP 6-9 seems to inhibit the crystallisation of surrounding longer side chains probably because of steric hindrance. Thereby these short chains seem to have a strong anti-detrimental retrogradation effect. In accordance with this, amylopectin retrogradation is directly proportional to th
Duedahl-Olesen Lene
Kragh Karsten M.
Larsen Bjarne
Rasmussen Preben
Zimmermann Wolfgang
Danisco A/S
Foley & Lardner
Hendricks Keith
LandOfFree
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