Food or edible material: processes – compositions – and products – Fermentation processes – Of plant or plant derived material
Reexamination Certificate
2002-06-13
2004-07-20
Hendricks, Keith (Department: 1761)
Food or edible material: processes, compositions, and products
Fermentation processes
Of plant or plant derived material
Reexamination Certificate
active
06764699
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for improving the Theological properties of corn packaged-tortillas by using commercial Xylanase with antimicrobial acidic-additives during tortilla making.
2. Description of Related Art
High-quality masa flour can be produced by conventional techniques only if the food-grade dent corn has the following characteristics: uniformity in kernel size and hardness, low stress-cracks and kernel damage and ease of pericarp removal during the lime-water cooking process. Nixtamalized corn flour (NCF) is produced by alkaline cooking of corn, washing, grinding the nixtamal and drying to give corn masa flour. This flour is sieved and blended for different product applications and it is usually supplemented with additives before packaging for commercial table tortilla and snack production. MASECA is the main brand flour in the US and Latin America, followed by Minsa, Agroinsa, Ill. Cereal Mills (Cargill) and Quaker Oats (Sustain, 1997).
Although the pericarp or bran is partially removed during the alkaline-cooking and washing process stages, there is still fiber left from the corn kernel (U.S. Pat. No. 4,513,018; Montemayor & Rubio, 1983, Ramirez & Alvarez, 1995). According to Watson (1987), the corn pericarp makes up 5-6% of the kernel dry weight. It also contains 67% hemicellulose, 23% cellulose and 0.6% soluble-fiber (soluble-hemicellulose). Unlike whole wheat, in which soluble fiber amounts to 11% of the total fiber, the corn soluble fiber is negligible (1%). Primary cell walls from the aleurone and starchy endosperm (83% dry weight) consist predominantly of arabinoxylan, &bgr;-glucan and some cellulose. It is estimated that mainly insoluble fiber in the pericarp and endosperm make up 78% of the total dietary fiber (9.5% in the kernel dry-weight).
Arabinoxylans are complex polymers (20,000-170,000 daltons) with a linear backbone of (1,4)-&bgr;-xylopiranosyl units to which substituents are attached through 02 and 03 atoms of the xylosil residues (mainly, &agr;-L-arabinofuranosyl; Fincher and Stone, 1986). A high degree of arabinosylation will increase its water solubility and more than 20% of the water in wheat-flour dough is associated with arabinoxylans. This polymer is apparently linked to the cellulose skeleton in the corn cell wall by ester linkage cross-bonding through ferulic and diferulic acid.
Nixtamalized corn flour or masa flour can contain from 7-9% of total dietary fiber or bran and 6-8% mainly consists of insoluble fiber on a dry-weight basis (Sustain, 1997). Dietary fiber of the new generation can surpass the functional and sensory qualities of the standard dietary fibers (e.g., commercial source of wheat bran can be removed of its starch, gluten and phytic acid). Due to its new fiber structure and its capillary effect the new fiber has good water binding capacity (twicefold) and a positive effect on baked goods freshness (e.g., Vitacel-brand name).
Haarasilta et al. (U.S. Pat. No. 4,990,343), Báez-Vásquez and Schoefield (1993) and Tanaka et al. (U.S. Pat. No. 5,698,245) have proposed that the use of endo and exo-hemicellulases causes decomposition of wheat insoluble fiber. Van Der Wouw et al (U.S. Pat. No. 6,066,356) also reported the use of arabinoxylanases to degrade the water-insoluble-solids from maize, in the preparation of feed or food (degermed maize and debranned wheat for bread).
Native Cellulose and Hemicellulose would render the dough non-homogeneous and affect the dough stretching capacity by preventing the formation of a gluten network (e.g., gliadin which provides elasticity and glutenin which effects viscosity). The enzyme treated bread product has an increased volume, more uniform grain structure, slower aging (retarded staling or retrogradation) and a reduction or replacement in baking additives.
Fiber components of Corn Kernel Parts
% Dry
Fiber
Soluble
Fiber
% Kernel
Part
matter
Insol.
Hemicellulose
Cellulose
Lignin
fiber
Total
fiber
Whole
100
9.5
6.7
3
0.2
0.1
9.5
100
Kernel
Starchy
80.9
1.0
—
—
—
0.5
1.5
12
Endo-
sperm
Aleurone
2.0
50.0
—
—
—
25.0
75.0
15
Endo-
Sperm
Germ
11.0
11.0
18
7
1.0
3.0
14.0
16
Pericarp
5.3
90.0
67
23
0.1
0.6
90.7
51
(bran)
Tip cap
0.8
95.0
70
—
2.0
—
95.0
6
Source: Watson, S. A. 1987. Structure and Composition, In: Corn Chemistry and Technology.
The benefit of using a xylanase instead of a traditional hemicellulase (pentosanase) preparation is that there are fewer side activities (e.g., &agr; or &bgr;-amylase, &bgr;-xylosidase/glucosidase) in the xylanase product. A suitable level of enzymes results in a desirable dough softening without causing stickiness, thereby improving machinability.
Xylanolytic systems (Wong and Saddler, 1992) include xylanases (1,4-&bgr;-D-xylan xylanohydrolase, EC 3.2.1.8) and &bgr;-xylosidases (1,4-&bgr;-D-xylan xylohydrolase, EC 3.2.1.37), the former generally hydrolyse the xylan backbone (endo-type) whereas the latter hydrolyse xylo-oligomers (exo-type). Xylose is not usually the major product and it is typically produced after xylobiose and xylotriose (smallest oligomer). Nonspecific xylanases from Trichoderma spp may attack cellulose and carboxymethylcellulose. Xylanases are classified into two major families (F or 10 and G or 11) of glycosylhydrolases. F10 xylanases are larger, more complex and produce low DP oligosaccharides (less specific); F11 are more specific for xylan (Jeffries, 1996). Low molecular weight xylanases (269-809 amino acid residues) were from
B. Pumilus, B. Subtilis
and
C. Acetobutylicum
(Wong and Saddler, 1992).
The xylanases can be prepared microbiologically by means of fungi and bacteria:
A. Niger
had shown not only arabinose releasing xylanase activity but also a xylotriose one, Trichoderma spp xylanases had optimal acitivity conditions between 45-65° C. and pH 3.5-6.5, Bacillus spp had alkaline tolerant (up to pH 10) and extreme thermophilic xylanases; and a Thermotoga sp (strain FjSS3-B1) xylanase had a temperature optimum of 105° C. at pH 5.5 and an half-life of 90 min at 95° C.
In recent years there has been a growing interest in the use of xylanase enzymes in the paper, pulp (enhance beatability and binding ability), food and feed industries. The use of xylanases (with or without cellulase and pectinase) has been proposed for clarifying juices and wine, for extracting coffee, plant oils and “starch”, for improving the nutritional properties of agricultural silage, for macerating plant cell walls, for producing food thickeners and for providing “textures to bakery products”. The scope for new applications is restricted mainly by the limited availability of specific xylanases with the required purity, properties (ie, pH optima and thermal stability) and action patterns (endo or exo-hydrolytic mechanisms). Commercial xylanase preparation marketed for pulp treatment include Pulpzyme HA (with little cellulolytic activity) from
T. Reesei
and Albazyme from
T. Longibrachiatum
. Crude enzyme preparations containing both hemicellulases and cellulases could be used to improve fibrillation and drainage properties of recycled pulpwood fibers (Wong and Saddler, 1992).
To aid in these developments, simple, reliable and sensitive procedures are required for the quantitative measurement of xylanase in a range of products with trace to high enzyme activity levels. The advent of genetic engineering has allowed the production of very specific enzyme preparations. A range of plant polysaccharides, including starch, &bgr;-glucan, arabinoxylan, fructans, as well as starch damage can be measured (McCleary, 1992).
López-Munguía et al. (Mexican patent application: No. 952,200) describes an enzymatic process to produce corn tortillas which retard accelerated staling with texture improvement during four days frozen storage. A fungal &agr;-amylase blend (i.e., commercial enzymes from Novo, Gist Brocades and Genencor International) was added during rehydration of nixtamalized corn flour (0.01 U/kg), and modified the starch during tortilla cooking up to the denaturing temperature (Iturbe-Chiñas et al
Baez Marco A.
Contreras Roberto
Rubio Manuel J.
Hendricks Keith
Roberto Gonzalez Barrera
Young & Thompson
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