Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Food or edible as carrier for pharmaceutical
Reexamination Certificate
1998-03-19
2002-11-19
Travers, Russell (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Food or edible as carrier for pharmaceutical
C424S439000, C424S440000, C426S573000
Reexamination Certificate
active
06482430
ABSTRACT:
This application claims foreign priority of GB 9705739.2 titled Aug. 28, 1997, and GB 970579.2 titled Mar. 20, 1997.
The present invention relates to hemicellulosic cereal extracts suitable as substrates for oxidative gelation (“gelling hemicelluloses”), to gels prepared therefrom, to processes for their production, to products containing such gels and to various applications thereof. In particular, the present invention relates to an improved process for preparing gelling hemicelluloses from cereals (especially wheat).
The term “hemicellulose” and “hemicellulosic material ” are terms of art used to embrace non-cellulosic, non-starch plant polysaccharides. The term therefore embraces inter alia pentosans, pectins and gums.
Some hemicelluloses are suitable as substrates for oxidative gelation (“gelling hemicelluloses”): such hemicelluloses often have substituents with phenolic groups which are cross-linkable with certain oxidizing agents.
Arabinoxylan and pectin constitute two particularly important classes of hemicellulose. Arabinoxylans consist predominantly of the pentoses arabinose and xylose, and are therefore often classified as pentosans. However, in many cases hexoses and hexuronic acid are present as minor constituents, and therefore they may also be referred to descriptively as heteroxylans.
The arabinoxylan molecule consists of a linear backbone of (1-4(-&bgr;-xylopyranosyl units, to which substituents are attached through 02 and 03 atoms of the xlosyl residues. The major substituents are single &agr;-L-arabinofuranosyl residues. Single &agr;-D-glucoronopyranosyl residues and their 4-O-methyl ethers are also common substituents.
Arabinoxylan preparations are usually heterogeneous with respect to the ratio of xylose to arabinose (i.e. the degree of substitution) and in the pattern of substitution of the arabinosyl units along the (1-4)-&bgr;- xylan backbone.
Phenolic acid including ferulic acid) and acetyl substituents occur at intervals along the arabinoxylan chains. These substituents to some extent determine the solubility of the arabinoxylan. Arabinoxylan preparations bearing phenolic (e.g. ferulic acid substituents) are referred to herein as “AXE”, while those bearing acetyl substituents are designated “AXA”. Similarly, preparation bearing both phenolic (e.g. ferulic acid, and acetyl substituents are hereinafter abbreviated to the designation “AXFA”. Arabinoxylan preparations having few phenolic (e.g. ferulic acid, substituents are designated “AX”: when the degree of substitution falls below that required for oxidative gelation, the arabinoxylan is designated a “non-gelling arabinoxylan” (a term which therefore embraces AX and AXA).
Pectins constitute another important class of hemicelluloses. As used herein and unless otherwise indicated, the term “pectin” is used sensu lato to define hemicellulose polymers rich in D-galacturonic acid. Many (but not all) are cell wall components. The term “pectin” is also used herein sensu stricto to define the so-called “true pectins”, which are characterized by the presence of an O-(&agr;-D-galacturonopyranosyl)-(1-2)-L-rhamnopyranosyl linkage within the molecule.
The pectins may be subcatergorized on the basis of their structural complexity. At one extreme are “simple pectins”, which are galacturonans. At the other extreme are “complex pectins” exemplified by rhamnogalacturonan II, which contains at least 10 different monosaccharide components in the main chain or as a components of branches. Pectins of intermediate complexity (herein referred to as “mesocomplex pectins” contain alternate rhamnose and galacturonic acid units, while others have branches of glucoronic acid linked to galacturnoic acid.
Complex and mesocomplex pectins are made up of “smooth” regions (based on linear homogalacturonan) and “hairy” regions corresponding to the rhamnogalacturonan backbone with side-branches of varying length.
Certain pectins (for example, pectins obtainable from representatives of the plant family Chenopodiaceae, which include beets (e.g. sugar beet), spinach and mangelwurzels) are substituted to some extent with substituents derived from carboxylic acids (usually substituted cinnamic acids) containing phenolic groups. Such pectins may be oxidatively cross-linked to produce viscous solutions or gels via their phenolic substituents. This can be achieved by powerful oxidants (e.g. persulfate - see J. - F. Thibault et alia, in
The Chemistry and Technology of Pectin,
Academic Press 1991, Chapter 7, pages 119-133) or a combination of peroxidase and hydrogen peroxide (see Thibault et alia, ibidem). Fr 2 545 101 Al also describes the gelling of beet pectins using an oxidant (e.g. hydrogen peroxide) and an enzyme (peroxidase). Such pectins are referred to herein as “gelling pectins”.
Sugar beet pectin is especially rich in arabinan. Arabinan contains &bgr;-1,5-linked arabinose in the backbone with &agr;-(1->3) or &agr;-(1->2)-linked arabinose residues, whereas arabinogalactan contains &bgr;-1,4-linked galactose in the backbone, with &agr;-(1->3) or a &agr;-(1->2) linked arabinose residues. Ferulyl substituents are linked to the arabinose and/or the galactose in the arabinan and arabinogalactan side-branches of the rhamnogalacturonan part. The “ferulic acid” content varies according to the extraction method, but is often about 0.6%.
Beet pectins obtained by processes which partially remove arabinose residues may exhibit improved gelling properties. Thus, procedures involving mild acid treatment and/or treatment with an &agr;-arabinofuranosidase will improve the gelling properties of the pectin (see F. Guillon et alia ibidem). Such pectins are hereinafter referred to as “treated pectins”.
It has long been known that certain flour extracts (e.g. wheat and rye flour extracts) can form gels in the presence of certain oxidants (e.g. upon the addition of hydrogen peroxide). The phenomenon is known in the art as “oxidative gelation”, and an extensive literature exists on the subject of oxidative gelation of wheat flour extracts. According to the literature, the gels arise as high molecular weight arabinoxylan and protein molecules become inter- and/or intra-linked (via inter alia diferulate bridges) - see e.g. Hoseney and Fabuion (1981), Cereal Chem., 58: 421.
Most of the work in this area has focused on water soluble pentosans from wheat flour. In these studies, wheat flour is extracted with water (usually at room temperature) to yield gelling arabinoxylans. However, water-insoluble wheat pentosans extracted from wheat flours with various concentrations of cold sodium hydroxide have also been shown to form gels (Michniewicz et alia, Cereal Chemistry 67(5): 434-439 (1990).
WO 93/1058 describes the preparation of hemicellulosic material from various brans and the oxidative gelation of maize-derived hemicelluloses using an oxidizing system comprising a peroxide, (such as hydrogen peroxide) and an oxygenase (such as a peroxidase). The hemicellulosic material for use as a gelling agent is prepared by hot water or mild alkali extraction.
However, gelling hemicelluloses from some cereal sources (including wheat) produced by known processes form gels which are unsatisfactory for many uses. Such gels are generally opaque, relatively soft, pigmented and exhibit marked syneresis on storage. These properties limit their utility in many potential fields of application (including food technology and the pharmaceutical industry).
There is therefore a need for improved methods of producing gelling hemicelluloses from testaceous cereal fractions (e.g. cereal brans) which exhibit improved gelling characteristics and which do not exhibit these undesirable properties.
It has now been discovered that the undesirable characteristics of the gels produced from certain hemicellulosic bran extracts arise from the presence of contaminating proteins. In certain brans (e.g. many what brans and other bran sources which contain residual endosperm material), such proteins are present at concentrations sufficient to impair or prevent the gelation (or to impair the p
Fitchett Colin Stanley
Greenshields Roderick
Weightman Richard Mark
Cambridge Biopolymers Limited
Heller Ehrman White & McAuliffe
Travers Russell
Wang Shengjun
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