Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1996-09-24
2000-08-15
Guzo, David
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536128, C08B 3000, C08B 3004, C08B 3020
Patent
active
061038938
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method of obtaining novel types of starch from potato plants, to novel potato plants from which the starch may be obtained, and to vectors for obtaining said plants.
BACKGROUND OF THE INVENTION
Starch is the major form of carbon reserve in plants. constituting 50% or more of the dry weight of many storage organs--e.g. tubers. seeds of cereals. Starch is used in numerous food and industrial applications. In many cases, however. it is necessary to modify the native starches, via chemical or physical means. in order to produce distinct properties to suit particular applications. It would be highly desirable to be able to produce starches with the required properties directly in the plant, thereby removing the need for additional modification. To achieve this via genetic engineering requires knowledge of the metabolic pathway of starch biosynthesis. This includes characterisation of genes and encoded gene products which catalvse the synthesis of starch. Knowledge about the regulation of starch biosynthesis raises the possibility of re-programming biosynthetic pathways to create starches with novel properties that could have new commercial applications.
The commercially useful properties of starch derive from the ability of the native granular form to swell and absorb water upon suitable treatment. Usually heat is required to cause granules to swell in a process known as gelatinisation, which has been defined (W. A. Atwell et al., Cereal Foods World 33, 306-311. 1988) as " . . . the collapse (disruption) of molecular orders within the starch granule manifested in irreversible changes in properties such as granular swelling, native crvstallite melting, loss of birefringence. and starch solubilisation. The point of initial gelatinisation and the range over which it occurs is governed by starch concentration, method of observation, granule type, and heterogeneities within the granule population under observation". A number of techniques are available for the determination of gelatinisation as induced by heating, a convenient and accurate method being differential scanning calorimetry, which detects the temperature range and enthalpy associated with the collapse of molecular orders within the granule. To obtain accurate and meaningful results, the peak temperature of the endotherm observed by differential scanning calorimetry is usually determined.
The consequence of the collapse of molecular orders within starch granules is that the granules are capable of taking up water in a process known as pasting, which has been defined (W. A. Atwell et al., Cereal Foods World 33, 306-311, 1988) as ". . . the phenomenon following gelatinisation in the dissolution of starch. It involves granular swelling, exudation of molecular components from the granule. and eventually. total disruption of the granules". The best method of evaluating pasting properties is considered to be the viscoamylograph (Atwell et al., 1988) in which the viscosity of a stirred starch suspension is monitored under a defined time/temperature regime. A typical viscoamylograph profile for potato starch is shown in FIG. 5, in which the initial rise in viscosity is considered to be due to granule swelling. At a certain point, defined by the viscosity peak, granule swelling is so extensive that the resulting highly expanded structures are susceptible to mechanically-induced fragmentation under the stirring conditions used. With increased heating and holding at 95.degree. C. further reduction in viscosity is observed due to increased fragmentation of swollen granules. This general profile (FIG. 5) has previously always been found for native potato starch. In addition to the overall shape of the viscosity response in a viscoamylograph, a convenient quantitative measure is the temperature of initial viscosity development (onset). FIG. 2 shows a typical viscosity profile for starch (Kennedy & Cabalda, Chem. in Britain. November 1991, 1017-1019), during and after cooking, with a representation of the physical s
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Cooke David
Gidley Michael John
Jobling Stephen Alan
Safford Richard
Sidebottom Christopher Michael
Guzo David
Kaiser Karen G.
Larson Thomas G.
National Starch and Chemical Investment Holding Corporation
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