Food or edible material: processes – compositions – and products – Surface coated – fluid encapsulated – laminated solid... – Having inedible feature
Patent
1997-01-23
1999-09-28
Bhat, Nina
Food or edible material: processes, compositions, and products
Surface coated, fluid encapsulated, laminated solid...
Having inedible feature
426293, 426305, 426308, 426310, A23G 300, A23L 1216
Patent
active
059584807
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a method for producing a biologically degradable polyhydroxyalkanoate coating, wherein an aqueous dispersion of polyhydroxyalkanoate is applied to the surface to be coated. In particular, the invention relates to the coating of surfaces which form part of a product to be supplied for consumption to a human being or animal and/or surfaces which form part of a product which is not resistant to high temperatures. A suitable example of a product to be coated is a foodstuff, in particular cheese. The invention also relates to objects coated with such a polyhydroxyalkanoate coating, and also to elastomeric, films of polyhydroxyalkanoate and latices thereof. Elastomeric means the polyhydroxyalkanoates behave at room temperature as elastomers, wherein the crystals serve as physical crosslinks providing a minimum elongation at break of 50%.
Poly(3-hydroxyalkanoates) (PHA) are biologically degradable polymers which can be accumulated by microorganisms as sources of carbon and energy (Anderson and Dawes 1990. Microbiol. Rev. 54: 450-472). Poly(3-hydroxybutyrate) (PHB) and the copolymer poly(3-hydroxybutyrate)-co-valerate (PHB/HV) are the most known and best studied forms of PHA and are classified as polyhydroxyalkanoates of the PHB type. In the past ten years, a large number of new types of PHA have been found. In particular, Pseudomonas strains have proved to be capable of synthesizing PHAs with diverse compositions (Lageveen et al. 1987, Appl. Environ. Microbiol. 54, 2924-2932). These polyhydroxyalkanoates comprise 3-hydroxy acids having a carbon-chain length of C.sub.6 -C.sub.14 and are termed polyhydroxyalkanoates of the PHA type.
In order to be able to use polyhydroxyalkanoates, they must be derived from biomass and separated from contaminating cell parts such as proteins and lipids. Two important working-up strategies have been developed for PHB and PHB/HV. The first method relates to an extraction with a solvent such as methylene chloride, dichloroethane, chloroform or trichlorobenzene (Lafferty et al. 1988, Biotechnology vol. 6b. 136-176). The disadvantage of this method is that the organic solvents used are toxic and environmentally unacceptable. The use of these solvents would not only make the working-up of PHAs expensive but also considerably limit the number of possible applications of PHAs. All the applications in which PHAs come into contact with products to be applied to or consumed by a human being or animal, such as foodstuffs, are ruled out in this case because small residues of the solvent which is harmful to health can, after all, always be present.
In the second working-up method, the bacteria cells containing PHB/HV are broken open by means of a combined physical, chemical and enzymatic procedure. In this way, the PHB/HV granules are released from the biomass and an aqueous dispersion is produced. viz. a latex. The aqueous PHB/HV dispersion is further purified of cell constituents by means of rinsing steps and centrifugation. A dry PHB/HV powder which can be processed further to produce, for example, foils, small bottles, fibres etc. can then be obtained by means of spray drying the dispersion (Holmes 1985, Phys. Technol. 16, 32-36).
With a view to the environmental requirements, great need has arisen for biologically degradable products. This certainly applies to products which comprise a solid support with a coating. Processing of PHA to form such a coating is an interesting field of application. It is known of PHB and the copolymer PHB/HV that they can be processed in various ways to form a coating. In the first place, by applying a PHB solution in an organic solvent such as chloroform to the surface of the coated agent and allowing the solvent to evaporate. It is clear that this is a very unacceptable method for environmental reasons.
In a second approach, use is made of an aqueous dispersion of PHB, PHB remaining behind as a powder on the surface of the agent to be coated after evaporation of the water. The PHB granules do not fuse and films ca
Eggink Gerrit
Northolt Martin Dinant
Bhat Nina
Stichting Onderzoek en Ontwikkeling Noord-Nederland (SOONN)
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