Food or edible material: processes – compositions – and products – Direct application of electrical or wave energy to food... – Heating by electromagnetic wave
Reexamination Certificate
2000-02-16
2001-07-10
Bhat, Nina (Department: 1761)
Food or edible material: processes, compositions, and products
Direct application of electrical or wave energy to food...
Heating by electromagnetic wave
C426S244000, C530S370000, C530S377000, C530S378000
Reexamination Certificate
active
06258393
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process and a device for gentle modification of functional properties of a protein preparation, preferably of protein isolate or concentrate from vegetable seeds, by heating the protein preparation, for the production of fresh or dry products as a base material or an additive for protein-containing foodstuffs.
STATE OF THE ART
In order to utilize proteins, preferably for the production of foodstuffs, naturally occurring proteins have to first be extracted from their natural occurrence and, depending on the application, have to be treated to determine their functional properties, such as for instance their water-binding properties, dispersive power and oil-binding behavior, just to name a few, in a specific manner.
As is well-known, vegetable proteins are obtained as protein concentrates or protein isolates by means of extraction from the vegetable seeds. Principally, solvents, which in the case of the extraction of protein concentrates usually are aqueous, alcoholic solutions or water, are used to extract proteins from vegetable seeds; whereas in the extraction of protein isolates, saline solutions or water containing additives of alkaline solutions, for example NaOH, or water containing additives of acids, for example HCl, are usually employed. Known extraction methods are described in D. K. Salunkhe's book “World Oilseed”, Chemistry, Technology and Utilization”, 1992, New York.
FIG. 2
shows in a flow chart two alternative prior art processes for the extraction of protein concentrates and protein isolates. From an oil or protein raw material, such as for instance soybean, the oil is extracted from the protein raw material after grinding, pressing and/or hexane extraction in such a manner that the residue is a protein-rich flour. The left branch of the process of
FIG. 2
shows known procedures for extracting protein concentrates. The protein-rich flour is extracted while adding aqueous, alcoholic solvents so that a wet protein concentrate containing up to 80% extract parts is yielded. In this manner the obtained, wet protein concentrate can be further treated by adding other reagents or introducing mechanical energy by grinding and/or stirring or by heating in order to alter the properties of the protein concentrate. In order to obtain the desired protein concentrate in a, for the most part, dry state, drying steps are provided which usually occur by means of thermal energy input.
An alternative to the extraction of protein concentrates is the extraction of protein isolates according to the procedure shown in the right branch of the flow chart of FIG.
2
. In this process, the protein-rich flour is extracted by adding alkaline liquids with the wet flour parts precipitating. By adding acidic reagents and centrifuging, the protein extract yielded by alkaline extraction is separated into whey and protein curd. The functional properties of the curd can subsequently be manipulated in the desired manner by dilution, pasteurization, neutralization or modification. The extraction of protein isolates, too, requires a subsequent drying step.
The functional properties of proteins can also already be influenced when processing the seed, extracting the protein, or by selective modification, which occurs with the protein isolate. For this also see J. E. Kinsella's paper “Functional Properties of Soy Proteins”, Journal of Am. Chem. Soc., 56 (1979), pp. 242 to 246.
The purpose of modification is to obtain protein products with selectively determined functional properties. Proteins possess, depending on their protein structure and/or pH values, good solubility or good water-binding capacity, which are particularly important when used as an additive in sausage and meat products. Especially, the water-binding capacity of proteins when used in sausage and meat products is a property of major significance. The functional property of water-binding can, for instance, be improved by selective thermal denaturing of the protein structure.
There are processes known, for instance processing lupine seeds by roasting, boiling, peeling and finely grinding, which lead to altering and determining the functional properties of the lupine flour gained in this manner. The products obtained this way are offered for binding oil and water in foodstuffs as well as for improving their texture. French patent FR 2 660 163 A1 describes such a process. However, a drawback is that the products obtained with this process possess only a limited protein content of maximally 45%. Thus, these products correspond to the natural seed composition and are not protein concentrates or protein isolates.
J. King and C. Aguirre's paper, “Functional Properties of Lupin Protein Isolates”, Journal of Food Science, 50(1985), pp. 82 to 87 describes a process for extracting protein isolates from lupines and notes the possibility of modifying the functional properties of the proteins. Heating the protein samples influences both their gelling property and their water-binding capacity positively. In order, for example, to increase the gelling property of the protein isolates, the concentration of the protein isolates is raised during heating, thereby, however, leading to high viscosity of the protein sample.
Heating such high-viscous protein samples, however, harbors the difficulty of uniform heating. Therefore, indirect heating processes have been proposed, which, however, require special heat exchangers, for example coaxial heat exchangers, and consequently are expensive devices. The slow flow properties of high-viscous protein preparations and the utmost necessity of avoiding overheating, for example on the wall of the heat exchanger, contribute to the need of additional, large and therefore expensive constructions. On the other hand, reducing the viscosity of the protein preparations by adding water, would increase the cost and complexity of processing further especially during drying.
However, with the aforedescribed convective thermal heating method, one is able to attain only uniform heating of the entire volume of the protein preparation if the preparations are, if diluted with water, a light, stirrable or flowable dispersion so that the structure change can set in uniformly throughout the entire protein preparation volume. When using convective thermal heating to heat a highly concentrated protein dispersion, proteins, particularly, cake readily on the heating surfaces of the heat exchanger device because the immediate thermal input is the greatest at these contact surfaces.
Moreover, thermal convection inside the to-be-heated protein preparation is accompanied by severe temperature gradients, which counteract the uniform determination of the functional properties throughout the entire protein preparation volume.
DESCRIPTION OF THE INVENTION
The object of the present invention is to further improve a process for the gentle modification of the functional properties of a protein preparation, preferably of protein isolates or protein concentrates from vegetable seeds, by heating the protein preparation, for the production of fresh or dry products as a base material or additive for protein-containing foodstuffs, in such a manner that a defined, selective, uniform determination of the functional properties is possible throughout the entire protein preparation volume. In particular, the drawbacks related to conventional heating with thermal convection should be avoided. Furthermore, a device for heating a protein preparation gently should be provided which is inexpensive and not complicated
A key element of the present invention is that a process for the gentle modification of the functional properties of a protein preparation, preferably of protein isolates or concentrates from vegetable seed, by heating the protein preparation, for the production of fresh or dry products as a base material or additive for protein-containing foodstuffs, is further improved in such a manner that the protein preparation is exposed to an electromagnetic high-frequency field by means of which t
Luck Thomas
Pfeiffer Thomas
Waesche Andreas
Antonelli Terry Stout & Kraus LLP
Bhat Nina
Fraunhofer Gesellschaft zur Forderung der angewandten Forschung
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