Food or edible material: processes – compositions – and products – Products per se – or processes of preparing or treating... – Plant material is basic ingredient other than extract,...
Reexamination Certificate
1998-02-02
2001-07-31
Pratt, Helen (Department: 1761)
Food or edible material: processes, compositions, and products
Products per se, or processes of preparing or treating...
Plant material is basic ingredient other than extract,...
C426S465000, C426S520000
Reexamination Certificate
active
06268012
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dried product, and in particular, though not limited to a dried biological product in which the product is dehydrated to a water content of 20% or less. The invention is also directed towards a process for dehydrating a product, and in particular, though not limited to a process for dehydrating a biological product.
BACKGROUND ART
Many processes exist for drying products, such as various foods, fruits, vegetables, and other biological substances. For example WO89/08229 discloses a system and a method for drying granular material, in which the granular material is subjected to a drying agent, such as nitrogen.
It is also known to freeze-dry vegetables. Such a method is known to cause rupture of the cells and to increase the permeability of vegetables to water, see U.S. Pat. No. 4,788,072 at Column 2, Lines 15 to 20.
It is further known to dry fruit or vegetable slices by immersing said slices into a sugar solution, see for example, European Patent Specification No. EP-A-0,339,175. When using a sugar solution with a high Dextrose equivalent (DE) value, for example, a DE value of 70, low molecular weight sugars are able to penetrate into the cells, whereby a higher sugar content exists. Such dried products may not have a water activity lower than 0.4, and some of the contents of the cell, such as flavour and odour constituents, may no longer be present in the interior of the cell.
When using a sugar solution with a low DE value, for example, a DE value of 25, sugars are extracted from the product. This dried product also may not have a water activity lower than 0.4.
Furthermore, it is considered that due to the extraction of sugars, the taste and odour characteristics of the product may be altered.
The sugar osmotic drying is also considered as a pre-treatment, that is, a treatment for lowering the water content of the product before a final drying treatment, such as frying. The water content of the osmotically dried product may thus not be low enough to preclude spoilage of the product without additional measures, such as refrigeration, sterile packaging or the addition of preservatives. Due to the treatment of the product in a liquid sugar solution, sugar may completely fill the voids or spaces situated between two adjacent cell membranes.
It is further known to dry grapes by spraying them before harvesting with a composition to facilitate removal of water from the grapes, see U.S. Pat. No. 5,068,988. The dried grapes retain a sufficiently high water content so as to produce sufficient juice for making wine. The wines obtained by using such dried grapes have a high alcohol content.
It is also known to dry timber using a carefully regulated temperature and humidity regime during the drying process. The temperature and humidity regime is species- and size-specific and is selected to ensure that the drying operation does not cause warping of the product as a result of excessive moisture and temperature gradients within the material. The drying process results in a longer drying time than would result from drying without humidity regulation. Details of such drying processes are presented in a large number of standard works, for example, in the 1991 ASHRAE Handbook, HVAC Applications.
It is generally accepted in the known art that “Based on the analysis of heat and mass transfer, the most efficient dehydration systems will maintain the maximum vapour-pressure gradient and the maximum temperature gradient between the air and the interior parts of the product”, see Introduction to Food Engineering, R. P. Singh and D. R. Heldman, Academic Press (1993), at Page 422.
It is also generally accepted that in known drying processes the outer layer of the product becomes essentially impermeable to aroma compounds but still transmits some water vapour to allow drying to continue, see for example, “Food Dehydration”, G. V. Barbosa-Canovas and M. R. Oaks eds., A.I.Ch.E. Symposium Vol 89 (1993), Page 32.
Finally, PCT Application Specification No. WO 94/13146 of one of the co-inventors of the present invention discloses a method and an apparatus for dehydrating biological products in which a closed system is used so as to ensure the retention of the essential flavour and fragrance of the natural product.
DEFINITIONS
In this specification and in the claims, the following words and terms as used herein have the following meanings:
Water content of an undried substance, in other words, a substance prior to being dried is given as a percentage of the total weight of the undried substance.
Water content of a dried substance is given as a percentage of the total weight of dry matter only of the dried substance excluding all moisture.
A hygroscopic substance is one in which the water content tends to equilibrate with its surroundings.
Water activity of a hygroscopic substance is defined as the equilibrium relative humidity of a closed and thermally insulated system in which the substance has been placed. The measurement thereof should take place with a minimum head space and generally in conformity with recognised procedures for measurement of water activity. So in principle, the water activity is no different from equilibrium relative humidity except that it is expressed in terms of a scale from 0-1, instead of on a scale of from 0-100%. The water activity measures the degree of freedom of water, retained in various ways, in a hygroscopic substance.
The water activity directly determines the physical, mechanical, chemical and microbiological properties of a hygroscopic substance, for example, interactions such as clumping, cohesion, electrostatic charge, and so on. In the food industry, the water activity is a highly significant factor to be considered for the conservation of semifinished and finished products.
In particular, the water activity threshold for deteriorative mechanisms in a given hygroscopic food substance is defined as a level of water activity above which significant oxidation, enzymatic browning, microbiological organic activity and other deteriorative processes begin to take place to the detriment of the organoleptic and nutritional characteristics of that substance. For example, the proliferation of micro-organisms is generally considered to be suppressed at water activity levels below about 0.65. Other deteriorative processes become progressively less active as the water activity decreases toward a value between 0.2 and 0.25, that is, towards a level: approximately corresponding to the monolayer water content.
Cellular structure of a substance means the structure of the cells of the substance, and also means the general arrangement of the cells, whereby intercellular spaces, channels or passageways are defined between the cells, and reference to damage to the cellular structure, in general, refers to damage caused to the cellular structure during a dehydrating process, it being understood that the cells and cellular structure adjacent a face of the product may be damaged prior to the dehydrating process, as a result, for example, of cutting the substance or product into slices or the like.
Cellular integrity of a substance refers to the degree to which the cellular structure of the substance is unaltered or undamaged, and in particular, the degree to which the cell walls remain intact for retaining the organoleptic characteristics of the product. Reference to the maintenance of cellular integrity during a dehydrating process is defined as the maintenance of the integrity of the cellular. structure, which the substance had prior to being dried throughout the drying process so that at the end of the dehydrating process the dried product can be rehydrated to substantially its original form in substantially all respects.
Structural intearitv of a substance refers to the degree to which the structure of the substance is unaltered or undamaged, including its cellular structure. Reference to maintenance of structural integrity during a drying process is defined as the maintenance of the integrity of the structure, which the substance
Grocholski Wlodzimierz Ludwik
Sikora Paul Thomas
DTL S.A.
Garrison David L.
Garrison & Associates PS
Pratt Helen
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