Measuring and testing – Moisture content or absorption characteristic of material – By desiccation or extraction
Reexamination Certificate
2000-06-15
2001-06-26
Williams, Hezron (Department: 2856)
Measuring and testing
Moisture content or absorption characteristic of material
By desiccation or extraction
C073S073000, C073S074000
Reexamination Certificate
active
06250139
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
Reference to a Microfiche Appendix
Not Applicable
Technical Field
This invention relates to a process as well as a moisture-measuring device for powders, grains and for the dry matter of liquid products. It therefore applies to numerous domains including food and agricultural products, such as milk, coffee, cocoa, tea, cereals and the like, as well as coal, paper, tobacco, and other products.
Background of the Invention
In order to establish water content, most international prescriptions FIL-IDF, ISO, AOAC, OICCC, IC, CCE including the Codex Alimentarius, recommend a gravimetric method whereby both the moisture and the dry matter of the sample are determined. Gravimetric analysis entails the drying of the product in an oven to constant weight, i.e., one where the difference in two successive weighings does not exceed 0.5 mg. The works carried out in rooms with controlled temperature and humidity revealed that results are significantly influenced by the prevailing climatic conditions. The humidity percentages of a same sample determined by the same analytical method can differ as much as 1.5%, according to where the analysis is made. For example, a sample exhibiting a 3% humidity content in Geneva (where the climatic conditions are 3 g water per m
3
air) may only yield a 2% humidity content in Sâo Paulo (where the climatic conditions are 26 g water per m
3
).
Brief Summary of the Invention
The invention relates to a process for measuring moisture in powders or grains, or for measuring dry matter of liquid products, wherein the sample and the dish are weighed together and then introduced into an air-tight glass tube through which a gas flows in order to remove any water produced by the sample, the water is thus eliminated in a closed circuit independently of climatic conditions. In this process, the loss in mass occurs firstly because of the individual heating of the product with the possibility of setting several different temperatures ranging from 40 to 150° C. and secondly because of the reduced pressure ranging from 10 mbar to atmospheric pressure. Also, the cooling of the dried product occurs within the tube under reduced pressure till ambient temperature is reached and by the fact the weighing is carried out only once the vacuum has been stopped and the atmospheric pressure recovered and the dish is extracted from the tube and is subsequently weighed with its cover on an analytical balance.
Advantageously, the gas used is nitrogen which first flows through a molecular sieve to remove any water traces before carrying the water produced by the sample towards the exterior of the tube, and that the reduced pressure within the tube created by the pump helps remove the last remaining traces of water in the product and in the tube. Preferably, the dry gas is introduced directly from a source within the whole device and that it is introduced through a medicinal needle with a lateral orifice to prevent it from being closed by the rubber of a septum at the extremity of the tube.
The invention also relates to a method for measuring the moisture content of powders or grains or for measuring the dry matter of liquid products, which comprises the steps of placing the product on a scoop and weighing it, inserting the product and scoop in a sealed glass tube, and passing a dry gas stream over the product to evacuate water content outside of the tube, with the water evacuation step is carried out in a closed circuit independently of ambient air in the place where the product is being analyzed before measuring the drained product.
Another embodiment of the invention relates to a measuring device for carrying out the method. The device includes a source of dry gas, one or several sheaths into which the glass tubes are fitted, a gas regulator, a manometer, a pump and by the fact that the glass tube is fitted at one end with a screw thread and a rubber septum which ensures that the device is air-tight when it is pierced by a needle and at the other end by a spherical rod equipped with a stopcock. Depending upon the products to be analyzed, the device advantageously permits individual heating and pressure conditions into each tube independently from one another. For example, when a 6 sheath device is utilized, six different temperatures may be set and six different products analyzed. The device preferably includes heating sleeves which wrap a steel sheath in which the glass tube is lodged.
Alternatively, a measuring apparatus for implementing the method includes the sealed glass tube, a dry gas source, one or several sheaths or cells which house the glass tube and which are used for draining the product, gas flow regulators, one or several manometers, and a pump.
REFERENCES:
patent: 4964734 (1990-10-01), Yoshida et al.
patent: 271 757 (1989-06-01), None
patent: 0 344 465 (1989-06-01), None
A. Klein, “Causes of error of the Oven Method for Moisture Determination in Milk Powders,” Abstract of Adresses at the International Dairy Federation 64thAnnual meeting, 1980.
“AOAC Methods and Determination of Moisture,” The Reference, AOAC International, vol. 17, No. 1, Jan. 1993.
Loo Dennis
Pennie & Edmonds LLP
Williams Hezron
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