Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Treatment of untanned skins or hides
Reexamination Certificate
1998-09-23
2002-09-17
Green, Anthony J. (Department: 1755)
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Treatment of untanned skins or hides
C008S094150, C252S008570, C422S028000, C422S032000, C427S389000, C510S275000, C510S382000, C510S383000
Reexamination Certificate
active
06451062
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of curing hides from a meat-packing plant prior to their shipment to another facility for tanning into leather. In particular, it relates to improved additives for use in hide-curing raceways employed at meat-packing plants and other hide-curing facilities. Hide processing plants cure fresh hides or re-cure previously cured hides. As used herein, “operator” refers to a meat-packer, hide processor or operator of a similar hide-curing facility.
The profitability of a meat-packing plant is greatly affected by the money that the operator receives from various by-products of the meat-packing operation. Typically, the most profitable by-product is from the sale of hides for the production of leather. Because the tanning operation in which the hide is turned into leather is usually conducted at another facility, it is essential for the operator to preserve the value of the hide by curing the hide before shipment to the tanner. The hide must be as clean and free of bacteria as possible in order to avoid decomposition of the hide in the period between removal from the carcass and the tanning operation. That period may be as short as a few days or as long as a year or more.
Decomposition of a hide occurs through the action of bacteria and enzymes, both of these processes being accelerated by heat and moisture. As used herein, references to the deleterious action of bacteria on hides generally refers to the action of both bacteria and enzymes. On a hot summer day, decomposition can begin within four hours of slaughtering and hide removal. Since uncured hides typically contain approximately two-thirds water by weight, the operator should insure that the cured hides are as saturated with salt as possible. This minimizes possible deterioration and reduces the chances of claims by the tanner for insufficient cure.
Perhaps the most significant goal of hide-curing at the meat-packing plant is to reduce the damage that bacteria and other microorganisms can cause to the hide tissue between the time that the hide is flayed from the carcass and the time that it is tanned into leather. Typically the green hide contains contaminants that were present on the animal when it entered the hide processing facility including fresh and decomposed manure and organic matter, such as blood, that are released from the animal during the initial stages of the slaughtering process. All of these organic materials are ideal nutrients for destructive bacteria. If the growth of bacteria is not halted by the curing process, the hide can decompose into a useless, glue-like mass prior to tanning.
The problem of inhibiting microbial growth involves a number of considerations. Obviously, the existing microbial contaminants should be killed or their growth inhibited chemically. In addition, however, it is extremely important to physically remove from the hide the organic material which is an ideal food source for microbes. As mentioned previously, the organic material includes manure, blood and other organic contaminants released in the slaughtering process as well as a not insignificant amount of fat attached to the hide itself. If both considerations are not addressed, any microbes that survive the treatment can propagate in the remaining organic material before tanning is commenced.
The problem of hide-curing has been known for many years. One of the earliest forms of hide-curing was simply to dry the hide in the sun or by artificial means and to physically clean the surface. Although this method was somewhat successful in preventing decomposition of the hide, it was very difficult to re-wet the hide to produce useable leather.
At the present time, meat-packing plants in the United States typically treat green hides in a series of processing steps. These processes are generally described, for example, in U.S. Pat. No. 5,435,808, which is assigned to the assignee of the present invention and is incorporated by reference herein. As described therein, a typical plant may initially treat the hide by cooling it and removing flesh. The preliminary procedures may vary from plant to plant. However, treatment of the hide with a brine is an essential step common to hide-curing processes at meat-packing plants in the United States.
The brine curing is typically conducted in a “raceway.” Regardless of whether the hide has been fleshed or not, the hide sent to the raceway still contains a layer of fat and organic material, as well as bacteria. The purpose of the hide-curing raceway is to physically remove the remaining fat and organic material and to chemically kill or inhibit the growth of bacteria so that the cured hide will not decompose.
A typical hide raceway is an oval shaped structure filled with brine. These structures are large, containing tens of thousands of gallons of brine and hundreds of hides. Paddle wheels placed on each side of the raceway circulate the hides in the brine to maximize contact between the hides and the brine and the removal of contaminants. The brine is a saturated aqueous solution of salt, usually sodium chloride. Treatment is normally affected for 12 to 72 hours, although the most typical time is about 16 hours.
The brine is an excellent inhibitor of bacterial growth, but does not necessarily kill the bacteria. During the curing it is important to have the hide absorb as much salt as possible to inhibit the future growth of bacteria during storage and shipment. Typically, the hide processor monitors the amount of salt absorbed by the hides by measuring the diminution of the salt remaining in the brine with a salometer. When the salt is absorbed, it replaces a significant portion of the water in the hides and saturates the remainder. As much as two gallons of water are released from each hide. Excess brine is permitted to overflow. The operator of the curing raceway must monitor the salinity of the brine carefully to ensure that the brine remains saturated. If the brine does not remain saturated, the hides will not be saturated with salt and may decompose later.
Because of the foregoing qualities and the fact that it is relatively inexpensive, sodium chloride is the primary hide-curing agent. Potassium chloride can also be used and, indeed, has certain advantages over sodium chloride. However, potassium chloride is not used extensively because of its price. Other hide preservatives and cure accelerators are sometimes added to the brine, but the principal agent is salt. As used herein, “salt” refers to potassium chloride, sodium chloride or mixtures thereof.
The cured hides are removed from the brine and are then treated in a wringer or by other means to reduce moisture for the reasons previously noted. A typical hide will contain approximately 48% water by weight at this stage of processing. The hides are then graded, bundled and palletized for shipment. Sometimes they are salted on the flesh side to prevent decomposition before being bundled and palletized. Although brine curing has been utilized since the 1950's, the process does have certain deficiencies. Among other things, the chemicals used in hide-curing are not environmentally friendly. Increasing environmental concerns significantly limit the disposal of the salt-containing brine. In addition, many of the materials that are added to the hide raceway to improve curing present similar considerations. Some of these materials are expensive, disposal is restricted because of their toxicity, and they are not biodegradable.
Efforts have been made to clean and recycle the brine to minimize the quantity of material to be disposed. Typically, this is done by filtering out some of the solids and then concentrating the remainder by forcing off the excess water in a dehydrator. Unfortunately, organic matter that is recycled back into the raceways acts as food for bacteria. Generally speaking, organic levels in brine exceeding 1% by weight can create high bacteria counts. The halophilic organisms that create the discolorations on the flesh side of the hide during storage
Holzhauer Frederick W.
Johnson Dana J.
McAninch Terry L.
Birko Corporation
Green Anthony J.
Merchant & Gould
Young Thomas H.
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