Food or edible material: processes – compositions – and products – Inhibiting chemical or physical change of food by contact... – Treating liquid material
Reexamination Certificate
1999-12-01
2001-02-20
Paden, Carolyn (Department: 1761)
Food or edible material: processes, compositions, and products
Inhibiting chemical or physical change of food by contact...
Treating liquid material
C426S417000, C426S478000, C426S489000, C426S643000, C554S008000
Reexamination Certificate
active
06190715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved process for producing edible quality fish oil. More specifically, the present invention relates to an improved process for producing menhaden fish oil wherein the produced fish oil is edible, retains a high percentage of omega-3 long chain fatty acids, has improved storage stability, and has minimal oxidation.
2. Description of the Related Technology
Certain fish and other marine animals contain oil rich in polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acids (DHA). These fatty acids are referred to as omega-3 fatty acids. The positive health effects of consuming fish oil containing omega-3 fatty acids have been widely reported in recent years (U.S. Pat. No. 5,006,281, issued Apr. 9, 1991 to Rubin et al., U.S. Pat. No. 4,913,921 issued Apr. 3, 1990 to Schroeder et al., and U.S. Pat. No. 4,874,629 issued Oct. 17, 1989 to Chang et al.—incorporated by reference herein). These positive health benefits have been seen in humans and in animals. Unfortunately, untreated fish oils and more specifically fish oils high in omega-3 fatty acid content inherently have an unsavory fish odor and flavor. Furthermore, untreated fish oils high in omega-3 fatty acid are susceptible to oxidation. These fish oils after being oxidized will degrade after a period of hours, and diminish the omega-3 content of the fish oil. However, fish oils high in omega-3 fatty acids can be processed to remove the inherently unsavory fish odor and flavor, and to improve their stability and enhance their storage capability.
Unsavory odors and flavors in fish oils can be initiated by lipid peroxidation catalyzed by enzymatic activity, such as lipoxygenase, peroxidase, and cyclooxygenase. In order to produce an edible fish oil it is important to remove these enzymes and thus remove the unsavory fishy odor and taste from the fish oil.
Fish oil instability and degradation is caused by oxidation and peroxidation of the fatty acids in the fish oil. This is especially true of the omega-3 fatty acids found in oil from menhaden, salmon, sardine, anchovy, and cod. Further oxidation of the fish oil can occur by exposing the fish oil to oxygen, heat, or light.
Numerous processes have been proposed in the past to stabilize fish oils high in omega-3 fatty acids. Some processes involve deodorizing the fish oil by removing the naturally occurring amines present in the fish oil (volatiles) that emanate the “fishy” odor. Deodorizing typically involves steam stripping the fish oil with high temperature steam in a vessel or container to remove the volatiles. This method alone has proven unsuitable since high temperature (above 470° F.) removes or damages the omega-3 fatty acids. As noted above loss of the omega-3 fatty acids eliminates a large portion of the health benefit of the fish oil. Other methods suggested to protect the fish oil against oxidation involve adding anti-oxidants to the oil to protect the oil from subsequent oxidation. Simply adding anti-oxidants to the fish oil has failed to produce an edible fish oil suitable for long term storage since naturally occurring compounds in the fish oil, such as aldehydes, ketones, and carotenoids can seed peroxidation and must be removed to provide antioxidant effectiveness. Each of the aforementioned processes, while having some valuable effect, does little to the inherent oxidative nature of fish oil, and therefore little to improve the long term storage stability of the produced fish oil.
It is therefore desired to develop an improved process for refining an edible fish oil for long term storage such that the oxidative nature of the produced fish oil is reduced, the fish oil is protected against further oxidation, and other impurities in the fish oil are removed. It is imperative that only a small percentage of the omega-3 fatty acids be lost in the refining process. Moreover, the process for refining fish oil should be capable of plant production scale in addition to bench and pilot plant scales, to ensure maximum commercial application.
SUMMARY OF THE INVENTION
The present invention solves a number of the problems inherent in the prior art by providing a method for refining fish oil from cooked, pressed fish comprising first extracting press liquor from said cooked fish. The press liquor consists essentially of fish oil and water that is inherent in the cooked fish flesh. The pH of the press liquor is adjusted and the press liquor is separated into a fish oil component and a water component. The fish oil component consists of a homogenous mixture of stearine and olein. The pH of the press liquor is lowered so that the water component has a pH of less than 2. The low pH of the press liquor deactivates enzymes in the oil that accelerate the production of unsavory taste and smell.
After the enzymes are deactivated the fish oil is chilled, without any agitation, to crystallize the stearine. Once the stearine is crystallized it can be separated from the olein. Most of the fatty acids are removed from the cold filtered fish oil (olein) by injecting an aqueous alkali solution. The aqueous alkali solution converts the fatty acids into water soluble soaps, which can be separated from the cold filtered fish oil. Additional water, at a temperature greater than the cold filtered fish oil temperature, is injected into the cold filtered fish oil. The water is gently mixed with the cold filtered fish oil and any residual soaps that reside in the cold filtered fish oil are dissolved into the water. The water is then extracted from the cold filtered fish oil.
The cold filtered fish oil is bleached after the soaps and fatty acids are removed from the cold filtered fish oil. Bleaching occurs inside of a vacuum vessel where the cold filtered fish oil is heated and amorphous silica is mixed with the cold filtered fish oil. Then diatomaceous earth is mixed with the cold filtered fish oil to remove unwanted compounds that interfere with anti-oxidant addition. The cold filtered fish oil is then heated further and vacuum conditions are ceased by introducing an inert gas into the head space of the vacuum vessel. The cold filtered fish oil is then cooled and filtered to produce a bleached fish oil.
The bleached fish oil is then deodorized under vacuum. Deodorizing is accomplished by heating the bleached fish oil and slowly injecting steam into the bleached fish oil. The bleached fish oil is heated further and a steam sparge is applied to the bleached fish oil; at the optimum temperature oil quality is assessed (this includes checking for residual impurities). Once it is determined that residual impurities are no longer present; the bleached fish oil is cooled and a chelating agent is added to the bleached fish oil. The bleached fish oil is further cooled and a mixture of anti-oxidants is added to the oil to produce a deodorized fish oil. The deodorized fish oil is then nitrogen blanketed and packaged for shipment.
Other and further features and advantages will be apparent from the following description of presently preferred embodiments of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings.
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Blackwell Delois Demery
Booth Bruce Howard
Crowther Jane Bruce
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