Chemistry: natural resins or derivatives; peptides or proteins; – Proteins – i.e. – more than 100 amino acid residues – Scleroproteins – e.g. – fibroin – elastin – silk – etc.
Reexamination Certificate
1999-07-21
2001-08-07
Russel, Jeffrey E. (Department: 1653)
Chemistry: natural resins or derivatives; peptides or proteins;
Proteins, i.e., more than 100 amino acid residues
Scleroproteins, e.g., fibroin, elastin, silk, etc.
Reexamination Certificate
active
06271350
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a collagen obtained from fishes and a method of producing such fish collagen. In particular, the present invention is directed to a collagen obtainable from the skin of fishes and a method of extracting and producing the same.
2. Description of Prior Art
A great amount of waste portions of fishes, which are generally considered useless or untapped, had been discarded. This has been one of the major problems that we should address in the modem society to find various ways to use that seemingly unserviceable portion of fishes in many applicable fields. One of the typical waste examples is a skin of fishes, particularly the skins of salmons and trouts.
The salmon and trout skins contain collagen as a principal ingredient. Until recently, such collagen has been deemed a useless portion of fishes and no one had ever contemplated upon adapting the fish skin collagen for various uses and applications. In the past, nearly ten thousand salmon and trout skins had been wasted and discarded in vain.
In view of collagen being obtained from mammals and widely available as an edible material, researches are now being made about fish collagen and in particular about salmon and trout skins, in which a collagen is a main ingredient of the tissues. Recent years, thus, have seen some methods proposed to extract and produce a collagen from fish skins, including the skins of salmon and trout in question.
The fish skin collagen, however, differs in characteristics from mammalian collagen and requires relatively troublesome extraction steps involving deodorization, decolorization and degreasing of the skin. Also, the extracted collagen may hardly be refined to a satisfied degree. Those points of concern have yet to be solved in assuring that the collagen is edible.
Hitherto extracting and producing of fish skin collagen entails use of an organic solvent, such as ethanol, to remove non-collagen substances or portions, i.e. other substances and portions than the collagen, including proteins, fats and oils, from the fish skin. More or less, the process leaves some substances, particularly fats and oils, in the fish skin until the collagen is extracted. Ethanol is used to remove the residual fats or non-collagen substances or portions from the skin. Namely, the fish skin is placed in the ethanol solution and washed by stirring therein for that removal purpose.
However, this sort of conventional method is found defective in that, after the removal of non-collagen substances or portions by ethanol, much care is required not only to insure washing off the ethanol from the skin in water to avoid its chemical influence on the skin, but also to treat the waste water thereafter so as to allow a cleaned waste water to be drained out. Further, defective is this method in requiring a quite expensive distillation system to recover the ethanol used in that fat and non-collagen substance removal process. As a result, the production of fish skin collagen has been considered extremely high in costs.
SUMMARY OF THE INVENTION
With the above-stated drawbacks in view, it is therefore a primary purpose of the present invention to provide a simplified and economical method of extracting and producing a collagen from fish skin and also to provide a highly refined fish collagen obtained thereby.
To achieve that purpose, in accordance with the present invention, there are basically provided the following steps:
step of providing a raw skin of the fish;
salt admixing step of admixing a salt with said raw fish skin and then leaving the raw fish skin mixed with the salt in a cold condition for degreasing and deodorization thereof;
salt removal step of removing the salt from the raw fish skin that has undergone the salt admixing step, together with non-collagen substances or portions, so that a desalted portion of the raw fish skin is collected;
collagen extraction step of extracting a collagen portion from that desalted portion of raw fish skin; and
filtration step of filtrating said collagen portion so as to remove residual non-collagen substances, including fats, oils, odor and colors, therefrom, thereby obtaining a refined collagen.
Accordingly, non-collagen substances and portions are effectively and easily removed from the fish skin, using an inexpensive salt, to collect a collagen portion, and further, the collagen portion is filtered into a highly purified collagen (fluid) suited for food product elements and for various industrial uses, including medical and cosmetic materials and emulsifier for photographic films.
The salt usable in the present invention includes NaCl, KCl, Na
2
SO
4
and the like.
In one aspect of the present invention, after having washed the raw fish skin, the salt admixing step includes admixing the salt with the raw fish skin in an amount equal to that of the latter and then leaving the raw fish skin thus mixed with the salt in a cold condition below a room temperature. Or, the salt may be admixed with the raw fish skin an amount 0.2 to 3 times that of the latter.
Preferably, the salt removal step may include the step of applying a filtration means to the raw fish skin mixed with the salt and washing the same in water stream to remove the salt therefrom together with the non-collagen substances or portions via the filtration means, whereby the desalted portion of the raw fish skin is collected in the filtration means.
Preferably, the collagen extraction step may include immersing and incubating the raw fish skin in hot distilled water of 70 to 90° C. to thereby extract the collagen portion therefrom.
In another aspect of the invention, as the collagen portion extracted at the collagen extraction step is an impure collagen solution which still contains impurities, the filtration step may include providing 1 W/V % of activated carbon with respect to an amount of the impure collagen solution, adding such 1W/V % of activated carbon to the solution, then stirring both of those activated carbon and impure collagen solution for a predetermined period of time, and after lapse of a predetermined period of time, subjecting a fluid mixture of the activated carbon and impure collagen solution to suction filtration using a pulp for filtration, cerite and kieselguhr for one hour, thereby filtering out impurities from the impure collagen solution to obtain a refined fluid collagen. A fish collagen thus obtained is a highly refined fluid collagen suited for food and industrial uses.
In yet another aspect of the invention, the above-described method further includes a drying step of drying and solidifying the refined collagen obtained at the filtration step, so as to provide a solidified collagen. The solidified collagen may be broken into fine powders. The collagen powders are also suited for food and industrial uses. At this step, preferably, hot air of 70° C. may be applied to the refined collagen for 12 hours so as to obtain at least one bar of solidified collagen.
All other specific features and advantages of the present invention will become apparent from reading of the descriptions below.
REFERENCES:
patent: 5420248 (1995-05-01), Devictor et al.
patent: 5698228 (1997-12-01), Takai et al.
patent: 5-155900 (1993-06-01), None
patent: 910246 (1997-01-01), None
Montero et al. Effect of pH and the Presence of NaCl . . . J. Sci. Food Agric. vol. 54, pp. 137-146, 1991.
Nagashima Koji
Shimizu Hideki
Shimizu Johsuke
Takamatsu Minori
Yamada Kunishige
Browdy and Neimark
Russel Jeffrey E.
Thara & Company Ltd.
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