DESCRIPTION

The invention consists in the means of obtaining a gelatin with a broad spectrum of characteristics, that is industrially competitive, odourless and translucent, and the procedure whereby this is achieved. The basis is denatured collagen to which some or all of the following ingredients can be added: water, salts (e.g., sulphates, phosphates and chlorides), hydrocolloids (e.g., hydroxymethylcellulose, carrageenans, guar), covalent bonding inducers (e.g., transglutaminase, cystein), sugars and alcohols. Whether all or only some of these ingredients are involved depends on the conditions and characteristics of the base product and on the chemical and physical treatment to which this is then subjected. It also depends on what characteristics are required of the product in which the gelatin is finally used.

The product is obtained by putting the skin and/or connective tissue through a series of washes, followed by a diluted alkali treatment to complete cleaning and prepare for solubilization. The duration and intensity of the process depends on the state of the raw material.

Next, after a neutralizing wash it is treated with diluted acid. Proper selection of the acid(s) makes it possible to obtain the right properties in the final product, and its concentration and the duration of the treatment depend on the state of the raw material, the degree of cross-linking of the collagen, etc. After pre-gelatinization the protein is thoroughly washed and the gelatin is extracted in a water bath. The characteristics and the yield depend on the extraction temperature and time. The product is filtered and ultrafiltered then dried (e.g., air-drying, atomization or freeze-drying). Finally, the protein is mixed with the requisite ingredients to produce gelatins; moreover, it is possible to control the degree of thermal irreversibility.

Long-term stabilization and storage of raw material (connective tissue):

Sources of skin and residual connective tissue are manifold, depending on the marine species and the processes to which it has been subjected before skinning. Stabilization and conservation are achieved by one or more of the following physicochemical processes. The first requirement is to add chemical compounds, especially common salt and alternatives to sodium chloride. It is also possible to stabilize by adding microbicides, protease inhibitors, covalent bonders and blanchers. Other possible additives are alcohols and sugars/polysaccharides, which also facilitate drying of the skin by reducing water activity; this means that they also have antimicrobial and antioxidant effects in that they halt chemical reactions to a greater or lesser extent depending on the residual water activity.

The material is then subjected to one or more of the following physical treatments, which have never been used before for the preservation of skin or residual connective tissue. These treatments include total or partial drying –air or vacuum drying, atomization or freeze-drying– pressing, heating, thermal sterilization/pasteurization, high pressure, smoking, irradiation, ultrasonication and freezing. The combined effects of these physicochemical processes prolong the shelf life of these waste products and make them easier to transport and store.

The dosages of the added chemicals or the intensity/duration of the physical treatments are not limiting factors and depend only on the number of simultaneous modifications that it is wished to effect. Whether all or only some of these physicochemical modifications are required will vary depending on the conditions and the characteristics of the raw material and the desired end product.

INNOVATIVE ASPECTS

The process extends the range of possible rheological properties for gels (melting temperature, gelling temperature, setting time, hardness, elasticity, cohesiveness, etc.) of the same species in the same climate, by altering their chemical composition. In this way, new characteristics can be introduced. For example, the degree of reversibility can be controlled so that the gelatin offers more possibilities of use in ready-made dishes or other products to be eaten hot.

As regards storage of skin, the little fish skin that is used to produce gelatin normally comes fresh, or at most frozen, with no prior treatment. The problem up till now was the rate of spoilage and the loss of functional quality, which severely limited the usability of this waste. The new process offers the possibility of physicochemical modification of skin and connective tissue from fish and other marine animals, which can thus be stabilized and stored for long periods while retaining a high level of functionality.

COMPETITIVE ADVANTAGES

Gelatin extracted by this method presents high rheological properties for a fish gelatin, and this means that it can be put to uses for which other marine gelatins are not suited. The possibility of prolonging the useful life of fish skins means that they can be more readily transported and industrial gelatin production can be better planned

KEYWORDS

007002001 Food additives/Ingredients 007003 Resources od the Sea, Fisheries

fish skins, collagen, gelatin extraction, preservation

PATENT

ES200001925, PCT/ES01/00275 & ES200101867, applied for at 2000-08-27

CONTACT

Estrella Maroto
email: e.maroto@orgc.csic.es
phone: +34 91 585 52 51

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