Title: Edible food casing printed with water-resistant ink

Description: The invention relates to edible food casings, especially for sausages, which are printed with edible printing ink, a process for the manufacture of such casings, and to a printing ink for use in printing the food casings.

For convenience, the following description refers only to sausage casings, because it is to sausage casings that the invention is especially directed, but it will be understood that such edible casings may also be used for other foods.

Edible sausage casings have been known for a long time. For this purpose, either natural guts or artificial guts of natural material are used. As is known, edible casings comprising artificial guts can be manufactured from an animal skin fibre composition (collagen) either by the wet extrusion process or the dry extrusion process. In the wet extrusion process, a solution of collagen is extruded through an annular die into a coagulation bath. In the dry extrusion process, a pasty collagen mass is extruded directly to give a collagen tube. The resulting tube is subjected, both in the case of the wet extrusion process and in the case of the dry extrusion process, to a drying treatment, and, in order to improve the water resistance, to a hardening treatment or tanning.

The present invention is directed to a solution of the following problem:

In many countries the law stipulates the marking of sausages, which are packaged on a large scale in natural guts or in edible artificial guts made of collagen, with some form of inspection stamp. Packaged sausages carry this inspection stamp on the packaging and non-packaged sausages must be provided with a bill band carrying the inspection stamp. This way of marking is very labour-intensive and therefore expensive. It is the principal object of the present invention to overcome these disadvantages by providing a marking of the goods which is easy to apply and is durable. According to the invention, this object is achieved by applying to sausage casings made of edible material a water-resistant durable print in an edible ink.

Accordingly, the present invention provides sausage casings of edible material which are printed with a water-resistant edible printing ink.

The invention also provides a process for the manufacture of such printed sausage casings.

Finally, the invention provides an edible printing ink for use in printing the sausage casings.

According to the invention, the water-resistant print on the sausage casing consists of a printing ink which comprises (a) at least one pigment dyestuff, (b) at least one liquid vehicle for the pigment dyestuff, (c) at least one substance which can be crosslinked thermally and/or by means of a tanning agent and, if appropriate, also comprises a tanning agent and added oils.

The pigment dyestuff may be any of the coloured pigments which are permitted under the Foodstuffs Laws, and preferably comprises a titanium dioxide pigment.

Liquids customary for the purpose, for example, water, may be used as the liquid vehicle in which the pigment dyestuff is dispersed or suspended. However, the printing ink preferably contains liquids of low volatility since as a result of the absence of volatile liquids, such as water, thickening of the ink in the inking unit is avoided or substantially reduced. Liquids of low volatility which at the same time exert a plasticising action on the collagen tube are especially preferred for use. Known plasticisers which may be used are the plasticiser alcohols such as, for example, ethylene glycol, glycerine and sorbitol.

The presence in the printing ink of at least one substance which can be cross-linked thermally, optionally in conjunction with a tanning agent, or alternatively by such an agent alone, is very important for the production of a water-resistant print. Examples of such substances include proteins and cellulosic materials. Suitable proteins include gelatine, albumen, casein and also collagen itself. In addition to cellulose, which can also be employed in the form of its derivatives, such as methylcellulose, ethylcellulose and the like, other vegetable "builders", such as pectins or products closely related to the pectins, such as gum arabic, as well as alginates, are also suitable.

The presence of a cross-linkable substance, such as a protein or cellulose, is essential in order to achieve a water-resistant ink application. This is because the particular coloured pigment, for example, titanium dioxide, when embedded in protein, cellulose or some other cross-linkable substance, gives a sufficiently water-resistant application of ink after cross-linking which is achieved by means of a tanning agent or by drying by warming, optionally in conjunction with a tanning agent. In other words, the cross-linking fixes the coloured pigment.

Suitable tanning agents which may be used to bring about the cross-linking of the cross-linkable constituent or constituents of the printing ink and at the same time the hardening or tanning of the collagen tube include, for example, glyoxal, glutaraldehyde, formaldehyde, aluminium sulphate, iron sulphate, and the like.

Small proportions of oil in the ink improve the flexibility and hence the printing properties. Unsaturated vegetable oils, such as linseed oil or castor oil, are preferably used for this purpose.

The printing of the sausage casings is carried out immediately after drying the extruded collagen tube, which is as a rule effected in a long drying tunnel. The printing is carried out in a manner which is in itself known. During printing, the liquids contained in the ink, such as, for example, glycerine, sorbitol or other plasticisers, migrate into the collagen of the tube. After the ink has been applied (in the form, for example, of a stamp, a letter or script) the tube is rendered water-resistant, by means of a heat treatment and/or tanning treatment, thereby cross-linking the cross-linkable substances present in the printing ink. A heat treatment of, for example, 6 hours at 90.degree.C will generally suffice.

The printed tube can then be subjected to further treatments, for example, plasticising and/or tanning treatment, and can also be gathered up to form a shirred tube before packaging.

The composition of the pasty printing ink is in itself not critical and can vary within relatively wide ranges. Examples of suitable compositions are as follows, all percentages being by weight.

    ______________________________________
    (a)  Pigment dyestuff
                      10 to 60%, preferably 25 to 50%,
    (b)  liquid vehicle
                      30 to 80%, preferably 50 to 60%,
    (c)  cross-linkable
                       2 to 30%, preferably 10 to 25%.
         substance
    ______________________________________

If a tanning agent and/or added oils are included in the printing ink, the amounts of these additional components advantageously lie within the following ranges, each percentage being by weight: Tanning agent 0.01 to 0.5%, preferably 0.1 to 0.4%, oil 5 to 25%, preferably 10 to 20%.

In the accompanying drawings, FIG. 1 shows, by way of example, a flat casing that has been printed in accordance with the invention; and

FIG. 2 shows a sausage in the printed casing.

The table which follows contains a tabular summary of examples of formulations of inks, suitable for consumption, for printing edible small guts of hardened albumen.

                                      Table
    __________________________________________________________________________
    (quantities quoted = parts by weight)
                 Basic
                      A   B  C  D  E   F  G  H  I  J   K  L  M  N
                 formul-
                 ation
    __________________________________________________________________________
    Water             500
    Glycerine    300  100 500
                             500
                                300
                                   300 300
                                          300
                                             300
                                                300
                                                   500 150
                                                          200
                                                             200
                                                                300
    Titanium dioxide
                 200  100 100
                             200
                                100
                                   200 300
                                          200
                                             200
                                                200
                                                   200 200
                                                          200
                                                             200
                                                                200
    Glyoxal (40% strength)
    aqueous solution)
                 1        3  2  2  4   4           5   2  4  4  4
    Al sulphate. 18 H.sub.2 O             1  1  1
    Methylcellulose   30  30 30           30 60 80
    Gelatine          20  20 20        10              30
    Ethylene glycol   10  10 10           10 20 30
    Linseed oil                                              100
    Castor oil                                            100
    Gum arabic                  100
                                   200    30 30 40 20
    Albumen                            30 30 30 40 20
    Alginate (tradename                            50
    "Cohasal")
    Guaran                                                      100
    Casein       50                                       50 50
    Collagen                                           500
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