NZ264689A - Method of freezing shellfish comprising applying sugar or a polyhydroxyl alcohol prior to freezing - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £64689 Patents Form No, 5 OurRef: AS203635 NEW ZEALAND PATENTS ACT 1 953 Complete After Provisional No. 264689 Filed: 14 October 1994 COMPLETE SPECIFICATION A SHELLFISH FREEZING METHOD We, WESTHAVEN SHELLFISH LIMITED, a New Zealand company of No 1, R.D., Collingwood, Golden Bay, Nelson, New Zealand hereby declare the invention, for which We pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: 2 The present invention relates to a method of freezing and cold storage of shellfish and the product thereof.

More particularly, but not exclusively, the invention relates to a method of mitigating the effects of ice formation during the freezing of shellfish.

The present invention relates to a method which reduces the susceptibility of shellfish shells to fracturing and cracking during freezing and subsequent frozen storage.

It is well known in the art to freeze various food substances prior to packaging, shipping or storage. There are many techniques known in the frozen food industry involving freezing and preservation of such products as vegetables and meats. Such techniques have been implemented to overcome the effects of freezing any water or moisture as may be present on or in the product. These effects may be clumping of individual vegetable or meat products, deterioration in quality and appearance of the product and the increased energy requirements necessary to freeze excess water on or in vegetables.

Many of the techniques, such as those described in New Zealand patent • No. 230,946, are directed towards reducing the water content of the product which is to be frozen. This patent is concerned with the technique whereby vegetable products can be stored at temperatures below 0° C in a "non breakable" and flexible form.

Techniques such as those described in NZ 230,946 are generally concerned with preserving the texture, taste and appearance of vegetables or vegetable products. Similar techniques involve freeze drying and treatment of vegetables with salt solutions. 3 2 6 r The freezing and cold storage of shellfish meat products present similar problems to those discussed above.

However, freezing of whole shellfish including the shells poses further difficulties. One of these difficulties is the cracking of the shell upon freezing.

In the sale and presentation of shellfish and shellfish products it is important that the shells remain intact for the following reasons: shellfish are often served still attached, or at least contained within, their original shells. The quality and appearance of the shellfish as a whole is therefore extremely important to the marketing of the product. Also, on processing and packaging the shellfish prior to preparation and eating, it is desirable that the shells remain intact. This contains the flesh in the interior of the shellfish so that the molluscs may be boiled, steamed or otherwise cooked whole.

Accordingly, it is important that the shellfish be frozen and stored in good condition otherwise a significant reduction in the value of the shellfish in the marketplace is incurred.

It is known that the surface of a shellfish shell contains many fine - interstitial cracks, crevices and cavities, which will generally contain residual water.

During harvesting the shellfish are collected and washed thereby allowing fresh water to permeate into such crevices and cracks. In the subsequent freezing, expansion or freezing of the residual water and the structure and number of ice crystals, is such that the shells often fracture at low temperatures. This reduces the value of the shellfish. '26 4 '6 89' It is an object of the present invention to provide a method and product which obviates the above mentioned disadvantages inherent in the freezing and cold storage of shellfish or to at least provide the public with a useful choice.

The present invention further provides for a method of treating shellfish comprising: applying, as an active ingredient, to the shellfish following drying, a substance selected so as to function to substantially prevent water from reentering interstitial cracks and cavities in the shellfish shell and substantially prevent of said water freezing.

Preferably the active ingredient is a sugar and/or a polyhydroxyl alcohol, optionally with a starch, to the shellfish and freezing the shellfish. intellectual property o of n.z.

SEP 1998 264689 The process may, prior to freezing, further include the steps of: harvesting the shellfish from the sea; and washing and draining the shellfish.

Starch may also be applied to the shellfish The process may further include thoroughly drying the shellfish by applying heated, unheated or dehydrated air.

The process may further include chilling the shellfish temporarily during washing and draining.

The washing and draining of the shellfish may be repeated as often as is required.

The process may further include the steps of; vacuum packing the treated shellfish; pasteurising said vacuum packed shellfish by placing them in hot water at approximately 80-100°C for six to eight minutes; cooling said vacuum packed shellfish; and freezing the vacuum packed shellfish to about -25°C as rapidly as possible.

The abovementioned process may include freezing the shellfish to about -25°C or less.

The process of freezing the shellfish may include the further steps of maintaining the shellfish in cold storage at about -25°C or below. ~ , fNTELLECTUAL PROPERTY OPTO OF N.Z. | 1 o Si':P 1998 i received - 5a - During vacuum packing the shellfish may be placed onto a polystyrene tray. intellectual property of n.z.

SEP 1998 RECEIVED The abovementioned product and process may be applied to bivalve shellfish such as cockles, mussels, pippies or similar molluscs.

Preferably the initial drying step is preceded by washing and/or grading.

Preferably prior to the freezing step the shellfish are vacuum packed and/ or cooked or pasteurised.

The abovementioned processes and products may be applied to univalve shellfish such as other clam species and similar molluscs.

A particular embodiment of the invention will now be described, by way of example only.

The shellfish are typically harvested from the sea, washed in fresh water, dried and washed again. The shellfish are dried by way of blowing unheated air over them. Alternatively the air may be heated or dehydrated. This process may occur over several cycles depending on the type of shellfish and the area in which I 0 SEP 1998 26 4 it was harvested. It is to be understood that the washing and drying process is not limited to a single cycle.

The shellfish are thoroughly dried, following which a coating of the present invention is applied.

The coating may be either a solution containing from about 5% by weight to saturation of sucrose in water, a solution containing 2% to 10% glycerol solution (in either water or ethanol) or a mixture of sucrose and glycerol where the proportion of glycerol is approximately 2% by volume and the sucrose from 5% to 40% by weight. The coating may further comprise the additional ingredient of wheat starch or similar starch product.

The above solutions are applied by either dipping or spraying the shellfish so that the shellfish are wet with the solution over the entire exterior shell surface. Excess coating material is allowed to drain from the shell and the shellfish left to dry. Drying is achieved by means of blowing air over the shellfish.

As soon as the drying is complete, the shellfish are transferred to a polystyrene tray which is placed into a plastic vacuum bag which is vacuum sealed.

The packaged shellfish product may then be placed in hot water at approximately 80-100°C for about six to eight minutes thereby providing for the partial sterilisation of the product. This process reduces the number of bacteria present in the shellfish. 26 4689 8 The vacuum packed, pasteurised shellfish are then cooled in cold water for several minutes. The vacuum packed pasteurised shellfish may also be cooled in air if desired.

The packaged shellfish are then blast frozen to -25°C as quickly as possible. Once frozen, the product is packed ready for the market and placed in cold storage at -25°C.

Without being bound by any theory it is understood that the coating materials described above acts as an agent which reduces the amount of water in the interstitial cavities and cracks in the shellfish shell, and modifies the structure of any ice crystals forming in such naturally occurring cracks thereby reducing the susceptibility of the shell of the shellfish to cracking upon freezing and cold storage.

The abovementioned process and coating composition has been applied to cockles, however, it is envisaged that similar techniques may be applied to other shellfish. intellectual property office of n.z. 1 0 SEP 1998 RECEIVED 9 It is to be understood that the scope of the invention is not limited to the described embodiment and therefore that numerous variations and modifications may be made to the embodiment without departing from the scope of the appended claims.

Claims (11)

WHAT WE CLAIM IS:

1. A method of treating shellfish comprising: applying, as an active ingredient to the shellfish following drying, a substance selected so as to function to substantially prevent water from reentering interstitial cracks and cavities in the shellfish shell and substantially prevent freezing of said water; and freezing the shellfish.

2. A method of treating shellfish as claimed in claim 1 wherein the active ingredient is a sugar and/or a polyhydroxyl alcohol.

3. A method of treating shellfish as claimed in claim 1 wherein starch is also applied to the shellfish.

4. A method as claimed in claim 1 further including thoroughly drying the shellfish by means of applying air to the shellfish.

5. A method as claimed in either claim 3 or 4 further including chilling the shellfish temporarily prior to the method being carried out.

6. A method as claimed in any one of claims 3 to 5 further including the steps of; vacuum packing the treated shellfish; pasteurising said vacuum packed shellfish by placing them in hot water at approximately 80-100°C for six to eight minutes; Intellectual" property ' q ffIce of n.z. 10 SEP 1998 -11- cooling said vacuum packed shellfish; and freezing the vacuum packed shellfish to about -25°C as rapidly as possible.

7. A method as claimed in any one of claims 1 to 5 wherein the shellfish are frozen to about -25°C or less.

8. A method as claimed in any one of claims 1 to 6 further including the step of maintaining the shellfish in cold storage at about -25°C or below.

9. A method as claimed in claim 1 wherein the initial drying is preceded by washing and/or grading.

10. A method as claimed in claim 1 wherein prior to the freezing step, the shellfish are vacuum packed and/or cooked and/or pasteurised.

11. A method of treating shellfish substantially as described in any one of claims 1 to 10. intellectual property office of n.z. 10 SEP 1998 RECEIVED 164 - 12 - 1 2. Shellfish treated in accordance with the process of any one of claims 1 to 10. WESTHAVEN SHELLFISH COMPANY LIMITED BALDWIN SHELSTON WATERS ASPEC03196 OFFICE ,Wai£wwTpjo®v 0FW.Z J 0 Sr? 1393