GB2116818A - A method of preparing a dry food product - Google Patents

Abstract

A readily rehydratable food product is prepared by mixing mainly undenatured mince of animal flesh, hard fat, starchy material, water and optionally usual additives, thereafter enclosing this mixture in a confining receptacle, subsequently freezing the confined mixture and finally effecting in any succession: thawing, dehydrating and subdividing. The dehydrated particles can be readily reconstituted in hot water. The dehydrating step may be effected at least partially using a smoking technique.

Description

SPECIFICATION A method of preparing a dry food product The present invention relates to a method of preparing a dry food product.

The invention provides a method of preparing a readily rehydratable dry food product, comprising mixing mainly undenatured mince of animal flesh, which is previously washed if necessary, with hard fat, starchy material, water and optionally usual additives, thereafter enclosing the mixture in a confining receptacle, subsequently freezing the mixture stiff while preventing the generation of any substantial compressive pressure and thereafter effecting in any succession: thawing, dehydrating and subdividing the mass.

The product obtained by this method is readily rehydratable, so it can be reconstituted in a relatively short time to a product ready for consumption.

Confining the mixture during freezing while preventing the build-up of a substantial pressure appears to promote the formation of a strong gel structure which survives subsequent treatments such as handling, thawing, dehydration and rehydration of the product.

The animal flesh will include at least a major proportion, typically at least about 70% by weight, of undenatured protein, obtained preferably from an animal source, such as comminuted fish, meat, or flesh derived from molluscs, crustacea or cephalopods. Minced fish flesh is particularly suitable. A blend of such materials derived from more than one of these sources can be used, but a mixture predominantly consisting of fish mince is preferred since the final reconstituted product then closely resembles natural fish.

The inclusion of minor amounts of starchy material together with the protein in the mixture is advantageous, as the texture and rehydration characteristics of the food product fragments are altered thereby. Dehydrated potato, for example in the form of potato powder or potato flake, is very suitable for this purpose, especially in food product fragments wherein the protein content is at least principally derived from fish and the reconstituted food product is intended to represent fragments of fish flesh. In this particular context, the presence of the potato ingredient can also help to maintain the colour of the reconstituted food product fragments.Preferably the finely divided starchy material comprises at least about 1%, most preferably at least about 3%, and ideally about 5%, by weight, while in general the finely divided starchy material will not comprise more than about 15% by weight of the mixture exclusive of the amount of added water. For obtaining a fish-like final product, preferably potato flake is used as a starchy material, while potato powder can also be used successfully, although it has to be used in greater amounts.

The total moisture content of the mixture immediately prior to freezing is also an important aspect of the invention. Preferably the moisture content is at least about 70%, and ideally at least about 80%, by weight. Preferably the moisture content does not exceed about 90%, and ideally not more tham 85%, by weight. In any event, the moisture content of the mixture must be such than an acceptable gel structure can be created when it is frozen in a confining receptacle.

The addition of water to the mixture may be necessary in order to obtain an appropriate total moisture content. Typically the optimum quantity of water to be added will be from about 5 to about 30% by weight of the moist mixture immediately prior to freezing, but this quantity will vary depending on the level of denaturation of the uncooked protein starting material on which the gelling capacity is dependent and on the nature and amounts of other ingredients blended with the uncooked protein.

A further minor ingredient that has a very beneficial effect on the texture of the reconstituted food product fragments is fat. This is particularly advantageous in a food product that in intended to simulate fragments of fish flesh. Hardened natural oils are very suitable in this context, but other edible fats can be used, provided they are solid at ambient temperature. If fish flakes are to be simulated, preferably white or slightly yellowish fat is used. Preferably, the total added fat content (that is, not taking into account any fat inherently present in the protein ingredient) of the mixture, exclusive of added water, immediately prior to freezing is at least about 5%, and ideally at least about 8%, by weight.

Preferably, the total added fat content at this stage does not exceed about 10%.

In order to maintain the organoleptic properties of the food product, it is very desirable that one or more antioxidants should be included in the mixture, especially where fat is also included as an added ingredient. Many protein ingredients contain some fat or oil in any event. Suitable foodgrade antioxidants are well known to the food technologist, and are specified in published lists of permitted food ingredients. In terms of the levels of such antioxidants appropriate for use in a food product of the invention, there is no necessity to deviate from what is standard practice in the art.

A further minor additive that can advantageously be included in the mixture is sodium chloride. In general, the level of sodium chloride will not be greater than about 2% by weight of the mixture, exclusive of added water.

Usual additives, such as permitted flavouring and colouring agents can also be included in the mixture in an amount up to 3% by weight of the mixture, exclusive of added water (this figure is not critical but is generally dependent on the character of the additives), in order to give the reconstituted food product fragments distinctive character and an appropriate appearance. For example, the inclusion of titaniurn dioxide is particularly beneficial in simulated fragments of fish flesh because it promotes an attractive white appearance in the reconstituted food product. So-called "liquid smoke" can be used to impart a smoked character.

Where it is desired that the food product should have a smoked character, it is also very beneficial to effect the dehydration of the mass at least partially by smoking, preferably using the traditional techniques that have been used for many years in the smoking of fish such as herring and haddock.

The preparation of the mixture from any desired suitable combination of the above ingredients can be effected simply by comminuting the various ingredients, using conventional food mixing equipment, for example a bowl chopper.

The preparation of the frozen block can be achieved by, for example, placing the mixture in trays of the type employed conventionally in the freezing of minced fish flesh into flat slabs prior to subdivision into fish sticks. The actual freezing can be accomplished using standard freezing equipment, for example a plate freezer or a blast freezer.

The manner of freezing the mixture is of interest for obtaining a strong gel structure, allowing subsequent handling of the frozen, thawed, dried and reconstituted product. During freezing, the mixture is to be confined in such a way that no free expansion can occur, but that generation of any substantial pressure is prevented.

The manner of subdivision of the frozen block into fragments will be dictated by the physical form desired in the reconstituted food product. In most situations it will be appropriate to divide the frozen block initially into smaller portions, such as logs, which can be handled more readily during the final subdivision into the desired fragments. Such initial subdivision of the block can be achieved, for example, by sawing. The final subdivision into fragments can be effected in several ways.

Dice, for example can be prepared by sawing or by pressing. Irregularly shaped fragments can be obtained, for example by crushing or by smashing. Flakes, such as simulated fish flakes, can be obtained by using a conventional slicing machine and in particularly by using multi-bladed rotary slicing machines of the type employed to slice vegetables such as carrots.

In most situations, and especially for the final subdivision, it will be sensible to temper the frozen block. An optimum freezing temperature is likely to be too low for efficient subdivision. For example, a typical plate freezer will operate at about - 30"C, but, for ideal subdivision by cutting or slicing, the block should be at a temperature higher than about - 10"C.

In general, the block needs to be tempered to a temperature of from - 8 to - 2'C.

Dehydration of the fragments can be effected using any one of a variety of conventional drying techniques. A very convenient technique is air-drying, using a current of heated air directed into fragments lying on a supporting means such as a tray or open mesh belt. It will be apparent to the skilled reader that the physical dimensions of the fragments wll be an important consideration in determining the extent to which the fragments can be dehydrated successfully and economically. In particular, the ratio of total surface area to the volume of the typical fragment should be relatively large. We have found that, for example, dice of up to about 1 0mm3 and simulated flakes of up to about 20 x 20 x 5 mm can be dehydrated satisfactorily using air drying.In general, the air temperature should be in the range of about 40"C to about 85"C. The dehydration should be conducted such that the dehydrated fragments have a moisture content not greater than about 5%, and preferably not greater tham about 3%, by weight. Although the fragments can be thawed, if desired, prior to dehydration, it is beneficial to commence the dehydration while the fragments are still frozen, as in this state the fragments are less likely to be damaged during handling and in any event this leads to a faster and more efficient process.

In some circumstances it can be beneficial to dehydrate the mass partially before it is subdivided into small fragments, dice or flakes which can then be dehydrated fully. According to a further preferred embodiment of the invention, the frozen mass is thawed, the partially dehydrated, thereafter subdivided and finally fully dried. If required, the mass may be divided into relatively large logs prior to, during or just after thawing, whereby the rate of the partial dehydration may be increased.

Suitably the partial dehydration is effected to an overall moisture content of from 50 to 70% by weight, as remarked before, the partial dehydration can be effected using a conventional smoking treatment.

Preferably following the partial dehydration, the mass should be chilled or lightly refrozen, generally to a temperature not lower than about - 1 0'C, prior to subdivision into the final fragments. Such chilling or refreezing can make it easier to subdivide the mass.

An advantage of partial dehydration of the mass is that the fragments have less tendency to adhere to one another during the further dehydration, and can therefore more readily be dried in multi-layers.

The dehydrated food product fragments of the invention.can be marketed as an individual food item for use as a meal ingredient according to the consumer's own choice, or the dehydrated food product fragments can be blended with other dry food materials in a composite reconstitutable convenience food product such as a soup mix, sauce mix or casserole mix.

The following Examples illustrate preferred embodiments of the invention in greater detail.

EXAMPLE 1 Blue whiting were headed, gutted, skinned and boned and the mince so obtained was washed using conventional equipment. The fish mince was used as the basis material for the method according to the invention by being mixed with additional ingredients as set out below: Ingredient % by weight Fish mince 70 White, hardened natural oil 8 Potato flake 7 Sodium chloride 1 Titanium dioxide 0.1 Antioxidant 0.001 Water to 100 The fish mince was placed in a bowl chopper together with the water and mixed for 3 minutes. The fat and antioxidant were then added, and mixing was continued for a further 1 minute.

The remaining ingredients were then added and mixing was continued for a final 1.5 minutes.

The resulting moist mixture was packed firmly into tray moulds of dimensions 2 cm X 40 cm x 57 cm, which were stacked, with freezing plates inserted between them, and frozen for 1 hour at - 30"C in a horizontal plate freezer. No discernible expansion, other than the filiing of minor voids in the mass, occurred during freezing.

The frozen blocks were divided into logs using a band saw. The logs were tempered to - 6"C and chopped into irregular flakes, approximately 20 X 20 X 4 mm, using a conventional multi-bladed rotary vegetable slicer.

The flakes were air-dried by being exposed to a current of air at 65"C and 30% RH flowing at 1 m/sec. After 5 hours, the flakes had reached constant weight and had a moisture content of 3% by weight.

The dehydrated flakes were fully reconstituted almost instantly when boiled in water, and had the appearance and character of whole cooked fish flesh. The flakes remained intact on prolonged boiling.

EXAMPLE 2 A similar moist minced fish mixture was prepared from the following ingredients, using the same techniques as in Example 1, and frozen into blocks as before.

Ingredient % by weight Minced fish (as in Ex. 1) 68 Hardened natural oil 8 Potato powder 1 > 0 Sodium chloride 1 Antioxidant 0.001 Yellow food colourant 0.1 Commercial "liquid smoke" 1.5 Water to 100 The frozen blocks were sawn into logs, tempered and chopped into flakes as in Example 1. The still frozen flakes were dehydrated, using the same drying conditions as in Example 1, and reached constant weight again at 3% moisture--after about 3 hours.

After reconstitution in boiling water, the flakes were judged to be an excellent simulation of whole flakes of cooked smoked fish flesh, both in terms of their physical appearance and their organoleptic characteristics when eaten.

EXAMPLE 3 Frozen whiting was thawed, headed gutted, skinned, boned and washed, using conventional equipment. Cooked crabs were cleaned and shelled. These ingredients were used for preparing a dry fish-like product having a distinct rabtaste.

Ingredient % by weight Fish mince 50 Crab mince 1 5 Hardened natural oil 8 Potato flake 4.5 Sodium chloride 1.5 Antioxidant 0.001 Titanium dioxide 0.3 Red food colourant 0.001 Water to 100 These ingredients were mixed, frozen and sawn to logs as in Example 1. The logs were partly dried by being exposed to a current of air at 80"C and 30% RH flowing at 1m/sec.

After 1.5 hours the logs had lost approximately 25% of their initial weight. The logs were diced and dried, using the drying conditions as in Example 1.

EXAMPLE 4 Fish mince as prepared according to Example 1 was used.

Ingredient % by weight Fish mince 70 Hardened natural oil 8 Potato flake 7 Sodium chloride 1 Yellow food colourant 0.1 Antioxidant 0.1 Water to 1 00 The ingredients were mixed and frozen as described in Example 1. The frozen blocks were divided into logs using a band saw.

The logs were smoked in a Torry kiln in a conventional woodsmoke atmosphere, produced by burning sawdust and wood shavings, at 80"C for 1.5 hours. On completion of the smoking step, the logs had lost approximately 25% of their initial weight. The smoked logs were transferred to a chill store at + 3"C and throughly chilled, and then sliced into irregular flakes, approximately 20 X 20 x 4 mm, using a conventional bacon slicer. The flakes were air-dried by being exposed to a current of air at 80"C and 30% RH flowing at 1m/sec. After 3 hours, the flakes had reached constant weight and had a moisture content of 3% by weight.

Boiling water poured onto the dehydrated flakes caused them to be fully reconstituted after standing for 3 minutes, and at that stage they had the appearance and character of whole cooked smoked fish flesh. The flakes also remained intact on prolonged boiling for 20 minutes.

Claims (11)

1. A method of preparing a readily rehydratable dry food product, comprising mixing mainly undenatured mince of animal flesh, which is previously washed if necessary, with hard fat, starchy material, water and optionally usual additives, thereafter enclosing the mixture in a confining receptacle, subsequently freezing the mixture stiff while preventing the generation of any substantial compressive pressure and thereafter effecting in any succession: thawing, dehydrating and subdividing the mass.

2. The method according to claim 1, wherein a mixture is prepared comprising 70-85% by wt of mince of animal flesh, 5-10% by wit of hard fat 1-15% by wt of starchy material 0-2 % by wt of salt 0-3 % by wt of usual additives sufficient water to bring the overall water content to between 70 and 90% by weight.

3. The method according to claim 1 or 2, wherein the starchy material is potato flake and/or potato powder.

4. The method according to claim 3, wherein the starchy material is entirely potato flake.

5. The method according to any of claims 1 to 4, wherein the mass is divided into flakes.

6. The method according to any of claims 1 to 5, wherein the mass is dehydrated in air having a temperature of 40 to 85"C.

7. The method according to claim 6, wherein the air comprises natural smoke.

8. The method according to any of claims 1 to 7, wherein the frozen mass is thawed, then partly dehydrated, thereafter subdivided and finally fully dried.

9. The method of claim 8, wherein the partial dehydration is effected to an overall moisture content of from 55 to 70% by weight.

10. The method according to any previous claim, wherein the mince is predominantly fish mince.

11. A method of preparing a readily rehydratable dry fish-like product substantially as hereinbefore described with particular reference to any of the foregoing Examples.

1 2. A rehydratable food product obtained by the method according to any of the foregoing claims.