IE46361B1 - Improvements in or relating to continuous food impregnation - Google Patents

Abstract

The continuous impregnation method, in which pieces of a food material to be impregnated are immersed in a concentrated solution of an impregnating agent, these pieces being initially light and floating in the solution and following, with this solution, a path leading to a zone of separation where the impregnating solution flows downwards at a faster speed than the flow speed of the food material, so that the pieces of food material which, by absorption of the desired quantity of the impregnating agent, have lost sufficient of their lightness or floatability in the surrounding impregnating solution to be removed downwards by this solution, are thus continually separated from the pieces of food material which have absorbed less than the desired quantity of the impregnating agent, applies to a food material chosen from meat, eggs, fish or textured vegetable proteins.

Description

This invention relates to a method of continuous food impregnation.

The present applicationis for a Patent of Addition to our earlier Patent No, A-blSS (Patent Application No, 221/77 ), which describes and claims a method of continuous impregnation of food material wherein pieces of food material to be impregnated are immersed in a concentrated solution of an impregnant, said pieces being initially buoyant in said solution and being passed together with said solution along a flow path to a separation zone wherein the impregnation solution flows downwards at a rate greater than the rate of downward flow of the food material whereby those pieces of food material which, by absorption of the desired quantity of impregnant, have lost sufficient of their buoyancy in the surrounding impregnation solution to be carried downwards by the said solution, are thereby continuously separated from pieces of food material which have absorbed less than the desired quantity of impregnant.; : In our abovementioned Patent No, (Patent Application No 221/77 )} we have described, in particular,the Impregnation of vegetables and fruits by brining or syruping using the above method.

We have now applied this method to the impregnation of further types of food material, namely, meat, eggs and fish. - 2 46361 Thus, according to the present invention there is provided a method for the continuous impregnation of foods selected from meat, eggs, fish and textured vegetable protein wherein pieces of said foods to be impregnated are immersed in a concentrated solution of an impregnant, said pieces being initially buoyant in said solution and being passed together with said solution along a flow path to a separation zone wherein the impregnation solution flows downwards at a rate greater than the rate of downward 10 flow of the food material whereby those pieces of said foods which, by absorption of the desired quantity of impregnant, have lost sufficient of their buoyancy in the surrounding impregnation solution to be carried downwards by the said solution and are thereby continuously separated from pieces of said foods which have absorped less than the desired quantity of impregnant.

The term fish as used herein is intended to include within its scope all types of edible sea and fresh water animals such as fish per se , Crustacea (for example crab and lobster meat and shrimps, prawns etc,), molluscs (for example, mussels, whelks and squid etc.) and the like.

It will be appreciated that the term meat is intended to include within its scope poultry meat.

In general, the food pieces wich may be processed by the method of the present invention should be in the form - 3 46361 of a cohesive solid rather than a friable or non-cohesive solid. Thus, it is preferred to use lightly cooked meat or fish in the present process or hard-boiled whole eggs. If, for example, on the other hand over-cooked meat or fish or the yolks of· hard-boiled eggs are used, there is a danger that the food pieces will break up during the impregnation process. It will be appreciated that the term food .pieces ” means discrete masses of food in contrastto pastes or mashes and other semi-solid food materials. The food pieces may be whole natural pieces of food such as eggs or small fish, sections of the natural food source, for example cubes or slices of meat or fish, or may be reconstituted food pieces such as reconstituted soy protein chunks.

In the process of the present invention, the concentration of impregnation solution is chosen so that the food pieces are initially buoyant in the impregnation solution. However, during the impregnation process individual food pieces absorb impregnation solution and eventually reach the point near the end of the flow path when their buoyancy is nearly equal to that of the surrounding impregnation solution at which point these fully impregnated food pieces can be separated from the more buoyant insufficiently impregnated food pieces by the continuous downflow of impregnation solution. - 4 Thus, the >46361 specific gravity of the initial impregnation solution is selected to provide a specific gravity, after absorption of impregnant by the food, which is approximately equal to the specific gravity of the pieces of food containing A the desired quantity of impregnant. The specific gravity of meat, fish and eggs is close to unity, whereas the specify, gravities of most impregnation solutions which may be desired will, be significantly higher.

Impregnation solutions which may be used in the method of the present invention are, for example, sugar syrups, brines,meat curing solutions, humectant solutions and mixtures thereof. It should be noted that the same substances, for example sugars, may sometimes be used for different purposes, e.g. as syrups impregnated into fruit as. described in our ahove application or as humectants 'impregnated into meats etc. Such solutions are relatively concentrated and’have specific gravities significantly higher than unity.

Thus, for example, eggs may be Impregnated with brine so that they have a final salt content of about 15%, by using brine of salt strength between about 19 and 22% w/w as the impregnant solution. When treating eggs in this manner they are preferably first hard-boiled and shelled before being subjected to impregnation. - 5 4 6 3 81 By the method of the present invention it is possible to impregnate,for example, meat with humectant solution and thus prepare preserved meat without using . traditional preservative solutions. The use of humectants 5 far the impregnation of foods is useful for the preparation of so-called intermediate moisture food products.

Suitable impregnants for the preparation of these intermediate moisture food products are, for example, solutions of substances selected from dextrose, glycerol, sorbitol, salt, fructose, sucrose and mannitol or other suitable polyhydric alcohols; it is frequently advantageous to employ two or more of such substances simultaneously, for example salt and glycerol and/or glucose. Propylene glycol may also be used, but as it has a specific gravity of approximately unity, this should be used in combination with one or more of the above substances.

Our Patent Specification No. (Patent Application No. ,22//77 ) describes and claims apparatus for the continuous impregnation of food and such apparatus may be used for effecting the method according to the present invention.

In an embodiment of the present invention, the whole impregnation and separation procedure may be effected in a single tower-like vessel, the food material in the form of pieces being introduced at the top of the tower. The food pieces may be transferred to the top of the tower by conventional means such as bucket elevation or pumping in water. In the latter case, the - 6 4 6 3 61 food pieces can be dewatered by means of a sieve or dewatering reel before entering the tower.

Impregnation solution of substantially constant concentration is pumped in at the top of the tower through a sprinkler system.

The concentration of impregnant in the impregnation solution depends on the final content desired in the food material. Mixtures of impregnants may also be used.

The food pieces then flow along the impregnation 10 flow-path for the time required to raise the content of the impregnant in the food pieces to the level desired.

This time depends on factors such as the particular food to be treated, the concentration of impregnant, the working volume of the tower and the relative throughput rates of solution and food material. At the end of the required time the food pieces have progressed to the base of the tower and their specific gravity is very near to that of the output solution so that they can be easily removed from the tower. Removal from the tower may be aided by agitating the material mass at the base of the tower conveniently by mechanical means but more preferably by means of jets of spent impregnation solution. Removal may be effected by food pumps employing the spent solution as a carrier medium. - 7 46 361 The food material may then be pumped to storage containers. Impregnated food material may be separated from the impregnation solution and the latter may be reinforced with further impregnant and then reused for impregnation, The rate of flow of impregnation solution down the tower should be greater than that of the food pieces.

Thus ensuring that there is comparatively little reduction in the specific gravity of the solution on reaching the separation.zone and the flow of solution past the food pieces is necessary to carry the food pieces of low buoyancy downwards from the pieces of higher buoyancy. In general, the ratio of the flow rate of the solution to the flow rate of the food pieces is preferably at least 4:1 and advantageously in the range 10:1 to 40:1 for example, about 20;1. The use of jets of spent solution at the bottom of the tower not only effects the agitation which permits separation of the food pieces but also increases the flow rate of solution at that point, thereby further assisting separation. In general, the ratio of the initial volume of impregnation solution used to impregnate the food pieces to the volume used for agitation may be in the range of from 10:1 to 1:2. - 8 46361 The following Examples serve to illustrate the method according to the invention:9 3 6 1 Example 1 325.4 kg of whole hard boiled and shelled standard'eggs were added to the top of an 0,46 metre diameter hy 3,64 metre high tower from a vibrator over a period of 1440 .-. minutes (0.226kg/minute). Over the same time period, brine of salt strengh between 19,0% and 21.3% w/w was pumped from a brine production through a sprinkler system into the' top of the tower at a rate of 9litres/minute and at a temperature of 50°C, After travelling to the coniform base of the tower,' the eggs were agitated by a series of brine jets feeding at 9 litres/minute from a spent brine 1 tank. The eggs and spent brine were removed from the tower using a pump and pumped to a sieve system over the spent brine tank. The tower required 960 minutes to fill and after thi.·· time the; eggs emerged from the tower at a rate of 0.181 kg/ minute which was equivalent to the input rate if account was taken of the normal weight losses occurring during brining. The salt content of the finished brined eggs varied between 14,4% and 15.2% w/w during the run and the spent brine strength varied between 18.2% and 20,5% w/w during the run. - 10 46361 Example 2 135.2 kg of deboned and trimmed leg of pork was diced to 12.5 iran cubes and blanched in boiling water for 15 minutes. The resulting 98,4 kg of cooked meat was added to the top of an 0.46 metre diameter by 1.21 metre high tower from a vibra5 tor over a period of 405 minutes (0.243 kg/minute).

Over the same time period a humectant solution of composition 13% w/w glycerol, 9.1% w/w glucose and 10% w/w salt was pumped from a humectant solution production plant through a sprinkler system into the top of the tower at a rate of 9 litres/minute and at a temperature of 50°C.

After travelling to the coniform base of the tower, the diced meat was agitated by a series of humectant solution jets feeding at 9 litres/minute from a spent humectant solution tank. The diced meat and spent humectant solution were removed from the tower using a pump and pumped to a sieve system over the spent humectant solution tank. The tower required 165 minutes to fill and after this time the diced meat emerged from the tower at a similar rate to the input rate. The composition of the humectant impregnated meat varied between 5.9% and 6,2% w/w glucose,. 8,9% and 9,-2% w/w glycerol and between 7.2% and 7.4% w/w salt.

'The composition of the spent humectant solution varied between 8,5% and 8.9% glucose, 12.1% and 12.8% w/w glycerol and between 9.6% and 9.9% w/w salt The water activity of the meat sample, as measured by the manometric technique, varied between 0. 898 and 0.923.

Claims (17)

1. What we claim is:' 1 1/ A method for the continuous impregnation of foods selected from meat, eggs, fish and reconstituted vegetable protein wherein pieces of said foods to be impregnated are immersed in a concentrated 5 solution of an’impregnant, said pieces being initially buoyant in said solution.and being passed together with said solution along a flow-path to a separation zone wherein the impregnation solution flows downwards at a rate greater than the rate of downward flow of 10 the food material whereby those pieces of said foods which, by absorption of the desired quantity of impregnant, have lost sufficient of their buoyancy in the surrounding impregnation solutiqn to be carried downwards by the said solution and are thereby continuously 15 separated from pieces of said foods which have absorped less than the desired quantity of impregnant.

2. A method as claimed in claim 1 in which said separation is effected in a tower into the top of which the food pieces and impregnation solution are 20 introduced while low buoyancy food pieces and impregnation solution are continuously removed from the bottom.

3. , A method as claimed in claim2 in which the food pieces and impregnation solution are introduced separately into the top of the tower and both impregnation - 12 4 6 3 6 of the food pieces and the separation of food pieces of low·buoyancy from those of higher buoyancy is effected.in said tower.

4. A method as claimed in claim 3 in which the ratio 5. Of the rate of flow of the impregnation solution to the rate of flow of the food pieces is in the range 10:1 to 40:1.

5. A method as claimed in any of claims 2 to 4 in which means are provided for agitating food material 10 at or near the bottom of said tower.

6. A method as claimed in claim 5 in which said agitation means include jets of spent impregnation solution.

7. A method as claimed in claim 6 in which the ratio 15 of the volume of impregnation solution introduced at the top of the tower to the volume of impregnation solution used for agitation is in the range 10:1 to 1:2.

8. A method as claimed in any of claims 3 to 7 in which impregnated food pieces together with impregnation 20 solution is removed from the tower by a food pump.

9. A method as claimed in any of claims 3 to 8 in which impregnated food material is separated from impreg nation solution and the latter is reinforced with - 13 46361 Impregnant and re-used for impregnation.

10. A method as claimed in any of claims 1 to 9 in which the impregnation solution comprises sugar syrup, brine, a meat curing solution, a humectant solution 5 or mixtures thereof.

11. A method as claimed in claim 10 in which the humectant solution comprises a solution of one or more substances selected from dextrose, glycerol, sorbitol, salt, fructose, sucrose and mannitol and other suitable 10 polyhydric alcohols,

12. A method as claimed in claim 11 wherein the humectant solution comprises a solution of two or more substances selected from dextrose, glycerol, sorbitol, > salt, fructose, sucrose, propylene glycol and mannitol 15 and other suitable polyhydric alcohols.

13. A method as claimed in any of the preceding claims wherein the food to be impregnated is meat or fish which has been lightly cooked,

14. A method as claimed in any of claims 1 to 12 20 wherein the food to be impregnated is whole eggs which have been hard-boiled and shelled,

15. A method as claimed in claim 1 substantially as herein described,

16. A method for the continuous impregnation of 25 foods selected from meat, eggs, fish and reconstituted - 14 46361 vegetable protein substantially as herein described with reference to any of the Examples.

17. , Impregnated meat, eggs, fish or reconstituted vegetable protein whenever prepared by a method claimed in any of the preceding claims.