GB2126868A - Method of improving the shelf life of processed meat products - Google Patents

Abstract

The shelf life of processed meat products (especially sausages but also products such as meatballs, hamburgers or ham) can be significantly increased, even under adverse storage conditions, by immersing the product in a brine having a water activity not exceeding 0.95 and a pH of from 4.5 to 5.8. In addition to salt, the brine also contains a pH-reducing agent and sufficient of such additives as are present in the processed meat product such that the percentage loss or gain in weight of the said product after immersion in said brine for 14 days at ambient temperature does not exceed 10%. The brine preferably has a salt content of 5-11.5% by weight.

Description

SPECIFICATION Method of improving the shelf life of processed meat products The present invention relates to a method of improving the self life of processed meat products.

The term "processed meat products" is here defined to mean a meat product to which has been added one or more ingredients and/or additives which either are not naturally present in the meat or are added in amounts in excess of those naturally present in the meat.

The preservation of meat products has exercised the ingenuity of mankind since prehistoric times. The problem is that it is difficult to reconcile the two requirements of (a) preserving the meat from decay and (b) preserving the desirable texture, flavour and "mouthfeel" of the meat.

In the highiy industrialised countries of the West, the problem has largely been solved by refrigeration, freezing, canning or vacuum-packing, although even these expedients are not always wholly satisfactory, e.g. for itinerant or street salesmen of comestibles. In other countries, the infrastructure necessary to make refrigeration, canning or vacuum-packing available on a significant and affordable scale often simply does not exist. Moreover, because of the capital costs involved in such processes as canning or vacuum-packing, it is normally necessary that meat products packaged in this way should be packaged in significant quantities, for example, in the case of sausages of the "frankfurter" type, these would normally be canned with 6, 10 or more sausages in each can.Such a quantity of sausages may exceed the consumer's needs and, in the absence of domestic refrigeration, the excess sausages may be impossible to preserve. As a result, such a can simply would not be bought.

In many developing countries, sausages, which now form a significant part of the individual's protein intake, are often bought singly without any signifant attempt to preserve them. For example, in the Phillipines, such sausages are often sold in open markets, may be frequently handled and can constituted a significant health hazard.

There is, therefore, a need for a method of improving the shelf life of processed meat products which, even if it is unable to match the shelf life of products preserved by canning or vacuum-packing, is less costly and is usable by people having a lesser degree of technological expertise, those people in developing countries and others without access to higher level technology, for example, itinerant or street salesmen in developed countries.

The present invention accordingly provides a method of increasing the shelf life of processed meat products (as hereinbefore defined) by immersing the product in a brine having a water activity not exceeding 0.95 and a pH of from 4.5 to 5.8 and containing salt, a pH-reducing agent and sufficient of such additives as are present in said product that the percentage loss or gain in weight of said product after immersion in said brine for 14 days at ambient temperature does not exceed 10%.

Although the method of the present invention is applicable to all types of processed meat product, it is of particular value when applied to such products which are normally provided in individual portions, for example meatballs, hamburgers (including such variants often known as beefburgers, chickenburgers, turkeyburgers etc. on the basis of their meat content or predominant meat flavour) and sausages (particuiarly those of the frankfurter type).The invention can also be applied to ham, although it is preferred that the ham should not be employed whole but should be cut into portions having a thickness of from 0.5 to 3 cm, as, if the ham is too thick, only the outermost portion is likely to be treated by immersion in the brine of the invention during the likely storage time of a few weeks, whereas, if the ham is too thin, it will be difficult to formulate a brine which does not substantially affect the flavour of the ham.

The water activity of the brine is an important element of the present invention. It is necessary to maintain the water activity at a relatively low level in order to prevent or at least minimise growth of harmful and spoilage bacteria and other microorganisms. In accordance with the present invention, the water activity is reduced by incorporating into the brine, in addition to the necessary sodium chloride, one or more compounds capable of reducing the pH of the solution, one or more of the compounds which are present as additives in the processed meat product and, if desired, one or more other of another class of compound which is capable of reducing water activity without adding significant flavour.

The maximum water activity of the brine in accordance with the present invention is 0.95, but we prefer that the water activity should be below this, e.g. from 0.88 to 0.94, more preferably from 0.90 to 0.93 and most preferably about 0.925. The water activity herein is measured by hygrometry.

The other characteristics of the brine employed in the present invention are interrelated in that, for example, if the brine has a relatively low pH value, then it can also have a relatively low salt content, whereas, if the pH value of the brine is relatively high, then the salt content also should be high. Equally, relatively low salt concentrations in the brine can be achieved if the level of other additives is increased. Accordingly, the following ranges are suggestions within which the optimum brine composition may be achieved, but it will be appreciated that variations may be permitted in order to achieve a particular flavour to suit particular storage conditions or particular markets.

The pH value of the brine must be within the range from 4.5 to 5.8. At the extreme limits of this range, the product will either develop a rather acid taste (at pH 4.5), which will be undesirable for certain applications or will have reduced storage stability (at pH 5.8). Accordingly, we prefer that the pH should be within the range from 5.3 to 5.5, more preferably about 5.4, at which point the conflicting requirements of good storage stability and good flavour will generally be in balance.

The amount of salt (i.e. sodium chloride) in the brine will depend upon the pH value of the brine and upon the level of other ingredients in the brine. If the salt level is too high, then too much salt may be taken up by the meat product, either by osmosis or simply by entrainment on the surface of the product. The salt level in the brine should also be chosen having regard to the level of salt in the processed meat product. A typical hot-dog sausage would normally have a salt content of from 4 to 7 percent by weight of the water phase in the sausage and it is clearly desirable that the salt level in the brine should be so chosen as not to increase unduly the salt level in the processed meat product.

Accordingly, we prefer that the amount of salt should be from 5 to 1 1.5% by weight; this percentage, like all percentages hereinafter relating to the brine, is the concentration of the component concerned in water (i.e. is based on the weight of the water only) and takes no account of the presence of other materials in the brine solution. At a level of 5% by weight of salt, a relatively low pH, e.g. about 4.5, is necessary in order to achieve sufficient storage stability. On the other hand, a level of 1 1.5% by weight of salt may make the product too salty for many purposes. It is for this reason that the brine employed in the present invention must be a multi-component brine, since the level of salt alone needed to achieve a water activity of no greater than 0.95 would render the product too salty to be palatable.A more preferred range of salt concentration is from 7.5 to 1 1.5% by weight, most preferably from 7.5 to 10% by weight.

Towards the higher salt concentrations within the above ranges, it may be desirable to include material capable of masking the salt flavour. A variety of materials capable of achieving this are well known to the art; examples include lactose, sucrose, dextrose and maltodextrins, of which lactose or a mixture of lactose with the maltodextrins is prefered. The amount of this material capable of masking salt flavours will, of course vary depending on its efficacy and upon the amount of salt in the brine as well as upon the taste preferences in the market where the product is to be sold.In general, however, we prefer that the amount of this material should be within the range from 8 to 45% by weight, more preferably from 10 to 35% by weight and most preferably from 12 to 30% by weight For example, where the salt concentration in the brine is from 7.5 to 10% by weight, the concentration of the saltmasking material would preferably vary correspondingly from 8 to 50% by weight; if the concentration of salt is as high as 1 1% by weight, then the concentration of this material is preferably from 20 to 30% by weight. However, a salty taste may be acceptable or even required for certain products and/or markets and, in that case, the concentration of salt-masking material may be reduced, even if there is a high salt concentration.Where a mixture of two or more different materials is employed, the balance between them will depend upon their taste characteristics and the desired taste of the final product; in the case of maltodextrins and lactose, however, a preferred weight ratio of maltodextrins to lactose is from 2.5:1 to 1:2.5.

Another essential component of the brine employed in the present invention is an agent capable of reducing the pH value of the brine; it will also, of course, assist the reduction of the water activity of the brine. Examples of materials which may be used to reduce the pH value of the brine include such acidic salts as acid phosphates, and such edible acids as phosphoric acid or acetic acid. However, since the purpose of the pH-reducing agent is to reduce the pH value of the brine without significantly or unavoidably affecting the flavour of the product, we prefer to use an acid phosphate, for example acid sodium pyrophosphate. Acid phosphates also have the advantages that they are much more gentle than acids in reducing pH and they they have a buffering capacity, which can be of some importance should the pH of the meat vary.The amount of pH-reducing agent employed will, of course, depend upon the desired pH of the brine and can easily be calculated by those skilled in the art. Some of the other components of the brine may also have the effect of reducing (or increasing) the pH of the brine. For example, the smoke flavour commonly employed in meat products and which may (as discussed hereafter) be incorporated in the brine has a base of acetic acid and hence necessarily has the effect of reducing pH; such components must be taken into account when determining the amount of.any component added primarily to reduce pH.

In addition to the specific materials described above, it will also be necessary to incorporate into the brine one or more of the additives present in the processed meat product; this in order to prevent such additives being leached from the product by the brine. Examples of additives which might be included in the product and which should, therefore, also be included in the brine, include nitrites and/or nitrates (for example sodium nitrite, potassium nitrite, sodium nitrate and potassium nitrate), ascorbates (particularly sodium ascorbate), citrates (particularly sodium citrate), food grade phosphates (for example trisodium polyphosphate), seasonings other than salt (for example monosodium glutamate and hydrolised proteins), additional flavouring agents (e.g. smoke flavour) and colouring agents. The inclusion of at least one nitrite is also preferred as the nitrites are bacteriostatic. The levels of such additives in the meat product will depend upon the particular product and the market for which it is intended; in any case, it is desirable that the concentration of such additives in the brine should be as close as possible to their respective concentrations in the aqueous phase of the meat product, in order to prevent leaching of the additives from the product or, conversely, addition of the additives to the product from the brine, by osmosis. The level of these additives, as well as the level of the other ingredients of the brine should be so chosen as to minimise the loss or gain in weight of the product during the period of its storage.In any case, the level should be such that the loss of gain in weight of the product over a 14 day period at storage temperature does not exceed 10%. In practice, by careful adjustment of the components of the brine, it is possible to reduce the loss or gain in weight of the product to a very low level, e.g. below 5%, frequently below 1% and often below 0.5%.

All of the materials discussed above will, to some extent, function to reduce the water activity of the brine. In many cases, however, the amount of such materials which can be incorporated into the brine without adversely affecting the flavour or other qualities of the processed meat product will be too low to reduce the water activity of the brine to an acceptable level. In this case, it will be necessary to incorporate into the brine another class of solute which reduces water activity without adding significant flavour, although they may have a sweetening effect. Examples of such solutes include the maltodextrins, polyhydric alcohols (e.g. glycerol, propylene glycol, sorbitol or mannitol), edible acids (e.g.

sorbic acid or citric acid), salts (for example, apart from those previously listed for other purposes, the sorbates, especially sodium sorbate), sugars (e.g. sucrose, dextrose, fructose, lactose, maltose and invert sugar - a mixture of fructose and glucose), corn syrup or molasses, preferably the maltodextrins.

It will, of course, be appreciated that, at high salt concentrations, this additional class of solute may not be necessary. Certain of these materials will also, as previously noted, also have the effect of masking salt flavour.

Of course, the requirements of the present invention may be met not merely by formulating a specific brine to match the formulation of the meat product, but also be adjusting the formulation of the meat product to match the composition of the brine; for example, if it is desired to incorporate maltodextrins in the brine to reduce water activity and to mask the flavour, then it may be desirable to incorporate the same maltodextrins in the meat product (even if they are not necessary to the formulation of that product), in order to provide a balance of ingredients in the product and the brine.

We have surprisingly found that the method of the present invention has an additional advantage over conventional processes for the long term preservation of meat products. Such processes normally involve sterilization of the product and this sterilization can have an adverse effect upon the texture of the product, particularly where it has a relatively low meat content -- rather than the fibrous texture associated with meat products, heat-sterilised meat products generally aquire a jelly-like texture, which the consumer does not readily associate with meat-containing products. By avoiding the need for sterilization, the present invention makes it possible to achieve the fibrous, chewy texture of real meat, even when the actual meat content of the product is substantially lower than that of sterilized products.

The invention is further illustrated by the following Examples; the maltodextrins used in the Examples had a dextrose equivalent between 20 and 1 7.

COMPARATIVE EXAMPLES 1-3 The sausage (hot dog) employed in this Example had the following composition (percent by weight); Beef 10.00 Purina Protein 500E 7.00 Rind 10.00 Back fat 24.00 Salt 3.00 Maltodextrins 2.00 Lactose 2.75 Colour 2.00 Acid sodium pyrophosphate 0.50 Farina (a potato starch) 5.00 Water 33.01 Smoke flavour 0.25 Sodium nitrite 0.02 Spices 0.46 Red 2G colour (diluted 1:9 by volume) 0.01 These were immersed in brines having the compositions shown in the following Table 1 at 370C.

The sausages were periodically examined and their stability is reported in the Table in terms of the number of days after which they would have been regarded as inedible, as determined by their appearance and smell. At the end of their period of stability, i.e. 2, 7 and 12 days for Comparative Examples 1,2 and 3, respectively, the sausages were weighed to determine the percentage increase or decrease in weight, and this is also reported in Table 1.

TABLE 1

Comparative Example No.

1 2 3 Ingredient A B A B A B Salt 5.25 5.7 5.25 5.9 8.25 9.8 A's.P. 0.50 0.55 1.00 1.1 1.50 1.8 NaNO2 0.04 0.044 0.04 0.046 0.04 0.048 Water 91.46 - 89.58 - 84.08 pH 4.35 3.80 3.49 Aw 0.97 0.97 0.95 % increase 8.43 9.27 8.61 Stability 2 days L 7 days > 12 days In the above Table, the abbreviation "A.S.P." means "acid sodium pyrophosphate" and the abbreviation "Aw" means water activity, as determined by hygrometry.

The concentration of each of the components of the brine is reported in two ways: in column A as the percentage by weight of the component based upon the total weight of the brine; and, in column B, based upon the weight of water only; the same applies in subsequent Examples.

All of the sausages were tasted after a few days immersion but before they had become inedible, and all were found to have a poor colour, were salty (although the salt concentration of the brine was not excessively high) and had an undesirable acidic flavour due to the low pH of the brine. The storage stability of the products of Comparative Examples 1 and 2 would be regarded as too low and, in any case, all of the products would be regarded as undesirable in view of their poor colour and flavour.

EXAMPLES 1-6 The sausages (hot dogs) used in these examples had the following composition (percentages by weight): Beef 10.00 Purina Protein 500E 7.00 Rind 10.00 Back fat 23.37 Salt 1.50 Maltodextrins 2.00 Dextrose 0.50 Colour 0.30 Acid sodium pyrophosphate 0.20 Farina 4.00 Water 28.00 Ice 4.00 Frozen beef blood plasma 8.00 Smoke flavour 0.40 Sodium nitrite 0.70 Spices 0.70 Sausages having this composition were wholly immersed in one of the brines whose composition is shown in the following Table 2 and stored at 370C for the period of the test. Periodically throughout the test, the sausages were weighed to determine the loss or gain in weight; the results are reported in Table 2 for the loss or gain after 14 days (a negative increase indicates that the weight of the sausage decreased by the stated percentage).After 12 days, samples of each of the sausages were taken to determine the bacterial count after incubation of the sample or nutrient agar at 300C for 3 days. The resulting plate count is also reported in Table 2.

TABLE 2

Example No.

1 2 Ingredient A B A B Maltodextrin 5.00 6.5 5.00 6.5 Salt 6.00 7.7 7.00 9.1 Lactose 6.97 9.0 6.97 9.0 A.S.P. 1.47 1.9 1.47 1.9 NaNO2 0.04 0.05 0.04 0.05 TSPP 1.96 2.5 1.96 2.5 Water 78.26 - 77.26 Smoke flavour 0.24 0.31 0.24 0.31 Red 2G (1::9) 0.06 0.077 0.06 0.078 Aw 0.95 0.94 pH 5.50 5.45 % increase 4.07 0.94 Plate count 12,000 500 TABLE 2 (Continued)

Example No.

3 4 5 6 A B A B A B A B 5.00 6.9 - - - - 14.0 20.3 8.00 11.1 8.00 9.8 9.00 11.2 7.0 10.1 10.97 15.2 6.93 8.5 6.93 8.6 8.0 11.6 1.47 2.03 1.47 1.8 1.47 1.8 1.0 1.4 0.04 0.055 0.04 0.05 0.04 0.05 0.04 - 1.96 2.7 1.96 2.4 1.96 2.4 1.0 1.4 72.26 - 81.30 - 80.30 - 69.0 - 0.24 0.33 0.24 0.30 0;24 0.30 0.24 - 0.06 0.083 0.06 0.073 0.06 0;075 0.06 - 0.93 0.94 0:93 0.93 5.35 5.50 1 5.40 5.50 -6.98 3.07 -0.16 -5.0 12000 200 2,300 < 10,000 In the above Table, 'TSPP" meanstrisodium polyphosphate and "Red 2G (1:9)" means the Red 2G food dye diluted with water in a volume ratio of 1:9.

All of the above samples still appeared in good condition after being kept for 14 days at 370C, although this is a higher temperature than they could expect to encounter for substantial periods of time in most instances. At the end of the initial 14 day trial, the brine of Example 1 shows a slight sediment, whilst all of the other brines were clear. All of the sausages were palatable and meaty, although the actual beef content was only 10% by weight. All of the sausages had retained their desirable meaty colour.

Samples of the sausages were fried until completely cooked and were then tasted. All samples had the chewy, rather fibrous texture of meat and gave the impression of containing minced particles of meat; by way of a contrast, a commercially available canned hot dog having a beef content of about 25% was also fried. This had a homogenous jelly-like texture lacking the desirable masticating qualities of meat.

Claims (22)

1. A method of increasing the shelf life of processed meat products (as hereinbefore defined) by immersing the product in a brine having a water activity not exceeding 0.95 and a pH of from 4.5 to 5.8 and containing salt, a pH-reducing agent and sufficient of such additives as are present in said product that the percentages loss or gain in weight of said product after immersion in said brine for 14 days at ambient temperature does not exceed 10%.

2. A method according to claim 1, in which said water activity is from 0.88 to 0.94.

3. A method according to claim 2, in which said water activity is from 0.90 to 0.93.

4. A method according to claim 3, in which said water adtivity is about 0.925.

5. A method according to any one of the preceding claims, in which said brine has a pH of from 5.3 to 5.5.

6. A method according to claim 5, in which said brine has a pH of about 5.4.

7. A method according to any one of the preceding claims, in which said brine has a salt content of from 5 to 11.5% by weight (based on the total weight of salt and water).

8. A method according to claim 7, in which said salt content is from 7.5 to 11.5% by weight.

9. A method according to claim 8, in which said salt content is from 7.5 to 10% by weight.

10. A method according to any one of the preceding claims, in which said pH-reducing agent is an acid salt or an acid.

11. A method according to claim 10, in which said pH-reducing agent is an acid phosphate.

12. A method according to claim 11, in which said acid phosphate is acid sodium pyrophosphate.

13. A method according to any one of the preceding claims, in which said brine additionally comprises a material capable of masking salt flavour.

14. A method according to claim 13, in which said material is lactose or a mixture of lactose and maltodextrins.

1 5. A method according to any one of the preceding claims, in which said brine additionally comprises another class of solutes which reduces water activity without adding significant flavour.

1 6. A method according to claim 1 5, in which said solute is a maltodextrin.

17. A method according to any one of the preceding claims, in which said meat product is a meatball, hamburger or ham.

1 8. A method according to any one of claims 1 to 16, in which said meat product is a sausage.

1 9. A method according to claim 1, substantially as hereinbefore described with reference to any one of foregoing Examples 1 to 5.

20. A processed meat product in a brine as defined in claim 1.

21. A processed meat product in a brine as defined in any one of claims 2 to 16.

22. A processed meat product as claimed in claim 20 or claim 21, which is a sausage.