WO1999060863A2 - A method for preserving food products particularly caviar - Google Patents

Abstract

A method for preserving food products, preferentially roe and most preferably roe from cod, is performed by carrying out the desired end preservation at the raw material stage. A salting at the raw material stage results in a severely reduced consumption of salt. Preservation with salt can be carried out in combination with one or more preservatives such as sugar, benzoic acid and derivatives thereof, sorbic acid and derivatives thereof, organic acids and salts thereof and acidity regulating agents.

Description

A METHOD FOR PRESERVING FOOD PRODUCTS PARTICULARLY CAVIAR

It is a well known phenomenon that food products must be preserved, and it is also well known that raw materials for later processing in the production of food products often must also be preserved to prevent deterioration, particularly due to effects of microbial growth.

A method that is often used is the so-called preservation by low water activity (a_w).

The low water activity is attained by adding low molecular compounds such as cooking salt (NaCl) and/or various types of sugars (such as sucrose, glucose, fructose, maltose or lactose) or also sugar alcohols (such as sorbitol, mannitol, inositol or xylitol) to the food raw materials.

Today it has been determined, however, that excessively high levels of such low molecular compounds should preferably be avoided from a health point of view. In particular, a high intake of salt and sugar in the population is undesirable, and a high intake of sugar alcohols has a laxative effect.

In addition to this, it is a disadvantage that excessively high, and even high, concentrations of the low molecular compounds often impart a taste to the raw material, a taste which is carried over to the products that are produced, thus severely limiting the utilization of the raw material.

The present invention relates generally to a method for preserving food products, but it concerns in particular a method for preserving caviar and particularly cod roe caviar.

Roe is a raw material that is perishable. The roe is harvested in large quantities during a relatively short season, and its industrial utilization therefore necessitates the preservation of the roe already at the raw material stage.

Roe is traditionally preserved by canning/bottling, freezing, salting (NaCl) or sugar- salting (also referred to as "sugar curing" or "pickling") (NaCl + sucrose).

Of these methods, the first two are relatively expensive due to the necessary investments in plants and similar installations and are therefore primarily suited to high priced products. This leads to a preference for more inexpensive methods of preservation such as salting and sugar curing, often in combination with cold storage.

These methods have the drawback, however, of bringing about a high and undesirable salt content in the roe, which means that the roe must either be watered down again prior to use, which is very costly and time consuming, or its use must be limited to products where the high saline content is not considered a problem.

A further disadvantage with salting/sugar curing is that the roe's water content varies with its maturation degree.

The salted/sugar cured roe is preserved by virtue of reduced water activity a_w, and if the water content of the roe is too high, this must in turn be compensated for by an increased, but undesirable, addition of salt.

Still another difficulty in this connection is that the water activity, in practice, is not measured at the location where the roe is packed, meaning that the dosage of salt is carried out on the basis of an estimate.

This means, in turn, that the roe may become oversalted, resulting in the subsequent need for watering down ~ a process which in itself is not damaging, but also that the roe may be undersalted. with the detrimental disadvantage of the roe's fermenting during storage.

The present invention aims to remedy all these deficiencies in a simple and effective matter, at the same time as it provides a raw material that is directly available for further processing without the need for additional preservation.

In accordance with this, the present invention relates to a method for preserving food products, and this method is characterized in that the desired end preservation is carried out at the raw material stage.

Preferentially the method is applied to roe, and most preferably to cod roe.

The invention's method for preservation, particularly of roe, is based on the so-called hurdle technology. Instead of only basing the preservation on one principle (the aforementioned reduced water activity a_w), the preservation is now based on several principles that individually would probably not impart sufficient keeping quality to the roe, but which in combination provide a good result.

An advantage of this is a significant reduction in the amounts of preservatives (salt) that are not always equally desirable, and also the fact that one is not as dependent on being able to estimate precisely the water content of the roe during the preserving process.

The roe is preserved by a combination of reduced water activity by virtue of the addition of salt, but in significantly lower quantities than with traditional salting/sugar curing, further reduced pH, low storage temperature (cold storage), and the addition of conventional preservatives that are approved for use in food products.

It should not be necessary to point out that the latter types of preservatives are preferentially selected among those already used in products that are produced using roe raw materials as a point of departure.

This has the additional advantage of reducing the costs of preservatives to a minimum.

According to the invention, the addition of the preservatives is transferred from the end product to the raw material, and the preservative is then allowed to remain with the goods all the way to the end product, where it will continue to impart its desired effect.

The end product consists, as a rule, of other components in addition to the roe, and by the method of the invention it is possible to increase or adapt the addition of the preservative in the raw material to correspond to the "dilution" which occurs during the processing and further refining toward the end product.

In this manner one achieves an enhanced preservative effect in the raw material without said effect interfering with the taste properties or conflicting with the provisions stipulated in the laws or regulations for the end product.

Here it should be pointed out that the choice of preservative cannot, of course, be undertaken entirely without restriction where food products such as roe, for example, are concerned. It is a precondition, of course, that the preservative must be suitable for being added to the end product. Accordingly, this additive also must not result in any significant, and certainly not any unfavorable, effects with regard to taste. Finally, and by no means of least significance, the preservative must have a positive effect on the keeping quality of the raw material. This can be governed in part by a proper control of the other attendant conditions such as, for example, the pH value.

Experiments have been carried out on the preservation of cod roe for production of caviar emulsion by the utilization of a combination of salt, acetic acid and sodium benzoate.

The pH value in the roe is reduced somewhat by the addition of an inorganic acid such as hydrochloric acid or phosphoric acid in order thereby to increase the anti-microbial effect of acetic and benzoic acid; this must be balanced, however, against the effects on the taste of the end product.

Na-benzoate is used today as a preservative in caviar emulsions, and the dosage of Na- benzoate in the roe is adapted to this additive.

Compared with traditional salting or sugar curing, one attains by the method of the invention, in addition to the simplified process, a substantial reduction in the amount of salt. In traditional salting/sugar curing there is used 14 kg or more of salt per 100 kg of fresh roe. By the invention's method, the amount of this addition may be reduced considerably, even to as low as 4 to 5 kg salt per 100 kg fresh roe.

This has rather significant economic implications, of course, but in addition it also has substantial significance with regard to health.

As indicated above, the proposed process is not limited to cod roe, but can be applied without major modifications to roe from other types of fish such as capelin, salmon, trout, lumpfish, catfish, and sturgeon, and also shellfish such as crab and lobster.

The process of the invention, that is, the transfer of the addition of preservatives from the end product to the raw material, can also be utilized on other products which are currently being preserved by salting, and of which the following examples can be mentioned: In the same manner as roe (which, in principle, is egg), egg yolk that is preserved by salting can be treated with the same preservatives as are used in the finished products such as mayonnaise, remulade, dressings and other products derived from mayonnaise.

Fish is currently cured in salt brine for later use in semi-preserves (perishables) such as pickled herring, pickled brisling, pickled herring filets, anchovies, etc. The same preservatives that are used in the end product can advantageously be added already during the pickling stage.

Vegetables that are preserved by salting in order to be used later on in end products such as peas, beans, onions and cauliflower can be treated with the same preservatives as those that go into the end product.

Meat that is to be salted in order to be used later on in blended products to which preservatives will be added can be treated with these same preservatives during the salting.

The invention will be described with the aid of the following example.

Example of preservation process

Fresh cod roe was pressed out of the roe sacks, blended well and mixed with sea water from Trondheim Harbour in an amount of 24 ml/kg roe in order to ensure that the roe contained from the outset a varied flora of micro-organisms.

The roe was then divided into two portions, part A and part B.

To part B was added sodium benzoate in an amount of 2.4 g/kg roe and concentrated acetic acid in an amount of 2.1 g/kg roe, both parts dissolved in a smaller amount of pure water (8- 10 ml/kg roe).

Both part A and part B were then divided into 15 smaller portions, and NaCl was added, as indicated in Table 1.

After the addition of salt, the pH value was adjusted with hydrochloric acid to a pH of 4.7 to 4.9 in portions from part B. The pH value in part A was not adjusted, but varied in the pH range of 5.5 to 6.0, depending on the salt concentration, with the pH value decreasing with an increasing amount of salt.

The roe was then transferred to a Hungate tube that was closed by a cork having a rubber septum. After closing the tube, the air pocket above the roe mass in the tubes was flushed with nitrogen gas to obtain approximately anaerobic conditions corresponding to the conditions under which the roe is stored in filled barrels.

The Hungate tubes were then incubated at 30°C and 15°C. At regular intervals the pressure in the Hungate tubes was measured by inserting the tip of a syringe coupled to a manometer through the rubber septum.

The microbial growth in the roe resulted in the formation of CO2 and, in some cases, other gases and thus brought about a pressure increase in the tubes. Tubes with an overpressure of >0.3 atmospheres were regarded as being microbially spoiled, whereas tubes where an overpressure of 0.1 to 0.3 atmospheres was registered were regarded as doubtful.

The obtained results are shown in Table 1 and indicate a clearly positive effect of the added preservatives combined with salt and reduced pH value on the keeping quality of the roe.

Table 1: Storage of salted roe with and without Na-benzoate and acetic acid in Hungate tubes under approximately oxygen-free atmosphere. The time period for significant pressure increase (>0.3 atm overpressure) was registered as a measurement of microbial spoilage. Tubes wherein an overpressure of 0.1 to 0.3 atmospheres was measured are indicated by parentheses.

Claims

P a t e n t C l a i m s

1.

A method for preserving food products, characterized in that the desired end preservation is carried out at the raw material stage.

2.

A method according to claim 1, characterized in that roe is used as the raw material, preferentially roe from cod.

3.

A method according to claims 1 and 2, characterized in that the roe product is preserved with 1-12 kg and preferably 4-8 kg salt/100 kg fresh roe.

4.

A method according to any one of the claims 1-3, characterized in that fresh roe raw material is preserved with salt in a combination with one or more of

sugar 0-120 g/kg roe raw material - benzoic acid, its salts and derivatives 0-10 g/kg roe raw material sorbic acid and its salts 0-5 g/kg roe raw material organic acids such as acetic acid, propionic acid and lactic acid and their salts 0-10 g/kg roe raw material - acidity regulating agents such as organic acids exemplified by ascorbic acid, malic acid, citric acid, butyric acid and tartaric acid; and inorganic acids such as phosphoric acid to a pH in the range of 6.5 to 3.