WO1996021360A1

WO1996021360A1 - Process for increasing the shelf life of agricultural products

Info

Publication number: WO1996021360A1
Application number: PCT/CH1996/000015
Authority: WO
Original assignee: Innovest Ag
Priority date: 1995-01-13
Filing date: 1996-01-13
Publication date: 1996-07-18

Abstract

In a process for increasing the shelf life of agricultural products like salads, vegetables and fruit, said products are suitably cut up and then subjected to at least one washing process after harvesting. The products are packed following a subsequent drying process. A certain percentage of concentrated hydrogen peroxide is added as a manufacturing aid to the water used in washing the products.

Description

V e r f a r e n z u r E r h a h u n q d e r H a l t b a r k e i t v o n 1 a n d w i r t - s c h a f t l i c h e n P r o d u k t «. in

Technical field

The present invention relates to a method for maximizing the shelf life of agricultural products according to the preamble of claim 1.

State of the art

Efforts to increase the shelf life of food, especially fresh agricultural products, are generally of great importance in the light of a growing earth population, i.e. the need for light, unadulterated and quickly prepared meals is increasing. The focus is on not reducing or falsifying the natural active ingredients (minerals, vitamins, enzymes, etc.) and the natural taste of these agricultural products through the various methods aimed at preservation.

Agricultural fresh products, such as fresh vegetables, salads, fruits etc., are preserved today using a variety of methods. In this context, the following methods are generally known, without claiming to be complete: Drying in general;

Dehydration;

Sterilization by radiation;

Place the products to be preserved in preserving liquids, such as sugar solution, salt solution, organic acids (acetic acid, lactic acid, tartaric acid, etc.)

In general, it can be stated that the methods which have become known are intrinsically complex, they regularly require expensive systems to carry them out, and they lack the diversity and flexibility in the preservation of a wide range of fresh agricultural products. Furthermore, it should not go unmentioned that many preservatives used or substances aimed at the shelf life of the products (for example chlorine, chlorine-containing solutions or chlorine-containing compounds) can lead to intolerance among consumers. It is also a fact that consumers rightly do not want to accept any loss of natural taste in favor of a longer shelf life when it comes to fresh agricultural products: A demand for these that, as far as can be seen, has so far not been met, is known to be Agricultural products tend to shrink and decay after a very short time.

Presentation of the invention

The invention seeks to remedy this. The invention, as characterized in the claims, has the object In a method of the type mentioned at the outset, the reasons are to maximize the shelf life of the products by a process aimed at disinfecting the washing medium and bacterial shielding, without enriching the products with preservatives.

The main advantage of the invention is that the method ensures that the products have a shelf life of well over 5 days at average temperatures from the packaging, without losing their natural properties in terms of nutritional value and taste. Accordingly, the proposal according to the invention allows for the first time a nationwide distribution of fresh agricultural products to be considered without necessarily having to resort to a cold chain. Since the process is also ideal for large production quantities, these products can be sold on a large scale at an affordable price. These products can therefore also be offered in areas where the population cannot be supplied with fresh salad, fresh vegetables and fruits for much of the year.

Another important advantage of the invention is that the products come into contact with a very dilute manufacturing aid, as an aqueous solution, but no residues or traces can be identified after the process has been completed, so that a genuine product with natural ones is always present Properties can be offered to the consumer.

Advantageous implementations of the task solution according to the invention are characterized in the further dependent claims. Exemplary embodiments of the invention are explained in more detail below.

Ways of carrying out the invention, commercial usability

The description of the method used here will primarily refer to salads, although it goes without saying that other agricultural products, such as vegetables, fruits, etc., can also be offered using this method. However, depending on the type of product, there may be slight differences within the range of the specified parameters in individual process steps. Insofar as these deviations are important for understanding the invention, they are recognized at the appropriate point. However, the underlying procedure, in accordance with the subject matter of the invention, has general validity in particular for all fresh agricultural products in question.

Starting from a leaf lettuce variety, such as lettuce, cicorino, etc., the collected lettuce is sent to an armory without pretreatment, where the products are prepared in the market-sized size with as few interfaces as possible. The shredding of the lettuce leaves with as few interfaces as possible strives on the one hand to be able to offer the consumer relatively large and strong pieces of lettuce; it is then up to the consumer to further shred the pieces of lettuce according to their own needs and tastes. On the other hand, it should be borne in mind that many cuts reduce the nutritional value and promote the susceptibility of the lettuce to faster browning. It is very important not to reduce the quality of the shredding process unnecessarily, is a fiber-friendly cutting technique to be provided: The bacterial browning develops more virulently over the entire product, the coarser the fiber damage at the interfaces. Therefore, the postulate to use a cutting technique that is gentle on the fibers is certainly justified. This can be achieved, for example, by continuously focusing on maintaining a sharp cutting edge when using knives. In systems with large throughputs, the use of other cutting agents can be easily imagined, which have a self-regenerating effect with regard to the cutting quality. Here, for example, the use of high-pressure water cutters should be considered, or the use of lasers. Regardless of the method by which the salads are crushed, the final purpose of this operation is always to avoid, if necessary to minimize, fiber damage to the product at the interfaces.

This first operation is preferably carried out in the immediate area of a continuously flowing water flushing channel. This has the advantage that the sliced lettuce, in particular its interfaces, come immediately into contact with water as the washing medium. Moreover, such a precaution is taken to ensure that the cut lettuce is transported to the subsequent process steps in a water channel, which prevents mechanical stress on this sensitive good. The transport water is largely recirculated to minimize water consumption. Regeneration of the same is initiated as required. In terms of temperature, the water is uncooled, so that an average temperature of around 15 ° C can be expected.

The water rinsing channel opens into wash basins with continuous flow of water, in which the actual one The process of washing the lettuce takes place, ie the lettuce is exposed to this water flow for a few seconds to several minutes. This wash water is preferably treated beforehand with antibacteriology and enriched with 0.03-0.40% pure hydrogen peroxide (H ₂ O ₂ ). If this hydrogen peroxide is introduced in a dilute composition, its percentage increases according to the composition of the diluted solution. This water / H2θ2 medium as an aqueous solution has an antibacterial effect on the water and the products in such a way that the chemical degradation processes in the lettuce, which occur particularly quickly at the fiber separations, i.e. in the cutting area, are inhibited. The degradation processes of vegetable substances initially show up as browning, which then quickly turns into a putrefaction process. A distinction is made between an enzymatic browning, which comes from an enzymatic-catalytic oxidation (polymeric browning), and a bacterial browning. The polymeric tanning is harmless in itself. The browning caused by bacteria, on the other hand, has a far more negative effect on the quality of the products, which is why the hydrogen peroxide used primarily counteracts this. In this context, the great importance of a qualitative shredding process of the products should be pointed out again, because the bacterial-induced browning arises the more virulent the coarser the fiber damage at the interfaces. Other essential parameters during this disinfection phase are the following:

- the material consistency of the respective product;

- the size of the cut surfaces;

- the percentage of hydrogen peroxide as a manufacturing aid;

- the temperature and quality of the wash water during the treatment phase; - the washing time of the products.

On the one hand it is important to minimize the theoretical vppm values from the use of hydrogen peroxide, on the other hand to keep the duration of treatment and the temperature of the washing medium low. In general, it has been proven that a long duration of treatment, coupled with a relatively high temperature of the washing medium, tends to soften the product. On the other hand, it is advantageous to choose a lower percentage of hydrogen peroxide, but to increase the treatment time.

From these explanations it is imperative that for each product there is an optimal design with regard to hydrogen peroxide concentration, temperature and washing time.

For a tender lettuce with only one cut in the area of the growth stem, it will be sufficient to select a proportion of 0.03% pure hydrogen peroxide and to treat this salad for about 30 seconds at a water temperature of about 15 ° C. If, on the other hand, roughly cut carrots are to be treated, for example, a larger proportion of hydrogen peroxide will be used due to the larger cut surfaces and the strong fibrous consistency of this type of vegetable; In addition, the exposure time, i.e. the washing time, will have to be increased accordingly, and depending on the degree of ripeness of the vegetable type, a washing time of up to several minutes will have to be provided. In this constellation too, the wash water will preferably be uncooled, that is to say approximately 15 ° C. For most large-leafed types of lettuce with several cuts per leaf, a hydrogen peroxide content of 0.15% is preferred, nothing needs to be changed at the water temperature, and the washing time is limited to 20-60 seconds. With a hydrogen peroxide content of less than 0.03%, a water temperature with low values, below 5 ° C, and an exposure time of less than 10 seconds, there is no guarantee that the desired specific effect of the manufacturing aid mentioned on the salad will be achieved in the smallest possible range. At these values, the exposed cells in the section plane are not satisfactorily disinfected, so that the desired durability cannot be achieved.

Of course, when determining the hydrogen peroxide concentration, it must be taken into account that the cleavage or the degradation of this substance adhering to the products must be complete by the subsequent process steps. Therefore, as already explained above, one will operate with a lower hydrogen peroxide concentration and instead increase the exposure time.

Hydrogen peroxide concentrations of over 0.40% at a water temperature of approx. 15 ° C and with an exposure or Washing times of up to 10 minutes will only be used for a few fresh agricultural products, because with these specifications there is a general risk that the products, in particular the well-known types of lettuce, are softened too much and that the cleavage or the breakdown of the hydrogen peroxide fractions during the subsequent process steps is no longer guaranteed.

The goods are first transported in the already mentioned water channel to a first wash basin, in which air injection nozzles are provided to support the washing process for extensive sedimentation of adhering earth, adhering sand, etc. This is followed by a multi-stage Sink system in the cascade principle with the supply of antibacterially treated fresh water, which is enriched with a low-percentage hydrogen peroxide concentration. The treated fresh water for maintaining the washing process is preferably entered by means of a spray device at the end of the washing system, in order to ensure a uniform hydrogen peroxide consistency of the washing water and to be able to rinse the product again with freshly treated water at the end of the washing process. By subjecting the products to a gentle washing process using a cascade principle of small conveyor belts, the mechanical stress on them is minimized by such a mode of transport.

After the washing process, the goods are transferred directly to the belt of a pre-drying stage. This pre-drying stage consists, for example, of a vibrating table, where most of the water adhering to the goods is gently removed. A multi-stage run is preferably provided. A perforated plate as a conveyor track ensures an optimal separation between water and material. Here, too, the goods are transferred directly and continuously to the next level. Optionally, especially with small-sized material that could get caught in the perforated plate, other means will have to be used for the purpose of water separation, for example centrifuges.

Of course, it is also possible to design this predrying stage from a combination of different agents.

If necessary, the product can be sprayed with enriched water (hydrogen peroxide) before the subsequent thermally processed drying stage, which has a cleaning effect and is also used to do that To create conditions for an even drying process.

The next stage to be passed through by the good is a tempered drying stage, which consists of a warm air tunnel, in which air nozzle sticks act for regular circulation of the air around the good. The effect emanating from these nozzle assemblies ensures a gentle, integral flow around the product on the drying belt in order to completely evaporate the water droplets still adhering on all sides. The prevailing temperature should be between 20 - 45 ° C, preferably around 25-30 ° C. In order to ensure the greatest possible germ-free atmosphere, the incoming air is preferably treated with UV rays after a previous antibacterial treatment. Moist, saturated air is continuously extracted from the tunnel, then regenerated accordingly in a closed circuit, and then returned to the tunnel. The treatment time of the goods in this tunnel is 20 seconds to 2 minutes. amount, depending on the type of salad. On the one hand, the temperature in the tunnel must be set in such a way that a drying process takes place; on the other hand, the temperature prevailing here should not be too high so that the cells of the product cannot be destroyed by drying out. It is optimal if the surface of the product no longer has any water droplets after it has passed this stage, but is still covered with a fine film of moisture.

Both the pre-drying stage and, in particular, the temperature-controlled drying stage ensure that the hydrogen peroxide fractions are completely removed from the aqueous solution or. they can split into oxygen (oxygen radicals) and water, which forms the temperature-controlled drying stage. So they have Portions of hydrogen peroxide converted into natural, harmless elements or molecular compounds. As will be explained in more detail below, the degradation of this substance is reinforced by other factors. It is important that the above-mentioned extraction of the air saturated with moisture takes place efficiently from the tunnel. Of course, this exhaust air can be subjected to an antibacterial treatment in a closed circuit, where it is also dried, before being re-used. Subsequently, as already explained above, it is reintroduced into the process via the aforementioned air nozzle sticks. An additional disinfection and antibacterial treatment of this air can be achieved with UV radiation that is arranged accordingly.

With regard to the enrichment of the washing water with a minimal amount of hydrogen peroxide, the following considerations are important:

Hydrogen peroxide first develops its direct effect by disinfecting the carrier medium (here water) and then by splitting it into water and oxygen (oxygen radicals), whereby the main focus is on the split oxygen (oxygen radicals). This cleavage of the hydrogen peroxide occurs first of all due to the natural instability of this substance, furthermore because the present process accelerates such a cleavage (drying stages). In addition, it should not go unmentioned that hydrogen peroxide is exposed to a natural catalase, which degrades or. Cleavage of this substance has a positive effect. With regard to the chemical processes involved in catalase within plant tissues, reference is made to the relevant literature. The method proposed here has the following advantages over the conventional methods for treating a salad with the substances commonly used:

a) First of all, an innocuous substance is used as a manufacturing aid in the form of an additive, which substance is used in various ways in the food industry.

b) The initial concentration of hydrogen peroxide is kept to a minimum.

c) The drying stages allow the residual moisture on the product to approach zero: the theoretically possible vppm concentration of hydrogen peroxide is correspondingly reduced.

d) The natural degradation, respectively. Cleavage of the hydrogen peroxide results from the internal instability of this substance, furthermore from the cleavage process of the substance caused by the process (drying stages) and finally from the catalase that occurs in the product, in such a way that at the end there is a product before packaging that contains a has no longer measurable concentration of hydrogen peroxide.

As far as the oxidizing effect of oxygen (oxygen radicals) is concerned, it must be said that it is directed against the formation of enzymatic browning on the product. This microbicidal effect is not disturbed by any other accompanying substances, because on the one hand great care is taken in the harvest and in the subsequent preparation steps of the product, and on the other hand in that the wash water is treated as antibacterially as possible before use. The tempered drying stage is then followed by a colder stage, which in itself has the same structure as the warm air tunnel. However, the temperature prevailing here is between 0-10 ° C, preferably 1-6 ° C. During this phase, 20 seconds to 2 minutes, the product is subjected to a slight cooling and, if a residual moisture from the previous step should still adhere to the product, further drying. The complete drying of the lettuce is a condition that practically no condensed water can form in the packaging bags.

The considerations made under the temperature-controlled drying stage with regard to antibacterial treatment of the air and regeneration of the exhaust air also apply to the latter process step.

The two tunnels can be connected to each other by means of uniform funding, or they can also be characterized by individual band funding. In both cases, the goods will go through the above-mentioned stages in regular cadence. The different temperature ranges are separated by structural measures which are able to minimize the energy consumption for the warm and cold atmosphere.

After the colder stage, the goods are transported on a conveyor belt into a cooled room, where they are portioned by weight at room temperatures between 0 - 10 ° C (for example using a multihead weigher) and packaged. This space is also preferably kept as germ-free as possible by various measures. It is important that the goods are not subjected to any mechanical loads during their entire passage through the various stages, so that they are carried on gently.

Of course, it is also possible for the goods to remain completely shielded from the ambient atmosphere from the washing process to the finished packaging, which can happen because the individual process steps work in closed cells at excess pressure.

The above-described packaging of the goods in bags in the largest possible germ-free space is increased by at least one further measure in order to maximize the sterility of the product: During the packaging process, the bags are continuously rinsed out with slightly cooled nitrogen so that they are only packed and sealed contain an extremely diluted proportion of air.

The goods are also packaged using suitable bags: in order to maximize durability, it is preferred to use bags whose material ensures impermeability to gases.

In summary, it should be ensured that the oxygen released during the splitting of hydrogen peroxide (oxygen radicals), the oxidation of which triggers the disinfecting effect on the surface of the goods, therefore significantly increases the shelf life of the product, not directly due to a new uncontrolled chemical process Force is set.

It is also important to ensure that the treatment of the products, especially during the cold drying stage and packaging, is carried out at temperatures between 0 - 10 ° C becomes. Below 0 ° C, the product suffers a falsification of its natural properties due to ice-crystalline cell destruction, above 10 ° C there is a concrete reduction in its shelf life.

Claims

claims

1.Procedure for increasing the shelf life of agricultural products, the products to be processed after harvesting being processed essentially in line with the market, subjected to at least one washing process aimed at increasing the shelf life of the products, then dried and then packaged, characterized in that at least the water is enriched with a hydrogen peroxide for the final washing treatment.

2. The method according to claim 1, characterized in that the water is enriched with a proportion of 0.03-0.40% pure hydrogen peroxide.

3. The method according to claim 1, characterized in that the final washing treatment process is carried out prior to the introduction of the products into a thermally processed drying stage.

4. The method according to claims 1-3, characterized in that the final washing treatment process is carried out by spraying the products.

5. The method according to claim 1, characterized in that after the washing process, the products pass through at least one mechanical predrying stage aimed at maximizing the separation of the water, that the products are then passed through at least one temperature-controlled drying stage, in which they reach up to a moisture film is dried, that the products are further passed through at least one colder stage downstream of the temperature-controlled drying stage, and that the products are then packaged in bags.

A method according to claim 5, characterized in that the products the washing process at room temperature for 10 sec. To 10 min. run through that the mechanical predrying stage takes place at room temperature, that the products pass the tempered drying stage at a temperature of 20-45 degrees C for 20 sec. to 2 min. and the colder stage at a temperature of 0-10 degrees C for 20 seconds to 2 minutes. and that the products are packed in gas-tight bags at a temperature of 0-10 degrees C.

A method according to claim 5, characterized in that at least the tempered drying stage e and / or the downstream colder stage are flowed through with an antibacterially treated and dried air, and that this air is continuously sucked out, regenerated and back there via a closed circuit is initiated.

A method according to claim 7, characterized in that the quality of the antibacterially treated and dried air is increased with UV rays.

A method according to claim 5, characterized in that one or more process steps is carried out in an antibacterial treated atmosphere, closed from the environment.

10. The method according to claim 5, characterized in that during the packaging, the bags are continuously flushed out with nitrogen, in such a way that the bags contain a minimized amount of air in the packaged and closed state.

11. The method according to claim 10, characterized in that the nitrogen is used in the packaging at a temperature of 0-10 degrees C.

12. The method according to claim 1, characterized in that the products are cut by means of a mechanical cutting edge, by means of laser beams or by means of a liquid, quasi-liquid medium under pressure.