Process for decontamination and microbiological stabilisation of liquid egg white stored at room temperature

Abstract

A process 100 for the decontamination and microbiological stabilisation of liquid egg white stored at room temperature, comprising the operating steps of: preparing the egg white in a liquid state; carrying out a first thermal treatment 110 by carrying out a first and a second sub-step for heating to specific temperature ranges and for specific time intervals in order to eliminate part of the microorganisms present in the egg white and activate any spores present; incubating 130 the egg white at a pre-established temperature and for a specific incubation time interval for the germination of any spores present; carrying out a second thermal treatment 140 on the egg white equivalent to the first to eliminate the spore-derived bacteria; carrying out an isothermal treatment 160 of the egg white to eliminate the bacteria present in the egg white that were not eliminated by the second thermal treatment; carrying out a third thermal treatment 170 similar to the aforesaid first and second thermal treatment in order to eliminate the bacteria present in the egg white that were not eliminated by said first and second thermal treatments.

Description

[0001] “PROCESS FOR DECONTAMINATION AND MICROBIOLOGICAL STABILISATION OF LIQUID EGG WHITE STORED AT ROOM TEMPERATURE”

[0002] DESCRIPTION

[0003] * * * * *

[0004] Technical field

[0005] The present invention relates to the technical field of egg products and, more specifically, to the technical field of the preservation and storage of easily perishable foodstuffs such as, precisely, egg products.

[0006] In particular, the invention relates to a process for the decontamination and microbiological stabilisation of liquid egg white that can be stored at room temperature.

[0007] * * * * *

[0008] Prior art

[0009] To date, industrial plants for the production and packaging of liquid egg white envisage applying different thermal treatment steps in order to minimise risks to consumer health, in particular thermal pasteurisation processes under lethal conditions for the pathogens normally present in eggs. In fact, as is known, food products have different microorganisms, such as bacteria in vegetative form, fungi and yeasts, which in the case of poor storage of the aforesaid food products can proliferate, develop and then be pathogenic to end consumers.

[0010] Generally, the most widely used thermal treatment process is that of pasteurisation which, in brief, involves heating the product for a pre-established time interval and at a pre-established temperature value in order to allow the elimination of most of the microorganisms that may be present, in particular pathogenic bacteria. Furthermore, the pasteurisation process occurs at temperatures lower than those that would result in the denaturation of the egg white proteins, so as to preserve the organoleptic characteristics thereof. However, in order to ensure the elimination of some extremely dangerous pathogenic bacteria, such as salmonella, the pasteurisation process is usually carried out under limit conditions such as to cause some protein denaturation with the consequent compromise of the chemical-physical properties of the egg product.

[0011] This means that the egg white thermally treated by means of pasteurisation will be free of pathogenic microorganisms, but still populated by heat-resistant microorganisms that contribute to the sensory deterioration of the product. Therefore, the egg white thermally-treated by means of pasteurisation must necessarily be introduced within what is known as the "cold chain" to ensure its correct storage in chillers set at temperatures below 5°C. The cold chain, therefore, will lead to an increase in the difficulty of transport and storage, as well as the relative final costs of the product.

[0012] In addition, not being totally free of heat-resistant microorganisms, the shelf life of the liquid egg white is limited to a few weeks after its packaging, as long as it is stored correctly.

[0013] In the case of egg white and egg products, unlike milk, it is not possible to carry out sterilisation processes at temperatures such as to ensure the total elimination of pathogenic and heat-resistant microorganisms for the aforesaid preservation of the organoleptic characteristics.

[0014] * * * * *

[0015] Summary

[0016] In this context, the technical task underlying the present invention is to propose a process for the stabilisation of liquid egg white at room temperature which obviates the drawbacks of the prior art as mentioned above.

[0017] In particular, an object of the present invention is to provide a process for the stabilisation of liquid egg white at room temperature such as to ensure an increase in the shelf life of the liquid egg white.

[0018] Another object of the present invention is to provide a process for the stabilisation of liquid egg white at room temperature which allows a reduction in consumption and, therefore, in overall production costs. Therefore, specifically, the invention pursues the object of eliminating the use of what is known as the "cold chain" which, to date, is essential in order to ensure the correct storage and consumption of liquid egg white produced with the known processes.

[0019] A further object of the present invention is to provide a process for the stabilisation of liquid egg white at room temperature which allows carrying out less costly packaging, in economic and practical terms, than the packaging with an aseptic packaging machine.

[0020] The stated technical task and specified objects are substantially achieved by a process for decontamination and microbiological stabilisation of liquid egg white stored at room temperature, which comprises the technical characteristics as set out in the independent claim. The dependent claims correspond to further advantageous aspects of the invention.

[0021] It should be noted that this summary introduces, in simplified form, a selection of concepts which will be further elaborated on in the detailed description provided below. The invention relates to a process for decontamination and microbiological stabilisation of liquid egg white stored at room temperature comprising the following operating steps: preparing a pre-established amount of liquid egg white; carrying out a first thermal treatment on the egg white in order to eliminate part of the microorganisms present in the egg white and activate the germination of the spores; incubating the egg white at a temperature value between 30 and 40 °C for a time interval of between 16 and 26 hours for the germination of the spores and, furthermore, for the resumption of bacterial growth; carrying out a second thermal treatment on the egg white equivalent to the first thermal treatment to eliminate the spore-derived bacteria present in the egg white and which have resumed vital activity; carrying out an isothermal treatment at a temperature between 42 and 52 °C for a time interval of the isothermal treatment between 7 and 17 hours to eliminate the bacteria present in the egg white that were not eliminated by the second thermal treatment; carrying out a third thermal treatment on the egg white in order to eliminate the resistant bacteria present in the egg white that were not eliminated by the first and second thermal treatments. preferably but not necessarily, carrying out packaging at temperatures between 48 °C and 58 °C. In detail, each thermal treatment step consists of two distinct heating operations: a first heating and a second heating.

[0022] In relation to the first and second thermal treatment steps, the first heating operation is carried out at a temperature value between 52 and 58 °C and, furthermore, for a time interval of less than 300 seconds. The second heating operation, in relation to the first and second thermal treatment steps, is carried out at a temperature value between 59 and 62 °C and, furthermore, for a time interval of less than 40 seconds.

[0023] In contrast, the first heating operation of the third thermal treatment step is carried out at a temperature value between 50 and 55 °C and, furthermore, for a time interval of less than 300 seconds. The second heating operation is instead carried out at a temperature value between 53 and 58 °C for a time interval of less than 40 seconds. Thereby, the stabilisation process just described is advantageously capable of allowing the preparation of stable liquid egg white at room temperature, i.e., liquid egg white that can be stored at room temperature avoiding the use of the "cold chain" and, furthermore, without the development of pathogenic microorganisms therein, as they are absent.

[0024] Therefore, the term "stabilisation" refers to the biochemical conditions of the egg white and its organoleptic components. A completely sterilised liquid egg white, i.e., free of pathogenic microorganisms or other heat-resistant microorganisms, maintained at room temperature is able to remain stable at the microbial level and, therefore, not evolve into a harmful product and / or altered in its nutritional and / or organoleptic characteristics.

[0025] Even more advantageously, the aforesaid process allows avoiding blowing carbon dioxide before the packaging step. In fact, the egg white sterilisation processes known in the state of the art require the aforesaid step of blowing carbon dioxide which, as a possible inconvenience, could present an alteration of the pH of the egg white and, therefore, a possible alteration of the functionality of the enzymes present therein and of the colour of the product.

[0026] In general, the aforesaid process does not envisage the addition of any type of additive to the thermally-treated product, i.e., egg white.

[0027] The aforesaid advantages are mainly obtained thanks to the alternation between the thermal treatment steps and the physical-biochemical treatment steps (i.e., incubation and isothermal treatment). The thermal treatments, in particular the second heating steps, are carried out with a bacterial abatement technology that does not affect the main functional properties of the egg white, while the physical-biochemical treatments contribute to the improvement of the microbial stability of the product. ★ ★ ★ ★ ★

[0028] Brief description of the drawings

[0029] Further characteristics and advantages of the present invention will become more apparent from the indicative and thus non-limiting description of a preferred, but not exclusive, embodiment of a process for the stabilisation of liquid egg white at room temperature, as illustrated in Figure 1 which, according to a schematic view, illustrates a process for the stabilisation of liquid egg white at room temperature.

[0030] With reference to the drawings, they serve solely to illustrate embodiments of the invention with the aim of better clarifying, in combination with the description, the inventive principles at the basis of the invention.

[0031] * * * * *

[0032] Detailed description of at least one embodiment

[0033] The present invention relates to a process for the stabilisation of liquid egg white at room temperature which, with reference to the figures, has been generally indicated with the number 100.

[0034] Any modifications or variants which, in the light of the description, should be evident to the person skilled in the art must be considered as falling within the scope of protection established by the present invention, according to considerations of technical equivalence.

[0035] Figure 1 shows a process 100 for the stabilisation of liquid egg white at room temperature.

[0036] In accordance with a preferred but not necessary aspect of the invention, the process 100 comprises the preliminary steps of preparing a pre-established amount of eggs 101 ; shelling the eggs and separating the egg white from the yolks 103 in order to obtain an amount of egg white having a yolk contamination of less than 0.2% by weight. Preferably, the raw liquid egg white exiting the sheller is filtered to be collected in a special storage tank.

[0037] Even more preferably, the process 100 envisages carrying out a preliminary cooling 105 of the raw egg white to a temperature below 5 °C, preferably below 4 °C, and maintained at that temperature in a homogeneous manner with the use of a mechanical stirrer positioned in the same refrigerated storage tank. In accordance with the invention, the process 100 comprises the following operating steps: preparing a pre-established amount of liquid egg white; carrying out a first thermal treatment 1 10; incubating the thermally-treated egg white 130; carrying out a second thermal treatment 140; carrying out an isothermal treatment of the egg white 160; carrying out a third thermal treatment 170.

[0038] The step of carrying out the first thermal treatment 110 of the liquid egg white has the purpose of eliminating part of the microorganisms naturally present in the same egg white and, at the same time, activating the development of any spores present. In detail, the first thermal treatment 1 10 comprises, in turn, a first heating step at a temperature between 52 and 58 °C for a time interval of less than 300 seconds and, further, a second heating step at a temperature between 59 and 62 °C for a time interval of less than 40 seconds.

[0039] The incubation step 130 of the egg white instead has the purpose of promoting the germination of the spores. In detail, the incubation step 130 envisages conveying the thermally-treated egg white into a collection tank to store it at an ideal temperature value for bacterial proliferation, preferably between 30 and 40 °C, and for a time interval between 16 and 26 hours. Advantageously, thereby, the germinated spores will be more sensitive and can be easily eliminated with the subsequent thermal treatments described in relation to the present process 100.

[0040] The step of carrying out the second thermal treatment 140 has the purpose of eliminating the bacteria present in the egg white, in particular the bacteria deriving from the spores germinated with the incubation step 130. In detail, the second thermal treatment 140 is similar to the first thermal treatment 1 10 and, therefore, comprises a first heating step at a temperature between 52 and 58 °C for a time interval of less than 300 seconds and, further, a second heating step at a temperature between 59 and 62 °C for a time interval of less than 40 seconds.

[0041] The step of carrying out an isothermal treatment 160 of the egg white has the purpose of eliminating the most resistant bacteria that had not been eliminated during the previous thermal treatments 1 10, 140, in particular in the second thermal treatment 140. In detail, the isothermal treatment 160 of the egg white is carried out at a temperature between 42 °C and 52 °C and, further, for an isothermal treatment time interval between 7 hours and 17 hours.

[0042] The step of carrying out the third thermal treatment 170 of the egg white has the purpose of eliminating the residual bacteria in the egg white not eliminated during the first and second thermal treatments 110, 140. In detail, similar to the first and second thermal treatments 110, 140, the third thermal treatment 170 comprises a first heating step at a temperature value between 50 and 55 °C for a time interval of less than 300 seconds and, further, carrying out a second heating at a temperature value between 53 and 58 °C for a time interval of less than 40 seconds. In addition, the third thermal treatment 170 is advantageously capable of maintaining the egg white at an optimal temperature for carrying out a possible subsequent hot filling step.

[0043] Thereby, the above-described stabilisation process is advantageously capable of allowing the preparation of liquid egg white stable at room temperature, i.e., liquid egg white having an optimal microbiotic stability to the extent that it does not necessarily have to be stored in refrigerators at temperatures below 5 °C.

[0044] In particular, the incubation 130 and isothermal treatment 160 steps can be defined as physical-biochemical processes that have two main purposes to contribute to the final objective of germinating and eliminating heat-resistant microorganisms from the egg white. The first aim is to restart bacterial growth following a corresponding thermal treatment. The second aim is instead to lower the protective functionality related to bacterial cell walls by means of the involvement of enhanced biochemical reactions associated with some bioactive proteins such as lysozyme. In fact, lysozyme is an enzyme provided with bactericidal activity and naturally present in egg products.

[0045] Advantageously, therefore, the particular combination of the operating steps of the process 100, in addition to actively eliminating part of the pathogenic microorganisms present in the egg white, allows increasing the bactericidal efficacy of the lysozyme and other similar enzymes present, thus determining optimal operating conditions for such enzymes, such as, for example, the weakening of the bacterial cell walls and / or increasing the mobility of the enzymes in the egg white. In fact, the process 100 in accordance with the invention is also able to fluidise the treated egg white so as to make the distribution of the lysozyme more homogeneous, which is therefore more free to act against any bacteria.

[0046] Thereby, moreover, the process 100 does not need to blow any gases such as carbon dioxide inside the egg white, before its packaging, to ensure microbiotic stability. Furthermore, carbon dioxide would result in the modification of the pH of the egg white and, therefore, a negative alteration of the enzymatic activity and of the colour of the product.

[0047] In accordance with an aspect of the invention, each of the first heating steps is carried out with one or more heat exchangers, of the direct and / or indirect type.

[0048] For example, the heat exchangers can be plate-type ("PHE") or tubular, single or multiple ("THE" or "m-THE").

[0049] That is, the first heating steps are based on the thermodynamic properties of the fluids and on their heat exchange capacity, in particular the exchange of thermal energy by conduction and convection between the liquid egg white and the fluids present in the heat exchangers in direct or indirect contact with the conveying pipeline of the liquid egg white.

[0050] In accordance with another aspect of the invention, each of the second heating steps is carried out with a direct electromagnetic heating device such as, for example, ohmic heating, radiofrequency, microwaves, preferably a pulsed ohmic heating device.

[0051] Advantageously, the use of a pulsed ohmic heating device allows, in this process, to heat the egg white up to 59° / 62° C.

[0052] Preferably, each electromagnetic heating device is configured to operate under a hyperbaric condition in which the pressure to which the egg white is subjected is lower than 45 bar.

[0053] Even more preferably, the thermal treatment carried out by each electromagnetic heating device is carried out with the aid of the rise in temperature (due, in fact, to the aforesaid electromagnetic heating device, preferably pulsed ohmic) and to an overpressure condition at a value between 6 and 32 bar.

[0054] That is, the second heating steps are based on the electrical resistance capacity of the liquid egg white which, in detail, is heated by the application of an external electric field to the conduit along which it is flowed. Direct electromagnetic heating, for example ohmic heating, is also defined as "volumetric heating" as it is capable of acting very quickly (i.e., with times less than one second) and homogeneously on the entire section of liquid egg white conveyed through the aforesaid external electric field.

[0055] Advantageously, volumetric heating is capable of performing a more effective bacterial abatement with respect to that achieved with the first heating steps, i.e., with the heat exchangers. Even more advantageously, volumetric heating is also capable of not affecting the main functional properties of the egg white.

[0056] In accordance with an aspect of the invention, the process 100 envisages conveying the egg white with high-pressure pumps towards the portions of the treatment plant in which each step of the first thermal treatment occurs.

[0057] Preferably, the aforesaid pumps are configured to operate at pressure values higher than a few bar units up to values equal to many tens of bar, but lower than 45 bar.

[0058] In accordance with an aspect of the invention, the aforesaid conveying step can be delegated to one or more positive displacement pumps present in the corresponding egg white treatment plant in order to inject the product, i.e., the egg white, into the treatment circuit at a pressure having any value lower than 45 bar.

[0059] In accordance with another aspect of the invention, a positive displacement pump is preferably arranged downstream at least of the apparatus for incubating the egg white, for example a plate ascending-heat recovery apparatus, so as to inject the egg white under pressure towards the apparatus configured to carry out the second thermal treatment.

[0060] In accordance with an aspect of the invention, the process 100 comprises a first and a second cooling step 120, 150 carried out, respectively, before the incubation step 130 and the isothermal treatment step 160. In particular, each cooling step 120, 150 is carried out with heat exchangers.

[0061] Thereby, each cooling step 120, 150 allows cooling the liquid egg white to a temperature value suitable for carrying out the corresponding and subsequent thermal and biochemical treatment step, i.e. the incubation step 130 in one case and the isothermal treatment step 160 in the other case.

[0062] Preferably, following each second heating step ("direct electromagnetic heating"), the liquid egg white is kept in a storage cell for a defined time, which is followed by a rapid cooling step by means of a heat exchanger. Subsequently, the cooled liquid egg white is conveyed to a section of the plant used for heat regeneration and cooling by means of a plate heat exchanger. In accordance with a preferred aspect of the invention, the process also comprises a hot filling step 180 carried out after the third thermal treatment 170 so as to eliminate any residual bacteria following the previous thermal treatment steps. In particular, the hot filling step 180 envisages conveying and packaging the egg white while maintaining it at a temperature between 48 and 58 °C. Advantageously, thanks to the aforesaid operating temperatures, the hot filling step 180 is also able to limit the possible recontamination of the egg white.

Claims

CLAIMS1. A process for the decontamination and microbiological stabilisation of liquid egg white stored at room temperature, comprising the operating steps of: preparing a pre-established amount of egg white in a liquid state; carrying out a first thermal treatment on the egg white, comprising the following steps• carrying out a first heating to a temperature value between 52 °C and 58 °C for a time interval of less than 300 seconds,• carrying out a second heating to a temperature value between 59 °C and 62 °C for a time interval of less than 40 seconds, in order to eliminate part of the microorganisms present in the egg white and activate any spores present; incubating the egg white at a temperature value between 30 °C and 40 °C for a time interval of between 16 hours and 26 hours for the germination of any spores present; carrying out a second thermal treatment on the egg white equivalent to said first thermal treatment to eliminate the spore-derived bacteria present in the egg white; carrying out an isothermal treatment at a temperature between 42 °C and 52 °C for a time interval of the isothermal treatment between 7 hours and 17 hours to eliminate the bacteria present in the egg white that were not eliminated by said second thermal treatment; carrying out a third thermal treatment on the egg white comprising the following steps:• carrying out a first heating at a temperature value between 50 °C and 55°C for a time interval of less than 300 seconds,• carrying out a second heating at a temperature value between 53 °C and 58 °C for a time interval of less than 40 seconds, in order to eliminate the bacteria present in the egg white that were not eliminated by said first and second thermal treatments.

2. The process in accordance with claim 1 , wherein each of said second heating steps is carried out with a direct electromagnetic heating device.

3. The process in accordance with claim 2, wherein each of said second heatingsteps is carried out with a pulsed ohmic heating device.

4. The process in accordance with claim 1 or 2, wherein each direct electromagnetic heating device is configured to operate under a hyperbaric condition in which the pressure to which the egg white is subjected is lower than 45 bar, preferably between 6 and 32 bar.

5. The process in accordance with any one of the preceding claims, comprising a hot filling step carried out after said third thermal treatment to eliminate any residual bacteria, wherein said hot filling step provides for keeping the egg white at a temperature between 48 °C and 58 °C.

6. The process in accordance with any one of the preceding claims, wherein each of said second heating steps is carried out with one or more heat exchangers of the direct and / or indirect type.

7. The process in accordance with any one of the preceding claims, wherein the egg white to be thermally treated during each first thermal treatment step is conveyed by means of high-pressure pumps.

8. The process in accordance with any one of the preceding claims, comprising a first and a second cooling step carried out, respectively, before said incubation step and said isothermal treatment step, each cooling step being carried out with heat exchangers.

9. The process in accordance with any one of the preceding claims, comprising the preliminary steps of removing the shells of a pre-established amount of eggs; separating the egg whites from the yolks in order to obtain an amount of egg white having a yolk contamination of less than 0.2% by weight.

10. The process in accordance with claim 9, comprising a step of cooling said amount of egg white to a temperature of less than 5 °C.

Images