Refrigerated processed foods that can be stored for a long period of time and a method for storing the same

Abstract

A shelf-stable refrigerated processed food (REPFED) having a pH value of at least 4.6, wherein the REPFED at a temperature between 0° C. and 10° C. is free of vegetative Listeria monocytogenes and / or Streptococcus faecalis and / or Clostridium botulinum and Bacillus cereus, and wherein these bacteria are killed and the spores of these bacteria are at least fatally damaged and are no longer capable of developing and growing into the bacteria. Also disclosed is a method (1) for preserving said REPFED stored in a refrigerator.

Description

[Background technology]

[0001] The present invention relates to fresh foods, also known as "long-term refrigerated processed foods", and to a method for preserving fresh foods stored in a refrigerator.

[0002] Various methods are known for preserving perishable foods and extending their shelf life.

[0003] Fresh foods are understood to include refrigerated foods, also called "refrigerated shelf-stable processed foods (REPFED)" that are produced on an industrial scale. The term REPFED is a commonly known term in the scientific literature and, for the purposes of this specification, fresh foods and REPFED can be considered synonymous.

[0004] The scientific paper "Occurrence, diversity and characteristics of spores of psychrotolerant spore-forming bacteria in different REPFEDs produced in Belgium" published in 2014 by S. Samapundo et al. revealed known problems with microorganisms and their spores in REPFEDs. The microbiological shelf life of REFPED is determined by European legislation, which sets out legal standards regarding the presence and quantity of certain microorganisms.

[0005] European law provides that:

[0006] Generally, the concentration of Bacillus cereus is 10 5 It is considered unacceptable to exceed CFU / g (spores or cells) (Langeveld et al., 1996) because outbreak evaluations in animals and humans and volunteer studies have shown that 10 5It has been shown that B. cereus can cause food poisoning at CFU / g and that such an increase in the number of B. cereus does not comply with the principles of Good Manufacturing Practice (GMP / GHP) (Notermans et al., 1997; Lund et al., 2000). Therefore, in this study, 10 5 All products with more than 10 CFU / g were recognized as posing a risk to human health. However, a distinction was made between cells and spores. 5 Even if the spores are present in the food, pasteurization reduces the concentration to 10 5 If the number falls below spores / g, there is no risk if storage temperatures are maintained adequately. However, if the number falls below 10 5 There is a risk if spores are present at a concentration of 10 / g. Spores pass through the stomach more easily than vegetative cells, then germinate and colonize the intestine, producing enterotoxins. With cells the situation is different. If 10 5 When 10 cells / g are present, degradation toxins can be produced, which are heat-stable and therefore remain present even after pasteurization (Rajkovic et al., 2008). 5 Spores / g are not considered a risk. However, the final product (on the market) is considered a risk. Furthermore, 10 5 vegetative cells / g are considered at risk at any stage (manufacturing or distribution) due to the potential production of degradation toxins. The exact shelf life of REPFED is determined by a criterion of approximately 100,000 colony forming units of pathogens such as Listeria monocytogenes, Streptococcus faecalis, and / or psychrophilic nonproteolytic Clostridium botulinum.

[0007] In addition to the aforementioned pathogens, REPFED frequently contains spores of Bacillus cereus, and such REPFED is generally known to pose a risk to consumer health. More specifically, psychrophilic strains of Bacillus cereus are increasingly found in REPFED. Such psychrophilic strains of Bacillus cereus can grow at temperatures above 6°C, and therefore can grow in refrigerators. The optimal growth temperature of psychrophilic strains of Bacillus cereus and their spores is between 30°C and 37°C, and they can grow at pH values ​​between 4.9 and 9.0, with an optimal pH value of 6.0 to 7.0.

[0008] When B. cereus spores develop into the bacteria themselves, B. cereus can cause foodborne infections and food poisoning in consumers.

[0009] Below are some methods used to store the REPFED mentioned above.

[0010] Known preservation methods are based on mild heat treatments applied during the production of REPFED, which serve to inactivate vegetative bacteria in REPFED.

[0011] Foods with a pH value above 4.5 are usually pasteurized in the food industry. During this process, fresh foods are heated intensely and vegetative microorganisms and their spores are killed. Pasteurization is carried out at about 121.1 °C, while ultra-high temperature pasteurization (UHT pasteurization) is carried out by heating for a short period (a few seconds) at about 140 °C. Such foods are usually packaged in cans and stored at room temperature, so they have a very long shelf life. However, the quality of these foods is significantly deteriorated, so many of them are not suitable for pasteurization.

[0012] On the other hand, there are known methods of pasteurization of food, with a maximum pH value of 4.5, where the food is heated for a short time. Pasteurization is a process in the food industry that kills nutrient bacteria in food by heating the food for a short time, without significantly changing the food molecularly and structurally. Foods that cannot be sterilized at pH values ​​above 4.5 are first lowered by adding additives. Such additives can be acids. One example is hummus. Although chickpeas have a pH value higher than 4.5, in fact, adding mayonnaise or lemon juice to chickpeas can lower the pH value below 4.5, allowing hummus to be pasteurized.

[0013] Spores are known to survive pasteurization. In products with a pH value above 4.5 in the refrigerator, the bacteria may resume vegetative growth and multiply. REPFED therefore has a limited shelf life in the refrigerator.

[0014] There are three different pasteurization techniques, each of which gives food a different shelf life.

[0015] In the first pasteurization technique, the food is packaged and then pasteurized in its package at 90°C for at least 10 minutes. Pasteurized foods are free of Listeria monocytogenes, faecalis Streptococcus, and / or psychrotrophic nonproteolytic Clostridium botulinum.

[0016] A drawback of the pasteurization technique is that spores of bacteria, particularly Bacillus cereus, Clostridium botulinum and other spore-forming bacteria, can survive, although their growth in refrigerators is usually more limited than without the pasteurization.

[0017] A further drawback is that the food is pasteurized at relatively high temperatures for long periods of time, resulting in a significant deterioration in food quality.

[0018] The second pasteurization technique involves packaging the food and then pasteurizing it while still in the package at 70°C for at least 2 minutes.

[0019] This pasteurization technique is not very strong and is intended to obtain 6D Listeria monocytogenes. Other pathogens can survive this treatment. In particular, spores of spore-forming bacteria such as Bacillus cereus and Clostridium botulinum can survive this pasteurization treatment.

[0020] A disadvantage of the second pasteurization technique is that the shelf life of pasteurized foods is limited to a few days in the refrigerator, since various pathogens and their spores remain viable after the treatment.

[0021] Refrigeration in this context means that pasteurised foods are stored at temperatures between 0°C and 10°C.

[0022] Finally, the third pasteurization technique involves pasteurizing the food before packaging it.

[0023] In this pasteurization, the food can be pasteurized at 90°C for at least 10 minutes or at 70°C for at least 2 minutes, after which the food is packaged or repackaged (also called open pasteurization).

[0024] There is a significant risk of food becoming contaminated with L. monocytogenes and other pathogens after pasteurization.

[0025] Such pasteurized foods therefore have a very short shelf life in the refrigerator, lasting only a few days.

[0026] Pasteurization or sterilization of foods allows them to be stored for longer than they would be if they were untreated.

[0027] When preserving various foods, preservatives such as acids (e.g. potassium sorbate, benzoic acid) are often added to further extend the shelf life.

[0028] In addition, it is known that among the above mentioned bacteria, there are psychrophilic bacteria that are highly resistant to heat, such as psychrophilic strains of Bacillus cereus. These bacteria can survive and grow even after the aforementioned pasteurization techniques. The survival and growth of these pathogenic bacteria poses a health risk in industrially produced pasteurized refrigerated foods, also known as REPFED.

[0029] The aforementioned pasteurization techniques are not suitable to protect REPFED from psychrophilic strains of Bacillus cereus and / or its spores: the temperatures at which REPFED is pasteurized or stored are too low and the treatment times are too short to kill the psychrophilic strains of Bacillus cereus and / or its spores and to cause fatal damage to the spores so that they cannot grow.

[0030] It is an object of the present invention to provide a solution to at least one of the above mentioned and other disadvantages. Summary of the Invention

[0031] The present invention therefore aims to provide a shelf-stable refrigerated processed food (REPFED) with a pH value of 4.6 or more, whereby in the REPFED at a temperature between 0°C and 10°C, killed vegetative forms of Listeria monocytogenes and / or Streptococcus faecalis and / or Clostridium botulinum and Bacillus cereus are absent, whereby the spores of said bacteria are at least fatally damaged, such that the spores are no longer able to grow vegetatively on the associated bacteria.

[0032] The advantage of this is that the pH value of REPFED in the refrigerator is at least 4.6, more preferably 4.6-7.0, most preferably 4.6-6.0, so that the quality of REPFED is maintained or only minimally degraded, resulting in a much longer shelf life. The shelf life of said REPFED can be extended from weeks to months. Even better, the shelf life of REPFED is determined by the organoleptic properties of REPFED, rather than bacterial spoilage of REPFED.

[0033] A further advantage of said REPFED is that it is microbiologically commercially sterile in the refrigerator at least against vegetative psychrophilic Bacillus cereus, preferably against spores thereof, or whereby the spores are at least fatally damaged.

[0034] Commercial sterility is here understood to mean "a condition achieved by heating which eliminates from food the viable forms of microorganisms of public health importance, and microorganisms of no importance to health which may grow in the food under normal non-refrigerated conditions of storage and distribution" (Source: Public Health England, 1994).

[0035] The advantage of this is that the Bacillus cereus spores are killed or damaged so that they are unable to grow vegetatively or only grow very slowly in the REPFED refrigerator at pH values ​​between 4.6 and 7.0.

[0036] Furthermore, the present invention relates to a method for preserving the aforementioned fresh food stored in a refrigerator, the method comprising at least the following steps: a) Preheat the food you want to store. b) Heat the food to be stored at 110℃~115℃ for at least 10 to 60 seconds. c) Cool the heated food to 0℃~10℃. d) The food is aseptically packaged, ultra-clean packaged, or clean packaged in a sealable package with an oxygen concentration of less than 1 percent. Steps c and d can be executed interchangeably.

[0037] This method is a novel and original preservation method called oostromising.

[0038] Fresh food is understood to mean foodstuffs, more specifically prepared foods, also known as "durable refrigerated processed foods" (REPFED).

[0039] This method is called oostromising and is a novel and original preservation method, the advantages of which are explained below.

[0040] The advantage of this method is that the shelf life of food is extended from 7-11 days to 90 days at a maximum temperature of 10°C.

[0041] Additionally, this method has the advantage that no preservatives are used to preserve the aforementioned foods.

[0042] Another advantage is that by preheating the food, the temperatures of the various components of the food are at the same temperature, or substantially the same, as they were before the food was heated to 110°C-115°C.

[0043] As a result, temperature differences between different aggregation states of food can be prevented.

[0044] The method of the present invention not only kills and / or inactivates Listeria monocytogenes, Streptococcus faecalis, and / or psychrophilic non-proteolytic Clostridium botulinum, but also kills and / or inactivates spores of psychrophilic Bacillus cereus.

[0045] Psychrotrophs and / or Bacillus cereus spores are more heat resistant than Listeria monocytogenes, Streptococcus faecalis, and / or psychrotrophic non-proteolytic Clostridium botulinum, and therefore these will also be killed. The spores of said bacteria may be killed or fatally damaged to the point that they are no longer able to grow vegetatively as bacteria in the REPFED in the refrigerator.

[0046] The advantage of this method is that the B. cereus spores are killed or damaged so that they are unable to grow vegetatively or only grow very slowly at pH values ​​of 4.6-7.0 in the refrigerator.

[0047] A further advantage is that REPFED stored according to the above-described method does not suffer from extreme deterioration in quality.

[0048] In order to better illustrate the characteristics of the present invention, some preferred variants of the method for preserving fresh food according to the invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

[0049] FIG. 1 is a schematic diagram of the method of the present invention. FIG. 2 shows a variation of process D of FIG. 3 and 4 show a modified method of FIG.

[0050] The present invention relates to a refrigerated processed food (REPFED) that can be stored for a long period of time, said REPFED being free of vegetative Listeria monocytogenes and / or faecalis Streptococcus and / or Clostridium botulinum and psychrophilic Bacillus cereus at a pH value of 4.6 or more and at a temperature between 0°C and 10°C.

[0051] Preferably, said REPFED in the refrigerator does not contain said bacterial spores and / or those spores have been fatally damaged and are no longer capable of vegetative growth by the bacteria, known as "fatally damaged" spores.

[0052] In a preferred embodiment, the REPFED in the refrigerator is also free of vegetative psychrophilic B. cereus and its spores are at least fatally damaged.

[0053] Preferably, the REPFED in the refrigerator contains a pH value of at least 4.6, more preferably between 4.6 and 7.0, most preferably between 4.6 and 6.0.

[0054] An advantage of the above mentioned REPFED is that in the refrigerator, REPFED is microbiologically commercially sterile at least against psychrotrophic Bacillus cereus and preferably also against its spores.

[0055] Microbiologically commercially sterile is understood here to mean that REPFED under the above conditions is free of vegetative Listeria monocytogenes and / or faecalis Streptococcus and / or Clostridium botulinum and psychrophilic Bacillus cereus, the spores of which are at least fatally damaged.

[0056] Preferably, said REPFED is free of preservatives such as acids, sorbic acid and sorbate salts (E200-E203), benzoic acid and benzoate salts (E210-E219), sulfites (E221-E228), nitrites, nitrates, etc.

[0057] FIG. 1 shows a schematic diagram of a method 1 for preserving fresh food 2 stored in a refrigerator and killing vegetative microorganisms and / or spores of Bacillus cereus.

[0058] Fresh foods refer to industrially prepared foods stored in refrigerators, also called REPFED. Examples include refrigerated foods, refrigerated meals, ready-to-eat meals, etc. It is known that said REPFED is microbiologically unstable and therefore can only be stored for a limited period of time. The method according to the invention can be used to preserve REPFED without the addition of preservatives, whereby vegetative Listeria monocytogenes and / or Streptococcus faecalis and / or Clostridium botulinum and psychrophilic Bacillus cereus are killed, whereby the spores of said bacteria are fatally damaged and can no longer grow vegetatively into bacteria. The advantage of this is that the shelf life of REPFED in the refrigerator can be extended. Therefore, Bacillus cereus includes a group of highly heat-resistant Bacillus cereus, more specifically, psychrophilic Bacillus cereus. After storing REPFED with a pH value above 4.6 by the method described below, there is no nutrient psychrophilic Bacillus cereus in the REPFED in the refrigerator, and its spores are killed or fatally damaged. It is known that certain strains of Bacillus cereus can grow at temperatures above 10°C or above 12°C, and these strains are highly heat-resistant.

[0059] Such method 1 includes at least the following steps: a) Preheat the REPFED2 to be stored. b) Heat the REPFED2 to be stored at 110°C to 115°C for at least 10 to 60 seconds. c) Cool the heated REPFED3 to 0℃~12℃. d) The cooled REPFED 4 is aseptically packaged in a sealable packaging material 5 with an oxygen concentration of less than 1%. Here, steps c and d may be interchanged.

[0060] Additionally, reserve REPFED2 may be mixed during and / or prior to preheating in process A.

[0061] In the step of aseptic, clean, or ultra-clean packaging (Process D), the cooled REPFED 4 may be inserted into a sterile, ultra-clean, or clean packaging material, such as a bag, cup, container, or other packaging material, and vacuum sealed. The purpose of aseptic or clean packaging is to prevent subsequent contamination. Aseptic, clean, or ultra-clean packaging involves insertion and sealing in a controlled environment, which prevents subsequent contamination of the REPFED with microorganisms and / or their spores.

[0062] Another variation is shown in Figure 2. In the aseptic packaging process (Process D) of the cooled REPFED 4, nitrogen gas (N2) is sprayed or blown over the cooled REPFED 4 to eliminate air above the cooled REPFED 4. Nitrogen can also be pre-sprayed inside or on top of the REPFED 2 to cool it.

[0063] Thus, the cooled REPFED 4 in a sterile or clean or ultra-clean package (Process D) can be applied to a sealable packaging material 5, which in the illustrated example is a container, after which nitrogen gas (N2) is blown or sprayed onto the open side 6 of the container.

[0064] While nitrogen gas (N2) is being sprayed or sprayed, a lid 7 is placed over the open surface 6 of the container to seal the packaging material 5, thereby trapping the nitrogen gas (N2) in the space 8 between the food 4 and the lid 7.

[0065] Preferably, the cooled REPFED4 is still warm before the aseptic or clean or ultra-clean packaging with nitrogen gas (N2) (Process D), whereby the cooled REPFED4 is rapidly cooled during and after the packaging process D with nitrogen gas (N2).

[0066] In this way, REPFED2 can be cooled very quickly. Specifically, REPFED can be cooled up to 10°C within a few minutes. Thus, REPFED2 can be cooled to below 10°C within 5 minutes.

[0067] In a practical embodiment of the cooled REPFED 4, the aseptic packaging of the food product 4 (process D) takes place in a sealable chamber 9, where nitrogen gas (N2) is blown or sprayed onto the cooled REPFED 4 and collected, creating an overpressure in the chamber 9. The overpressure has the advantage that the package does not deform during cooling.

[0068] Thereafter, a mixture of air and nitrogen gas (N2) is present in the chamber 9.

[0069] As shown in FIG. 3, if steps c and d of the method are interchanged, it is also possible to pre-cool the cooled REPFED4 to a temperature of 10° C. to 12° C. (process E) before aseptic packaging (process D).

[0070] In this case, the food product 4 can be cooled after packaging (process D) to a maximum of 12°C, preferably to 10°C.

[0071] Preferably, the temperature during packaging of REPFED (Process D) is below 100°C, more preferably between 70°C and 95°C, most preferably between 82°C and 92°C.

[0072] Preferably, the stored REPFED2 is heated (Process B), for example by ohmic heating.

[0073] In a preferred embodiment, the stored REPFED2 is heated to 40°C to 80°C, more preferably 50°C to 70°C, and most preferably 60°C to 65°C during pre-heating (process A).

[0074] In another embodiment, as shown in Figure 4, the cooled REPFED4 is packaged after a sterile, clean or ultra-clean packaging step to prevent post-contamination. Vegetative Listeria monocytogenes and / or Streptococcus faecalis and / or Clostridium botulinum and Bacillus cereus are killed and the spores of these bacteria are fatally damaged and can no longer grow vegetatively into bacteria. Process D and Process F may be interchanged and further cooling may be performed up to 12°C, preferably 10°C.

[0075] Preferably, the method of the present invention not only kills and / or inactivates Listeria monocytogenes, Streptococcus faecalis and / or psychrophilic non-proteolytic Clostridium botulinum, but also kills and / or inactivates spores of psychrophilic Bacillus cereus and / or Listeria monocytogenes and / or Streptococcus faecalis and / or psychrophilic non-proteolytic Clostridium botulinum.

[0076] The present invention also relates to a REPFED having the properties as described above, the REPFED being obtainable by a process as described above.

[0077] Preferably, for determining the lethality and / or inactivation of microorganisms, an apparatus and / or a method and / or a use as defined in BE2022 / 5016 is used.

[0078] The method and / or device and / or their use can mimic the lethality and / or inactivation of microorganisms in the aforementioned food preservation methods very accurately, resulting in an accurate determination of the lethality and / or inactivation of microorganisms in the food. Spore recovery or growth can also be determined, thereby simulating both the heating, holding and cooling times and temperatures of REPFED.

[0079] The invention is in no way limited to the variants described by way of example and shown in the drawings, and such a method can be realised according to different variants without departing from the scope of the invention.

Claims

1. A shelf-stable refrigerated processed food (REPFED), wherein the REPFED has a pH value of 4.6 or more and is at a temperature between 0°C and 10°C and is free of killed vegetative forms of Listeria monocytogenes and / or faecal streptococci and / or Clostridium botulinum and Bacillus cereus, whereby spores of said bacteria have been fatally damaged and are no longer capable of vegetative growth by the associated bacteria.

2. 2. The REPFED according to claim 1, characterized in that the REPFED in the refrigerator is free of vegetative psychrophilic Bacillus cereus and its spores are at least fatally damaged.

3. A REPFED according to any one of the preceding claims, characterized in that the pH value of the REPFED in the refrigerator is between 4.6 and 7.0, most preferably between 4.6 and 6.

0.

4. 10. The REPFED according to any one of the preceding claims, characterized in that the REPFED is preservative-free.

5. A method (1) for preserving the "long-term storage refrigerated processed food (REPFED)" according to any one of claims 1 to 4, comprising at least the following steps: a) Preheat the REPFED (2) to be stored; b) Heat the REPFED (2) to be stored at 110°C to 115°C for 10 to 60 seconds; c) cooling the heated REPFED (3) to 0°C to 12°C; d) The REPFED (4) is placed in a sealable packaging material (5) and packaged aseptically, ultra-clean or cleanly with an oxygen concentration of less than 1%. Here, steps c and d can be performed in the reverse order.

6. During the aseptic packaging (D) of the cooled REPFED (4), nitrogen gas (N ２ 6. The method according to claim 5, characterized in that the air above the cooled REPFED (4) is replaced by spraying or spraying the

7. During the aseptic packaging (D) of the cooled REPFED (4), nitrogen gas (N ２ 7. The method according to claim 5 or 6, characterized in that the mixture is sprayed or sprayed onto the cooled REPFED (4).

8. Nitrogen gas (N ２ While the REPFED (4) is being sprayed or sprayed with nitrogen gas (N), a lid (7) is placed over the open side (6) of the packaging material (5) to seal the packaging material (5), and nitrogen gas (N ２ 8. The method according to claim 7, characterized in that

9. 9. The method according to any one of claims 5 to 8, characterized in that in process B, the stored REPFED (2) is heated by ohmic heating.

10. 10. The method according to any one of claims 5 to 9, characterized in that the stored REPFED (2) is mixed before and / or during pre-heating (Process A) of the stored REPFED (2).

11. A method according to any one of claims 5 to 10, characterized in that pre-heating (Process A) of the REPFED (2) to be stored comprises heating said REPFED (2) to a temperature between 40°C and 80°C, more preferably between 50°C and 70°C, most preferably between 55°C and 65°C.

12. 12. The method according to any one of claims 5 to 11, characterized in that steps c and d in method (1) are carried out in the reverse order, and the cooled REPFED (4) is pre-cooled (Process E) to 110°C to 12°C, more preferably 100°C to 60°C, most preferably 83°C to 87°C, before aseptic packaging (Process D).

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