RU2421002C1 - Meat raw material sterilisation method - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention is intended for usage in meat industry for meat raw material sterilisation. Sterilisation is performed by a combined two-stage physical-chemical method. At the first stage milled meat raw material is treated with 1% propionic acid solution during 2 minutes in an acid-resistant vessel. At the second stage the raw material in the form of a 30-40 mm thick layer (placed into special moulds of a radiotransparent material) is sterilised in a continuous action microwave installation with oscillation power 20 kW at a frequency of 915 MHz during 30-40 sec.

EFFECT: method ensures disinfection of meat-and-bone mince from spore microflora.

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Description

The invention relates to the field of sterilization of meat and bone raw materials and can be used in the livestock industry or processing industries.

Currently, sterilization of livestock and meat products is carried out mainly in autoclaves at significant overpressure (US Patent No. 6207215, A23B 4/005, Pub. 02.27.2001 High temperature / ultra highpressure sterilization of foods). For example, canned meat is sterilized in autoclaves at a pressure of 1.5 atm for 2-2.5 hours. When the temperature in the center of the can reaches 120 ° C. As a result, the so-called “industrial sterility” occurs when no more than 10 non-pathogenic microorganisms are found in 1 g of canned food (Flaumenbaum B.L. Theoretical basis for sterilizing canned food. Kiev, 1981. - 196 p. GOST 30425-97 Canned food. Method for determining industrial sterility ) Sterilization of slaughter cattle and dead animals is carried out in horizontal vacuum boilers of the KVM-4.6, GVK-2.6 type for 4-5 hours at an overpressure of 3-4 atm (Liberman S.G., Petrovsky V.P. Handbook for the production of technical products at meat plants. M: 1969. - 407 p.).

The disadvantage of this method is its limited use, since autoclaving is used only in a small number of processing enterprises, and a limited number of specially trained operators are allowed to work on high-pressure apparatuses.

In this regard, an ongoing search is being made for alternative ways of inactivating microorganisms in food or raw materials. Therefore, recently, microwave technology and technology have found increasing application in industry and household (US Patent No. 4393088, MKI A23L 3/10; Sterilizing process for foods by applying microwaves thereto // Matsusaka O. - Publish. 07.12.83) . (Patent RU No. 97122003 “Method for determining the technological characteristics of microwave processing of agricultural materials and food products.” - Application. 12/26/97. - Publish. 08/27/99). (Patent RU No. 94016416. "Drying household microwave oven." - Application. 04/27/94. - Publish. 02.10.95). (Patent RU No. 93019796, IPC Н05В 6/64 "Microwave oven" Application. 04.15.93, publ. 09.10.95).

The main features of microwave processing include: the ability to penetrate to a considerable depth inside the product, the independence of the duration of heating to a given temperature on the volume and shape of the product, the absence of its contact with the coolant, and high efficiency of converting energy to heat released in the heated object. The death of microorganisms in a high-intensity microwave field is caused, as a rule, by hyperthermia, leading to irreversible coagulation of the protein. In addition, inactivation of enzymes and other physiologically important components occurs in the microbial cell.

Known methods of processing in the microwave field of meat products, fish and seafood. There is scientific evidence that during microwave heating of food products for 3 min, the vegetative microflora is destroyed (Rogov I.A. Microwave heating of food products. M .: 1986. - 351 p.). In the monograph by V.V. Vorobyov “Processing hydrobionts with microwave heating and product quality control”, M. 1998, 345 p. provides information on the death of vegetative microflora in fish and seafood under various modes of microwave processing. Apparently, when processing products under the influence of microwaves in microbial cells, enzyme systems partially incapable of rapid adaptation are partially affected. At the same time, under the influence of microwaves, the membrane of microbial cells is destroyed. As a result of the analysis of scientific and technical information and the results of our own research, it was found that the microwave field is mainly fatal to the vegetative form of microorganisms and, as a rule, does not cause spore inactivation.

Information on the harmful effects of the microwave field on spores and spore-forming microflora is extremely limited. An article by Kim SY, Shin SJ, Song CH, Jo EK, Kim HJ, Park JK “Destruction of Bacillus licheniformis spores by microwave irradiation” (J. Appl. Microbiol. 2009) noted that MV processing at 2 kW and exposure 60 s do not lead to the complete destruction of Bacillus licheniformis spores. It should be noted that the results were obtained on a pure culture of Bacillus licheniformis, not protected from microwave radiation, for example, by proteins or lipids.

The impact on microorganisms of certain chemicals (preservatives) leads to the inactivation of certain enzymes, in particular dehydrogenases, which causes a halt in the oxidation processes and the synthesis processes associated with them, i.e. to cessation of microbial cell activity. In addition, chemical preservatives can change the composition of the nutrient substrate for absorption by microorganisms and, accordingly, to the bacteriostatic effect.

For example, in relation to spore-forming bacteria of the genus Bacillus, destruction of the microbial cell wall as a result of the action of preservatives has been established (P. Setlow. Spores of Bacillus subtilis: their resistance to and killing by radiation, heat and chemicals. Department of Molecular, Microbial and Structural Biology). When using preservatives, the stable multilayer protein-fatty membrane of spores, cortex, and peptidoglycans are destroyed.

However, it was found that as a result of the analysis of scientific and technical information and their own research, chemical preservatives have a detrimental effect mainly on the vegetative microflora and are not able, as a rule, to inactivate spores and spore-forming microflora. So, in our studies on an Electrolux microwave oven with a power of 800 W after processing minced meat, infected with Bac.sereus spores at a concentration of 10 ⁶ CFU / g, only with propionic acid at a concentration of 1% for 2 minutes and after appropriate thermostation was noted Colony growth of Bac.sereus (Table 1).

Table 1 The effectiveness of disinfection of meat and bone paste after treatment with propionic acid and a combined method Sample MAFANM Bacillus Meat and bone paste (1% rd, 2 min) Solid growth Solid growth Meat and bone paste (1% rd, 3 min) Solid growth Solid growth Meat and bone paste (1% rd, 2 min, microwave 2 min) No growth No growth Meat and bone paste (1% rd, 3 min, microwave 2 min) No growth No growth

To prove the effectiveness of the combined method of sterilization of meat and bone raw materials, experiments were performed on meat and bone mince, artificially infected with Bac.sereus spores at a concentration of 10 ⁶ CFU / g. Further microbiological studies carried out at SibNIIP found that the processing of minced bone-minced meat contaminated with Bac.sereus spores only in a microwave field with a power of 800 W for 2-3 minutes did not cause a bactericidal effect (Table 2).

In further experiments, seeded minced meat was first treated with propionic acid at a concentration of 1% for 2 minutes, then it was exposed to a microwave field for 2-3 minutes. As a result, sterilization of the investigated meat and bone mince was achieved.

table 2 The effectiveness of microwave disinfection of Bac.sereus on meat and peptone broth Processing time, min Unheated suspension of microbial cells (vegetative form) Heated suspension of microbial cells (spore form) one - + 3 - + 5 - + - lack of microbial growth; + the presence of microbial growth

The drying and inactivation processes of minced meat and bone microorganisms are essentially different physical processes. Indeed, drying requires the transfer of the electromagnetic energy contained in the minced water necessary for the evaporation of the required amount, Δm _in , of water in accordance with the heat of vaporization, q = 2256 kJ / kg and overcoming the resistance to the exit of water vapor from the material. The inactivation of microorganisms requires exposure directly to energy of a certain power level.

For example, at the initial moment of drying, when a material contains a large amount of water having a high dielectric constant, ε = 80, it is water that absorbs the bulk of the energy, as a result of which the bulk of the energy is spent on the evaporation of water. Therefore, during this period of the process, the temperature of the minced meat remains low (50-60 ° C), and inactivation of microorganisms practically does not occur. As the water contained in the meat is evaporated, that is, its moisture decreases, due to a decrease in the volume of water, the absorption of electromagnetic energy by the meat itself increases (its temperature by the end of the drying process, that is, when the forcemeat moisture reaches W _k = 10%) increases to 100-110 ° С and at the same time the amount of energy absorbed by microorganisms increases.

The present invention is to develop a method for sterilizing spores and spore-forming aerobic microflora (such as Bac.sereus, Bac.subtilis) contained in meat and bone raw materials, using a combined two-stage physicochemical method.

When processing minced meat in a microwave field, the necessary parameters were determined (power, processing time, layer thickness). In the process of working on a microwave installation f = 915 MHz, a series of experiments was carried out to determine the optimal power of the microwave influence. Minced meat was processed at 5, 10 and 20 kW. The experiments showed that the energy consumption for drying the same amount of material is practically independent of the power absorbed by the meat and bone meat. In all experiments, the drying results remained constant at the same microwave energy: Q _pad = P _pad Δt (i.e., at P _pad = 5 kW and Δt = 2 min, P _pad = 10 kW and Δt = 1 min, P _pad = 20 kW and Δt = 30 s, the impact energy was the same). But the bactericidal effect was obtained only at P _pad = 20 kW and Δt = 30 s, then the temperature of the stuffing reached 110-120 ° C.

The upper limit of the acting energy Q _pad was set according to the final humidity of the minced meat and its organoleptic characteristic. So, when the force P _pad = 20 kW was applied to the forcemeat, a minimum humidity of 10% was obtained for 60 s and the forcemeat temperature exceeded 120 ° C. However, according to organoleptic indicators (minced meat was partially charred), this microwave drying regime was recognized as unacceptable. In further studies, it was found that stable biochemical parameters and guaranteed bactericidal activity of minced meat were obtained at P _pad = 20 kW and Δt = 30-40 s.

Experiments to determine the optimal thickness of the meat layer were carried out in the range of 30-50 mm. The results of these experiments with an accuracy of ± 5% showed that when drying the meat and bone meat, the process efficiency practically did not depend on the flow thickness in the studied range and amounted to 0.75 ± 0.05, which is associated with the penetration of the microwave field over the entire thickness of the meat.

The method is as follows. In the first stage, the raw material is treated with a 1% solution of propionic acid for 2 min in an acid-resistant container. Propionic acid significantly inhibits the development of putrefactive and butyric acid bacteria. Lowering the pH of the medium leads to loosening of the surface amphoteric structures of the cell and, as a result, to the disruption of the physiological state of the microbial cell.

At the second stage, meat and bone raw materials in the form of a layer 30–40 mm thick, depending on the type of raw material, are processed for 30–40 s in a continuous microwave installation with an oscillatory power of 20 kW at a frequency of 915 MHz.

Microwave energy is introduced into the interaction zone through the waveguide, providing excitation in the working chamber of the wave H ₁₀ . The product is introduced into the working microwave chamber in the form of a layer 30–40 mm thick on the conveyor, the plane of which is located at an angle of ≈30 ° to the axis of the waveguide. Stuffing placed in the molds is introduced into the chamber through the box, rigidly connected to the waveguide of the chamber and through the slot in the waveguide, located symmetrically about its axis, enters the chamber. Slit width 70 mm. In the upper part of the box is absorbing material, which is used carbonyl iron. It is designed to absorb the damaging radiation from the waveguide slots of the input and output of the material to ensure the safety of personnel.

The waveguide of the chamber has an internal section of 124 × 248 mm, which ensures the propagation in it at a frequency of 915 MHz of a wave of the main type H ₁₀ , which creates a maximum of the electromagnetic field in the cross section of the minced meat.

A microwave generator is connected to the camera on either side, and on the other hand, it can be connected to any waveguide device (to a similar camera or to a load).

Stuffing passes through the chamber in forms made of radiolucent material (fluoroplastic, quartz glass, etc.). The design of the mold should not contain a single metal element.

An angle of 30 ° between the incident electromagnetic wave and the surface of the product ensures good coordination of the chamber, and the resulting large length of the heating zone allows one to obtain a high coefficient of utilization of microwave energy. The remainder of the unabsorbed energy is absorbed in the water load located behind the conveyor plane. As studies have shown, the chosen design creates favorable conditions for maintaining a traveling wave of type H ₁₀ in the working chamber. The processed raw material moves along the chain of the dielectric container made of polypropylene. The width of the stream is 300 mm. The conveyor speed is 1 m / min.

Since at the first stage the strong spore membrane was partially destroyed by propionic acid, accordingly, a deeper penetration of the microwave field into the processed raw material occurs and as a result sterilization of the raw material is achieved (see Table 1).

After determining the optimal parameters for microwave processing of meat and bone meat, the effectiveness of its disinfection was determined by the following microbiological indicators: KMAFAM, BGKP, salmonella. It was found that after irradiation of meat and bone meat samples containing 10 ⁷ CFU / g at a frequency of 915 MHz, with a power of 20 kW for 30-40 s, the residual amount of microflora did not exceed 59 CFU / g. In the tested samples, after treatment, no bacteria of the Escherichia coli group (BHEC) as well as Salmonella were found. The results obtained are presented in table.3.

Table 3 The effectiveness of the disinfection of meat and bone paste after microwave processing in an experimental setup at a frequency of 915 MHz Sample MAFANM BGKP Salmonella Meat and bone paste (control) 7.9 × 10 ⁷ Detected Not found Meat and bone paste (20 kW, 40 s) No growth Not found Not found Meat and bone paste (20 kW, 40 s) 1) no growth Not found Not found 2) no growth Not found Not found 3) 27 * Not found Not found 4) 59 * Not found Not found Note: As a result of microwave processing of meat and bone meat, a decrease in the value of MAFAnM by 6 orders of magnitude * according to SanPiN 2.3.2.1078-01 (1.1.4.4-1.1.4.10) for cooked sausages, KMAFAnM, CFU / g of not more than 1000 are allowed.

Information on the effect of the presented combined physicochemical method on spores and spore-forming aerobic microflora contained in meat and bone raw materials was not found in the scientific and technical literature.

Claims (1)

Method for sterilization of meat raw materials, characterized in that at the first stage the raw materials are treated with a 1% solution of propionic acid for 2 minutes in an acid-resistant container, at the second stage the raw materials pre-treated with acid are sent for disinfection to a continuous microwave unit with an oscillating power of 20 kW at frequency of 915 MHz for 30-40 s and a layer thickness of 30-40 mm.