RU2768698C1 - Method for express analysis of freshness of meat food and photoluminescent analyser device for implementation thereof - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention relates to food industry and production process control equipment and can be used for express assessment of meat freshness due to determination of their characteristic storage time without preliminary sampling. Disclosed is a method for determining freshness of meat, which involves rapid analysis by irradiating a controlled meat sample with monochromatic laser radiation and subsequent analysis of the resulting fluorescent radiation in the fluorescence band, based on the results of which the state of the meat is determined, wherein at first, reference photoluminescence spectra of fresh meat samples are formed and stored in a database, then the controlled meat sample is measured by irradiating it with a laser with wavelength of 405 nm, which is directed through a set of band-pass filters in range of 600–800 nm and a focusing system in the form of a lens so that radiation reflected from the controlled meat sample falls on the spectrometer, which is located inside a casing blocking the penetration of spurious electromagnetic radiation of the visible range of third-party emitters, the radiation received by the spectrometer is detected and determining the quantitative value of the intensities of the photoluminescent lines of protoporphyrin IX, as an indicator of bacterial contamination of the monitored meat, lying in the red wavelength range of 600–800 nm, the obtained data are sent for comparing the intensities of these photoluminescence lines with the intensity of the reference photoluminescent spectrum from the reference spectra database, wherein freshness of the controlled meat sample is established based on the compliance of the obtained intensity values for these photoluminescence lines of the controlled meat sample with the intensity values of these photoluminescence lines laid down in these reference spectra. Also disclosed is a device for implementing said method for determining freshness of meat in the form of a photoluminescent analyser, which consists of a protective housing, configured to block spurious electromagnetic radiation of the visible range of third-party emitters, inside which there is a power source, a laser with wavelength of 405 nm, a focusing system in the form of a lens, system for filtering detected radiation, consisting of a set of band-pass filters of 600–800 nm, a spectrometer, which is connected to at least one detector of electromagnetic radiation in the visible range, which is connected to a signal processing controller, where the output of the latter is connected to a control unit consisting of a microprocessor unit and a database of reference photoluminescence spectra of fresh meat samples, wherein the microprocessor unit is connected to a display, a laser and a power supply unit.

EFFECT: invention enables fast analysis of freshness of a meat sample, without the need for sampling, as well as portability of the analysis system.

2 cl, 4 tbl, 9 dwg

Description

SUBSTANCE: invention relates to the field of food industry and production process control technology and can be used for rapid assessment of the freshness of meat food products by determining their characteristic storage time without prior sampling.

As you know, food products are constantly and quite heavily contaminated with various microorganisms. It is customary to differentiate the microflora that seed food products into specific and nonspecific [see, for example, Shustrova N.M., Snegireva A.E., edited by Krasovsky P.A. // Microbiological examination of product quality. MU MHSE. MP-016-2002]. The first includes microorganisms artificially introduced into the product to give it certain properties. Nonspecific microflora includes microorganisms that in vivo seed organs and tissues of animals in case of disease or violation of the barrier functions of the intestine, injuries, starvation, overheating or hypothermia of the animal body. If the sanitary conditions for obtaining food at the stages of harvesting, processing, transportation and storage are not observed, secondary contamination with microorganisms is also possible. Microorganisms that cause spoilage and rotting of food products most often have pronounced proteolytic activity. Their entry into products is undesirable, since they reduce the biological and nutritional value, and in some cases make it impossible to use products in food. Along with changes in the organoleptic properties of the product, microorganisms contribute to the accumulation of toxic components that can lead to food poisoning.

Microorganisms that seed meat products in the course of their life activity synthesize a large number of different substances, some of which can serve as a kind of indicator of contamination of these products. Protoporphyrin IX is an important precursor in the synthesis of heme, cytochrome c, and chlorophylls by bacteria, and at the same time it can serve as an indicator of the degree of bacterial contamination of meat products, because when excited by laser light with a wavelength of 405 nm, it has an intense photoluminescence in the red spectral region of 600-800 nm [see, for example, J. Biomed. Opt. 21(12), 125008]. By evaluating the intensity of this photoluminescence, one can judge the degree of bacterial contamination, the storage time of meat foodstuffs, and thus their freshness.

To date, there is no device that reliably assesses the freshness of meat products and the degree of their bacterial contamination in express mode. The classic method for determining the number and identification of microorganisms in meat foods is the microbiological method, which is used to determine the number of mesophilic aerobic and facultative anaerobic microorganisms (QMAFAnM) and differentiate microorganisms by serial 10-fold dilutions of liquid meat swabs, followed by parallel seeding on cups with 5% blood agar, mannitol salt agar, SS agar, TSN agar, Schedler agar, Sabouraud's medium, Endo's medium and others. But it is lengthy and requires highly qualified service personnel and specialized stationary laboratories and microbiological facilities.

Measuring the optical characteristics of meat products after excitation of the sample by electromagnetic radiation takes a small amount of time and does not require large and expensive measuring equipment.

A device is known that implements a method (patent SU 1244589) for determining the quality of meat, which involves preparing a sample and measuring its color parameter, characterizing its quality by reflectance coefficients of a meat sample at wavelengths of 480-520 nm and 640-720 nm. The disadvantages of the device are that the method implemented by him is quite laborious and requires prior sampling. And also this device has a low sensitivity and specificity, tk. the change in the reflectance is due to a large number of reasons, some of which are not directly related to the spoilage of meat products.

A device is known that implements a method (patent RU 2015507) for determining the quality of meat products by exposing a sample to electromagnetic radiation in the range of about 800 - 1800 nm to determine the presence of worms in it and further analysis of the characteristic absorption of radiation by worms present in the specified product. The disadvantages of the device are that its operation requires preliminary sampling, and it allows you to examine only those meat samples that already contain worms, that is, they are rejected at the factory.

A device is known (patent RU 2035399) for determining the quality of meat, which involves measuring the magnitude of the intensity of reflected light, followed by setting the value of the reflection coefficient. Measurement of the intensity of reflected light is carried out directly in the thickness of the test sample at a depth of 5-7 cm by introducing into the last optical needle, while the measurement uses a light flux with a wavelength of 600-720 nm. The main disadvantage of the device is that the broad spectral bands of reflection, absorption and transmission have no specificity and therefore, based on their analysis, it is impossible to reliably and reproducibly determine the quality and freshness of meat products under various storage conditions of the studied samples.

Known solutions for assessing the freshness of fish, set out in applications US2015330906, US2017074784, based on the measurement of the absorption (or reflection) spectrum of light in the range of 315-450 nm from the eye of the fish. When developing this method, it was established as a result of detailed studies that when the fish ages, a wide characteristic light absorption band appears in its eye in the range from 315 to 450 nm. The absorption intensity at the peak of the band, near 410 nm, increases monotonically as the fish ages.

US2015330906 and US2017074784 offer a range of options for assessing the freshness of fish by light absorption in its eye. In the most sophisticated implementations, the absorption (or reflection) spectrum of light from a continuous spectrum source in the eye of a fish or in a biological fluid removed from the eye and placed in a quartz optical cuvette is measured. In simpler versions, a set of narrow-band light sources with different wavelengths is used. To assess the freshness, it is proposed to compare the absorption in the characteristic band with the absorption far from it, or the absorption levels on the side of short and long waves from the band. Finally, a variant with one narrow-band source with a maximum in the region of 410–430 nm was proposed for measuring the absolute value of absorption in the region of the most characteristic absorption band in the eye of a fish. In any case, to assess freshness, the absolute value of light absorption is measured, A (λ) = -log( I (λ) / I ₀ (λ)), where I ₀ (λ) is the intensity of the incident light, I (λ) is the intensity of the reflected or transmitted light.

Known methods for assessing the freshness of meat products require the measurement of the absolute characteristics of the optical spectrum. Accordingly, the estimation accuracy is significantly lower than when measuring the relative value of the optical characteristic.

In addition, known techniques require optics to focus light onto the surface of the test sample and to collect luminescence light.

The closest in technical essence to the claimed solution is a device that implements a method for remote spectral quality control of meat (patent RU2170928, publ.: 07/20/2001), including irradiation of a controlled meat sample with monochromatic laser radiation with a wavelength of 488 nm and subsequent analysis of the resulting fluorescent radiation in fluorescence band, the results of which are used to judge the state of the meat, characterized in that, when analyzing fluorescent radiation, two spectral sections with maxima at wavelengths λ ₁ = 510 nm and λ ₂ = 545 nm are isolated from the fluorescence band using appropriate spectral-selective interference filters , measure the intensities J ₁ and J _{2 of} fluorescent radiation at the indicated wavelengths with the corresponding photodetectors, compare the values of the intensities J ₁ , J ₂ with each other and, if the value of the ratio J ₁ /J ₂ ≥ 1, give a positive assessment of the analysis performed, corresponding to high-quality meat, and at the value of the ratio J ₁ /J ₂ < 1 give a negative assessment of the analysis, corresponding to meat with pathogenic bacteria.

The technical problem of the prototype is that the green fluorescence region (in the wavelength range of 500-565 nm) from the studied meat products is not informative and specific when considering the processes of their spoilage and decay, because in the green area, a broad fluorescence is observed, which is inherent in all types of tissues (connective, epithelial, muscle), substances and metabolites that make up the studied meat sample. For the bacterial microflora accumulated as a result of the processes of decay and spoilage of meat products, photoluminescence from substances synthesized by these bacteria is characteristic in the red region of wavelengths of 600-800 nm.

The objective of the invention is to create such an express assessment of the freshness of meat food products without the need for sample analysis, which is portable and efficient, and at the same time does not have the disadvantages inherent in known solutions.

The technical result of the invention is the ability to quickly analyze the freshness of meat food products, without the need for sampling, portability of the analysis system.

The specified technical result is achieved due to the fact that the claimed method of conducting an express analysis of the freshness of meat food products, characterized by irradiation of a controlled sample of meat with monochromatic laser radiation and subsequent analysis of the emerging fluorescent radiation in the fluorescence band, the results of which are used to judge the state of the meat, moreover, when analyzing the fluorescent radiation is isolated from the fluorescence band of a certain spectrum using the appropriate spectral-selective interference filters, characterized in that, first, reference photoluminescence spectra of fresh meat samples and meat aged at a certain temperature regime for a strictly set time are formed and stored in a database, then they are measured of a controlled sample of meat, by irradiating it with a laser with a wavelength of 405 nm, which is directed through a set of band-pass filters in the range of 600-800 nm and a focusing system in such a way that The radiation emitted from the meat sample fell on the spectrometer, which is placed inside a casing that blocks the penetration of parasitic electromagnetic radiation in the visible range from third-party emitters; the radiation received by the spectrometer is detected and the quantitative value of the intensities of the photoluminescent lines of protoporphyrin IX lying in the region of red wavelengths of 600-800 nm is determined; the obtained data are sent for computer processing to compare the intensities of these photoluminescence lines with the intensity of the reference photoluminescence spectrum from the database of reference spectra, and the storage time and freshness of the test meat sample are set based on the correspondence of the obtained values of the intensities of these photoluminescence lines of the controlled meat sample to the intensity values of these photoluminescence lines, embedded in the data of the reference spectra.

Also claimed is a device for a photoluminescent analyzer for express analysis of the freshness of meat food products, functioning according to the described method, and consisting of a protective housing designed to block parasitic electromagnetic radiation in the visible range of third-party emitters, inside which are located: a power source, a source of laser radiation with a wavelength 405 nm, focusing system, filtering system for detected radiation, consisting of a set of bandpass filters 600-800 nm, a spectrometer, which is connected to at least one detector of electromagnetic radiation in the visible range, which is connected to the signal processing controller, where the output of the latter is connected to the control unit, consisting of a microprocessor unit and a database of reference photoluminescence spectra of fresh meat samples and meat aged at a certain temperature regime for a strictly set time, and the microprocessor unit is connected to the display, laser and power supply.

Brief description of the drawings

Figure 1 schematically shows the principle of operation and the scheme of the device of the analyzer for assessing the freshness of meat products.

Figure 2 shows an example of a reference graph of the revealed relationship that beef meat stores for various periods of time at all studied temperatures within one equivalent storage time at a temperature of +22°C.

Figure 3 shows graphs of the ratio of the intensity of the luminescence of waste products of anaerobic and aerobic bacteria of pork.

Figure 4 shows graphs of the ratio of the intensity of the luminescence of waste products of anaerobic and aerobic beef bacteria.

Figure 5 shows a graph of intensity versus time on a double logarithmic scale of one of the characteristic lines of photoluminescence of a substance-indicator of bacterial contamination of protoporphyrin IX of a sample of pork meat at a temperature of +22°C for 100 hours.

Figure 6 shows the time dependence of the intensity of one of the characteristic lines of photoluminescence of a substance-indicator of bacterial contamination of protoporphyrin IX, synthesized during the vital activity of bacteria, in a pork sample at a storage mode of +22°C on a double logarithmic scale.

Figure 7 shows examples of test pads for actually testing meat rot.

Figure 8 shows examples of the identified burst growths of colonies of putrefactive bacteria.

Figure 9 shows examples of serial dilution of washings from meat by 10 times and counting of bacterial colonies (samples A, B - pork, C - beef for stale meat and samples D - pork, D - beef - for fresh meat.

On the drawings: 1 - a casing that blocks the penetration of parasitic electromagnetic radiation in the visible range of third-party emitters, 2 - a laser with a wavelength of 405 nm, 3 - a focusing system (lens), 4 - a meat sample under study, 5 - bandpass filters in the range of 600-800 nm, 6 - spectrometer, 7 - detector of electromagnetic radiation of the visible range, 8 - signal processing controller, 9 - control unit, 10 - microprocessor unit, 11 - database of reference photoluminescence spectra of fresh meat samples and meat aged at a certain temperature regime for a strictly established time, 12 - display, 13 - photoluminescent radiation, 14 - power supply.

Implementation of the invention

The essence of the invention lies in the fact that photoluminescent express analysis is carried out with a wavelength of exciting radiation of 405 nm using a controller and software is recorded, processed and quantitatively analyzed the intensity of photoluminescent lines of protoporphyrin IX, lying in the region of red wavelengths of 600-800 nm, which is an indicator bacterial contamination of the studied meat food product.

According to the data obtained, the freshness of the meat product is judged by pre-normalized photoluminescent spectra of a reference sample of fresh meat and meat aged at a certain temperature regime for a strictly specified time. Reference values are stored in the database of photoluminescent spectra of the analyzer, and they determine the characteristic storage time and freshness of the studied meat sample by comparing photoluminescent lines.

Measurements are made either directly on bovine carcasses after slaughter, or on chilled or frozen meat, or on ready-to-eat meat dishes. Samples for analysis can be packed in a material that is transparent to electromagnetic radiation in the visible spectral range or can be placed outdoors. They can be minced meat, whole cuts of meat or ready-to-eat meat dishes.

The photoluminescent analyzer (see Fig.1) consists of a casing (1) that blocks the penetration of parasitic electromagnetic radiation in the visible range of third-party emitters, a source of laser radiation with a wavelength of 405 nm (2), a focusing system (3) (lenses or lens systems) and radiation filtering.

The radiation filtering system can be made consisting of a set of bandpass filters in the range of 600-800 nm (5) or a spectrometer (6) connected to at least one detector (7) of electromagnetic radiation in the visible range, which is connected to a signal processing controller (8), where the output of the latter is connected to a control unit (9) consisting of a microprocessor unit (10) and a database (11) of reference photoluminescence spectra of fresh meat samples and meat aged at a certain temperature regime for a strictly set time, and the microprocessor unit (10) connected to the display (12), which displays the measurement results.

The microprocessor unit (9) is connected to the display (12), laser (2) and power supply (14).

The database (11) may be a block of memory, for example, in the form of a removable media (flash card).

This design of the analyzer in view of the smallness and simplicity of design (see Fig.1) is portable.

The principle of operation of the device is as follows.

According to the signals from the control unit (9), power from the power supply unit (14) is supplied to the laser (2). From the laser (2) through band-pass filters in the range of 600-800 nm (5) and the focusing system (3), radiation is sent to the meat sample under study (4). Photoluminescent radiation (13) from the sample (4) passes to the spectrometer (6), from where the signal goes to the detector (7) of electromagnetic radiation in the visible range and then to the signal processing controller (8). The data from the latter are fed to the control unit (9), specifically to the microprocessor unit (10), where they are compared with the data from the database (11) of the reference photoluminescence spectra of fresh meat samples and meat aged at a certain temperature regime for a strictly set time .

The parameters set by the microprocessor unit (10) for the studied meat sample are displayed on the display (12).

This method of analysis provides a quick analysis of the freshness of meat food products, since the speed of data processing, including comparison of the obtained data with the reference database, until the result is displayed on the display (12), takes no more than 1 - 2 seconds. In this case, obviously, sampling is not required, since the analysis is carried out by a non-contact method due to reflected radiation (13) from a laser (2).

Approbation

On test samples, a photoluminescent analysis of the freshness of meat products (minced beef and minced pork) was carried out. For 5 days with an interval of 10 minutes, the photoluminescence spectra of minced beef and pork were recorded when stored at temperatures of -4°C, +4°C, +8°C, +22°C, +35°C.

It was found that meat stored for various periods of time at all temperatures studied can be characterized by one equivalent storage time at a temperature of +22°C. For example, storing a beef meat product at +8°C for 30 hours is equivalent to storing the same product at +22°C for 8 hours (see reference graph in FIG. 2).

From the graph in Fig.5 it can be seen that the dependence of the intensity on time in a double logarithmic scale of one of the characteristic lines of photoluminescence of the substance-indicator of bacterial contamination of protoporphyrin IX of a sample of pork meat at a temperature of +22°C for 100 hours is similar to Fig.2, and for fresh meat graph does not have burst peaks, which have rotten meat and smoked sausages.

From Fig.6, one can see a linear time dependence of the intensity of one of the characteristic lines of photoluminescence of a substance-indicator of bacterial contamination of protoporphyrin IX, synthesized during the life of bacteria, in a pork sample at a storage mode of +22°C on a double logarithmic scale.

Thus, it is not the absolute time of meat storage that is established, since the processes of decay and bacterial contamination occur at different rates at different temperatures, but the equivalent time is determined during which the meat product would be stored at a temperature of +22 ° C or at some other temperature beforehand. temperature set by the user. The choice of +22°C or lower temperature to determine the equivalent storage time is due to the fact that at these temperatures there was a monotonous growth of photoluminescence lines of protoporphyrin IX, which is an indicator of bacterial contamination of the studied meat food product, for a long time.

The photoluminescence spectrum of meat and meat products, excited by a violet laser, 405 nm, consists mainly of two broad lines (bands). One of them is in the blue-green region of the spectrum, 465-500 nm with a maximum near 480 nm, and does not change its intensity with time. The other band, in the yellow-red region, 560-750 nm with a maximum of about 640 nm, appears and intensifies as the meat products age. The main result of detailed studies of the luminescent analyzer for studying the quality and freshness of meat and meat products was the construction of graphs of the ratios of the intensities of the yellow-red and blue-green bands on the exposure time of test samples of various types of meat products at a temperature of 22 ° C for 5 days with a measurement interval of - 30 minutes. To assess the freshness of meat and meat products, there is no need to compare the photoluminescence spectrum of the tested product with the reference spectra from the database, which, of course, was built during the research. It suffices to extract from the resulting spectrum the value of the ratio of the intensities of the above pair of bands. From this value, you can find out from the corresponding graph what holding time at 22 ° C it corresponds to. In addition, it is possible to determine which category of product freshness this value corresponds to (as will be shown below using the example of Table 2).

Testing of the analyzer, made and functioning according to the invention, was carried out at the Moscow State Academy of Veterinary Medicine and Biotechnology - "MBA named after KI Skryabin".

The essence of the method and the operation of the luminescent analyzer were as follows: the photoluminescence spectra of fresh meat samples and meat aged at a certain temperature regime for a strictly specified time were formed and stored in a database of reference spectra; a quantitative analysis of the intensities of photoluminescence lines characteristic of bacterial processes of spoilage and putrefaction was carried out; the intensities of photoluminescence lines were compared with the reference lines from the database of reference spectra. Using the software, the storage time of the studied meat sample was set. Samples for analysis were packed in a material transparent to electromagnetic radiation in the visible spectral range or were placed in the open air. Study samples were minced meat, whole cuts of meat or ready-to-eat meat dishes. The resulting spectral indicators were put in correspondence with the scoring scale of organoleptic indicators of meat products according to GOST 9959-91 (Table 1).

Table 1. Organoleptic quality indicators of meat products on a 10-point scale

Grade
in
points Appearance Cut color Smell (aroma) Taste Consistency (tenderness, hardness) juiciness Overall quality rating nine Very
beautiful Very
beautiful Very
fragrant Very
delicious Very
gentle Very
juicy Excellent 8 Nice Nice Fragrant Delicious Gentle Juicy Very
good 7 Good Good Quite fragrant Tasty enough Gentle enough Enough
juicy Good 6 Not good enough Not good enough Not aromatic enough Not tasty enough Not tender enough Not juicy enough Above the average five Average (satisfactory) Average (satisfactory) Average (satisfactory) Average (satisfactory) Average (satisfactory) Average (satisfactory) The average 4 Slightly undesirable (acceptable) Uneven slightly discolored (acceptable) not expressed
(acceptable) A little
tasteless
(acceptable) A little stiff, loose (acceptable) Slightly dry, damp (acceptable) Below the average 3 Unwanted (acceptable) Slightly discolored (acceptable) A little nasty
(acceptable) Unpleasant,
tasteless (acceptable) Harsh, loose (acceptable) Dryish, damp (acceptable) Bad (acceptable) 2 Bad
(unacceptable) Bad
(unacceptable) Unpleasant (unacceptable) Bad
(unacceptable) Hard, loose
(unacceptable) Dry
(unacceptable) Bad (unacceptable) one Very bad
(unacceptable) Very bad (unacceptable) Very bad
(unacceptable) Very bad
(unacceptable) Very hard, very loose
(unacceptable) Very dry
(unacceptable) Very bad
(absolutely
unacceptable)

Sampling was carried out in accordance with GOST 9959-91. Samples were taken into clean, dry glassware. For delivery to the laboratory, vials with samples were packed in containers that ensured the safety of quality, constancy of temperature and humidity, and protected from sudden temperature changes and shocks.

When performing measurements, they followed the safety rules when working with fresh meat in accordance with GOST 9959-91, electrical safety requirements when working with electrical installations in accordance with GOST 12.1.019, as well as the requirements set forth in the technical documentation for measuring instruments.

The room complied with the fire safety requirements in accordance with GOST 12.1.004; it had fire extinguishing agents in accordance with GOST 12.4.009. The content of harmful substances in the air did not exceed the permissible values according to GOST 12.1.005. Organization of training of workers in labor safety in accordance with GOST 12.0.004.

When performing measurements, the following conditions were observed:

- ambient temperature (25±10)°C);

- relative air humidity (65±15)%;

- atmospheric pressure (760±60) mm Hg;

- or (1.01±0.08) 105Pa;

- mains voltage (220±11)V;

- constant laser radiation power 10 mW;

- exposure time 1 OOms.

In preparation for the measurements, the following work was carried out.

New and contaminated laboratory glassware, flasks, vials were sterilized in an autoclave by dry heat at 180°C for 1 hour.

Measuring instruments were prepared for operation in accordance with the instructions for their operation. The studied meat samples corresponded to GOST 9959-91.

Taking measurements.

In the device according to the invention, a blue laser with a wavelength of 405 nm was used, with which the luminescent emission of the studied meat samples was excited. All measurements were carried out at a constant radiation power of 10 mW and an exposure time of 100 ms every half an hour at a constant temperature and in the dark for 5–10 days. The vial was located at a distance of 2–5 cm from the spectrometer motionless during the entire measurement cycle. The recorded luminescence spectra were processed by software and presented in a normalized form in the form of graphs.

Luminescent analysis of the quality of meat food products (beef and pork) was carried out on test samples. For 5 days, with an interval of 30 minutes, measurements were made and the luminescence spectra of beef and pork meat stored at a temperature of +22°C were recorded. The photoluminescence spectra of fresh meat samples and meat aged at a certain temperature regime for a strictly specified time were formed and stored in a database of reference spectra. An unknown sample of meat was measured. A quantitative analysis was made of the intensities of photoluminescence lines characteristic of bacterial processes of spoilage and putrefaction. The intensities of photoluminescence lines were compared with reference lines from the database of reference spectra.

This method demonstrated that meat stored for varying lengths of time at all temperatures tested could be characterized by one equivalent storage time at +22°C. For example, storing a pork meat product at +8°C for 30 hours is equivalent to storing the same product at +22°C for 8 hours. Thus, not the absolute time of meat storage was set programmatically, since the processes of decay and bacterial contamination occur at different rates at different temperatures, but the equivalent time was determined during which the meat product would be stored at a temperature of +22 ° C or at some other temperature beforehand. temperature set by the user. The choice of +22°C or lower temperature to determine the equivalent storage time is due to the fact that at these temperatures there was a monotonous growth of specific luminescence lines of putrefactive bacteria for a long time. Using the software, the storage time, freshness, degree of bacterial contamination and the quality of the studied meat sample were determined.

The measurement results were recorded in a special journal. At the same time, information was given about the analyzed sample, measurement conditions, and the date of receipt of the measurement results.

Table 2. Results of the analysis of dependences of the ratio of the intensity of luminescence of the products of vital activity of anaerobic and aerobic bacteria

Meat categories Pork Beef steam room chilled frozen steam room chilled frozen 1 cat. freshness t=(0÷20)h
I=(0.2÷0.5) t=(0÷20)h
I=(0.2÷0.5) t=(0÷10)h
I=(0.2÷0.5) t=(0÷20)h
I=(0.2÷0.5) t=(0÷20)h
I=(0.2÷0.5) t=(0÷20)h
I=(0.2÷0.5) 2 cat. freshness t=(20÷100)h
I=(0.5÷0.8) t=(20÷50)h
I=(0.5÷0.8) t=(20÷100)h
I=(0.5÷2) t=(10÷50)h
I=(0.5÷0.8) t=(20÷100)h
I=(0.5÷0.8) t=(20÷100)h
I=(0.5÷2) 3 cat. freshness t > 100 h
0.8 < I < 2 t > 50 h
0.8 < I < 2 t > 50 h
I > 2 t > 100 h
0.8 < I < 2 t > 100 h
0.8 < I < 2 t > 100 h
I > 2

Based on the measurement results, the following graphs of the ratio of the intensity of the luminescence of waste products of anaerobic (in the range of 560÷750nm) (see Fig.3) and aerobic (in the range of 465÷500nm) bacteria (see Fig.4) were constructed.

The processes of actual meat decay were checked using ready-made RIDA COUNT test wipes containing a nutrient medium and a chromogenic substrate. The total chromogen luminescence signal from the entire area of the napkin carries information about the number of bacterial colonies grown. Examples of such informative napkins can be seen from Fig.7.

With the help of such control, burst growths of colonies of putrefactive bacteria (total microbial number - TMC) were revealed in the yellow-red region of the spectrum in the range of 560-750 nm with a maximum of about 640 nm, which arise and intensify as meat products age for 24 hours (see Fig. .8).

The results of measurements using test wipes are presented in table 3 and table 4.

Table 3
Beef (OMCH) Day Test wipes
RIDA COUNT
(COE/ml) Nutrient medium
(COE/ml) one 6* ¹⁰⁴ 1* ¹⁰⁵ 2 2* ¹⁰⁹ 2 * 10 ¹¹ 3 3 * 10 ¹¹ 1 * 10 ¹¹ 4 1 * 10 ¹³ 4 * 10 ¹² five 6* ¹⁰⁵ Table 4
Pork (MCH) Day Test wipes
RIDA COUNT
(COE/ml) Nutrient medium
(COE/ml) one 1* ^{104 4} *104 2 2* ¹⁰⁸ 2* ¹⁰⁸ 3 7 * 10 ¹¹ 2 * 10 ¹¹ 4 2* ¹⁰⁷ five 1* ¹⁰⁸ 2* ¹⁰⁷

Comparison with fresh meat was made visually by diluting meat swabs 10 times and counting bacterial colonies.

An example of such a comparison is shown in Fig. 9, where it can be seen that successive dilutions of washings from meat by 10 times and counting of bacterial colonies (samples A, B - pork, C - beef) clearly indicate the staleness of meat in comparison with the same washings from fresh meat (samples G - pork, D - beef).

Meat is divided into three categories of freshness: the first is fresh meat, the second is relatively fresh, and the third is stale. Any meat up to 20 hours of storage at 22°C is considered fresh, except for thawed pork, which becomes relatively fresh after 10 hours of storage. The second category of freshness of steamed and chilled pork and any beef lasts up to 100 hours of storage at a temperature of 22 ° C, and thawed pork meat deteriorates faster and becomes stale after 50 hours. Note that even once frozen pork spoils twice as fast as beef. The ratio of the luminescence intensities of the waste products of anaerobic (560-750 nm) and aerobic (465-500 nm) bacteria, exceeding a value of two, indicates that the meat was frozen at least once and anaerobic bacteria multiply there much faster during defrosting and the amplitude of the luminescence of waste products of these bacteria significantly exceeds the maximum achievable level of luminescence of bacterial waste products in meat without freezing. In steamed or chilled meat, the maximum achievable ratio of the luminescence intensities of the metabolic products of anaerobic and aerobic bacteria usually does not exceed the coefficient k = 1.5.

Correspondence of luminescent spectra and organoleptic indicators of meat quality: comparing our results with the database of reference spectra, we found that meat with a score of 9 to 7 points can be attributed to the first category, with scores of 6 to 4 points - to the second category, and with with estimates from 3 to 1 points - to the third category.

Claims (2)

1. A method for determining the freshness of meat, characterized in that it includes an express analysis by irradiating a controlled sample of meat with monochromatic laser radiation and subsequent analysis of the emerging fluorescent radiation in the fluorescence band, the results of which are used to judge the condition of the meat, while first forming and storing in database of reference photoluminescence spectra of fresh meat samples, then measure the controlled meat sample by irradiating it with a laser with a wavelength of 405 nm, which is directed through a set of bandpass filters in the range of 600-800 nm and a focusing system in the form of a lens in such a way that reflected from of a controlled sample of meat, the radiation fell on the spectrometer, which is located inside the casing, blocking the penetration of parasitic electromagnetic radiation in the visible range of third-party emitters, the radiation received by the spectrometer is detected and the quantitative value of the photoluminescence intensities is determined centive lines of protoporphyrin IX, as an indicator of bacterial contamination of controlled meat, lying in the region of red wavelengths of 600-800 nm, the obtained data are sent to compare the intensities of these photoluminescence lines with the intensity of the reference photoluminescent spectrum from the database of reference spectra, and the freshness of the controlled meat sample is determined based on from the correspondence of the intensity values obtained for these photoluminescence lines of the controlled meat sample to the intensity values of these photoluminescence lines, embedded in these reference spectra. 2. A device for implementing the method for determining the freshness of meat according to claim 1 in the form of a photoluminescent analyzer, characterized in that it consists of a protective casing of the body, configured to block parasitic electromagnetic radiation in the visible range of third-party emitters, inside which are located a power source, a laser with a length 405 nm wavelength, a focusing system in the form of a lens, a filtering system for detected radiation, consisting of a set of band-pass filters 600-800 nm, a spectrometer, which is connected to at least one detector of electromagnetic radiation in the visible range, which is connected to a signal processing controller, where the output of the latter connected to a control unit consisting of a microprocessor unit and a database of reference photoluminescence spectra of fresh meat samples, the microprocessor unit being connected to a display, a laser and a power supply unit.

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