There is only one freshness
How to recognize a meat fake?
Irina Palchikova, Diana Khomyakova, "Science in Siberia"Photo: Diana Khomyakova
Scientists from KTI NP SB RAS and FTI SB RAS managed to find new approaches to determining the quality of meat. The integral estimation method created by them uses the electrical polarization characteristics of the raw material, its color, as well as reflection coefficients at various wavelengths.
Recognizing the quality of meat (as, indeed, any other food product) is vital for people. Sensory assessments of the sensory organs, such as the consistency, taste, smell and appearance of the sample, help us to determine it.
The classic of Russian culinary literature, Elena Molokhovets, back in 1861, in her famous book "A Gift to young housewives" advises: "Good fresh beef should not be: 1) neither pale scarlet nor rich red, because the first is a sign of illness, and the second indicates that the animal was not killed, and died with all the blood preserved, or that it suffered from acute fever."
"More than a hundred years have passed since that time, the way of fattening and raising livestock has changed, in fact, meat has already turned into raw materials, and color is still able to play the role of quality assessment. Only now it is based not on subjective human perception, but on the impartial accuracy of computer vision that distinguishes the smallest shades," says Irina Georgievna Palchikova, head of the laboratory of laser precision Systems, Doctor of Technical Sciences, KTI NP SB RAS.
Within the framework of an interdisciplinary integration project led by the director of KTI NP SORAN, Doctor of Technical Sciences Yuri Vasilyevich Chuguya (and initiated by the director of the Center for Information and Computing Support of SB RAS, Doctor of Technical Sciences Alexander Fedorovich Aleynikov), employees of the Physics and Technology Institute of SB RAS and the Design and Technology Institute of Scientific Instrumentation SB RAS studied the possibility of using color characteristics to assess the quality and category of meat raw materials. The result of the research was the creation of a portable autonomous color analyzer and a specialized program with a user-friendly interface that allows you to determine the significant characteristics of the product.
The technique works as follows: raw meat is photographed, and then its digital image is subjected to mathematical processing. Specific values of color characteristics correspond to different degrees of freshness. There are no analogues of this type of analyzer on the Russian market yet.
The issue of the accuracy of color determination is of great importance in many areas of modern human activity: in cameras, scanners, in the processing of satellite photographs, in sorting and recognizing objects in technical systems, in expert assessments of works of art, in criminology. Despite the fact that many publications are devoted to it and at first glance it seems to be quite studied, digital image processing algorithms that allow increasing the reliability and accuracy of calculating the color difference between samples have not yet reached perfection. Take, for example, the Zelenka experience, popular in Akademgorodok, which is annually demonstrated to students of the SUNC NSU and students of the Faculty of Physics, as well as to everyone who just wants to attend the Days of Science at the university. The trick here is that the visually determined color of the substance shown depends on its thickness: in dense layers, the solution has a red color, and in thin layers – green. When you try to capture this perfectly visible effect on the camera, you fail. At best, the purple hue will barely break through, and you need to have considerable imagination to describe the result of the experience. Well, or, of course, to "touch up" the picture a little specially.
Why does the color of meat depend on its quality? This property is due to the pigments of complex proteins. In fresh raw materials, under the influence of oxygen, they are represented by dark red myoglobin, bright red oxymyoglobin and brown oxidized metmyoglobin, which pass into each other. Over time, the second of them, indicating the freshness of the product, becomes the third due to the reaction with oxygen and gives the product an unattractive earthy or dark brown hue.
"Today, the issue of the targeted use of meat raw materials, taking into account the course of autolysis, is of particular importance, because the proportion of animals coming for processing from industrial complexes (both domestic and foreign) has significantly increased, in which, after slaughter, significant deviations from the usual development of autolytic processes are found in the muscle tissue. This is due to the conditions of keeping livestock (which has already turned into a kind of "raw material", ceasing to be animals), and with special methods of fattening and treatment (the main task of industrial cattle breeding complexes is to increase the maximum amount of muscle mass in as short a time as possible), – says Irina Georgievna. "In this regard, the food industry is facing the urgent task of rapid analysis of meat in order to objectively divide it into three categories: PSE (pale, soft, watery), Norm (normal) and DFD (dark, hard, dry)."
These qualities are not always detected by color analysis, therefore, within the framework of the integration project, scientists have also studied the possibilities of impedance spectroscopy. This method is based on passing weak alternating currents of various frequencies through the test sample and measuring its impedance (electrical conductivity). In the process of autolysis, with the increase of tissue degradation processes, the size of their intercellular spaces is reduced. This affects the permeability of the membranes, which begin to break down and the resistance changes. With the help of impedance spectroscopy, it is possible to determine various indicators of the quality of raw materials (moisture content, fat, and others) even before the slaughter of the animal.
Scientists were able to detect frequency intervals at which violations of the classical course of autolysis are detected. This effect manifests itself in a specific change in the dynamics of the electrical conductivity of the studied samples. So, it turned out that in meat of the PSE and DFD categories, it differs from a monotonically decreasing dependence on the frequency of raw materials of the NOR category. The revealed patterns make it possible to create a sensor for express diagnostics of the quality of meat raw materials.
"The colorimetric device has already been made, and as far as impedance measurement is concerned, we are currently in the process of development: we are creating a convenient cuvette, electronic and software part. I think we will have a sample soon," Irina Palchikova notes.
The next step in the development of the project will be the testing of devices directly at enterprises. "In the past three years, the raw materials for experimental work were prepared on the basis of FTI with RAS. Very fruitful contacts have been established with the Berdskaya poultry farm, where research has been conducted for many years to replace antibiotics and chemical preparations (without which poultry farming and egg production would be impossible) with a probiotic based on lactic acid bacteria," says Irina Georgievna.
One of the primary tasks of the colorimetric method is the development of a database. Even the usual doctor's sausages made by different companies are at least a little different from each other, and for each of them it is necessary to create their own color "spectrum of quality".
The devices that Novosibirsk scientists are working on will be useful to manufacturers interested in ensuring that their product meets European standards, catering companies wishing to control the quality of suppliers' goods, and, in the end, ordinary consumers who care about their health. Thus, it has been experimentally proven that the method of impedance spectroscopy distinguishes the meat of laying hens and broilers, determines the exact age of eggs, reveals a stale and low-quality product disguised with the help of various tricks (like tinting).
Portal "Eternal youth" http://vechnayamolodost.ru13.02.2015