RESEARCHING OF MEAT AND FAT COLOUR AND MARBLING IN BEEF

The studies of meat and fat colour and marbling in Longissimus dorsi of different cattle — beef-producing (Aberdeen-Angus, Hereford breeds) and dual-purpose (Simmental, Black-and-white breeds) — allowed to define groups by the colour values according to Lab international colour model. Measurements were performed 24 hours post-mortem between 12th and 13th ribs. It was found that different ranges of meat colour differed primarily in L* (lightness) and a* (redness) values, while b* (yellowness) values did not significantly differ. The highest differentiation between ranges of fat colour was noted in b* values, whereas L* and a* slightly differed. Moreover, visual assessment of beef marbling by four grades (small, moderate, good, and rich) and instrumental (microstructural) analysis using a computer image analysis system were carried out. The morphometric study of marbling was conducted in accordance with the principles of system quantitative analysis. To perform quantitative measurements, object analysis parameters (area) were specified. Both automatic and manual measurements of specified parameters were used. The study of Longissimus dorsi marbling established high agreement between visual and instrumental evaluations of marbling. Аннотация В результате исследований цвета мышечной и  жировой тканей и  мраморности на длиннейшей мышце спины (L. dorsi) крупного рогатого скота различного направления продуктивности  — мясного (породы абердин-ангус, герефорд) и мясо-молочного (породы симментальская, черно-пестрая) — определены группы по показателю цвета в международной цветовой модели Lab. Измерения проводили через 24 часа после убоя между 12 и 13 ребрами. Установлено, что различные диапазоны цвета мышечной ткани отличались прежде всего показателями *L (светлота) и *a (краснота), тогда как показатель *b (желтизна) изменялся не так значительно. Наибольшая дифференциация между различными диапазонами цвета жировой ткани отмечена по показателю b, тогда как показатели L и a отличались незначительно. Проводили также сравнение визуальной оценки мраморности говядины по четырем степеням (небольшая, умеренная, хорошая, насыщенная) с  приборным (микроструктурным) анализом с  применением компьютерной системы анализа изображений. Морфометрические исследования мраморности проводили в соответствии с принципами системного количественного анализа. Для проведения количественных измерений задавали параметры анализа объекта (площадь). Применяли как автоматическое, так и  ручное измерение заданных параметров. В результате исследования мраморности на длиннейшей мышце спины (L. dorsi) установлена высокая степень корреляции между визуальной и приборной оценками мраморности. УДК/UDC: 637.5.07:637.052 DOI 10.21323/2414-438X-2016-1-4-51-56 Введение Цвет является важным критерием качества, отображающим функциональные и технологические свойства мяса, и необходимым фактором для привлечения покупателя и коммерческого успеха. Кроме того, показатель цвета является индикатором многих физиологических, биохимических и технологических процессов. Окрашивание веществ в  определенный цвет происходит в  результате их взаимодействия с  видимой частью спектра электромагнитных волн (400–750 нм). Образование цвета мяса  — более сложный процесс, чем окрашивание неорганических веществ. Сложность обусловлена участием в  этом процессе молекулярного кислорода, четырехдентатного лиганда порфирина с  обширной системой спряженных двойных связей, иона железа Fe2+, способного окисляться, и других причин [1]. Introduction Colour is an important quality characteristic reflecting the functional and technological properties of meat and necessary factor for customer attraction and commercial success. Furthermore, the colour values indicate many physiological and biochemical processes. Certain colour of different substances is due to their interaction with visible part of the electromagnetic spectrum (400–750 nm). Meat colour formation is more complicated process compered to staining of inorganic substances. The complexity is due to the involvement of molecular oxygen, tetradentate porphyrin ligand with an extensive system of conjugated double bonds, oxidizable Fe2+ ions, and other

fered.Moreover, visual assessment of beef marbling by four grades (small, moderate, good, and rich) and instrumental (microstructural) analysis using a computer image analysis system were carried out.The morphometric study of marbling was conducted in accordance with the principles of system quantitative analysis.To perform quantitative measurements, object analysis parameters (area) were specified.Both automatic and manual measurements of specified parameters were used.The study of Longissimus dorsi marbling established high agreement between visual and instrumental evaluations of marbling.

Introduction
Colour is an important quality characteristic reflecting the functional and technological properties of meat and necessary factor for customer attraction and commercial success.Furthermore, the colour values indicate many physiological and biochemical processes.
Certain colour of different substances is due to their interaction with visible part of the electromagnetic spectrum (400-750 nm).Meat colour formation is more complicated process compered to staining of inorganic substances.The complexity is due to the involvement of molecular oxygen, tetradentate porphyrin ligand with an extensive system of conjugated double bonds, oxidizable Fe 2+ ions, and other factors [1].
Beef is an important meat type in human nutrition.According to the Ministry of Agriculture of Russian Federation, beef production grows in absolute terms every year.So, in 2015, in the structure of slaughtered cattle production in all categories of farms (2879.5 thousand tons), the proportion of specialized beef-producing cattle and crossbred cattle reached 451.4 thousand tons, which is 15.7%.During January-December 2015, the volume of industrial production of beef (including offal), amounted to 271.9 thousand tons (11.0 thousand tons higher compared to corresponding period of 2014) [4].The increase in livestock population of specialized breeds and their crossbreeds is stimulated by subsidizing from the budgets of all levels [5].
Currently, the interest of Russian companies in the production of high quality beef increases every year.Growing and fattening of young beef-producing cattle allows businesses in the Russian market to receive high quality products that meet the most stringent international standards, and to move confidently in the direction of imported beef substitution with domestically produced meat.However, an extremely important question is the objective evaluation of beef and its further use depending on quality parameters and technological properties.
All over the world, there is a long established practice of beef evaluation by the colour of muscle and fat tissue, as these indicators provide an objective view of meat quality.In addition, their measurement is easily carried out in the conveying system at the stage of half carcass separation into quarters during cutting and deboning.Based on meat colour and marbling, beef value can be predicted, both for industry and for the consumer [6].Since 2007, Australia, which is considered one of the recognized leaders in the production of high quality beef, have established uniform standards of meat and fat colour and marbling [7].In Canada, beef grading system according to colour indicators was established in the 80s of XX century and is constantly и постоянно совершенствуется для повышения объективности и наилучшего соответствия предпочтениям потребителей [8].
being improved to enhance the objectivity and meet consumer preferences the best way [8].
However, as demonstrated by our preliminary study of existing world practice of beef standardization, there are no uniform world standards of meat and fat colour and marbling.This is due to national aspects of cattle breeding and fattening, as well as various preferences of consumers.
In this connection, there is a need to develop standards of meat and fat colour and marbling applicable to Russian market conditions, taking into account the aspects of cattle breeding and beef production, on the basis of which objective and reliable rapid methods for evaluating beef quality will be subsequently established.

Materials and methods
To determine meat and fat colour in a production environment, Konica Minolta CM-2300d spectrophotometer (Japan) was used.
Since the visual colour evaluation is strongly influenced by the light source and viewing angle [9,10], all measurements were carried out with D65 light source (standard daylight) and observation angle of 2°.Each measurement was performed twice, and the result was the average of two measurements.

Statistical analysis of data was performed using MS
Excel and IBM SPSS Statistics software.
Measurements were carried out in Longissimus dorsi of different young (up to 24 months) cattle -beef-producing (Aberdeen-Angus, Hereford breeds) and dual-purpose (Simmental, Black-and-white breeds).Measurements were carried out between the 12th and 13th ribs.Overall, more than 150 measurements of muscle tissue colour were carried out, as well as more than 100 measurements for fat colour.All measurements were taken 24 hours post-mortem.The measurements were used to determine the colour grades of meat and fat, which are characteristic of Russian beef, and to establish average (standard) values for each grade.
The comparison was carried out for visual assessment of beef marbling by four grades (small, moderate, good, and rich) and instrumental (microstructural) analysis using AxioVision 4.7.1.0computer image analysis system adjusted for histological studies.

Results and discussion
As a result of data mathematical processing on the basis of average values, five grades of meat colour and four grades of fat colour were determined in Lab system, which are presented in Figure 1 and Table 1.
It was found that meat colour values differ between grades primarily by L* (lightness) and a* (redness), whereas b* (yellowness) values varied not significantly.As a result, the calculation of percent difference determined that the difference in L* (lightness) between grades 1 and 5 is 69.05%, as well as the difference in a* is 64,0%, and in b* is 45%.Colour difference dE between each two neighbouring grades was 5 or more, which is sufficient for perception by the human eye, as the average colour difference dE recognizable by human is 3-4 units and more.
According to Benjamin W. B., Holman et al. [11], comparison of the instrumental analysis of beef colour with consumer preferences revealed the dependence of preferences on L* and b* values, whereas variations in a* values did not significantly influence the visual beef assessment by consumers.R. A. Mancini and M.C.Hunt [12] in a review of existing colour evaluation methods (visual and instrumental) of meat stated that the greatest variations in meat colour were caused, first of all, by variations in L* (lightness) values.R. Morales, A. P. S. Aguiar et al. [13] in their work based on the interview of 204 consumers made similar conclusions that preferences vary most of all with the difference between L* values.
As a result of mathematical processing of data obtained during the experimental work in the conditions of Russian meat-processing enterprises, fat colour standards were identified (Table 2).
The results obtained (Table 3) were transferred to other software programs for further statistical processing.
The findings suggest the agreement between visual assessment and instrumental (microstructural) analysis of marbling and the potential application of both methods in industry.

Figure 1 .
Figure 1.The graph of colour values distribution Рис. 1. График распределения показателей цвета difference determined that L* (lightness), a* (redness), and b* (yellowness) values varied between grades 1 and 4 by 10.02%, 100.0%, and 640.0%, respectively.Similar results were obtained by K. Chen et al. in a computer study of fat colour in beef grown in Asian countries [14].During the study of quality indicators of fat in Irish cattle, A.P. Moloney, M.T. Mooney et al. revealed variations in b* values, fatty acids content and sensory properties of fat with different colour characteristics [15].
Average values (L*, a*, b*) for each range of meat and fat colour from different young (up to 24 months) cattle were established.High agreement was shown for visual assessment and instrumental (microstructural) analysis of marbling allowing the possibility of standards implementation to determine the beef quality by this parameter.