Allele frequencies and genotypes of kappa casein (CSN3) and their association with chemical composition and coagulation properties of milk in Brown cattle

The aim of the present study was to evaluate allele frequencies and genotypes of kappa casein (CSN3) and their association with milk quality and coagulation properties in Brown cattle. Milk proteins’ polymorphism was found out in 155 tissue samples from cows reared at 4 farms. The analysis of milk composition was done in the lab of the Agriculture Institute – Stara Zagora on Lactoscan ultrasound milk analyzer, whereas coagulation properties of individual milk samples were evaluated on a Computerized Renneting Metter – Polo Trade, Italy. Milk samples were obtained by milk meters. The milk was analysed within 3 hours after sample collection. Naturen Plus 215/0.8L chymosin was used, with milk coagulation activity of 215 IMCU/ml. During the study, the following parameters were studied: milk fat and protein contents (%), rennet coagulation time (RCT, min), curd firmness (а30, mm) and curd firming time (k20, min). Kappa casein (CSN3) is characterised by five genotypes – АА, АВ, ВВ, АН and ВН, the frequency of which varied within various ranges. The milk of cows with genotype AB was characterized by the highest content of fat and protein: 4.85% and 5.00%, respectively. The milk of heterozygous cows from genotype AB demonstrated the longest rennet coagulation time – 18.04 min. The animals carrying the H allele produced milk with the highest curd firmness – 37.00 mm.

Effect of Protein Genotypes on Physicochemical Properties and Protein Functionality of Bovine Milk: A Review

Milk protein comprises caseins (CNs) and whey proteins, each of which has different genetic variants. Several studies have reported the frequencies of these genetic variants and the effects of variants on milk physicochemical properties and functionality. For example, the C variant and the BC haplotype of αS1-casein (αS1-CN), β-casein (β-CN) B and A1 variants, and κ-casein (κ-CN) B variant, are favourable for rennet coagulation, as well as the B variant of β-lactoglobulin (β-lg). κ-CN is reported to be the only protein influencing acid gel formation, with the AA variant contributing to a firmer acid curd. For heat stability, κ-CN B variant improves the heat resistance of milk at natural pH, and the order of heat stability between phenotypes is BB > AB > AA. The A2 variant of β-CN is more efficient in emulsion formation, but the emulsion stability is lower than the A1 and B variants. Foaming properties of milk with β-lg variant B are better than A, but the differences between β-CN A1 and A2 variants are controversial. Genetic variants of milk proteins also influence milk yield, composition, quality and processability; thus, study of such relationships offers guidance for the selection of targeted genetic variants.

Influence of k-casein genotype on heat stability and cheese making properties of milk powder

In this study the effect of k-casein gene polymorphism on the technological characteristics of milk powder obtained by spray (AA1:BB1) and freeze drying (AA2:BB2) was investigated. Standardized and generally accepted methods were used in the field of physical and chemical control of dairy products, as well as methods for assessing the heat stability and cheese making properties of milk. The most heat-resistant were the samples with a predominance of milk obtained from cows with the AA CSN3 genotype, in the pH range from 6.4 to 7.0 (36-91 minutes for AA1:BB1 and 37-101 minutes for AA2:BB2). In systems with a fraction of 25 % to 100 % of milk from cows with the AA CSN3 genotype obtained by freeze drying, higher (by 3-10 %) stabilization qualities of protein were revealed when heated in the pH range from 6.4 to 7.0 compared to spray drying. The analysis of the results regarding the cheese making properties showed that with an increase in the proportion of milk from cows with the BB CSN3 genotype from 0 % to 100 % in model systems, the rennet coagulation time decreases for all samples, regardless of the drying method. It was also found that when using freeze drying, coagulum of all samples were assigned to the highest class of milk quality in terms of cheese making properties, while during spray drying only the samples consisting of min. 75 % or completely of milk obtained from cows with genotype BB CSN3 corresponded to this category.

Methods of Assessing Milk Proteins Coagulation as a Part of the Forecasting System of Technological Properties

Introduction. An integrated monitoring of raw milk’s contents, quality, and security is a key factor that guarantees the high-quality dairy production. As a result, new research methods of rennet clotting are a topical and urgent area of study. The research objective was to systemize and analyze the basic criteria and assessment methods of rennet-induced protein gels in milk systems. Study objects and methods. The authors reviewed the official Russian criteria and methods of raw milk assessment by its rennet coagulation properties. The research also featured the most widespread instrumental approaches used in best practices from around the world. Results and discussion. In Russian and foreign cheese production, milk is always tested for its physicochemical and microbiological indicators, with a mandatory check of its coagulation characteristics. Russian cheese-makers use different modifications of rennet and rennet-fermenting tests based on subjective sensory evaluation, while international scientific trends in this area aim at developing and improving instrumental methods by using a complex indicator MCP. This indicator characterizes the parameters of rennet coagulation with the help of such devices as Formagraph, Lattodinamografo, Optigraph, etc. Formagraph is a simple instrument for measuring rheological properties of milk clotting. It was popular in the late XX century. The resent years saw the development of other methods of instrumental control, including those based on optical measurements. For instance, Ortigraph is one such instrument that receives unified data on coagulation properties of raw milk by using near-infrared waves. Sensory and instrumental methods have their advantages and disadvantages. However, the most significant criteria for a quick test of cheeseability, yield, and quality are the speed of analysis and the comparability and reproducibility of results. Conclusion. To improve cheeseability testing, Russian cheese-makers need to use the international experience, which offers standardized evaluation criteria in combination with various instrumental approaches. However, the integration of foreign regulations and methods into Russian studies is not the only option. The improvement and development of national instrumental methods of evaluating milk protein coagulation is also crucial.

Development of methodical approaches to assessing the formation of rennet-induced milk gels using the method of rotational viscometry

Формирование структуры сычужно-индуцированных молочных гелей, имеющее первостепенное значение в производстве целого ряда продуктов, наиболее объективно может быть охарактеризовано исключительно посредством инструментального измерения реологических параметров. В статье представлены результаты эксперимента по определению способности молочных систем с различной концентрацией сухих веществ к сычужному свертыванию с использованием ротационной вискозиметрии. Метод базируется на анализе изменений динамических показателей вязкости в процессе коагуляции молока, а также его УФ- и НФ-ретентатов с использованием вискозиметра Brookfield с последующей сравнительной графической оценкой кинетики гелеобразования и пиковой вязкости образующихся сгустков. Полученные данные подтвердили эффективность предлагаемых методических подходов для сравнительной оценки способности к сычужной коагуляции молока и его концентратов, полученных разными способами баромембранной обработки, и выявили перспективные направления исследований по изучению активности и дозировок молокосвертывающих препаратов, а также по выбору оптимальных температурно-временных режимов сычужной коагуляции молочных систем с прогнозированием их структурно-механических параметров. Rennet-induced milk gels are crucial for the production of a number of products. The formation of their structure can be objectively characterized only with the use of instrumental measurements of rheological parameters. The article presents the results of the experiment on determining the ability of milk systems with different dry substances concentration to rennet clot using rotational viscometry. This method is based on the analysis of changes in the dynamic viscosity indicators during the milk coagulation and its UV and NF retentates, followed by a comparative graphical assessment of the gelation kinetics and maximum clots viscosity. In our experiment, we used Brookfield viscometer. The presented data confirmed the effectiveness of the proposed methodological approaches for the comparative assessment of the ability to rennet coagulation of milk and its concentrates obtained by different methods of baromembrane treatment. A great prospect has been obtained in studies on the study of the activity and doses of milk-clotting enzymes and, the selection of the optimal temperature-time regimes of rennet clotting of milk systems with the prediction of their structural and mechanical parameters.

COMPARATIVE ASSESSMENT OF MILK PROTEIN COAGULANTS OF DIFFERENT ORIGIN

Потребность в увеличении количества и качества производимой молочной продукции стимулирует исследования, направленные на повышение эффективности переработки молочного сырья, что, в свою очередь, невозможно без изучения технологических свойств молока и функционально необходимых ингредиентов, применяемых в производстве различной молочной продукции. На основе научно-технической информации международных и российских баз данных, систематизированной в рамках изучаемой тематики, представлен обзор научных работ о коагулянтах белков молока различного происхождения, применяемых при кислотной, кислотно-сычужной и сычужной коагуляции. Установлено, что в российской и международной производственной практике востребованы коагулянты животного, микробного и рекомбинантного происхождения. Наибольшим спросом среди коагулянтов животного происхождения пользуется химозин, получаемый из желудков телят. Ферменты микробного и рекомбинантного происхождения отличаются более стабильным качеством и низкой стоимостью, но их производство, основанное на методах генной инженерии, вызывающих предубеждение у большинства потребителей, практически полностью сосредоточено за рубежом. При условии повышения лояльности потребителей ферменты рекомбинантного происхождения могут стать наиболее перспективными функциональными ингредиентами. Исследования потенциала различных протеолитических ферментов растительного происхождения выявили невысокий технологический эффект их применения. Рассмотренный материал позволяет прогнозировать перспективность научных исследований по выявлению механизмов коагуляции молока и новых эффективных и универсальных коагулянтов совокупно с селекционной практикой отбора животных, направленной на улучшение технологических свойств молочного сырья. The need to increase the quantity and quality of dairy products encourages research aimed at improving the efficiency of processing dairy raw materials, which, in turn, is impossible without studying the technological properties of milk and functionally necessary ingredients used in the production of various dairy products. On the basis of scientific and technical information from international and Russian data bases, systematized within the framework of the subject under study, a review of scientific works on milk protein coagulants of various origins used in acid, acid-rennet and rennet coagulation is presented. It is established that coagulants of animal, microbial and recombinant origin are in demand in the Russian and international production practice. The greatest demand among coagulants of animal origin is chymosin, obtained from the stomachs of calves. Microbial and recombinant enzymes are characterized by more stable quality and lower cost, but their production, based on genetic engineering methods that cause prejudice among most consumers, is almost entirely concentrated abroad. If consumer loyalty is increased, recombinant enzymes may become the most promising functional ingredients. Studies of the potential of various proteolytic enzymes of plant origin revealed a low technological effect of their use. The considered material allows us to predict the prospects of scientific research to identify the mechanisms of milk coagulation and new effective and universal coagulants together with the breeding practice of animal selection, aimed at improving the technological properties of dairy raw materials.