Milk Coagulation Research Articles

CONTENT OF MACRO- AND MICROELEMENTS IN CHEESES PRODUCED WITH THE ADDITION OF DIFFERENT SPICES

<p>Cheese is a dairy product used directly for human consumption or indirectly as an ingredient of other foods or ready meals. Being an extremely valued product, cheese is a concentrated source of proteins, vitamins and minerals, especially calcium, phosphorus and magnesium. Various spices are used to enhance the taste of food, which also have numerous medicinal properties. The aim of this study was to examine the effect of the addition of different spices on the mineral composition of cheeses, obtained by heat-acid coagulation of milk. There were six different samples of cheese produced in the milk processing plant (mini cheese factory). The first sample was taken as a control one, with no addition of spices, and the other five were produced with 0.5% addition of different spices (oregano, basil, parsley, rosemary, and chives). The total ash content and the content of macro- and microelements were determined in the tested cheese samples. It was established that the addition of different spices has a statistically significant (p<0.05) effect on the content of macro- and microelements in the produced cheeses. The total content of macro-elements ranged from 612.55 mg/100g to 811.81 mg/100g, of which sodium had the largest share (from 293.61 mg/100g to 389.20 mg/100g), as well as calcium (from 74.13 mg/ 100g to 278.12 mg/100g). The total content of microelements in the tested spice-containing cheeses ranged from 7.317 mg/100g to 9.360 mg/100g, of which the most abundant was zinc, the content of which was between 5.903 mg/100g and 7.351 mg/100g.</p>

Some enzymatic properties of lactic acid bacteria isolated from dairy products

This article presents data on the study of physiological and biochemical properties, antagonistic and enzymatic activity of lactic acid bacteria isolated from dairy products.9 types of lactic acid bacteria were studied:Lactobacillus bulgaricus GM – 08, Lactobacillus bulgaricus KZh – 01,Lactobacillus bulgaricus GS – 03, Lactococcus cremoris – 6, Lactococcus cremoris – 17, Lactococcus cremoris – 26, Lactococcus lactis – 1,Lactococcus lactis – 15, Lactococcus lactis – 23. These strains were found to have resistance to 2% and 4%-vertical NaCl concentrations, bile and phenol.In addition, the antagonistic activity of Gram-positive and Gram-negative microorganisms in relation to test cultures of Staphylococcus aureus, Salmonella dublin, Escherichia coli, Bacillus subtilis, Sarcina flava was studied.All studied lactic acid bacteria showed activity in Test cultures with different inhibition zones. The Lactococcus lactis – 23 strains showed high activity for all cultures, with an inhibition zone of 17-25 mm.Further, 5 strains were selected from these strains and their aroma-forming properties, the formation of diacetyl and ammonia from arginine, hemolytic and lecithinase activity were studied.Compositions were compiled from these strains to make yeast.The compatibility of strains of lactic acid bacteria was checked with each strain individually and with the duration of milk clotting according to organoleptic indicators compared to the duration of milk clotting.Thus, the most active clot formation was obtained by the Lactococcus lactis – 23 strainof the selected combinations.

Comprehensive bioinformatics-based annotation and functional characterization of bovine chymosin protein revealed novel biological insights

Chymosin, an aspartic protease present in the stomachs of young ruminants like cows (bovine), causes milk coagulation and cheese production through the breakdown of κ-casein peptide bonds at the Met105-Phe106 site. Bovine chymosin is first synthesized as a pre-prochymosin that is cleaved to produce the mature chymosin protein. Despite significant strides in research, our understanding of this crucial enzyme remains incomplete. The purpose of this work was to perform in silico evolutionary and functional analysis and to gain unique insights into the structure of this protein. For this, the sequence of Bos taurus chymosin from UniProt database was subjected to various bioinformatics analyses. We found that bovine chymosin is a low molecular weight and hydrophilic protein that has homologs in other Bovidae species. Two active sites of aspartic peptidases, along with a functional domain, were identified. Gene Ontology analysis further confirmed chymosin's involvement in proteolysis and aspartic endopeptidase activity. Potential disordered residues and post-translational modification sites were also uncovered. It was revealed that the secondary structure of bovine chymosin is comprised of beta strands (44.27%), coils (43.65%), and alpha helices (12.07%). A highly optimized 3D structure was also obtained. Moreover, crucial protein–protein interactions were unveiled. Altogether, these findings provide valuable insights that could guide future research on bovine chymosin and its biological roles.

USE OF FERMENTED ACID WHEY ENRICHED WITH MINERAL ELEMENTS IN THE TECHNOLOGY OF RYE-WHEAT BREAD

This article investigates the use of fermented acid whey enriched with mineral elements (magnesium, zinc, and manganese) in the technology of rye-wheat bread. Whey obtained through thermal acid coagulation of milk is a valuable resource that can significantly enhance the quality and nutritional value of bakery products. The study analyzes scientific approaches to enriching whey with mineral elements through spark discharge treatment, which creates optimal conditions for cultivating lactic acid bacteria. The primary aim of the study is to examine the fermentation process of whey enriched with mineral elements and its impact on the rheological properties of dough and the quality of finished bakery products. It has been established that spark discharge treatment of whey significantly accelerates the fermentation process, increases acidity, and boosts the growth of lactic acid bacteria. The research shows that using enriched whey allows the fermentation time to be reduced by almost half compared to the control. This is achieved through intensive acid production and biomass growth of lactic acid bacteria. The best results were obtained with whey treated with spark discharges in a conductive layer of zinc, magnesium, and manganese granules. Using fermented whey in the production of ryewheat bread contributed to increasing the gas-forming capacity of the dough, improving its rheological properties, and increasing the specific volume of finished products. Enriched whey also positively affected the bread's quality by enhancing its porosity, shape stability, and organoleptic properties. It was found that enriching whey with magnesium, zinc, and manganese not only intensifies the fermentation process but also increases the nutritional value of the finished products by enriching them with important microelements. The study demonstrated that using enriched whey reduces dough ball spread, increases its elasticity and resilience, and extends the bread's freshness. The research results confirm the feasibility of using spark discharge enrichment of whey with magnesium, zinc, and manganese to improve the efficiency and quality of bakery production. The proposed technology can be recommended for widespread implementation in production, ensuring high quality and competitiveness of bakery products in the market.

Estimating the Effect of the Kappa Casein Genotype on Milk Coagulation Properties in Israeli Holstein Cows.

In Israel, about 26% of produced milk is used to produce hard cheeses and 29% for soft cheeses. Milk with preferred coagulation properties requires a shorter coagulation time and yields a higher curd firmness than milk with inferior coagulation properties. Studies have shown that milk from cows with the B allele of kappa casein (κ-CN) produces more cheese than milk from those with A and E alleles. There is evidence that milk from AE or EE genotype cows is unsuitable for cheese production. In the early 1990s, the proportion of the B allele in Israeli Holstein cattle was about 17%, similar to its prevalence in the Holstein population worldwide. In recent years, however, its proportion has increased to about 40%. We analyzed milk coagulation properties as a function of the cow's κ-CN genotype, including time in minutes until the beginning of coagulation and curd firmness after 60 min-measured in volts via an optigraph device and scored on a scale of 0-4 by a laboratory technician. Cow selection was based on their sire's genotype, so that there would be sufficient genotypes that include the rare E allele. A total of 359 cows were sampled from 15 farms: 64 with genotype AA, 142 with AB, 41 with AE, 65 with BB, and 47 with BE. Data were analyzed via the general linear model procedure of SAS. We found the following: (a) There were significant differences between genotypes for optigraph-measured curd firmness. In a multi-comparison test, the BB genotype gave the highest curd firmness, and AB and BE showed a significant advantage compared to AA and AE (9.4, 8.6, 8.4, 6.9, 6.8 V, respectively). Assuming a frequency of about 55% for the A allele, about 30% of the milk delivered to dairy plants comes from AA cows. (b) There was a significant difference between the genotypes in technician-observed curd firmness, with BB scoring significantly higher than AA and AE. (c) The optigraph-measured curd firmness was significantly higher for milk from primiparous cows as compared to milk from second, third, or fourth lactation cows (8.9, 7.8, 7.9, 7.7 V, respectively). The technician-observed curd firmness was significantly higher for primiparous vs. multiparous cows. There was a clear advantage in curd firmness for genotypes that included the B allele compared to those with AA and AE genotypes. We can increase the proportion of the B allele in the population by insemination of cows using bulls with the genotypes AB and BB. This factor should therefore be included in the selection index.

Streptococcus ruminantium-associated sheep mastitis outbreak detected in Italy is distinct from bovine isolates

Streptococcus ruminantium is the causative agent of several bovine and ovine diseases, however reports are uncommon and application of whole genome sequencing to identify is rare. We report for the first time, a severe ovine mastitis outbreak caused by S. ruminantium in Italy, 2022. S. ruminantium was isolated from 12 adult lactating ewes with diffuse nodules in the mammary parenchyma and predominantly serous and clotted milk. All outbreak isolates, along with five additional historical Italian isolates (between 2011 and 2017), were genomically characterised and then analysed in the context of all publicly available S. ruminantium genomes. Antimicrobial susceptibility testing was performed to determine the MICs of 16 antibiotics. The results showed that all isolates were susceptible to all antimicrobials tested except kanamycin. Single Nucleotide Variant analysis confirmed this as a clonal outbreak across 10 sheep (≤ 15 SNVs), while the two others were colonised by more distantly related clones (≤ 53 pairwise SNVs), indicating the presence of multiple infecting lineages. The five historical S. ruminantium isolates were comprised of genetically-distant singletons (between 1259 and 5430 pairwise SNVs to 2022 outbreak isolates). Ovine isolates were found to be genetically distinct to bovine isolates, forming monophyletic groups. Bovine isolates were similarly made up of singleton clones in all but two isolates. Taken together, our genomic analysis using all globally available genomes is consistent with general opportunistic pathogenesis of S. ruminantium. We encourage future genomic surveillance efforts to facilitate outbreak detection, as well as improve our understanding of this poorly-understood, multi-host, zoonotic pathogen.

Elemental composition of salt and vulnerability assessment of saline groundwater sources selected based on ethnoarchaeological evidence in Romania

The study aimed to evaluate the elemental composition of salt extracted from shallow to saline groundwater sources selected based on ethnoarchaeological evidence in the Eastern Carpathians and Sub-Carpathians area of Romania and to assess their specific vulnerability using groundwater pollution potential (DRASTIC and DRASTIC-LU methodology). 198 saline water samples were collected from different site types, including natural saline springs, catchment saline springs, brine wells, salted lakes and ponds, during the period between 2007 and 2019. Scanning electron microscopy with energy-dispersive X-ray spectroscopy was employed to characterize the elemental composition of salt after dry-evaporating a predetermined volume of each collected sample. The results indicated that the salt concentration in the brines ranged from 0.1% to 41.3%, with the highest concentration found in wells and natural saline springs. The dominant component was sodium chloride, but several sites had high concentrations of potassium chloride, which is essential for human health. Over 95% of the analyzed samples also contained other minerals like calcium and magnesium, further highlighting the health benefits of these brine sources. However, two sites were slightly contaminated with heavy metals, posing potential health risks if consumed. The DRASTIC index, a standardized system for evaluating groundwater pollution potential, gave scores between 99 and 208, indicating moderate to very high intrinsic pollution potential. Similarly, the DRASTIC-LU index, which takes into account and the land use aspects, showed scores ranging from 114 to 258, suggesting low to very high vulnerability to contamination. These findings provide valuable information on the elemental composition of salt and the vulnerability of these brine sources, which are still used by rural communities for traditional practices like meat and fish preservation, milk curdling, and pickling. The study has important implications for sustainable management from both ethnoarchaeological and economic perspectives.

Improvement of camel milk-clotting: Usefulness of crude extract from green pods of carob (Ceratonia siliqua. L) as a substitute for commercial rennet.

Camel milk transformation into cheese remains an objective to be improved today. This study aimed to improve camel milk clotting using a crude extract from green pods of carob as a substitute for commercial rennet. The composition of the crude carob extract was determined for dry matter and protein content. Milk clotting conditions were studied at different temperatures, pH and CaCl2 concentrations. Milk clotting properties were assessed by milk clotting activity, specific activity and proteolytic activity. Enzymatic hydrolysis of camel milk caseins by crude carob extract and its inhibition were demonstrated by SDS-polyacrylamide gel electrophoresis. Crude carob extract analysis showed a protein and dry matter content of 23.26±0.5 mg/ml and 30.66±0.5 g/l, respectively. Optimal milk clotting activity was observed at 53.6 °C, pH 4.5, and 0.09 M CaCl2. The crude carob extract showed a high milk clotting activity (4.97 U/ml) and a low proteolytic activity (0.04U/ml) with camel milk. The cheese yield of curd produced from camel milk using crude carob extract was the highest (23.95%) compared with that of Camel chymosin (20.5%). The high ratio of milk-clotting to proteolytic activity shows the potential of this extract as a substitute for commercial rennet in the dairy industry.

In-Line Detection of Clinical Mastitis by Identifying Clots in Milk Using Images and a Neural Network Approach.

Automated milking systems (AMSs) already incorporate a variety of milk monitoring and sensing equipment, but the sensitivity, specificity, and positive predictive value of clinical mastitis (CM) detection remain low. A typical symptom of CM is the presence of clots in the milk during fore-stripping. The objective of this study was the development and evaluation of a deep learning model with image recognition capabilities, specifically a convolutional neural network (NN), capable of detecting such clots on pictures of the milk filter socks of the milking system, after the phase in which the first streams of milk have been discarded. In total, 696 pictures were taken with clots and 586 pictures without. These were randomly divided into 60/20/20 training, validation, and testing datasets, respectively, for the training and validation of the NN. A convolutional NN with residual connections was trained, and the hyperparameters were optimized based on the validation dataset using a genetic algorithm. The integrated gradients were calculated to explain the interpretation of the NN. The accuracy of the NN on the testing dataset was 100%. The integrated gradients showed that the NN identified the clots. Further field validation through integration into AMS is necessary, but the proposed deep learning method is very promising for the inline detection of CM on AMS farms.

Технологические свойства препаратов сычужного фермента

The quality of the finished cheese is determined by all stages of its production, but the basis of cheese making is the production of a milk clot under the action of a milk-converting enzyme. The duration of coagulation and the structural and mechanical properties of the cheese clot are critical indicators that affect the yield of cheese, consistency, pattern, taste. In practice, it is necessary to take into account that the coagulating ability of the enzyme may vary depending on the properties of the milk mixture prepared for coagulation (protein content, mineral salts, acidity, temperature). The main technological characteristics of rennet enzyme preparations (proteolytic activity, qualitative composition, sensitivity to Caions, pH, thermal stability), important for the regulation of the coagulation process, have been studied. Practical recommendations on the use of milk-clotting enzyme preparations are given.

ASSESSMENT OF THE QUALITY AND SUITABILITY OF DAIRY PRODUCTS FOR PRODUCTION OF HARD CHEESE

Some aspects of feeding dairy cows and factors affecting the production of high-quality milk suitable for the production of cheeses are considered, in particular, the study of the possibility of full or partial replacement of corn silage with silage from one-year forage crops in the rations. The study was conducted on cows of the Ukrainian black and spotted dairy breed using the method of periods. In the first period (duration 36 days), in addition to the main diet, the animals were fed 25 kg of corn silage, in the second (29 days) - 17 kg of hay from one-year forage crops, and in the third (35 days) - 12 kg of corn silage + 10 kg hay one-year forage crops. The main ration consisted of cereal and legume hay, winter wheat straw, fodder beets, a mixture of grain concentrates and premix. Density, content of dry matter, fat, total protein and casein and its fractional composition, lactose, degree of bacterial contamination, coagulation time of milk under the action of rennet enzyme were determined in milk.
 At the end of each period, batches of cheese were produced, the acidity, content of dry matter, fat, protein, degree of maturity were determined in the samples, and their expert evaluation was carried out. Since for the production of high-quality cheeses, milk must meet certain organoleptic parameters, chemical composition, bacterial contamination, the article provides requirements for its quality, as well as recommended rations and composition of premixes. It has been established that for feeding cows in cheese-making areas during the stall period, it is possible to recommend partial or complete replacement of corn silage (as it contains little calcium, which causes slow rennet coagulation of milk) with hay from one-year forage crops, which will lead to improvement of the technological properties of milk (reduction of time coagulation with rennet enzyme for 4-5 minutes, increasing the yield of mature cheese by 7-8%) and will contribute to increasing the casein content in cheese (by 0.12-0.15%), k-fraction of casein (by 1.6-2.1%) and calcium, which are he main indicators of milk suitability for cheese production.

Ethanol-salt based two-phase partitioning for concentration of milk clotting proteases from Sweet Indrajao (Wrightia tinctoria R. Br.) fruit

Cheese is the naturally fermented dairy product beloved for its wide variety of textures and other nutritional qualities. Animal rennet, microbial and fermentation produced chymosin are generally considered for commercial level cheese preparation. In order to meet the growing global demand observed in cheese market, milk clotting proteases from diverse alternative sources are under exploration. Sweet Indrajao (Wrightia tinctoria R. Br.) fruit extract is known for its utility in traditional cheese preparation. Organic solvent-salt based aqueous two-phase system (ATPS) using ethanol and salt was employed to partially purify milk clotting proteases from W. tinctoria fruit. The system with ethanol-25.90% (w/w) and dipotassium phosphate-13.60% (w/w) was found favorable with yield of 96.33%, milk clotting index of 77.85, purification factor of 2.42, partition coefficient of 458.80 and selectivity of 345.58. Tricine SDS-PAGE and zymogram revealed presence of two prominent protein bands between 66 and 97.4 kDa with caseinolytic activity. Whole casein and κ- casein hydrolysis pattern was analyzed by tricine SDS-PAGE. The optimized system was scaled up to 100 g and its performance was found comparable to its 10 g counterpart. Characteristics of the cheese prepared using partitioned enzyme was comparable to that of the positive control used (Enzeco®).

The process of yak milk fermentation by polycomponent starter culture

The paper presents a comparative characteristic of the fermentation processes of yak and cow milk samples with a high fat content of 1.5% and 6% with a multicomponent starter culture, which includes Lactobacillus acidophilus, Bifidobacterium animalis subsp Lactis and Streptococcus thermophiles. Acid formation in the process of milk fermentation under the influence of the starter microflora was assessed by the dynamics of changing in titratable (Ac) and active (pH) acidity over time. The course of the formation of the structure of the resulting clot was monitored on a rheometer, fixing the viscosity characteristics of the fermented milk clot in dynamics. It has been established that the increase in acidity occurs more intensively in yak milk in comparison with cow's milk with a corresponding acceleration of the formation of a fermented milk clot. In conclusion, the resulting clots were subjected to sensory analysis with the identification of the best sample, which was fermented yak milk with a fat mass fraction of 6%.

Performance Evaluation of Fiber Near-Infrared (NIR) Optic Probes for Quality Control of Curd Hardness in Cheese Produced by Spray-Dried Milk

This study aims to provide the dairy industry with a direct control model focused on milk coagulation by using multifiber probes to determine parameters in the curding process, such as cutting time, at a lower cost. The main objective of the research is to confirm that a multifiber NIR light scattering probe can be used to predict the elastic modulus of curd during milk coagulation in cheese production. Two randomized complete block designs were used with a 3 × 3 factorial arrangement of three protein levels (3%, 3.5% and 4%) and three wavelengths (870 nm, 880 nm and 890 nm). Using a multifiber probe at a wavelength of 880 nm allowed obtaining a better optical response of the sensor during enzymatic milk coagulation than the 870 nm. It showed greater sensitivity to variations in the protein content of the milk and lower variation in the response. The multifiber probe at a wavelength of 880 nm generated a NIR light backscatter profile like those obtained with other systems. The results showed that the prediction model parameters had a variation as a function of the protein content, which opens the possibility of improving the prediction model’s performance substantially. Furthermore, the initial voltage obtained with the probe responded linearly to the different protein levels in milk. This fact would make it possible, at least theoretically, to estimate protein concentration with the same inline probe for G’ determination, facilitating the incorporation of a corrective protein factor in the prediction models using a single instrument.

Invited review. Milk clotting enzymes: A transcendental decision in goat´s milk cheese quality

Cheese production has increased more than 3.5-fold since 1960, while animal rennet production has declined, thus other proteolytic enzymes have been developed. Cheese quality depend on many factors, some of them are linked to milk composition (genetic aspects: species, breed and animal, lactation stage and number, type of kidding, animal feeding and health, offspring season, etc.) and other due to cheesemaking aspects and storage processing (raw or pasteurized milk, coagulation enzymes and coagulation parameters (temperature and time), moulding, drainage, salting, ripening, smoking, etc.). All these factors interact and only under experimental conditions it is possible to analyse the effect of any particular feature by itself. Between all these factors, milk coagulation process is one of the most important steps for the cheese final characteristics. The differences in protein matrix degradation due the origin of coagulant agents affect cheese texture, odour, flavour and taste and consequently consumer’s preference. This last assertion is especially important for the economic choices of the dairy firm. In the past, cheesemakers used animal rennet for curdling milk; it was produced by macerating the stomachs obtained from suckling ruminants according to the local uses, although plant coagulant was used in some typical specific cheesemaking processes. Nowadays, several types of coagulant are available, with different origin and variability in proteases for milk coagulation: animal origin rennet and vegetable coagulants than can be both artisan or commercial, microbial proteases and recombinant from genetically modified microorganism with cDNA for chymosin. In this paper the state of the art of these enzymes used in goat´s cheese industry is presented, also focused on artisan cheeses. Coagulant effect in physical-chemical and sensory profile of cheeses is analysed, also under an ethical and religious point of view. Finally, the importance of the market target in producing new cheese with vegetable coagulant is met, with an overview on the trends on cheese labelling issue.

Milk-Clotting Properties and Primary Proteolysis of a Lyophilised Extract from Artichoke Flowers (Cynara scolymus L.).

A few studies have investigated Cynara scolymus enzymes as a substitute for calf rennet in cheese making. They used aqueous extracts prepared by maceration of plant material and stored by freezing. However, it was indicated that lyophilisation is a better alternative to preserve the coagulant properties of plant extracts over a longer period of time, as it is a more controllable, stable and hygienic alternative with a better shelf life that is easier to transport, store and standardise. We obtained a lyophilised extract of mature artichoke flowers, named CS, which was characterised for its milk-clotting properties at different pH and temperatures. In addition, the potential yield, whey composition and the primary hydrolysis profile of caseins by urea-polyacrylamide gel electrophoresis (PAGE) of mini curds prepared with different doses of coagulant were determined. The lyophilised extract was able to hydrolyse casein and showed stable proteolytic activity at pH=6.4 and 37 °C for 50 min, which decreased when the process temperature was increased to 41 and 45 °C and was lost at 70 °C. On the other hand, milk-clotting activity increased significantly (p<0.001) when the temperature increased from 37 to 45 °C and the pH of the milk decreased from 6.8 to 5.8. Potential yield ​​between 10 and 17 % was obtained for the mini curds prepared with the lyophilised artichoke extract, and the casein degradation pattern obtained by urea-PAGE was similar to that of the commercial coagulant. On a laboratory scale, our work has shown that the lyophilised artichoke extract has sufficient proteolytic and coagulant activity to be used as a milk coagulant, i.e. plant rennet, in cheese making as an alternative to animal rennet. As this extract is lyophilised, it has the advantage of being a better alternative in terms of preservation and shelf-life. It offers an innovative way to diversify cheese products and appeal to consumers with different dietary preferences and needs.

Особенности процесса ферментации молочно-соевой смеси

The plant milk market is actively developing at the moment, as many consumers suffer from lactose and casein intolerance, while vegetarianism is being popularized. The use of soy milk is becoming popular in the technology of fermented dairy plant products, as it is a lactose-free analog of cow milk and source of native protein, polyunsaturated fatty acids, vitamins, minerals, and other micronutrients. However, the fermentation of dairy and plant compositions is quite complex and has not been fully understood yet, and therefore the goal of this study was to conduct a comparative analysis of the fermentation of milk and soy mixtures with different compositions (cow milk: soy milk in the ratios of 55:45; 70:30; 85:15). The tests were conducted at the Laboratory of Agricultural Product Processing. To obtain milk and soy mixtures, a plant protein drink – soy milk – was prepared from soybeans of the Sentyabrinka variety selected by the Federal State Budgetary Scientific Institution Federal Research Center All-Russian Research Institute of Soybean. The fermentation of milk and soy mixtures was performed using the acid-rennet method with bacterial starter cultures No. 1 (Lactobacillus lactis, Lactococcus diacetylactis, Lactococcus cremoris, Streptococcus thermophilus) and No. 2 (Lactococcus lactis ssp. lactis, Lac. lactis subsp. diacetilactis, Leuconostoc lactis and/or mesenteroides subsp. cremoris, Lactobacillus plantarum, Lactobacillus helveticus, Streptococcus thermophilus). The acid formation of fermented milk and soy clots was studied in time at intervals of 1 hour, and their active and titratable acidity levels were analyzed in the course of work. Fermentation completion was determined based on the organoleptic indicators of fermented clots and their acidity levels. The following was established as the result of the tests: composition of the milk-soy mixture – 70:30; technological fermentation process parameters and modes – 328–346 minutes at a temperature of 34 °C, with the production of a fermented milk and soy clot having the best organoleptic quality indicators – well-formed, with a stable texture, pleasant, sour-milk taste, light soy aftertaste and smell. The analytical dependences of the titratable and active acidity indicators on the duration of fermentation process were calculated based on an analysis of acid formation in experimental clot samples.

Effects of calf rennet, and microbial and plant coagulants on rheological properties of milk for Grana Padano PDO cheese production

The effects of calf rennet, and microbial and plant coagulants on milk coagulation properties (MCP) measured through lactodynamographic analysis were investigated. Each coagulant was tested at 7 different dilutions: one reference dilution, 3 lower dilutions (−30%, −20%, and −10% IMCU L−1 milk) and 3 greater dilutions (+10%, +20%, and +30% IMCU L−1 milk). Sources of variation of rennet coagulation time (RCT, min), curd-firming time (k20, min), and curd firmness (a30, mm) were investigated through a linear model that included the effects of coagulant, dilution, and their interaction. All the effects were highly significant in explaining the variability of the studied traits (P <0.001). In particular, calf rennet resulted in shorter k20 and greater a30 than microbial and plant coagulants. Dilution effect was linearly associated with MCP, whereby a decreasing amount of coagulant led to a lengthening of RCT and k20, whereas a less clear association was observed for a30.

Milk coagulation and gastric emptying in women experiencing gastrointestinal symptoms after ingestion of cow's milk.

Gastrointestinal symptoms after drinking milk are often attributed to lactose intolerance or cow's milk allergy. However, some individuals without either condition still report gastrointestinal symptoms after drinking milk. This may be caused by gastric emptying (GE) rate or gastric protein coagulation. This study aimed to compare GE rate and protein coagulation after milk consumption between individuals reporting gastrointestinal symptoms and those without symptoms using a novel gastric MRI approach. Thirty women were included in this case-control study, of whom 15 reported gastrointestinal symptoms after drinking milk and 15 were controls. Participants underwent gastric MRI before and up to 90 min after consumption of 250 mL cow's milk. Gastric content volume and image texture of the stomach contents were used to determine GE and changes in the degree of coagulation. GE half-time did not differ between the groups (gastrointestinal symptom group 66 ± 18 min; control group 61 ± 14 min, p = 0.845). The gastrointestinal symptom group reported symptoms from 30 min onwards and rated pain highest at 90 min. The control group reported no symptoms. Image texture analyses showed a significantly higher percentage of coagulum and lower percentage of liquid in the group in the GI symptom group (MD 11%, 95% CI [3.9, 17], p = 0.003). Invitro data suggests that pH and proteolytic enzyme activity influence the coagulum structure. Gastric milk coagulation and emptied fraction of stomach content may differ between individuals experiencing symptoms after milk consumption, possibly due to differences in pH and proteolytic enzyme activity.

Biochemical Properties of a Promising Milk-Clotting Enzyme, Moose (Alces alces) Recombinant Chymosin.

Moose (Alces alces) recombinant chymosin with a milk-clotting activity of 86 AU/mL was synthesized in the Kluyveromyces lactis expression system. After precipitation with ammonium sulfate and chromatographic purification, a sample of genetically engineered moose chymosin with a specific milk-clotting activity of 15,768 AU/mg was obtained, which was used for extensive biochemical characterization of the enzyme. The threshold of the thermal stability of moose chymosin was 55 °C; its complete inactivation occurred after heating at 60 °C. The total proteolytic activity of moose chymosin was 0.332 A280 units. The ratio of milk-clotting and total proteolytic activities of the enzyme was 0.8. The Km, kcat and kcat/Km values of moose chymosin were 4.7 μM, 98.7 s-1, and 21.1 μM-1 s-1, respectively. The pattern of change in the coagulation activity as a function of pH and Ca2+ concentration was consistent with the requirements for milk coagulants for cheese making. The optimum temperature of the enzyme was 50-55 °C. The introduction of Mg2+, Zn2+, Co2+, Ba2+, Fe2+, Mn2+, Ca2+, and Cu2+ into milk activated the coagulation ability of moose chymosin, while Ni ions on the contrary inhibited its activity. Using previously published data, we compared the biochemical properties of recombinant moose chymosin produced in bacterial (Escherichia coli) and yeast (K. lactis) producers.