Rennet Coagulation Time Of Milk Research Articles

Including clover and herb species in grazing forages – effects on milk production, milk processability and milk fatty acid profile of late lactation dairy cows supplemented with grass silage and concentrate

Abstract Milk production declines as dairy cows enter late lactation, resulting in reduced milk quality and negatively impacting milk processability, such as rennet coagulation time (RCT), milk pH and ethanol stability (ES), leading to seasonality issues for milk processors. Multispecies forages, containing grass, legume and herb species, require lower N inputs and are of interest to dairy farmers. However, little is known about the effect of grazing multispecies forages on milk processability characteristics in late lactation dairy cows. Forty-five autumn-calving dairy cows in late lactation were allocated to 1 of 3 grazing forages; perennial ryegrass (PRG; Lolium perenne), perennial ryegrass and white clover (Trifolium pratense) (PRGWC), and a 6 – species multispecies forage (MULTI) containing perennial ryegrass, timothy (Phleum pratense), white clover, red clover (Trifolium repens), chicory (Cichorium intybus) and plantain (Plantago lanceolata). Cows were allocated 12 kg DM grazed forage and supplemented with a grass – silage TMR and concentrate. Forage DMI was significantly lower for cows grazing PRG. Milk yield increased when cows grazed PRGWC (18.07 kg/d) and MULTI (17.84 kg/d) compared to PRG (16.08 kg/d). Milk RCT (mins) and ES (%) were unaffected by treatment. However, offering cows PRGWC and MULTI increased the concentration of C18:2 cis – 9, 12 and C18:3 cis – 9, 12, 15 in milk compared to PRG. Compared to PRG, grazing forages containing clover and herb species improved milk yield and beneficially altered milk fatty acid profile in late lactation dairy cows without negatively impacting milk processability.

QUATERNION-TYPE REPRESENTATION FOR MEASURING THE RENNET COAGULATION TIME OF MILK BY COLOR IMAGE SEQUENCES PROCESSING

The determination of the rennet coagulation time of milk by image sequences processing was performed using a computer vision system (CVS), consisting of a computer coupled with a transmitted light microscope equipped with a digital camera. Algorithms implemented with Matlab 2014 encoded the color image as a quaternion, computed and analyzed the histogram peak. The evolution of this last parameter was monitored as a function of the milk coagulation time, for different concentrations of calcium chloride (0.01–0.03 M) and for coagulation temperatures varying between 30 and 36°C. No statistically significant difference was observed in the measurements of the rennet coagulation time, neither by the Berridge method nor by the analysis of the image sequences, except for those at 36°C. The association of the optical microscopic method and the analysis of image sequences by a quaternion-type representation, made it possible to identify optical changes during gel formation and to accurately determine the rennet coagulation time of milk.

Effect of THI on milk coagulation properties of Holstein-Friesian dairy cattle

ABSTRACT The objective of this study was to evaluate the effect of temperature-humidity index (THI) on the milk coagulation properties of Holstein-Friesian dairy cattle from northeast part of Italy. A total of 592 individual milk samples from six dairy herds were evaluated. The milk coagulation properties traits analysed were milk rennet coagulation time and curd firmness, as well as the fat, protein, and casein contents, pH, milk aptitude to coagulate (IAC), and the somatic cell count. The THI was determined [...]

Transglutaminase cross-linking of milk proteins for improved functionality of cow and buffalo milk

Modification of proteins by enzymes such as Transglutaminase (TG) has recently become of great interest to food scientists. TG induced cross-linking has strong effects on the functionality of milk proteins. Effect of TG on heat stability, antioxidant activity, surface hydrophobicity, rennet coagulation time, emulsifying and foaming properties of cow and buffalo milk proteins was studied. TG treatment improves heat stability from 18 min to 38 min in cow milk and 14.5 min to 25.5 min in buffalo milk, surface hydrophobicity from 237.28 to 292.23 in cow milk and 252.8 to 332.7 in buffalo milk. Cross-linked cow and buffalo casein shows better emulsifying and foaming properties. It does not affect the antioxidant activity of milk proteins. Whereas cross-linked milk proteins are highly resistant to rennet coagulation. TG treatment completely prevents rennet coagulation of cow milk, whereas in buffalo milk rennet coagulation time gets elongated.

Transglutaminase cross-linking of milk proteins for improved functionality of cow and buffalo milk

Modification of proteins by enzymes such as Transglutaminase (TG) has recently become of great interest to food scientists. TG induced cross-linking has strong effects on the functionality of milk proteins. Effect of TG on heat stability, antioxidant activity, surface hydrophobicity, rennet coagulation time, emulsifying and foaming properties of cow and buffalo milk proteins was studied. TG treatment improves heat stability from 18 min to 38 min in cow milk and 14.5 min to 25.5 min in buffalo milk, surface hydrophobicity from 237.28 to 292.23 in cow milk and 252.8 to 332.7 in buffalo milk. Cross-linked cow and buffalo casein shows better emulsifying and foaming properties. It does not affect the antioxidant activity of milk proteins. Whereas cross-linked milk proteins are highly resistant to rennet coagulation. TG treatment completely prevents rennet coagulation of cow milk, whereas in buffalo milk rennet coagulation time gets elongated.

Short communication: Genetic correlation and heritability of milk coagulation traits within and across lactations in Holstein cows using multiple-lactation random regression animal models

Genetic parameters of milk rennet coagulation time (RCT) and curd firmness (a30) among the first 3 lactations in Holstein cows were estimated. The data set included 39,960 test-day records from 5,216 Estonian Holstein cows (the progeny of 306 sires), which were recorded from April 2005 to May 2010 in 98 herds across the country. A multiple-lactation random regression animal model was used. Individual milk samples from each cow were collected during routine milk recording. These samples were analyzed for milk composition and coagulation traits with intervals of 2 to 3 mo in each lactation (7 to 305 DIM) and from first to third lactation. Mean heritabilities were 0.36, 0.32, and 0.28 for log-transformed RCT [ln(RCT)] and 0.47, 0.40, and 0.62 for a30 for parities 1, 2, and 3, respectively. Mean repeatabilities for ln(RCT) were 0.53, 0.55, and 0.56, but 0.59, 0.61, and 0.68 for a30 for parities 1, 2 and 3, respectively. Mean genetic correlations between ln(RCT) and a30 were −0.19, −0.14, and 0.02 for parities 1, 2, and 3, respectively. Mean genetic correlations were 0.91, 0.79, and 0.99 for ln(RCT), and 0.95, 0.94, and 0.94 for a30 between parities 1 and 2, 1 and 3, and 2 and 3, respectively. Due to these high genetic correlations, we concluded that for a proper genetic evaluation of milk coagulation properties it is sufficient to record RCT and a30 only in the first lactation.

Effect of fat content on sensory and physico‐chemical properties of laboratory‐pasteurised calcium‐ and vitamin D‐fortified mixture of cow and buffalo milk

The influence of milk fat on physico‐chemical properties of calcium and vitamin D‐fortified milk was investigated. Sensory scores, curd tension, viscosity, rennet coagulation time and TBA value increased with the increase in fat content. Calcium and vitamin D fortification had no effect on sensory scores, whereas a significant increase was observed in curd tension and viscosity. The TBA value of fortified milk was significantly lower than that of the unfortified milk. The rennet coagulation time of milk increased significantly with addition of calcium phosphate, whereas calcium citrate fortification had no significant effect. All milk samples were stable to alcohol.

Selection for milk coagulation properties predicted by Fourier transform infrared spectroscopy in the Italian Holstein-Friesian breed

Milk coagulation is based on a series of physicochemical changes at the casein micelle level, resulting in formation of a gel. Milk coagulation properties (MCP) are relevant for cheese quality and yield, important factors for the dairy industry. They are also evaluated in herd bulk milk to reward or penalize producers of Protected Designation of Origin cheeses. The economic importance of improving MCP justifies the need to account for this trait in the selection process. A pilot study was carried out to determine the feasibility of including MCP in the selection schemes of the Italian Holstein. The MCP were predicted in 1,055 individual milk samples collected in 16 herds (66±24 cows per herd) located in Brescia province (northeastern Italy) by means of Fourier transform infrared (FTIR) spectroscopy. The coefficient of determination of prediction models indicated moderate predictions for milk rennet coagulation time (RCT=0.65) and curd firmness (a30=0.68), and poor predictions for curd-firming time (k20=0.49), whereas the range error ratio (8.9, 6.9, and 9.5 for RCT, k20, and a30, respectively) indicated good practical utility of the predictive models for all parameters. Milk proteins were genotyped and casein haplotypes (αS1-, β-, αS2-, and κ-casein) were reconstructed. Data from 51 half-sib families (19.9±16.4 daughters per sire) were analyzed by an animal model to estimate (1) the genetic parameters of predicted RCT, k20, and a30; (2) the breeding values for these predicted clotting variables; and (3) the effect of milk protein genotypes and casein haplotypes on predicted MCP (pMCP). This is the first study to estimate both genetic parameters and breeding values of pMCP, together with the effects of milk protein genotypes and casein haplotypes, that also considered k20, probably the most important parameter for the dairy industry (because it indicates the time for the beginning of curd-cutting). Heritability of predicted RCT (0.26) and k20 (0.31) were close to the average heritability described in literature, whereas the heritability of a30 was higher (0.52 vs. 0.27). The effects of milk proteins were statistically significant and similar to those obtained on measured MCP. In particular, haplotypes including uncommon variants showed positive (B-I-A-B) or negative (B-A1-A-E) effects. Based on these findings, FTIR spectroscopy-pMCP is proposed as a potential selection criterion for the Italian Holstein.

The antioxidant properties of skim milk supplemented with rosemary and green tea extracts in response to pasteurisation, homogenisation and the addition of salts

The aim of this study was to develop functional dairy products with high antioxidant activities to combat the risk of degenerative diseases. Rosemary and green tea extracts were added separately to reconstituted skim milk at the ratios of 2.0%, 4.0%, 6.0%, 8.0% and 10.0% respectively. The effect of pasteurisation, homogenisation, addition of calcium chloride and sodium chloride as well as the effect of added extracts on rennet coagulation time of milk were measured. The additions of green tea, rosemary extract, calcium chloride and pasteurisation significantly increased markedly the phenol content and the antioxidant activity of skim milk.

Prediction of coagulation properties, titratable acidity, and pH of bovine milk using mid-infrared spectroscopy

This study investigated the potential application of mid-infrared spectroscopy (MIR 4,000–900cm−1) for the determination of milk coagulation properties (MCP), titratable acidity (TA), and pH in Brown Swiss milk samples (n=1,064). Because MCP directly influence the efficiency of the cheese-making process, there is strong industrial interest in developing a rapid method for their assessment. Currently, the determination of MCP involves time-consuming laboratory-based measurements, and it is not feasible to carry out these measurements on the large numbers of milk samples associated with milk recording programs. Mid-infrared spectroscopy is an objective and nondestructive technique providing rapid real-time analysis of food compositional and quality parameters. Analysis of milk rennet coagulation time (RCT, min), curd firmness (a30, mm), TA (SH°/50mL; SH°=Soxhlet-Henkel degree), and pH was carried out, and MIR data were recorded over the spectral range of 4,000 to 900cm−1. Models were developed by partial least squares regression using untreated and pretreated spectra. The MCP, TA, and pH prediction models were improved by using the combined spectral ranges of 1,600 to 900cm−1, 3,040 to 1,700cm−1, and 4,000 to 3,470cm−1. The root mean square errors of cross-validation for the developed models were 2.36min (RCT, range 24.9min), 6.86mm (a30, range 58mm), 0.25 SH°/50mL (TA, range 3.58 SH°/50mL), and 0.07 (pH, range 1.15). The most successfully predicted attributes were TA, RCT, and pH. The model for the prediction of TA provided approximate prediction (R2=0.66), whereas the predictive models developed for RCT and pH could discriminate between high and low values (R2=0.59 to 0.62). It was concluded that, although the models require further development to improve their accuracy before their application in industry, MIR spectroscopy has potential application for the assessment of RCT, TA, and pH during routine milk analysis in the dairy industry. The implementation of such models could be a means of improving MCP through phenotypic-based selection programs and to amend milk payment systems to incorporate MCP into their payment criteria.

The effect of milk protein contents on the rennet coagulation properties of milk from individual dairy cows

The objective of this study was to investigate the effect of milk proteins on rennet coagulation properties. Milk samples ( n = 516) were taken from 54 cows once a month during one full lactation period and analysed for rennet coagulation properties, and for contents of α S1-, α S2-, β- and κ-casein, and β-lactoglobulin. The contents of the analysed milk proteins and the relative contents of different caseins (Cn) in total casein were significantly influenced by sampling month, breed, and the month of lactation. An increase in milk protein, casein, casein fractions, and the casein number decreased the rennet coagulation time of milk and increased curd firmness. Milk formed a firmer curd when the relative content of α S1- and β-Cn in total casein was lower, or the relative content of κ-Cn in total casein was higher. Higher values of κ-Cn:β-Cn and κ-Cn:α S-Cn ratios had a positive effect on curd firmness.

Milk Coagulation Ability of Five Dairy Cattle Breeds

Samples of herd milk (506) were analyzed to assess sources of variation for milk coagulation properties (MCP) for 5 different dairy cattle breeds. Data were recorded in 55 single-breed dairy herds in the Trento province, a mountain area in northeast Italy. The 5 cattle breeds were Holstein-Friesian (8 herds), Brown Swiss (16 herds), Simmental (10 herds), Rendena (13 herds), and Alpine Gray (8 herds). Herd milk samples were analyzed for the MCP traits, milk rennet coagulation time (RCT), curd-firming time, and curd firmness (a30), as well as protein and fat percentages, somatic cell count, Soxhlet-Henkel acidity, and bacterial count. An ANOVA was performed to study the effect of breed, herd within breed, DIM, month of lactation, protein and fat percentages, somatic cell score, titratable acidity, and log bacterial count within breed on MCP. Breed was the most important source of variation. In particular, the Rendena breed showed the best MCP traits at 13.5min and 27.0mm for RCT and a30, respectively. The Holstein-Friesian breed had the worst coagulation properties at 18.0min and 17.5mm for RCT and a30, respectively. The other 3 breeds showed intermediate coagulation properties. The RCT values were better at the beginning of lactation, whereas RCT and a30 values were better in September and October (14.3min and 25.7mm, respectively). Among the composition traits, only the titratable acidity affected MCP traits of herd milk positively.

EFFECT OF MICROWAVES ON THE NITROGEN DISTRIBUTION AND SOME PHYSICAL PROPERTIES AND MICROBIAL CONTENT ON SHEEPS MILK

Sheep milk was subjected to microwave for 60-180 sec., and analysed for nitrogen distribution , pH and rennet coagulation time.Also analysed for total bacterial count,Co- liform bacteria ,Staphylococcus and Salmonella. Heating with microwaves improved the bacteriological quality of milk ,but resulted in partial denaturation of whey proteins ,and Increased the ratio of casein nitrogen and non protein nitrogen,and retardation of the rennet coagulation time of milk.

Characterization of curd formation during the rennet coagulation of milk by an optical microscopic method

Abstract Optical microscopic observation of the coagulation of rennet-treated milk was performed using a conventional light microscope under standardized conditions. The microscopic images, i.e., number and average area of milk aggregates, were analyzed using Optiscan software. The evolution of the latter parameters was followed as a function of the rennet coagulation time of milk. The curves presented two inflection points which correlated with the rennet flocculation time and the rennet clotting time values, as determined by reference methods. These relationships were validated on milk supplemented with different concentrations of calcium (5.0–7.5 m m ) and subjected to varying temperatures for rennet coagulation (22.5–40°C). This optical microscopic method with associated image analysis software allowed (i) the observation of structural changes occurring during gel formation, even at low magnification (200X) and (ii) the determination of the rennet flocculation and clotting times.

Effects of high pressure on constituents and properties of milk

High pressure (HP) treatment has significant and, in many cases, unique effects on many constituents of milk. The structure of casein micelles is disrupted and the whey proteins, alpha-lactalbumin and beta-lactoglobulin, are denatured, with the former being more resistant to pressure than the latter. Pressure-induced shifts in the mineral balance in milk also occur and moderately high pressures (100-400 MPa) induce the crystallisation of milk fat. However, milk enzymes seem to be quite resistant to pressure. As a result of pressure-induced effects on individual milk constituents, many properties of milk are affected. HP treatment increases the pH of milk, reduces its turbidity, changes its appearance, and can reduce the rennet coagulation time of milk and increase cheese yield, thereby indicating potential applications in cheese technology. However, to fully understand the effects of HP treatment on milk and to evaluate the full potential of this process in dairy technology, further research is required in several areas, including the reversibility of pressure-induced changes in milk and the physical stability of HP-treated milk. (C) 2002 Elsevier Science Ltd. All rights reserved.