Cheddar cheese: influence of milking frequency and stage of lactation on composition and yield

Advances in Atypical FT-IR Milk Screening: Combining Untargeted Spectra Screening and Cluster Algorithms

Fourier-transform mid-infrared spectrometry is an attractive technology for screening adulterated liquid milk products. So far, studies on how infrared spectroscopy can be used to screen spectra for atypical milk composition have either used targeted methods to test for specific adulterants, or have used untargeted screening methods that do not reveal in what way the spectra are atypical. In this study, we evaluate the potential of combining untargeted screening methods with cluster algorithms to indicate in what way a spectrum is atypical and, if possible, why. We found that a combination of untargeted screening methods and cluster algorithms can reveal meaningful and generalizable categories of atypical milk spectra. We demonstrate that spectral information (e.g., the compositional milk profile) and meta-data associated with their acquisition (e.g., at what date and which instrument) can be used to understand in what way the milk is atypical and how it can be used to form hypotheses about the underlying causes. Thereby, it was indicated that atypical milk screening can serve as a valuable complementary quality assurance tool in routine FTIR milk analysis.

Compositional and functional properties of milk and dairy products derived from cows fed pasture or concentrate-based diets

Worldwide milk production is predominantly founded on indoor, high-concentrate feeding systems, whereas pasture-based feeding systems are most common in New Zealand and Ireland but have received greater attention recently in countries utilizing conventional systems. Consumer interest in 'pasture-fed' dairy products has also increased, arising from environmental, ethical, and nutritional concerns. A substantial body of research exists describing the effect of different feeding strategies on the composition of milk, with several recent studies focusing on the comparison of pasture- and concentrate-based feeding regimes. Significant variation is typically observed in the gross composition of milk produced from different supplemental feeds, but various changes in the discrete composition of macromolecular components in milk have also been associated with dietary influence, particularly in relation to the fatty acid profile. Changes in milk composition have also been shown to have implications for milk and dairy product processability, functionality and sensory properties. Methods to determine the traceability of dairy products or verify marketing claims such as 'pasture-fed' have also been established, based on compositional variation due to diet. This review explores the effects of feed types on milk composition and quality, along with the ultimate effect of diet-induced changes on milk and dairy product functionality, with particular emphasis placed on pasture- and concentrate-based feeding systems.

Invited review: organic and conventionally produced milk-an evaluation of factors influencing milk composition

Consumer perception of organic cow milk is associated with the assumption that organic milk differs from conventionally produced milk. The value associated with this difference justifies the premium retail price for organic milk. It includes the perceptions that organic dairy farming is kinder to the environment, animals, and people; that organic milk products are produced without the use of antibiotics, added hormones, synthetic chemicals, and genetic modification; and that they may have potential benefits for human health. Controlled studies investigating whether differences exist between organic and conventionally produced milk have so far been largely equivocal due principally to the complexity of the research question and the number of factors that can influence milk composition. A main complication is that farming practices and their effects differ depending on country, region, year, and season between and within organic and conventional systems. Factors influencing milk composition (e.g., diet, breed, and stage of lactation) have been studied individually, whereas interactions between multiple factors have been largely ignored. Studies that fail to consider that factors other than the farming system (organic vs. conventional) could have caused or contributed to the reported differences in milk composition make it impossible to determine whether a system-related difference exists between organic and conventional milk. Milk fatty acid composition has been a central research area when comparing organic and conventional milk largely because the milk fatty acid profile responds rapidly and is very sensitive to changes in diet. Consequently, the effect of farming practices (high input vs. low input) rather than farming system (organic vs. conventional) determines milk fatty acid profile, and similar results are seen between low-input organic and low-input conventional milks. This confounds our ability to develop an analytical method to distinguish organic from conventionally produced milk and provide product verification. Lack of research on interactions between several influential factors and differences in trial complexity and consistency between studies (e.g., sampling period, sample size, reporting of experimental conditions) complicate data interpretation and prevent us from making unequivocal conclusions. The first part of this review provides a detailed summary of individual factors known to influence milk composition. The second part presents an overview of studies that have compared organic and conventional milk and discusses their findings within the framework of the various factors presented in part one.

Microbiological Quality and Safety Issues in Cheesemaking

As the manufacture of cheese relies in part on the select outgrowth of microorganisms, such conditions can also allow for the multiplication of unwanted contaminants. Milk ultimately becomes contaminated with microorganisms originating from infection, the farm environment, and feedstuffs, as well as milking and processing equipment. Thus, poor sanitation, improper milk handling, and animal health issues can result in not only decreased yield and poor quality but also sporadic cases and outbreaks of dairy-related disease. The entry, establishment, and persistence of food-borne pathogens in dairy processing environments also present a considerable risk to products postprocessing. Food safety management systems coupled with regulatory policies and microbiological standards for milk and milk products currently implemented in various nations work to reduce risk while improving the quality and safety of cheese and other dairy products. With that, cheese has enjoyed an excellent food safety record with relatively few outbreaks of food-borne disease considering the amount of cheese produced and consumed worldwide. However, as cheese production and consumption continue to grow, we must remain vigilant in ensuring the continued production of safe, high-quality cheese.

Real-time evaluation of milk quality as reflected by clotting parameters of individual cow's milk during the milking session, between day-to-day and during lactation

Real-time analysis of milk coagulation properties as performed by the AfiLab™ milk spectrometer introduces new opportunities for the dairy industry. The study evaluated the performance of the AfiLab™ in a milking parlor of a commercial farm to provide real-time analysis of milk-clotting parameters -Afi-CF for cheese manufacture and determine its repeatability in time for individual cows. The AfiLab™ in a parlor, equipped with two parallel milk lines, enables to divert the milk on-line into two bulk milk tanks (A and B). Three commercial dairy herds of 220 to 320 Israeli Holstein cows producing ∼11 500 l during 305 days were selected for the study. The Afi-CF repeatability during time was found significant (P < 0.001) for cows. The statistic model succeeded in explaining 83.5% of the variance between Afi-CF and cows, and no significant variance was found between the mean weekly repeated recordings. Days in milk and log somatic cell count (SCC) had no significant effect. Fat, protein and lactose significantly affected Afi-CF and the empirical van Slyke equation. Real-time simulations were performed for different cutoff levels of coagulation properties where the milk of high Afi-CF cutoff value was channeled to tank A and the lower into tank B. The simulations showed that milk coagulation properties of an individual cow are not uniform, as most cows contributed milk to both tanks. Proportions of the individual cow's milk in each tank depended on the selected Afi-CF cutoff. The assessment of the major causative factors of a cow producing low-quality milk for cheese production was evaluated for the group that produced the low 10% quality milk. The largest number of cows in those groups at the three farms was found to be cows with post-intramammary infection with Escherichia coli and subclinical infections with streptococci or coagulase-negative staphylococci (∼30%), although the SCC of these cows was not significantly different. Early time in lactation together with high milk yield >50 l/day, and late in lactation together with low milk yield<15 l/day and estrous (0 to 5 days) were also important influencing factors for low-quality milk. However, ∼50% of the tested variables did not explain any of the factors responsible for the cow producing milk in the low - 10% Afi-CF.

Proteomic study of proteolysis during ripening of Cheddar cheese made from milk over a lactation cycle

Milk for cheese production in Ireland is predominantly produced by pasture-fed spring-calving herds. Consequently, there are marked seasonal changes in milk composition, which arise from the interactive lactational, dietary and environmental factors. In this study, Cheddar cheese was manufactured on a laboratory scale from milk taken from a spring calving herd, over a 9-month lactation cycle between early April and early December. Plasmin activity of 6-months-old Cheddar cheese samples generally decreased over ripening time. One-dimensional urea-polyacrylamide gel electrophoresis (PAGE) of cheese samples taken after 6 months of ripening showed an extensive hydrolysis of caseins, with the fastest hydrolysis of αs1-caseins in cheeses made in August. A proteomic comparison between cheeses produced from milk taken in April, August and December showed a reduction in levels of β-casein and appearance of additional products, corresponding to low molecular weight hydrolysis products of the caseins. This study has demonstrated that a seasonal milk supply causes compositional differences in Cheddar cheese, and that proteomic tools are helpful in understanding the impact of those differences.

Yield and sensory properties of cheese made with milk from Holstein or Montbeliarde cows milked twice or once daily

The aim of this study was to evaluate the milk properties and the yield and sensory properties of Cantal cheese made with milk from Holstein or Montbéliarde cows milked once or twice daily. Sixty-four grazing cows [32 Holstein (H) and 32 Montbéliarde (M) cows] in the declining phase of lactation (157 d in milk) were allocated to 1 of 2 equivalent groups milked once daily (ODM) or twice daily (TDM) for 7 wk. The full-fat raw milk collected during 24 h from the 4 groups of cows (M-TDM, M-ODM, H-TDM, and H-ODM) was pooled and processed into Cantal cheese 4 times during the last 4 wk of the experimental period. In all, 16 cheeses were made (2 milking frequencies x 2 breeds x 4 replicates) and analyzed after a ripening period of 15 and 28 wk. The results showed that for both breeds, the pooled milk content of fat, whey protein, casein, total protein, and phosphorus as well as rennet clotting time and curd firming time were significantly higher with ODM cows, whereas the casein-to-total protein ratio was lower, and lactose, urea, calcium, and free fatty acids contents of milk remained unchanged. The acidification and draining kinetics of the cheese as well as cheese yields and the chemical and rheological properties of the ripened cheese were not significantly modified by milking frequency. For both breeds, the cheeses derived from ODM cows had a slightly yellower coloration but the other sensory attributes, except for pepper odor, were not significantly affected by milking frequency, thereby demonstrating that ODM does not have an adverse effect on the sensory properties of Cantal cheese. Compared with that of Holstein cows, milk from Montbéliarde cows resulted in a higher cheese yield (+1.250 kg/100 kg of milk) and ripened cheeses with lower pH, dry matter, calcium, sodium chloride, and water-soluble nitrogen concentrations. These cheeses had also a less firm and more elastic texture, a more acidic taste, and a yogurt/whey aroma.

Valuation of milk composition and genotype in cheddar cheese production using an optimization model of cheese and whey production

A mass balance optimization model was developed to determine the value of the kappa-casein genotype and milk composition in Cheddar cheese and whey production. Inputs were milk, nonfat dry milk, cream, condensed skim milk, and starter and salt. The products produced were Cheddar cheese, fat-reduced whey, cream, whey cream, casein fines, demineralized whey, 34% dried whey protein, 80% dried whey protein, lactose powder, and cow feed. The costs and prices used were based on market data from March 2004 and affected the results. Inputs were separated into components consisting of whey protein, ash, casein, fat, water, and lactose and were then distributed to products through specific constraints and retention equations. A unique 2-step optimization procedure was developed to ensure that the final composition of fat-reduced whey was correct. The model was evaluated for milk compositions ranging from 1.62 to 3.59% casein, 0.41 to 1.14% whey protein, 1.89 to 5.97% fat, and 4.06 to 5.64% lactose. The kappa casein genotype was represented by different retentions of milk components in Cheddar cheese and ranged from 0.715 to 0.7411 kg of casein in cheese/kg of casein in milk and from 0.7795 to 0.9210 kg of fat in cheese/kg of fat in milk. Milk composition had a greater effect on Cheddar cheese production and profit than did genotype. Cheese production was significantly different and ranged from 9,846 kg with a high-casein milk composition to 6,834 kg with a high-fat milk composition per 100,000 kg of milk. Profit (per 100,000 kg of milk) was significantly different, ranging from $70,586 for a high-fat milk composition to $16,490 for a low-fat milk composition. However, cheese production was not significantly different, and profit was significant only for the lowest profit ($40,602) with the kappa-casein genotype. Results from this model analysis showed that the optimization model is useful for determining costs and prices for cheese plant inputs and products, and that it can be used to evaluate the economic value of milk components to optimize cheese plant profits.

Impact of Milking Frequencies on the Level of Free Fatty Acids in Milk, Fat Globule Size, and Fatty Acid Composition

The aim of the present study was to study the effect of milking cows 4 times daily on free fatty acids (FFA) in the milk compared with milking twice daily. An experiment was performed during 2 wk in which half udders in 11 cows were milked 2 or 4 times daily. Milk yield was measured, and milk was analyzed for fat content, FFA, fatty acid composition, fat globule size, and activity of gamma-glutamyl transpeptidase. Concentration of FFA was greater (1.49 mEq/100 g of fat) in milk from half udders milked 4 times daily than in milk from the half udders milked twice daily (1.14 mEq/100 g of fat). Further, it was noted that milk from the half udder milked 4 times daily contained milk fat globules with larger average diameters. Increased milking frequency increased milk yield by 9% compared with the udder half milked twice daily, but fat content and fat yield were not affected. The results are of importance for further understanding the mechanisms behind the increased content of FFA that is frequently observed in automatic milking systems.

Impact of Seasonal Changes in Ovine Milk on Composition and Yield of a Hard-Pressed Cheese

A hard-pressed, brined cheese was produced from frozen ovine milk collected in February, May, and August. Solids in the milk decreased as the season progressed. This was a result of high solids in early-lactation milk and low solids in August milk because of hot weather and poorer quality pastures. Casein as a percentage of true protein and the casein to fat ratio were higher in May and August milk. Fat in the cheese from February milk was higher and total protein was lower than in May and August. Milk, whey, and press whey composition were influenced by season and followed the trends of milk composition. Fat recovery in the cheeses ranged from 83.2 to 84.2%. Protein recovery in the cheeses was not affected by season. Cheese yield from February milk was higher than from May and August milk and was a result of higher casein and fat in the milk.

Effect of milking frequency on DHI performance measures

Increasing production by increasing milking frequency (MF) is a management option available to dairy producers. This study examined effects of MF and interactions with region and herd size on measures of herd performance. Dairy Herd Improvement (DHI) Holstein herd summary records (n = 10,754, 10,550, and 10,438) for the years 1998, 1999, and 2000 were classified by MF: two times a day (2X) milking vs three times a day (3X); herd size: small (< 250 cows) and large (> or = 250 cows); and region: North and South. Percentage of herds milking 3X by year were 7.0, 6.7, and 7.1. Rolling herd average milk production was 16, 16, and 15% higher for herds milking 3X than herds milking 2X for the respective years. Herds milking 3X in the North region outproduced herds milking 3X in the South region. Milk fat and protein percentages were lower for herds milking 3X during all 3 yr. Differences in energy-corrected milk production between herds milking 3X and herds milking 2X were 14.5, 13.4, and 13.4% during the respective 3 yr as a result of lower component percentages for herds milking 3X. Herds milking 3X had more days open and higher actual calving intervals than herds milking 2X. Services per pregnancy for herds breeding primarily by artificial insemination were higher for herds milking 3X than for herds milking 2X. Somatic cell scores and weighted somatic cell counts were lower for herds milking 3X than herds milking 2X. Herds milking 3X had a higher percentage of somatic cell scores in the low range (0 to 3) and a lower percentage in the high range (7 to 9). Mean percentages of cows entering and leaving the herd were higher for herds milking 3X during all 3 yr.

Influence of salt on the quality of reduced fat cheddar cheese

Cream was homogenized in a two-stage homogenizer (17.25 MPa in the first stage and 3.43 MPa in the second stage); blended with skim milk to produce milk containing 1.25% fat, which was pasteurized (63 degrees C for 30 min); and then manufactured into reduced fat Cheddar cheese. After milling, the curd was divided into three equal portions of 13 kg each. Three salting rates, 2.3, 3.8, and 5%, yielded cheeses with 1.3, 1.7, and 2.0% salt and 2.7, 3.7, and 4.5% salt in the moisture phase. Cheese moisture contents ranged from 45% (2.0% salt) to 47.7% (1.3% salt), and fat contents ranged from 14.6 to 15.1%. In the texture profile analysis, the hardness and fracturability of the cheeses increased as the salt content increased. Both parameters decreased during ripening, but cheeses with 4.5% salt in the moisture phase remained the hardest. Cheeses with the most salt had the least desirable body characteristics, but there were no differences in flavor. Intensity of bitterness was lowered as the amount of salt in cheese increased. During ripening, the number of lactic acid bacteria decreased more slowly in cheese with 2.7% salt in the moisture phase than in those with 3.7 or 4.5% salt in the moisture phase. As the salt content increased, proteolysis and the general rate of ripening decreased. Degradation of alpha s-casein was reduced by higher percentages of salt, but no differences were found in the degradation of beta-casein.

Influence of milking three times a day on milk quality

Lactations were divided into three periods: early (1 to 99 d), mid (100 to 199 d), and late (200 to 299 d). One hundred Holsteins were randomly split into four groups that were balanced for parity. Groups 222 and 333 were milked twice and three times a day, respectively, throughout lactation. Group 233 was switched from twice to three times daily milking at 100 d, and group 223 was switched at 200 d. Compared with group 222, milk yield for group 333 increased by 10.4%, and fat and protein yields increased by 4.7 and 7.3%, respectively. Mean milk SCC for all groups was < 175,000 cells/ml within each lactation period. The percentage of CP was lower for cows milked three times a day than for cows milked twice a day during each stage of lactation (early, 2.78 and 2.91; mid, 3.08 and 3.19; and late, 3.16 and 3.28, respectively). Casein as a percentage of CP was significantly higher for cows milked three times a day during midlactation. The acid degree values (milliequivalents of FFA/ 100 g of fat) were significantly higher for milk from cows milked three times a day than for cows milked twice a day during early and midlactation, (early, 0.75 and 0.55; mid, 0.82 and 0.61; and late, 0.88 and 0.75, respectively). No differences were detected in milk flavor or plasmin activity because of milking frequency. Casein as a percentage of CP decreased, and plasmin activity increased, as parity and stage of lactation increased.