New markers of bulk milk quality in relation to mastitis

All dairy processors depend on a continuous supply of high-quality bulk milk from milk producers to be able to distribute liquid milk and dairy products. Mastitis, inflammation of the bovine udder, is the most common disease in dairy cows, and leads to altered milk composition and impaired milk quality. The somatic cell count (SCC) is currently used as a marker for udder health, and indirectly, for bulk milk quality, but because it is somewhat insensitive and unspecific, there has been an interest to find alternative markers. The main objective of this thesis was to acquire more knowledge about two potential markers for bulk milk quality: polymorphonuclear leukocyte count (PMNC) and α-lactalbumin (α-LA). Another objective was to study if the combination of α-LA, haptoglobin (Hp) and serum amyloid A (SAA) in an acute phase index (API) could be useful as an alternative marker for bulk milk quality. Bulk milk samples were collected from Swedish dairy farms and analyzed for PMNC, α-LA, SCC, haptoglobin (Hp), serum amyloid A (SAA), fat, lactose, total protein and casein contents, casein number, protein composition, proteolysis and coagulating properties. An API was calculated for each sample by combining results on α-LA, Hp and SAA. Samples with high PMNC had a lower casein number than samples with low PMNC, while samples with high SCC had lower lactose and casein contents, lower casein number and more proteolysis than low SCC samples. There was no significant difference in the inflammatory markers SCC, PMNC, Hp and SAA between milk samples containing low, medium or high concentrations of α-LA. Differences between α-LA groups were, however, found in some milk quality parameters as high α-LA concentration was related to low concentrations of αs1-, αs2- and β-casein, and high concentrations of lactose and β-lactoglobulin. High API was related to low lactose content and casein number. In conclusion, PMNC and α-LA were not considered more useful markers of inflammation and milk quality in bulk milk than SCC, which is currently used

Relationship between haptoglobin and serum amyloid A in milk and milk quality

The objective of this study was to evaluate relationships between the presence in milk of the major bovine acute phase proteins, haptoglobin (Hp) and serum amyloid A (SAA), and milk quality parameters. Composite milk samples were collected from 89 clinically healthy dairy cows and analysed for Hp and SAA, total protein, casein, and whey protein levels, casein number, proteolysis, total fat and lactose levels, and somatic cell count (SCC). Milk samples with detectable levels of Hp showed lower total protein and casein levels, whereas milk samples with detectable levels of SAA had lower casein number and lactose level. Samples with detectable levels of acute phase proteins also showed an elevated SCC. The results suggest that the presence of Hp and SAA in milk might indicate unfavourable changes in milk composition, especially in relation to protein quality

PRODUCT QUALITY IN THE CANADIAN DAIRY INDUSTRY

Supply management has been shown to increase the price of milk. Technological change has induced (and allowed) processors to substitute alternative inputs, many of which can be imported tariff-free, for the traditional ingredients to lower costs and maximize profit. Meanwhile, there has been a great deal of consolidation in the dairy processing industry. We analyse the effect of these trends on cheese quality by measuring the increase in casein imports. Results suggest that supply management is negatively affecting cheese quality, by increasing casein imports due to the higher milk price. Furthermore, we were able to calculate that approximately 9.8% of specialty cheese is produced used casein. A 22% ad valorem tariff is needed to drive casein imports down to zero.Industrial Organization,

Product Quality in the Canadian Dairy Industry

Supply management has been shown to increase the price of milk. Technological change has induced (and allowed) processors to substitute alternative inputs, many of which can be imported tariff-free, for the traditional ingredients to lower costs and maximize profit. Meanwhile, there has been a great deal of consolidation in the dairy processing industry. We analyse the effect of these trends on cheese quality by measuring the increase in casein imports. Results suggest that supply management is negatively affecting cheese quality, by increasing casein imports due to the higher milk price. Furthermore, we were able to calculate that approximately 9.8% of specialty cheese is produced used casein. A 22% ad valorem tariff is needed to drive casein imports down to zero.Food Consumption/Nutrition/Food Safety, Industrial Organization,

Modelling primary proteolysis in cheddar cheese in commercial cool stores : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Bioprocess Engineering at Massey University

One issue identified as a possible problem during the manufacture of cheddar cheese is the possibility of producing a non-uniform product. It was proposed that a pallet of cheese experiencing different time-temperature histories, depending on the position within the pallet, could cause the heterogeneity. This work involved the investigation of that issue. The level of primary proteolysis observed in cheese was measured over time in cheeses of different compositions, stored at different temperatures. The remaining intact α s ₁casein was measured using reverse phase high performance liquid chromatography. Several trends were observed during maturation. High temperatures caused a faster rate of disappearance of α s ₁casein. The temperature relationship followed Arrhenius law. High moisture content caused a faster rate of the disappearance of α s ₁casein. The level of rennet added to the milk during production had a directly proportional effect on the rate of the disappearance of α s ₁casein. Salt had no observable effect in the range investigated here. From the data a kinetic model was developed that described the rate of disappearance of α s ₁casein in terms of the temperature, the moisture content, and the level of rennet in the cheese. The heat transfer occurring in the commercial pallet of cheese was mathematically modelled and solved numerically. The heat transfer model was then applied to produce data describing the time-temperature profile throughout a pallet of cheese for a variety of possible industrial storage conditions. The kinetic model developed was then used to predict the extent of proteolysis in each case. It was found that there would be significantly different levels of proteolysis within a pallet of cheese that had undergone chilling. A 10% difference in the level of proteolysis between the surface and the centre was observed after chilling for 40 days. During freezing the difference in the level of proteolysis after freezing was complete ranged from 10-25%. It was found that the heterogeneity was reduced during the thawing process and that the greatest reduction in non-uniformity was observed when thawed at lower temperatures

Study of the interactions between milk proteins and hydroxyapatite particles : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Riddet Institute, Palmerston North, New Zealand

Hydroxyapatite (HA) and other insoluble calcium salts added to calcium-fortified milks are often described as inert, as they do not cause any protein aggregation and heat instability during heat treatment of the milk. However, it is well-known that proteins can interact with HA. The adsorption of milk proteins on HA has been demonstrated in many systems, for example in chromatography, bioceramic and dentistry applications, and has been shown to have consequence on the colloidal stability of HA, but has never been studied in food systems. The main objective of the present study was therefore to explore the adsorption of milk proteins onto HA particles under a range of physico-chemical conditions. The consequences of these interactions on the colloidal properties of the HA particles and on the stability of the milk proteins were investigated. It was shown that the five individual milk proteins aS-casein, ß -casein, ?-casein, ß- lactoglobulin and a-lactalbumin adsorbed onto the HA particles. A Langmuir model was used to fit the adsorption data and determine the affinity constant and maximum surface loads of the different proteins. The adsorption of the different milk proteins onto HA particles was found to be of competive nature. ß-casein and aS-casein were always preferred for adsorption over ?-casein, ß-lactoglobulin and a-lactalbumin. This was attributed to the presence of phosphoserine clusters in ß-casein and aS-casein, forming many anchor points capable of binding to the calcium sites of HA. ß-casein and aS-casein also adsorbed to higher maximum levels compared to ?-casein, ß-lactoglobulin and a-lactalbumin. Both ß-Casein and aS-casein were considered to self-associate or associate together in the adsorbed layer, therefore forming a thick layer onto the HA surface. Conversely, ?-casein, ß-lactoglobulin and a-lactalbumin adsorbed to lower maximum amounts and had lower affinities for HA, which was attributed to adsorption in a monolayer through their carboxyl groups binding to the calcium sites of HA. The amount of protein adsorbing to the HA surface was affected by the physico-chemical properties of the solution such as pH and ionic strength, for all proteins. Decreasing pH and increasing ionic strength decreased the electrostatic repulsive forces between HA and the proteins and the electrostatic repulsive forces within the protein molecules, which allowed more protein to adsorb onto the HA surface. Milk serum ions such as calcium, phosphate and citrate bound specifically onto HA particles, therefore competing with the milk proteins for adsorption. In milk, it was shown the addition of HA in milk disrupted the mineral equilibrium and the milk protein phase. When HA particles were added to milk, the milk serum ions bound to the HA surface. This caused the colloidal calcium phosphate to be released from the casein micelles and the casein micelles to dissociate. Therefore the casein micelles did not bind as intact micelles but as individual molecules or small aggregates onto the HA particles. The adsorption of milk proteins onto HA particles affected the colloidal properties of the HA particles in suspension. The adsorption of both caseins and whey proteins onto HA particles resulted in the particles becoming negatively charged, thus improving their suspension stability. Whey protein adsorption probably provided only electrostatic stabilisation, whereas casein adsorption also provided steric stabilisation. Overall, this work has provided a detailed understanding of the interactions between milk proteins and HA particles. Calcium fortification of milk using insoluble calcium salts such as HA should be approached using an awareness of these interactions, as they may have consequences on the stability of calcium fortified milks

PCR Based Genotyping of Lulu Cattle of Nepal for A1, A2 Type Beta-caseins

Lulu is an indigenous breed of cattle (Bos taurus) found in high altitude regions of western Nepal. Population of Lulu cattle has been declining due to introgression with other exotic breeds to increase milk productivity. Here we aimed at finding potential approach for conserving Lulu cattle and its assets by studying the milk contents and investigating which variant of beta-casein protein is present in this breed. Beta caseins are an abundant protein in cow milk with A1 and A2 being the most common genetic variants of this protein. Consumption of A1 type of milk has numerous health-related complications whereas A2 type of milk has numerous human health promoting factors. We used restriction fragment length polymorphism (RFLP) for determining the A1 and A2 variant of beta casein in Lulu cattle. For performing DNA extraction, we collected (n = 18) blood samples of Lulu from Mustang and (n=17) Nepal Agriculture research council farm. The amplified fragments in 3% agarose at 251bp and 213bp respectively confirmed the presence of both A1 and A2 gene in Lulu; however, A2 was of greater abundance. Our study indicated that Lulu has A2 variant of beta-casein predominantly. The gene frequency of A1A1 is 0, A1A2 is 0.06 and A2A2 is 0.94. We further found that the allele frequency of A1 and A2 is 0.03 and 0.97 respectively. We designed special primer for sequencing CSN2 genes since A2 type beta casein gene was predominantly seen on Lulu. The sequencing result further supports our RFLP result as most of our samples have “C” nucleotide SNP in amplified CSN2 gene sequence. The Chi-square value of the current study is 0.04 which supports Hardy-Weinberg equilibrium inferring that Lulu cattle are still in the pure state, where there is no genetic introgression with the exotic breed for the sake of improvement of productivity

Allelic Frequency of Kappa-Casein Locus (Asp148/Ala) in F1: Simmental (Bos Taurus) X Ongole Grade (Bos Indicus)

This study was conducted to detect the genetic variants (single nucleotide polymorphism) of kappa-casein locus (Asp148/Ala) in F1: Simmental (Bos taurus) x Ongole grade (Bos indicus), SIMPO. Genomic DNA was isolated from blood sample of 40 SIMPO (21 males and 19 females). A 780 bp specific fragment of kappa-casein gene spanning from the forth exon region (517 bp) to forth intron (263 bp) was successfully amplified. The result of the PCR-RFLP (Polymerase Chain Reaction - Restriction Fragment Length Polymorphisms) analysis using HindIII enzyme showed that two genotypes (AA and AB) were found at this locus in SIMPO. The frequencies of A and B alleles in SIMPO were 0.79 and 0.21, respectively. The frequency lies between B. taurus (Simmental) and B. indicus group