Changes in Curd Strength Due to Dialysis of Abnormal Against Normal Milk

Erwin, R.E.; Hampton, Otto; Randolph, H.E.

doi:10.3168/jds.s0022-0302(72)85485-7

Cited by 6 publications

(2 citation statements)

References 10 publications

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“…The same changes must occur during cheesemaking with high cell count milks although due to the time and temperature conditions involved the extent of casein breakdown will not be so extensive as in the above work. It seems probable that the action of proteinases, and losses in whey of the resulting peptides, is a major contributor to the losses in yield observed (Erwin et al 1972;Ali et al 1980) when cheese is made from mastitic milk as opposed to normal milk. Much of the proteinase activity will survive cheesemaking conditions and continue to act during cheese maturation, almost certainly with harmful effects on cheese quality in terms of texture and flavour, but these aspects remain to be investigated in detail.…”

Section: Discussionmentioning

confidence: 99%

Qualitative and quantitative determination of proteolysis in mastitic milks

Rham¹,

Andrews²

1982

Journal of Dairy Research

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SUMMARYProteolytic activity in mastitic skim-milk was often 5–10 fold higher than in normal milk, its level being related to somatic cell count but not precisely correlated with it. In milks with the highest levels of activity plasmin accounted for about one third of the total proteinase. A further third was sedimented with the micellar fraction together with the plasmin, but unlike plasmin, was not inhibited by addition of soyabean trypsin inhibitor (SBTI). The final third remained in the serum phase.Polyacrylamide gel electrophoresis (PAGE) showed that αsl- and β-caseins were degraded at about the same overall rate. The plasmin produced the usual readily identified fragments from β-casein, but incubation of mastitic milk also produced changes in patterns in the γ-casein region differing from plasmin-induced changes which were also apparent when the micellar fraction was incubated. As they were inhibited by SBTI, a second trypsin-like enzyme in addition to plasmin may also have been present. Other proteinase(s) not inhibited by SBTI was also associated with casein micelles and produced at least 3 characteristic protein fragments seen on PAGE. The serum phase proteinase(s) was likewise not inhibited by SBTI, and did not produce any well-defined electrophoretic bands, suggesting a rather non-specific breakdown of caseins. After separation of mastitic whole milk, a considerable proportion of the proteolytic activity was found in the cream phase. The proportion was enhanced by freezing and thawing, and the enzyme appeared to be identical to the SBTI-resistant micellar proteinase.Because of the considerable proteolysis likely to occur under the time and temperature conditions involved, our results may provide some explanation for the problems encountered in cheesemaking with mastitic milks (e.g. yield losses, poor curd strength and off-flavour development).

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Section: Discussionmentioning

confidence: 99%

Qualitative and quantitative determination of proteolysis in mastitic milks

Rham¹,

Andrews²

1982

Journal of Dairy Research

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“…The composition of cheese and cheese yield are influenced by the milk used so that cheeses made from mastitic milk are usually of poor quality and yields are low (Sommer & Matsen, 1935;Scott, 1967;Hampton & Randolph, 1969;Tallamy, Randolph & Dill, 1969;Erwin, Hampton & Randolph, 1972). As part of our studies on the influence of cold storage on casein distribution in milk and on cheese-making (Ali, Andrews & Cheeseman, 1980), it was important to study the effects of varying somatic cell count on both casein distribution between the soluble and micellar phases in milk and also on parameters related to subsequent cheese-making, using both fresh and stored milks.…”

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confidence: 99%

Influence of elevated somatic cell count on casein distribution and cheese-making

Ali¹,

Andrews²,

Cheeseman³

1980

Journal of Dairy Research

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The effects of increased somatic cell count, whether caused by infection or by experimental infusion of bacterial endotoxin, on the distribution in milk of caseins between the micellar and soluble forms were investigated. The relationship of somatic cell count to some cheese-making parameters was also studied. With quite modestly elevated cell counts (2-3 x 10 6 /ml) increases of up to 37 % in total casein in the soluble phase were observed, most of which was contributed by /^-casein, while K-and a sl -caseins increased only slightly. With storage at 4 °C, the concentrations of all the caseins, Ca and phosphate in the soluble phase increased substantially during the first 48 h, but this was followed by a slight decline on further storage. Rennet clotting time, losses of fat in whey, curd moisture, and losses in curd yield and rigidity were all greater the higher the somatic count. Clear differences were detectable in these parameters between milks of very low cell count (e.g. 5 x 10 4 cells/ml) and milks with counts more typical of those found in bulk supplies (e.g. about 5 x 10 5 cells/ml). If these findings can be reproduced in commercial practice even a modest reduction in bulk milk somatic cell counts might be expected to bring definite benefits.Udder infections modify milk composition by altering membrane permeability within the mammary gland and by reducing synthesis of milk components. Mastitisinduced changes in the gross composition of milk as well as changes in the relative proportions for the individual milk proteins and minerals are well established (O'Donovan

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Secondary (Non-enzymatic) Phase of Rennet Coagulation and Post-coagulation Phenomena

Green¹,

Grandison

1993

Cheese: Chemistry, Physics and Microbiology

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Changes in Curd Strength Due to Dialysis of Abnormal Against Normal Milk

Cited by 6 publications

References 10 publications

Qualitative and quantitative determination of proteolysis in mastitic milks

Qualitative and quantitative determination of proteolysis in mastitic milks

Influence of elevated somatic cell count on casein distribution and cheese-making

Secondary (Non-enzymatic) Phase of Rennet Coagulation and Post-coagulation Phenomena

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