An Electrophoretic Study of the Protein in Skimmilk

Slatter, W.L.; Winkle, Q. Van

doi:10.3168/jds.s0022-0302(52)93796-x

Cited by 31 publications

(10 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, heat treatment reduces the susceptibility of /c-casein to hydrolysis by rennin (chymosin) (Powell & Palmer, 1935) thus limiting the use of NDM in cheesemaking. The decreased ability to hydrolyse /c-casein is apparently due to complex formation with /?-lg (Tobias et al 1952;Slatter & Van Winkle, 1952;McGugan et al 1954;Sawyer, 1968).…”

mentioning

confidence: 99%

Interaction between heated κ-casein and β-lactoglobulin: predominance of hydrophobic interactions in the initial stages of complex formation

Haque

Kinsella

1988

Journal of Dairy Research

104

View full text Add to dashboard Cite

Mixtures of /c-casein and /Mactoglobulin (/?-lg) were heated at 70 °C in 20 mM-imidazole buffer, pH 6-8 containing 20 mM-EGTA. Aggregation of the *-casein//?-lg mixture occurred within 90 s and susceptibility to hydrolysis by chymosin decreased significantly within 180 s even though covalent interaction was not detected until after 4000 s. UV-absorbance indicated initial structural destabilization of the heated /c-casein//?-lg mixture followed by a return (> 350 s) to a spectrum comparable to the native state, indicating molecular rearrangement. Apparent hydrophobicity of /c-casein decreased 80 % within 250 s compared to a 38% decrease for /?-lg. Under similar conditions, the /c-casein//?-lg mixture (1:1) showed a faster (2 -5 times) decrease in apparent hydrophobicity than /c-casein alone with concomitant exposure of acidic (hydrophilic) groups. The results suggested that the driving force for the rearrangement was mainly hydrophobic, i.e. entropic in origin. The tendency of heated and subsequently cooled /c-casein//?-lg to aggregate reached a maximum after heating at 70 °C for 720 s.

show abstract

mentioning

confidence: 99%

Interaction between heated κ-casein and β-lactoglobulin: predominance of hydrophobic interactions in the initial stages of complex formation

Haque

Kinsella

1988

Journal of Dairy Research

104

View full text Add to dashboard Cite

show abstract

“…As electrophoretic studies have proved of great value in the examination of systems containing a mixture of proteins, such as blood serum, it is not surprising to find an increasing number of attempts (211,212,213,214,215,216) to apply the technique to the examination of skim milk. The published evidence suggests that elucidation of the properties and behaviour of the milk proteins by this technique presents formidable problems.…”

Section: Physical Chemistrỹ (A) Proteins Generalmentioning

confidence: 99%

“…That identification of the components presents difficulties is indicated by the fact that numbers or letters, rather than names, have been used in referring to the components. Changes caused by heating (212,213) and centrifuging(2l4) as well as differences between colostrum (215) or late lactation milk (216) and full lactation milk have, so far, been studied by electrophoretic examination.…”

Section: Physical Chemistrỹ (A) Proteins Generalmentioning

confidence: 99%

Section C. Dairy chemistry and physics: Part I. Chemistry and physical chemistry

Aschaffenburg¹,

Ling²

1954

Journal of Dairy Research

View full text Add to dashboard Cite

nitrogen decreased; chloride percentage was high, and lactose percentage low; and there was a significant fall in yield. Schmid & Zollikofer(35) observed that the strain of a 30 km. journey of six cows to higher altitudes of the Alps caused an immediate decline in milk yield, fat and lactose percentages, while the chloride concentration increased. Data for bulk milk received in Norwegian dairies for the three periods 1927-30, 1937-40 and 1944-5 show but little variation(36), the levels of protein being 3-11, 3-19 and 3-11%, those of lactose 4-64, 4-87 and 4-83%, and those of fat 3-72, 3-80 and 3-69% respectively. Ash remained steady at 0-72%. The milk of six Sindhi cows and five buffaloes was examined for cholesterol by Gulvady, Kannan & Basu(37). Variations from 10 to 50p.p.m. were noted in the former and from 10 to 80 p.p.m. in the latter. In both species there was a sharp rise at the end of lactation. Evidence of proteolysis during the souring of the milk of cows and buffaloes is presented by Khambatta & Dastur(38). Variations in non-protein nitrogenous constituents of the milk of cows, buffaloes, goats and sheep were examined by Venkatappaiah & Basu(39). All the non-protein nitrogen constituents except creatinine were 2-5 times higher in the first colostrum of cows and buffaloes. The averages were respectively 258-2, 276-0, 323-9 and 432-9 p.p.m., of which urea was 44-8, 41-2, 64-9 and 32-9 p.p.m., uric acid 2-1, 0-9, 0-6 and 0-4 p.p.m. and amino-acids 15-7,18-6,16-6 and 22-2 p.p.m. Bakalor(40) found that the mean composition of 1608 samples of milk from forty-six producers taken on arrival at a Pretoria milk plant was: total solids 12-12%, fat 3-51 %, solids-not-fat 8-61%, ash 0-737%, protein 3-19% and lactose 4-69%. Fat and ash showed greatest variation. During the 12-month period 2-8% of the total number of samples fell below 3-0% fat, and 35-4% fell below 8-5% non-fatty solids. The milk from 25% of the producers contained less than 8-5% yearly average non-fatty solids. The author concludes that mastitis and poor feeding during the dry winter months are largely responsible for low non-fatty solid content. The Capetown city milk supply was shown by Bakalor(41) to have declined steadily in both fat percentage and solids-not-fat over the years 1934-46. In this period the fat varied between 3-51% in December to 3-79% in May, while solids-not-fat rose to 8-74% in July to September after reaching a minimum of 8-62% in January. The same author examined the milk supply of nine South African cities (42) during the period October 1949 to September 1950, and again noticed a frequent failure to reach the 8-5 % limit. In some cities all samples failed in this respect for one or more months in the year. Deficiencies in fat were much less frequent. Milk of 138 cows in the Parma region of Italy showed a decline in fat percentages from 3-86 to 3-52 % during the period 1939-43(43). The bulked milk of 30,000 cows in the province of Milan during the period 1930-9 was found by Fabris(44) to contain 3-49 % fat and 8-87 % solids...

show abstract

“…Eagles (286) has briefly reviewed their chemistry. The electrophoretic technique has been applied to the study of milk proteins (287,288,289,290,291,292); Heyndrickx & de Vleeshauwer (287,288) have shown differences in protein structure between colostrum, full lactation milk (287) and late lactation milk (288), and Ewerbeck (292) showed differences in the protein structure of cow's and human milk. Nandi & Rajagopalan (293) have used paper chromatography to confirm the similarity in the amino-acid make-up of cow's milk and of a vegetable milk designed by them.…”

Section: (Ii) Proteinsmentioning

confidence: 99%