Variations in chemical composition and in some physico-chemical properties of milk from a herd of lactating Alpine goats imported into Greece were determined from week 8 after parturition until the end of lactation (35 weeks, 35 samples). The average composition (g/100 g) of the milk was: fat 3·44, protein 3·35, casein 2·46, lactose 4·30, ash 0·79, total solids 11·76 and solids-not-fat 8·32. The average pH was 6·57 and titratable acidity was 16·76 (°D). The averaged density was 1·030. The mean mineral contents (mg/100 g) of the milk were: Na 53·12, K 157·67, Ca 140·06, P 110·00, Mg 13·59, citrate 106·97. All constituents studied as well as pH and density were significantly (P < 0·05) dependent on the stage of lactation. Titratable acidity was not significantly affected by stages of lactation. There were significant (P < 0·001) differences in Na/K and Ca/P ratios in the milk between lactation stages. Trends with lactation for each of the components and physico-chemical properties determined are reported and correlations between constituents in the milk are given.

An indirect enzyme-linked immunosorbent assay was successfully developed for the detection of defined amounts of cows' milk (1–50%) in sheeps' milk and cheese. The assay used polyclonal antibodies raised in rabbits against bovine caseins (BC). The anti-BC antibodies were recovered from the crude antiserum by immunoadsorption and elution from a column containing BC. The antibodies were biotinylated and rendered cows' milk specific by mixing them with lyophilized ovine and caprine caseins. ExtrAvidin-peroxidase was used to detect the biotinylated anti-BC antibodies bound to BC immobilized on 96-well plates. Subsequent enzymic conversion of substrate gave clear absorbance differences when assaying mixtures of sheeps' milk and cheese containing variable amounts of cows' milk.

The hyperinsulinaemic euglycaemic insulin clamp technique was used to compare insulin sensitivity in lactating ewes at two levels of feeding. Clamps were performed at two (restricted intake) or three (ad libitum intake) stages of lactation and also 30 d after drying off. Dose response curves for insulin were constructed using the glucose metabolic clearance rate (MCR) as the measure of glucose metabolism and these were statistically compared between stages of lactation within the feeding levels, and also between feeding regimes. Animals on a restricted feed intake showed a weight loss throughout lactation, coupled with a lower insulin sensitivity, as measured by the ED50 (concentration of insulin required to produce a half maximal increase in MCR), while those on ad libitum feeding showed a weight gain and a decreased insulin sensitivity in the dry period. Endogenous glucose production was less sensitive to inhibition by insulin in the animals subjected to restricted food intake, compared with those on the ad libitum regime, which suggested a major role for the plane of nutrition in adjusting the homeorhetic control of metabolism during lactation.

Changes in the concentrations of glucose and galactose were measured in the peripheral blood of ten piglets after they had ingested milk during a natural sucking. In addition, the mild stress associated with the experimental procedure was determined by sampling nine fasted piglets over a period of 9 to 12 min. During this period there was a significant increase in the concentration of glucose in the blood of the piglets but no change in the concentration of galactose. After milk ingestion during a natural sucking the concentrations of both glucose and galactose increased from 5·7 mM and 19 μM to reach peak values of 7·7 mM and 122 μM, respectively, by 30 to 35 min. The concentrations of glucose and galactose returned to initial values in 60–80 min and 80–100 min, respectively, after sucking. Since the change in the concentration of galactose in the peripheral blood was much lower than the change in the concentration of glucose, we conclude that galactose was rapidly removed by the livers of sucking piglets. However, after the ingestion of milk the percentage increase (from initial to peak values) in the concentration of galactose in the blood was much larger (650%) than the increase in the concentration of glucose (43%). Thus, we propose that the determination of galactose in the peripheral blood may provide a qualitative method for monitoring the digestion and absorption of milk lactose in sucking piglets.

Formation and adhesion of fouling deposit during heating of milk at a stainless steel surface were studied separately using a model apparatus. The amount of deposit and proportion of minerals present increased with increase in surface temperature. At 140 °C, the amount of deposit formed increased linearly with heating time, becoming more uneven in appearance. The variations of deposit formation at 140 °C with pH of the milk, with fat removal and with preheating were similar to those observed in the final heating section of continuous UHT plants. Deposits containing a higher proportion of protein were easier to remove. The remaining inner layer had a smoother appearance and contained a higher proportion of minerals than the original deposit. Depth profiling, using secondary ion mass spectrometry, showed that protein was concentrated on the outside of deposits with calcium phosphate being concentrated closest to the steel surface.

The nitrogen solubility index (NSI) method for the examination of caseinates was evaluated. It was found that widely scattering NSI values are mainly due to ineffective centrifugation and filtration of the caseinate dispersion. In order to avoid this, an improved combined centrifugation–filtration procedure was developed as an alternative to the original NSI method, using an Amicon micropartition system MPS-1 equipped with discs of filter paper. The micropartition devices can be centrifuged in a Gerber centrifuge of the type used for butyromctric fat determination. Several types of caseinates were evaluated with the new method and yielded a markedly smaller range of single values than were obtained with the NSI method.

In milk samples from 549 cows of the breeds Danish Jersey, Red Danish Dairy Cattle (RDM), and Black and White Danish Dairy Cattle (SDM) the genetic polymorphisms of the αs1, β and K-cascin and β-lactoglobulin (β-Lg) loci were determined by isoelectric focusing in agarose gels. The results of the screening were comparcd with results obtained by Larsen & Thymann (1966). In addition, the genetic linkage of the three casein loci was studied, and the association between milk protein genotypes and yields in first and second lactations of milk, fat and protein were investigated.

The distribution of genotypes of all four milk protein Systems was different from breed to breed.

For Jersey cows, significant differences in the gene frequencies from the results of the 1966 investigation were found for αs1 and K-casein and β-Lg. For SDM cows a change in the K-casein frequency had occurred whereas for RDM cows no changes were found.

Linkage between some of the casein loci was found within ail three breeds. For the RDM breed the possible linkage between αs1-casein and the other caseins could not be tested bccause nearly ail thc cows were homozygous for the αs1-cascin-B genotypes.

β-Casein genotypes were associated with yield parameters in ail breeds. The A2A2 genotype of this protein gave higher yields of milk, fat, and protein in the second lactation than thc A1A1 genotype.

Lactating goats were subjected to dehydration and to infusions of arginine vasopressin (AVP). Dehydration decreased milk production significantly but no changes were observed on the day of AVP infusion. The levels of AVP in plasma reached the same magnitude during both experimental procedures. AVP-immunoreactivity was immunocytochemically detected by light (peroxidase-antiperoxidase technique) and electron microscopy (immuno-Au technique on to glutaraldehyde-fixed, resin-embedded sections) in the mammary gland but not in the control experiments. In addition the cisternae of the rough endoplasmic reticulum in the secretory alveolar cells underwent significant swelling in response to the experimental procedures.

In order to examine the effect of heating on the changes in the linkage between colloidal Ca phosphate (CCP) and casein, high-performance gel chromatography of casein micelles disaggregated by 6 M-urea was carried out using 6 M-urea simulated milk ultrafiltrate as the effluent. Although the CCP content increased when whey protein-free (WPF) milk was heated at 60–90 °C for 10 min, almost no changes in the content of casein aggregates cross-linked by CCP were observed. The content of casein aggregates cross-linked by CCP decreased from 51·9 to 46·1% in WPF milk and from 52·3 to 43·6% in concentrated WPF milk on heating at 135–140 °C for 75 s, indicating the cleavage of the linkage between CCP and casein. The cleavage of the linkage between CCP and casein on heating was considered to occur without liberation of ester phosphate groups. It was suggested that the transformation of CCP to another form was responsible for the cleavage between CCP and casein on heating milk at high temperature

Changes in heat stability and Ca2+ activity of recombined concentrated milk (18% solids non-fat:8% fat) induced by the additions of 0·011–0·217 mol phosphate/kg skim milk solids (SMS), 0·022–0·217 mol citrate/kg SMS, 0·011–0·022 mol Ca/kg SMS and 0·016–0·067 mol EDTA/kg SMS were evaluated. Heat stability was assessed using an objective method which involved determination of viscosity after heating under controlled conditions. Low levels of added phosphate and citrate generally effected an acid shift of the viscosity–pH profile, while higher levels caused a broadening of the profile. Addition of CaCl2 at a level of 0·011 mol/kg SMS resulted in a narrowing of the viscosity–pH curve; additions of higher levels resulted in a non-heat stable recombined milk concentrate. EDTA also caused a narrowing of the viscosity–pH curve. The results highlight the importance of pH control for effective stabilization of recombined milk concentrates by additions of phosphate and citrate.

The separation of bovine milk proteins by fast protein liquid chromatography has been studied by ion-exchange chromatography on Mono S and Mono Q columns. The use of a non-ionic detergent, octyl-glucoside, made possible the separation of the four major casein components (αs1, αs2, β and κ) as well as minor caseins on the Mono S column using urea-containing buffers at pH 3·5. There was, however, considerable overlap between the αs1 and αs2-casein peaks. A good resolution was obtained with a low concentration of urea (3·5 M) and detergent (0·1%). These conditions allowed the separation of casein components in their native state in less than 50 min. The purity of isolated κ-casein was further improved by a second separation on a Mono Q column.

In five untreated goats, mammary extraction of plasma triglycerides increased at parturition. In five goats that had as much secretion as possible regularly removed from one mammary gland beginning on d 143 of gestation, the change of triglyceride extraction occurred several d before parturition in the emptied gland but at parturition in the contralateral control gland. The experimentally induced early increase of extraction of plasma triglycerides preceded the increase of prostaglandin Fα concentration in mammary secretion at parturition, and occurred despite abnormally high concentrations of progesterone in the secretion.

Cream feathering was studied in sixteen samples made from six brands of filter coffee. We have used a predictive rule, deduced from our studies of instant coffees, to determine the likelihood of feathering occurring in filter coffee samples upon the addition of coffee cream. The predictive rule makes use of 1,3,4,5-tetra-hydroxycyclohexane carboxylic acid-3-[(3,4) dihydroxycinnamate] (chlorogenic acid) concentration in the coffee, and the ratio of ultraviolet absorbances at 261 nm and 340 nm. We found good agreement between the predicted and observed behaviour of samples of filter coffee and conclude that the predictive rule is reliable for both instant and filter coffees. The effect of increased fat content in the cream was also studied.

Machine milking induced repeatable, short-term changes in thickness of the teat apex. These changes were measured with a spring-loaded caliper instrument under milking conditions that imposed differing forces on the teat apex. The mean percentage changes in teat end thickness (relative to the premilking values for individual teats) varied from 10% decrease up to 20% or more increase depending on the particular milking system used. The overall decrease in teat end thickness associated with cannula milking, milking at very low vacuum levels or milking with positive pressure pulsation may result from: (i) decrease in the intramammary pressure; and/or (ii) small changes in tone of teat musculature; and/or (iii) changes in the distribution of interstitial fluids in the teat apex. The overall increase in teat thickness caused by conventional or PKME milking systems results mainly from oedema (the extravascular accumulation of fluid). It is likely that milking equipment can, and should, be designed to minimize circulatory impairment resulting in oedema of the teat.

The effect of arginine on the production of extracellular lipase by Pseudomonas fluorescens 32A was studied. Arginine repressed lipase production when N was supplied partially or totally as arginine. Proteinase production was unaffected under the same conditions. Arginine did not repress lipase secretion when cells were pregrown in an arginine-containing medium; however, repression was found with uninduced cells. Several arginine-analogues were tested for the ability to repress lipase secretion and. of these, L-homoarginine and L-canavanine were the most effective. D-Arginine, L-arginine methyl ester, and L-ornithine did not cause repression. With the exception of glutamic acid and methionine, those amino acids that supplied N but not C for growth were found to repress lipase secretion. It is suggested that the accumulation of metabolic intermediate(s) may cause repression of lipase production.

Casein micelle suspensions, colloidal Ca phosphate-free casein solution and simulated milk ultrafiltrate (SMUF) were studied using high-resolution 43Ca and 31P NMR in the temperature range 4–64 °C. Only one 43Ca and one 31P signal was obtained for each solution. Signal intensities and line widths varied with the environment and were affected by the redistribution of Ca and P during heating and cooling. Based upon the temperature-dependent broadening of the 43Ca signal, five different Ca environments were discerned in the heated milk fractions. The Ca state, induced by heating of a casein-containing milk salt solution, differed from both the state of Ca present in micellar colloidal Ca phosphate and from the state of Ca induced by the heating of SMUF.

The microorganisms present in raw and pasteurized milk and the sources of contamination in the milk after it had arrived at the processing plant in Addis Ababa were studied. The lowest count registered for raw milk samples was 4 × 107 cfu/ml while the highest was 1 × 109 cfu/ml. Pasteurized milk had mesophilic aerobic counts of 7 × 105 cfu/ml as it left the pasteurizing unit, but the population increased 2- to 4-fold as a result of subsequent contamination. Of the total counts in raw milk, psychrophilic, thermoduric and thermophilic organisms made up 98·l, 1·4 and 0·5% respectively. In pasteurized milk, the amounts were 53·0, 39·5 and 7·5% respectively. Samples of milk pasteurized in the laboratory contained only 74·5% thermoduric and 25·5% thermophilic organisms. The isolates mostly belonged to the genera Bacillus, Streptococcus, Lactobacillus, Arthrobacter, Alcaligenes, Aeromonas and Pseudomonas. Cocci were more predominant than rod-shaped bacteria. Of the rod-shaped bacteria, 73% were Gram-negative. The utensils holding the raw and pasteurized milk and the plastic sheets used for bagging the pasteurized milk contributed unusually high numbers of bacteria which were either thermoduric or thermophilic. More isolates were obtained from the pasteurized than the raw milk. The keeping quality of the pasteurized milk was found to be much lower than that of the laboratory-pasteurized milk.

The present study identifies proline-specific peptidases found in Streptococcus cremoris AM2. These activities were present prcdominantly in the cytoplasmic fraction of the cells with minor amounts in cell membrane fraction. No evidence vvas found for such activities in either the extracellular fluid used to grow the cells, in the wash fraction or in the cell wall fraction. The involvement of these enzymes in release of free proline from proline-containing peptides is considered.

The acidic coagulation of casein micelles was monitored turbidimetrically at 400 nm using a Cary 219 spectrophotometer. Following acidification with HCI, the rate of coagulation during the initial stage of coagulation was proportional to the rate during the immediate subsequent stages, indicating that progressive stages of coagulation were controlled by similar factors and the slope at any portion of the reaction profile could be used to characterize the kinetics of the coagulation reaction. The rate of coagulation following acidification by glucono-δ-lactone was proportional to the reciprocal of the rate of acidification. The effects of environmental factors on the rate of the acidic coagulation of casein micelles over a range of pH values were evaluated from the smooth, hyperbolic profiles of pH v. coagulation rate. Determination of the pH required to initiate coagulation of casein micelles in skim milk ultrafiltrate at 5–25 °C, together with the maximum rates of coagulation at 5–25 °C, suggested that repulsive forces are reduced by acidification and con-sequently facilitate hydrophobic interactions resulting in the coagulation of casein micelles.

Affinity chromatography on a concanavalin A–Sepharose support was used to isolate two glycoprotein fractions from a heat- and acid-stable fraction of ovine milk. One of these glycoprotein fractions was purified by rechromatography on DEAE-cellulose to essentially a pure protein yielding a single band on gel electro-phoresis. The apparent Mr of this glycoprotein (GP2) as estimated by electrophoresis was 50500. It contained 8·88% carbohydrate and 0·61% P. The other glycoprotein fraction (GP3) contained 0·53% P and 17·76% carbohydrate including sialic acid, mannose, galactose, fucose, galactosamine and glucosamine. It appeared on electrophoresis in acrylamide gels as a slow-moving broad band. On similar treatment in the presence of sodium dodecyl sulphate it revealed four glycoprotein zones with apparent Mr of 15200, 18300, 23500 and 25300. Both GP2 and GP3 contained low amounts of aromatic and sulphur-containing amino acid residues and large amounts of Asp, Glu, Ser and Leu. GP3 is similar in some respects to the bovine milk heat- and acid-stable fraction constituent, component 3.