bluuebunny/crossref_metadata_2025 huggingface dataset:
Accelerated ripening of Feta cheese, with heat-shocked cultures or microbial proteinases
Authors: Vafopoulou Anna , Alichanidis Efstathios , Zerfiridis Gregory
Published: June 2009

Accelerated ripening was successfully achieved in Feta cheese by the addition of a heat-shocked culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, or neutral or acid microbial proteinase. Optimum levels of microbial proteinases were established at which trichloroacetic acid-soluble N (TCA-N) compounds were increased by about 35% in 40 d. Treated cheeses of this age had flavour intensities and body and texture qualities typical of 80 d-old control cheeses. Any further increase in TCA-N by adding larger amounts of enzyme resulted in bitterness. Heat-shocked culture treated cheeses developed similar characteristics to those prepared with neutral or acid proteinases. In contrast to the control cheese, it was necessary in the experimental cheeses to add minute amounts of lamb lipase (0·1–0·2 g/100 kg milk) to the cheese milk to keep the flavour balance. Best organoleptic characteristics were obtained from cheese treated with heat-shocked culture, followed by those treated with neutral or acid proteinase.
Prevention of gastrointestinal infection using immunobiological methods with milk fermented withLactobacillus caseiandLactobacillus acidophilus
Authors: Perdigon Gabriela , de Macias Maria E. Nader , Alvarez Susana , Oliver Guillermo , de Ruiz Holgado Aida A. Pesce
Published: June 2009

The protective effect of feeding milk fermented with a mixture ofLactobacillus caseisp. andLb. acidophilussp. againstSalmonella typhimuriuminfection in mice was compared with that obtained feeding milks fermented with these microorganisms individually. The survival rate obtained after oral infection withSal. typhimuriumwas 100% in mice pretreated by feeding during 8 d with the mixture ofLb. caseiandLb. acidophilusfermented milks. Similar treatments with the individual milks were ineffective. Moreover, mice became more susceptible to infection withSal. typhimuriumafter such treatment. The colonization of liver and spleen with the pathogen was markedly inhibited by the pretreatment with the mixture of fermented milk, while such inhibition was not observed using theLb. caseiandLb. acidophilusmilks. The highest levels of anti-salmonellae antibodies in serum and in intestinal fluid were found in the group of mice fed with the mixture and withLb. caseifermented milk respectively. However, this latter milk was not effective in protecting againstSal. typhimurium. When the mice were first infected withSal. typhimuriumand then fed with the mixture of fermented milks, pathogen colonization was not prevented. The results suggest that the augmentation of resistance to salmonellae caused by the treatment withLb. casei-+Lb. acidophilus-fermented milk was due to the anti-salmonellae protective immunity mainly mediated by the mucosal tissue. Milk fermented with this mixture could be used as an immunobiological method to prevent gastrointestinal infection.
Cost benefit analysis of bovine mastitis in the UK
Authors: Beck Harvey S. , Wise William S. , Dodd Frank H.
Published: June 2009

Bovine mastitis reduces the yield and quality of milk and increases the rate of culling and veterinary costs. This reduces the profitability of farm milk production but the calculation of the extent of this economic loss is complex because of the many factors involved and deficiencies in the evidence on the relationship between the disease and various production factors. This paper examines the available evidence for the UK and provides a consistent analytical framework within which the benefits arising from reduced mastitis in dairy herds constrained by quota can be considered. It is estimated that since 1970 the farms that have followed the recommended control procedures have reduced the average annual number of cases of clinical mastitis from 135 to 40 cases/100 cows each year, while the quarters remaining uninfected for a whole year has increased from 65 to 80% of the total quarters. The costs of the main control procedures (e.g. £8–60/cow for dry-cow therapy and teat dipping or spraying) are broadly covered by the reduction in clinical mastitis, leaving the benefits of reduced subclinical infection (e.g. £3810 for a 100 cow herd unconstrained by quota and achieving the average reduction in infection) as a substantial bonus. The imposition of quotas reduces the financial benefit of mastitis control but it still remains a worthwhile investment. The results of this analysis can be used to suggest maximum costs of additional new control measures produced by research. It also indicates that there is considerable value in production research which gives more precise knowledge of production Systems, thus allowing producers to respond optimally to quota cuts.
Effects on milk yield and composition of intra-abomasal infusions of sodium caseinate, an enzymic hydrolysate of casein or soya-protein isolate in dairy cows
Authors: Choung Jai-Jun , Chamberlain David G.
Published: June 2009

Six lactating dairy cows receiving a diet of grass silage and barley were given the following treatments as infusions into the abomasum, in a replicated 3 × 3 Latin square with 10 d periods: sodium caseinate (C), an enzymic hydrolysate of casein (CH) and soya-protein isolate (SPI). The C and CH treatments supplied ~ 185 g/d and the SPI treatment ~ 160 g/d of amino acids. Milk yield was similar for all treatments. Yields of milk protsein were 605, 604 and 582 (P > 0·05) g/d for C, CH and SPI respectively. For C, CH and SPI respectively, concentrations (g/kg) of fat were 39·6, 45·7 and 41·9 and yields (g/d) of fat were 790, 931 and 827; values for CH were significantly (P < 0·01) higher than for either of the other treatments. It is concluded that the form in which amino acid residues of casein are supplied to the abomasum (protein v. peptide–amino acid mixtures) can influence the partition of use of nutrients between body tissues and the mammary gland.
Effect of the A and B variants of both αs1- and κ-casein on bovine casein micelle solvation and κ-casein content
Authors: Anema Skelte G. , Creamer Lawrence K.
Published: June 2009

Casein micelle solvation, a micelle characteristic that is sensitive to many factors, has been measured by a centrifugation technique at 30 °C for a series of uncooled fresh skim milks at pH 6·3, 6·6, 6·9 and 7·1. The relative αs-(αs1- plus αs2-), β– and κ-casein contents of all centrifuge pellets and supernatants were determined by a standardized electrophoretic method. The calcium and phosphate contents of a number of the pellets and milk samples were also determined. Solvation of micelles from milks with various genetic variants of β-lactoglobulin (A and B), αs1-casein (A and B) and κ-casein (A and B) was often found to be lower for milks containing either the B variant of αs1-casein or the A variant of κ-casein. It was also found that these two variant caseins were associated with a lower κ-casein content of the milks and the micelles, which is consistent with the lower solvation as κ-casein is associated with smaller micelle size and greater solvation. The solvations also seemed to increase during the lactation period. It is possible that some of the other features of milk and its products that have been ascribed to the differences in functional character between the A and B variants of αs1-casein may be partly caused by the increased level of κ-casein. The reason for the association of the A variant of αs1-casein with higher concentrations of κ-casein (and micelle solvation) is not obvious but possibly the haplotype αs1-casein A, β-casein A1, κ-casein A contains a controlling sequence in the chromosomal DNA that enhances expression of the κ-casein gene.
Effect of the levels of N fertilizer, grass and supplementary feeds on nitrogen composition and renneting properties of milk from cows at pasture
Authors: Hermansen John E. , Ostersen Steen , Aaes Ole
Published: June 2009

In a 2 × 2 × 3 factorial design grazing experiment we investigated the effect of fertilizer (none or 240 kg N/ha), amounts of clover grass available (low or high) and type and level of daily supplementary feed for each cow (3·5 kg barley, 3·5 kg concentrate mixture rich in protein and fat, or both, 7 kg) on the protein composition and renneting properties of their milk. The experiment was carried out in two successive grazing seasons (years) and included a total of 79 Danish Holstein cows. The effect on milk protein composition was determined in both years whereas the effect on renneting properties was determined only in the second year. Fertilization of the clover grass significantly decreased total milk protein concentration (− 1·4 g/kg; P < 0·01) and tended also to decrease the relative proportion of whey protein N. Fertilization had no effect on renneting properties. Increased availability of clover grass significantly increased milk protein concentration (1 g/kg; P < 0·05) and resulted in significantly poorer renneting properties, that is increased clotting time (P < 0·01) and decreased coagulum development. These effects seemed to be mediated through an effect on the pH of the milk (+ 0·05; P < 0·05) as the effect was markedly reduced when statistical correction was made for the actual pH. Use of the protein- and fat-rich concentrate mix (3·5 kg) significantly reduced the total protein content of the milk (P < 0·05) and increased the proportion of non-protein N (NPN) in total N compared with use of the other supplementary feeds (P < 0·05). We found no effect on renneting properties of the different supplementary feeds. Throughout the grazing season and independent of the main treatments, the NPN proportion of milk N increased at the expense of casein N. At the same time, renneting properties became poorer, especially with high clover grass availability.
Disulphide arrangement in bovine caseins: localization of intrachain disulphide bridges in monomers of κ- and αs2-casein from bovine milk
Authors: Rasmussen Lone K. , Højrup Peter , Petersen Torben E.
Published: June 2009

Naturally occurring monomeric κ-casein and αs2-casein in bovine milk were purified by ion-exchange chromatography in order to localize potential intrachain disulphide bridges. Enzymic cleavage of the proteins followed by mass spectrometry and amino acid sequence analysis of cystine-containing peptides revealed the presence of an intrachain disulphide bond in both proteins.
Distribution of lysosomal enzymes within the non-secretory epithelium of the bovine mammary gland
Authors: Mattila Tuna , O'Boyle Denise , Frost Alan J.
Published: June 2009

The levels ofN-acetyl-β-glucosaminidase (NAGase) and acid phosphatase were analysed in tissue from the teat and lactiferous sinus epithelia of dairy cows at different stages of lactation. Enzyme levels were lower in the epithelia of the teat sinus than of the lactiferous sinus. For both enzymes, levels were highest in tissue from post-partum glands, lowest in those from dry and mid-lactation glands. In involuting glands the levels were high, but not as high as the post-partum glands.
Antimutagenic activity of whole casein on the pepper-induced mutagenicity to streptomycin-dependent strain SD 510 ofSalmonella typhimuriumTA 98
Authors: Hosono Akiyoshi , Shashikanth Kunigal N. , Otani Hajime
Published: June 2009

When the antimutagenic activity of milk or cultured milk components on the pepper-induced mutagenicity to streptomycin-dependent strain SD 510 ofSalmonella typhimuriumTA 98 was investigated, whole casein showed a significant antimutagenic activity. Heating at 121 °C for 15 min completely destroyed the antimutagenic activity of casein, which was temperature dependent. While acid or papain digestion resulted in the loss of antimutagenic activity of casein, trypsin digestion had little effect although the digestion of casein by each proteinase was over 75%. β-Casein, egg albumin, and bovine serum albumin also had a similar antimutagenic activity to that of whole casein.
Small-angle X-ray scattering investigation of the micellar and submicellar forms of bovine casein
Authors: Pessen Helmut , Kumosinski Thomas F. , Farrell Harold M.
Published: June 2009

Small-angle X-ray scattering was performed on whole casein under submicellar (Ca2+ removed) and micellar (Ca2+ re-added) conditions. Submicellar scattering curves showed two Gaussian components which were interpreted in terms of a spherical particle with two concentric regions of different electron density, a relatively compact core of higher electron density and a looser shell. Normalized scattering curves and calculated distance distribution functions were consistent with this picture. Micellar scattering data, which can yield only cross-sectional information related to a window of scattered intensities, could be analysed by a sum of three Gaussians with no residual function. The two Gaussians with the lower radii of gyration were again taken to indicate the two concentric regions of different electron density of inhomogeneous spherical particles; the third Gaussian was shown to reflect the packing number of these particles within a cross-sectional portion of the micelle, which was 3:1 for this system. These results are a strong indication that submicellar inhomogeneous particles containing hydrophobically stabilized inner cores exist within the colloidal micelle.
A model for the assembly of bovine casein micelles from F2 and F3 subunits
Authors: Ono Tomotada , Obata Takayuki
Published: June 2009

Casein micelles were reassembled from mixtures of F2 and F3 subunits, the major subunits of bovine casein micelles, in varying ratios. The average radius of the reassembled micelles was inversely proportional to the F2 content. Based on this relationship, a model for casein micelle assembly is proposed in which the F3 subunit forms the core of the micelle with F2 subunit occurring on the surface. Micelle size can subsequently be defined by the F2 content.
Yield and composition of milk from lactating mares: effect of lactation stage and individual differences
Authors: Doreau Michel , Boulot Sylviane , Barlet Jean-Pierre , Patureau-Mirand Philippe
Published: June 2009

The yields and composition of milk from nursing mares were studied during the first two months of lactation in 11 mares of heavy breeds (784 kg). Daily yield increased from 21·7 to 24·6 kg between weeks 1 and 8 of lactation. Fat, protein, gross energy and Ca concentrations significantly decreased when lactose content increased during this period. Individual variations were higher for yield than for composition. Casein, whey protein and non-protein N (56, 34 and 10% of crude protein, respectively) and amino acid composition did not vary between weeks 1 and 8 of lactation.
Purification of disulphide-linked αs2- and κ-casein from bovine milk
Authors: Rasmussen Lone K. , Petersen Torben E.
Published: June 2009

Naturally occurring disulphide-linked αs2- and κ-casein in bovine milk were purified by gel chromatography on a column of Sepharose CL-6B. Four fractions (A–D) were obtained by elution with ammonium acetate-urea buffer. Fractions A and B, identified by SDS gel electrophoresis and amino acid sequence analysis, corresponded to disulphide-linked κ-casein and αs2-casein respectively. Fraction C consisted of a mixture of αs1-, αS2-, and β-casein. Separation of fraction C into its components was achieved by reversed-phase HPLC. The stability of the disulphide bridges in αs2- and κ-casein was shown to differ with respect to reducing agents (dithioerythritol and 2-mercaptoethanol).
Denaturation, aggregation and heat stability of milk protein during the manufacture of skim milk powder
Authors: Singh Harjinder , Creamer Lawrence K.
Published: June 2009

The effect of preheat treatment, evaporation and drying in a commercial plant on the denaturation of βlactoglobulin and α-lactalbumin, their incorporation into the casein micelle and the heat stability characteristics of the milks and powders were determined. Preheat treatments between 110 °C for 2 min and 120 °C for 3 min denatured between 80 and 91% of β-lactoglobulin and between 33 and 45% of α-lactalbumin. Evaporation increased the extent of denaturation but spray drying did not increase it further. The incorporation of α-lactalbumin and βlactoglobulin into the micelles was markedly less than the amount that denatured and was not a constant ratio to it. Heat coagulation times at 140 °C of milks, concentrates and powders diluted to the original milk concentration were measured as a function of pH. In general, the greater the collective heat treatment, the shorter the time required to achieve coagulation. Spray drying shifted the peak positions in the pH-heat coagulation time profiles. In contrast, heat coagulation times (measured at 120 °C) of concentrates and powders diluted to 20% total solids content increased with the severity of the preheat treatment. Surprisingly, spray drying markedly increased the heat coagulation times of the diluted concentrates.
Effect of lactic starter inoculation on chemical, microbiological, rheological and sensory characteristics of La Serena cheese
Authors: Medina Margarita , Del Pozo Buensuceso Fernandez , Rodríguez-Marin M. Asunción , Gaya Pilar , Nuñez Manuel
Published: June 2009

The influence of lactic starter inoculation on La Serena cheese characteristics was investigated in duplicate experiments, each consisting of a vat inoculated with 1%Lactococcus lactissubsp.lactisskim milk culture and a control vat without lactic starter.Lc. lactisinoculation achieved a significant pH decrease in the interior and on the surface of cheese, which ranged from 0·09 to 0·25 units throughout ripening. Breakdown of αs1- and β-casein and formation of soluble N fractions were retarded byLc. lactisinoculation. Levels of αs1-casein, β-casein and pH 4·6-soluble N after 60 d were respectively 30·4, 34·9 and 28·8% in cheese made with starter and 18·4, 23·0 and 34·2% in control cheese. More acidic conditions in the interior of cheese made with starter resulted in a reduction of Enterobacteriaceae, coliform and staphylococci counts, which after 60 d were respectively 2·55, 2·40 and 0·29 log units lower than in control cheese. The firmer texture obtained throughout maturation for cheese made with starter was attributed to retarded proteolysis and lower pH value. Cheese flavour quality and intensity were significantly impaired byLc. lactisinoculation.
Effect of vegetable and animal rennet on chemical, microbiological, rheological and sensory characteristics of La Serena cheese
Authors: Nuñez Manuel , Pozo Buensuceso Fernandez Del , Rodríguez-Marin M. Asunción , Gaya Pilar , Medina Margarita
Published: June 2009

The characteristics of La Serena cheese produced using animal rennet in place of the traditional vegetable rennet were evaluated. Total solids, fat and total N were higher in whey from animal rennet than in whey from vegetable rennet. Cheese produced using animal rennet had a higher moisture content and a lower pH. Proteolysis was more rapid in the cheese produced with vegetable rennet than in the cheese produced with animal rennet, but there was less lipolysis. Enterobacteriaceae and coliform counts were respectively 1·7 and 1·4 log units higher in 60 d vegetable rennet cheese than in 60 d animal rennet cheese. Softening of cheese texture was considerably more pronounced in vegetable rennet cheese, which also showed significantly higher flavour quality and intensity.
Intracellular pH and the role of D-lactate dehydrogenase in the production of metabolic end products byLeuconostoc lactis
Authors: Fitzgerald Richard J. , Doonan Shawn , McKay Larry L. , Cogan Timothy M.
Published: June 2009

The kinetics of lactate dehydrogenase fromLeuconostoc lactisNCW1 were studied. The pH optimum for the enzyme depended on the concentration of pyruvate used in the assay and the enzyme displayed an ordered mechanism with respect to substrate binding. TheKmfor pyruvate and NADH and theVmaxof the enzyme decreased 20–, 30– and 6-fold respectively as the pH decreased from 8·0 to 5·0. No activators were found and none of the intermediates of the phosphoketolase pathway tested inhibited the enzyme. ATP, ADP, GTP and NAD+were inhibitory. The intracellular volume (Volin) and intracellular pH (pHin) decreased as the extracellular pH (pHex) decreased. Co-metabolism of citrate and glucose affected the Volinbut did not affect the pHin, which decreased by 0·6 units per unit change in pHex; at pH 7·0, the pHinand pHexwere equal. The results suggest that pHinmay play a role in determining the production of diacetyl and acetoin at low pH byLeuconostoc.
Physical characteristics of the bovine teat canal and their influence on susceptibility to streptococcal infection
Authors: Lacy-Hulbert S. Jane , Hillerton J. Eric
Published: June 2009

Physical characteristics of the bovine teat canal were examined for their influence on susceptibility to intramammary infection. All quarters of 18 cows were inoculated with 2 × 105 cfu Streptococcus agalactiae (Trial 1) and 20 cows with 105 cfu Str. Uberis (Trial 2) 3–4 mm into the teat canal every 3 d for 12 d. Incidence of quarter infection was similar for both pathogens, 30/72 (42%) in Trial 1 and 32/80 (40%) in Trial 2. Logistic regression analysis showed that probability of infection by Str. Agalactiae increased significantly with an increase in quarter peak flow rate (P < 0·05) whereas probability of infection increased for Str. Uberis with a decrease in teat canal length (P < 0·05). A significantly higher (P < 0·001) incidence of infection by Str. Uberis was observed in quarters that contained a low wet weight (< 1·8 mg) of removable keratin compared with those that contained > 1·8 mg keratin, but there was no correlation between weight of keratin and length of the teat canal. Infections by Str. Uberis took significantly less (P < 0·05) time to show a rise in somatic cell count above 7·5 × 105 cells/ml than Str. agalactiae. The results provide evidence that these pathogens use different mechanisms to pass through the teat canal.
Effects of physicochemical factors on the secondary structure of β-lactoglobulin
Authors: Boye Joyce I. , Ismail Ashraf A. , Alli Inteaz
Published: June 2009

Fourier transform infrared spectroscopy and differential scanning calorimetry were used as complementary techniques to study changes in the secondary structure of β-lactoglobulin under various physicochemical conditions. The effects of pH (3–9), NaCl (0–2 M), and lactose, glucose and sucrose (100–500 g/l) in the temperature range 25–100 °C on the conformation sensitive amide I band in the i.r. spectrum of β-lactoglobulin in D2O solution were examined. The 1692 cm−1 band in the amide I band profile had not been definitively assigned in previous studies of the i.r. spectrum of β-lactoglobulin. The decrease in this band at ambient temperature with time or upon mild heating was attributed to slow H-D exchange, indicating that it was due to a structure buried deep within the protein. The disappearance of the 1692 cm−1 band on heating was accompanied by the appearance of two bands at 1684 and 1629 cm–1, assigned to β-sheets. The 1692 cm−1 band was therefore attributed to a β-type structure. β-Lactoglobulin showed maximum thermal stability at pH 3 and was easily denatured at pH 9. On denaturation, the protein unfolded into more extensive random coil structures at pH 9 than at pH 3. After 10 h at pH 9 (25 °C), β-lactoglobulin was partly denatured. Heating to 60–80 °C generally resulted in the loss of secondary structure. At all pH values studied, two new bands at 1618 and 1684 cm−1, characteristic of intermolecular β-sheet structure and associated with aggregation, were observed after the initial denaturation. Differential scanning calorimetry studies indicated that the thermal stability of β-lactoglobulin was enhanced in the presence of sugars. The Fourier transform i.r. results obtained provide evidence that sugars promoted the unfolding of β-lactoglobulin via multiple transition pathways leading to a transition state resisting aggregation.
Effect of high hydrostatic pressure on the enzymic hydrolysis of β-lactoglobulin B by trypsin, thermolysin and pepsin
Authors: Stapelfeldt Henrik , Petersen Per Hjort , Kristiansen Kristian Rotvig , Qvist Karsten Bruun , Skibsted Leif H.
Published: June 2009

Hydrolysis of β-lactoglobulin B (β-lg B) by pepsin, a process slow at ambient conditions, is facilitated at a moderately high hydrostatic pressure such as 300 MPa, corresponding to an apparent volume of activation ΔV# = −63 ml mol−1 at pH 2·5, 30 °C and Γ/2=0·16. Digestion of β-lg by trypsin and thermolysin is likewise enhanced by pressure, and the pressure effect has been traced to pressure denaturation of β-lg B, which by high-pressure fluorescence spectroscopy has been shown to have a large negative volume of reaction, ΔV° = −98 ml mol−1, at pH 6·7, 30 °C and Γ/2 = 0·16. Pressure denaturation is only slowly reversed following release of pressure and the enhanced digestibility is maintained at ambient pressure for several hours.
Effects of somatic cell count and stage of lactation on raw milk composition and the yield and quality of Cheddar cheese
Authors: Auldist Martin J. , Coats Stephen , Sutherland Brian J. , Mayes Jeffery J. , McDowell Graham H. , Rogers Graeme L.
Published: June 2009

The effects of somatic cell count and stage of lactation on the yield and quality of Cheddar cheese were investigated. Cheese was manufactured in a pilotscale factory using milk of low bulk milk cell count (BMCC) from herds in early (LE) and late (LL) lactation, and milk of high BMCC from herds in early (HE) and late (HL) lactation. The deleterious effect of an elevated BMCC on product yield and quality in late lactation was clear. Cheese made from LL milk was significantly superior to that made from HL milk for most yield and quality characteristics measured. Stage of lactation also affected cheese yield and quality, as evidenced by the lower recovery of fat and poorer flavour score for cheese from LL milk compared with that manufactured from LE milk. The observed differences could be explained largely by differences in raw milk composition. We conclude that the effect of stage of lactation was magnified by an elevated BMCC, and that many of the problems encountered when processing late season milk could be overcome by containing mastitis at this time.
Acute phase response in heifers with experimentally induced mastitis
Authors: Hirvonen Juhani , Pyörälä Satu , Jousimies-Somer Hannele
Published: June 2009

Ten pregnant heifers were inoculated in both hind udder quarters with a mixture ofActinomyces pyogenes, Fusobacterium necrophorumandPeptostreptococcus indolicus. Development of the experimental mastitis was monitored by sequential clinical and bacteriological examinations, and by blood acute phase protein profiles. Sequential changes in plasma fibrinogen, serum haptoglobin, acid-soluble glycoproteins and α1-proteinase inhibitor activity were analysed and compared with both the clinical and bacteriological findings and the final outcome of the disease after calving. All ten heifers developed moderate to severe clinical mastitis. Four recovered completely, had a normal lactation after calving and exhibited only transient fever and moderate local signs. In six of the heifers the course of the disease was severe, and the inoculated quarters failed to produce milk after calving. The acute phase response of the four heifers that recovered was also significantly milder than that of the other six heifers. Haptoglobin and acid-soluble glycoproteins were most effective in indicating the severity of the infection and predicting the final outcome of the disease. Fibrinogen was a reliable indicator for detecting the presence of bacterial infection in all heifers. α1-Proteinase inhibitor activity was of low diagnostic value in this study.
Electroacoustic determination of size and zeta potential of casein micelles in skim milk
Authors: Wade Theresa , Beattie James K. , Rowlands William N. , Augustin Mary-Ann
Published: June 2009

Measurements of the zeta potential and particle size of casein micelles in skim milk suspensions at natural and lower pH have been made using the technique of electroacoustics. This technique requires no dilution or change of environment of the casein micelles. The zeta potential obtained at natural pH for a commercial skim milk suspension was −18 mV; it became less negative with decreasing pH. The median particle size observed at natural pH for a commercial skim milk suspension was 0·2 εm, in good agreement with previously reported values. The particle size increased as the pH was decreased.
Effect of incorporation of cottage cheese whey solids andBifidobacterium bifidumin freshly made yogurt
Authors: Baig Mirza I. , Prasad Velore
Published: June 2009

Fresh rennet-coagulated cottage cheese whey was vacuum concentrated to 400 g total solids kg−1, and part of this evaporated whey was acidified to pH 4·6 to prepare whey protein concentrate. Both products were used separately to replace non-fat dried milk in yogurt. Diacetyl concentration increased on fortification with whey protein concentrate, and acetaldehyde increased with evaporated whey. However, the use ofBifidobacterium bifidumas a supplementary starter culture in addition toStreptococcus thermophilusandLactobacillus delbrueckiisubsp.bulgaricusreduced the concentration of diacetyl and acetaldehyde. Incorporation of whey solids stimulated the growth ofStr.thermophilusandBifid. bifidumin yogurt but the count ofLb. bulgaricuswas reduced whenBifid. bifidumwas incorporated. Examination of the organoleptic properties of the yogurts showed that both forms of whey solids were satisfactory replacements for non-fat dried milk. Fortification by whey protein concentrate improved the textural properties. Supplementation byBifid. bifidumhad only a marginal effect on the flavour of the product.
Cholesterol oxidation in feta cheese produced from high-temperature bleached and from non-bleached butteroil from bovine milk
Authors: Nielsen Jacob H. , Olsen Carl Erik , Lyndon Jeff , Sørensen John , Skibsted Leif H.
Published: June 2009

During chill storage, cholesterol oxidation in feta cheese produced from bovine butteroil bleached at high temperature was compared with cholesterol oxidation in feta cheese produced from non-bleached butteroil. The bleaching was performed at two different temperatures, 265 and 280 °C, and the oil was bleached for 2·4, 3·8 or 4·3 min; a reference feta cheese was produced without bleaching. All cheeses were stored in brine at 4 °C, and cholesterol oxidation was measured during a storage period of 5 months. For the first 11 weeks of storage, the concentration of cholesterol oxides was comparable for the bleached feta cheeses, but on longer storage the concentration of oxysterols was highest in feta cheeses produced from the butteroil bleached at 280 °C. The bleaching temperature rather than the bleaching time affected cholesterol oxidation, which was minimal in the non-bleached reference cheese throughout the storage period compared with the bleached feta cheeses. 7-Ketocholesterol was found to be the dominant oxysterol in the feta cheeses at the end of the storage, comprising ∼ 50% of the total cholesterol oxides. In feta cheeses based on butteroil bleached at 265 °C, the concentration of 7-ketocholesterol ranged from 3·7 to 4·9 µg/g lipid at the end of the storage period, and in feta cheese based on butteroil bleached at 280 °C the concentration was 10·4–13·1 µg/g lipid. In the reference feta cheese the concentration of 7-ketocholesterol was 1·2 /µg/g lipid. There was no difference in yellowness, measured by tristimulus colorimetry as the Hunter b characteristic, of the feta cheeses bleached at 265 and 280 °C, and a small scale bleaching experiment with butteroil showed that it was possible to secure complete bleaching at temperatures down to 220 °C. We suggest that bleaching of butteroil for feta production should be performed at temperatures as low as possible in order to prevent cholesterol oxidation.
322. Bacteriophage infection in cheese manufacture
Authors: Whitehead H. R. , Hunter G. J. E.
Published: June 2009

1. Previous work on bacteriophage infection of starters as a cause of slow acid development in cheese manufacture is reviewed. Air-borne phage seems to be the form of infection which is most insidious and most difficult to exclude. Hypotheses are developed to explain the sequence of events observed in commercial practice. The spread of phages as dust or droplet infections seems to explain the gradual increase of trouble with a given starter culture within a single factory and also throughout an entire dairying district.

2. When phage is established in the surroundings of a dairy factory a cycle of infection can develop. Besides the air-borne droplet infection there may be daily reinfection of cheese milk from incompletely sterilized factory and farm equipment which comes into contact with the milk. A description is given of methods which have been used to determine in any given case whether slow acid development is due to phage infection of the starter itself or to infection of the milk from factory or farm utensils.

3. The problem of preventing phage infection of the starter culture is fully discussed. The extent of the air-borne infection to be guarded against is indicated. The equipment which has so far been developed in New Zealand for the aseptic handling of starter cultures is described in detail. The most promising lines of development are indicated.
Evaluation of the direct epifluorescent filter technique for assessing the hygienic condition of milking equipment
Authors: Hunter Alastair C. , McCorquodale Rhona M.
Published: June 2009

The hygienic condition of 6 milking installations, 3 sanitized by circulation cleaning (CC) with chlorine-based chemicals and 3 by flushing with acidified boiling water (ABW), was tested using rinses of quarter strength Ringer's solution. The bacterial content of the rinses was determined using both colony counts and the direct epifluorescent filter technique (DEFT). A comparison of testing methods gave correlation coefficients between colony count and DEFT of 0·82 for plants using CC and 0·46 for plants using ABW.

Five strains of bacteria belonging to different genera and commonly found on milking equipment were exposed to various degrees of heat and to various concentrations of chlorine. The effects of such treatments on the staining characteristics of the organisms were studied. It was observed thatStaphylococcus aureusandStreptococcus lactis, although killed by heat treatment, stained a bright orange when treated with acridine orange dye.Pseudomonas fluorescens, Escherichia coliand vegetative cells ofBacillus cereusdid not take up the orange stain after heat treatment, nor did any of the 5 strains stain orange after treatment with NaOCl. It is suggested that the DEFT is a useful and rapid means of counting bacteria in rinses of equipment where sterilization is due primarily to chlorination, but in the absence of a stain which can differentiate more accurately between dead and living organisms its use is limited where sterilization is carried out solely by heat.
Kinetic studies ofin vivodigestion of bovine unheated skim-milk proteins in the rat stomach
Authors: Miranda Guy , Pelissier Jean-Pierre
Published: June 2009

Thein vivoaction of gastric proteinases on bovine milk proteins was studied in rats fed with skim-milk, by analysing gastric contents after 30, 60 and 240 min of digestion. Gastric proteolysis was already marked after 30 min of digestion and liberated a large number of peptides with different molecular weights. αs1-Casein and β-casein were still the main components of the stomach contents together with α-lactalbumin and β-lactoglobulin, which were little degraded, even after 240 min of digestion. A statistical analysis (multivariate method), made on several parameters (such as pH, N, and NPN) showed changes in the stomach contents during the digestion. The amino acid composition of the protein fraction was close to that of the diet, whilst that of the non-protein fraction was very different, being between the amino acid composition of the endogenous proteins and that of the diet.
Separation of the submicelles from micellar casein by high performance gel chromatography on a TSK-GEL G4000SW column
Authors: Ono Tomotada , Odagiri Satoshi , Takagi Toshio
Published: June 2009

Bovine caseins from skim-milk (micellar casein and acid precipitated casein) were separated into 4 discrete components by high performance gel chromatography on a TSK-GEL G4000SW columm. The resolution was better than that obtained by conventional gel chromatography which resulted in separation into 2 components at best. Our results showed that the second and third components consisted of αs1- and κ-caseins and αs1- and β-caseins respectively. They are presumed to be submicellar fractions. Samples prepared by removal of Ca phosphate from large and small micelles were rich in the third and the second components respectively. It is suggested that casein micelles consist of αs1- and κ-casein complexes and complexes and polymers of αs1- and β-casein which are situated preferentially on the periphery and in the interior of the micelles respectively.
Bacteriological sampling of glass, rubber and stainless steel pipe sections
Authors: Speers John G. S. , Lewis Stephanie J. , Gilmour Arthur
Published: June 2009

A practical effective method was devised for the removal of bacteria from soiled glass, rubber and stainless steel pipe sections which allowed the isolation of bacteria more loosely associated with the surfaces. This method, consisting of a pre-rinse followed by six successive double squeegee rinses, was compared with six other procedures (involving scraping followed by one or more successive swabbings) for the removal of bacteria from rubber pipe sections which had been inserted into an experimental milking plant. The squeegee method was found to be the most effective. It was also found that one particular part of these pipe sections was consistently more heavily contaminated.
Effect of refrigerated storage of milk on the manufacture and quality of Teleme cheese
Authors: Kalogridou-Vassiliadou Despina , Alichanidis Efstathios
Published: June 2009

Teleme cheese made from milk stored at 4–5 °C for 1–5 d and then pasteurized was compared with that made from unstored control milks. In the raw milks titratable acidity, tyrosine value and acid degree value increased more rapidly in stored milks than in the controls. With pasteurized milks, variations in coagulation times were attributable to levels of psychrotrophs in the corresponding raw milks. Differences were minor for milk fat and N content between cheeses. Curds made from milks stored > 4 d differed markedly from the controls in pH, moisture, N soluble at pH 4·6 and trichloroacetic acid (TCA)-soluble N, but only small differences in levels of casein fragments were detected. Proteolysis in mature cheese (60 d old) made from milk stored > 3 d differed significantly from the controls, and casein fragments were detectable. Off flavour related to excessive protein breakdown developed only in cheese made from milk stored > 4 d. In 60 d old cheeses there was significantly more rancidity in those made from milk stored for > 3 d than in those made from control milk. Unacceptable rancidity became evident at 60 d in cheeses produced from milk stored > 4 d. For Teleme cheesemaking psychrotrophic bacteria multiplying in the milk to levels likely to be encountered in commercial practice are of far greater importance for their lipolytic than for their proteolytic enzymes.
Effect of subclinical mastitis on milk plasminogen and plasmin compared with that on sodium, antitrypsin andN-acetyl-β-D-glucosaminidase
Authors: Schaar Johan , Funke Hans
Published: June 2009

The effect of subclinical mastitis on levels of plasminogen and plasmin in milk from cows in a high-yielding herd was investigated. Comparisons were made with levels of milk Na, antitrypsin andN-acetyl-β-D-glucosaminidase (NAGase). In samples from mastitic quarters plasminogen activity, as measured after activation to plasmin, increased by only 21% and plasmin by 82%, while NAGase increased by 307 %. Plasminogen was the only component that was normally distributed, all other components showed more or less skewed distributions. Plasmin and plasminogen were significantly related to the other components. However, plasminogen plateaued when the other components continued to increase. There was thus no further increase in plasminogen with the severity of inflammation as with the other components. Plasmin showed a similar although less pronounced tendency. Results of treatment of mastitic whey samples with acid suggested that the non-linear increase in plasmin activity was due to interaction with acid-labile proteinase inhibitors. Mastitis led to dissociation of plasminogen and plasmin from the casein micelles. The degree of activation of plasminogen was higher with casein-associated than with soluble plasminogen in both healthy and mastitic milks. Plasmin was very closely related to milk Na, which is a sensitive indicator of epithelial integrity. It is suggested that plasmin contributes to Na leakage into milk by degrading membrane proteins of the epithelial lining. Plasminogen and antitrypsin, which are both plasma proteins, were not identically affected by stage of lactation, indicating nonidentical modes of transport from plasma to milk.
Potassium iodate-induced proteolysis in ultra heat treated milk during storage: the role of β-lactoglobulin and plasmin
Authors: Grufferty Mary B. , Fox Patrick F.
Published: June 2009

The report that addition of KI03(0·1 mm) to milk before ultra high temperature (UHT) treatment induces extensive proteolysis during subsequent storage at 37 °C was confirmed. None was produced by addition of H202KMn04or K2Cr207. The pH optimum for KI03-induced proteolysis was between 7·0 and 8·0 and the temperature optimum 37—45 °C. β-Casein was particularly susceptible and the proteolysis pattern was similar to that caused by indigenous alkaline milk proteinase (MPA, plasmin). Addition of plasmin to milk before UHT treatment (140 °C/10 s) caused slight proteolysis during subsequent storage but addition of 0·1 mm-KI03and plasmin caused extensive proteolysis which was prevented by addition of soyabean trypsin inhibitor, indicating the probable involvement of plasmin in KI03-induced proteolysis in UHT-treated milk. Equally extensive proteolysis occurred in serum protein-free casein micelle systems (SPFCM), with or without KI03, during storage at 37 °C following UHT treatment, indicating a role for whey proteins in KI03-induced proteolysis. Addition of β-lactoglobulin (β-lg) to a SPFCM system inhibited proteolysis, but extensive proteolysis occurred in a SPFCM system containing both β-lg and KI03. MPA-free Na caseinate (prepared by heating at 140 °C for 7 min) underwent extensive proteolysis when treated with plasmin before UHT treatment; proteolysis was inhibited by addition of °-lg to this system and KI03reversed the inhibitory effect of β-lg. Plasmin proteolysis of isolated αs1-casein was inhibited by denatured β-lg (90 °C/30 min) at a level of 4 mg/ml but not by native β-lg. When denatured in the presence of KI03, β-lg had a lower free SH content than the control and was less inhibitory for plasmin in proteolysis of isolated αsl-casein. The results show that denatured β-lg inhibits plasmin proteolysis of caseins in UHT milk and that inhibition is prevented by KI03. This inhibition may occur via thiol–disulphide interchange, which is prevented if the SH group of ²-lg is oxidized by KI03, thus permitting the stimulatory effect of KI03on proteolysis in UHT-treated milk.
pH-Induced dissociation of bovine casein micelles. I. Analysis of liberated caseins
Authors: Dalgleish Douglas G. , Law Andrew J. R.
Published: June 2009

The dissociation of caseins of different types from casein micelles in milk, acidified to different pH values in the range 4·9–6·7, and at temperatures of 4, 20 and 30 °C, has been studied. In contrast to a number of previous findings, it was shown that caseins of all types were dissociated from the micelles, although in all cases β-casein was in highest concentration. The amounts and proportions of all of the caseins were found to be pH- and temperature-dependent, especially the former. Studies of the proportions of the different caseins liberated suggested that, at a defined temperature, the proportions of κ;- and αs2-caseins were independent of pH, while the proportions of β- and αsl-caseins were variable, changes in one being compensated by changes in the other. The manner in which the proportions of the αsl-casein and β-caseins changes with pH was found to be temperature-dependent.
Omitting the dry period between lactations does not reduce subsequent milk production in goats
Authors: Fowler Paul A. , Knight Christopher H. , Foster Margaret A.
Published: June 2009

Four goats were studied from the end of their second lactation. One mammary gland of each goat was dried off just prior to the start of the third gestation, whilst the other gland was milked throughout gestation, with no dry period. At the end of gestation the continuously milked gland was significantly smaller than the gland that had been allowed a dry period. However, this difference did not persist beyond parturition and there was no significant difference between the milk yields of the two glands in the next lactation, although the continuously milked gland tended to have the higher yield. At 18 weeks of lactation, mammary parenchyma weight and secretory cell number were significantly greater in the continuously milked gland, but mammary enzyme activities did not differ between the two glands.
Two Dicrocoeliid Trematodes from Ghana: Concinnum ghanensis n.sp. and Dicrocoelium hospes Looss, 1907
Authors: Fischthal Jacob H. , Thomas J. D.
Published: June 2009

Two dicrocoeliid trematodes are reported from Ghana. Concinnum ghanensis n.sp. is from the gall bladder and bile duct of the Senegal kingfisher, Halcyon senegalensis (L.), differing from the 14 species recognized in the genus in body shape, the caeca terminating at the vitellarian level or just previtellarian, and the vitellaria being in the form of a band of follicles extending across the body. Dicrocoelium hospes Looss, 1907, is from the bile duct of the Sudan sheep.
Serological evidence of toxocariasis in patients from Spain with a clinical suspicion of visceral larva migrans
Authors: Fenoy S. , Cuéllar C. , Guillén J.L.
Published: June 2009

Sera from patients with clinical characteristics of toxocariasis were assayed using the ELISA method and larval excretory-secretory antigen. Four hundred and seven samples ofToxocaraserology were received at the laboratory of ‘Ciudad Sanitaria Juan Canalejo’ Hospital of Corunna, Spain, from 1984 to 1989. Of these, 30 were from adults, 332 from children and 45 from patients of unknown age, resulting inToxocaraseroprevalences of 23.3%, 32.8% and 17.7% respectively. The reasons for these serological differences in the rural and urban areas of Galicia, Spain are discussed.
Thein vitroeffect ofKhawia sinensison leucocyte activity in carp (Cyprinus carpio)
Authors: Morley N.J. , Hoole D.
Published: June 2009

The interactions betweenKhawia sinensis(Cestoda: Caryophyllidea), a pathogenic tapeworm of carp, and host leucocytes has been investigatedin vitroby monitoring blastogenesis in pronephric, splenic and thymic lymphocytes and apoptosis of pronephric leucocytes. Both parasite homogenate and excretory/secretory (E/S) products were found to suppress lymphocyte blastogenesis at high concentrations (346.6–98.8 μg ml−1) whilstcell stimulation occurred at low concentrations (49.4–19.8 μg ml−1). This differential affect on leucocyte activity may not be associated with apoptosisin vitroas the parasite E/S products did not significantly affect programmed cell death as monitored by acridine orange and DNA analysis. The parasite effect on leucocyte activity is discussed and its relationship to host susceptibility is evaluated.