bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tallowy discoloration and trace metals in cheddar cheese
Authors: Bishop F. 
Published: June 2009

SummaryThe characteristics are given of a Chaddar cheese defect known as ‘tallowy discoloration’ or ‘white streak’. In the tallowy portions of the cheese the copper content is lower and the iron content higher than in the adjacent normal cheese. The copper probably migrates in cheese following oxidation of the sulphydryl compounds in the tallowy area while the unexpected distribution of iron may be explained by changes that occur during salting of the curd. The proportion of ferrous to ferric iron tends to increase as the cheese matures and tallowy portions of cheese do not contain less ferrous iron than adjacent portions.The addition of iron salts to cheese milk did not increase the incidence of tallowy discoloration, but the addition of sufficient copper salts reduced it. Although the sulphydryl content of cheese appeared to be related to tallowy discoloration, little evidence of the part it plays was obtained. The oxidation of sulphydryl groups and the formation of peroxides occurred more readily at lower temperatures.The significance is discussed of ferrous iron in a fat-oxidizing system where copper does not increase oxidation.
Physical properties of milk fat: II. Some factors influencing crystallization
Authors: de Man J. M. 
Published: June 2009

SummaryThe crystal habit of milk fat is determined by the cooling procedure employed and is changed markedly by interesterification (randomization) of the fat. X-ray diffraction analysis indicated that slowly cooled milk fat occurs in both beta prime and beta modifications, whereas in rapidly cooled milk fat, evidence for the beta prime modification only was obtained. The long spacing was greatly increased by interesterification, especially when the fat was slowly cooled. The presence or absence of certain high melting glyceride fractions greatly influenced solid fat content, softening point and hardness of milk fat.
Fat oxidation in Cheddar cheese
Authors: Riddet W. , Whitehead H. R. , Robertson P. S. , Harkness W. L. 
Published: June 2009

SummaryFat and carotene oxidation in Cheddar cheese may give rise to bleached areas surrounding slits in the cheese and to a tallowy flavour. It was shown that direct contact of the fat with atmospheric oxygen was essential for oxidation to occur, and examination of cheeses showed that slits running from the rind into the interior provided this contact. Factors enhancing slit formation such as gas production by bacteria and mechanical shock to the cheese were shown to increase the incidence of tallowy discoloration. Factors which tended to exclude oxygen such as waxing the cheese surface, wrapping the cheese in plastic film or sealing in a tin were shown to reduce the incidence of the fault or eliminate it.Accelerating factors were shown to be low cheese storage temperature, excess moisture in the cheese and possibly low salt content. Various factors which may be relevant to a commercial cure for discoloration are also discussed.
A comparison of the influence of Streptococcus lactis and Str. cremoris starters on the flavour of Cheddar cheese
Authors: Perry K. D. 
Published: June 2009

SummaryComparable cheeses were made using single strains of Streptococcus cremoris and Str. lactis as starters. The three Str. lactis strains imparted a characteristic rather abnormal flavour to the cheese, whereas the three strains of Str. cremoris all gave cheeses of normal flavour. The abnormal flavour caused by the lactis cultures increased in intensity as ripening proceeded, and differed slightly from strain to strain.Bacteriophage usually developed slightly in the whey and in the curd during the manufacturing process, but never to such a degree as to delay acid production unduly. The extent of phage development did not have a significant influence on cheese flavour.All the lactis strains survived in much larger numbers in the cheese than the cremoris strains. The simplest explanation of the data is that the ‘lactis’ flavour was a direct effect, due to flavour substances produced by the Str. lactis cells present in the young cheese.
Enhancement of the flavour of Cheddar cheese by adding a strain of micrococcus to the milk
Authors: Robertson P. S. , Perry K. D. 
Published: June 2009

SummaryThree strains of micrococci and two of pediococci were individually tested for effect on Cheddar cheese flavour by their addition to cheese milk. Only one of the micrococcal strains had a significant effect on flavour. In twenty-eight of the thirty-three trials with this strain the flavour of the experimental cheeses was appreciably better than that of the corresponding control cheeses; in the other five trials the experimental and control cheeses were similar in flavour.This micrococcus did not grow appreciably during manufacture or ripening of the cheese, the peak number being present in the curd at the time of pressing. The count fell to less than 30% of the peak number after 1 week, and to less than 0·5% after 5 weeks.The ways in which the micrococcus may have influenced the flavour of the cheese are discussed and attention is drawn to the possibility that bacterial action in the milk and the young cheese may play an important part in flavour development.
The effect on the performance of growing pigs of the level of meal fed in conjunction with an unrestricted supply of whey
Authors: Mitchell K. G. , Sedgwick P. H. 
Published: June 2009

SummaryResults are reported of an experiment made under commercial conditions on the effect of the level of meal fed in conjunction with an unrestricted supply of whey on the performance and carcass quality of pigs.All the pigs received the same meal mixture and had continuous access to an unrestricted supply of whey. The four treatments were: (1) 3 lb meal per pig per day reduced to 2 lb at 13 weeks of age; (2) 3 lb meal per pig per day throughout; (3) 2½ lb meal per pig per day throughout; and (4) as (1) but the daily allowance of meal increased to 2½ lb/pig at 20 weeks of age. There were five pens of nine group-fed pigs on each treatment, involving a total of 180 pigs. The pigs were on experiment from 8–9 weeks of age to bacon weight. Comprehensive carcass measurements were made on all the pigs.Mean differences in rate of growth, efficiency of food utilization and carcass quality between the four groups of pigs were small and were not statistically significant. The significant differences in the proportions of meal and of whey consumed by the pigs on the different treatments during the growing period are discussed in relation to relative prices of the two foods. It is concluded that where unrestricted whey feeding is to be used, the feeding system employed in treatment 3 could be recommended in most of the environmental and economic situations likely to be encountered in practice.The superior performance of the pigs in the experiment compared with that in earlier trials is discussed in relation to the stock improvement work and concurrent improvements in housing and management carried out during the intervening years on the Cow and Gate farm in Dorset where the experiments were conducted.
The incidence of bacteria in cheese milk and Cheddar cheese and their association with flavour
Authors: Franklin J. G. , Sharpe M. Elisabeth 
Published: June 2009

SummaryThe numbers and types of non-starter lactic acid bacteria, lipolytic bacteria and group D streptococci in cheese milks and corresponding Cheddar cheeses have been studied and their relationship to cheese flavour discussed. Different milks, heat-treatments and starters were used, and their association with flavour investigated. The pH and fat, salt and moisture contents of the cheeses were also determined.The non-starter lactic acid flora consisted mainly of Lactobacillus casei, L. plantarum, L. brevis, L. buchnerii, Pediococcus spp. and Leuconostoc spp. Lactobacillus casei was nearly always present in the milks and cheeses, predominating in most of the cheeses, particularly in those made from milk which received the most severe of the three heat-treatments tested (160°F for 17 sec). Leuconostocs were not found in any of the cheeses. Other species sometimes occurred in approximately equal numbers to L. casei, particularly in cheeses manufactured from the milder heattreated milks. Cheeses made from milk receiving the highest heat-treatment contained fewest bacteria and scored lowest for flavour. The average flavour scores increased as the number of species contributing to the non-starter lactic acid flora at the time of tasting increased.The lipolytic organisms capable of hydrolysing butterfat consisted mainly of Gram-positive cocci, predominantly Staphylococcus saprophyticus. The group D streptococci occurred infrequently, Streptococcus faecium being the most commonly occurring species.A definite correlation was found to exist between the starters used and the flavour of the cheeses. The pH of the cheeses was associated with the flavour, but the fat, moisture and salt contents of the cheeses showed no definite effect.
Hydrogen sulphide in Cheddar cheese; its estimation and possible contribution to flavour
Authors: Lawrence R. C. 
Published: June 2009

SummaryA modified entrainment method is described for the estimation of microquantities of hydrogen sulphide in cheese. Optimum recovery is only possible if the conditions are very acid, if oxygen is excluded and if appreciable loss by diffusion is avoided by minimizing the surface area of the sample and the time it is exposed to the atmosphere. The reproducibility of determinations from the same cheese was satisfactory.The concentration of H2S in New Zealand Cheddar cheese curd at hooping was less than 20 μg/100 g but increased after ripening for 1–4 months to an average concentration of 55 μg, thereafter remaining fairly constant. There appeared to be no simple relationship between characteristic Cheddar flavour and H2S concentration.
Destruction ofBacillus subtilisspores with solutions of sodium hydroxide
Authors: Whitehouse R. L. , Clegg L. F. L. 
Published: June 2009

SummaryThe rate of destruction ofBacillus subtilisspores by sodium hydroxide solutions in the range of atmospheric temperatures 34—82 °F was studied: (a) to provide information which might be used in practice for immersion cleaning of dairy utensils in sodium hydroxide solutions at low atmospheric temperatures, and (b) to examine the nature of the disinfection curves by slowing down the rate of disinfection. The results expressed as a three-dimensional graph showed that an increase in temperature from 34 to 82 °F had a more marked effect on spore destruction than an increase in concentration of sodium hydroxide from 1·5 to 5·0%. The overall effect could be expressed aswheret= time in hours for the 99% destruction ofB. subtilisspores,C= concentration of NaOH (%, w/v) and θ = temperature, °F. Since the time for the 99% destruction ofB. subtilisspores by a 2% NaOH solution at 34 °F is 5 times that of a 5% solution, immersion cleaning in cold climates might be assisted by increasing the concentration of NaOH from the normal 2–3 to 5%. Results in disinfection tests at low temperatures were more variable than had been observed in previous work at higher temperatures. These surprising results prevented a careful study of the nature of the disinfection curves and confirmed previous conclusions that such curves are basically sigmoid.
The effect of concentrates on the rate of disappearance of digesta from the alimentary tract of cows given hay
Authors: Campling R. C. 
Published: June 2009

SummaryTwo experiments were conducted with non-lactating cows to examine the effect of adding concentrates to a diet of hay on the rate of disappearance of digesta from the alimentary tract. The addition of large amounts of concentrates to the diet of cows offered hay ad lib. decreased the voluntary intake of hay, increased slightly the digestibility of the organic matter and decreased markedly the digestibility of the crude fibre of the diet. Also, the addition of concentrates increased the mean time of retention of stained hay residues in the alimentary tract and increased the time/kg hay the cows spent ruminating. At the end of a meal the amount of digesta in the reticulo-rumen of the cows offered hay ad lib. with restricted amounts of concentrates was about the same as that found when offered hay ad lib. as the only food. The results are discussed in relation to the regulation of the voluntary intake of hay by the cow.
The stability of milk protein to heat: III. Objective measurement of heat stability of milk
Authors: White J. C. D. , Davies D. T. 
Published: June 2009

SummaryAn objective test has been developed to help in assessing the value, as a method for determining the heat stability of milk, of the subjective test described by Davies & White (1966a). The objective test showed that coagulation time, as determined by the subjective test, is a reasonably accurate measure of the induction period that precedes the onset of initial rapid coagulation, but that coagulation proceeds in 2 different ways depending primarily on whether the coagulation of the milk is good (initial clots large) or poor (initial clots small). The latter finding confirms the view that in studying heat stability these 2 categories of milk should be examined separately.
Pediococci in Cheddar cheese
Authors: Fryer T. F. , Sharpe M. Elisabeth 
Published: June 2009

SummaryFifty-nine strains of pediococci were isolated as representing the predominant non-starter flora in a series of Cheddar cheeses made over a period of 5 months. All strains had the same physiological characteristics and were identified asPediococcus cerevisiae. A common antigen was found in 54 of the strains, whereas in the other 5 the antigenic component appeared to be related but not the same. Both antigens were located in the cell wall.All the strains required folinic acid for growth and it was shown with one strain that the small amount of growth which occurred in sterile milk was greatly increased by the presence of the folinic acid producing starterStreptococcus cremoris924.
Factors affecting the design of milk total solids testing schemes
Authors: O'Keeffe M. G. 
Published: June 2009

SummaryAn analysis of variance was applied to the ‘within herd’ variance of milk total solids in order to find the contribution due to sampling, testing and biological variances on a balanced 8 × 8 two factor (herds and days) experiment with replicate sampling and testing. Testing samples from every consignment from 10 herds over a 12-month period showed that the mean monthy ‘within herd’ variance was 0·039 and the yearly ‘within herd’ variance was 0·085. A formula is given showing how the variance of the mean for compositional quality testing can be obtained and on which the design of testing schemes can be based.
Thermorésistance des spores declostridium tyrobutyricumetClostridium butyricum
Authors: Cerf O. , Bergere J.-L. , Hermier J. 
Published: June 2009

SummaryClean spores suspensions of 3 strains ofClostridium tyrobutyricumwere prepared after culture in dialysis sacs. The survivor curves of the spores heated at 90 °C in 0·033 M phosphate buffer (pH 7·0) or in skim-milk were logarithmic. From the thermal-death-time curves the following values were calculated:Dat 121 °C = 0·003−0·012 min andz= 8·4−10 °C when spores were heated in phosphate buffer;Dat 121 °C = 0·006−0·008 andz= 9·5−9·9 °C when spores were heated in milk.When clean spores of 2 strains ofClostridium butyricumwere heated at 85 °C in 0·005 M phosphate buffer (pH 7·0) the survivor curves were logarithmic, but ‘tails’ were observed after heating in skim-milk. The value ofDat 85 °C was lower than that obtained with spores ofC. tyrobutyricum.
The influence of the dissolved oxygen in milk on the stability of some vitamins towards heating and during subsequent exposure to sunlight
Authors: Ford J. E. 
Published: June 2009

SummaryHeat sterilization of milk destroyed about 50% of its folic acid activity, and subsequent exposure of the milk to sunlight caused a progressive further loss. This loss of folate, as of vitamin B12, was a consequence of the oxidative destruction of the milk's ascorbic acid, and was largely prevented by thorough exclusion of oxygen from the milk during heat processing and subsequent storage. With thiamine, riboflavin, nicotinic acid, vitamin B6and biotin, stability towards heating and during exposure to sunlight was affected little, if at all, by the oxygen tension in the milk.
The influence of the milk ejection reflex on the flow rate during the milking of ewes
Authors: Labussière J. , Martinet J. , Denamur R. 
Published: June 2009

SummaryIn order to obtain more information on the importance of the milk ejection reflex in the lactation of normal ewes, experiments were conducted to determine whether the neuroendocrine reflex is able to modify the parameters which characterize the flow rate of the milk under normal milking conditions.Ewes were allowed to suckle their lambs freely during the 3 days following parturition. They were then milked with a machine and the individual milk production was measured volumetrically at each milking. Different fractions obtained during milking (‘machine milk’, ‘machine strippings’ and ‘hand strippings’), and the milk flow, were measured using a sensitive recording system. In further experiments, machine milking was performed after intravenous administration of oxytocin, during general anaesthesia, and after unilateral or bilateral denervation of the mammary gland.The ewes fell into 2 categories: those giving most of their milk in 1 rapid emission, and those giving it in 2 quite separate emissions. The results indicated that the second emission found in some of the ewes was the milk emptied from the acini by the neuroendocrine ejection reflex. Disappearance of the second emission resulted from the administration of oxytocin before milking—which induces passage of the milk from the acini into the mammary cistern—and also from general anaesthesia or denervation of the mammary gland.
The flavour of milk protein
Authors: Ramshaw E. H. , Dunstone E. A. 
Published: June 2009

SummaryThe flavour stability of casein and co-precipitated milk proteins has been examined organoleptically. Differences in flavour stability were correlated with processing conditions and the early stages of the non-enzymic browning reaction were implicated in the off-flavour development. The ‘gluey’ flavour present in stored casein could be removed and the flavour stability improved by treatment with activated carbon or Sephadex. However, a better solution to the problem was to avoid the development of off-flavour by careful choice of conditions of preparation, drying and storage to minimize heat damage and browning. Conditions were established under which milk protein could be expected to have flavour stability during at least 6 months storage at ambient conditions.
Volatile compounds associated with the off-flavour in stored casein
Authors: Ramshaw E. H. , Dunstone E. A. 
Published: June 2009

SummaryCompounds associated with the ‘gluey’ off-flavour in stored casein have been isolated and identified by a combination of gas chromatography and mass spectrometry. Most of the flavour was found in the non-acid steam-volatile fraction which contained many compounds including n-alkanals, n-alkan-2-ones, furfural and other furan derivatives, benzaldehyde, dimethyl disulphide and benzthiazole. No single compound had the typical gluey flavour, which must be a complex sensation in which the quantities of minor components may determine the specific gluey character. o-Aminoacetophenone was present in the casein in subthreshold amounts. This compound has some gluey flavour and may have a synergistic effect in enhancing the total flavour.
A fractionation of the αs-casein complex of bovine milk
Authors: Annan W. D. , Manson W. 
Published: June 2009

SummaryThe nature of the αs-casein complex of bovine milk has been investigated by cation-exchange chromatography on columns of sulphoethyl Sephadex C-50 of purified preparations of αs-casein and of whole acid-precipitated casein. Three main fractions were separated from each. Two behaved as single homogeneous proteins as judged by starch-gel electrophoresis; they were the main constituent of the complex, αs1-casein, and a closely related phosphoprotein, designated αs0-casein, which was present in small amounts only. The third fraction also constituted only a small part of the total complex. It was heterogeneous on starch gel electrophoresis and contained 2 major and 2 minor components. This fraction, while similar to other members of the αs-casein complex and to β-caseins hitherto described in that it contained phosphorus, nevertheless differed significantly from these since 3 at least of its components contained sulphur either in the form of disulphide bonds or of sulphydryl groupings.Information is presented on the composition of the 3 fractions including C-terminal end group analysis.
The rennet hysteresis of heated milk
Authors: Morrissey P. A. 
Published: June 2009

SummaryThe phenomenon of rennet hysteresis in heated milk is essentially due to reversible heat-induced changes of calcium phosphate equilibrium which affect the second or calcium ion stage of the rennet coagulation. The phenomenon is shown not only by heated milk but also by all heated caseinate systems provided they contain sufficient calcium to permit of coagulation with rennet and enough phosphate to ensure some degree of colloidal phosphate precipitation during the heating process; its occurrence does not require the presence of micellar casein or of β-lactoglobulin, or the initial presence of colloidal phosphate. Nevertheless, rennet hysteresis is greatly increased in these heated systems if β-lactoglobulin is present owing to the formation of a calcium caseinate/β-lactoglobulin complex which in its renneted condition is much less sensitive to calcium ions than is calcium para-caseinate. The resulting relative prolongation of the second stage of the rennet coagulation renders this phenomenon more apparent by increasing the proportion of the total time occupied by the hysteresis effect.
Synthetic peptide and ester substrates for rennin
Authors: Hill R. D. 
Published: June 2009

SummaryRennin hydrolysed the phe-met bond in the peptide H-ser-leu-phe-met-ala-OMe (i.e. methyl ester), the amino acid sequence of which is similar to that around the phe-met bond attacked by rennin in κ-casein. Rennin did not attack other peptides from this sequence not containing serine, and it is suggested that, in both κ-casein and the pentapeptide, the enzymic attack is accelerated by the nearby serine side chain. Rennin also hydrolysed sulphite esters such as phenyl sulphite ester and some N-substituted imidazole compounds such as benzoyl imidazole. Phenyl sulphite esters may be suitable substrate for assaying the activity of preparations of rennin.