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The weight lost during curing by Cryovac-packaged 7 lb. loaves of Cheddar cheese was found to be very much less than that by similar cheese when waxed. No evidence of rind formation or rind flavour was found after curing for up to 6 months. Some cheese in all trials developed mould growth within 4 weeks of packaging. However, much of this moulding was only very slight, and cheese free from mould after this time usually remained so for the remaining 12 to 20 weeks of curing. An environment very conducive to mould growth did not influence the occurrence of moulding in packaged cheese initially free from it. Packaged cheese proved resistant to infestation by cheese mites for 4 months under conditions which caused waxed cheese to become seriously infested in 3 months. No difference was found between the rate and type of flavour development of packaged cheese and that of similar waxed cheese but packaged cheese tended to have the slightly weaker body after curing. No detrimental effects results from a complete lack of turning of 5 lb, 7 lb. and 10 lb loaves of packaged Cheddar cheese for several months except for a slight spreading of the largest-size cheese. A necessity to safeguard packaged cheese against contact with sharp objects was revealed. When packaged cheese was held for short periods at high temperatures some free fat appeared underneath the packaging film. A subsequent return to cold room temperatures caused the cheese to recover its appearance well, but when the package was opened the surface of the cheese was found to be greasy. The distension of some Cryovac packages of Cheddar cheese by an excessive rate of gas production was observed. The manufacture of cheese by methods designed to restrict the rate of evolution of gas by the maturing cheese to a level at which it can diffuse through the packaging film, is considered necessary.
Authors: Golda L. Munro, L.F. Bailey and J.T. Feagan
Monthly protein testing data from commercial dairy farms and weekly data from a Research Centre herd were examined. A significant drop in protein percentage occurred from the first to the second month of lactation followed by a gradual rise to the end of lactation. The significance of this observation in relation to the protein content of herd milks and its effect on the requirements of an individual cow protein testing service are discussed.
The aqueous phase of butter (i.e. butter serum) contained on the average 30 mg of protein and 45 mg of lipid per mL. Approximately 15% of the lipid material was phospholipid, consisting mainly of phosphatidyl choline, posphatidyl serine and sphingomyelin. The remainder of the lipid was largely triglyceride but there were low levels of mono- and diglycerides, cholesterol and free fatty acids. The fatty acid compositions of the phospholipids and triglycerides were considerably different from that of milk fat itself. The major proteins of butter serum were α- and β-casein, with β-casein being the most predominant. Smaller amounts of κ casein, β-lactoglubulin and α-lactalbumin were also present. Other high molecular weight poly-peptides were identified as originating from milk fat globule membrane (MFGM) material and it is suggested that these MFGM polypeptides are mainly responsible for the binding of the large amount of lipid material found in the butter serum.
The incidence during the 1960 season of an ester-like flavour defect in cheese from a number of Queensland factories and the failure of most factories to obtain choicest grade for their cheese led to a comprehensive investigation of bacterial quality of milk supplies. Platform tests applied included methylene blue, fermentation, Wisconsin curd, sediment and acid-inhibitory tests, and laboratory tests used were counts of thermoduric bacteria, plate counts, and disc assay for antibiotics. The results of these tests, numbering over 60,000, are outlined. Comparison with earlier surveys showed that methylene blue tests had improved, with a closely corresponding improvement in general cheese quality. There were weaknesses in sediment, tests, fermentation tests and thermoduric counts, but it was considered that a high proportion of the milk now supplied to cheese factories should be convertible to cheese of sound commercial quality.
It has long been appreciated that to attain and maintain the highest standard of efficiency in the Butter Industry a technical control service in the chemical composition and bacteriological quality of the product is essential. This paper outlines the results obtained and methods used by the Butter Improvement Service over a 9 year period from 1940 to 1949.
The Butter Improvement Service gives a technical quality control service to the Queensland butter industry. This service gives regular detailed chemical, physical and microbiological examinations of butters and advice on quality improvements. Results are given of nearly 30 years of testing. Changes in testing methods and standards, as well as additions to the service, are detailed.
Authors: W.D. Jarrett, G.E. Mitchell and J.R. Dulley
The Food Research and Technology Branch has maintained an interlaboratory testing program with Queensland dairy factories since May, 1982. The program currently offers comparisons on eleven different chemical and microbiological analyses and involves 25 separate laboratories. The system provides an effective means of monitoring the standard of testing carried out by dairy laboratories.
A photometric method for the determination of fat in young Cheddar cheese using the Milko-Tester is described. Either sodium tripolyphosphate or the tetrasodium salt of ethylene-diamine-tetra-acetic acid (EDTA) may be used to disperse the cheese to form an emulsion suitable for presentation to the Milko-Tester. The result obtained with the tripolyphosphate method must be multiplied by a factor of 0.981 to give a corrected estimate of the fat content. The EDTA method of preparation does not require a correction factor. Both methods were compared with the British Standard method BS 770. The mean fat content of twenty-two cheese samples analysed by the tripolyphosphate-Milko-Tester method was 31.69%, and 31.62% by the British Standard method. The standard deviation of differences between paired means was 0.627% fat in the cheese. Twenty samples were analysed by the EDTA-Milko-Tester method and the British Standard method. The means of these analyses were 32.44% fat and 32.34% fat for the British Standard and the Milko-Tester methods respectively. The standard deviation of differences between the paired means was 0.315% fat in the cheese. The EDTA method therefore has the advantages that the result does not require correction and is considerably more accurate.
The determination of the salt content of unripened Cheddar cheese using a liquid ion exchange electrode which is specific for chloride ions is described. The preparation of the sample is simple and the sample is not destroyed during the analysis, thus making it available for further analyses. The method was compared to the IDF (1961) standard method and was shown to be accurate. The error means squares after 22 analyses are 0.00076% NaCl for the IDF and 0.00128% NaCl for the electrode method. The correlation coefficient between the two methods was 0.9636. The standard error of the proposed method was 0.075% NaCl. The method is recommended for use where large numbers of samples are to be analysed.
A technique is described for the rapid estimation of fat in low-fat rennet casein in semi-capillary Plane Precision butyrometers. Treatment and digestion of the sample follow the modified Gerber method for fat in casein previously published in this journal (1). The results obtained in Plane Precision butyrometers agree within 0.1 per cent. with those of the British Standard gravimetric method.
A fluorescence method, taking twenty minutes to complete, has been tested and modified for milk containing 3 000-300 000 bacteria /mL. The method involves pre-treatment of the milk with Trypsin and Triton X-100 to lyse somatic cells, disperse fat globules and degrade protein sufficiently to permit filtration through a bacteria retaining membrane. The retained bacteria are then strained with the fluorescent dye, acridine orange, and the orange-yellow fluorescing bacteria counted by means of an epifluorescence microscope. When compared in a trial against 114 samples of know Standard Plate Count the technique showed excellent agreement (r = 0.94).
The purpose of these investigations was to determine whether the phosphatise test of Aschaffenburg & Mullen could be used under Australian conditions as an alternative to the present Kay & Graham test. The results obtained showed good correlation between the two tests. As the readings are made at 1Â½ to 2 hours, it should now be practicable to check all pasteurised milk prior to distribution. The test is as simple as a Methylene Blue Test to perform, and there is no problem of phenolic contamination.
The prosperity of the milk trade will, in the long run, depend quite largely on the satisfaction of the consumer with the quality of the milk he is receiving. His degree of satisfaction will influence the amount of money he will spend on milk relative to other foods, his response to appeals for greater consumption, and his reaction to such changes as block delivery. A comprehensive and confidential questioning of milk consumers, using methods similar to those adopted by the Gallop Poll, provides the only means of finding out just what consumers think of milk quality. Their attitude will be influenced by many psychological factors as well as by the actual quality of the milk. Information of the type most obviously useful to the milk trade cannot always be elicited from the consumer directly or easily. The trade will wish to know such things as: (1) whether most people are satisfied with their milk; (2) whether they are sufficiently interested in milk as a drink to notice at once any flavour defect; (3) whether they are perhaps put off milk without being consciously aware of off-flavours; (4) why some drink milk and others do not; (5) the relative importance of price and flavour-quality to the consumer, and (6) their ideas as to the source of off-flavours. The questionnaire was designed to give as much information as possible on such points, but only an indirect approach was possible on some aspects.
The extent of precipitation of the proteins in Cheddar cheese whey as insoluble complexes with carboxymethyl cellulose (CMC) depended on the degree of substitution (DOS) of the CMC and on the pH and ionic strength of they system. The pH for optimum precipitation of the complex was 3.2 to 3.4. At the ionic strength of Cheddar cheese whey (approximately 0.15), more than 85% of the protein content was precipitated by use of CMC of DOS 0.8. This compared with earlier findings that CMC of similar DOS precipitated only 54% of the protein from undiluted hydrochloric casein whey.