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The use of "paper thermometers" for the determination of the temperature of hot water used for the sanitizing of milking machines is described and the results of a field survey involving some 59 farms are given.
A total of 1893 strains of Micrococcaceae isolated from raw milk, mastitic udders and down-graded dairy products were used in a study to assess the performance of the thermo-stable nuclease (TSN) rapid Staphylococcus aureus identification method. All 139 S. aureus isolates were found to be TSN producers. Of the other species examined ten were isolates of S. epidermidis type 1, two of which produced TSN. The other 34 isolates of S. epidermidis types 2 and 4 and of Micrococcus were all TSN negative. In comparison seven of 59 S. aureus strains isolated from raw milk and tested for coagulase production were coagulase negative. The TSN test is a useful method for the rapid identification of S. aureus either for confirming negative coagulase results or in place of the coagulase test itself.
Authors: David C. Thorn, Heath Ecroyd and John A. Carver
Molecular chaperones are a diverse group of proteins that stabilise partially folded target proteins to prevent their misfolding, aggregation and potential precipitation under conditions of cellular stress, e.g. elevated temperature. Protein aggregation, particularly the formation of highly ordered protein aggregates termed amyloid fibrils, is of considerable research interest because of its intimate association with a wide range of debilitating diseases, including Alzheimer's, Parkinson's and Huntington's diseases and type II diabetes. In this review, we discuss the ability of the milk casein proteins to act in a chaperone-like manner. This property is of biological importance since at least two of the casein proteins, αS2- and κ-casein, have a propensity to assemble into amyloid fibrils under physiological conditions. The fibril-forming propensity of α S2- and κ-casein, the possibility of its occurrence in mammary tissue, and the ability of the other casein proteins, α S1- and β-casein, to inhibit the aggregation of α S2- and κ-casein and other proteins, are discussed. The results have application in the use of casein proteins in a systematic manner to stabilise other proteins at high temperature and under shear conditions, as occurs in the industrial treatment of milk and milk-based products.
The possible use of the stable free radical 2, 2'-diphenyl-1-picrylhydrazyl (DPPH) for measuring antioxidant properties of butterfat was investigated. There was a lack of correlation between the extent of reduction of DPPH and either tocopherol content or stability of the fat. As DPPH also reacts with hydroperoxides it is not considered a suitable reagent for measuring the antioxidant properties of butterfat. As it reacts with most commercial antioxidants it may be used to detect their presence in a fat provided the history of the fat is known.
The hard milkfat fraction obtained by fractional crystallisation was used successfully to replace part of the milkfat in processed Cheddar cheese, in which the young cheese was partly replaced by a low fat cheese. Up to 40 per cent of the cheese blend was substituted by this fraction so that approximately 15 per cent of the total fat in the cheese was a hard milkfat fraction. There was no significant difference in taste test evaluation, pH, oil separation and accelerated storage test results between the control and the different levels of substitution in the cheese blend.
It has already been shown (Dawson and Feaghan, 1960) that intramammary penicillin preparations dyed with Brilliant Blue F.C.F. can be successfully used in the lactating cow. Penicillin preparations are sometimes used to treat the udder of a cow when it is dried off. A experiment was therefore conducted to determine whether dyed penicillin preparations cause any damage to udder tissue under these conditions. It was considered that if damage occurred it would be reflected by lower milk yields in the following lactation. Milk yields were therefore used to measure any possible udder damage resulting from such treatment.
It was found that dihydeostreptomycin intramammary preparations could be satisfactorily dyed with Brilliant Blue F.C.F. When dyed at a rate of 0.125 g dye per 100,000 μg of dihydeostreptomycin, the dye and antibiotic concentrations excreted at each milking were closely related and disappeared from the milk at the same time. The dye did not affect the stability of the antibiotic.
Investigations were carried out to find a suitable dye to use in intramammary penicillin preparations. Fluorescein dyes were investigated and found unsuitable. A food dye Brilliant Blue F.C.F was found to have suitable properties and was used in subsequent experiments. This dye could be detected at .25 p.p.m. in milk. Various ointment bases were examined. Preparations can be satisfactorily dyed using 0.125 g. of Brilliant Blue F.C.F per 100,000 I.U. of penicillin in a paraffin base. The dye and penicillin concentrations excreted at each milking were closely related and disappeared from the milk at the same time. The use of water-repellent bases caused extended excretion of dyed milk. The penicillin in dyed preparations lost no potency on extended storage. The dye did not cause any irritation in the udder.
Oxytetracycline HCl intramammary preparations in a water miscible base could be satisfactorily dyed with Brilliant Blue F.C.F. When dyed at the rate of 0.25 gm dye per 426 mg oxytetracycline HCl, the dye and the antibiotic disappeared from the milk of treated cows at the same rate. Exclusion of dyed milk excluded 99.9% of the antibiotic. The dye did not affect the stability of the antibiotic.
Growth of cultures in skim milk and factory buttermilk has been compared. Cultures produced more acid in skim milk than in buttermilk but reached the same final pH in the two media. Dilution of cream in factory processing caused this loss of buffering capacity of buttermilk. Acid production in undiluted buttermilk from undiluted cream was similar to that in skim milk
Diacetyl production in undiluted buttermilk was greater than that in skim milk, but in factory buttermilk it was approximately the same as in skim milk.
Butter was made on a laboratory scale from cream inoculated with skim milk and buttermilk cultures. The use of buttermilk for culture growth did not cause any off-flavours in the butter. Slightly less diacytal was produced in cream by the buttermilk cultures than by the skim milk cultures. Buttermilk sterilised in the factory showed considerable browning, but this did not affect the flavour of butter made from cream inoculated with buttermilk culture.
Authors: M.C. Broome, N. Willman, H. Roginski and M.W. Hickey
Stirred skim milk yoghurt was manufactured from fortified skim milk in which cheese whey protein concentrate, in liquid form, replaced up to 30% (w/w) of the fortified skim milk. At replacement levels up to 25% there was no statistically significant taste or textual difference between control and experimental yoghurts. Also, laboratory studies showed that growth and acid production rates of both Streptococcus thermophilus and Lactobacillushelveticus were stimulated by the presence of cheese whey protein concentrate. The same situation did not occur in factory trials.
The effectiveness of chlorine teat dips, at concentrations of available chlorine of 1.5 and 5.0% was assessed over eight and twelve-week periods respectively. Both concentrations effectively reduced the bacterial level in milk from dipped quarters relative to that from un-dipped quarters. The cell count levels were also reduced relatively, although this reduction was retarded by a temporary irritative effect of the chlorine dip. It was concluded that these chlorine formulations are effective teat dips but may cause epidermal irritation of transient papilloma around the teat orifice.
The enzymatic processing of milk products employing lactase (beta-galactosidase) to obtain a reduced lactose content was studied. Three types of microbial lactases were compared, and a fungal lactase which was active at a pasteurization temperature for milk was selected. Fungal lactase was effective in hydrolyzing lactose in skim milk, whole milk as well as concentrated milk, despite some product inhibition, and was utilized for the preparation of a low-lactose skim milk powder. The final product with reduced lactose content has a sweeter taste than the original milk and offers several advantages.