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Although there are reliable formulae for the calculation of the total solids in whole milk and skim milk from specific gravity data, no such formula is available for condensed whey. Ramsdell and Webb (1938) quote Sanders as suggesting for uncondensed whey the formula: Total Solids = 0.24 L plus 1.2 x per cent Fat, where L is the Quevenne lactometer reading. Bell & al. (1928) show the relation between specific gravity 29 to 32 degrees Baume and 55 to 66 per cent total solids in condensed fat-free whey. The following study was undertaken to provide data on the relationship between hydrometer-measured specific gravity and total solids in whey over the range from 6 to 30 per cent total solids for the convenient use of factories condensing or drying whey.
Authors: E. G. Pont and L. L. Muller and W. P. Rogers and R. BirtwhistleAn investigation was carried out under commercial conditions at two Victorian butter factories during the 190-61 and 1961-62 seasons to examine the effect of low cream acidity (below 0.08 per cent and in the pH range 6.8 to 8.0) on fat losses in churning. Bothe factories were equipped with Triple M Vacreators and only sweet factory-separated cream was used.
An investigation was carried out under commercial conditions at two Victorian butter factories during the 190-61 and 1961-62 seasons to examine the effect of low cream acidity (below 0.08 per cent and in the pH range 6.8 to 8.0) on fat losses in churning. Bothe factories were equipped with Triple M Vacreators and only sweet factory-separated cream was used.
With cream neutralized in the normal way before pasteurization, churning losses increased by an average of 0.07 per cent of the total fat for every decrease of 0.01 per cent in the titratable acidity of cream below its natural level around 0.08 per cent.
Neutralization of cream with caustic soda solution after pasteurization gave a similar trend to increased fat losses, but the effect was less pronounced than with the normal method. With post-pasteurization neutralization therefore a substantial saving could be demonstrated at low churning acidities, but its extent varied considerably between the two factories.
The amount of fat lost in churning showed a seasonal trend at both factories, the maximum losses occurring in the summer months.
The influence of somatic cell count (as a measure of mastitic infection) on the composition and quality of cheddar cheese and skim milk yoghurt was studied. The use of milk containing >500 00 cells/mL resulted in cheddar cheese with higher moisture content and proteolysis breakdown products, and lower flavour and body and texture grades. During the manufacturing process rennet coagulating times were increased by 25% and there were increased losses of fines, fat and protein in the whey associated with milk of >500 000 cells/mL. Losses of whey resulted in decreased cheese yields of approximately 8.9%. The data of one farm indicated that skim milk yoghurt manufactured from milk containing <250 000 cells/mL was organoleptically superior to that manufactured from milk of >250 000 cells/mL. However, the data from the second farm indicated that there was no significant relationship between milk log somatic cell count and organoleptic grade score of yoghurt.
Thirty-six bulk farm milk samples were analysed for somatic cell counts (SCC) and up to 23 constituents. Although significant correlations were obtained between log SCC and various milk constituents, it was concluded that SCC was not a reliable indicator of any compositional imbalance within farm bulk milk.
Authors: G.E. Mitchell, I.A. Frederick and S.A. Rogers
Thirty farm bulk milks, with somatic cell counts ranging from 70 x 103 to 2.1 x 106, were used in the manufacture of Cheddar cheeses. Cheese produced from milks with cell counts > 500 x 103 were significantly higher in moisture and lower in fat and cheese hardness than cheeses produced from milks with cell counts > 500 x 103. Rennet coagulation time was significantly longer and cheese yield was reduced for high cell count milks.
The influence of somatic cell counts (as a measure of mastitic infection) on the concentration of casein fractions and individual whey proteins were studied in two herds using combined milk from groups of 8 to 14 cows selected as healthy or suffering from subclinical mastitis. Log somatic cell count was positively correlated with the non-casein nitrogen (P<0.01), bovine serum albumin (P<0.01), x-casein (P<0.01), γ-casein (P<0.05), immunoglobulin G (P<0.05, one farm), immunoglobulin A (P<0.10) and total nitrogen (P<0.10, one farm) contents, and the non-casein nitrogen:total nitrogen ratio (P<0.01). Log somatic cell count was negatively correlated with the β-casein (P<0.01), α-lactalbumin (P<0.01, one farm) contents and the ration of total casein to total protein (P<0.01). When the SCC data were divided into four categories (< 250 000, 2500-499 999, 500 000-999 9999 and >1 000 000 cells/mL), analysis of variance showed significant differences in the following constitutents: non-casein nitrogen, β-casein, x-casein, γ- casein, α-lactalbumin, β-lactoglobulin and bovine serum albumin contents and the rations of total casein to total protein and non-casein nitrogen to total nitrogen. While SCC was found to be related to a number of protein fractions, these associations were not considered strong enough to enable the use of SCC to predict the milk protein changes associated with mastitic infection.
Authors: S.A. Rogers, G.E. Mitchell and J.P. Bartley
The influence of somatic cell counts (as a measure of mastitic infection) on milk composition was studied in two herds using combined milk from groups of 8 to 14 cows selected as healthy or suffering from sub clinical mastitis. Log SCC was positively correlated with the chloride and sodium contents, pH level and the ratios of chloride to lactose and sodium to potassium (P<0.01). Log SCC was negatively correlated with the lactose content (p<0.01) and for one farm with the solids non-fat, soluble calcium (P<0.01), total solids, total calcium and potassium contents (P<0.05). When the SCC data were divided into four categories (< 250 000, 250 000-499 999, 500 000-999 999 and > 1 000 000 cells/mL), analysis of variance showed significant changes in the following: lactose, chloride, sodium, pH, chloride to lactose ratio and sodium to potassium ration and for one herd solids-non-fat total calcium and potassium. While SCC was found to be related to a number of bulk milk constituents, these associations were not considered strong enough to enable the use of SCC to predict the bulk milk compositional changes associated with mastitic infection.
The influence of somatic cell count (as a measure of mastitic infection) on the composition and quality of pasteurised milk and high heat skim milk powder was studied. Pasteurised milk samples were organoleptically assessed after 1, 7 and 14 days storage at 4°C. The data from one farm indicated a negative relationship between log SCC and pasteurised milk grade at the three assessment times (P>0.05, P>0.05, P>0.01 respectively). However the data from a second farm indicated that there was no relationship between log SCC and pasteurised milk grade. When the SCC data were divided into categories of < 250 000, 250 000-499 999, 500 000-999 999 and > 1 000 000 cells/mL, statistical analysis indicated that after 14 days storage, pasteurised milk processed from milk in the <250 000 cells/mL category had a significantly higher (P>0.05) mean grade socre than those processed form milk containing > 500 000 cells/mL. In addition, milk processed from the 250 000-499 999 cells/mL category had significantly higher (P>0.05) mean grade score than those processed from the > 1 000 000 cells/mL category. Due to the conflicting nature of results obtained from the data of both farms, a strong relationship between somatic cell count and pasteurised milk organoleptic assessment grade could not be conclusively demonstrated. Milk collected from one farm was used in the skim milk powder study. Results indicated that as the SCC of the milk increased the resultant skim milk powders had a lower titratable acidity (P>0.01) and higher ferricyanide reducing value (P>0.05). Solubility index and heat stability was not influenced by somatic cell count. The effects of elevated milk SCC on skim milk powder flavour after storage at 18°C for one year were minimal.
Analysis of the relationship between the somatic cell counts and lactation yields of 19,849 cows over the period 1979/81 indicated that, under Victorian conditions, a doubling of the geometric mean cell count of individual cows was associated with a loss of 80 litres of milk or 4 kilograms of butterfat per cow per lactation. A separate study in 1982/83 of the production difference between cows that were classified as infected or free from subclinical mastitis showed a butterfat production loss of 5 to 8 kilograms per infected cow per lactation was associated with a 3 to 4 fold increase in the geometric cell count.
In strongly pasture-based production systems, such as those present in the majority of Australian dairy production regions, considerable variation is possible in the consumption of milk. This is due to a range of factors at the farm level, such as the stage of lactation of the cow, nutrition and genetic variation. This review examines the literature regarding the effects of the composition of milk on the processability of milk into typical bulk milk manufactured products, such as powdered milk, UHT milk and key products made from recombined milk powders such as recombined evaporated milk and recombined sweetened condensed milk. As heat treatment is a key processing step for most manufacturing of this type, an emphasis is placed on the effects on milk composition on heat stability.
The softening point and refractive index were determined on milkfat from 112 samples of butter collected from eastern Australian states during the period August 1967, to April 1970. The survey included monthly sampling from the Maleny butter factory in Queensland. Softening points ranged from 31.65°C to 35.07°C and the refractive index from 1.45368 to 1.45534. Results for the Maleny factory showed that minimum values for softening point occurred from August to December with maximum values appearing in the period May to July. Maximum refractive index values were found in winter butter, minimum values in the summer.
Statistical analyses showed a lack of correlation between refractive index and softening point. Using previously determined fatty acid composition for the butters studied, a highly significant positive correlation was found between refractive index and oleic acid content. There was a lack of correlation between oleic acid content and softening point. Correlation co-efficients between individual fatty acids and softening point together with multiple correlation co-efficients for various combinations of fatty acids are presented.
The oxidative stability of butterfat was examined by the Swift or active oxygen method. The range of Swift times from 43 samples of choicest Victorian butter was 12 to 24Â¼ hours. The addition of 0.01 per cent dodecyl gallate or nordihydroguiairetic acid to butterfat markedly prolonged Swift times but gave comparatively small increases in keeping quality at room temperature. The Swift values were not influenced by the grade or age (up to 6 months) of butter and within the range 12 to 22Â½ hours they were not correlated with the keeping quality of butterfat or of shortbread biscuits containing butterfat.
Many attempts have been made in the past to obtain a relationship between the lactose and chloride content of cow's milk, the main purpose being (1) to differentiate between abnormality and adulteration, and (2) to utilise one figure as a basis for calculating the other. The relationships developed are summarised by Davies (1939) and Davis (1950). In the investigation here reported the formulae proposed by Kopatschek, Mathieu and Ferré Sunderland and Davies to correlate lactose and chloride contents were applied to 142 normal bulk milks received at Sydney, NSW.
Official grading of Cheddar cheeses manufactured in a pilot plant from milk which had undergone various degrees of lipolysis showed an inverse relationship between level of lipolysis and flavour score, with a marked drop in flavour score for cheeses with acid degree values (ADV) > c. 3.0. The flavour defect, attributable to the increased amounts of free fatty acids, resembled the 'butyric' flavour responsible for downgrading of some local cheese. Evidence is presented to show that activation of the milk lipase system is unlikely to be the sole cause of such flavour defects in commercial cheese. The role of bacterial lipases in the production of rancidity in Cheddar cheese is discussed.
Authors: W. C. T. Major, D. A. Cummings and L. E. Nichols
Methods are described for removing weed taints due to Coronopus, Lepidium and Rapistrum species during the conversion of butter to butteroil. Laboratory trials showed that taint is not removed when desludged butter receives single treatments with electrolytes, is water-washed and re-centrifuged. However, taint is removed by electrolytically-assisted double refining and phosphoric acid in the second. Alternative electrolytes and simplified processing are now being investigated.