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This review addresses the importance of effective cleaning and sanitation programs in assuring food safety and dairy product quality. The processes of organic fouling and biofilm fouling have a major impact on cleaning efficiencies and methods and have a significant impact on operational efficiencies. The challenge for the dairy industry is to improve cleaning performance against biofilm matrices and achieve complete disinfection, extending the time for re-colonisation of new biofilms and increasing production run lengths. The fundamental requirements for effective cleaning remain constant and limitations cannot be compensated for through chemistry solutions. Traditional cleaning chemistries have improved only incrementally in the last 60 years, but very recent developments using oxidative precursor programs offer significant cleaning performance enhancement whilst addressing key sustainability performance indicators and operational gains. The use of latest generation biocides in association with these chemistries offers the prospect of genuine biofilm disinfection. Alternative methods for biofilm disruption including surface modification, phage disruption and temperature cycling offer future prospect although none are yet ready for commercial adoption.
The manufacture of butter from unneutralized factory-separated cream was investigated under commercial conditions. The experimental butters had serum pH values in the range 6.46 to 6.63. They had very good keeping quality and had the advantage over neutralized cream butters of a much brighter flavour. All the butters had copper contents of less than 0.05 ppm.
The fat losses in churning were significantly less when the cream was vacreated at the natural level of acidity of 0.08 to 0.09 per cent instead of at 0.03 per cent which is usual in neutralized cream. The fat losses increased by 0.32 per cent of the total fat when the acidity of the cream was reduced from 0.084 per cent to 0.032 per cent prior to vacreation in an Economic Vacreator 16*.
The results also showed that the fat losses in churning cream vacreated in an Economic Vacreator 16 were comparable with those associated with the Triple M Vacreator.
The onset of age gelation in ultra-high-temperature (UHT) sterilized milk was not directly related to the degree or extent of proteolysis in either the freshly prepared UHT milk or the gelled samples. In addition, the time of gelation (as defined by the product exceeding a viscosity of 10 mPa.s.) did not appear to be correlated with the microbiological quality of the raw milk. Age gelation did not occur in samples stored at 40°C or 50°C. Samples of UHT milk stored at ambient temperatures (20°, 25°C) gelled rapidly (typically 120-150 days), whereas the onset of age gelation was considerably retarded at low storage temperatures (2°C, 10°C). The order of resistance of UHT milk to the onset of age gelation at various temperatures was: 50°C, 40°C >2° > 10° > 15° > 20° > 25° >30°C. In general the rate of increase in proteolysis was storage-temperature dependent, except for samples stored at 40°C or 50°C. The initial rate of proteolysis in samples stored at 40°C was higher than any other. On further storage however, the extent of proteolysis in samples stored at 40°C did not increase appreciably. The level of proteolysis in samples stored over 200 days was highest in samples stored at 30°C. The rate and extent of proteolysis in samples stored at 50°C were low and comparable to levels observed in samples stored at 15°C. Gelled samples did not show a common level of proteolysis.
The effects of pH, pre-heat treatment, processing conditions and storage temperature on the period required for the onset of age gelation in Ultra-High-Temperature (UHT) milk were determined. Varying the pH of the raw milk in the range 6.6 to 7.2 did not affect gel time. Increased severity of the UHT process, either as a result of increased sterilization temperature or holding time resulted in increased gel time. Preheating raw milk also extended gel time, greater effects being obtained with increasing severity of the treatment. Incubation of the raw milk for 4 h at 30°C did not affect gel time. Gel times varied from more than 208 days at 2°C or 40°C storage temperature, to a minimum of 99 days at 25° and 30°C.
Authors: G.A. Mein, C.C. Thiel, Rosemary J. Fulford and J.B. Hoyle
Calculations based on measurements of the pressure and volume changes in the mouth-piece chambers of different liners indicated that small amounts of air normally leak past the teat during milking. Because these calculated values were necessarily regarded as minimum rates, direct measurements of the amount of air leaking past the teats of 8 cows milked with 4 makes of liners were made under conditions of both fast and slow rates of liner movement. The liners were assembled in separate, independent teatcup assemblies and also in conventional clusters. The overall mean rates of air leakage measured while the teatcups were stable on the cow were: 0.2 litre/min of free air per cluster during the period of peak milk flowrate; 0.8 1/min early in the period of reduced milk flowrate and 0.4 1/min at the end of this period. With each of the liners there were frequent measuring intervals during which no air leaked past the teat.
The measured air leakage rates were similar to the values calculated from pressure and volume changes in the mouthpiece chamber. This similarity implied that air normally leaked past the teat and mouthpiece lip, and then past the teat and barrel, during separate phases of a pulsation cycle. Records of mouthpiece chamber vacuum also supported this conclusion, indicating that air entered the chamber as the liner closed and passed down between the teat and barrel of the liner as it opened.
As a part of a study on the influence of alcohol on casein micelle stability, the L*, a* and b* values of skim milk/ethyl alcohol mixtures were determined at temperatures ranging from 20°C to 80°C. At 20° there was little effect of alcohol concentration in the range of 0% to 75% on the values of L*, a* and b* (note that the figures of alcohol content herein refer to the alcohol content of the water/alcohol mix which was mixed 1:1 by mass with milk to evaluate alcohol stability). Coagulation of the sample occurred at an alcohol level of 70% at 20°C. At and above 40°C, there was no evidence of coagulation at any of the alcohol contents examined (0 to 100% alcohol). Further, above 40°C, samples of higher alcohol content (above about 40%) became progressively less turbid as the alcohol content was increased. At higher temperatures (above about 60°C) and alcohol levels (above about 50%), the samples became almost clear and colourless - any remaining turbidity was presumed to be due to the presence of residual lipid. These changes in appearance were completely reversible. On cooling, samples became fully milky again and returned to their original L*, a* and b* values. These results suggest that the casein micelle undergoes a reversible temperature-induced alcohol-mediated dissociation under these conditions. There was little effect of temperature on the value of a* below about 30°C. Above this temperature a* increased. The extent of this increase was greatest for samples treated at the highest temperatures. Below about 50°C, there was little effect of temperature on b*. Above this temperature, b* increased, reaching a maximum at about 40% alcohol content, and then decreased to its original level. This alcohol-mediated temperature-induced reversible disassociation of the casein micelle has applications in enabling the ready modification to studies on micelle composition and properties. The procedure is simple and rapid, and does not alter the solids components of the milk. After dissociation, addition of modifiers (if desired) and reassociation, the alcohol may be removed by evaporation or membrane techniques, allowing examination of the modified reformed micelle in an aqueous medium of unchanged solids composition.
Authors: Patricia J.M. Reis, Freni K. Tavaria and F. Xavier Malcata
Serra da Estrela cheese was manufactured using a novel, customised apparatus – designed to meet that specialty cheese’s specifications, and the resulting product was compared with that obtained via traditional manufacture in the same dairy. Semi-industrial cheesemaking led to a significantly (p<0.05) higher fat content in the final cheeses, with favourable consequences in terms of flavour and consumer acceptability – and significantly (p<0.05) lower viable numbers of (unwanted) enterococci in the matured cheese. Textural characteristics were broadly similar. Proteolysis was significantly (p<0.05) faster, but it was more variable in artisanal than in semi-industrial cheeses. The latter received significantly (p<0.05) better scores for organoleptic texture, but lower scores for flavour. However, both products were within the specifications set forth by national regulations pertaining to Serra da Estrela PDO cheeses, so the novel apparatus is rather promising towards improved small-scale cheesemaking.
Authors: M.W. Hockey, H. Van Leeuwen, A.J. Hillier and G.R. Jago
Free amino acids accumulated more slowly in Cheddar cheese manufactured by a specific pilot-scale method from ultrafiltered milk than in cheese manufactured by the traditional method. The release of amino acids in both types of cheese was markedly increased by the inclusion of Lactobacillus helveticus with the normal starter. No difference was observed in the level of proteinase activity and TCA-soluble protein in the same cheese.
Cheese quality gradings recorded in Queensland from 1962 to 1965 are discussed. The most frequently used flavour description was "slightly bitter" but for cheese grading below first grade the dominant description was "fermented".
The use of the terms "very slightly weak" and "slightly weak" is increasing and in 1964/65 was applied to almost half of the cheese. Factors which might influence the grade of the cheese are discussed.
Colorectal cancer is a common form of cancer in both men and women. This review assesses the evidence that calcium and vitamin D protect against colorectal cancer. Although cellular and extracellular calcium levels may be important in carcinogenesis, it is the role of dietary calcium in colonic lumen physiology that has attracted the most attention. Dietary and diet-induced components such as long chain fatty acids and bile acids, which are present in the faecal stream, can be cytotoxic to colonic epithelial cells. Damaged cells are removed by apoptosis. Replacement of these cells causes an increase in the cellular proliferation rate that increases the risk of mutations in oncogenes and tumor suppressor genes, and thus subsequent colorectal cancer. The chemopreventive action of calcium results from the formation of non-toxic insoluble complexes with the cytotoxic lipids. Most animal studies show that dietary calcium can decrease the incidence of chemically induced or bile-acid-promoted cellular proliferation, preneoplastic lesions and colon tumors. However, conflicting results are common with human studies that explore the association between calcium intake and the risk of colorectal adenoma or carcinoma. Although the majority of the studies have demonstrated an inverse association, most did not attain statistical significance. Human intervention studies, where supplemental calcium was used to reduce colonic cell proliferation rate, have also produced conflicting results. This intervention appears to be effective when the initial proliferation rates are high but not when they are normal. There is also limited evidence that calcium supplementation can prevent the recurrence of adenomas in patients who had previously had adenomas resected. Vitamin D3 can likewise help prevent colorectal carcinoma in animals and humans. Moreover, of considerable significance are the studies that suggest vitamin D deficiency can attenuate the beneficial effect of calcium. In this review, reasons for the conflicting outcomes in the various studies are explored in terms of a range of individual, cultural and lifestyle factors. Recent evidence suggests that the effect of calcium on colorectal cancer risk differs according to the molecular nature of the mutated gene. Evaluation of specific types of mutations will need to be included in future studies.
Economic analysis showed that the main cost saving of the short method of Cheddar cheese manufacture was in capital outlay. Provision of extra starter was the main additional expense. Capital savings would be possible in a new factory or in existing plants replacing equipment or increasing capacity. In a specific case study in which plant capacity was to be increased, starter costs had relatively minor impact on profitability and reduction of equipment outlay through the use of the short method would be economically advantageous.