Single Factory Research Articles

Factors affecting the concentration of vitamins in milk: I. Effect of breed, season and geographical location on fat-soluble vitamins

SummaryTwo surveys were done, one in 1943–44 and one in 1958–60, of the seasonal variation in the concentration of vitamin A and carotene in milk fat from 13 different areas in Great Britain. In the 1958–60 survey α-tocopherol and vitamin D were also measured. The main purpose of the second survey was to find out if the marked swing from Shorthorns to Friesians, and the trend towards greater use of carotene-rich foods in winter feeds that occurred in the intervening 15 years, had affected the pattern of vitamin A activity. In addition, monthly samples of butter were obtained in 1958–59 from a single factory in New Zealand during a complete butter-making season (9 months) and were assayed for vitamin A, carotene, α-tocopherol and vitamin D. Three experiments were done to study the effect of breed on the vitamin A and carotene content of milk fat, and in one of them α-tocopherol and vitamin D were also determined.The seasonal trends for vitamin A and carotene were essentially the same in both surveys. A peak occurred in May after the spring flush of grass and was followed by a decline with a second peak in the autumn, except in 1959 when both the summer and autumn were very dry. Potencies were higher in the south than in the north, where the differences between summer and winter were more marked. In winter, mean vitamin A potencies of 5·8 and 7·7 μg/g fat were found for northern and southern areas, respectively; the corresponding values for β-carotene were 2·0 and 4·5 μg/g fat. Mean summer values were 8·8 and 9·7 μg/g fat for vitamin A and 5·1 and 6·5 μg/g fat for carotene, equivalent to increases of about 52 and 26% and about 155 and 44%, respectively, over winter values. Differences in mean potency between areas are explained by length of grazing season and type of winter feed.The concentration of vitamin A in the fat was essentially the same for Ayrshires, Friesians, Jerseys and Shorthorns but somewhat lower for Guernseys; that of carotene was higher for the Channel Island breeds, particularly Guernseys, than for the other breeds studied.Compared with this country, concentrations of carotene were higher and of vitamin A lower in milk fat from New Zealand, probably because of the predominance of Jersey cows in New Zealand herds. The seasonal trends for these vitamins were similar in both countries, but the spring peaks were earlier, the autumn peaks later and the summer declines more pronounced in New Zealand than in this country.Concentrations of α-tocopherol in British milk fat showed a trend similar to that found for both vitamin A and carotene and were again influenced by feeding practices. Mean values of 23 and 29 μg α-tocopherol/g fat were found in the summer for northern and southern areas, respectively; the corresponding winter values were 15 and 23 μg/g fat. Mean values of about 30 μg/g fat were found, over a 28-month period, for the milk fat of each of the 3 breeds, Ayrshire, Friesian and Jersey. No seasonal trend was observed in the New Zealand samples; the mean value for the 9 months was 32 μg/g fat (range 24–39 μg).Vitamin D potencies were higher in summer, when there is more sunshine, than in winter. The higher summer values in the northern than in the southern part of the country may have been related to a higher intake of vitamin D in the former from hay and pasture. Summer potencies of 0·44, 0·53 and 0·62 i.u. vitamin D/g fat, respectively, were found for Friesian, Jersey and Ayrshire milk; corresponding winter values were 0·06, 0·08 and 0·9 i.u./g fat. For the New Zealand butters, summerues values were higher than in this country, about 0·7 compared with about 0·4 i.u./g fat; winter values were similar in both countries.

THERMAL STRESS IN A SINGLE STOREY FACTORY

Abstract Environmental conditions in a single storey factory were investigated as a result of staff complaints in summer when the external temperature rose to 74 deg. F. The Bedford corrected effective temperature scale was used to assess the thermal conditions, from measurements of air temperature, heat radiation, humidity and air movement in ten different parts of the factory. For the greater part of the day, the conditions were found to lie outside the Beford Confort Zone for light work. Measurements of energy expenditure were made in two areas of the factory, i.e. where the worst environmental conditions were found, and where the greatest physical work was involved, to determine whether all the work in the factory was in the light work category of the B.M.A. classification of work. The Wolff IMP respirometer was used to make direct measurements of energy expenditure. In one area, an indirect estimate of energy output was also made by the method of activity sampling, to compare with the direct measurem...

322. Bacteriophage infection in cheese manufacture

1. Previous work on bacteriophage infection of starters as a cause of slow acid development in cheese manufacture is reviewed. Air-borne phage seems to be the form of infection which is most insidious and most difficult to exclude. Hypotheses are developed to explain the sequence of events observed in commercial practice. The spread of phages as dust or droplet infections seems to explain the gradual increase of trouble with a given starter culture within a single factory and also throughout an entire dairying district.2. When phage is established in the surroundings of a dairy factory a cycle of infection can develop. Besides the air-borne droplet infection there may be daily reinfection of cheese milk from incompletely sterilized factory and farm equipment which comes into contact with the milk. A description is given of methods which have been used to determine in any given case whether slow acid development is due to phage infection of the starter itself or to infection of the milk from factory or farm utensils.3. The problem of preventing phage infection of the starter culture is fully discussed. The extent of the air-borne infection to be guarded against is indicated. The equipment which has so far been developed in New Zealand for the aseptic handling of starter cultures is described in detail. The most promising lines of development are indicated.