Milk separation and pasteurisation : the impact of separating temperature, and order of separation and pasteurisation, on the composition of skim milk, cream and separator sludge : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology of Massey University, Palmerston North, New Zealand
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Date
2014
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Massey University
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Abstract
A principal purpose of the present study was to determine whether the order in which
separation and pasteurisation of whole milk occurs has an effect on the composition of
skim milk and cream, and thus potentially of products made using these streams. The
study also sought to determine the effect of separating temperature on the composition
and microbiological quality of skim milk and cream.
In addition, a survey of whole milks and separator sludges at four Fonterra
manufacturing sites across New Zealand was carried out to determine whether there
was regional variation in minerals content. This related to the suspected involvement of
sludge minerals content in the incidence of desludging port erosion found in some
separators, particularly in Northland.
Trials to study the effects of order of separation and pasteurisation, and of separating
temperature, were first carried out in an ideal environment in the pilot plant at what is
now Fonterra Research and Development Centre. Commercial-scale trials of the
same kind were then carried out at Fonterra Kauri. The minerals survey was
conducted by collecting and analysing whole milk and separator sludge samples
collected at Fonterra Kauri, Fonterra Whareroa, Fonterra Clandeboye and Fonterra
Edendale. This study has identified that dairy manufacturing plants have a larger operating
window in terms of separating temperature and equipment configuration than
previously thought. The ANOVA analysis may have found significant effects, but the
compositional changes were minor.
The mineral survey work showed that there were significant batch differences for all
minerals. The calcium and phosphate contents explained most of the variability in the
composition. The milk at the Kauri plant was different to milk in other parts of the
country. Calcium content could be used to differentiate between the different sites
tested. The phosphate content could be used to distinguish between separators.
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Keywords
Milk pasteurisation, Milk, Skim milk, Cream, Separation, Research Subject Categories::TECHNOLOGY::Chemical engineering::Food technology