I'roc. Roy. Sor. Vktoima, 25 (N.S.), I'r. II., \U\:V. 



Akt. XXiV. — T/ie Viscosity ofCred'm. 

 By FRANCP:s K. M DUMAliESQ, M.A., li.8c. 



^ l*liysiolui;i(.Ml L;ilK»i"it<>ry, University of MellKHirne). 



[\ien<l lu'tli D.'ceiiilxn-, 1912 1. 



It seems to lie roiiiiiioiily suppdNi'd that the tliiekiiess or viscosity 

 -of ri'L'iun aft'oids a fair tost of its lielmess in fat; investigation, 

 Jiowever, discloses a number of factors which affect the viscosity to 

 a greater or less extent. Amongst these there are three to which 

 a ninre prominent intluenic u|M)n viscosity must be attributed — 

 viz., acidity, fat content and temperature; hut liesides these there 

 jire several minor factois. which exercise an undeniable influence 

 upon the viscosity, and wliose relative important-e is difticult to 

 -estimate. l'"<>i- instance, such factors as mechanical agitation, 

 growth of organisms, exposure to higher or lower tem])eratures 

 for a considei'able period (all of which may be included uiidei- the 

 term " pi-evious history of the cream "), certainly have their effect 

 uijon the viscosity, but tliese can hardly be independently investi- 

 gated, and hence tlieir individual contril)ution to the general effect 

 •cannot readily l>e calculated. Again, the size of the fat globule 

 may be of impoitance, or, since each globule may be encased in a 

 layer of protidn. the number of fat globules in a given volume of 

 cream of known fat content may liave an appreciable effect in 

 -determining the viscosity. 



The nature of tiie ])idtein niay vary, as regard its physical (;on- 

 •dition, ill creams fi'om different sources, hut it would be difficult 

 to obtain an experimental evaluation of the viscosity effect (d' tliis 

 factor, owing to tiie impossil>ility of ascertaining whether the 

 various samples of cream iindei- observation were directly com])ar- 

 able in other respects. 



Hence in the following jiajK-r the vaiiations in viscosity due 

 to acidity, fat content ami temperature changes are alone taken 

 into consideration. 



.]<■/(// fi/ of Grrnm (is Afffcttng Viscositj/ {Critical Acidity). — This 

 is assuredly the most potent of the factors generally recognised as 

 influencing viscosity. A fresh cream, of fat content as great as 

 40 jier cent., will be com])aratively li(piid, and on this account 

 •ordinary commercial pasteurised cream .seldom ajipears sufficiently 

 rich to the average purcha.ser. 



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