149392799X by Unknown

Author:Unknown [Unknown]
Language: eng
Format: epub
Published: 2015-10-29T12:21:38+00:00

Similar observations were found for cow’s authors’ experience with pilot plant and labora-

milk (Chen, 2013 ). In a comparison study, 25 tory experiments on cow’s milk and goat’s milk

batches of cow’s milk showed good heat stability

suggests that reducing ionic calcium is benefi cial

when subjected to UHT treatment and in- in terms of reducing fouling of heat exchangers

container sterilisation. The average sediment and sediment formation (Boumpa

et al. , 2008 ;

level was 0.19 % for UHT treatment (range 0.1–

Prakash et al. , 2007 ). Also, reducing ionic cal-

0.29 %) and 0.24 % for in-container sterilisation cium was found to increase ethanol stability and

(range 0.02–0.56 %). Adding 10 mM DSHP or good correlations have been found between etha-

TSC increased sediment much more for in- nol stability and Ca

2+

. Therefore, in situations

container sterilisation than for UHT treatment. where sediment formation or fouling is a prob-

Thus, trends were similar to those found for lem, the following suggestions were offered by

goat’s milk, although sediment levels were lower

Lewis and Deeth ( 2009 ). The pH, ethanol stability

in the control cow’s milk. Adding only 2 mM and ionic calcium should be routinely monitored

calcium chloride increased sediment signifi -

in raw milk to establish their effects on sediment

cantly for UHT treatment but not for in-container

and fouling-

related problems. Over time, this

sterilisation. Such differences have only recently should provide data to assess, understand and

been reported. However, although variations eventually reduce problems arising from poor

were found in amounts of sediment, the overall heat stability. Chavez et al., ( 2004 ) grouped bulk

heat stability of these milk samples was consis-

milk samples into those having alcohol stability

tently high and none of them produced sediment values above and below 72 %. Over 30 % of bulk

levels that would be detectable to consumers. It milk samples had ethanol stabilities less than

is not clear why there are these differences and 72 %; these had Ca 2+ values between 1.84 and

why relatively small reductions in ionic calcium 2.59 mM and pH values in the narrow range of

make milk more susceptible to sediment forma-

6.67–6.69. Those showing ethanol stability

tion during in-container sterilisation compared greater than 72 % had Ca 2+ from 1.66 to 2.04 mM

to UHT treatment. Some of these fi ndings for in-

and pH from 6.70 to 6.72. The mean heat coagula-

container sterilisation are in agreement with tion times were 23.8 and 19.9 min for samples

HCT–pH relationships for Type A milk samples with ethanol stabilities above and below 72 %,

in that narrow pH range between their minimum respectively.

and maximum values.

There are two main reasons why milk may

There is a strong argument for avoiding using have a low ethanol stability (<74 %). The fi rst is

milk for commercial processes which shows poor poor microbial quality which is accompanied by

heat stability, but for the reasons discussed, avoid-

a fall in pH and the second is a salt imbalance

10 Protein Stability in Sterilised Milk and Milk Products

255

(Horne, 2003 ). The former situation is likely to this could also be improved by further heat

arise with milk of poor hygienic quality or stored treatment of the concentrate prior to sterilisation.

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