Microbiological quality and shelf-life of raw cow`s milk preserved by lactoperoxidase system
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Date
1998
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Department of Dairy Science, College of Veterinary and Animal Sciences, Mannuthy
Abstract
A detailed study was carried out to determine the micro-biological
quality and shelf- life of raw cow's milk preserved by lactoperoxidase (LP)
system. Literature related to the LP-system have been reviewed .
••
A total of 6 trails were conducted to obtain reliable data for
statistical analysis. In each trail, three litres of raw cow milk was divided into
three equal parts of one litre each. One part was kept as a control (C) and
LP-system was activated in the other two parts one part with 20: 10ppm (Tl)
and other with 20:20ppm (T2) (SCN-:H202), with in two hours of production of
milk. The milk samples were stored at 30 +1 DC .
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Before the activation of LP- system the micro-biological quality of
raw milk, samples were analysed. After the activation of LP-system the
micro-biological quality of control and experimental group milk samples were
analysed once in every 3 hours, till the samples showed positive on
clot-on-boiling (COB) test.
Standard plate count, Coliform count, Titratahle acidity, pH,
Methylene blue reduction time, one hour Resazurin reduction test,
Clot-on boiling test and Alizarin - Alcohol test were the parameters studied.
The mean initial SPC of milk samples was 5.280 log cfu per ml.
The control milk samples remained 'Good' quality only for 3 hours storage,
while the LP-treated milk samples of both Tl and T2 remained 'Good' quality
even after 9 hours of storage.
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The standard plate count and coliform count (CC) of control milk
samples showed a steady increase from the initial period itself, whereas in the
LP-treated milk samples of T1 and T2 the SPC and CC showed a reduction
than the initial count after 3 hours of storage and both SPC and CC slightly
exceeded the initial count even after 6 hour of storage .
..
Based on the titratable acidity, the control milk had the
acceptable quality (0.18 per cent lactic acid) of only upto 6 hours while the
LP-treated milk remained with in the acceptable limit for 12 h.
According to the Alizarin - Alcohol test, the control milk remained
stable only for 3 hours and the LP- treated milk remained stable for 9 hours of
storage at 30+ 1 DC. The milk samples of control group had the shelf-life of
12 hours where as the LP-treated milk samples of T1 and T2 had the shelf-life
of 18 hours based on the clot-on-boiling test.
The micro-biological quality and shelf-life of milk samples, both T1
and T2 did not show significant difference during the entire period of storage.
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Citation
171383