Pakistan is among the largest milk producing countries. The requirement of milk is
increasing day by day. It has rapidly increasing demand and competition in national and
international markets. Milk consumers in Pakistan often face low-quality, lack of hygiene and
absence of cold chains as primary contributors to this low quality. Milk and dairy products also
become contaminated during manufacturing and packaging processes. The consumption of low
quality milk may cause milk borne diseases. Not only the bacteria but the presence of their
enzymes also can cause deterioration of the milk quality. The heat stable enzymes can cause the
spoilage of commercial UHT products without presence of any viable count. Aflatoxin (M1) is
metabolite of AFB1 in milk. It causes chronic diseases and immunosuppression in children. It is
found carcinogenic and cytotoxic in nature.
In this project microbial load, free amino acid estimation to predict any protease activity
and Aflatoxin M1 were studied in both UHT and Raw milk samples (n=15) procured from local
markets of Lahore. Three UHT brands A, B and C were purchased. The UHT milk was studied
for microbial growth and protease activity at purchase and at expiry of the products. The
microbial load was evaluated by testing of milk for Total viable count, Coliforms, Yeast and
Molds, Anaerobic Clostridia and Bacillus cereus in both raw and UHT milk. Protease activity
was estimated by assessing the free amino acid by using ninhydrin assay while the Aflatoxin M1
was detected through High performance liquid chromatography.
SUMMARY
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CONCLUSION:
It was found that the locally available raw milk quality was poor for consumption and dairy
processing for safe and stable milk products. UHT milk quality was found better with low
microbial load. Protease activity with reference to free amino acid was detected in raw milk
which is indication of the poor milk storage conditions, cold chain maintenance and
unavailability of fresh milk. Protease activity was also found in UHT milk and an increase in free
amino acid which could be due to heat stable proteases active during shelf life of the milk
brands. Aflatoxin M1 was found in majority of raw milk sample which showed the poor animal
feed storage and monitoring system. Aflatoxin M1 was also found in some samples of UHT
brands with high concentration which depicted that AFM1 was heat stable and it retained in the
commercial UHT products as well.