LPT 311: Milk and Milk Products Technology (1+1)

TOXIC /PESTICIDE RESIDUES IN MILK

Milk is pooled from different sources and hence Mycotoxins (Aflatoxin M1), heavy metals, pesticides residues and veterinary residues due to several environmental reasons.

Mycotoxins(Aflatoxin M1)

• Mycotoxins are metabolites of moulds like Aspergillus flavus and Aspergillus parasiticus are carcinogenic and can be present in grains,nuts,cotton seed and other commodities associated with human food and animal feeds.Animals are exposed to aflatoxins by consumption of feeds that are contaminated by aflatoxin producing fungal stains.Aflatoxin M1(AFM1) and it is quite stable towards normal milk processing methods such as pasteurization and if present in raw milk it may persist into final products for human consumption.Quantitative estimation of Aflatoxin M1is done by HPLC method.

Heavy metals

The feed of polluted ares when regularly given to milch animals there is chance of contamination of heavy metals in milk.The contamination of arsenic,cadmium,mercury,lead in milk is reported and they cause the following diseases.

• Arsenic:Affects pulmonary,nervous system and skin.
• Mercury-Mercury and ethyl mercury are toxic.Mercury stores in kidney and liver has affinity for sulphahydryl groups.
• Cadmium causes kidney damage.
• Lead affects renal,gastrointestinal and nervous system.Lead inhibits Hb synthesis and leads to anaemia.It also affects nervous system leading to encephalomalacia. Organochlorine and Organophosphate pesticide residues from contaminated sources enters milk causing ill effects. eg. HCH isomers(Hexachlorocyclohexane) is a commercial insecticide, endosulfan, malathion, chlorpyrifos, and methyl-parathion

Codex Guidelines for the establishment of a regulatory programme for control of Veterinary drug residues in foods (CAC GL16-1993) provides useful guidelines on selection of methods of analysis for veterinary drugs.

Various antibiotics like Ampicillin, Benzylpenicillin, Bacitracin, Cloxacillin, Kanamycin, Tetracycline in milk can be detected by various microbial inhibition assays.

DELVO MICROBIAL INHIBITION ASSAY IS USED FOR DETECTION of antibiotics and sulphonamides in milk.The higher concentration of cleaning agents and disinfectants in milk may give false positive results.The preservatives used to conserve milk for later analysis usually make the milk unsuitable for testing.