Trichloromethane (TCM) is a residue in milk caused by the interaction of chlorine (from cleaning detergent) and milk. TCM in milk must be at levels less than 0.0015mg/kg. Maintaining low milk TCM levels on the farm is achieved in most instances by practising correct milking equipment cleaning procedures. Adequate rinsing of the plant with at least 14 litres per unit is the key to minimising residue levels in milk leaving the farm gate. Other key cleaning procedures that will influence the TCM level in milk are:Farm survey
Trichloromethane (TCM) is a residue in milk caused by the interaction of chlorine (from cleaning detergent) and milk. TCM in milk must be at levels less than 0.0015mg/kg. Maintaining low milk TCM levels on the farm is achieved in most instances by practising correct milking equipment cleaning procedures. Adequate rinsing of the plant with at least 14 litres per unit is the key to minimising residue levels in milk leaving the farm gate. Other key cleaning procedures that will influence the TCM level in milk are:
Using high chlorine cleaning products.Using higher than required detergent levels.Reusing the detergent cleaning solution.Using chlorine in a pre-milking rinse.Dipping clusters in chlorine.Farm survey
A recent survey of milking equipment (milking machine and bulk tank) cleaning procedures was undertaken by milk quality advisers in conjunction with Ornua and Teagasc. This survey was conducted on 112 farms which were previously identified as having milk containing unsatisfactory TCM residue levels.
The high TCM farms chosen were geographically spread across Ireland, with those farms supplying milk to five different milk processors. The parlour type and unit size of these parlours was representative of typical farms in Ireland, with 67% having pipeline plants, 11% with pipelines plus milk meters attached and 22% having glass jars.
Twenty-nine percent of these herds had six milking units or less, a further 61% had between seven and 15 units and 10% of herds had greater than 15 milking units. Sixty-one percent of farms had their own well water supply, 18% of farms were part of a local group scheme and a further 13% were linked to a county council water supply.
While there may be infrequent instances of high TCM milk being linked to the addition of higher than normal chlorine to group scheme wells, the majority of farms on this study had their own well water supply.
The main faults associated with high milk TCM levels on these farms are outlined in Table 1. There were 14 different incorrect cleaning procedures identified on the farms visited, with the number of faults per farm ranging from one to seven.
Rinsing of milk and detergent from machine/bulk tank surfaces
Adequate rinsing of both milk and detergent residues at equipment cleaning time is critical to minimise TCM residues in milk. At least 14 litres or three gallons of clean water per milking unit is necessary to remove milk and detergent residues. The volume of the water trough (for storage of water for the cleaning process) was inadequate on 55% of farms and this is a key factor accounting for the insufficient water used for rinsing on 65% of farms. Currently, in many instances of parlour expansion, the water trough storage volume has not been increased in line with the extra milking units.Inadequate rinsing of the bulk milk tank was also identified as an issue on 30% of farms. Correction of bulk tank rinse levels is achieved by increasing the bulk tank rinse cycles or implementing an additional manual rinse when the wash cycle is complete.Strength and level of detergent/steriliser products used
Overuse of detergent for both machine (18%) and bulk milk tank (26%) cleaning was identified as a further problem leading to TCM residues. Furthermore, this results in increased cost of cleaning. This is generally due to lack of measurement utensils and not following product guidance.Only products containing less than 3.5% chlorine concentration should be used for equipment cleaning; using products with higher levels will lead to residues, especially where rinse water volumes are low. There is a tendency to use these higher-chlorine concentrated products for bulk tank cleaning (16% of farms on survey), as it is considered that these products are less likely to crystalise in the pipes supplying the detergent for cleaning. However, these products will increase the likelihood of residues.Unregistered products are not legally approved to be sold in Ireland and the chemical content of these products is not known in some instances. Five percent of farms in this study were using unregistered products. Check the Teagasc link for registered products, chemical content of products and washing routines – www.agresearch.teagasc.ie/moorepark/cleaningguides/cleaning.aspWashing a milking machine
Adding additional chlorine to the detergent/steriliser solution is not necessary as there is adequate chlorine concentration in all detergent/steriliser products to clean the equipment. This practise will increase the likelihood of residues and will increase the daily cost of cleaning the equipment.Detergent steriliser products contain chlorine and this is identified as sodium hypochlorite on drum labels. When this product is used for cleaning milking equipment, it should be rinsed from the plant with clean water as soon as the wash cycle (eight to 10 minutes) is complete. Leaving this solution (containing chlorine) in the plant until the next milking will cause rubber tubing to deteriorate more quickly and will also likely lead to residues in milk. Twenty-five percent of farms with high milk TCM in this survey were incorrectly leaving this solution in the plant.Read more from our Liquid Milk supplement here.
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