Whey Below the Surface: Grading Milk’s Appearance
Along with temperature and odor, the milk hauler’s evaluation of a tank’s appearance is among the most important assessments they can make to determine the quality of a herd’s production. Though it may seem superficial, the way milk looks can tell us a lot about problems that may be lurking behind the scenes of its production. But in order for milk haulers to assure quality, they have to know what to look for before loading milk onto their truck.
How Do They Inspect The Milk?
Normally, milk is odorless and ranges in colour from bluish white to golden yellow. To inspect the tank, milk haulers turn on the tank inspection light and open up the tank to a sufficient amount of external light. They lift the lid and inspect the surface of the milk in the tank, which should be quiescent – not moving.
What Issues Raise Red Flags?
- Blood: A small amount of blood can color a whole tank with a slightly reddish tint, and is a sign that one or more animals may have mastitis – an udder infection (the most common disease in dairy cattle in the U.S.), and will need to veterinary treatment.
- Flakes: Flakes or curd particles may be caused by mastitis, milk souring or destabilized protein. Further investigation can determine the cause, so that it can be addressed.
- Extraneous matter: Any extraneous material found floating in the milk tank (insects, chaff, straw, etc.) results in the entire tank being rejected at the farm. Usually these are the result of careless handling, improper filtering, improper cleaning of the udder, etc.
- Churned milk / butterballs: These are caused by excessive agitation at warm temperatures, and may be floating or visible on the sides of the tank.
- Frozen milk: Evidence of ice in the milk is a sign that the bulk tank is malfunctioning and overcooling the milk. Like butterballs, ice in milk is most visible either floating on the surface or frozen to the sides or bottom of the tank. Milk that has been frozen can impact the results of lab testing.
- Excessive foaming: Foam in the milk tank may be caused by any of a number of mechanical issues – an agitator running too quickly, a short fill pipe or air leak in the milk line during milking – or rancidity. Since foam is high in fat, its presence could affect the proper evaluation of milk’s butterfat, in the lab.
- Curdled milk: More often than not, curdling is a sign of milk that has soured. It may have a high bacteria count, and could cause errors in readings of butterfat and somatic cells.
Milk haulers should be familiar with these so that they can adequately evaluate potential issues as they arise. In some cases, the milk may just need to sit for 10 minutes, and then be reassessed. In others, however, the driver will reject the milk onsite and will not load it onto the truck’s tank. Milk haulers need to know the difference in order to confidently make the right call.
Grading milk’s appearance is an integral part of food safety protocol. While any health risks will undoubtedly be discovered by the testing facilities, insufficient oversight by haulers can result in a whole truckload of healthy milk being needlessly wasted because of one contaminated pickup. That’s why it’s so important for drivers to learn the look of healthy lactose – and to take the necessary steps when something’s off.