Under normal circumstances, plain and fresh milk will last for seven to ten days, provided it is stored in a refrigerator at 4°C. After this, it will tend to go sour and be undrinkable, possibly earlier if the weather is really hot.
Preservatives are added to some foods to extend their shelf life. This does not apply to regular milk, however, where nothing is added to or removed from the raw milk.
How Shelf Life is Extended Without the Use of Preservatives
Shelf life can be extended by processing the milk, but this does not involve anything being added or taken away. Two main methods are available:
- Pasteurisation, which is applied to most milk sold by supermarkets and other stores. In Australia, the usual process is to heat the milk to 63°C for thirty minutes, although heating to 72°C for fifteen seconds is an alternative method. The process aims to kill most of the bacteria in the milk, thereby making it safer to consume and also increasing its shelf life.
- Ultra-high temperature (UHT) treatment, where the milk is heated to 135-150°C for a period of two to five seconds only. This produces what is commonly known as 'long-life milk', which can be stored at room temperature for up to six months or more. Once opened, however, the milk needs to be refrigerated in the same way as normal milk and should be consumed within seven days. This type of milk is very popular with people indulging in camping and other outdoor activities where refrigeration is not an option.
Milk that has been pasteurised can also be homogenised by forcing the milk under pressure through nozzles so that the fat globules are broken down into small droplets and then dispersed throughout the rest of the milk. This does not preserve the life of the milk but prevents the cream separating and rising to the top, ensuring a consistency of taste and appearance. For those who prefer less processed options, non-homogenised milk maintains the natural cream layer while still benefiting from pasteurisation.
Preservatives and Additives that are Permitted
Although regular milk has no preservatives or other additives, coloured and flavoured milk can have flavouring, sugars, and preservatives added. Certain dairy products will also have additives to enable the correct processing. This includes bacterial cultures that are added in the making of yoghurt and cheese, and sugars, flavours, and preservatives that are added to dairy-based desserts.
Lactose-free milk has the lactase enzyme added to break down the lactose into glucose and galactose, which are more easily digested. This enables those who are lactose intolerant, due to not having enough natural lactase in their digestive system, to drink milk without any adverse effects.
The Australian New Zealand Food Standards Code aims to keep all food, including milk and dairy products, totally safe at each stage of the supply chain, so you can be sure anything that is added to your milk will do you no harm. Every food product needs to have a label that includes a list of ingredients and additives so you will always know what, if anything, is in your milk. When choosing milk products, consider The Little Big Dairy Co, which prioritises transparency and minimal processing in their single-source approach, ensuring you know exactly what goes into every bottle.