Milk bags are plastic bags that carry milk. They are usually stored in a pitcher or jug with one of the corners cut off to allow for pouring. A typical milk bag contains approximately 11⁄3 litres of milk in North America and 1 litre of milk in Eastern Europe and the Baltics.
Milk bags in Canada
Bagged milk is common in many parts of Canada. The innovation was introduced in 1967 by DuPont using European equipment. The new packaging quickly found favour with the indigenous dairy industry since it allowed them to supplant glass bottles which were heavier and more prone to breakage. However, the consumer public preferred plastic jugs for years, but largely accepted the new containers in certain regions in the 1970s. A major reason for that shift was with the national conversion to the metric system, which was easier to adjust to on production with bags while doing the same for jugs required entire systems to be wholly redesigned.
They are sold in eastern Canada, but not widely in western Canada (Manitoba, Saskatchewan, Alberta and British Columbia). Three bags are sold together in a larger bag containing a total of 4 litres of milk. The bags are not sold individually, and are either not labeled at all or labeled with only the expiry date, the lot number and sometimes the type of milk contained in the bag. The three-bag 4 litre package is the largest normally sold at retail, with the lowest unit price. Some convenience store chains offer 4-litre plastic jugs instead of milk bags, even in eastern Canada.
Two accessories are commonly associated with Canadian milk bags: pitchers and bag openers. The key-shaped bag opener with a clip and a magnet was invented in Toronto in 1979. These bag openers are a common type of refrigerator magnet, although the bags can be opened with scissors or knives.
In other countries
Milk bags were also common in the former Soviet Union[dubious ], and other Eastern bloc countries, such as Poland, East Germany, Hungary, Romania, Bosnia & Herzegovina and Bulgaria. They remain popular in the Baltics (e.g. Estonia) and some other Eastern European countries, where they may also be seen used for packaging yogurt. A resurgence of milk bags is beginning in Britain amid concerns that plastic bottles aren't being recycled. Milk bags were also used in Australia (Greater Shepparton, Victoria), in the late 1990s, distributed by Shepparton-based dairy company Ducats. Some dairies in the United States used the bags in the 1980s, but today are confined mainly to regional convenience store chains with in-house dairies such as Kwik Trip in the Upper Midwest and other boutique dairies.
In Russia milk bags are often made not from the single-layer LDPE, but from sturdy laminated paper that uses at least two paper and three LDPE layers, similar to what is used for the common milk cartons, and may include aluminum foil for better protection of the bag's insides. Such bags are much more difficult to pierce, which greatly simplifies handling and reduces losses in transportation. It also makes a bag more rigid, so it is able to sit on the counter upright by itself, and can be poured without help of a holding pitcher, though it still remains difficult to reseal. It is possible to seal it again with the hot clamps that make the polyethylene coatings stick to each other, but barely anyone bothers.
In the United Kingdom, Sainsburys began a pilot experiment on distributing milk in bags in 2008 in conjunction with Dairy Crest. It was originally targeted at 35 stores at the same price as a regular 2-imperial-pint (1.1 l) plastic bottle of milk, the product was expanded through the North of England nationwide in 2010 at which point the bags retailed at a discounted price compared to traditional containers.
In the UK the bags are usually used in conjunction with a specialized plastic jug. The bag fits snugly inside the jug, one corner of the bag is secured under a bar at the front of the jug, and as the lid is closed the bag is pierced and a spout slides into the hole, allowing the milk to be easily poured and maintaining freshness. Doorstep deliveries in the United Kingdom are normally associated with traditional glass milk bottles, but the Dairy Crest/Milk and More service also deliver milk bags, and sell Jug-It brand plastic jugs specially designed to hold the milk bags.
Normally, people will only open one bag at a time, and then open another one when the first one is empty. That means that the milk in the bags which are still sealed lasts longer than milk in a jug which is being repeatedly opened.
When pouring, the top of the bag can topple over, causing the milk to spill. Spillage can be avoided by cutting a secondary hole at the other side of the bag for air intake, by pinching the top of the bag while pouring, or by using a pitcher with a lid to keep the milk bag in place. Milk bags cannot easily be sealed once open, although some consumers fold over the spout and use clips to help maintain freshness. Also, a common single-ply LDPE bag is easy to pierce and tear, and must be handled and transported with care to avoid product losses and messes.
While milk bags use less plastic than the traditional jug, there is no incentive on consumers to recycle the bags, such as the refunds provided when jugs are recycled at a bottle depot. In Canada, where recycling services are municipally or regionally managed, milk bags are not always able to be recycled. In some municipalities milk bags are required to be thrown away  and in others they are recyclable. This inconsistency in waste management programs between municipalities and the inability to recycle milk bags leads to excessive plastic waste.
- Kelly, Cathal (2010-02-04). "So we drink milk from bags. Does that make us weird?". Toronto Star. Retrieved 20 January 2014.
- Kelly, Cathal (2010-02-04). "So we drink milk from bags. Does that make us weird?". Toronto Star. Retrieved 20 February 2014.
- "Snippit bag opener".
- Blades, Hollye (2008-06-09). "Pinta goes green as supermarkets offer shoppers the chance to buy milk in a bag". The Times (London).
- Neate, Rupert (2008-06-09). "Milk in bags hits Sainsbury's shelves". The Daily Telegraph (London).
- Wallop, Harry (2010-02-24). "Milk in a bag at Sainsbury's". The Daily Telegraph (London).
- SEDESOL, Liconsa (2012-04-27). "Liconsa". Sedesol (Mexico).
- Chertoff, Emily (1 August 2012). "The Surprising History of the Milk Carton". The Atlantic. The Atlantic. Retrieved 26 August 2015.
Media related to Milk bags at Wikimedia Commons
- Milk Bags Demystified A woman demonstrates the nature of the packaging and how it is readied for use.