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Milk bag

Milk bag is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Milk bag rather than just read about it. In short: A milk bag is a flexible plastic pouch used to package milk and is used in some areas instead of a hardened milk jug. Usually one of the corners is cut off to allow for pouring, and the bag is stored in a pitcher.

Milk bag — main illustration
Milk bag — illustration

Key takeaways

  • Milk bag belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Milk bag to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Milk bag from memory before moving on to harder problems.

Reference excerpt

A milk bag is a flexible plastic pouch used to package milk and is used in some areas instead of a hardened milk jug. Usually one of the corners is cut off to allow for pouring, and the bag is stored in a pitcher. A typical milk bag contains approximately 1 L (1.8 imperial pints) of milk in South America, Iran, Israel, and continental European countries, while in Canada they contain 1+1⁄3 L (2.3 imp pt), and in India, 0.5 L (0.9 imp pt). In the Baltic rim countries and some Eastern European countries, similar bags may also be seen used for packaging yogurt or kefir.

Benefits

For producers, it is easier to vary portion size when sealing bags than cartons, as well as lowering the cost of packaging. Milk bags also take up less space in the garbage. For consumers, bags typically allow for smaller portion sizes. This theoretically reduces the risk of spoilage, as well as the space and location of storage in the fridge.

Recycling While milk bags use less plastic than standard plastic bottles or jugs, empty bags are often not accepted for recycling when mixed with other plastics. In Canada, where recycling services are municipally or regionally managed, milk bags may not always be recycled. In some municipalities milk bags are required to be discarded as garbage and in others they are recyclable.

By country and region This is not an exhaustive list of all the countries where bagged milk is commonly sold.

Canada

In Canada, milk was packaged in heavy, reusable imperial unit glass milk bottles, cardboard cartons and plastic jugs. In 1967, DuPont, using European equipment, introduced plastic bags to store and sell milk. These bags gained widespread acceptance in some parts of Canada due to 1970s metrication in Canada, when bottles, jugs, and cartons had to be redesigned and manufactured in metric units; milk bag packaging machines could easily be resized. The consumer largely accepted the new containers in parts of Ontario, Quebec and the Maritimes in the 1970s. Regulation in Ontario that required retailers to collect a deposit on milk jugs, but not bags, also motivated the practice. Milk bags are sold (typically packaged three in a larger 4L sack) in parts of Ontario, Quebec and the Maritimes. They are not common in western Canada.

India Milk bags are commonplace in India, with an estimated 30% of milk sold in the country being packaged this way. There has been limited compliance from dairy businesses in buying back consumer plastic as required by the Maharashtra Pollution Control Board.

Israel

In Israel, bags are the most common type of packaging for milk. They became the standard form of milk packaging in the 1960s, with the discontinuation of glass bottles. Milk bag prices are controlled by the state. Therefore, price differences exist between them and other alternatives like plastic bottles or cartons. Due to the price differences, a relationship was observed between the socioeconomic status of the consumer and the type of milk container that they customarily purchased. The higher the socio-economic status of the purchaser, the more likely they are to buy milk in cartons rather than in bags, despite the higher price of cartons. Based on these differences, Blue Square Network created a way to measure the socioeconomic status of an area based on the sales ratio of milk cartons versus bagged milk. The higher the ratio of the former to the latter, the higher the status of the region in Israel. For religious Jews, opening a bag of milk can be considered problematic on Shabbat, because the action requires cutting. Eli Yishai, Israel's former minister of internal affairs, used empty milk bags in the Knesset as props to complain about price-hikes in the cost of milk.

South America Milk bags are also commonly used in Colombia, Ecuador, Argentina, Bolivia, Brazil, Chile, Paraguay, Peru, and Uruguay.

United Kingdom In the United Kingdom, Sainsbury's 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 nationwide in 2010, at which point the bags retailed at a discounted price compared to traditional containers, but stopped in early 2015.

United States DuPont introduced milk bags to American schools in 1989; by 1993 three million pouches a day were being served in 24 states. However, the popularity of them waned. There appears to only be one verified school district, in Omaha, NE, using bagged milk as recently as 2015.

European Union A few countries of the European Union sell milk in bags, as well as in the other types of containers, such as in Estonia (e.g. brands like Farmi, Valio/Alma, or Pilos).

See also Food portal Milk bottle Milk carton Plastic milk container Square milk jug

References

External links

Canadian Milk Bags Demystified on YouTube—a woman demonstrates the nature of the packaging and how it is readied for use

Illustrations

Milk bag: A milk bag
A milk bag
Milk bag: Pitcher used to hold a milk bag
Pitcher used to hold a milk bag
Milk bag: Packaging of milk bags in Pakistan
Packaging of milk bags in Pakistan
Milk bag: Neilson Dairy milk bags and cartons in Ontario, Canada
Neilson Dairy milk bags and cartons in Ontario, Canada
Milk bag: Israeli milk bags
Israeli milk bags

Worked examples

Example 1 — a first encounter with Milk bag

Start with the simplest possible case. Write down what Milk bag claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Milk bag before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Milk bag ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Milk bag

In research
Milk bag appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Milk bag in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Milk bag is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bags, Milk containers, so understanding it makes those chapters shorter.
In everyday life
Look for Milk bag outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Milk bag in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Milk bag means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Milk bag out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Milk bag in simple terms?

A milk bag is a flexible plastic pouch used to package milk and is used in some areas instead of a hardened milk jug. Usually one of the corners is cut off to allow for pouring, and the bag is stored in a pitcher.

Why does Milk bag matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Milk bag?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Milk bag.

Tags

  • Bags
  • Milk containers

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