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Plastic milk containers are plastic containers for storing, shipping and dispensing
milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modul ...
. Plastic bottles, sometimes called
jug A jug is a type of container commonly used to hold liquids. It has an opening, sometimes narrow, from which to pour or drink, and has a handle, and often a pouring lip. Jugs throughout history have been made of metal, and ceramic, or glass, and ...
s, have largely replaced
glass bottle A glass bottle is a bottle made from glass. Glass bottles can vary in size considerably, but are most commonly found in sizes ranging between about 200 millilitres and 1.5 litres. Common uses for glass bottles include food condiments, soda, liq ...
s for home consumption. Glass milk bottles have traditionally been reusable while light-weight plastic bottles are designed for single trips and plastic recycling.


Materials

Packaging of milk is regulated by regional authorities. Use of
food contact materials Food contact materials are materials that are intended to be in contact with food. These can be things that are quite obvious like a glass or a can for soft drinks as well as machinery in a food factory or a coffee machine. Food contact materia ...
is required: potential food contamination is prohibited. Strict standards of cleanliness and processing must be followed. The most common material in milk packaging is
high density polyethylene High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, ...
(HDPE), recycling code 2. Low density polyethylene (LDPE) and
polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natu ...
(PET) are also in use.
Polycarbonate Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures. Polycarbonates used in engineering are strong, tough materials, and some grades are optically transparent. They are easily work ...
had been considered but had concerns about potential contamination with
bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on an industrial s ...
.


Container forms

Blow molded plastic milk bottles have been in use since the 1960s. HDPE is the primary material but polyester is also used. A wide variety of milk bottle designs are available. Some have a round cross section while others have a more square or rectangular shape. A special flat-top square milk jug was recently developed to maximize shipping and storing efficiency but had some difficulties in dispensing. Many milk bottles have integral
handles A handle is a part of, or attachment to, an object that allows it to be grasped and manipulated by hand. The design of each type of handle involves substantial ergonomic issues, even where these are dealt with intuitively or by following tr ...
.
Milk bag A milk bag is a plastic bag that contains milk. Usually one of the corners is cut off to allow for pouring, and the bag is stored in a pitcher or jug. A typical milk bag contains approximately of milk in South America, Iran, Israel, and contin ...
s are also in use. The milk is sold in a
plastic bag A plastic bag, poly bag, or pouch is a type of container made of thin, flexible, plastic film, nonwoven fabric, or plastic textile. Plastic bags are used for containing and transporting goods such as foods, produce, powders, ice, magazines, ...
and put into a
pitcher In baseball, the pitcher is the player who throws ("pitches") the baseball from the pitcher's mound toward the catcher to begin each play, with the goal of retiring a batter, who attempts to either make contact with the pitched ball or draw ...
for use. Larger bags are the inner bladder of a
Bag-in-box A bag-in-box or BiB is a container for the storage and transportation of liquids. It consists of a strong bladder (or plastic bag), usually made of several layers of metallised film or other plastics, seated inside a corrugated fiberboard box. ...
, sometimes used for institutional dispensing. Small individual containers of milk and cream are often thermoformed or injection molded and have a peelable lid. These are often used in restaurants.


Shelf life

The
shelf life Shelf life is the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale. In other words, it might refer to whether a commodity should no longer be on a pantry shelf (unfit for use), or no longer on a ...
of pasteurized milk in HDPE bottles and LDPE pouches has been determined to be between 10 and 21 days when stored at 4–8 °C. Other factors such as light and temperature abuse have effects. Shelf life can be extended by ultrapasteurisation and
aseptic processing Aseptic processing is a processing technique wherein commercially thermally sterilized liquid products (typically food or pharmaceutical) are packaged into previously sterilized containers under sterile conditions to produce shelf-stable products ...
.


Volume control

Milk containers for retail sale must contain the same amount of milk as indicated on the label. To be acceptable to consumers, the containers must also appear to be completely full. Therefore, the volume of the container must be precisely controlled. The designer of a die for a blow moulded bottle can never be completely sure of how much the finished bottle will hold. Shrinkage always occurs after the item is released from the mould. The amount of shrinkage depends upon many factors, including cycle time, inflation air pressure, time in storage prior to filling, storage temperature, and more. A volume adjuster insert is one way to slightly adjust the volume of a bottle, without building a completely new mould. A volume insert attaches to the inside of a mould, creating a circular indentation on the side of the finished bottle. Different size inserts can be used as manufacturing circumstances change, for example mould temperature or cooling rate. The volume of finished bottles is periodically measured, and volume inserts are changed as needed.


Environmental comparisons

Many potential factors are involved in environmental comparisons of returnable vs non-returnable systems. Researchers have often used
life cycle analysis Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for assessing environmental impacts associated with all the stages of the life cycle of a commercial product, process, or service. For instance, in the case of ...
methodologies to balance the many diverse considerations. Often the comparisons show benefits and problems with all alternatives. One recent life cycle study of one-way recyclable HDPE bottles indicated the importance of secondary packaging: returnable plastic crates can allow lower tare weight bottles. Reuse of bottles requires a
reverse logistics Reverse logistics encompasses all operations related to the upstream movement of products and materials. It is "the process of moving goods from their typical final destination for the purpose of capturing value, or proper disposal. Remanufacturing ...
system, cleaning and, sanitizing bottles, and an effective
Quality Management System A quality management system (QMS) is a collection of business processes focused on consistently meeting customer requirements and enhancing their satisfaction. It is aligned with an organization's purpose and strategic direction (ISO 9001:2015). ...
. A key factor with glass milk bottles is the number of cycles of uses to be expected. Breakage, contamination, or other loss reduces the benefits of returnables. A key factor with one-way recyclables is the recycling rate: In the US, only about 30–35% of HDPE bottles are recycled.


Examples

File:Coffee fresh (2012.08.04).jpg, Individual plastic container of coffee creamer, Japan File:Spring roll with milk.jpg, 11.5 US fl oz, 340 ml, PETE bottle File:Israeli Milk Bag.jpg, Plastic bags of milk File:Plastic bottle of milk.jpg, 1419 ml, 48 US fl oz PETE bottle File:Square milk jug side.JPG, Flat-top square jug File:Plastic Milk Bottle.tif, HDPE milk bottle, 40 US fl oz, 1 1/4 US quart


See also

*
Gallon smashing Gallon smashing is the act of spilling a gallon of liquid, approximately 3.78 liters in the United States, usually by breaking its container (hence 'smashing'), in a manner that appears to be accidental. The act often involves throwing a gallon of ...
, internet challenge involving participants deliberately spilling milk in a supermarket by breaking containers


References


Books, general references

* Yam, K.L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009,


External links

{{Packaging Milk containers Liquid containers Retail packaging