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Shelf life is the length of time that food, drink, medicine and other perishable items are given before they are considered unsuitable for sale or consumption. In some regions, a best before, use by or freshness date is required on packaged perishable foods.

Shelf life is the recommendation of time that products can be stored, during which the defined quality of a specified proportion of the goods remains acceptable under expected (or specified) conditions of distribution, storage and display.

Most shelf life labels or listed expiration dates are used as guidelines based on normal handling of products. Use prior to the listed date does not necessarily guarantee the safety of a food or drug. Thus, immediately after the date, a product is not always dangerous nor ineffective.

Shelf life

Shelf life is different from expiration date; the former relates to food quality, the latter to food safety. A product that has passed its shelf life might still be safe, but quality is no longer guaranteed. In most food stores, shelf life is maximized by using stock rotation, which involves moving products with the earliest sell by date to the front of the shelf, meaning that most shoppers will pick them up first and so getting them out of the store. This is important, as some stores can be fined for selling out of date products, and most if not all will have to mark such products down as wasted, leading to a loss of profit.

Shelf life is most influenced by several factors: exposure to light and heat, transmission of gases (including humidity), mechanical stresses, and contamination by things such as micro-organisms. Product quality is often mathematically modelled around a parameter (concentration of a chemical compound, a microbiological index, or moisture content), .

For some foods, the shelf life is an important factor to health. Bacterial contaminants are ubiquitous, and foods left unused too long will often acquire substantial amounts of bacterial colonies and become dangerous to eat, leading to food poisoning. However, the shelf life itself is not an accurate indicator to the food safety. For example, pasteurized milk can remain fresh for five days after its sell-by date if it is refrigerated properly. In contrast, if milk already has harmful bacteria, the use-by dates become irrelevant.

The expiration date of pharmaceuticals specifies the date the manufacturer guarantees the full potency and safety of a drug. Most medications are potent and safe after the expiration date. A rare exception is a case of Renal tubular acidosis purportedly caused by expired tetracycline. A study conducted by the U.S. Food and Drug Administration covered over 100 drugs, prescription and over-the-counter. The results showed that about 90% of them were safe and effective as far as 15 years past their expiration date. Joel Davis, a former FDA expiration-date compliance chief, said that with a handful of exceptions - notably nitroglycerin, insulin and some liquid antibiotics - most expired drugs are probably effective.

Preservatives and antioxidants may be incorporated into some food and drug products to extend their shelf life. Some companies use induction sealing and vacuum pouches to assist in the extension of the shelf life of their products.

Some degradation factors can be controlled by use of appropriate packaging. For example, the amber bottle used for many beers blocks damaging wavelengths of light. Transparent beer bottles do not. Packaging with barrier materials (e.g. low moisture vapor transmission rate, etc) extends the shelf life of some foods and pharmaceuticals.

The United States Department of Defense (DoD) Shelf-Life Program defines shelf-life as,
The total period of time beginning with the date of manufacture, date of cure (for elastomeric and rubber products only), date of assembly, or date of pack (subsistence only), and terminated by the date by which an item must be used (expiration date) or subjected to inspection, test, restoration, or disposal action; or after inspection/laboratory test/restorative action that an item may remain in the combined wholesale (including manufacture's) and retail storage systems and still be suitable for issue or use by the end user. Shelf-life is not to be confused with service-life (defined as, A general term used to quantify the average or standard life expectancy of an item or equipment while in use. When a shelf-life item is unpacked and introduced to mission requirements, installed into intended application, or merely left in storage, placed in pre-expended bins, or held as bench stock, shelf-life management stops and service life begins.)


Temperature control

Nearly all chemical reactions will occur (at various rates depending on the individual nature of the reaction) at common temperatures. Examples are the breakdown of many chemical explosives into more unstable compounds. Nitroglycerine is notorious. Old explosives are thus more dangerous (i.e., liable to be triggered to explode by very small disturbances, even trivial jiggling) than more recently manufactured explosives. Rubber products also degrade as sulphur bonds induced during vulcanization revert; this is why old rubber bands and other rubber products soften and get sticky as they age.

These breakdown processes characteristically happen more quickly at higher temperatures. The usually quoted rule of thumb is that chemical reactions double their rate for each temperature increase of 10 Celsius degrees (C°) because of activation energy barriers become more easily surmounted at higher temperatures. However, as with all rules of thumb, there are many caveats and assumptions. This particular one is most applicable to reactions with activation energy values around 50 kJ/mole; many of these are important at the usual temperatures we encounter. It is often applied in shelf life estimation, sometimes wrongly. There is a widespread impression, for instance in industry, that "triple time" can be simulated in practice by increasing the temperature by 15 C°, e.g., storing a product for one month at 35 °C simulates three months at 20 °C. There is enough variation that this practical rule cannot be routinely relied upon.

The same is true, to a point, of the chemical reactions of life. They are usually enzymatically catalyzed which changes reaction rates, but with constant catalytic action, the rule of thumb is still mostly applicable. In the particular case of bacteria and fungi, the reactions needed to feed and reproduce increase at higher temperatures, up to the point that the proteins and other compounds in their cells themselves begin to break down, or denature, so quickly that they cannot be replaced. This is the reason high temperatures kill bacteria and other micro organisms; 'tissue' breakdown reactions reach such rates that they cannot be compensated for and the cell dies. On the other hand, 'elevated' temperatures short of these result in increased growth and reproduction; if the organism is harmful, perhaps to dangerous levels.

Just as temperature increases speed up reactions, temperature decreases reduce them. Therefore, to make explosives stable for longer periods, or to keep rubber bands springy, or to force bacteria to slow down their growth, they can be cooled. This is the reason shelf life is generally extended by temperature control: (refrigeration, insulated shipping containers, controlled cold chain, etc) and the reason some medicines and foods must be refrigerated.

Temperature data loggers, RFID tags and Time Temperature Indicatrs can record the temperature history of a shipment to help determine the remaining shelf life.

Parallel names

Best before

Best before is sometimes indicated on food and drink wrappers, followed by a date, and is intended to indicate the date before which the supplier intended the food should be consumed. The term Best before is similarly used to indicate the date by which the item will have outlived its shelf life, and is intended to ensure that customers will not unwittingly purchase or eat stale food. Sometimes the packaging process involves using pre-printed labels, making it impractical to write the Best before date in a clearly visible location. In this case, a term like Best before see bottom or Best before see lid might be printed on the label and the date marked in a different location as indicated.

Best before is usually advisory and refers to the quality of the product, in contrast with Use by and Best by which indicate that the product is no longer safe to consume after the specified date .

Use by

Generally, foods that have a use by date written on the packaging must not be eaten after it has expired. This is because such foods usually go bad quickly and may be injurious to health if spoiled. It is also important to follow storage instructions carefully for these foods (for example, product must be refrigerated).

Foods that have a best before date are usually safe to eat after the date has passed, although they are likely to have deteriorated either in flavour, texture, appearance or nutrition.

Bathroom products/toiletries usually state a time in months by which, once the product is opened, they should be used. This is often indicated by a graphic of an open tub, with the number of months written inside (e.g., "12M" means use the product within 12 months of opening).

Open dating

Open Dating is the use of a date or code stamped on the package of a food product to help determine how long to display the product for sale. It is also beneficial to the customer and ensures that the product is at its best quality when bought. An Open Date does not supersede a Use by date, which should still be followed.

Sell by / Display until

These dates are intended to help keep track of the stock in stores. Food that has passed its sell by or display until date, but is still within its use by / best before will still be edible, assuming it has been stored correctly. It is common practice in large stores to throw away such food, as it makes the stock control process easier. It also reduces the risk of customers buying food without looking at the date, only to find out the next day that they cannot use it. Tampering with the posted date is illegal in many countries.

Most stores will rotate stock by moving the products with the earliest dates to the front of shelving units, which allows them to be sold first and saving them from having to be either marked down or thrown away, both of which contribute to a loss of profit.

Mark-downs

It is also common for food approaching the use by date to be marked down for quick sale, with greater reductions the closer to the use by date it gets.

Issues associated with sell by / use by dates

According to WRAP, 33% percent of all food produced is wasted along the chill chain or at the consumer. At the same time, a large number of people get sick every year due to spoiled food. According to the WHO and CDC, every year in the USA there are 76 million foodborne illnesses, leading to 325,000 hospitalizations and 5,000 deaths.

UK government to replace sell by / use by dates?

According to UK minister Hilary Benn, the use by date and sell by dates are old technologies that are outdated and should be replaced by other solutions or disposed of altogether.

How to enhance sell by / use by dates?

There are many ways to enhance sell by and use by dates. These include a better education of consumers on how to use, transport and store fresh food products. Also, they can be improved by adding to the package smart indicators such as TTI's (Time Temperature Indicators). These show through a visible color change if the product is still fresh or not. Time Temperature Indicators are already in use by retailers and food producers in France (Monoprix, Carrefour), Switzerland (Kneuss) and other countries in western Europe.

Software Shelf Life

In a metaphorical sense, much software also has a shelf life. Most software products are released to market with defects, security vulnerabilities, and design flaws. Over time, some of these are discovered and patch issued by the vendor (and possibly others, as in the open source environment) which fix bug and add functionality. The result is that, after some time, the software application is rather different than it was at first release, even with the same version level. Since correct inclusion of patches at end user sites is spotty, the actual population of that software application in the field is quite varied; some will have patches 1 and 2, others 1, 2, and 3, some others none, in all possible variations. This increases support difficulty. There have been a few attempts to address this.

US Government Guidelines

The Food & Drug Administration, which regulates packaged foods and drugs, only requires a use-by, or expiration, date on infant formula and some baby foods. That's because formula must contain a certain quantity of each nutrient that is described on the label. And if formula is stored too long, it loses its nutritional quality, and also separates or form lumps that will clog the bottle nipple. Except for infant formula and some baby foods, product dating is not required by federal regulations.

The Agriculture Dept., which regulates fresh produce and meats, only requires labeling of the date when poultry is packed at the farm. However, many manufacturers also add sell-by or use-by dates.

The DoD Shelf-Life Program operates under the DoD Regulation 4140.1-R, DoD Materiel Management Regulation, ()
     A. There are items in the Department of Defense (DoD) and the Federal Supply System that require special handling due to certain deteriorative characteristics. These items are to be properly maintained to ensure that the customer is provided fresh, useable materiel. The purpose of this Manual is to establish a shelf-life program and process, with special emphasis on those items having these known deterioration characteristics, to mitigate the risk of shelf-life expiration and lapses of shelf-life items/materiel beyond their inspect/test dates.
B. Provide policy and basic procedures for the management of both non-consumable and consumable shelf‑life items that may be hazardous material (HAZMAT) or non-hazardous material, spanning all classes of supply and stored at all levels of the Federal Supply System. Shelf-life management for hazardous materiel follows the same procedures as those for any shelf-life items, except that hazardous materiel should receive priority processing over non-hazardous materiel. Issues and guidelines concerning the acquisition, storage, handling, transportation, and disposal of hazardous materiel are addressed in Chapters 3 and 5 of this Manual. Class I perishable subsistence, Class III bulk petroleum, Class V ammunition, and Class VIII-B blood, are excluded from this Manual and shall continue to be managed in accordance with existing regulations. Commodities excluded from this Manual may be represented by their respective DoD Component to the DoD Shelf-Life Board. The definitions for “classes of supply” may be found in Appendix 16 of DoD 4140.1-R.
C. This Manual endorses the pollution prevention measures in DoD Instruction 4715.4 for hazardous materiel (HAZMAT) minimization (HAZMIN), as well as, the establishment of hazardous materiel control and management (HMC&M) philosophies which include consolidation and reutilization practices that embrace HAZMIN and HAZMAT elimination to reduce the hazardous waste (HW) stream.
D. Appendices A through K augment this Manual and furnish additional information germane to the DoD Shelf-Life Management Program. Appendix L serves as a quick reference index to this Manual.


Example

Beer freshness date

A freshness date is the date used in the American brewing industry to indicate either the date the beer was bottled or the date before which the beer should be consumed.

Beer is perishable. It can be affected by light, air, or the action of bacteria. Although beer is not legally mandated in the USAmarker to have a shelf life, freshness dates serve much the same purpose and is used as a marketing tool.

Beginnings of freshness dating

General Brewing Company of San Francisco marketed their Lucky Lager Beer as "Age Dated" as early as late 1935. They stamped a date on each can lid to indicate that the beer was brewed before that date. This was not to insure that the beer was "fresh" but to insure that it had been aged properly. So many breweries had rushed beer to market before it was ready when Prohibition ended, that customers were wary of getting "green" beer.The Boston Beer Company, maker of Samuel Adams, was among the first contemporary brewers to start adding freshness dates to their product line in 1985. For ten years there was a slow growth in brewers adding freshness dates to their beer. The practice rapidly grew in popularity after the Anheuser-Buschmarker company's heavily marketed "Born-On dates" starting in 1996. Many other brewers have started adding freshness dates to their products, but there is no standard for what the date means. For some companies, the date on the bottle or can will be the date that the beer was bottled; others have the date by which the beer should be consumed.

Beer processing

Before a beer is bottled, it is process to prolong its shelf life; this evidently affects the beer's freshness date. It may be done in several ways, not all of which will be used by a particular brewery:

  • Pasteurisation is a process by which a liquid is heated for a brief time to kill microbes that may be in the liquid. Pasteurisation has also been used for many years to keep milk safe for drinking due to bacteria that may be present.


  • Sterile filtration, in which the beer is passed through a mechanical filtration system which removes anything larger than 0.5 micrometres. This removes any yeast or hops that may still be in the beer which would continue to react with it.




  • Freshness longevity affects the time it takes a beer to become stale. Some of this depends on the type of beer ingredients included. If the beer has more hops and more alcohol than otherwise, it will stay fresh longer than those that are not as strong.


See also



References

Further reading

  • Labuza, T. P., and Szybist, L., "Open dating of Foods". 2001, Food and Nutrition Press, Trumbul CN
  • "Cold Chain Management", 2003, 2006, [64164]
  • "Freshness and Shelf Life of Foods", Hugo Weenen and Keith Cadwallader, ISBN 0841238014
  • "Shelf-Life Evaluation of Foods", by C. M. Man, A. A. Jones, ISBN 0834217821
  • "Stability and Shelf Life of Food", by David Kilcast, Persis Subramaniam ISBN 0849308577


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