food shelf life

Shelf Life: How Long Does Your Food Last?

When doing groceries most people will always do one quick look on the date printed on the label. Sometimes it is “best before”, while other products write “best use by” or “sell by” date.

Do you ever wonder what those dates actually mean? What’s the difference between all these dates? Does that mean that food will be unsafe after that date?

The rising problem of food waste can be partly attributed to consumers’ lack of understanding of these date terms. Many people think that all food passing those dates should go to waste.

While it is understandable that consumers want to stay on the safe side, these dates have different meanings and should not be seen in a similar manner.

In this article, we’ll take a closer look at food shelf life, food product dating, and how we can make better use of food from this information.


What Does Shelf Life of Food Mean?

Shelf life is a period of time when a food product remains safe and suitable for consumption when properly stored at recommended conditions. This means that food should retain its desired quality and doesn’t lose its nutrients [1]. This period is calculated since production, distribution, sale, and until finally stored in your kitchen.

Many factors affect the shelf life of a food product, These are a combination of inherent factors of the product (intrinsic) and other external factors (extrinsic), such as:

  • quality of the ingredients
  • initial microbial level
  • nature of the ingredients (ph, moisture content, pH)
  • product formulation
  • manufacturing process (pasteurized milk has a shorter shelf life than ultra-pasteurized one)
  • packaging
  • storage conditions

These factors are usually manipulated or improved to extend the shelf life. As consumers, we can maintain and extend the shelf life of food products we buy with proper storage as instructed by the manufacturers.

According to the storage condition, in general, food items can be grouped into:

Perishable food

Perishable foods include fresh or minimally processed foods or not otherwise preserved, such as pasteurized milk, ready-to-eat salad, fresh sauce, raw meat. These foods typically have a short shelf life and rely on refrigeration to reduce the deterioration rate.

Shelf-stable food

Shelf-stable foods have a longer shelf life and can be safely kept at room temperature. These foods are preserved with different methods, for example, heat treatment, canning, modified atmosphere packaging, etc.


How Is Shelf Life Estimated?

Shelf life is specific to food products as it is affected by a combination of multiple factors. It is the responsibility of the manufacturer to estimate the food shelf life. Thorough studies are conducted by taking into account many factors that may end the shelf life.

The methodologies are generally divided into direct and indirect methods [2]. The direct method involves full-length storage under normal conditions from production to consumption, as close as to realistic conditions. The product is examined from time to time to determine at which point of time it doesn’t meet quality properties.

Some food commodities have a stable shelf life and can last for months or even years. Running a full storage trial seems tedious and costly. In this situation, indirect methods offer a solution. These methods include accelerated shelf-life tests, challenge tests, predictive microbiology, or a combination of them.

Accelerated shelf-life test increases the rate of deterioration by applying higher storage temperature. The result is then used to calculate shelf life under normal storage conditions. Predictive microbiology uses computer modeling to predict microbial activities that will spoil the product. Meanwhile, challenge tests introduce microorganisms or pathogens that may exist in normal storage conditions.

Shelf life of foods varies considerably, but typical foods have a similar range of shelf life such as canned food and dairy products.


How Long Does Canned Food Last?

Canned foods are shelf-stable. They should be properly stored at a cool, dry place, away from sources of heat and sunlight.

Commercially prepared high acid foods such as canned tomatoes and fruits maintain their peak quality for at least 12 – 18 months. Low acid food such as canned fish or meat last longer up to 2 – 5 years. Meanwhile, home-canned foods are generally safe up to a year [3].

Never purchase and consume canned food if the packaging is damaged; leaking, dented, bulging, or if the container smells off and spurts liquid upon opening. This food may pose a risk to botulism poisoning.

How Long Do Dairy Products Last?

Most dairy products require refrigeration, except ultra-pasteurized milk and powder milk. Their shelf life can vary significantly. Shelf life for typical dairy products with proper storage in the refrigerator are as follows [4], [5]:

  • Pasteurized milk: 1 – 2 week
  • Yoghurt: 2 – 6 weeks
  • Soft cheese (ricotta, brie, cream cheese): 1 – 2 weeks
  • Hard and semi-hard cheese (gouda, parmesan): depending on the cheese, from several weeks to months
  • Buttermilk: 1 – 2 weeks

These shelf lives may be shortened if your refrigerator is too warm. The ideal temperature should be below 40 ºF or 4 ºC.


How Long Does Cooked Food Last?

Cooked foods are perishable and should be stored in the fridge. Cool temperature slows down microbial growth but doesn’t stop it.

Unless frozen, cooked food should be consumed within 3 – 4 days. If food has sat in the fridge for too long, it may have spoiled and is unsafe for consumption. 

Some pathogenic bacteria such as Listeria monocytogenes can survive chilling temperatures and cause food poisoning if consumed.


What is the Expiry Date?

Shelf life is indicated on food packaging as what most people know as an “expiry date” or “expiration date”. 

This date comes in different terms (depending on the food). It can be a “best-before” date, “use-by” date, or “sell-by date”. This is where the terms become so confusing!

Depending on which country you are, regulation on food product dating may vary. In the United States, the regulation is quite relaxed and date marking is not required by federal law, except for infant formulas [6]. 

In the European Union, food producers should provide such information, except for some products such as alcoholic beverages, vinegar, cooking salt, solid sugar, etc. [7]


What Is The Difference Between Shelf Life and Expiry Date?

Shelf life refers to a period during which a food product stays in the desired quality and suitable for consumption. To indicate the end of food shelf life, food manufacturers print “expiry date” on the label.

An expiry date is an estimate from the manufacturer as a practical guide for retailers and consumers. But, the actual shelf life can be longer or shorter than this date

When stored properly, food may stay edible beyond this date. On the other hand, subject to poor storage or damaged packages, the shelf life may be ended even before the date on the label.


Do Food Expiration Dates Really Matter?

Date marking is an estimate from the producers. Use this date as a guide for your purchase and consumption. 

In general, food does not necessarily and instantly go bad after the date, if the instructed storage conditions are followed.

Below are the most common date terms and how you should interpret them:

Best-before / Best-use-by date

This is an estimate from the manufacturer to guarantee the quality and not a safety concern. This date is usually for shelf-stable food that can last for more than one or two years, for example on canned food, frozen foods, dried food, biscuits, pasta, etc.

Sell-by-date

This guides the retailers how long they can display the food for sale. Food may still remain safe to eat although the quality has passed its peak. This date term is commonly found in the US and usually stamped on fresh products such as eggs, pasteurized milk, raw meat, or chicken.

Use-by date

This indicates the latest date food should be consumed [9]. This date marking is usually for highly perishable food such as ready-to-eat salad and cooked meats. 

Consuming food that is past this date is not recommended since it may raise safety concerns. The food may have lost the nutrient contents and even worse pose microbial risks.

Date of manufacturing or date of packaging

This can be printed instead of the other date terms. You can see this example on a sake bottle.

This date is applicable for some foods that are not likely to spoil such as candy, chewing gum, vinegar, alcoholic beverages with >10% ABV (except those containing dairy cream such as Baileys). 

Due to the nature of the ingredients (sugar, alcohol, acid), these foods don’t support microbial growth and will not likely to spoil


Are expired foods safe to eat?

Provided with proper storage, foods with “best-before” and “sell-by” dates generally remain safe, but the quality (flavor, texture, taste) may not be the best. 

A recent study confirmed that six months after their “best before” dates, food products including milk, pasta, mayonnaise, and jam remained safe, but changed in flavor, taste, or texture [8].

You may want to pay more attention to highly perishable products which usually come with a “use-by” date, such as ready-to-eat salad or cooked meats. 

In this case, you should avoid consuming the food past the date. If you’re reluctant to waste the still-looking-good food, don’t do it longer than 1 – 2 days. The quality may have significantly declined and the safety could be questionable. Use or freeze the food before this date.

Use your senses to assess the questionable food. If you are doubtful, better to toss it.

Is it OK to eat expired canned food?

It is possible to eat expired canned food as long as the packaging is in perfect condition. Make sure the can is not leaked, dented, bulged, or spurt liquid when opened.

Can Expired Food Cause Food Poisoning?

Food poisoning is caused by the contamination of pathogenic/ harmful bacteria. This contamination does not exclusively happen after food has expired. Even before the date, contamination can happen due to poor handling. For example when food is left at room temperature for too long, cross-contaminated with other food, or when the package is damaged.

Shelf-stable food is generally safe after the date on the label. However, for perishable foods, you may want to look carefully. Most pathogenic bacteria causing food poisoning are odorless or flavorless.

You should always check spoilage signs before eating food, particularly for expired food. If you are doubtful, you probably better stay on the safe side.


Common Methods to Extend Shelf Life

Food, by its nature, will deteriorate over time. However, the speed can be slowed down by different methods of food preservation. The following methods are worth trying if you need to prolong your supply and to avoid unnecessary food waste.

Fermentation and Pickling

Fermentation might be the oldest food preservation method. Any food ingredient containing sugar can be fermented with the help of microorganisms, either lactic acid bacteria or molds/ fungus.

Milk, fruit juice, vegetables, and soybean are the most common items for fermentation. Fermentation does not only preserve food but also imparts flavor, taste, texture, and nutritional value of the food which are desirable for many people. [10]

Many of today’s food items were made by the fermentation process. These food items make up a significant part of the regular diet in most of the world’s population. Examples of fermented food are:

  • Cheese, yogurt, kefir
  • Tempeh, soy sauce, natto, miso
  • Kimchi, sauerkraut,
  • Kombucha (fermented tea)
  • Beer, wine, vinegar

Pickling is also a popular way to preserve vegetables by fermenting them in a solution consisting of water, vinegar, salt, sugar, and spices. Many people find it easy to do at home. While cucumber is the most common vegetable to pickle, other pickled vegetables taste great as well.


Refrigeration and Freezing

Most food items belong in the fridge. Room temperature is a real enemy to most food items since it provides a favorable condition for microorganisms to grow and spoil your food. Perishable food should not stay at room temperature for too long.

However, some fruits and vegetables do not need refrigeration, such as onion, garlic, coffee, potato, sweet potato, banana, honey, cucumber.

Tips for refrigeration

Separate fruit and vegetables:

Some fruits and vegetables emit ethylene gas, including apple, onion, pear. Unless you want to speed up the ripening process of your avocado or banana, this gas is a real enemy for most vegetables. Separate these foods from your vegetables, such as when storing broccoli.

Don’t place milk and dairy products on the door

Dairy products are very sensitive to temperature change. If you open the fridge frequently, milk spoils faster due to sudden temperature change. Place them at the back of the fridge, except if you plan to empty the bottle immediately.

While freezing is an easy yet effective way to prolong the shelf life of food items, the flavor and texture may change after defrosting. Most foods do freeze well, but some don’t. These include jello, coleslaw, egg white, mayonnaise, sour cream, etc. [11]

Tips for freezing:

  • Divide the food into portion size
  • For paste, sauce, or liquid, consider freezing them on ice cubes trays. This comes handy when you only need a small amount to thaw. This trick works well with lime and lemons juice, pesto, and beef broth.

Which Foods Can You Freeze?

Here’s a list of common foods that you can freeze:


Curing

When it comes to preserving meat, curing might be the oldest method invented. Curing process involves adding salt (salting), or combined with spices and nitrite/ nitrate.

This mixture effectively inhibits the growth of microbes by pulling out the water content. Some popular cured meats are ham and chorizo.

Aside from meat preservation, curing also refers to a natural process to heal physical wounds of root and tuber crops, such as sweet potato, potato, and cassava. The curing process forms new skin over scratches, consequently, prolongs the shelf life.

Additionally, during the process, starch is converted to sugar, thus developing a sweet flavor. Curing process should be completed before storage or sale [12].


Drying

Drying is a common way to preserve food, both at home and commercial production. Removal of water inhibits bacterial growth, consequently, prolongs shelf life. Traditional drying uses sunlight, smoking, or as simple as air drying.

It’s not difficult to find dried foods in our kitchen. These include sun-dried tomatoes, herbs, spices, dried meat, salted codfish, coconut flour, etc.

If you have to deal with your fruit/ vegetable harvest, drying them is a worth to make the most out of your produce. Drying food is easy and can be done in some different ways using a dehydrator, oven, sun drying, air drying, even in a microwave. [13]


Vacuum packing

Vacuum packing aims to remove air from food containers to limit the growth of anaerobic bacteria and slow down oxidation, consequently, prolong shelf life. This method is commonly used for meat, fish, cheese, vegetables, nuts, and many more.

Vacuum packaging does not replace the need for cold storage for perishable foods. Thus, always keep these foods in the refrigerator or freezer. [14]


Sugaring

The preserving mechanism of sugaring is similar to salting. Water content is removed to limit bacterial growth.

Sugaring works perfectly for fruits, such as apples, pears, mango, ginger, and many more. Making them into jam, marmalade, or candied fruits will significantly extend fruit shelf life.


Canning

Canned products are very easy to find, from canned meat, fish, fruits. Almost any food items can have their canned version.

Canning is highly effective to extend shelf life and make perishable foods become shelf-stable, making them safe to keep at room temperature.

Home canning is also getting more popular to prolong homemade food items, such as applesauce or pickles. Make sure you follow the canning procedure correctly to keep your food safe. USDA and National Institute of Food and Agriculture provide a complete guide to home canning here.

How To Tell If Your Food Has Gone Bad or Spoiled

Food, either plant-based or animal-based, will break down naturally. Deterioration can be as quick as raw meat spoils after several hours. 

The changes can also occur slowly over days or weeks, like how bread goes stale or sesame oil becomes rancid. Meanwhile, spoilage is mostly attributed to microbial activities.

Food spoilage degrades the appearance, smell, and taste of foods. To tell if food has gone bad, the rule of thumb is to carefully examine these aspects. Your senses are quite reliable tools to judge. If you’re still doubtful, the simple rule is to throw the food.

Damaged packaging

First thing first, don’t purchase or consume a food item if the packaging is compromised, e.g. broken seal, dented, bulged, rusty. The packaging is the last barrier to protect food from the outside environment.

When packaging is compromised bacteria will easily contaminate and grow. Nobody can guarantee if the food is still suitable and safe for consumption.

Mold

The presence of mold is a common sign of food going bad. Molds can grow in a wide array of food products.

Molds don’t need much water to grow, therefore even food with low water content is prone to molds. These include peanuts, pistachio, corn, oatmeal, pumpkin seeds, bread, etc.

Some nuts and grains are susceptible to mold contamination that produces toxins called aflatoxins which are carcinogenic to humans [15].

Molds also tolerate sugar, salt, and acid. Thus, molds can grow on cured meats, jam, and cheese.

If molds grow on porous, soft material like your pesto, casserole, bread, these foods must be trashed. Molds may have penetrated further than you can see.

Fortunately, not all moldy foods must go to waste. If molds grow on a hard, dense surface you can cut off at least 1 inch around and below the affected part and save the rest.

These foods include hard cheeses (including a block of parmesan, not grated one), firm fruit, or vegetables (such as bell peppers, carrots). If molds appear on hard salami and dry-cured hams, simply scrape the molds off the surface as these products are common to have surface mold [16].

Discoloration

Foods should be in the color they are supposed to be, like broccoli should be green or banana should be yellow. If you notice a change in color or your food turns darker, it’s a sign that it has past its prime.

Bruises cause discoloration on fruit and sweet potato. Unless the bruises are all over the surface, it is okay to remove the affected part and eat the rest.

Smell

An unpleasant smell is an apparent indication that food is spoiled and unfit for consumption. Each food has a distinct smell when it’s still fresh. If your food smells different in any way than it’s supposed to be, it has probably gone bad.

Dairy products turn sour, whole foods with high oil content smell rancid. Some foods like yogurt and coleslaw are naturally sour, but when they smell awfully sour, it’s also time to discard them.

Texture

A change in texture is the next thing to observe. Milk tends to thicken and curdle, fruits get mushy when spoiled. Some foods also get slimy. These are clear signs to throw foods away.

Foods that are high in oil tend to separate when put in cool temperatures, like your Nutella or peanut jam. This is normal, give it a good stir to get the consistency back.

Sprouting

Tuber and root vegetables, like potatoes and sweet potato,will begin sprouting after a while. You can easily remove the sprout and save the rest. But if the vegetable has severely shriveled, there’s no good in consuming it since the nutrients are already gone.

Pantry pests

Pantry bugs, like flour beetle and moth, are after dry goods such as flours, rice, and grains. These bugs may have been in the package when you bought it. Discard infested foods outside to prevent the bugs from spreading and always keep food containers tightly sealed.


Our List of Common Foods and Their Shelf Life

Simply click on each food name below for a detailed guide of its shelf life:

Dairy

Fresh Meat and Deli Meat

Processed or Cooked Foods

Fruits and Vegetables

Grains

Nuts and Seeds

Sauce and Condiments

Confections and Desserts

Flour and Baking Products

Canned and Bottled Products

Liquid and Beverages

Alcoholic Products

Conclusion

Shelf life is a length of time when foods have the desirable quality and are safe for consumption when stored under normal storage conditions. Food producers indicate the end of shelf life on the label. The dating term can vary from one food to another, that is “best before”, “use-by”, “sell-by” date.

Contrary to popular belief, most food items may stay good after these dates. Unless you see any signs of spoilage, feel free to eat them. But keep in mind that changes in the flavor of taste might happen.

Food handling is critical in maintaining a food shelf life. Never purchase food items if the package is damaged. Likewise, don’t take any products from the refrigerated shelf if the temperature is too warm. Always practice hygiene and follow storage instructions to keep your food stay fresh until the end.

References

[1] D. Kilcast and P. Subramaniam, The Stability and Shelf-life of Food, Cambridge: Woodhead Publishing Limited, 2000.
[2] New Zealand Food Safety Authority, “A Guide to Calculating the Shelf Life of Food,” February 2005. [Online]. Available: www.nzfsa.govt.nz. [Accessed 07 May 2020].
[3] USDA, “How long can you keep canned goods?,” 17 July 2019. [Online]. Available: https://ask.usda.gov/s/article/How-long-can-you-keep-canned-goods. [Accessed 8 May 2020].
[4] Dairy Food Safety Victoria, “Shelf-life of dairy products,” [Online]. Available: https://www.dairysafe.vic.gov.au/consumers/keeping-dairy-food-safe/shelf-life-of-dairy-products. [Accessed 8 May 2020].
[5] USDA, “How long can you keep dairy products like yogurt, milk, and cheese in the refrigerator?,” 17 July 2019. [Online]. Available: https://ask.usda.gov/s/article/How-long-can-you-keep-dairy-products-like-yogurt-milk-and-cheese-in-the-refrigerator. [Accessed 8 May 2020].
[6] USDA, “Food Product Dating,” 2020. [Online]. Available: https://www.fsis.usda.gov/wps/wcm/connect/19013cb7-8a4d-474c-8bd7-bda76b9defb3/Food-Product-Dating.pdf?MOD=AJPERES.
[7] Food Safety Authority of Ireland, “Shelf-life: Best before and use-by dates,” [Online]. Available: https://www.fsai.ie/faq/shelf_life/best_before_and_use_by.html. [Accessed 8 May 2020].
[8] D. Zielinska , B. Bilska, K. Marciniak-Łukasiak, A. Łepecka, M. Trzaskowsk, K. Neffe-Skocinska, M. Tomaszewska, A. Szydłowska and D. Kołożyn-Krajewska, “Consumer Understanding of the Date of Minimum Durability of Food in Association with Quality Evaluation of Food Products After Expiration,” International Journal of Environmental Research and Public Health, vol. 17, no. 1632, 20 March 2020.
[9] Codex Alimentarius, “General Standard for the Labelling of Prepackaged Foods,” Codex Alimentarius, 2018.
[10] N. S. Terefe, “Food Fermentation,” in Reference Module in Food Science, Elsevier, 2016.
[11] National Center for Home Food Preservation, “Foods that do not freeze well,” [Online]. Available: https://nchfp.uga.edu/how/freeze/dont_freeze_foods.html. [Accessed 8 May 2020].
[12] FAO, “Principles of Storage for Roots and Tubers,” [Online]. Available: http://www.fao.org/3/X5415E/x5415e03.htm#3.1.1%20curing%20of%20root%20and%20tuber%20crops. [Accessed 8 May 2020].
[13] University of Minnesota Extension, “Drying food at home,” [Online]. Available: https://extension.umn.edu/preserving-and-preparing/drying-food. [Accessed 8 May 2020].
[14] National Center for Home Food Preservation, “Should I vacuum package food at home?,” [Online]. Available: https://nchfp.uga.edu/publications/uga/vacuum_packaging.html. [Accessed 8 May 2020].
[15] Department of Food Safety and Zoonoses WHO, “Aflatoxins,” February 2018. [Online]. Available: https://www.who.int/foodsafety/FSDigest_Aflatoxins_EN.pdf. [Accessed 8 May 2020].
[16] USDA, “Molds on Food: Are they dangerous?,” [Online]. Available: https://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/safe-food-handling/molds-on-food-are-they-dangerous_/. [Accessed 8 May 2020].

*Photo by [email protected]/depositphotos

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