How Long Will They REALLY Last? Part I: Non-perishables

Part I - Shelf-Stable Foods

The most popular (most often visited) Q/As on Shelf Life Advice are ones that ask, "How long can I keep it?" The product section of Shelf Life Advice provides answers to these questions about specific foods. This article will give you some general guidelines--provided by scientists on the Shelf Life Advice Advisory Board--on various categories of shelf-stable foods.  (Perishables will be discussed next month.) Along with info about how long foods can last (beyond the "use-by" date) are tips on how to extend shelf life beyond the usual expectations. Some foods, if treated right, will essentially last indefinitely. 

"Use-by" dates indicate when a food will begin to decline from its peak quality.  Knowing that frustrates shoppers. What they want to know is when the food will--to be blunt-- taste rotten, look lousy, and/or smell stinky, in other words be spoiled, too disgusting to eat.  Notice I didn't add "become contaminated" because pathogens that cause food-borne illness are a different matter and may come about because of different issues. Of course, consumers also want to know when a food will become unsafe. Some make the expensive mistake of thinking that "use-by" dates are the mark of danger telling them to throw the food out.  But "use-by" dates are NOT about safety.  They are about quality and warnings of future spoilage rather than contamination.

Why, you may wonder, don't manufacturers tell consumers when the food will become spoiled?  Here's why: a decline in peak flavor, texture, etc. doesn't necessarily mean you won't enjoy the food.  That's a subjective matter.  Example:  After milk has been open a week, it tastes bad to me, but my husband insists it's fine.  Who's right?  We're both right.  Week-old milk isn't contaminated; it won't hurt you; only your taste buds can tell you whether or not to use it.  (Tip:  you may not like the taste when you drink, it but it will be fine in a soup or pudding.) 

ENVIRONMENTAL FACTORS THAT AFFECT SHELF LIFE

Shelf life is defined by food scientist Dr. Karin Allen as "the length of time a food can be held without loss of nutritive value (an objective calculation) and quality (a subjective determination).  A food becomes spoiled, she says, when a change occurs that makes it unacceptable to ME! 

What keeps many foods fresh even at room temperature? Products that are acidic or high in sugar or salt are very stable. The acidity or alkalinity of a product is expressed using the pH scale that commonly ranges from 0 to 14.  The number 7 equals neutral.  If the pH is low (as in canned goods), the product is acidic and less likely to allow microbial growth. Food process engineer Dr. Tim Bowser says, "If properly processed and packaged, low-moisture and low-pH (high acid) foods should be stable long beyond their listed shelf life." 

Shelf-stable products will last even longer if they're well-sealed and kept in a cool, dark place. That's why many people commonly store mustard, catsup, peanut butter, and other non-perishables in the fridge.

Dr. Allen mentions that water activity is an important factor affecting shelf life. The phrase "water activity" does not refer to the amount of water in a particular food but to the amount of water that is AVAILABLE for microbes. If water is tied up with sugar or salt, it is not available for microbes.  If there is sufficient available water, mold growth can occur, but the types of molds that grow on food are not usually ones that cause illness. However, molds can produce harmful toxins that can grow on some dry products, such as peanuts and corn.   

What about the effects of heat, humidity, and light on the shelf life of so-called nonperishable products? Dr. Bowser considers temperature one of the most important factors in prolonging or shortening the shelf life of food.  Some consumers have learned this lesson the hard way when canned goods subjected to very hot weather exploded and messed up the entire pantry. 

Food scientist Dr. Joe Regenstein explains that the effects of temperature, humidity, and light are factored into the end date. Humidity is important in paper packaging.  For metal cans, only the temperature makes a difference, but products canned in glass may be affected by light. According to food scientist Dr. Cutter, light may accelerate rancidity in some foods, especially those with fat.

PRODUCT CATEGORIES

Sugar:

It will last indefinitely unless moisture gets into it and causes clumping.  Sugar can also get infested with bugs, which is not a health problem but an aesthetic one that will probably make you discard the sweetener.

Grains, Pasta, Beans, and Legumes:

If they don't smell bad and aren't providing meals for bugs, you can keep them long past the "use-by" date. After you've opened the packages, it can't hurt to double-wrap them in a plastic bag. 

These products can oxidize over time, more hastily if subjected to high heat or high humidity.  Dr. Allen says, "If an off odor is objectionable, the flavor of the cooked product probably will be, too." If it smells bad, don't cook it; discard it.  Also, check these products for insects.

Dr. Allen also points out that some packaged noodles and rice products contain flavor packets that may turn rancid more quickly than the pasta itself.

Flour:

Flour is a very long-lasting product, but it will oxidize over time, and it also attracts bugs.  Once you've opened the bag, sealing it in a plastic bag may help keep bugs and moisture out.

If a product made with flour also contains fat (shortening) that will shorten its shelf life.  Read the labels on products such as pancake batter and biscuit mixes.  If they contain fat, it might be wise to obey the "use-by" dates.

Flour can be frozen to lengthen shelf life.  However, Dr. Cutter supplied a warning based upon personal experience:  Her father sent her a package of grits (coarsely ground corn) and didn't tell her that the package had been frozen.  She put it in her cupboard, where, within a short time, it became moldy (due to moisture). Dr. Regenstein suggests that, whenever you take something out of the freezer that you may want to use only part of and then store the rest, don’t open it immediately; allow it to reach room temperature while sealed.  Once it's at room temperature, it can be opened and will not draw in moisture.

Crackers and Cookies:

Let's face it, these get stale.  I've sometimes purchased individually-wrapped cookies that tasted stale even before they'd reached their "use-by" date.  However, some people are probably more sensitive to that stale taste than others.  Dr. Allen offers the following helpful bits of information:

- Crackers still in their overwrap have a much longer shelf life.  Don't expect those crackers you put on a plate with cheese to hold up very long.  However, as long as they smell okay, they'll taste okay.

- Drier cookies have a longer shelf life than moist cookies.

- Repackaging cookies and crackers at home doesn't do much to maintain shelf life.   At home, you can't vacuum-package them or add nitrogen, which is what's needed for longevity.

Commercially Canned Foods:

The FDA considers canned foods to have an essentially unlimited shelf life.  Despite the "use-by" date stamped on the lid, if the cans are properly canned and show no signs of rust, dents, bulging, or leakage, then old age is not a safety concern.  Furthermore, according to Dr. Allen, the quality of canned goods deteriorates very slowly. Vegetables long past their "use-by" date may not taste great, but they can still be used in strongly flavored dishes. 

A dented can may still be safe, but not if a seal is compromised.  Whether that has happened or not may be difficult for the average consumer to determine, so the safest advice is to discard a dented can or return it to the store.  

A swollen can is a warning of danger. Microbial spoilage following leakage or under-processing, the germination of spores within the can, the interaction of acids in the food product with the metals of the can, or other causes may make a can bulge.  Do not eat the contents of a can that is swollen or has a bulging top.  It could cause illness, and it could explode.  Discard it immediately.

Two incidents Dr. Cutter witnessed:

1) As an experiment, her students heated some closed cans in a 400°F oven for about an hour and then out set them on a counter.  Within a few days, they bulged. 

2) Some campers put a sealed can of beans on a campfire.  The result was very messy.

Tips: Canned goods left in a hot warehouse have also been known to explode, which suggests that, in hot weather, you should not leave canned goods in your car trunk or garage. Also, don't store canned goods next to your stove.

Peanut butter:

The shelf life of an open jar of peanut butter, even stored at room temperature, may be 2-3 months. Kept in the fridge, the shelf life is at least 6 months. Why so long? The oil ties up the water and protects the peanut butter from spoilage bacteria to a great extent. However, eventually it can get slimy or moldy; if it does, throw away the entire container.  Also, a chemical reaction called oxidation may cause the product to develop a bad smell; if that happens, discard it.

But remember that shelf life ends when the product BEGINS to decline in nutritive value and quality.  Your peanut butter may taste and look fine to you even after the time periods listed above.  But if you are eating peanut butter or any other shelf-stable food primarily for a particular nutrient (or nutrients), then that shelf life date may be more important to you.    

Jams, Jellies, and Syrups:

Open jars of jelly and jam can last indefinitely unless mold develops. The water activity and pH of sugar-containing jams and jellies makes them inherently safe.  However, if you see mold, don't try to remove it; just discard the entire jar because invisible mold may have spread throughout the product, spoiling its taste.  All open jars of low-sugar and sugar-free jams and jellies need to be refrigerated not just to maintain quality but to assure safety. 

Many syrups--imitation maple, corn syrup, and molasses--don't need refrigeration.

Condiments:

Catsup, hot sauces, and barbecue sauces contain preservatives to prevent mold or yeast growth. Check salsas, tartar sauce, and creamy condiments for mold after they've been open for a few weeks.  Mustard and horseradish are natural preservatives, but they can lose flavor due to oxidation. Refrigerate all these products once they've been opened.  That will extend their shelf life and keep the creamy ones safe to consume. 

Seasonings:

Salt and baking soda have an unlimited shelf life, but baking powder will eventually lose its leavening power. 

What about dried herbs and spices?  According to the experts at the Spice House in Evanston, Illinois, the shelf life of these dried products varies quite a bit depending upon the type of spice and the form it's in.  For example, peppercorns may last 4 years, but poppy seeds will barely last a year. As you might expect, whole spices will hold up longer than ground spices.  As dried spices and herbs age, they oxidize and lose flavor.  However, that doesn't mean they're dangerous or spoiled; it just means that you need to use a greater quantity to get the taste benefit you got from a smaller amount of fresher product. 

Dr. Allen offers these tips: Unopened bottles have a longer shelf life.  Seasoning mixes in unopened foil pouches should keep their high quality for several years.  As with many products, storage in a cool, dark place lengthens shelf life; heat causes flavor loss to happen more quickly.  Herbs lose flavor faster than spices.  (For an explanation of the difference between herbs and spices, click here.) 

I'm convinced that, despite the shelf life dates of 6 months to 2 years on various dried spices and herbs, these products can last a long, long time even if they're not pampered. When my kitchen was remodeled about 5 years ago, I purchased a revolving spice rack with many seasonings in it. I wanted to display this attractive item in my new kitchen.  I didn't want to hide it in a cabinet, and it was too big for that anyway. When I learned that light would hasten deterioration of the spices and herbs, I moved the rack from its original prominent location near a window to a darker space away from direct sunlight. Then I realized that the rack was sitting between my toaster and my convection oven, often a hot spot. Now I move the rack away from the heat when I use my toaster or oven--if I think of it.  Five years after purchase, these seasonings still retain their original scent. According to the folks at Spice House, if the scent is there, the taste will also be there. I no longer worry about the shelf life of my seasonings.  They may outlive me.

Dr. Allen had a brilliant solution to her problem with fancy spice bottles she wanted to show off without spoiling expensive spices.  She bought inexpensive spices to put in her fancy display bottles and kept more expensive spices and ones she used often and depended upon to do their flavoring job perfectly in her cabinet, in--you guessed it--a cool, dark place.

A few years ago, in her school's kitchen pantry, Dr. Allen found peppercorns that had probably been there since the 1950s.  They had not yet lost their scent or taste.  She points out that, since whole spices last longer than ground ones, when purchasing those you don't use often, it makes sense to buy them whole and grind a few as you need them.

A recently-conducted poll conducted by Health magazine found that 52% of those surveyed dish out food that has passed the expiration date.   Based upon comments by an expert the article quotes, the magazine goes on to say that the other 48% are probably wasting perfectly good food. 

Source(s):

Karin E. Allen, Ph.D., Utah State University, Dept. of Nutrition, Dietetics, and Food Sciences

Timothy J. Bowser, Ph.D., Oklahoma State University, Dept. of Biosystems and Agricultural Engineering

Catherine N. Cutter, Ph.D., Pennsylvania State University, Dept. of Food Science

Joe Regenstein, Ph.D., Cornell University, Dept. of Food Science

fda.gov "BAM: "Examination of Canned Food"

http://www.fda.gov/Food/ScienceResearch/LaboratoryMethods/BacteriologicalAnalyticalManualBAM/ucm109398.htm

ShelfLifeAdvice.com Write-ups on specific products.

Health "America's Wildest Food Habits, Revealed"

December 2012.