You know that store-bought guacamole that sat in the back of your fridge for months because you forgot about it? Melanie Warner, author of Pandora's Lunchbox: How Processed Foods Took Over the American Meal discovered such a tub, but found that it was strangely fresh, even after several months (Her mother even accidentally ate it -- and was fine!). In response, Warner took it upon herself to conduct some serious home science projects with foods aging over time. The results are a bit alarming -- preservatives are a powerful thing.

Warner recorded four experiments for the masses. Here, she tested a fast food fried chicken sandwich versus a homemade breaded chicken sandwich. Check out what happens after Warner leaves the two sandwiches out over a period of four months:

Next up, Warner found out what happens when you leave out store-bought "fresh" guacamole and homemade guacamole. Here's a hint -- if the store-bought version never turns brown, there may be something else besides avocado lurking in there...

American cheese singles versus cheddar cheese:

And, the strange evolution of frozen chicken tenders:

Surprised? Or not at all?

Also on HuffPost:

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  • Low Fat

    Low fat is an FDA-regulated term that requires food bearing its label to have three or fewer grams of fat per serving.

  • Natural

    You may be surprised to learn that the term "Natural" has no actual FDA guideline behind it. Instead, it's a commercial term meant to sell products. Though <a href="">according to the FDA</a>, they traditionally don't object to the term if the food in question is free of "added color, artificial flavors, or synthetic substances." The USDA does require that any meat or poultry product labeled "natural" have <a href="">additional labeling to explain in what way it is natural</a> (e.g. "minimally processed").

  • Light

    A "light" label is regulated by the FDA and can refer to fat, calories or sodium. If referring to fat, the "light" food must have at least 50 percent less fat than the original version of the product. If the food began with fewer than 50 percent of its calories derived from fat, the "light" label can refer to a reduction of a third or more calories, or a 50 percent or greater reduction in sodium.

  • Zero Trans Fats

    Foods must contain fewer than half a gram of trans fat per serving to get the "zero trans fat" label, which has led to criticism that people may be <a href="">unknowingly eating a substantial amount of trans fat</a> on a daily basis.

  • Organic

    The term organic, on its own, doesn't have a legal definition from the FDA. But if the label says USDA Organic, it has been accredited by the USDA and thus contains a minimum of 95 percent organic ingredients. Another USDA label, "100 percent organic" requires all of the ingredients to be fully organic.

  • Made From Organic Ingredients

    Like USDA Organic, "Made from organic ingredients" is a USDA certified label, though it has a lower threshold: instead of 95 percent, 70 percent of the ingredients must be organic.

  • Cholesterol Free

    "Cholesterol free" foods must have fewer than two milligrams of cholesterol per serving as well as fewer than two grams of saturated fat per serving.

  • Whole Wheat

    Foods that are labeled<a href=""> whole wheat and 100% whole wheat</a> are the only labels that actually mean a food made with whole wheat flour.

  • Multigrain

    This label simply means that more than one type of grain was used to make the product, though it doesn't necessarily indicate that the grains were whole and thus healthier.

  • Lean

    The USDA requires meat that is labeled as "lean" to have fewer than 10 grams of fat, 4.5 grams of saturated fat, and 95 milligrams of cholesterol per 100 grams. Of note, this regulation is grandfathered in, which means that meat that has consistently been labeled lean since before 1991 can retain the label even if it doesn't meet the requirements.

  • Free Range

    For poultry, the term "free range" is enforced by the USDA and means that <a href="">the animals were allowed access to the outside</a>. Of note, many eggs claim "free range" status, though the USDA does not regulate the term "free range" for <a href="">egg producing poultry or for beef</a>.

  • Low Sodium

    Low sodium foods must have 140 or fewer milligrams of sodium per serving -- that's about 10 percent of the recommended daily allowance, per the 2010 Dietary Guidelines for Americans.

  • 'Good' Source Of

    When foods claim to be a good source of a particular vitamin or nutrient, <a href="">they must prove that they have at least 10 percent</a> of the USDA's recommended daily allowance. "Provides" and "contains" are synonymous with "good source of" in the eyes of the FDA.

  • 'High' Source Of

    When foods claim to be a high source of a particular vitamin or nutrient, they must prove that they have <a href="">at least 20 percent</a> of the USDA's recommended daily allowance.

  • Reduced Fat

    'Reduced fat' refers to a food that has less than half the fat of its original version.