Most astute shoppers might guess that a pile of supposed Louis Vuitton handbags being hawked by a shady sidewalk vendor for $20 a pop are probably not authentic. But how about a lovely looking bottle of extra-virgin olive oil on the shelf of the supermarket? Even the savviest of shoppers might not suspect that behind the label lurk 12 ounces of, say, humdrum corn oil. Welcome to the world of food fraud.

In a country where we have relatively strict labeling regulations, many food manufacturers still manage to swindle shoppers by adding fillers or diluting the real deal with less expensive ingredients, without the knowledge of the consumer. And in fact, it’s become so prevalent that the U.S. Pharmacopeial Convention, a nonprofit that sets standards used by the FDA, set up a database to track the infractions. Called the Food Fraud Database (FFD), it describes food fraud as the "deliberate substitution, addition, tampering or misrepresentation of food, food ingredients or food packaging, or false or misleading statements made about a product for economic gain." It has a shocking number of entries.

And while a knockoff purse may pose little more harm than embarrassment upon its discovery, phony food can be a cause for concern. It can lead food allergy sufferers dangerously astray. As well, some items being used aren’t meant for human consumption, while others contain toxic components such as lead or melamine. While the list of foods on the database is extensive, here are some of the most commonly consumed ones to be on the lookout for.

1. Orange juice

What could be complicated about orange juice? It is made from oranges, juiced — except when it’s not. That some juice makers feel compelled to regularly pump up their product with non-orange ingredients seems far-fetched, but they do it. And in fact, orange juice is one of the most popular items to have suspect ingredients sneaked into the mix. The FFD is chock full of faux orange juices, one of the most shocking reveals a mixture of beet sugar, corn sugar, monosodium glutamate, ascorbic acid, potassium sulfate, orange pulp wash, grapefruit solids, and a byproduct from a water distillation system.

But nutritionists are railing against OJ for another reason. Packed with sugar, calories and carbs, orange juice isn't much better for you nutritionally than soda or any other sweetened beverage, reports Business Insider. Maybe that's why sales of orange juice are down, at a time when Americans are actually eating more breakfast than ever.

2. Honey

Mix some honey in a cup of warm tea to help soothe your laryngitis. Vladimir Kovalchuk/Shutterstock

Honey laundering has been making headlines lately due to a large-scale case in China where stocks are commonly tainted with a potentially dangerous antibiotic – launderers mask the honey's origin and the defiled product is whisked through the system to unwitting consumers.

Also at play, cheaper honeys are increasingly passed off as more expensive varieties. Honey is one of the most commonly mislabeled foods, representing 7 percent of food fraud cases. Last year, Food Safety News tested honey and found that 75 percent of store-bought honey didn’t contain pollen. People are still buying a product made from bees, but with no pollen food regulators are unable to identify the honey’s source. Consequent testing found that a third of all phony honey was imported from Asia and was contaminated with lead and antibiotics.

The National Honey Board says regulations do allow for pollen to be filtered out as part of the removal of “bee parts” and other organic matter, but there is still cause for dismay. The FFD lists a bevy of non-honey ingredients, such as sucrose syrup, sugar syrup, partial invert cane syrup, corn syrup, glucose syrup, high-fructose corn syrup, beet sugar, and a whole host of non-authentic sweeteners. The good news is that the tests from Food Safety News found all of their samples from farmers markets, co-ops and whole food stores like Trader Joes were authentic.

3. Truffle oil

This one comes as a shock to any self-respecting foodie upon its discovery. The fancy truffle oil that home chefs and beloved restaurants drizzle across pizza, pasta and salads ... isn’t flavored with real truffles. No, most commercial truffle oils are created by mixing olive oil with a synthetic petroleum-based flavoring agent, commonly 2,4-dithiapentane. The collective sound of gourmands’ hearts breaking when The New York Times did a story on the practice was nearly audible; all that dreamy reverie spent on a chemical created in a lab! Real truffle oil may be hard to find, but check the label for truffle “aroma” or “essence” to spot the imposter oils, both of these terms are not USDA-approved food descriptions.

4. Blueberries

Blueberries are already linked to better memory and heart health, so this is just one more good reason to eat them. (Photo: Brian A. Jackson/Shutterstock)

In 7 nutrition bars that are worse than candy, we discovered that the Berry Blast PowerBar (you know, the one with pictures of berries blasted across the wrapper) contained, ta-da, no berries whatsoever. Berries, and blueberries in particular, have become a superfood darling and consequently, commonly faked – there’s a pretty lengthy list of retail food items that contain words or photos suggesting that real blueberries were used in the products, when in fact, they weren’t.

The nonprofit Consumer Wellness Center reported that many "blueberries" in popular products they found were nothing more than glops of sugar, corn syrup, starch, hydrogenated oil, artificial flavors and artificial food dye blue No. 2 and red No. 40. And these are from popular manufacturers such as Kellogg's, Betty Crocker and General Mills. If you see bagels, cereals, breads, muffins, cereal and other items that promise blueberries, closely check the ingredient list for, you got it, actual blueberries. Also to note, artificial food dye blue No. 2 and red No. 40 likely indicate “fake blueberries at work here.”

5. Milk

Fake milk being sold as the real McCoy? It seems unfeasible, but it’s not. Milk is one of the most commonly adulterated food items out there. A look at the FFD turns up pages of search results for milk, with a nightmarish list of adulterants. For starters: Melamine, non-authentic animal sources, formaldehyde, urea, hydrogen peroxide, machine oil, detergent, caustic soda, starch, non-potable water, cow tallow and pork lard. Gulp.

6. Fish

Between sustainability issues and mercury levels, many of us are obsessively diligent about the fish we buy. So it’s depressing and distressing to discover that a study by Oceana from 2010 to 2012 found that 33 percent of the 1,215 samples they analyzed nationwide were mislabeled according to FDA guidelines. The samples were collected from 674 retail outlets in 21 states.

Samples labeled as snapper and tuna had the highest mislabeling rates (87 and 59 percent); only seven of the 120 samples of red snapper purchased nationwide were actually red snapper, the other 113 samples were another fish.

At the same time, farmed fish gets sold as wild catch and scallops are sometimes stamped-out whitefish. And buyer beware: A Consumer Reports study included a "grouper" sample that was really tilefish, a fish that contains frighteningly high levels of mercury.

7. Saffron

Few spices are as exotic or expensive as saffron, and consequently, few spices are knocked off as frequently. Commonly standing in for the costly crimson threads, according to the FFD, are creative adulterants such as marigold and calendula flowers, turmeric, corn silk, poppy petals, died onions, gypsum, chalk, starch, borax and glycerine, tartrazine, barium sulfate, sandalwood dye, colored grass and red-dyed silk fiber.

8. Olive oil

The business of fake olive oil is a lucrative one, with consumers getting regular olive oil instead of extra virgin or olive oil diluted with other oils. dominique landau/Shutterstock

Researchers have found that olive oil is the food most vulnerable to food fraud. In most cases consumers are getting a lesser quality than what is labeled – regular olive oil instead of extra virgin, or a cheaper, non-Italian variety being sold as Italian. But olive oil is also frequently diluted with imposter oils such as hazelnut oil, corn oil, sunflower oil, peanut oil, vegetable oil, soybean oil, palm oil and walnut oil. One sample even contained lard.

In rare instances, varieties of non-food-grade oil may be added in. In one notorious case, more than 600 Spaniards died in 1981 after eating a non-food-grade, industrial rapeseed oil that was sold as olive oil.

9. Pomegranate juice

Pomegranate juice is another food category undone by its own popularity. Ever since pomegranate juice hit the market, it has been lauded for its high antioxidant content, for which consumers are willing to pay a premium. So it’s with no little amount of frustration to find that “pomegranate” juice is often diluted with grape or pear juice, sugar and high-fructose corn syrup. There have also been reports of completely "synthetic pomegranate juice" that didn't contain any traces of the real juice at all.

10. Coffee

If you buy whole beans and grind them at home, there’s less of a chance that your morning joe has been "enhanced" with the confounding oddities that find their way into ground and instant coffee courtesy of sketchy coffee producers. The following have been found in these forms of coffee: twigs, coffee husks, roasted corn, roasted barley, roasted soybeans, chicory powder, rye flour, potato flour, burned sugar, caramel, figs, roasted date seeds, glucose, maltodextrins, starch and roasted ground parchment.

The moral of the story? Don't be scared by all of this, but be aware. Buy whole foods when you can. Shop at trusted co-ops and farmers markets when possible. Know that well-known names and bigger brands should be somehwat reliable, since they have a lot to lose if they're busted for mislabeling. And look out for deals that seem to good to be true; that super cheap saffron could well be nothing more than died daisy petals.