In February 2021, Mark Bello, the owner, and operator of Pizza School NYC, helped Fox News Digital judge an unappealing slice of pizza before buying it.

Bello has demonstrated pizza making at the James Beard House and was named a "pizza expert" at the Food & Wine masters series. By his own estimation, he has tasted thousands of pizzas, both in the U.S. and abroad. And when it comes to trying out a new slice shop, he tells Fox News to beware of five red flags.

THE ORIGIN OF PIZZA

National Pizza Day is an unofficial holiday in the U.S., although the tradition of eating pizza in the western hemisphere dates back to the early large-scale Italian immigration during the late 19th and early 20th century. 

Inherited directly from Italy, there existed two types of distinct American pizza styles: Chicago deep-dish and New York pizza. The Chicago pies have a high edge and fluffy bread that allows for the pizza to be filled with an abundant amount of sauce and cheese. The New York pizza had a thinner crust from thick dough with less tomato sauce but large amounts of mozzarella. 

Before World War II, pizza was a popular dinner food among Italian immigrants before veterans from the Italian campaign in Europe started eating it after returning home. By the 1960s and 1970s, large pizza chains like Dominoes and Pizza Hut began to emerge all over the country.

The modern Pizza Day every Feb. 9 is meant to be a celebration of the Italian custom as well as a chance for communities and friends to break bread over a widely popular Americanized dish. Here are some of the tips Bello told Fox News Digital to look for during the pizza holiday. 

1. Too-good-to-be-true-deals
2. Sorry-looking slices
3. The wrong ingredients
4. It's praised as great "drunk food"
5. Their cheese slice stinks

Bello said consumers should immediately be wary "if the place is trying to sell you on the quantity of the pizza over the quality of the pizza."

That doesn’t mean the pizza is necessarily bad. It’s just the first of a few factors that point to poor pizza.

Quality pizza is always going to look appetizing, but it’s not always going to look consistently the same, even between slices from the same pizzeria. And it should never be too "pale," Bello says.

"If the outer crust resembles the rim of a Styrofoam cup in geometry, uniformity and pale color, it’s likely going to taste like the outer rim of a Styrofoam cup," according to the expert.

Depending on the size of the pizzeria, some shops may have their ingredients — cans of tomatoes, bags of flour, cheese — on display or at least in view of customers. If you sense something amiss with the ingredients, take your tastebuds elsewhere.

"For example, often pizzerias have their bags of flour stored in view of the customer. If they say ‘bromated’ and/or ‘bleached’ that’s not good," Bello says, referring to flours that have been treated to change their pigments, to help develop gluten or to strengthen the dough.

Good pizza should taste like good pizza all the time — not only when you’re inebriated.

Or, as Bello advises, never go out of your way "if the overwhelming recommendations you hear for the pizzeria in question emphasize ‘it’s best if you go there at 3 a.m. when you're really drunk.'"

So the pizza seems slightly questionable, but it looks halfway decent, and you can’t see the ingredients. In that case, stick with a single cheese slice. It’s the ultimate indicator of the rest of the menu, according to Bello.

"If their classic cheese and sauce slice is bad, move along," the expert advises.

Mark Bello is the owner and operator of Pizza School NYC. Since 2010, the company has shared its knowledge of pizza with over 50,000 students. For more visit Pizza School NYC’s official website at pizzaschool.com.