I'm a chef who loves to shop at Costco - but there are 12 things I never buy there

Nuts are a fantastic snack and ingredient, but this 2 1/2-pound tub of five different nut varieties that have been roasted and salted is a pass for me.

Nuts are high in natural oils, which can go rancid easily. And though roasting nuts certainly improves the flavor, it also significantly decreases their shelf life.

Plus when you get five different nuts in one container, you attract dreaded cherry pickers — or maybe you're the one leaving behind the starchy Brazil nuts and gobbling up all of the salty cashews.

Your best bet is to buy Costco's single-variety packs of unroasted nuts and keep them in your freezer for maximum freshness.

Husked corn is more convenient, but taking a few minutes to remove your own silk is guaranteed to be worth the effort for flavor and crunch.

It's impossible to know how long ago this plastic-wrapped corn was undressed. Plus the longer corn hangs around in the buff, the more it dries out and loses its flavor and nutrients.

After you've conquered the impressive feat of prying open this nearly 7-pound can of tomato sauce you're probably going to have a lot of leftovers unless you're feeding a village.

And that red stuff won't last forever. Sure, you can freeze it, but you'll need multiple containers and a lot of freezer real estate to house those tomatoes.

This is an item you're better off buying in smaller cans since it's inexpensive and much easier to manage.

Save yourself the disappointment of a stale bowl of cereal and pick up your favorite breakfast from the regular grocery store.

Extra-large boxes of cereal will likely either lose its crunch or you'll get tired of it before you finish off 3 pounds of the stuff.

Even the most generous burrito-stuffers probably don't need 3 quarts of sour cream in their fridge.

Despite being pasteurized, this dairy product may spoil or go moldy before you can make the most of it — especially if you're double-dipping.

Unfortunately, most dairy products don't freeze well either. Stick to smaller containers of dairy products like sour cream and yogurt for the freshest flavor and lowest food-safety risk.

Not only does this two-pack of extra-large cans of seasoned panko bread crumbs present an obvious storage issue, but also these aren't not going to stay fresh forever.

Bread crumbs go stale just like regular bread, but you can't freeze them to extend their shelf life. Plus these bread crumbs are pre-seasoned with cheese, which is likely to diminish their shelf life even faster.

Instead, you can choose a smaller container of bread crumbs and add your own seasonings.

Despite all of the processing, sliced deli meats have a very brief shelf life once they're opened.

You're better off choosing freshly-sliced ham from your local butcher or deli counter in an amount that you can consume within a few days.

I think you're better off buying fresh salmon at Costco's seafood counter and marinating the fish yourself than buying anything frozen and pre-seasoned.

Protein, especially delicate fish, shouldn't be marinated indefinitely. Over time, the fish's flaky texture will break down and you'll end up with something much mushier than the soft, buttery texture you're looking for.

Extended periods of freezing can have the same effect, making this frozen and marinated salmon something to avoid.

As a general rule, I say pre-shredded cheese often has less flavor than cheese you grate at home.

There's no telling how long ago this cheese was shaved from its block and blended with three other cheeses. And although you can see both orange and white cheese shreds in the mix, it's impossible to identify each of the four varieties from the others or to know how much of each kind you're working with.

In my opinion, what's the point of melting cheese into your quesadilla if you can't taste the complex and delicious flavors that are carefully developed by cheese makers?

Whether you're at Costco or the neighborhood market, just say no to pre-peeled garlic.

No one likes the tedious task of prying papery skin off a tiny clove of garlic — but it's a labor of love and the only way to get fresh garlic flavor into your food. Pre-peeled cloves tend to be dried out, woody, and lacking flavor.

Plus this 3-pound pouch of garlic is only going to degrade in flavor and attract bacteria after it's been opened.

And, for the sake of your family and friends, don't put that kind of pressure on yourself to finish the bag before it goes bad.

There's a reason that Parisian bakers are at work by 5 a.m. every day. It's because their precious loaves, croissants, and tartlets are at their best the very day they're baked.

Unless you're feeding a classroom or going to a potluck, there's no need to invest in a container of pastries that you won't be able to finish in a day or two at most.

Chances are, you can also find higher-quality treats at a shop that bakes in smaller batches.

Depending on the season, you can keep fruit fresh in the crisper drawer for some time. But if you're buying fruit that's already past its prime, and in big quantities to boot, you're not doing yourself any favors.

Delicate fruits like stone fruit and berries are best bought in smaller quantities and locally, if possible. The further fruit has to travel to reach your store, the more time there is for damage.