Spare Ribs vs Baby Back Ribs: What's the Difference?

Pork ribs are one of the first meats that beginners will choose to smoke. Their overall difficulty falls somewhere between pork butt (easy) and beef brisket (hard).

Pork rib cuts are sourced from two different parts of the pig and are known as Spare Ribs (including St. Louis cut) and Loin Back ribs (baby back ribs).

Where are These Ribs Located?

Loin Back Ribs

Back ribs or loin back ribs are taken from the upper portion of the rib cage, where the rib and spine meet.

As the name implies, they contain loin meat and are smaller in comparison to spare ribs. "Baby back" both implies where they're sourced from and their smaller size.

Spare Ribs

Spare ribs are taken from the bottom of the ribs or the underbelly of the hog (where the bacon comes from). These ribs extend around the belly and connect to the sternum.

A "St. Louis" cut spare rib refers to a style of trimming spare ribs. They are also referred to as "center cut" ribs as they remove the sternum, costal cartilage, and flap in order to effectively square the rack.

In general, spare ribs are more meaty, less tender, and tend to have more flavor due to the extra fat content. In order to break down the collagen (connective tissues), they also need to be smoked longer. For this exact reason, a method like 3-2-1, can work well with spares and do poorly with loin back ribs.

How to Choose Pork Ribs

In an ideal world, every single bone is uniform and the rack is the same size on both ends. There is also minimal bone curvature.

As a backyard cook, these factors don't tend to matter much. Uniformity and lack of curvature may appeal to judges but your family and friends only care if it tastes good.

In general you should look for the following:

  • Avoid "shiners" which is where the meat has been cut too close to the bone. Typically these will fall out in the smoking process.
  • Avoid ribs that are discolored and have dried-out edges.
  • Avoid large fat deposits and look for even fat marbling.

Before choosing a pork rib, it's important to have an understanding of certain terminology that's used to describe pork ribs.

What is a "Slab"?

Pork rib cuts are sold as slabs. Depending on the breed of pig, they will have 15-16 rib bones. However, during the butchering process, 2-3 bones are left in the shoulder and smaller bones may be removed with the discretion of the butcher.

In a grocery store, you should expect to see at least 10 to 13 bones in a slab. If you have a rack with less than 10 bones you have what's known as a "cheater" rack.

Size and Weight

Size and weight of a slab is dependent on several factors like the age and size of the pig. Meaning, you can expect an older hog to have larger, heavier slabs.

These factors are also dependent on how the slabs are processed. Depending on the supplier they will offer ribs based on weights noted as:

  • 1-1/4 to 1-1/2 and down (loin back ribs)
  • 3-1/2 and down (spare ribs)

The above industry jargon refers to loin back ribs that weigh 1-1/4 to 1-1/2 lbs. Where-as 3-1/2 and down refers to spare ribs that weigh 3-1/2 lbs or less.

For spare ribs you can expect weight ranges of:

  • 3-1/2 and down
  • 3 to 5
  • 5 and up

For loin back ribs you can expect weight ranges of:

  • 1-1/4 to 1-1/2
  • 1-3/4 and down
  • 1-3/4 to 2-1/4
  • 2-1/4 and up

Note, while the terminology above for weight is used by a meat supplier, you won't see them in a grocery store.

What to Look for in Spare Ribs

untrimmed pork spare ribs

In order to choose a good spare rib, you want to look for a rack where you can see visible fat marbling throughout.

This is necessary because large isolated fat deposits will render down and leave big chunks missing in your meat. Evenly marbled fat results in evenly flavored meat.

A traditional slab of spare ribs consists of 11+ ribs as well as the brisket bone. A slab of spare ribs will weigh between 2 to 4 lbs or within the weight ranges noted above.

Spare ribs are sold as either whole untrimmed slabs or as a St. Louis cut.

A slab of untrimmed spare ribs will contain part of the sternum (breast bone), costal (rib) cartilage, a flap, and a skirt on the bone side of the meat.

When the sternum, costal cartilage, and skirt are removed you have a St. Louis Style spare rib.

On a per pound basis, Spare ribs cost less than loin back ribs.

What to Look for in Loin-Back Ribs

baby back ribs

Baby back ribs come as a rack that includes 10+ curved bones. These bones are rather uniform in length ranging from 3-6 inches.

In order to pick a good loin-back rib, you should look for even thickness in the rack. Just like spare ribs, you want even fat marbling throughout the rack as apposed to isolated pockets.

Baby back ribs contain less meat and fat, and are more tender than spare ribs.

Rib Preparation

Preparation for both types of ribs is similar. However spare ribs require a bit more effort if you opt to do a St. Louis cut.

Before prepping ribs it's important to understand certain concepts as it relates to the packaging:

What is the "Purge"?

Most ribs are packaged in Cryovac. When ribs or other meat are removed from this packaging, they will have a liquid at the bottom. This liquid is referred to as the "Purge."

It is essentially a combination of water and meat proteins that drain from the meat. Meaning it can also contain the same bacteria that the raw meat can.

For this reason, it's advised that you handle the container that contains the purge with the same care as the raw meat.

You should NOT pour the purge into the sink or rinse the raw meat. It's recommended to throw the purge-laden packaging away and to pat-dry the meat.

The Meat Smells When Removing it from the Packaging

This smell is normal and a result of using cryovac and not an indication of the freshness of the meat. As the meat is exposed to the oxygen, the color will return and the smell should dissipate within 10-15 minutes.

However if the smell continues to linger, the meat is likely spoiled and should be discarded.

How to Prepare Baby Back Ribs

sinew membrane removal

First start by removing the ribs from the packaging. This is done by cutting one end of the cryovac packing open and pulling the rack out.

Don't dump the purge or rinse the meat in the sink. Simply disregard the purge laden packaging in the trash.

You can safely remove the ribs to be placed on your cutting board. You can then pat dry both sides of the rack with a paper towel.

Next remove the sinew membrane from the back of the rack. With the sinew membrane removed you can trim any large fat deposits that may not render evenly.

How to Prepare Spare Ribs

st louis cut ribs

Preparing spare ribs is very similar to loin back ribs. However they require additional trimming.

Start by removing the ribs from the cryovac packaging. Simply cut one end open and pull the rack out.

Again, don't dump the purge or rinse the meat in the sink. Disregard the purge laden packaging in the trash.

Place the spare ribs on a cutting board and pat dry both sides with a paper towel.

The next thing to determine is how you want to cook the ribs. Most people prefer to prepare spare ribs using a St. Louis cut or "center cut ribs." This section is removed in order to square up the slab.

Note: You can also buy St. Louis cut ribs in a grocery store. Spare ribs and St. Louis cut are priced around the same, even though spares weigh more.

The St. Louis cut removes the skirt, the rib tip (brisket, costal cartilage, break, or sternum), and excess flap at the end of the rack.

This results in a rack that's uniform in shape making it easier to both smoke and eat.

Once the rib is squared up, you need to remove the sinew membrane from the back of the rack.

Avoid "Enhanced" Ribs

Enhanced ribs are typically found in grocery stores/supermarkets. Enhanced ribs are essentially ribs that have been injected with a solution of water and other ingredients like salt, phosphates and flavorings.

As you might expect, if you take a salt-based rub and apply it to these ribs, you'll end up with a rib that tastes very salty.

I strongly suggest avoiding these types of ribs and opt to go as fresh as possible. Preferably ribs that have never been frozen, however even still, these are better than enhanced.

Final Thoughts

The next steps of preparation vary based on how you plan to cook/smoke your ribs. However the initial preparation process above is fairly universal.

As you can see there are a number of factors that govern the differences between the two cuts of pork ribs. Namely, the size, weight, and where they're sourced from. However, they can also differ based on how you choose to prepare them for smoking.

Dylan Clay
I've grilled and smoked meat for roughly half my life. While i'm not a professional Pitmaster, I've worked with nearly every cut of meat. Not everyone has a hands on guide to teach them BBQ. It's my hope that Barbecue FAQ can be that helping hand.

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