Pork rib cuts are sourced from two different parts of the pig and are known as Spare Ribs (including St. Louis cut) and Baby Back Ribs.
Aside from anatomical location on the pig, there are a number of nuances that are worth discussing.
Back ribs are taken from the upper portion of the rib cage, where the rib and spine meet; The meat comes from the loin.
"Baby back" both implies where they're sourced from and their smaller size in comparison to spare ribs.
Spare ribs are taken from the bottom of the ribs or the underbelly of the hog (where pork belly and bacon comes from). They extend around the belly and connect to the sternum.
In general, spares 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.
The same could be said for different types of smokers and their affect on ribs. For instance, spare ribs cook much differently on my PBC than baby back ribs.
A "St. Louis" cut refers to a style of trimming spare ribs.
They are also referred to as "center cut" as they remove the sternum, costal cartilage, and flap in order to effectively square the rack.
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:
Before choosing a pork rib, it's important to have an understanding of certain terminology that's used to describe pork ribs.
Pork rib cuts are sold as slabs or racks.
Depending on the breed of pig, they will have 15-16 rib bones in a rack. 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 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:
The above industry jargon refers to baby backs 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:
For loin ribs you can expect weight ranges of:
Note, while the terminology above for weight is used by a meat supplier, you won't see them in a grocery store.
In every case, baby backs will cost more per pound. This is due large in part to how they're marketed.
For example, most people have heard of "Chili's baby back ribs!"
Where-as spares are more popular among folks who do barbecue. They contain more fat, and consequently, tend to be more flavorful.
Just to illustrate, a common place I buy meat from online is Wild Fork Foods. As of updating this article - 11/3/2022 - the prices are as follows;
Those prices are about what you'll pay at a grocery store and it makes sense too. Baby backs contain loin meat, which is quite desirable, and they're marketed better.
Just a quick side-note. While I like beef ribs more than I like pork ribs, they also cost 2-5x more; Beef plate short ribs from wild fork foods are $11.78/lb.
Whole spare ribs are less butchered than St. Louis cut and cost less per pound. Where-as St. Louis cut include additional trimming and contain less meat (which you may waste).
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 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 full slab of spares will weigh between 3.5 to 5 lbs+ or within the weight ranges noted above.
At a BBQ joint, half racks of spares will be sold based on weight, rather than the number of ribs on a bone.
Spare ribs are sold as either whole untrimmed slabs or as a St. Louis cut.
A slab of untrimmed spares will contain part of the sternum (breast bone), costal (rib) cartilage, a flap, and a skirt on the bone side of the meat.
Loin 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 spares, 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.
Preparation for both types of ribs is similar. However, spares 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:
Most slabs are sold in a vacuum package like Cryovac. When meat is removed from this packaging, it 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.
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.
First start by removing the meat from the packaging. This is done by cutting one end of the cryovac packing open and pulling the rack out.
Don't rinse the meat in the sink or dump the purge down the drain; Simply disregard the purge laden packaging in the trash.
You can then pat dry both sides of the rack with a paper towel.
For visual learners, here's a quick video I recorded on the membrane removal:
Start by removing the rack 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 rack on a cutting board and pat dry both sides with a paper towel.
The next thing to determine if you want to trim the meat. Most people prefer a St. Louis cut; The meat is trimmed to square up the rack.
Note: You can also buy St. Louis cut ribs in a grocery store.
The St. Louis cut or "center cut" spare ribs removes the skirt, the brisket bone, and flap meat. This results in a rack that's uniform in shape making it easier to both smoke and eat.
If you're after a more detailed guide on this concept, you can learn how to trim spare ribs to a St. Louis cut by reading this article.
Once the rack is squared up, you need to remove the sinew membrane from the back of the rack.
Enhanced ribs are typically found in grocery stores/supermarkets. Enhanced simply means that the meat was 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 the meat, you'll end up with a rib that tastes very salty.
I strongly suggest avoiding enhanced meat and opt to go as fresh as possible. Preferably ribs that have never been frozen, however even still, frozen is far better than enhanced.
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.
My preference are baby backs.