You could also simply use a diluted mixture of Bromelain, which is the enzyme in the pineapple that causes the tenderizing. It is quite available online and is used in many of the available meat tenderizers you would get at the grocery store. This way you don't get the pineapple flavor...
I would try injecting immediately before smoking. For more information on Bromelain see below.
bromelain, a natural mixture of two
proteases (protein-digesting enzymes) found in pineapples. They discovered that bromelain is quite effective at dividing proteins such as the collagen in meat.
Although bromelain is found in every part of the pineapple, it's most plentiful in the stem. Most commercially grown pineapple is sliced, canned or juiced. The remains are rich with this corrosive substance, which is then extracted.
Bromelain works in these capacities due to its ability to separate
amino acids. Amino acids are organic compounds within living cells. Amino acids join by forming
peptide bonds, a link that connects one amino acid's amino group with the carboxyl group of another amino acid. When amino acids join through peptide bonds, they form proteins. These proteins then carry out numerous functions in the structure and operation of
cells, tissues and organs.
The compound separates the all-important peptide bonds that link the proteins in collagen. Since the collagen gives the
muscle tissue its shape, once it's broken down, the muscle tissue begins losing firmness. If you left meat for a day or two covered with bromelain, it would be noticeably mushy, so much so that you wouldn't want to eat it. When used shortly before cooking, however, bromelain efficiently softens the steak for chewing, but leaves it firm enough to enjoy its taste. The enzymes are neutralized by heat of about 158 degrees Fahrenheit (70 degrees Celsius), so they stop working once cooked.
