The average molecular weight of amino acid is ~100 Daltons.
Since the protein content varies depending on the type of meat, I calculated the average amino acid content across the most commonly consumed meat types (beef, chicken, pork, lamb, turkey), which resulted in approx. 24 g of amino acids per 100 g meat.
The number of amino acid molecules in 500 g meat was calculated as following:
$$ n = \frac{m}{M} $$
2. Calculation of the number of amino acid molecules using the Avogadro constant. This
resulted in the following number of amino acid molecules:
$$ \#_{\text {AminoAcidsIn500gMeat}} = n * 6.02 *10^{23} $$
This resulted in the following number of amino acid molecules:
$$ \#_{\text {AminoAcidsIn500gMeat}} = \frac{m}{M} 6.0210^{23} = 7.226*10^{23} $$
Data on amino acid content was manually taken from FoodData Central, a database by the U.S. Department of Agriculture that provides detailed nutrient profile data of common foods (https://fdc.nal.usda.gov/). Only reports from SR Legacy, the Standard Reference Databank, were considered, as these included detailed data about amino acid contents. I chose the data of cooked meat, as the cooking process decreases the water content. However, a larger set of meats would have been needed for a more accurate estimation of amino acid content. Due to the lack of other options, most data chosen were ground meats (see Tab. 1). Ground meats might also not be representative of the average, since the meat used for ground meat tends to be made from less popular cuts of meat, including skeletal tissue, which have usually lower protein contents. Turns out that this simple task might not be so simple, once you go into detail. However, I already spent waaay too much time on this task, so I'll leave it at that.
Summary:
The standard amino acid alphabet (SAAA) likely evolved in two major phases: the first 13 amino acids were established during primordial Earth and the last seven, likely products of the emerging life and metabolism, were gradually added afterwards. The later the amino acid was added, the less codons were available for its embeddedment, which is apparent in the latest additions to the SAAA, Methionine and Tryptophane, both encoded by only one codon. This correlation, as well as several studies on Earth's early environment, indicate that each added amino acid must have provided a significant evolutionary benefit to be embedded into the SAAA.
The fact, that many lifeforms also incorporate amino acids outside of the SAAA into proteins, like selenocysteine and pyrrolysine, (which btw. are considered to be natural amino acids as well) shows that the SAAA might not cover the full property space required for an organism's survival. However these non standard amino acids are included through alternative pathways, since they do not have an "own" aminoacyl-tRNA synthetase (aaRS), like all amino acids from the SAAA. Since the aaRSs for the latest amino acids developed from already present aaRSs, a reason for this might be that physicochemical properties of newer amino acids, albeit complementary to the existing alphabet (thus leading to increased fitness), can not be accomododated for in existing aaRSs, without interfering with their native function.