Can I contribute (with an over-simplification) please?
Amino acid - responsible for smell/scent and taste.
Essential amino acid - one the animal can only acquire through their diet.
(Fish have a requirement for 10 different essential amino acids)
To attempt to demystify what amino acids are and their role in baits (food stuff), its first important for us to realise that ALL raw and unprocessed food contains amino acids that can potentially attract fish, they are simply the building blocks of proteins, their mystery lies in understanding how they work and why fish find them so attractive. A subject of great debate amongst course anglers.
Imagine a string of beads, and each bead is held together tightly by the string. Its that string of beads that makes up a protein (Polypeptides and proteins are chains of amino acids held together by peptide bonds). The beads (peptide bonds) are the protein building blocks, break that bond and you release amino acids some of which have a slight negative charge and some positive and others neutral. Other categories relate to polarity, pH level ect.
The positive charge is generally what excites the fishes senses as they come into contact with them (L-amino types), some have no effect and some are repulsive.
When they are whole and complete they are simply too big a protein with little or no smell. Break them apart by pulverising, mashing, crushing chopping up and they release their flavours (amino acids), solubility being the key.
When anglers talk about amino acids many immediately assume they're only important or relevant if your a carp angler for some reason, but what's so special about carp?
Carp will eat almost anything that looks edible, there's nothing so unique about carp when it comes to fish anatomy - all fish will be attracted to smells and scents in the water to some extent, its the amino acids that are responsible for those smells the exact same smell us lesser mortals might be able to pick up on in the air we breathe all around us.
In order for amino acids to be effective as an additive for inclusion with our baits, they need to be soluble before they can be picked up by the fishes senses and they need to be of the right type.
Many amino acids are not soluble and a soup of amino acids doesn't necessarily make it better either, sometimes it causes confusion and is overpowering for the fishes receptors especially the so called; "nature identical" man-made artificial additives or any combination that is incompatible with each other.
If anyone's confused then your not alone; even scientist cannot always agree and applying their research to angling comes with its own complications.
If I was to give one take it or leave it piece of advice I would suggest; using a SINGLE natural water-soluble liquid such as molasses, CSL (corn steep liqueur), or solids like powdered seaweed, live yeast or any predigested foods/liquids that have been converted by natural enzyme processes - bruised and ripened fruit, bread (from the action of yeast), milk proteins (from the actions of bacteria) ect. these foods are microscopically tiny and have an abundance of soluble amino acids present.
I have learned that no single food item (which includes many we use for bait) is complete. "Man cannot live by bread alone"! its for this reason all living creatures need to eat a variety of different food stuff that contain the right amount of nutrients and amino acids essential for life. It may also be the reason why even the best bait in the world may not catch all the time and why we need to keep changing the hookbait?
