CULINARY & HOSPITALITY: Fish Sauce & Umami

What I learned from the Curtis paper about Umami and Fish Sauces (Notes and excerpts):

Umami  appears to have been derived from glutamic acid and 2 ribonucleotides, 5′-inosinate and 5′-guanylate  
Foods mentioned:
meats (pork, chicken and beef)
fruits (grapes,apples)
vegetables (carrots, mushrooms, cabbage, asparagus, peas, and onions)
seafood (sardines, mackerel, tuna, oysters, and prawns)
processed foods: cheese, fish sauce, and soy sauce

Fish sauce seems to be fish plus salt and time to ferment. 
Use small fish (sardines and anchovy) and/or viscera of larger fish (tuna, mackerel)
May have a clear, reddish brown or amber color.
Best sauces have robust, though not offensive, odor.

Roman Fish Sauces
Garum: hydrolysis of small whole fish or fish innards in the presence of salt through natural fermentation over several months.
Allec: The undissolved fish material remaining from garum production.
Muria: Salty solution that resulted from osmosis during the salting of whole, gutted fish or slices of fish meat (salsamentum). 
 Liquamen: sesult of subsequent washings of allec with a salty solution, closely related to garum. In late antiquity the term liquamen effectively replaced garum as the generic word for fish sauce.

Romans placed into a vat small fish, particularly anchovies, sardines, and mackerel, 
and added salt at prescribed ratios and sometimes various herbs, spices, or wine. 
They used weights to press down on the concoction, covered it, and allowed it to remain in the sun for several months. 
At the end of this time, they withdrew the liquid garum by using a basket, filtered it, and placed it in a terracotta transport vessel, or amphora. 

Asian/Oriental fish sauce (prepared in a similar way)
Producers place fish (whole fish, usually anchovies) into a terracotta vessel, barrel, or concrete vat small, 
mix the fish with salt in a specified ratio that can vary but is usually Fish to salt  ≤5:1. 
Place weights on the mixture, cover the vat, and allow fermentation to continue for up to a year or more. 
They then remove the liquid sauce by ladling or draining from a conduit at the bottom of the vat. 
Once filtered, they place the sauce into bottles. 
Often wash the residue with a hot, salty liquid and allow it to ferment before extracting a second-quality sauce. 

Modern Fish Sauces
Solutions of >20% salt and whole, uneviscerated, usually pelagic fish (coastal and oceanic fish), especially anchovies.
Eventually, the fish loses its shape and begins to liquefy as proteins decompose into amino-nitrogen compounds, notably amino acids, oligopeptides, and nitrogenous bases. 
Because enzymic hydrolysis is not total, an insoluble residue remains.
The quality of the final product depends on limiting the growth of microorganisms. 

Bacterial spoilage creates a stronger smelling sauce which is considered to be of poorer quality. 
fish-to-salt ratio of ≤5:1 and a relatively low pH of 5.0–6.5, common in the best fish sauces, are not conducive to the growth of bacteria. 

The dominant free amino acid in fish sauce is glutamate, which is present at a concentration of ≈1300 mg/100 mL fish sauce. 
As such, it has one of the highest free glutamate contents of any food, similar to that of parmesan cheese.