Reaction E Strecker Degradation

This is a reaction of a-amino acids, in which they are oxidised to the corresponding aldehyde, giving off carbon dioxide, and ammonia is transferred to other components of the system, very little being liberated as such. The reaction is initiated by compounds, such as a-dicarbonyl compounds and their vinylogues, or compounds which can give rise to them readily, such as reductones by dehydrogenation or imino analogues by hydrolysis. The reaction may therefore be represented as follows  

Studies with radioactive carbon have shown that well over 80% of the carbon dioxide liberated in the Maillard reaction does indeed originate from the amino acid, somewhat less than 10% coming from uniformly labelled glucose.62 

The reaction is named after Strecker,63 who reacted a-amino acids with alloxan, obtaining C02 and the purple murexide. The reaction was reviewed by Schonberg and Moubacher,64 its contribution to food flavour being covered by Rizzi.65 

Dehydroascorbic acid (but see later) and quinones, such as vitamin K and those formed enzymically from polyphenols, can also act as dicarbonyl compound in the reaction. 

It is known that in fish, two less commonly occurring amino acids are major contributors to the browning reaction and to the loss of free sugar, i.e., anserine, a dipeptide, /i- a I a n y l-i-mctliyl liistidinc, and taurine, H3N+.CH2.CH2.S03 . Discoloration of fish at 0% r.h. in sunlight has been shown to be due to 1-methylhistidine without the 

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