The water-soluble constituents of apricot
and peach purees were examined qualitatively and quantitatively before and
after storage for 4 to 16 months at 25 �C and 70 per cent. R.H. All samples
contained all the amino acids, organic acids, sugars, and polyols previously
detected (Reynolds 1967 ; Anet and Reynolds 1955a, 1966b ; Ash and Reynolds
1955a, 1955b) in the two species of fruit.
The stored samples also contained the
following compounds : eleven 1-(N-amino acid)-1-deoxyfructoses, traces of two
2-(N-amino acid)-2-deoxyglucoses, nine by-products of unknown constitution
formed from the reaction between glucose and aspartic acid and glucose and
asparagine, three compounds formed from ammonia and glucose, two series of
sucrose, glucose, and fructose mono-esters of malic acid, traces of a sorbitol
mono-ester of malic acid, and some sugar mono-esters of citric acid.�The
free amino acid or organic acid lost was equal, on a molar basis, to the amino
acid-deoxyfructoses (and related compounds) and sugar esters formed. After
allowing for these derivatives as much as 7 per cent. of the total sugar
(calculated as hexoses) originally present could not be accounted for.
1-Deoxy-1-glycino-D-fructose was obtained
in good yield from the reaction of glycine and glucose in the presence of
sodium bisulphite and 10 per cent. of water. Small quantities of by-products
with similar properties were formed. The results were not affected
qualitatively by the reaction temperature or the presence of salts of
phosphoric or malic acids.
For quantitative studies
deoxyglycinofructose was separated from neutral reducing compounds on a
cation-exchange resin and determined with alkaline ferricyanide.�The
yield of deoxyglycinofructose was dependent on the proportion of glucose and
bisulphite to glycine and decreased as the water content of the mixture was
increased above 10 per cent.
The rate of reaction of glycine and glucose
in the presence of bisulphite was studied over the pH range 3.5-5.6 and the
temperature range 25 to 100 �C. Pseudo first-order rate constants obtained for
pH 3.6 and 4.7 fitted the Arrhenius equation.�The
addition of phosphate at pH 3.6 and malate at pH 3.5 increased the rate of
reaction of glycine and glucose ; the increase was proportional to the square
root of the concentration of dihydrogen phosphate or hydrogen malate ion.
The implications of these results in the
non-enzymic browning of dried fruit are discussed.
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