BROWNING OF SUGAR SOLUTIONS. V. EFFECT OF PH ON THE BROWNING OF TRIOSES^a,b

Abstract

The primary decomposition products of the reducing hexose sugars are generally considered to be glyceraldehyde and its ketoisomer dihydroxyacetone. These two trioses can enolize in alkaline solution to give the 1,2 triose endiol, and it is through this common product that these two compounds are inter-related.Many investigators (1,6,7,11,12,13,16,17) have shown that acetol, methylglyoxal and triose-reductone are produced from glyceraldehyde, dihydroxyacetone and from the hexose sugars. Sattler and Zerban (14) have suggested that glyceraldehyde and dihydroxyacetone are intermediates in the formation of acetol methylglyoxal and triose-reductone. Likewise it has been suggested by Zerban and Sattler (18,19) and by Enders (5) that methylglyoxal, acetol and triose-reductone have a role in the darkening (browning) of hexose and triose sugars. It would appear that the pH of sugar solutions has a pronounced effect on the production of these carbonyls. It has been shown by Meyerhoff and Lohmann .(ll) and Thornton and Speck (16) that in acid solution methylglyoxal is formed from dihydroxyacetone and by Nodzu et al (11) and Prey et al (13) that acetol, and by Bauer and Teed (2) and Weygand (17) that triose-reductone are formed in alkaline solutions. These findings together with work done at this laboratory (8) suggest that browning (caramelization) of hexose and triose sugars proceed through the intermediate formation of methylglyoxal, acetol and triose-reductone depending upon the pH of the solution.This study was undertaken to obtain a better understanding of the intermediates formed in the browning of the trioses, dihydroxyacetone and glyceraldehyde, in solutions of pH 4 to 11. EXPERIMENTAL

Factors affecting the formation of pyrazine compounds in sugar-amine reactions

“…Lento et al (1960a) studied the formation of some 3-carbon carbonyl compounds from glucose and fructose heated in buffer solutions. It was suggested (Lento et al, 1960b) that acetol (hydroxyacetone) might be an important intermediate in the browning reaction at high pH levels. When used as the carbon source in the model system reaction study, the 3-carbon compound, hydroxyacetone, produced only dimethylpyrazine, as might be predicted (Table III).…”

Pyrazines in foods

“…For example, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, and 2-ethyl-3-methylpyrazine eluted close succession from a 10 ft x 1/8 in. Buttery et al, 1969bFerretti and Flanagan, 1971a,b Kinlinetal., 1972Ferretti and Flanagan, 1972van Praag, 1968Walradt et al, 1970Johnson et al, 1971Wang and Odell, 1972Walradt et al, 1970Liebich et al, 1972Liebich et al, 1972Sizer and Maga, 1972Viani et al, 1965Vianiet al, 1965Murray et al, 1970Collins, 1971Collins, 1971Manley and Fagerson, 1970Manley and Fagerson, 1970 1 8 16 FIGURE 6. Basic pyrazine fraction GLC capillary column separation:…”

“…Glycerol only gave small amounts of the unsubstituted, mono-, and disubstituted pyrazines, whereas propionaldehyde and asparagine produced no detectable pyrazines. In an earlier study Lento et al (1960) had predicted that the three-carbon unit hydroxyacetone could be an important browning intermediate especially under basic conditions. Thus, when Koehler and Odell (1970) reacted hydroxyacetone with asparagine, a high yield of the predicted compound dimethylpyrazine was found.…”

“…In another study dealing with flavor in meats Liebich et al (1972) analyzed the total flavor extract from roast beef and its drippings. No attempt was made to fractionate the extract into acidic and basic portions.…”

Dihydroxyacetone: A User Guide for a Challenging Bio-Based Synthon

“…Some papers have reported the production of acetol (monohydroxyacetone) subsequent to the production of MGO [ 157 , 158 ]. To our knowledge, no further evidence is presented in the literature to clarify the reaction pathway for acetol production; it could be produced directly from MGO as reported, but it could also come from earlier reaction intermediates, as both papers deal with reactions on hexose sugars systems, or from additional rearrangements after MGO production.…”