Redox Power Changes of Caramels and Sugar Reductones in Beer

Aerated or nitrogenated solutions of various sugars (10 % w/w) in deionized water, brewing water or phosphate buffers with dichlorophenolindophenol (DCIP) addition (10 mg/l) were heated 45 min at 60 °C and absorbance at 520 nm (?max of DCIP at pH 4.6) and 610 nm (?max of DCIP at pH >6) was measured. Reduction power of the solutions increased with the absence of oxygen, increasing pH value and the kind of sugar (FRU>LAC,MAL,GLU>SUC). Aerated solutions of various sugars were also autoclaved (10 min at 121 °C) and the absorbance at 420 nm was measured. The color of caramels from sugars was dependent on the kind of sugar (FRU> LAC,MAL,GLU>SUC), and it increased with increasing pH value. The formation of caramel pigments from ascorbic acid or maltose by oxidation with potassium peroxodisulfate or hydrogen peroxide was also compared. The formation of colored pigments is considered to be the mark of irreversible aging of food.