Correlations study "structure – property" of model products reaction monosaccharides non-enzymatic coloring in ethanol media

Caramel compositions based on carbohydrates are available food colorants, additionally characterized by a set of practically significant properties, in particular, antioxidant activity. In the present work, the features of the chemical structure of caramels based on the most important monosaccharides – D-glucose, D-mannose and D-galactose, and their correlations with structure-dependent parameters, such as color and reducing capacity, are studied. The syn thesis of target products was performed in water-ethanol media (90% ethanol) in the presence of alkali with thin lay er chromatography (TLC) control and subsequent dialysis. The structural features of the condensed products of the non-enzymatic coloring reaction were studied by Infrared spectroscopy (IS), which were subsequently compared with the values of the reducing capacity expressed by permanganate oxidizability and color estimated by color indices. Qualitative and quantitative analysis of the mid infrared frequency (1800–1000 cm−1) of the initial zero-order spectra and their second derivatives indicates the presence of unsaturated (enolic) fragments (1600 and 1625 cm−1) in the caramel structure. In the spectrum of the D-mannose-based composition, low-frequency shifts of the bands to 1595 and 1620 cm−1 probably indicate a higher degree of enolization. The limiting component of the structure, represent ed by bound polyglycosides, appears in systems based on D-glucose and D-galactose (strengthening of the 1150 cm−1 band). The analysis of the values of structure-dependent parameters shows a decrease in the reducing capacity and color in the series of caramels based on D- mannose > D- glucose > D-galactose. It correlates with the increased con tent of reducing fragments (enols) in the structure of the first system and the excessive presence of bound non-re ducing forms in the structure of the latter, as well as the previously obtained data on the kinetics of caramelization, which forms the basis of the correlation model. Comparison of the reducing capacity and the total color index CI (EBC unit) of the studied products with similar indicators of ascorbic acid and class I food caramels characterizes them with fairly close values of the same order, which suggests further research in the direction of developing and scaling the technology for producing carbohydrate caramels under the described conditions.