Evaluation of heat-induced changes and 5-hydroxymethylfurfural formation in mare milk - a comparative study to cow milk

Abstract

Mare milk is known for therapeutic properties due to the presence of bioactive components that are sensitive to thermal treatments and tend to lose their activity. Accordingly, mare milk is consumed raw or frozen, but for food safety reasons recent studies suggest mandatory pasteurization of mare milk before consumption. The aim of this study was to examine the effects of different heat treatments on mare milk quality and compare those to heat induced changes in cow milk. In all milk samples, the total dissolved solids (TDS), electrical conductivity (EC), antioxidant capacity (AC) by the DPPH and FRAP methods, changes in colour (ΔE*), concentration of 5-hydroxymethylfurfural (HMF) and the total phenols (TPC) were determined. Heat induced protein denaturation was monitored by SDS-PAGE, while NIR was applied for qualitative analysis of structural changes. In-bottle sterilization at 116 °C/16ʹ and 120 °C/5ʹ showed to be inappropriate for mare milk processing, since they resulted in the most intense colour changes (ΔE*>5), the highest free and total HMF concentrations (40.70 μmol/L free, 70.26 μmol/L total HMF at 116 °C/16ʹ; 35.49 μmol/L free, 58.12 μmol/L total HMF at 120 °C/5ʹ) and the most intense protein denaturation. On contrary, the applied HTST regimes (72 °C/20”, 85 °C/30”, 90 °C/5ʹ) and thermisation at 63 °C/15” were appropriate for mare milk processing considering the studied qualitative changes. Thereby, the HMF concentration, FRAP, TPC and ΔE* value, combined with NIR analysis showed a good potential to be used as rapid and useful tools for monitoring the intensity of heat induced changes in mare milk.