Assessment of agave fructans as lyoprotectants of bovine plasma proteins concentrated by ultrafiltration

Abstract

The effectiveness of fructans as protectant agent to prevent protein denaturation was evaluated during freeze-drying and storage. Native agave fructans and two fractions obtained by ultrafiltration were assessed as protective agents. Since the protein denaturation during freeze-drying can alter the functional properties of proteins, the evaluation of bovine plasma protein properties was performed with different concentration of fructans, pH and freezing temperatures. The results showed that the incorporation of fructans as lyoprotectants improved functional properties, due to the reduction of protein denaturation with maximum stabilization of plasma bovine protein at a fructan concentration between 5% and 10% (w/v) for native fructans and 10% (w/v) for the fractions of fructans at - 40. °C. Moreover, when freezing at - 4. °C, fructans fraction at 15% (w/v) prevented protein denaturation while native fructans exerted no acceptable protection (P<. 0.001). This behavior could be explained by a microstructure study of fructans, where the higher heterogeneity in size of native fructans may be the reason for the lower protective effect. Furthermore, the higher heterogeneity of the samples affected the extent of non-enzymatic browning in the range of the temperatures assessed. The shelf life of freeze-dried proteins was improved from 1.7. months for the control sample to 7-11, depending on the saccharide considered. Taking into account the health benefits of fructans, since they are categorized as prebiotic, the protein-saccharide mixture may be valuable functional ingredients for food formulations.