Freeze − thaw induced structuration of whey protein − alfalfa (Medicago sativa L.) galactomannan binary systems

Authors

Hellebois T., Gaiani C., Soukoulis C.

Reference

Food Hydrocolloids, vol. 125, art. no. 107389, 2022

Description

The cryotropic gelation of food biopolymers is an alternative method to impart bespoke structural, textural, and functional characteristics to food colloids. The present work aims to explore the structuring performance of whey protein isolate (WPI) in the presence of alfalfa (Medicago sativa L.) galactomannan (AAG) under cryogenic processing. Aqueous WPI solutions (10% wt.) fortified with AAG (0–1% wt.) were subjected to five consecutive freeze – thaw cycles from 25 to −28 °C with an isothermal hold at −28 °C for 20 h. The development of the elastic modulus G′ in the WPI – AAG solutions was monitored throughout the cryogenic processing, and the cryogels obtained were characterised rheologically, structurally and physically. The addition of AAG in heat-treated WPI solutions induced an extensive microscopic phase separation, which was driven via a depletion – flocculation mechanism. Cryostructuration was governed by WPI, whilst AAG modulated the development of the microstructural features, the rheological behaviour and the stability of the cryogels when confronted with spontaneous and forced syneresis phenomena. It was postulated that the mechanisms of action of AAG were associated primarily with its ability to enhance the macroviscosity of the unfrozen water phase controlling the ripening of ice crystals (porogens) during the freezing step, and secondarily to its direct contribution via the partially structured hydrogel segments interpenetrating the formed protein network. Since the extent of phase separation eminently affected the cryogelation process, it was suggested that the use of at least 0.75% wt. of AAG was required in order to enhance the structural, rheological and physical stability of the WPI cryogels.

Link

doi:10.1016/j.foodhyd.2021.107389