Effects of Freeze–Thaw Cycles on the Structures and Functional Properties of Clitocybe squamulosa Protein Isolates

Abstract

Changes in the functional properties and structures of Clitocybe squamulosa protein isolate (CSPI) in the process of freeze–thaw (F–T) cycles were explored. Remarkable alterations and the reduced content of protein ordered structure were revealed through structural analysis of CSPI after F–T treatments. The surface hydrophobicity and free sulfhydryl content of CSPI first increased and then decreased. However, after the F–T treatments, the carbonyl content of CSPI continued to increase. Similarly, the water holding capacity (WHC), oil holding capacity (OHC), and solubility of CSPI all declined as the number of F–T cycles increased. The foaming properties and emulsifying properties of CSPI were significantly improved and reached maximum values after three F–T cycles. CSPI undergoing two F–T cycles showed the highest digestibility, maximum polypeptide content, and highest DPPH and ·OH-radical-scavenging activities. The ·OH-radical-scavenging activities and reducing power of the gastrointestinally digested CSPI had the highest value after one F–T cycle. Therefore, it has been demonstrated that F–T treatments could be a residue-free and cost-effective tool for improving mushroom protein functional properties.