Cryostabilization mechanism of fish muscle proteins by maltodextrins

Maltodextrins of varying mean molecular weights (MW) were evaluated for cryoprotective ability in Alaska pollock surimi (leached mince) versus sucrose or a sucrose-sorbitol mixture. Treatments were stored either isothermally at -8, -14, or - 20 degrees C for 3 months or freeze-thaw (F/T) cycled six times to induce freeze-related protein denaturation, measured as a decrease in myosin Ca+2 ATPase activity and change in heat-induced gel-forming ability. Results indicated good cryoprotection by all maltodextrins at -20 degrees C isothermal storage irrespective of MW, but poor cryoprotection by higher MW maltodextrins at higher isothermal storage temperatures or after F/T cycling. These observations, and surface tension measurements of maltodextrin solutions, indicated that lower MW maltodextrins likely cryoprotect by a preferential solute exclusion mechanism, similar to sucrose and sorbitol. Higher MW maltodextrins presumably cryoprotect at lower storage temperatures via a reduced water mobility mechanism. As the MW of maltodextrins increased the gelling ability of the surimi was increasingly impaired, such that evidence of cryoprotection from gelation data was obscured. (C) 1999 Academic Press.