Role of water state and mobility on the antiplasticization of green and roasted coffee beans.
J Agric Food Chem
; 59(15): 8265-71, 2011 Aug 10.
Article
en En
| MEDLINE
| ID: mdl-21718028
ABSTRACT
The effect of water on "antiplasticization" and plasticization of green and roasted coffee was studied by textural analysis, sorption isotherms, differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR). From BET monolayer value to a(w) = 0.61 and 0.75 for green and roasted coffee, respectively, the solid matrix hydration occurred and water induced hardening. Very short NMR T(2) values and the concomitant absence of any DSC endothermic peak assignable to water freezing were observed at these a(w) values. When solid matrix hydration was completed, water started to act as a plasticizing agent, the compressive modulus started to decrease, and NMR revealed the appearance of a new proton pool with increased mobility. According to DSC, only when the plasticizing effect became important did water present enough mobility to freeze. Above this moisture value (a(w) = 0.78 and 0.86 for green and roasted coffee, respectively), water determined a decrease of bean hardness and a further decrease of the elastic modulus.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Semillas
/
Agua
/
Culinaria
/
Coffea
Idioma:
En
Revista:
J Agric Food Chem
Año:
2011
Tipo del documento:
Article
País de afiliación:
Italia