TY - JOUR
T1 - Structural Relaxation of Salmon Gelatin Films in the Glassy State
AU - Enrione, Javier I.
AU - Sáez, Carlos
AU - López, Daniel
AU - Skurtys, Olivier
AU - Acevedo, Cristian
AU - Osorio, Fernando
AU - MacNaughtan, William
AU - Hill, Sandra
N1 - Funding Information:
Funding Sources Work supported by FONDECYT 11075053; FONDECYT 11090051; PBCT PSD62 from CONICYT; Innova Chile-Corfo CT11 PUT-20 J.I.Enrione(*).C.Sáez.D.López.O.Skurtys.F.Osorio Departamento de Ciencia y Tecnología de los Alimentos, Universidad de Santiago de Chile, Av. Ecuador 3769. Estación Central, Santiago, Chile e-mail: [email protected]
PY - 2012/8
Y1 - 2012/8
N2 - Mechanical relaxation of glassy carbohydrates has been reported extensively in the literature; however, little work is available on protein-based systems. This study deals with the structural relaxation of salmon (Salmo salar) gelatin in the glassy state. Skin gelatin was obtained by an acid-alkaline extraction method. Molecular weight (M w) was determined by capillary viscometry. Films prepared by casting (7% w/v) were equilibrated to a moisture content of ~18. 4% (db). The glass transition temperature (T g) and enthalpic relaxation were determined by differential scanning calorimetry (DSC). Mechanical properties were assessed using a texture analyzer at constant temperature and moisture content. DSC showed a T g ~34°C, and the selected storage temperature (T a) was 29°C (T g - T a = 5°C). The films were aged for 0, 4, 8, 16, and 40 h. Viscometry produced values of M w ~90. 2 kDa. The stress relaxation was modeled by the Kohlrausch-Wlliams-Watts (KWW) equation, reporting an increase in relaxation time (τ 0) as the ageing time increased (τ 0 ~6. 41E + 03 s for 0 h; τ 0 ~9. 01E + 05 s for 40 h). β parameter was smaller for the aged films, indicating a spread of relaxation times. The derivative of KWW equation (dφ/dt) indicated a more rapid relaxation in a fresh sample compared with aged films. DSC showed an excess in enthalpy (ΔH) on the aged samples due to the non-equilibrium state of the matrix. ΔH increased with ageing time with values of ΔH ~2. 42 J/g for the films aged for 40 h. This work demonstrated molecular relaxation process of gelatin in the glassy state, which must be taken into account if this material is used as a structure forming matrix.
AB - Mechanical relaxation of glassy carbohydrates has been reported extensively in the literature; however, little work is available on protein-based systems. This study deals with the structural relaxation of salmon (Salmo salar) gelatin in the glassy state. Skin gelatin was obtained by an acid-alkaline extraction method. Molecular weight (M w) was determined by capillary viscometry. Films prepared by casting (7% w/v) were equilibrated to a moisture content of ~18. 4% (db). The glass transition temperature (T g) and enthalpic relaxation were determined by differential scanning calorimetry (DSC). Mechanical properties were assessed using a texture analyzer at constant temperature and moisture content. DSC showed a T g ~34°C, and the selected storage temperature (T a) was 29°C (T g - T a = 5°C). The films were aged for 0, 4, 8, 16, and 40 h. Viscometry produced values of M w ~90. 2 kDa. The stress relaxation was modeled by the Kohlrausch-Wlliams-Watts (KWW) equation, reporting an increase in relaxation time (τ 0) as the ageing time increased (τ 0 ~6. 41E + 03 s for 0 h; τ 0 ~9. 01E + 05 s for 40 h). β parameter was smaller for the aged films, indicating a spread of relaxation times. The derivative of KWW equation (dφ/dt) indicated a more rapid relaxation in a fresh sample compared with aged films. DSC showed an excess in enthalpy (ΔH) on the aged samples due to the non-equilibrium state of the matrix. ΔH increased with ageing time with values of ΔH ~2. 42 J/g for the films aged for 40 h. This work demonstrated molecular relaxation process of gelatin in the glassy state, which must be taken into account if this material is used as a structure forming matrix.
KW - Enthalpic relaxation
KW - Mechanical relaxation
KW - Salmon gelatin
KW - T
UR - http://www.scopus.com/inward/record.url?scp=84864414941&partnerID=8YFLogxK
U2 - 10.1007/s11947-011-0618-3
DO - 10.1007/s11947-011-0618-3
M3 - Article
AN - SCOPUS:84864414941
SN - 1935-5130
VL - 5
SP - 2446
EP - 2453
JO - Food and Bioprocess Technology
JF - Food and Bioprocess Technology
IS - 6
ER -