Food Biochemistry and Food Processing (2 edition)

BLBS102-c21 BLBS102-Simpson March 21, 2012 13:39 Trim: 276mm X 219mm Printer Name: Yet to Come

21 Fish Gelatin 397

Figure 21.4.Impact of endogenous protease associated with fish skin on degradation of gelatin molecules.

strength was noticeable when extraction temperature of 75◦C

was used for extraction of gelatin from the skin of both sharks

(Kittiphattanabawon et al. 2010).

Emulsifying and Foaming Properties

Emulsions and foams are heterogeneous systems consisting of

one phase dispersed in another. An emulsion is a dispersion or

suspension of two immiscible liquids, while a foam is a gas

phase dispersed in liquid (Hill 1998). Proteins extracted from

the different natural sources, for example, soy, milk, fish, meat,

and plant, can be used as the emulsifier or foaming agents be-

cause of their ability to facilitate the formation and improve

the stability of emulsion or foam (Surh et al. 2006). Gelatin is

surface-active and is capable of acting as an emulsifier in oil-in-

water emulsions and foaming agent (Lobo 2002, Cho et al. 2004,

Surh et al. 2006, Aewsiri et al. 2008, Binsi et al. 2009, Kwak

et al. 2009, Aewsiri et al. 2009a, Jongjareonrak et al. 2010).

The hydrophobic areas on the peptide chain are responsible for

giving gelatin its emulsifying and foaming properties (Galazka

et al. 1999, Cole 2000). Gelatin concentration has an impact on

interfacial properties, but these properties are also governed by

the source of the raw material.

Aewsiri et al. (2008) reported that the higher emulsifying and

foaming properties were observed in gelatin from precooked

tuna fin when the concentration of gelatin was increased. In

contrast, the emulsifying capacity of gelatin from bigeye snap-

per (Priacanthus hamrur) decreased with increasing gelatin

concentration (Binsi et al. 2009). Additionally, Aewsiri et al.

(2009a) studied the emulsifying properties, emulsion activity

index (EAI) and emulsion stability index (ESI), and foaming

properties, foam expansion (FE) and foam stability (FS) of

gelatin from cuttlefish skin with and without bleaching using

hydrogen peroxide (H 2 O 2 ). Emulsions containing gelatin from

bleached dorsal and ventral skin were more stable than those of

gelatin without bleaching. A longer bleaching time and higher

H 2 O 2 concentration led to a lower ESI of gelatin for all samples,

except for gelatin from dorsal skin in which the highest ESI was

obtained when the skin was bleached with 5% H 2 O 2 for 48 hours

(p<0.05). Surh et al. (2006) found that the oil-in-water emulsion

prepared with high-molecular weight fish gelatin (∼120 kDa)

was more stable than that prepared with low-molecular weight

fish gelatin (∼50 kDa). For foam-forming ability, gelatin from

unbleached skin, both dorsal and ventral, had a slightly lower

FE than gelatin extracted from bleached skin, while bleaching

had no effect on the FS of gelatin from ventral skin, but gelatin

from dorsal skin bleached with 5% H 2 O 2 for 48 hours showed

the highest FS (Aewsiri et al. 2009a). Jongjareonrak et al. (2010)

reported that foam capacity and foam stability of gelatin from

farmed giant catfish were higher than that from calfskin. Gelatin

from shark cartilage and precooked tuna fin showed lower foam

capacity and foam stability than gelatin from porcine skin (Cho

et al. 2004, Aewsiri et al. 2008).

Film formation

Film and coating from biopolymers such as proteins and polysac-

charides have been receiving increasing attention since synthetic

packaging films have led to serious ecological problems because

of their nonbiodegradability. Proteins are important biopolymers

possessing good film-forming ability (Benjakul et al. 2008).

Moreover, their mechanical and barrier properties are generally

superior to polysaccharide-based films (Cuq et al. 1998). Among

all proteins, gelatin has attracted the attention for the develop-

ment of edible films due to its abundance, biodegradability, and

excellent film-forming properties (Gennadios et al. 1994, Bigi

et al. 2002). Thus, it is one of the first materials applied to edible

coatings and films. The main parameters affecting film-forming

properties of gelatin are the source of raw material, extraction

method, molecular weight, film preparation method, and degree

of hydration or type and level of plasticizer used (Jongjareonrak

et al. 2006a, 2006b).

Gimenez et al. (2009) suggested that giant squid gelatin ob- ́

tained from pepsin aid process during the swelling step showed

good film-forming properties. Its puncture force, puncture de-

formation, and water permeability were 4.94 N, 46%, and