Effect of various acids on physicochemical and functional characteristics of gelatin from swim bladder of rohu (Labeo rohita).

Influence of various acids (acetic acid, phosphoric
acid, and propionic acid) at different concentrations
(0.05, 0.1, and 0.2 M) on the extraction yield,
physicochemical and functional properties of gelatin from
Labeo rohita swim bladder were investigated. Highest
gelatin yield (44.22%, dry weight basis) was obtained in a
sample prepared by without acid pretreatment (GWA) of
swim bladder as compared to acid pretreatment counterparts.
Amongst the acid pretreatments, propionic acid
(GPrA) showed the highest gelatin yield, followed by
acetic acid (GAA) and phosphoric acid (GPA) at all
concentrations used, respectively. Moreover, with
increased concentrations of all acids, the decrease in
gelatin yield was observed for all the acids. GWA showed
higher protein and hydroxyproline content than that of
acid counterparts (P\0.05). Amino acid analysis of
gelatins showed glycine as the major amino acid in all
gelatins followed by proline, glutamic acid and alanine,
respectively. GWA showed a (a1 and a2) and b-chains as
the predominant components with low molecular weight
peptides. However, GPrA, GAA, and GPA had a1 and a2
dominant constituents. FTIR spectra of gelatins revealed
that the loss of the triple-helix was found in GPA, GAA,
and GPrA, compared to GWA. Among gelatin samples,
GWA showed the highest solubility at all pH tested followed
by GPrA, GPA, and GAA respectively. Furthermore,
GWA exhibited higher emulsifying, foaming and
gelling properties as compared to GPrA, GPA, and GAA,
respectively. Therefore, the acid pretreatment of swim
bladder had a negative impact on the extraction yield,
physicochemical and functional properties of gelatin from
rohu swim bladder.