4/3/2023 0 Comments Bovine gelatinPapain was used to extract gelatin from rawhide splits but the obtained gelatin showed low gel strength and viscosity (Damrongsakkul, Ratanathammapan, Komolpis, & Tanthapanichakoon, 2008). Pepsin and proctase (isolated from Aspergillus niger) were used to extract the gelatin from bovine skin but the gelatin yield, its gel strengths and viscosities were low (Chomarat, Robert, Seris, & Kern, 1994). Previously, to improve the gelatin extractability, some proteases capable of breaking the collagen cross-links have been used (Nalinanon et al., 2008). The molecular bonds present in the collagen are stable to thermal and acid treatment (Galea, Dalrymple, Kuypers, & Blakeley, 2000) resulting in a low gelatin yield (Nalinanon, Benjakul, Visessanguan, & Kishimura, 2008). Therefore, the recovered gelatin has lower molecular weight components than native collagen and comprises of a mixture of polypeptide fragments having molecular weight in the range of 16–150 kDa (Asghar & Henrickson, 1982). Apart from this, hydrolysis of some amide bonds present in the collagen molecules take place (Bailey, 1985). Cleavage of covalent and non-covalent bonds in sufficient numbers releases free α-chains and oligomers (Johnston-Banks, 1990). Finally, conversion into gelatin takes place during extraction process due to the cleavage of hydrogen and covalent bonds by heat leading to helix-to-coil transition (Djabourov, Lechaire, & Gaill, 1993). Insoluble collagen is required to be converted into soluble form by pretreatment with either acid or alkali resulting in the loss of the ordered structure of native collagen which is swollen but still insoluble (Stainsby, 1987). Gelatin is a high molecular weight biopolymer derived from collagen by thermal denaturation. Finally, it was concluded that the ultrasound assisted gelatin extraction using bromelain enzyme produced high yield with good quality gelatin. Longer duration of ultrasonic treatment resulted in denser, irregular, disorganized and more interconnected structure with increased porosity as revealed by scanning electron microscopy (SEM) but structural integrity was retained in UBC indicating degradation effect of bromelain enzyme in other samples. As demonstrated by Fourier transform infrared (FTIR) spectroscopy, amide I band of gelatins extracted by ultrasound treatment exhibited higher wavenumbers than the commercial gelatin (CG) suggesting greater loss of molecular order in these samples. Protein pattern of the gelatin samples showed the progressive degradation of polypeptide chains as the time duration of ultrasound extraction increased. The amino acids content increased with longer duration of ultrasonic treatment and UBC exhibited the highest content of the glycine (27.06%) and hydroxyproline (17.21%) compared to other samples. The corresponding values for UB6 were 595.51 g and 16.37 mPa s, respectively. Gel strength and viscosity of UBC were 603.24 g and 16.33 mPa s, respectively. Gelatin yield increased significantly (P < 0.05) as the time duration of ultrasound treatment increased with UB6 giving the highest yield of 19.71% followed by UBC (18.67%). Control (UBC) gelatin was extracted using ultrasound for 6 h at 60 ☌ without enzymatic pretreatment. Bovine skin was pretreated with bromelain enzyme and ultrasound (53 kHz and 500 W) was used to extract gelatin for the time durations of 2, 4 and 6 h at 60 ☌ (samples were referred as UB2, UB4 and UB6, respectively).
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