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Improving gelation properties of fish gelatin by nonthermal processes

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2019
Sezer, Pürlen
Gelatin is mostly obtained from skin, bone or connective tissues of bovine or porcine land animals. Gelatin is commonly used in confectionery products as the main gelling agent and as a hydrocolloid and stabilizer in liquid food systems. Due to religious preferences, helal gelatin has started to be very common in Middle Eastern countries and bovine gelatin is mainly utilized for that purpose. Gelatin could also be obtained from fish which is very abundant in nature however it has weak gelation ability. There are different studies in the literature that explored the gelation ability of fish gelatin by adding additional substances as CaCl2 or other hydrocolloids. In this research, it is hypothesized that fish gelatin could be modified by using processing techniques as High Hydrostatic Pressure (HHP) and ultrasonication (US). HHP was applied at 400 MPa, at two different temperatures (10o C and 30o C) by keeping process time constant at 15 minutes. Ultrasonication experiments were conducted at 24 kHz at two different amplitudes (100% and 60%) for 5 and 10 minutes. In order to compare the gelation abilities of the fish gelatin, bovine gelatin is used as a commercial gelatin type. The results showed that HHP treatment on fish and bovine gelatin could stabilize gelatin network by organizing the structure and reduce free volume. Furthermore, US treatment could destroy gelatin network, change gelation mechanism and decrease the degree of aggregation. NMR spectroscopy vi measurements were useful to monitor change in protein structures and intramolecular forces between protein and water molecules. Gelation properties and hydration of gelatins were identified by using T1 and T2 values. When the T2 results of fish and bovine gelatin were compared, it concluded that the free water of fish gelatin was higher than bovine. Moreover, gelation capability of the bovine gelatin was higher than fish gelatin. In order to estimate the change in the amino acid structure of the gelatin after HHP and US treatments, FTIR measurements were used. FTIR results indicated that the secondary structure of the amino acids was rearranged after treatments.