Conversion of Avian Collagen to Gelatin and Cryoprotective Peptides

• Author / Creator

  Du, Lihui

• Gelatin - a gel-forming, multifunctional biopolymer obtained from the processing of collagen - has long been used in the food industry. Gelatin hydrolysates obtained by enzymatic hydrolysis have various bioactivities. Although porcine and bovine sources are principally used for commercial gelatin production, the demand for gelatin derived from alternative sources is increasing mainly due to the religious, ethical, sustainability, as well as health and safety reasons. Therefore, in this research underutilized poultry by-products were developed as a potential source for gelatin and collagen production. In the first study, gelatins were extracted from chicken and turkey heads with optimized pre-treatment and extraction methods at 50 °C and 60 °C, and their physicochemical properties (amino acid composition, molecular weight, microstructure, rheological behavior, Bloom strength) and functionalities (solubility, emulsifying and foaming properties) were examined. All the obtained poultry gelatins exhibited an excellent Bloom greater than 200 g, and the gelatin achieved from turkey heads at 50 °C showed superior gel attributes with a Bloom of 368±8 g. Except for source of collagen, the manufacturing method mostly affects both the physicochemical and functional properties of gelatin. Traditional gelatin production involves a time and energy intensive pre-treatment step, with the enormous consumption of water and chemical reagents. Therefore, in the second study, a new, efficient and environmental-friendly pre-treatment approach was developed for gelatin extraction from mechanically separated turkey meat (MSTM) using an isoelectric solubilization/precipitation process (ISP). The resulting gel had an improved quality (bloom strength 353.2 g) compared to the gel made by the conventional manufacturing procedures. The first part of the research demonstrated the possibility of using poultry by-products as an alternative gelatin source; here the features of these poultry gelatins were comparable to those from porcine or bovine sources. However, the lower yields of this process may represent a limitation in commercializing these poultry gelatins. To maximize the value of gelatin or collagen obtained from poultry by-products, collagen produced from chicken skin was hydrolyzed by trypsin, and then the cryoprotective effect of these collagen hydrolysates was evaluated in different food systems with two studies. Firstly, the ice growth inhibition activities of collagen peptides were determined in a sucrose model system as compared to natural antifreeze proteins (AFPs). The ice crystal dimension in the model systems was evaluated under a microscope after thermal cycles, and the amino acid sequences of several ice-controlling peptides were identified. The addition of certain collagen peptides at 1 mg/mL effectively reduced approximately 67% of ice crystal growth in the sucrose systems, in a similar manner as do AFPs. In the second study, the cryoprotective effect of collagen hydrolysates against freeze-denaturation of actomyosin systems was investigated in relation to the ice-controlling activity. Smaller ice crystals induced by collagen hydrolysates may decrease protein unfolding, oxidation and functionality loss during frozen storage. Overall, this thesis provides a research foundation for producing high-quality gelatin from poultry sources. It demonstrates the potential of how chicken collagen peptides can be a substitute for sweet commercial cryoprotectants like sucrose or sorbitol used in frozen foods.

• Subjects / Keywords

  • Collagen peptides
  • Poultry gelatin
  • Cryoprotective effect

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3R49GH8V

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.