| The wasted limed hides in tanneries were utilized to prepare acid relaxed collagen fibers in this work; further, the film-forming properties of prepared collagen fibers were studied. In order to enhance the mechanical properties of collagen fiber film, methods such as adding hydroxyapatite, in situ apatite and adding laponite were used, meanwhile, the effects of these inorganic particles on the performance of collagen fiber film for food packaging were investigated.The main chemical components of limed hides (dry basis) were listed below: water,5.07%, ash, 2.09%, protein, 89.61%, lipid, 2.99%. The fabrication techniques of collagen fibers were classified into washing, pickle, relaxing, grinding, etc. Single factor experiments showed that the 0.01 M hydrochloric acid could swell the limed hides to 100.37%. Besides, the swollen hides became soft, which was suitable for relaxing. The diameter and length of collagen fibers prepared in this method ranged from 3 to 4 ?m and 0.5 to 1.0 cm. The calcium and collagen contents of prepared collagen were 0.096% and 98.97% respectively. Infrared spectrum analysis indicated the prepared collagen fiber was typically Type-? collagen and the total content of Alpha helix and beta-pleated sheet in the secondary structure was 69.02%, which suggested that the collagen fiber has a stable molecule structure.Fabrication of composite film with acid-swollen collagen fiber and nano-hydroxyapatite: Acid-swollen collagen fibers and nano-hydroxyapatite (HA) at 1 wt%,2wt% and 4wt% were used to develop a biodegradable film with glycerin as plasticizer. At 4 wt% of HA or below, collagen fiber formed acceptably homogeneous films, with HA dependent increase in opacity and color. SEM images showed adding HA caused the composite films a coarser and uneven surface and a more compact inner structure. HA addition significantly augmented tensile strength of the composite films to 48.20 MPa from 38.98 MPa along with an observable decrease in elongation. Furthermore,film's water vapor (WVP) and oxygen barrier property were enhanced; for example, the WVP was reduced to 1.30×10-11 g-m/Pa-m·s when the HA content reached 4%. Additionally, the DSC showed that the melting point of composite film with 4wt% HA was increased to 96.18 ?, indicating that the thermal stability of the films was mush improved. Collagen fiber-HA composite film provides the potential to apply as a novel material for food packaging.Fabrication of composite film with in situ apatite and collagen fibers: This study attempted to prepare apatite in situ in acid-swollen cowhide collagen film by an ammonia gas fumigating method and assess its reinforcement effect on a collagen fiber film for food packaging applications. The X-ray diffraction and Fourier transform infrared spectroscopy results confirmed the successful synthesis of apatite in collagen fiber films. SEM images showed that tiny apatite particles appeared as a coating on the film surface and also made the film's inner structure more compact and less porous than pure collagen fiber film.Apatite significantly (p<0.05) increased the tensile strength and improved the water vapor barrier and water insolubility properties of collagen fiber film. Moreover, the thermogravimetric and differential scanning calorimetry results confirmed that the thermal stability of collagen was improved with the increasing apatite. The in situ-synthesized apatite provided a practical reinforcement approach to improving the collagen fiber film's performance and benefited its application as a food packaging material.Fabrication of composite film with collagen fibers and laponite: This study aimed to prepare collagen fibers from liming hides and fabricate collagen fiber-laponite composite film through casting and dehydration, and its packaging related properties were investigated.The results showed the collagen fibers could form homogeneous gelatinoids as the ratio of collagen fiber and loponite was controlled at 60:4 (w:w) or below. As the collagen fiber to laponite ratio was 60:4, the tensile strength and elongation of collagen fiber-laponite composite film reached 62.80 MPa and 11.04% respectively. Furthermore, the barrier capacity of water vapor and oxygen were increased by 39.67% and 32.42% respectively.Meanwhile, laponite obviously inhibited swelling property and improved thermodynamic stability of the film in a concentration dependent manner. The changes in microstructure of the composite were also characterized using a scanning electron microscope. Collagen fiber-laponite composite film could be a promising material in food processing where packaging with specific strength and good water resistance is needed, such as meat, aquatic product, etc. |
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