| The vacuum packaging is mainly used for preserving cooked salted duck eggs, which cost much and could easily cause-"white" pollution, and the mechanization degree of cooking and packaging is low. Application of new materials and new processes was the only way to modernize the traditional industry. Therefore, coating fresh-keeping technology has become a research hotspot in recent years. Polyvinyl alcohol shows the broad application prospects in the field of food packaging, and could be modified through nano-technology to improve packaging properties, which had been systematical studied by present research group. This paper proposes to study the packaging properties of PVOH-based nano-MMT composite materials, and as well as to explore the effect of nanocomposite on quality of salted eggs during storage, the idiographic contents are as follows:1. Effects of nanoclay type on the physical and antimicrobial properties of PVOH-based nanocomposite filmsPolyvinyl alcohols-based nanocomposite films with four types of organically modified montmorillonite (MMT) nanoclay (I.24TL,I.34TCN,I.44PSS) and a natural MMT (Na+-MMT) were fabricated by a solution-intercalation, film-casting method, and effects of the nanoclays were evaluated on physical properties, including transmittance, tensile strength (TS), elongation at break (E), water solubility (WS), swelling ratio (SR), water vapor uptake ratio (WVUR), and water vapor permeability (WVP), as well as antimicrobial activity of the polyvinyl alcohols-based films. Transmittance, WS, SR, WVUR, WVP of the nanocomposite films were significantly reduced by nano-composition compared to a pure polyvinyl alcohols film. The WVP decreased by 11.8%-20.7%, and WS, SR and WVUR decreased by 19.9%-41.8%,9.1%-26.4%, and 4.8%-12.8%, respectively. The extent of changes was dependent on nanoclay type. X-ray diffraction patterns revealed that intercalation was formed in nanocomposite films. Overall among all the tested nanoclays, Na+-MMT showed more impact on physical properties of polyvinyl alcohols films, and the Polyvinyl alcohols film compounded with quaternary ammonium group displayed remarkable antimicrobial activity against Gram-positive bacteria.2. Effect of nano-montmorillonite contents on packaging properties of Polyvinyl alcohol-based nanocomposite filmsPolyvinyl alcohol (PVOH)-based nanocomposite films with different amount of natural and organically modified nano-montmorillonite (Na+-MMT, I.34TCN) (0,2.5,5,10, 15, and 20g MMT/100g PVOH) were fabricated by a solution-intercalation, film-casting method, and effects of the MMT contents were evaluated on film packaging properties. Results on X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed exfoliated nanocomposite films at low level (2.5% and 5%), but intercalated nanocomposite films at high content (more than 10%) of nano-Na+-MMT addition, and their crystalline behavior and packaging properties was greatly influenced by MMT content. With the increase of nano-MMT content, water vapor permeability and water resistance of films increased, but transparency property decreased. Tensile strength of PVOH/Na+-MMT increased with increase in the MMT content up to 5%, and decreased with more than 10% of MMT incorporation, while PVOH/I.34TCN decreased as the contents increased, and both of their nanocomposite films became brittle after addition of MMT. Na+-MMT showed more compatible with PVOH relative to I.34TCN. PVOH/MMT with 5% nano-MMT addition was used to coating salted duck eggs based sensory evaluation.3. Effect of PVOH-based nanocomposites coating material on quality of salted duck eggs during preservation processSelf-maded salted duck eggs that were coated with PVOH, PVOH/Na+-MMT and PVOH/I.34TCN nanocomposite coating material, respectively, were stored at 27?, 50-60% relative humidity for 120 days, the loss of weight, pH, TVB-N, TBARS and total bacteria counts were detected during the storage process. The treatment of coating with polymer could significantly inhibit the increase of loss of weight, TVB-N, total bacteria counts and pH of egg yolk, as well as restrain the decrease of pH of egg white. The inhibition of PVOH/I.34TCN nanocomposite to increase of total bacteria counts, TVB-N, pH of egg yolk was significantly higher than other coating materials (P<0.05). However, the TBARS of salted duck eggs didn't change significantlyduring preservation (P>0.05). The results of sensory evaluation indicated that salted duck eggs coated with PVOH-based nanocomposite coating materials had better color and flavor. It's concluded that PVOH-based nano-MMT composite coating materials could effectively preserve the quality of salted duck eggs. |
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