Characterization of PLA-PHB Based Active Packaging Film, and Its Application on Oysters
Type of DegreeMaster's Thesis
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Biodegradable material polylactic acids (PLA) and polyhydroxybutyrate (PHB) were designed as the matrices for active food packaging applied on oysters. In this study, the performance of bioplastics was first evaluated through the comparison of PLA-PHB and Ethanol vinyl alcohol (EVOH, as reference group). Detailedly, mechanical properties such as tensile strength, elongation at break, oxygen transmission rate (OTR), water vapor permeation (WVP); active properties including releasing, antibacterial and antioxidant were determined. Then the effectiveness of preserving oysters was valued via the contrast of PLA-PHB and PLA-PHB with fennel oil (PLA-PHB-FEN). More specifically, bacteria, pH value, TVB-N, texture profile and free amino acids of oyster samples were tested. The results showed that the overall properties of PLA-PHB are nearly comparable to those of EVOH except for the oxygen barrier property. The release of fennel oil in 65% ethanol ranked highest and the maximum concentration is 38.82 µg/mL. Though the release in water is very low, PLA-PHB-FEN still presented almost 1 log inhibition on selected bacteria. When applying on oysters, the count number of aerobic and anaerobic bacteria were both 1 log CFU/g lower in PLA-PHB-FEN than in PLA-PHB and EVOH. In addition, the pH value of oyster samples was 5.98 and 5.96 respectively in PLA-PHB and EVOH on Day 12th when the total aerobic count reached the acceptable limit, while it was 5.79 on Day 16th in PLA-PHB-FEN packaging. The dominant free amino acids in oyster samples are glutamic acid, histidine, alanine and arginine, accounting for about 92.91% of total amount of amino acids. Oyster samples have less total amount of amino acids in PLA-PHB-FEN than other two packaging, indicating that there were less bacteria activity due to the inhibitory action of fennel. We concluded that this biodegradable packaging is effective to extend the shelf-life of oyster samples for 2 to 3 days with the function of fennel oil.