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 ?g/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 12 th when the total aerobic count reached the acceptable limit,while it was 5.79 on Day 16 th 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. |