Preparation Of Tea Polysaccharide Film And Application Of Fresh-keeping Activity

Tea Polysaccharide is a kind of natural bio-complex polysaccharide with many biological activities,and it has a large content in the old leaves of tea trees.It also has a wide application prospect in production.At present,the thick and old leaves of tea plants are often treated as waste in the production and management of tea gardens.If not handled properly,not only will huge resources be wasted,but also serious soil diseases will be caused.Therefore,how to make the tea garden wastes rationally resourced has become increasingly prominent.In order to improve the comprehensive utilization rate of tea resources,this paper studied the extraction of tea polysaccharide(TPS)from the thick and old leaves of ' Shaancha No.1' by hydrothermal extraction.Using sodium alginate(SA)as film-forming matrix,then compounded with 0%,20%,40%,60%,and 80% TPS and SA to prepare a TPS composite film with natural biological activity.The physical and chemical properties of the TPS film were determined.Based on this,the 'Jufeng' grape was used as the test material to determine the weight loss rate,rot rate,vitamin C,soluble solids,titratable acid,polyphenol oxidase and peroxidation.Physiological indicators such as enzyme activity explore the preservation effect of SA/TPS on 'Jufeng' grapes.Below are key research findings:1.The anti-oxidation performance of SA/TPS film showed that DPPH free radicals could be effectively removed by adding TPS,and the scavenging rate increased with the increase of TPS content.When the TPS dosage was 80%,the scavenging rate could reach 60.86%.Film contact angle test The results show that the TPS addition amount increases within the range of 20%-80%,the contact angle of the film surface decreases gradually,and the hydrophilicity increases.The tensile strength results show that the tensile stress of the film is 60% when the TPS is added.The tensile elongation at break was the best,113.44 MPa and 5.20%,respectively.The results of AFM showed that the surface roughness of the film decreased with the increase of TPS.The results of TG-DTG and DSC analysis showed that the addition of TPS could improve the water holding capacity of SA film.The results of XPS analysis showed that the addition of TPS increased the content of C1 s and N1 s in SA film,and the content of O1 s decreased accordingly.The results of water vapor transmission coefficient indicated that the water vapor transmission coefficient of SA film decreased with the increase of TPS.2.The SA/TPS film preservation study showed that polysaccharide film treatment could reduce fruit weight loss compared with non-coated(CT)treatment,but there was still a certain gap between the water retention and the commercial food fresh-keeping film(CK)treatment group;The fruit rot rate after treatment with TPS was 11.72%,10.37%,9.4%,9.17%,9.09%.Compared with the CT and CK groups,the fruit rot rate was significantly reduced.After storage for 16 days at 32 °C per day,the fruit decay rate was low and still had edible value;SA/TPS film treatment could effectively inhibit the decrease of Vc content.After 16 days of storage,the Vc content of the CT treatment group was 3.69 mg/100 g,and the CK treatment group was 4.03 mg /100 g,TPS film treatment group were 4.29,4.53,4.96,5.78,5.48 mg/100 g,respectively.The decrease rate of soluble solids and titratable acids in fruits was delayed.The results showed that TPS could effectively maintain the contents of Vc,soluble solids and titratable acids in fruits during storage and preservation,and maintain good taste and flavor of fruits;Compared with the CT and CK treatment groups,the TPStreated treatment group can effectively reduce the increase of polyphenol oxidase activity in 'Jufeng' grapes during storage.At the same time,it can increase the activity of peroxidase in fruits and reduce the senescence rate of fruits.