Study On Preparation Of Carvacrol-β-cyclodextrin Inclusion Complex And Its Slow-release Preservation For Chinese Bayberry

Chinese bayberry is a special fruit produced only in southern China. It has colorful appearance, sweet and delicious flavor and is well-liked by the consumers. However, Chinese bayberry is harvested during hot raining season and has high respiration rate, therefore, it is highly perishable. In addition, the fruit does not have protective outer layer and is easily suffered from mechanical damage and pathogen infection, so the shelf life of Chinese bayberry is very short. Chemical treatment can be effective for the preservation of Chinese bayberry, but chemical preservation is harmful to human health and no longer suitable for use in the market, so it is very important to look for safer and more efficient preservation methods.Carvacrol is a essential oils which used to preserve fruits with a good effect, but it is easy volatile, oxidized and inconvenient to use.In this study, β-cyclodextrin and carvacrol were used as raw materials. The slow-release carvacrol-β-cyclodextrin complex was prepared with saturated water solution. The inclusion complex’s natural property was studied in preliminary research and then it was applied to Chinese bayberry preservation. The main results were as follows:1. The preparation of carvacrol-β-cyclodextrin inclusion complex.(1) The optimum conditions for carvacrol-β-cyclodextrin inclusion complex.The inclusion complex was prepared with β-cyclodextrin as wall material and carvacrol as core material. The optimum conditions for inclusion complex were established through single factor and orthogonal experiment. The results showed that the best proportion of core material and wall material were 1:8; and inclusion time was 2h; the temperature was 60℃. Under this condition, the inclusion rate could reach 61.89%.(2) The characterization of carvacrol-p-cyclodextrin inclusion complex.The inclusion complex was identified by using scanning electron microscopy, infrared spectrum and fluorescence spectrum. The results showed that scanning electron microscopy confirmed the different crystalline between inclusion complex and β-cyclodextrin. The infrared spectrum and fluorescence illustrated the difference of structure and properties. These results verified the formation of inclusion complex.(3) The effect of different temperature and humidity for release of carvacrol-β-cyclodextrin inclusion complex.Both temperature and humidity can impact on release of inclusion complex. With the increase of ambient temperature, the release rate of carvacrol became faster. Therefore, high temperature favored the release of carvacrol, and low temperature tended to make it more stable. With the increase of relative humidity, the release rate of carvacrol also speeded up. Avrami’s regression was used to analyze the release of carvacrol and the results showed that release mechanism parameters of carvacrol were between 0.54 and 1 at 10℃ and 40℃ conditions. It was the first grade release and diffusion-limited kinetics. Moreover, at the 25℃ conditions, the release mechanism parameters was less than 0.54. It belonged to the kinetics of diffusion limited. Under various relative humidity conditions, the release mechanism parameters were less than 0.54. It was close to the kinetics of diffusion limited.2. The purifaction and identification of post-harvest Chinese bayberry pathogenic fungi and antibacterial test.Three pathogenic fungi of Chinese bayberry were purified and identified, at the same time; the inhibitory test of these fungi was performed with inclusion complex. The results showed that three pathogenic fungi were P.citrinwm Thom, A.niger and P.digitatum. In addition, these three pathogen fungi were all restrained by inclusion complex, with the best results for P.digitatum. The most effective concentrations of inclusion complex to inhibit P. digitatum, P. citrinwm Thom and A. niger were 0.03,0.08 and 0.1 g, respectively.3. The slow-release preservation research of carvacrol-β- cyclodextrin inclusion complex for Chinese bayberry.Different quantities of inclusion complex were used to treat Chinese bayberry. The results showed that Chinese bayberry maintained the best quality when the amount of inclusion complex was 2 grams per 500 grams of Chinese bayberry. The slow- release carvacrol effectively retarded the decline of fruit firmness, total soluble solids, titratable acid and Vc content, and improved the peroxidase (POD), catalase (CAT), superoxide dismutase (SOD) enzyme activities, and induced the rise of total phenol content, inhibited polyphenol oxidase (PPO) and lipoxygenase (LOX) activities, reduced the rotting rate and delayed the senescence of the fruit. The treatment also maintained the color and luster of Chinese bayberry.