| Zanthoxylum schinifolium Sieb.et Zucc is one of the main spices in our country, its quality is better than Zanthoxylum Bungeanum Maxim, it has the higher nutrient and the strong numb-taste, what's more, its odor is more fragrant, but Zanthoxylum schinifolium Sieb.et Zucc is prone to browning during storage and its fresh time is short, thus its exploitation is limited. This paper tries to solve the drawbacks that Zanthoxylum schinifolium Sieb.et Zucc hard to store and extend the period of fresh time. This article takes the Zanthoxylum schinifolium Sieb.et Zucc from Hanyuan as the experimental object, firstly, the pre-treatments before storage (including the heat treatment and color protecting experiment) were optimized, and then, Zanthoxylum schinifolium Sieb.etZucc processed by the best pre-treatment were coated with different concentrations of chitosan and packaged by polyethylene film bag, finally, they were storaged at 4℃in the refrigerator. According to study the qulity and physical change of Zanthoxylum schinifolium Sieb.et Zucc during the storage, the optimum concentration of chiostan coating is determined. This paper also preliminarily studied the browning mechanism of Zanthoxylum schinifolium Sieb.et Zucc through measuring the relationship among the degree of browning, POD activity, PPO activity, Vc content and total phenolic content during storage, and concluded the main cause of its browning, Finally, this paper studied the enzymatic properties of PPO. The study results can provide the experimental basis to study the storage technology of Zanthoxylum schinifolium Sieb.et Zucc and have the positive effect on extend the storage time and fresh time. In this paper, main results are as follows:1. Using citric acid, ascorbic acid, zinc acetate, and soaking time for testing factors, PPO activity and chlorophyll content after treatment for two days as the measured indicators, the L9(34) orthogonal experiment is chosen, the result showed that the best process of green protecting for Zanthoxylum schinifolium Sieb.et Zucc is 0.70% citric acid, 0.80% ascorbic acid,0.05% zinc acetate and the soaking time for 60.00min.2. Through the single factor test of instantaneous high temperature steam treatment, with steam pressure, steam processing time and feeding amount as three factors which affect the volatile oil content of Zanthoxylum schinifolium Sieb.et Zucc, make the Box-Behnken central composite design, after the response surface optimization, the most optimal heat treatment conditions were:steam pressure 0.33MPa, steam treatment time 12.40s, feeding amount 2696.00g/m2, in this response surface model, the predicted value of volatile oil content is 0.41mL/20g, amended the optimal conditions for the vapor pressure 0.35MPa, the steam treatment time 13.00s, feeding amount 2720.00g/m2, the volatile oil content is 0.39mL/20g, it is the 95.24% predictive value, indicating that the model can well reflect the high-temperature steam treatment conditions, and it is feasible to determine the heat treatment conditions by the response surface.3. With the different concentrations of chitosan coating preserving the Zanthoxylum schinifolium Sieb.et Zucc, test results showed that 1.0% chitosan coating is the best process, which can can effectively delay the loss of nutrients and body aging.4. This study showed that the browning degree of Zanthoxylum schinifolium Sieb.et Zucc and PPO activity, total phenolic content was significantly related during storage at 4℃, r values were 0.9936 and 0.9616 respectively, therefore, it can preliminarily determi-ne that the Zanthoxylum schinifolium Sieb.et Zucc pericarp browning is mainly due to PPO enzymatic oxidation.The studies of polyphenol oxidase enzymatic characteristics on Zanthoxylum schinifo-lium Sieb.et Zucc have showed that:when gallic acid is as the substrate, the optimum temperature of polyphenol oxidase enzymatic reaction is 25℃; the optimum pH value is 6.81; Km=0.004mol/L, Vmax=2x103g.min/U; polyphenol oxidase enzyme of Zanthoxylum schinifolium Sieb.et Zucc is a more heat-resistant enzyme, this study found that the reminant PPO activity is still 27% during the processing with 90℃,120s; citric acid and ascorbic acid are the strong inhibitors,1.0% ascorbic acid and 0.9% citric acid can effectively inhibit the activity of polyphenol oxidase. |
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