| Xinjiang has abundant rose resources,planted with native Hetian roses,the fragrance of roses is sweet and pure,not only can be used to extract essential oils,but also can be used as edible,with high nutritional value and commercial value.However,the effects of respiration and mechanical action on the rose are prone to browning,resulting in a sharp decline in sensory and nutritional value.This topic chooses Xinjiang Hetian Rose,study on physiological and biochemical changes related to browning of postharvest roses,the changes of phenolic substrate during browning and the enzymatic properties of polyphenoloxidase.The effects of various factors on the enzymatic browning reaction of rose were discussed.It provides a theoretical basis for the suppression of browning of roses.The research results are as follows:(1)Study on the extraction method of total phenol from rose:Selecting ultrasound assisted extraction,study on effects of solvent concentration,solid-liquid ratio,ultrasonic time and ultrasonic temperature on the extraction of total phenol.The extraction conditions of rose total phenol after optimization by response surface are:solvent concentration of 69%,ultrasonic temperature of 59 ?,time of 29 min,solid-liquid ratio of 1:14,ultrasonic power of 140 W.(2)Changes of phenolic compounds in process of rose browning:UV was used to screen 9 substrates such as chlorogenic acid,gallic acid and kaempferol to participate in the enzymatic browning reaction of rose.The content of chlorogenic acid,caffeic acid andkaempferol varied greatly between 2 and 3 h by high performance liquid chromatography.The content of isorhamnetin and protocatechuic acid was less changed.Combined with correlation analysis,the correlation between chlorogenic acid,caffeic acid,kaempferol,gallic acid,vanillic acid and polyphenol oxidase enzymatic browning was significant.(3)Physiological and biochemical changes in process of rose browning:Analysis of the changes and correlations of browning degree,anthocyanin content,total phenolic content and browning-related enzymes during browning.There is a very significant correlation between anthocyanin content,total phenolic content,polyphenol oxidase activity,and browning.There was no significant correlation between peroxidase activity and browning.(4)Study on enzymatic properties of polyphenol oxidase from rose:By investigatingthe enzymatic properties of Hetian rosette polyphenol oxidase,the optimal buffer for rose polyphenol oxidase is pH 7.0 and the optimum reaction temperature is 40 ?,stable at around 50?.The optimum concentration of substrate is 0.04 mol/L,Km and Vmax are 0.351 mol/L and 76.335 U/min.L-ascorbic acid has strong inhibitory effect on rose PPO.Mg2+,Fe2+and K+promoted the activity of polyphenol oxidase in rose,Mn2+ and Cu2+had a two-way effect on polyphenol oxidase activity,while Ca2+,Zn2+andBa2+inhibited the activity of polyphenol oxidase in rose. |
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