Effects Of Frozen Storage Temperature On The Storage Quality Of Dahongpao Fresh Pepper(Zanthoxylum Bungeanum Maxim.)

Zanthoxylum bungeanum Maxim is a product with a rich flavor and medicinal properties.However,it is prone to browning and dehydration during storage,resulting in the losses of aroma,numbness,bioactive substances and antioxidant ability,which seriously affects its storage quality and lifespan.Frozen storage is a safe and efficient technology for fruit and vegetable preservation,but this technology is only preliminarily reported in the preservation of Z.bungeanum,and it is still unclear that the changes of the sensory quality,the content of bioactive substances and antioxidant indexes of fresh Z.bungeanum stored at different freezing temperatures,as well as the storage lives at the temperature of each frozen storage.In this study,Hancheng Dahongpao fresh Z.bungeanum were stored at different temperatures（0,-7,-20 and-35℃）for 12 months,and then the changes of sensory,bioactive substances and antioxidant capacity were monitored,as well as the interrelationships among various indicators were analyzed to determine the appropriate freezing temperature and storage lives.The aim of this study was to realize the annual supply of fresh Z.bungeanum and to provide theoretical basis and application technology for its industrial development.The main results were as follows:（1）The browning of fresh Z.bungeanum was significantly reduced by each freezing temperature,with the brown percentage as high as 50%for 0℃at 1 month,and there was no obvious browning at-7℃,-20℃and-35℃.The frozen storage treatments still did not show obvious browning except for-7℃sample at 12 month.Compared with-7℃,-20℃and-35℃effectively slowed down the loss of moisture content and the production of ice crystals and cracking of fresh Z.bungeanum during storage,with 97.6%,18%and 6.4%cracking of fresh Z.bungeanum stored in the three conditions at 12 months,respectively.（2）The losses of anthocyanin,volatile oil and numbing substance content was 48.6%,18.4%and 1.3%,respectively,when fresh Z.bungeanum was stored at 0℃for 1 months.Frozen storage delayed the loss of these substances,and the preservation of the three substances were better at-20℃and-35℃.These substances of fresh Z.bungeanum lost73.2%,14.5%and 0.8%in-7℃,14.3%,10.3%and 0.1%in-20℃,and 15.6%,9.0%and0.4%in-35℃at 12 months,respectively.The volatile oil components changed the most during-7℃storage,and they were the most species at 12 months.Frozen storage treatments promoted the increase of total phenols,total flavonoids and As A content of fresh Z.bungeanum and maintained the high content of bioactive substances in the fruit.-7℃maintained the higher contents of total phenols and total flavonoids,and-20℃and-35℃maintained the higher contents of other bioactive substances.（3）The MDA content of fresh Z.bungeanum stored at 0℃for 1 month did not change significantly,and its DPPH radical scavenging capacity and FRAP increased by 16.8%and7.8%,respectively.Frozen storage stimulated the production of O₂^-.and H₂O₂in fresh Z.bungeanum and led to the accumulation of MDA content,which increased by 58.1%,31.5%and 14.7%at-7,-20 and-35℃for fresh Z.bungeanum at 12 months,respectively.Frozen storage maintained high level of antioxidant substances content and promoted the increase of antioxidant enzymes（SOD,CAT,POD and APX）activities of fresh Z.bungeanum during storage,thus maintaining a high antioxidant capacity.During 12 months storage,the DPPH radical scavenging capacity of fresh Z.bungeanum at-7,-20 and-35℃increased by 31.1%,57.1%and 65.9%,respectively,and the mean values of FRAP increased by 13.6%,23.4%and 27.9%,respectively,and storage at-20℃and-35℃significantly improved the antioxidant capacity.In conclusion,the storage life of fresh Z.bungeanum at 0℃was less than 1 month.Frozen storage effectively maintained the sensory quality,bioactive substances and antioxidant properties and significantly extended their storage life of fresh Z.bungeanum,and the effect increased with the decrease of the freezing temperature.The storage lives of fresh Z.bungeanum were less than 4 month at-7℃and more than 12 months at-20℃and-35℃.