Study On Microbial Contamination Analysis And Radio Frequency Assisted Hot-air Drying Process Of Zanthoxylum Bungeanum

In this study,56 samples of dried Zanthoxylum bungeanum collected from 22 regions in Sichuan Province were tested for microbes to investigate the pollution status of commercially available samples.And samples with high total number of colonies were analyzed for microbial heat resistance.At the same time,using fresh "Dahongpao" Zanthoxylum bungeanum as materials,to analyze the effect of different temperatures on the survival of microorganisms carried in the fresh Zanthoxylum bungeanum.On this basis,with hot air drying as a control,with the goal of better product quality and higher microbial safety after drying,the process of radio frequency assisted hot air drying of Zanthoxylum bungeanum was optimized.The main research contents and results of this study are as follows:1.According to methods of GB/T 4789,56 samples were tested for microorganisms.By comparison with GB/T30391-2013,we found that: The unqualified rate of 56 samples was89.29%,among which the unqualified rate of granular Zanthoxylum bungeanum and powder Zanthoxylum bungeanum was 85.71% and 92.86%,respectively.And the main cause of the sample unqualified was the coliform bacteria exceeded the standard.The results showed that the sanitary condition of dried Zanthoxylum bungeanum was poor and its microbiological safety was worthy of attention.2.Three samples of dried Zanthoxylum bungeanum with high pollution were selected for the background microbial heat resistance test.The samples were packed into aluminum TDT heating units and respectively treated in 80 ?and 100 ? water bath.The analysis of the survival number of background microorganisms found that the total number of colonies of the three samples treated in 80 ? water bath after 80 min could not meet the NY/T901-2011 limit requirement.After treatment in 100 ? water bath for 40 min,although the total number of colonies of the three samples can meet the limit requirements of NY/T901-2011,but the aroma of the sample is seriously lost and the quality is reduced.Due to the low moisture content of the sample,the background microorganisms in dried Zanthoxylum bungeanum showed high heat resistance.The use of heat treatment to control the microorganisms in dried Zanthoxylum bungeanum had limited control effects,and it was easy to reduce the quality of products.3.Aluminum TAC heating units were used to analyze the background microorganism heat resistance of the fresh Zanthoxylum bungeanum.The results showed that the total number of colonies of the fresh flower pepper sample reached 4.69 ± 0.38 log CFU/g.During the heat treatment,the total number of colonies stabilized after a short period of rapid decline;The decrease rate of the total number of colonies at 50 ? was slow,the total number of colonies decreased to 2.26±0.29 at 12.5 min.At this time,the sensory maintenance of Zanthoxylum bungeanum was better;When heated at 60 ? for 5 min,the total number of colonies decreased to 1.85±0.19 log CFU/g,which could achieve a good sterilization effect.At 70 ? and 80 ?,the total number of colonies can be greatly reduced within 2.5 min,and the numbers are reduced to 1.70±0.19 log CFU/g and 1.75±0.25 log CFU/g,respectively.However,because of the high temperature,the oil cells on the surface of Zanthoxylum bungeanum are destroyed,the oil leakage is serious and the quality is inferior.4.The best conditions for radio frequency heating of peppercorns were determined as: the electrode gap was 115 mm,the heating time was 180 s,and the material layer thickness was 60 mm.Under this condition,the average temperature of the materials after the radio frequency heating was 56.6 ?,the cold spot temperature was 51 ?,the heating uniformity index was0.116,and the sensory evaluation score was 74.5.Compared with 50 ? hot air drying(CK),it was found that the dried products of Zanthoxylum bungeanum after radio frequency assisted hot air drying(RF-HA)were not significantly different from the CK treatment group in terms of water content,water activity and seed removal rate,but it was significantly different from the CK treatment group in terms of color difference and sensory evaluation,and the quality of Zanthoxylum bungeanum decreased.Through the tracking of the total number of colonies during the drying process,it was found that the total number of colonies in the RF-HA treatment group decreased significantly after RF treatment.It can be speculated that RF-assisted hot air drying is beneficial to control the microbial quality of Zanthoxylum bungeanum.