| Ginseng(Panax ginseng C.A.Mey.)is a valuable traditional Chinese medicine and health food in China.Ginseng not only has antioxidant,blood pressure,lipid-lowering,anti-inflammatory,tumor cell growth inhibition and other effects,but also has anti-depression,relieve fatigue and other effects,is given the"king of herbs"reputation.September to October is the best season for harvesting ginseng.Due to high water content,fresh ginseng is not able to be stored after harvesting,and due to backward preservation technology and incomplete cold chain construction,it is easy to appear"heating","running pulp",mildew,black rot,softening and other phenomena,leading to the loss of active ingredients such as ginsenoside.At present,most of the harvested fresh ginseng is made into dry ginseng,red ginseng and sugar ginseng and other products,which are time-consuming,labor-intensive,loss of nutrients,affect the taste and expensive.Therefore,in order to better meet the demand of consumers and industrial production and reduce the loss of fresh ginseng,it is urgent to carry OTU research on new ginseng preservation processing technology to solve the shortage of ginseng supply and demand,single product and other problems.In this paper,the sterilization process conditions of fresh-cut ginseng slices by acidic electrolyzed-oxidizing water and low temperature plasma were respectively investigated,and the changes in the microbial flora structure on fresh-cut ginseng after sterilization by these two methods were detected and analyzed.The fresh-cut ginseng slices were stored by acidic electrolyzed-oxidizing water treatment?vacuum packaging?low temperature plasma treatment?near freezing temperature combined with fresh-keeping method,the quality changes of fresh-cut ginseng slices during storage were detected,and established a shelf-life prediction model.The research contents were as follows:1.In order to reduce the total number of colonies on fresh-cut ginseng slices,on the basis of single-factor experiments such as soaking time,material-to-liquid ratio,soaking temperature and p H value,the response surface design was used to optimize the sterilization process conditions of acidic electrolyzed-oxidizing water.The results showed that the order of the influence of various factors on the sterilization rate of acidic electrolyzed-oxidizing water was:material-liquid ratio>soaking time>soaking temperature;the optimal sterilization conditions were:material-liquid ratio1:10(g/m L),soaking temperature 25?,soaking time of 11 min,the sterilization rate under these conditions was 94.4%,and after treatment,the color of fresh-cut ginseng slices had no obvious change,and was lihgt yellow.Compared with other commonly used chemical fungicides,the sterilization rate of acidic electrolyzed-oxidizing water was increased by 25%?30%.2.In order to explore the sterilization effect of low temperature plasma and obtain the best sterilization process conditions,on the basis of the single factor experiments such as discharge power,processing time and gas flow rate,the response surface design of three factors and three levels was used to investigate the sterilization of low temperature plasma.The sterilization process conditions are optimized.The results showed that the order of the influence of various factors on the sterilization rate of low-temperature plasma was:plasma treatment time>discharge power supply>gas flow rate;the optimal sterilization conditions were:discharge power supply power of340 W,treatment time of 4.7 min,and gas flow rate of 10 cm~3/min,the sterilization rate under this condition reached 99.89%,and the color of fresh-cut ginseng slices did not change significantly after treatment,which was light yellow.Compared with acidic electrolyzed-oxidizing water sterilization,the sterilization rate of low temperature plasma treatment was increased by 5.3%,and the sterilization time was shortened by 57%.3.In order to explore the effect of acidic electrolyzed-oxidizing water and low temperature plasma treatment on the surface flora structure of fresh ginseng,the bacterial and fungal flora structures of fresh ginseng were analyzed by 16S r RNA and ITS amplicon sequencing technology.The results showed that a total of 1490 bacterial operational taxonomic units(OTUs)and 384 fungal OTUs were identified.According to the analysis of?diversity index,acidic electrolyzed-oxidizing water treatment and low temperature plasma treatment did not cause significant changes in the types of microorganisms on fresh ginseng.According to the distribution map of the flora structure,the two treatments can change the microbial diversity of fresh ginseng,and can lead to changes in the flora structure at both the phylum level and the genus level,and the change of the bacterial flora structure was greater than that of the fungal flora.4.In order to prolong the shelf life of fresh-cut ginseng slices,the fresh-cut ginseng slices were stored by combined fresh keeping technology,and the changes of the color,physicochemical indexes and the total number of colonies of fresh-cut ginseng slices during storage at-2?,4?,25?and 36?were studied.Furthermore,by studying the change rule of the total number of colonies of fresh-cut ginseng slices with storage time at different storage temperatures,a prediction model of shelf life was established.The results showed that:acidic electrolyzed-oxidizing water treatment?vacuum packaging?low temperature plasma treatment?low temperature storage was determined as the combined preservation and storage process.Storage at-2?and 4?can effectively inhibit the growth of the total number of colonies,the decrease of moisture content,total polyphenol content and soluble protein content on fresh-cut ginseng slices,and delay the color change;and when stored at-2?,the change rate of the quality index of fresh-cut ginseng slices was lower than 4?.After60 days of storage,the contents of ginsenosides Rg1 and Rb1 in fresh-cut ginseng slices under the four storage temperature conditions were all increased;the content of ginsenoside Re in fresh-cut ginseng slices increased when stored at-2?and 4?,and decreased when stored at 25?and 36?.It indicated that low temperature storage could effectively inhibit the change of fresh-cut ginseng slice color,the change of nutrient content and the growth of total number of colonies.The shelf-life prediction model of fresh-cut ginseng slices was established by the first-order kinetic formula and Arrhenius equation.The predicted shelf-life of fresh-cut ginseng slices stored at-2?and 4?can reach 550 days and 395 days,and the actual shelf-life was 520 days and 380 days.The error between the actual value and the predicted value was less than 10%at both temperatures,which indicates that the model can predict the shelf-life of fresh-cut ginseng slices well. |
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