Effects Of Low Temperature Plasma Treatment On Quality And Antioxidant Activity Of Fresh-cut Ginger Slices And Ginger Powder

Ginger is one of the first batch of medicine and food homologous foods published in China,which combines nutritional value and medicinal value.However,in the process of processing and storage,ginger is easy to produce water loss,browning and tissue softening,which reduce its nutritional value and edible quality.Low temperature plasma is a new non-thermal processing technology,which has the advantages of low treatment temperature,safety and wide application range.This paper mainly explores the effect of low temperature plasma on the bactericidal effect and quality of fresh-cut ginger slices,and low temperature plasma as pretreatment assistance ultrasound to improve the ginger flavonoids yield and preliminary discussion on the mechanism,finally the antioxidant activity of total flavonoids extracted from ginger powder is analyzed.It provides theoretical basis for further processing and comprehensive utilization of ginger.1.Taking the sterilization rate of fresh-cut ginger slices as the index,the effects of low temperature plasma discharge power supply and treatment time on the sterilization effect of ginger slices were investigated,and the response surface optimization design was applied.The optimum sterilization conditions were as follows: the discharge power was 400 W,the treatment time was 4.6 min,and the sterilization rate was 99.89%.Among them,the low temperature plasma treatment time had a more significant impact on the sterilization effect than the discharge power supply power.Further,on the basis of the best sterilization rate,the effect of low temperature plasma treatment on the quality of fresh-cut ginger slices was explored.The results showed that there was no significant difference in the contents of total polyphenols and flavonoids in ginger slices before and after plasma treatment,gingerol content decreased by 35.18%,DPPH radical scavenging rate increased by 33.64%.Low temperature plasma treatment had no significant effect on the color of fresh-cut ginger slices.This showed that low temperature plasma treatment could be used as a more effective and convenient sterilization method of fresh-cut ginger slices.2.To explore the effect of low temperature plasma pretreatment assisted ultrasonic method on the extraction of total flavonoids from ginger,the process was optimized and preliminarily explored the mechanism,so as to provide a new method for the extraction of flavonoids from ginger.Taking the yield of total flavonoids in ginger powder as the index,and taking the low temperature plasma discharge power supply,treatment time and air intake as the investigation factors,the three factor and three-level response surface optimization design was carried out.The optimum extraction conditions of total flavonoids from ginger powder were as follows: discharge power295 W,treatment time 60 s,air intake 150 SCCM,and the yield of total flavonoids was26.4 mg/g.A high performance liquid chromatography(HPLC)analytical method for the simultaneous determination of 21 polyphenols in ginger was established.The chromatographic conditions were poroshell 120 EC-C18 column(4.6 mm)×150 mm,4?m),the mobile phase was 0.1% phosphoric acid(A)and acetonitrile(B),and the detection wavelength was 230 nm.Under this condition,21 polyphenols could be well separated,with high precision(RSD?3.75%),good stability(RSD?4.25%),good repeatability(RSD?4.75%),accurate and reliable spiked recovery results(average recovery 84.11%?100.86%).Before and after low temperature plasma treatment,the content of 21 polyphenols in ginger were determined by HPLC,and the structure of ginger powder before and after treatment was characterized by scanning electron microscopy(SEM)and fourier transform infrared(FTIR).The results showed that after low temperature plasma treatment,the flavonoids in ginger showed an increasing trend,while the phenolic acids showed a decreasing trend;The etching effect of plasma increased the surface roughness and leaded to the lignin decomposition of ginger powder,which increased the contact area between the extraction solvent and ginger powder,which was conducive to the penetration of the solvent.3.Analysis of antioxidant activity for low temperature plasma-ultrasonic extract extraction solution,and compared with ultrasonic method,enzyme method and water method.Low temperature plasma-ultrasonic method extraction total flavonoids was significantly higher than that of ultrasound,enzymatic and water proposed,and increased by 23.70%,9.76%,77.42%,respectively;the gingerol content extracted by enzymatic method was higher than that extracted by low temperature plasma-ultrasonic method and ultrasonic method;there was no significant difference in the total polyphenols content extracted by low temperature plasma-ultrasonic method,ultrasonic method and enzymatic method,while the total polyphenols content extracted by water method was the lowest;In terms of antioxidant activity based on free radical scavenging rate and reduction ability of iron ion,low temperature plasma-ultrasonic method ?ultrasonic method had stronger antioxidant activity,and low temperature plasmaultrasonic method was slightly lower than ultrasonic method,which might be caused by degradation of phenolic acid.In terms of antioxidant activity based on the absorption capacity of oxygen free radicals,the order of antioxidant activity of extracts extracted by different methods was ultrasonic method > enzymatic method > low temperature plasma-ultrasonic method > water extraction.In terms of antioxidant activity based on the ability to inhibit hydroxyl free radicals,The order of antioxidant activity of extracts extracted by different methods was enzymatic method > low temperature plasmaultrasonic method > ultrasonic method > water extraction.