Effects Of Cysteine And Glutathione Combined Ultrasonic Treatment On Quality Of Fresh Cut Lotus Root

Lotus root(Nelumbo nucifera)is suitable for fresh cutting,but the quality of fresh cut lotus root is affected by enzymatic Browning reaction caused by phenol and polyphenol oxidase exposed to air.In order to prevent Browning safely and efficiently,the research group used ultrasonic,cysteine,glutathione,combinative application of ultrasonic(US)and cysteine(Cys),ultrasonication(US)for combined with glutathione(GSH)to treat lotus root,and explored its effects on the quality of lotus root during cold storage.The main results are as follows.1.This study investigated the effects of ultrasound(US)power of 200 w at a constant frequency of 40 kHz for 2 min,0.01 % cysteine(Cys)and combinative application of US and Cys(US + Cys)on browning prevention and quality of lotus root slices were compared during storage at 4 °C for 12 d.The visual appearance,colour attributes including L*,b*,hue,chroma,whiteness index(WI),browning index(BI)and colour difference(ΔE*),browning enzymes activities such as polyphenol oxidase(PPO)and peroxidase(POD),total phenols concentration,texture,total sugars concentration and antioxidant activities were evaluated.US + Cys retarded browning incidence being greater than Cys,US and control treatments,respectively.The browning retardation was concomitant with the retention of high L* and WI values and low b*,chroma,BI and ΔE*value.Cys and US + Cys controlled the increased PPO activity rather than US.All treatments delayed the increased total phenols concentration compared to control.All treatments maintained hardness of lotus root slices,especially US,and did not affect total sugars concentration.Both sonication treatment enhanced ferric reducing antioxidant potential(FRAP)whilst free radical scavenging activity was enhanced by Cys.In conclusion,both of the Cys and US could prevent browning and maintain physicochemical quality of lotus root slices and the simultaneous US and Cys treatment exhibited synergistic antibrowning effect.2.Efficacy of 40 kHz(200 W)ultrasonication(US)for 2 min combined with glutathione(GSH)at 0.5% w/v(US + GSH)in preventing browning and preserving the physicochemical quality of lotus rhizome slices stored in a 4±1 °C refrigerator.According to the visual appearance of the slices,US + GSH treatment more effectively inhibited the browning of the cut surface than did GSH or US treatment alone.US + GSH and GSH treatments were more effective than US and control treatments in preserving the slices’ colour attributes,such as their lightness and whiteness index values,and potentially retarded enzymatic browning reactions and increases in browning index and total colour difference values.Moreover,the application of US and US + GSH treatments noticeably preserved the texture of the slices.None of the treatments affected the total sugar content during storage.The US + GSH treatment markedly enhanced the ferric reducing antioxidant potential of the slices during storage.The slices treated with US,GSH,and US+ GSH exhibited slower reductions in 2,2-diphenyl-1-picrylhydrazyl(DPPH)free radical scavenging activity than did the controls.In conclusion,US + GSH treatment is a feasible approach for inhibiting browning,maintaining texture,and inducing antioxidant activity in lotus rhizome slices during storage.