Study On Controlled Atmosphere Storage Of Lotus Root

Lotus rhizome(Nelumbo nucifera Gaertn),belonging to genus Nelumbo Adans and family Nymphaeaceae,is an important aquateic plant in China.According to the "948" rolling project Introduction of High-quality Cultivars of Aquateic Vegetable and Safe and Key Production Technologies(number:2003-T5),researches were conducted with the cultivar "Elian 5" via studying the key technologies,such as selection of bactericidal agent, color fixative combinations,gas proportion regulation in atmosphere packaging,etc.The results were as following:1.Section of the lotus rhizomeFour original lotus rhizome cultivars,"Wuzhi 2","Qingmaojie","Elian 4" and "Elian 5",were used as experimental material.The results showed that "Wuzhi 2" and "Elian 4" mostly endured storage following by "Qingmaojie" and "Elian 5",regardless of the storage temperature 0～6℃or 5～15℃.In order to study the proper storage methods,"Elian 5" that did not endure storage among the four cultivars was used the material for further study.2.Selection of bactericidal agentThree different bactericidal agents(A),sodium hypochlorite(B),qianglian and combination of sodium hypochlorite and qianglian(C),were used to treated the materials for disinfection.The results showed that after treated with 200 mg/kg A(2.5 min),80 mg/kg B(2 min) or combination of 60 mg/kg A and 150 mg/kg B(2.5 min),the bacteria and E.coli of the materials stored for 15d did not multiple and the number of them kept stable. According to published reports,when vegetable began to rot,the total number of bacteria reached 106 every gram;the number standard of bacteria rated to fresh vegetable is below 106 every gram in Japan.In our experiment,B was chosen as bactericidal agent to adapt to Japanese standard.3.GRAS color fixative combination and treatmentFour color fixative,Calcium chloride(D),sodium pyrophosphate(E),citric acid(F) and phytic acid(G),were used for color fixation in our experiment with orthogonal design.The levels of the different factors were:D[0.3,0.5,0.7%],E[0.4,0.5 0.6%],F[0.2,0.3,0.4 %],G[0.1,0.2,0.3%].Experimental results showed that the optimal factor combination was 0.5%D+0.5%E+0.3%F+0.2%G.4 Gas proportion studyTo study the effect of gas on lotus rhizome storage,different proportion of gas was used for combination experiment with obvious material browning as criterion.Our results showed the best gas combination:90%N₂+5%O₂+5%CO₂.5.Study on package and storage conditionsThe feature quality was investigated under five temperature ranges,0～2℃,2～4℃, 4～6℃,6～15℃and 15～25℃,using LDPE bag in 0.05 mm thick and vacuum multiplicity bag as gas regulation package.In our experiment,the feature quality of the lotus rhizome in gas regulation package with vacuum bags did not changed under 0～4℃for 60 d or 4～6℃for 30 d or 6～15℃for 15d or 15～25℃for 10～15 d.The physiological and hygienical index and microorganism number was investigated for lotus rhizome under 0～4℃storage.No change was found with feature quality when lotus rhizome was stored with LDPE bag(0.05 mm thick) under 0～4℃for 10～20 d or 4～6℃for 5～10 d or 6～15℃for 5 d or 15～25℃for less than 5 d.Therefore,the optimal temperature for lotus rhizome gas regulation storage was between 0℃and 4℃;vacuum multiplicity bag should be used for gas regulation package if the period for keeping fresh was about 60 d.After 60 d of gas regulation storage, the major nutritional ingredients changed a little:all the physiological and hygienical index attained the criterion of safe food and the number of bacteria and E.coli were below 103 every 100 gram and 3 every 100g,respectively.That indicated that storage under 0～4℃could meet the request of lotus rhizome storage.