Investigation On Mechanism And Control Of Green Bean Sprouts Fresh-keeping

Green bean sprouts are rich in nutrients and low in price.Sales in the vegetable market are rising rapidly.However,green bean sprouts are extremely crisp,and shelf life is short.When green bean sprouts are harvested and saled,its safety and commodity value without proper treatment will greatly reduce.Green bean sprouts were used as experimental objects to study the mechanism affecting preservation efficacy and control method.The main research results are as follows:1.The sensory scores,hypocotyl microstructure and physicochemical indicators changes of green bean sprouts under different temperature were studied.Results showed that storage temperature was significantly correlated with freshness of green bean sprouts.Green bean sprouts hypocotyls showed obvious hollow structure.The worse the freshness of green bean sprouts was,the larger the hollow area was.Cellulose and pectin content of green bean sprouts were respectively related to activity of cellulase and pectinase(p<0.01).Cellulase and pectinase activities changes were important factors influencing the autolysis of green bean sprout cell wall.The changes of MDA content and relative membrane permeability were both correlated with sensory scores,indicating that the integrity of green bean sprouts cell membrane was closely related to preservation efficacy.In summary,the cell structure(including cell wall and membrane)integrity is an important factor affecting preservation efficacy.2.Ferulic acid and EDTA were used as enzyme inhibitors to treat green bean sprouts.Using sensory score and Vc content as indicators,the optimal treatment conditions for two enzyme inhibitors were obtained by orthogonal experiment:green bean sprouts were soaked in 0.1 g/L ferulic acid solution at 25? for 30 min,or in 0.1 g/L EDTA solution at 25? for 30 min.V_Ccontent,cellulose and pectin content of green bean sprouts treated by enzymes inhibitors were higher than control.Cellulase and pectinase activity were lower than control.And hypocotyl cavity area of green bean sprouts stored for 48 h was smaller than control.Ferulic acid and EDTA treatment could prolong shelf life of green bean sprouts at 25? for 24 h and 12 h,respectively.It is reasonable to explain that the technical route to prolong shelf life by inhibiting green bean sprouts cell wall hydrolase activity.3.Ascorbic acid and sodium dithionite were used as antioxidants to treat green bean sprouts.The optimum conditions for orthogonal optimization were as follows:green bean sprouts were immersed in 3 g/L ascorbic acid solution at 10? for 30 min,or soaked in 0.1 g/L sodium dithionite solution at 25? for 20 min.In preservation test,V_Ccontent,DPPH and hydroxyl radical scavenging rate of green bean sprouts treated with ascorbic acid and sodium dithionite were higher than control,and MDA content and relative membrane permeability were lower than control.The shelf life of green bean sprouts with ascorbic acid and sodium dithionite treatment at25? was extended for 12 h or 24 h than control,respectively.It shows that enhancing the antioxidant activity of green bean sprouts can help to protect cell membrane integrity,and promote preservation efficacy.4.In order to study the effect of endogenous antioxidants on green bean sprouts preservation,green bean sprouts were prepared by 0-1.0 mmol/L oxalic acid solutions.Green bean sprouts prepared by 0-0.6 mmol/L oxalic acid solutions were stored.Results showed that green bean sprouts prepared with oxalic acid solution could increase V_Cand total phenol content during harvesting.The content of V_Cand total phenol of green bean sprouts with 0.6 mmol/L oxalic acid solution treatment was the highest,which was 68.3%,or 50.0%higher than that prepared by distilled water,respectively.In preservation experiment,the higher the V_Cand total phenolic content were,the better the preservation efficacy was.The shelf life of green bean sprouts with 0.4 or 0.6 mmol/L treatment oxalic acid solution was extended by 12 h or 24 h,respectively.It shows that shelf life of green bean sprouts can be extended by increasing the endogenous antioxidant content.5.The effects of green bean sprouts prepared by oxalic acid solution treated with ferulic acid on preservation and related physicochemical indicators were studied.Results showed that shelf life of green bean sprouts with 0.6 mmol/L oxalic acid solution and ferulic acid was extended by 36 h,reducing the loss of V_Ccontent in green bean sprouts during storage,inhibiting activity of cellulase and pectinase,maintaining cell wall integrity,alleviating the degree of membrane lipid oxidation of green bean sprouts,and protecting the cell membrane.Compared with two treatments alone,shelf life of green bean sprouts with combined treatment was extended by 12 h,indicating that shelf life of green bean sprouts prepared by oxalic acid solution combined with ferulic acid treatment had a significant synergistic effect.