Studies On The Processing Of Dehydrated Green Bean Sprouts And Its Qualities

Bean sprouts are a kind of favorite vegetables. In the processing of sprouting, someingredients which affected the flavor and nutrition are eliminated. In result, proteins andsugars are transformed to the other forms which could be absorbed easily. However, beansprouts are brittle and short in shelf life. This resulted in low profits in the manufactorycorporation. It is necessary to process it into profitable products, as well as provide morekinds of food into market. Utilizing the green bean sprouts as the main material, theprocessing technology of dehydrated bean sprouts were investigated, including ofblanching, crispness-keeping, maltodextrin preparation and hot-air drying. The nutrients ofdehydrated bean sprouts were investigated compared with fresh bean sprouts and greenbean. In the end, the change of sugar ingredients in bean sprouts bean sprouts wasinvestigated by HPLC. Results were shown as bellows:1. The study on techniques of preparation to bean sproutsIn order to eliminate soybean odor and inactivate the activity of peroxidase in beansprout, green bean sprouts were blanched in hot water. After being blanched, bean sproutswere soaked in CaCl₂ solution in order to keep their crispness. Then the bean sprouts weresoaked in maltodextrin, sucrose and NaCl mixture solution to improve the rehydration ofdehydrated bean sprouts. The results indicated that the activity ofperoxidase in bean sproutwas completely lost when it was blanched in 0.15% citric acid solution for 2.5 min at 90℃and the hexanal in it was obviously decreased. The crispness of bean sprouts was keptbetter after being soaked in 0.4% CaCl₂ for 60 min. The rehydration of dried sprouts wasoptimum when soaked in the mixture solution contained 10% maltodextrin, 15% sucroseand 10% NaCl for 30 minutes. 2. The study on technique of hot-air dryingIn this part, the technique of hot-air drying was investigated. The results showed that thequality of dehydrated sprouts was optimum when the air temperature was 60℃and theweight load was 0.7g/cm², based on a comprehensive score of recovery ratio of waterabsorption, rehydration rate, whiteness and drying time. Two drying curves of green beansprouts were made under different drying temperatures and loads.3. The study on the content of some nutrients in dehydrated bean sprouts and the sugaringredients by HPLCThe nutrients of dehydrated bean sprouts, green bean and flesh bean sprouts wereinvestigated, including the content of protein, fat, fibre, mineral, Fe and flavone. Theresults indicated that the contents of protein, fat, fibre in dehydrated bean sprouts were20.22%, 3.15% and 10.82%, more than green bean and fresh bean sprouts, and the contentof other nutrients were close to green bean.The sugar ingredients in bean sprouts after being soaked, being soaked and blanched,and dehydrated bean sprouts were investigated by HPLC. The chromatograms indicatedthat sucrose and maltose could permeate into bean sprouts or stick on it in soaking. Withthe help of NaCl, glucose and some kinds of polysaccharose could permeate into beansprouts or stick on it too. Sucrose took an important part in improving the rehydration ratioof dehydrated bean sprouts, as well as glucose, maltose and polysaccharose.