Study On The Extraction And Stability Of Onion Essential Oil Rish In Thiosulfinates

The onion essential oil has many biological activities and these physiological effects attribute to the organic sulphuric compound, specially thiosulfinates(TS) it contained. TS content in onion essential oil is the key index to evaluate the onion essential oil extracting technology.The primary goal of this thesis is to develop a new technology with which to extract onion essential oil with as more TS content as possible. Both the onion essential oil recovery rate and TS content in this oil are selected to screen the optimal technology, The author also studied the storing conditions in order to protect the TS in onion essential oil.The main task of this work included the following three aspects:First of all, method for quantitative detection of effective component in onion essential oil was established:the author tried to detect the TS content of onion essential oil via spectrophotometry determination brought up by Lawson Larry.After some necessary improvement and calibration, the optimal determining conditions were described as follows:reacting temperature,20～30℃; the pH of the reacting system,7.5～8.5; the period of the reaction decreased from 15min to 5min. With the above improvements, the TS determining method became much more easy and convenient, the accuracy was also improved.Next, extracting technology of high quality onion essential oil was brought:in order to overcome the shortcomings of traditional onion essential oil extraction which resulting in S-alkyl-L-cysteine sulfoxides transforming into lachrymatory factor because of alliinase and lachrymatory factor synthase. the author tried to inactivate the lachrymatory factor synthase in the onion before it is crushed, and then, some exogenous alliinase was added in order to accelerate the synthesizing of TS. The optimal onion essential oil extracting conditions were drawn via single factor screening and orthogonal tests and it was described as follow:. yellow onion was better than red onion, extracting solvent should be methylene chloride, the amount of extracting solvent used should be 40mL/100g fresh onion and the solid-liquid ration was 1:1.5, the period of enzyme inactivation was 20min in boiling water. Then, garlic juice (5g garlic/100g fresh onion) was added to supply alliinase for TS synthesize and the enzymatic reaction should be kept at 25℃for 50min. The yield of onion essential oil was 0.921g/1000g onion and TS content in this oil was up to 71.3%.The storing conditions for onion essential oil was established:the author studied the influence of atmosphere (vacuum), light and storing temperature on the stability of onion essential oil. The optimal storing conditions were obtained:The vacuum-packed onion essential oil was stored at-20℃for 100 days, the retention of TS is 78.09%.