Change And Regulation Of Allergen During Peanut Seed Germination

Peanut（Arachis hypogaea L.）,which is a family of Papilionaceae,belongs to the genus Arachis Linn.Peanut seed oil is an important oilseed in the world.Peanut seed is rich in fat,protein and amino acids.Among oilseeds,peanut protein is regarded as excellent source of protein,due to its high nutrition level,low content of anti-nutritive components and easily-digestive property.Therefore,it plays an important role in maintaining human health and promoting the growth of young children.Peanut protein has been suggested as an alternative protein source to the traditional one in developing countries where protein deficiencies remain a major health problem.However,peanut is one of the eight major allergenic foods,since its protein is antigenic.Peanut consumption may lead to the occurrence of anaphylactic reactions or even death.Currently,the studies about reducing the contents of allergic components in peanut have been widely concerned.In this thesis,the changes of physiochemical properties and allergen contents of peanut seed during germination were monitored.The effects of both trypsase and metal ions on physiochemical properties and allergen contents of peanut seed during germination were also investigated.Besides,the influences of different thermal treatment methods on soluable protein and allergen（Ara h 1）contents in peanut were studied.The main results are shown as follows:peanut seeds（variety H-25）were first soaked in deionized water in darkness at 30 ℃ for 12 h.After that,peanut seeds were treated by water spraying at the same conditions until the end of germination（96 h）.The contents of protein and Ara h 1 in peanut seeds were measured after germination for 24,48,72 and 96 h.The results showed that the protein profile of peanut changed significantly after germination.The degree of hydrolysis reached 15.01%after germination for 96 h.The SDS-PAGE pattern revealed the disappearance or loss of density from the conarachin（50～66 kDa）and acidic arachin（38～49.9 kDa）bonds,as well as the appearance of a series of sub-units with smaller molecular weight（<18 kDa）.The activities of neutral and alkali proteases reached the peak values after germination for 72 h,while acid protease was the most active after germination for 96 h.Furthermore,after germination for 72 h,the contents of proteins with molecular weights of 60 KDa and 43 KDa decreased significantly,particularly for Ara h 3.As for Ara h 1,its content also decreased after germination for 72 h.But the existence of Ara h 1 could not be neglected.The concentrations of trypsase were set at 0.05%（w/v）,0.1%,0.15%and 0.2%for the enzymatic treatments during peanut germination.Peanut seeds were treated by enzyme maceration（EJ）,enzyme spraying（EP）and the combination of enzyme maceration and enzyme spraying（EJP）,respectively.For EJ treatment,peanut seeds were first soaked in enzyme solution for 12 h,and then treated by water spraying.For EP treatment,peanut seeds were first soaked in deionized water and treated by enzyme spraying.For EJP treatment,peanut seeds were first soaked in enzyme solution and then treated by enzyme spraying.The best enzyme treatment to reduce the allergen contents in peanut seed during germination was selected by monitoring the changes of peanut physiochemical properties and contents of solvable protein and allergens.For peanuts treated by EJ,the peanut shoots kept growing during germination between 24-96 h.After 96 h germination,lateral root appeared and the wooden structure can be easily observed.In the meantime,the appearance of peanut seeds treated by EJ after 72 h germination was beautiful.In general,0.15%EJ treatment resulted in minimum inhibition on peanut shoot,high reservation of soluble protein and decrease of allergen Arah 1 content.Furthermore,according to the Western-blot results,the relative optical density of Ara h 1 in the EJ-treated sample germinated for 72 h was 84.78%of the control sample.On the other hand,both EP and EJP treatments can inhibit the germination of peanut seeds,to a certain extent.As a result,the best enzymatic treatment was the 0.15%EJ treatment,while the 0.05%EJP treatment can also be acceptable.Metal ions with various concentrations,including Na⁺,Mg²⁺,Ca²⁺,were also added during peanut seed germination.The peanut physiochemical properties,as well as the contents of soluble protein and allergen,were measured,so as to optimize the metal ion treatments.It was found that the effects of metal ion on the peanut physiochemical properties and contents of soluble protein and allergen during germination depended on the type of metal ions.The optimal metal ion concentrations added were 5 mM for Na⁺,10 mM for Mg²⁺ and 15 mM for Ca²⁺.Under these mentioned conditions,the seeds were characterized by longer shoot length,higher soluble protein content and lower allergen content than other samples after germination for 72 h.Different thermal treatments（including poaching,frying and roasting）were performed after peanut seed germination for 72 h.Poaching treatment at 80～100 ℃for 45～60 min was regarded as the suitable poaching treatment,since the soluble content was high and the Arahl content was relatively low.The toasting treatment at temperatures higher than 120 ℃ resulted in the increase of Ara h1 content,while toasting at 120 ℃ did not change the Ara h1 content significantly.For the samples treated by frying at 130～155 ℃ within 15 min,the Ara h1 content is relatively lower than other samples and the loss of soluble protein was also low.Therefore,the mentioned frying condition can be used in the practical applications.