Study On Extraction And Microencapsulation Of Sulforaphane From Broccoli Seeds And Sprouts

Sulforaphane(SF)is a water-soluble natural product with various functions such as anti-oxidation,bacteriostasis,anti-cancer,anti-inflammatory and immune enhancement.Broccoli seeds and sprouts are rich in SF,which can be used as the raw materials of functional food.However,SF is extremely unstable,highly heat-sensitive,and rapidly metabolized or excreted in the human body,resulting in the very limited amount of SF obtained from food.Therefore,an urgent problem need to be solved is how to achieve high-value utilization of SF and its raw materials at present.In this study,the SF,total phenolic(TP),total flavonoid(TF)and antioxidant activities in broccoli seeds and sprouts(3,5,7 d)of six cultivars were compared.On the other hand,SF nanoparticles and microspheres were prepared by electrospraying to improve its stability and release properties.The research results provide data support and theoretical basis for the development and utilization of broccoli seeds and sprouts with abundant SF as raw materials of functional food.The main research contents and results are as follows:The optimal extraction conditions of SF from broccoli seeds and sprouts were obtained by response surface methodology.Based on optimized extraction conditions and established comparison method,it was clear that higher SF yields could be obtained from seeds than sprouts.SF contents in sprouts were 46 % to 97 % of seeds,whereas TP and TF contents in sprouts were 1.12 to 3.58 times higher than seeds among six cultivars.The variety MNL with highest active ingredients was selected for in vitro gastrointestinal digestion(GID)experiments,and the results showed that the content of SF,TF,TP and antioxidant capacity of 3 d sprouts were higher than that of seeds during in vitro digestion.Five kinds of Uniaxial/coaxial nanoparticles were prepared with SF extracted and purified from MNL seeds as the core material and Zein,Gelatin(Gel),and Chitosan(CS)as wall by electrospraying.The characteristics of nanoparticles were characterized by scanning electron microscopy(SEM),flourier transformation infrared spectroscopy(FT-IR)and thermogravimetric analysis(TG)and SF thermal stability and release properties were investigated.The results showed that nanoparticles had high encapsulation efficiency for SF,and its stability was significantly improved.Compared with free-form SF,the cumulative release rate of SF of five kinds of nanoparticles in 10% ethanol,3% acetic acid and GID was relatively stable.In addition,the broccoli sprouts extract(BSE)containing SF,TF and TP was obtained from MNL sprouts after 3 days germination.The nanoparticles prepared according to the method described above had higher encapsulation efficiency for SF and TP.In vitro GID experiments showed that the encapsulation of nanoparticles could effectively reduce the degradation of SF and TP during the digestion process.In order to further improve SF sustained release property,Alg-CS-Zein-SF microspheres were prepared by electrospraying technology with adding Zein-SF nanoparticles to the alginate/chitosan microsphere systems.The optimum conditions were as follows: voltage 16 k V,CS concentration 0.5%,and flow rate 10 m L/h.Under these conditions,the encapsulation efficiency and loading capacity were 85.16% and 2.36 mg/g respectively.The cumulative release rate after in vitro GID for 8 hours was 75.1%,which indicated that the Alg-CS-Zein-SF microspheres had a very good sustained release effect.Alg-CS-Zein-BSE microspheres were prepared by the above methods,SF and TP were mainly released in the intestine during the in vitro GID,and at the same time exhibited high antioxidant capacity.