| Shatianyou(Citrus grandis L.Osbeck),one of the characteristic fruits in South China,is the key pomelo variety developed in China.It is reported that pomelo peel is an important source of flavonoids and dietary fiber(DF).Our preliminary study found that Shatianyou pulp was rich in flavonoids and DF,and its flavonoids and DF showed synergistic effect on improving high fat diet-induced metabolic syndrome in mice,suggesting that the Shatianyou fruit powder(SFP)can be used as an important functional ingredient for developing healthy food for people with obesity-related metabolic diseases.However,the septum of pomelo tastes bitter,which might restricts the application of SFP as a functional ingredient in healthy food.Thus,this paper intends to(1)systematically analyze the compositions and activities of flavonoids and DF in different parts of Shatianyou;(2)Compare the effects of hot air drying and freeze drying on the compositions and activities of flavonoids and DF in SFP to determine its drying technology;(3)Prepare SFP,which is rich in flavonoids and DF,by removing bitterness of SFP through solid-state fermentation with lactobacillus.The main results are as follows:(1)Compositions and activities of flavonoids and dietary fiber in different parts of Shatianyou: There were significant differences in compositions of flavonoids and DF in flavedo,albedo,septum,pulp and seed of Shatianyou.The contents of total phenols,flavonoids and total DF(TDF)in Shatianyou were 1.39-4.61 mg GAE/g FW,1.08-10.14 mg CE/g FW,and 16.41-75.81 g/100 g DW respectively.Albedo and septum had the highest contents of total phenols,flavonoids and TDF.Naringin and melitidin were the main flavonoids in different parts of Shatianyou,accounting for 40%-62% of the total flavonoid contents.Furthermore,flavonoids and DF of albedo and septum showed stronger antioxidant activities and physicochemical properties(water retention,oil adsorption and water swelling capacity).Therefore,Shatianyou,especially the albedo and septum,are good sources of flavonoids and DF.(2)Effects of different drying methods on the compositions and activities of flavonoids and dietary fiber in SFP: SFP was prepared by hot-air drying and freeze-drying,which was from the pulp and septum remained after the juice was squeezed.Results showed that the contents of total phenols(5.54 mg GAE/g DW)and total flavonoids(13.11 mg CE/g DW),together with the antioxidant activities of SFP prepared by hot-air drying were higher than those prepared by freeze drying.Naringin and melitidin were the main flavonoids in SFP.The TDF contents and physicochemical properties of SFP prepared by hot-air drying(46.10 g/100 g DW)was higher than those prepared by freeze drying(P<0.05).Therefore,hot-air drying was more suitablle for preparing SFP rich in flavonoids and DF.(3)Bitterness evaluations of SFP and its debittering study by solid-state fermentation with lactobacillus: SFP prepared by hot-air drying tasted bitter,and naringin and melitidin were the main bitter compounds.Four kinds of lactobacillus were used to fermentate Shatianyou pomace.Lactobacillus rhamnosus fermentation for 12 h had the best debittering effect on pomace,in which the degradation rate of naringin and melitidin,together with the sensory deprivation rate of bitterness were 22.59%,19.35% and 65.97%,respectively.The total phenols(5.54 mg GAE/g DW),flavonoids(13.11 mg CE/g DW),and TDF contents(46.93 g/100 g DW)were improved after debittering.In conclusion,the debittered SFP with better flavor is rich in flavonoids and DF,and is suitable for the development of functional food. |
