乳酸菌半固态发酵对沙田柚果粉苦味及活性成分的影响

Effects of Semi-Solid Fermentation with Lactobacillus on the Bitterness and Active Components of Shatianyu(Citrus grandis L.Osbeck)Fruit Powder

【目的】探究不同乳酸菌半固态发酵对沙田柚果粉苦味及活性成分的影响,建立沙田柚果粉的脱苦技术,制备富集黄酮和膳食纤维(DF)的低苦味沙田柚果粉,为沙田柚果粉在健康食品中的应用提供理论依据和技术支撑。【方法】分别对由沙田柚囊衣和果肉匀浆热风干制成的果粉及其中对应含量的主要黄酮糖苷(柚皮苷和melitidin)进行苦味评定,明确沙田柚果粉的苦味物质基础。分别采用植物乳杆菌(Lactobacillus plantarum GIM 1.1516,LP1.1516)、干酪乳杆菌(Lactobacillus casei GIM 1.411,LC1.411)、鼠李糖乳杆菌(Lactobacillus rhamnosus GIM 1.325,LR1.325)和嗜酸乳杆菌(Lactobacillus acidophilus GIM 1.731,LA1.731)发酵沙田柚匀浆,动态监测发酵过程中匀浆的还原糖含量、pH和酸度变化;采用高效液相色谱(high performance liquid chromatography,HPLC)分析发酵过程中沙田柚匀浆柚皮苷和melitidin降解率的变化,结合对发酵后匀浆的苦味评定,明确沙田柚匀浆最佳发酵脱苦条件。对发酵后干制的沙田柚果粉进行苦味评定,并分别测定发酵前后果粉总酚、总黄酮、总DF(TDF)、可溶(SDF)及不溶性DF(IDF)的含量,并评价其氧自由基吸收能力(oxygen radical absorbance capacity,ORAC)、铁离子还原能力(ferric reducing antioxidant power,FRAP)和ABTS自由基清除能力及持水力(water retention capacity,WRC)、持油力(oil adsorption capacity,OAC)和吸水膨胀力(water swelling capacity,WSC)。【结果】由沙田柚囊衣和果肉制备的果粉滋味较苦,苦味主要由其黄酮主组分柚皮苷和melitidin共同呈味引起。植物乳杆菌、嗜酸乳杆菌、干酪乳杆菌和鼠李糖乳杆菌在发酵沙田柚囊衣和果肉匀浆的前12 h,均可利用匀浆中还原糖并代谢产酸,但发酵12—24 h,只有鼠李糖乳杆菌可持续利用匀浆还原糖并代谢产酸;经鼠李糖乳杆菌发酵12 h沙田柚匀浆的柚皮苷和melitidin总降解率及感官脱苦率均最大,分别为41.1%和66.0%,此时干制成的果粉滋味由发酵前的较苦(苦度值5.64)降低至少许苦和稍苦之间(苦度值2.21),感官脱苦率可达60.8%。与发酵前相比,经鼠李糖乳杆菌发酵12 h后的沙田柚果粉总黄酮含量显著提高19.8%,IDF含量降低9.6%,SDF含量增加19.6%,但TDF含量无显著变化。此外,发酵后果粉的ORAC抗氧化活性提高24.1%,持水力和吸水膨胀力分别提高20.8%和32.0%。【结论】采用鼠李糖乳杆菌发酵沙田柚匀浆12 h可用于制备富集黄酮和DF的低苦味沙田柚果粉,该果粉可用于相关功能食品的开发。

【Objective】The effects of semi-solid fermentation with different lactobacillus on the bitterness and active components in Shatianyu(Citrus grandis L.Osbeck)fruit powder(SFP)were explored.The aim of the present study was to establish the debitterizing technology and prepare low-bitterness SFP enriched in flavonoids and dietary fiber(DF),for providing the theoretical basis and technical support for the application of SFP in healthy food.【Method】Shatianyu septum and pulp were dried and crushed to generate SFP,then,the bitterness of SFP and the equivalent main flavonoid glycosides(naringin and melitidin)in SPF were evaluated by sensory evaluation to clarify the bitter substance base.Lactobacillus plantarum GIM 1.1516(LP1.1516),Lactobacillus casei GIM 1.411(LC1.411),Lactobacillus acidophilus GIM 1.731(LA1.731)and Lactobacillus rhamnosus GIM 1.325(LR1.325)were used to ferment Shatianyu homogenate.During fermentation,the reducing sugar content,pH and acidity were dynamically monitored,the naringin and melitidin degradation rate were analyzed by HPLC,and the bitterness of Shatianyu homogenate after fermentation was also evaluated to determine the optimal fermentation conditions.Then,the fermented SFP was prepared,and its bitterness,together with total phenolic,total flavonoids,total DF(TDF),soluble DF(SDF),and insoluble DF(IDF)content were determined,respectively.Furthermore,the oxygen radical absorbance capacity(ORAC),ferric reducing antioxidant power(FRAP),ABTS free radical scavenging ability,together with water retention(WRC),water swelling(WSC),and oil adsorption capacity(OAC)of fermented SFP were determined,respectively.【Result】SFP exhibited a more bitter taste,which was mainly caused by the co-flavor of naringin and melitidin,the main flavonoid components in SFP.During the first 12 h-fermentation,LP1.1516,LC1.411,LA1.731 and LR1.325 could use the reducing sugar in the homogenate and produce acids,while during 12-24 h-fermentation,only LR1.325 could still use the reducing sugar and produce acids.Shatianyu homogenate fermented by LR1.325 for 12 h showed the highest total degradation rates of naringin and melitidin(41.1%),also showed the highest sensory bitter removal rates(66.0%).Compared with unfermented SFP,the taste of SFP prepared by 12 h-LR1.325 fermentation changed from bitterer to between little bitter and slightly bitter,with a sensory bitter removal rate of 60.8%.Furthermore,the later showed higher total flavonoid content(increasing 19.8%),lower IDF(decreasing 9.6%),and higher SDF content(increasing 19.6%).Also,SFP prepared by 12 h-LR1.325 fermentation showed higher ORAC antioxidant activity(increasing 24.1%),higher water retention(increasing 20.8%)and water swelling capacity(increasing 32.0%).【Conclusion】12 h-LR1.325 fermentation of Shatianyu homogenate consisting of septum and pulp generates low-bitterness SFP enriched in flavonoids and DF,which could be used in the development of related functional foods.