Effects Of Brassinolide And UV-B Radiation On Physiological Characteristics,Nutritional Components And Shelf Life Of Small Black Bean Sprouts

Sprout vegetables are rich in nutrition.It has become one of research hotspots to improve its quality by technical methods such as CaSO₄ sprayded.Meanwhile,the postharvest physiological metabolism in sprouts is vigorous because of the high water content,so the sprouts are susceptible to decay,which limits the postharvest storage and long-distance transportation of sprouts.Therefore,the preservation of postharvest sprouts is one of the most urgent problems in industry.The paper,the seeds of Inner Mongolia flat yellow core black bean as materials,explored the effects of soaking concentration and time of brassinolide?BR?and ultraviolet-B?UV-B?radiation on physiological characteristics,nutritional composition and the shelf life of small black bean sprouts.It further broadened the filed of the specific application of BR and UV-B radiation on sprout vegetable,and this will provide certain theoretical evidences for the production and postharvest preservation technology of small black bean sprouts.The results are as followed:1.Effects of BR soaking concentrations on physiological characteristics and nutritional quality of small black bean sprouts.The experiment included seven levels of BR treatments:0,0.01,0.2,0.5,1.0,1.5 and 2.0 mg L^-1.The seeds of small black bean were soaked in different concentrations of BR for 24 h.The results showed that the lower concentration of BR(0.01and 0.2 mg L^-1)significantly increased the contents of photosynthetic pigments,free amino acids,vitamin C,flavonoids,anthocyanins(except for 0.01 mg L^-1)and total phenolic(except for 0.01 mg L^-1)in sprouts,but soluble sugar content was significantly reduced in sprouts?P<0.05?.The phenylalanine ammonia-lyase?PAL?activity,flavonoids,total phenols,anthocyanins(except for 0.5 mg L^-1),free amino acids(except for 2.0 mg L^-1)and soluble sugar content were markedly enhanced in small black bean sprouts under the higher concentrations of BR treatments(0.5-2.0 mg L^-1).Furthermore,sprouts with the higher concentration treatments had more contents of flavonoids,total phenolic,anthocyanins and soluble sugar than those treated with the lower concentrations.2.Effects of BR soaking time on nutritional quality of small black bean sprouts.The experiment included two BR concentrations(0.2 and 1.5 mg L^-1)and five soaking times?6,12,24,36 and 48 h?.The results indicated that the low concentration BR(0.2 mg L^-1)significantly increased the content of flavonoids?except for 24 h?and free amino acids?except for 6 h?in small black bean sprouts compared with the high concentration BR(1.5 mg L^-1)?P<0.05?.In addition,the total phenolic content was markedly enhanced by the low concentration of BR at the short time soaking?6 and 12 h?.However,the high concentration BR treatments could obtain the higher content of total phenolic?except for 6 and 12 h?,anthocyanin,soluble sugar and vitamin C,and the activity of PAL.The comprehensive analysis showed that the optimal soaking concentration was 1.5 mg L^-1,and the optimal soaking time was 24-36 h under the conditions of the experiment.3.Effects of BR soaking time on the shelf life of small black bean sprouts.In this experiment,the 0.2 and 1.5 mg L^-1 BR were used to soak seeds for 6,12,24,36 and 48 h,respectively.The results suggested that the high concentration BR(1.5 mg L^-1)remarkably increased the content of total chlorophyll?except for 36-48 h?,anthocyanin,total phenolic?except for 6 h?,soluble sugar and vitamin C?except for 12 h?as well as the activity of PAL in stored small black bean sprouts when compared to the low concentration BR(0.2 mg L^-1)?P<0.05?.However,low concentration BR treatment could obtain the higher content of carotenoid?except for 12 h and 48 h?,flavone?except for 24-48 h?and the DPPH radical scavenging rate?except for 24-36 h?.The comprehensive analysis indicated that the optimal BR soaking concentration was 1.5 mg L^-1,and the optimal soaking time was 24 h to maintain a higher nutritional quality of small black bean sprouts during storage.4.Effects of BR soaking and preharvest UV-B radiation on the shelf life of small black bean sprouts.The experiment included four treatments:?1?the small black bean seeds were immersed in distilled water for 24 h?CK?,?2?the seeds were immersed in 1.5 mg L^-1 BR for24 h?BR?,?3?the seeds were immersed in distilled water for 24 h and the sprouts were exposure to UV-B before harvested?UV-B?,?4?the seeds were immersed in 1.5 mg L^-1 BR for 24 h and the sprouts were exposure to UV-B before harvested?BR+UV-B?.The results suggested that BR,UV-B and BR+UV-B treatments could significantly improve the storage property of small black bean sprouts.BR soaking alone observably increased the contents of vitamin C and soluble sugar,and markedly decreased the malonaldehyde?MDA?content of small black bean sprouts when compared with the control stored for 5 d?P<0.05?.Furthermore,the combined treatment of BR soaking and UV-B radiation,compared with BR alone,significantly enhanced the flavone,free amino acid and photosynthetic pigment contents as well as the activities of DPPH radical scavenging rate and PAL in small black bean sprouts after 5 d of storage.Meanwhile,the combination increased the contents of anthocyanin?without significance?and total phenols and PAL activity as well in comparison with UV-B alone.The combination also reduced MDA content of small black bean sprouts.In addition,the combination also significantly enhanced the maximum quantum efficiency of PSII?F_v/F_m?,the effective quantum yield of PSII?Y?II??and the photochemical extinction coefficient?qP?in sprouts while markedly lessened the initial fluorescence?F0?,the non-photochemical quenching of photosystem?NPQ?,?Y?NO??and the quantum yield of regulated energy dissipation?Y?NPQ??.The combined treatment of BR soaking and UV-B radiation could be used to preserve the postharvest small black bean sprouts with higher levels of both nutritional ingredient and DPPH radical scavenging activity after comprehensive analysis.