Preparation,Biological Activity,and Stabilization Of Gardenia Yellow Pigment

Gardenia yellow pigment was widely used in food additives and industrial dyes as a natural,safe,and healthy food coloring.The demand for it at home and abroad is increasing day by day,and the market prospect is broad.However,the traditional preparation process of gardenia yellow pigment was complicated,the yield and color value were low,and its main components were still unclear.Moreover,there are few reports on the biological activity of gardenia yellow pigment.Based on these,in this paper,gardenia fruit was taken as the research object,and systematic researches on the efficient enrichment,structure characterization,biological activity,and stabilization of gardenia yellow pigment were carried out,which provided a theoretical basis for the development and utilization of gardenia yellow pigment.The main findings were as follows:（1）The extraction of gardenia yellow pigment by traditional solvent extraction method,ultrasonic-assisted method,and ultra-high pressure-assisted method was compared,and the extraction process parameters of gardenia yellow pigment were optimized by the method of Box-Behnken response surface analysis.The results indicated that the optimal process conditions for extraction of gardenia yellow pigment by ultra-high pressure-assisted method were:pressure of 100 Mpa,ethanol mass concentration of 47.78%,extraction time of 114.95s,liquid-solid ratio of 18.08 m L/g.The extraction yield of gardenia yellow pigment was 7.73mg/g DW,which was significantly higher than that of traditional solvent extraction method（3.55 mg/g DW）and ultrasonic-assisted extraction method（4.81 mg/g DW）.The ultra-high pressure-assisted method is expected to replace the traditional solvent extraction method to prepare gardenia yellow pigment and improve the production efficiency of gardenia yellow pigment.（2）The gardenia yellow pigment was separated and purified by macroporous resin chromatography,and the main components of the purified gardenia yellow pigment were analyzed by LC-TOF-MS/MS technology.The optimal process conditions for purifying gardenia yellow pigment by X-5 resin were screened out as follows:the concentration of sample loading was 1.5 mg/m L,the flow rate of sample loading was 1.0 m L/min,the flow rate of desorption was 3.0 m L/min,and the mass fraction of ethanol was 80%.After purification,the color value of gardenia yellow pigment was 498.34,which was 8.6 times higher than that of the crude extract（57.84）.Fifteen main compounds in gardenia yellow pigment were identified,and crocins were the main component of gardenia yellow pigment,accounting for 47.09%.（3）The antioxidant activity of gardenia yellow pigment was systematically evaluated,and the immunomodulatory effect and mechanism of gardenia yellow pigment on macrophage RAW264.7 were also investigated.The results indicated that the antioxidant activity of gardenia yellow pigment was stronger than Vc,and its IC₅₀ values of 1,1-Diphenyl-2-trinitrophenylhydrazine free radical（DPPH·）,2,2-hydrazine-bis（3-ethylbenzothiazole-6-sulfonic acid）radical（ABTS+·）,and hydroxyl radical（·OH）scavenging ability were 0.44,0.07,0.09 mg/m L,respectively.When the mass concentration of gardenia yellow pigment was 0.01-0.11 mg/m L,the FRAP value was 0.19-1.65 m M Fe SO₄.Moreover,the gardenia yellow pigment could significantly promote the proliferation of RAW264.7 and enhance its phagocytic activity,promote the secretion of NO,TNF-α,IL-10,and COX-2,and increase the m RNA expression level of related cytokines.The results of this study can provide a theoretical basis for the application of gardenia yellow pigment in the field of functional food.（4）Five kinds of gardenia yellow pigment microcapsules were prepared by spray drying method with maltodextrin,gum arabic,soybean protein isolate,and whey protein as different wall material combinations,and their physicochemical properties,structure,and stability were studied.The results showed that the encapsulation efficiency and drug loading of gardenia yellow pigment microcapsules ranged from 58.73-83.16%and 1.63-3.32 g/100 g,respectively,and the encapsulation efficiency and drug loading of whey protein-maltodextrin（WP-MD）microcapsules were significantly higher than other microcapsules.Scanning electron microscope,Fourier transform infrared spectrometer,and X-ray diffraction analysis confirmed the successful entrapment of gardenia yellow pigment.Thermogravimetric analysis showed that the gardenia yellow pigment microcapsules had good thermal stability below 220℃.In addition,the five kinds of microcapsules could significantly improve the thermal stability,photostability,and p H stability of gardenia yellow pigment.The results can broaden the application scope of gardenia yellow pigment microcapsules in functional foods.