| In this study,20%mango juice was made by using Tainung No.1 mango.The composition and formation of sediment and color change during storage were studied.And the production process of mango juice was improved and optimized.The results were as follows:(1)The color change of mango juice showed a change from bright yellow to dark red in the early stage of storage.The(3 carotene is the main pigment providing the yellow part of color in mango juice.A small amount of lycoypene and procyanidine provide the traces red part of color in mango juice.The phenolic substances and ? carotene were oxidized gradually in mango juice,causing the yellow part of color to fade gradually and the black part of color to increase gradually,with the time of storage extending gradually.It's show the process of turning to dark red.The effects of oxygen in mango juice on color change during storage was excluded.Polyphenol oxidase are inactive completely after pasteurization,however the peroxidase still have a small amount of activity.In order to further verify that the oxygen is main reason affecting the color darkened of mango juice,oxygen content was controlled the only variable.The results show that the color of mango juice darken gradually with the increase of oxygen content,until it was oxidized completely and transparent.Further verification results showed that the color of mango juice becomes darker from top to bottom gradually,at this time,the only gas exchange channel is the mouth of the bottle in the glass container.It's show that the mango juice that is first exposed to oxygen have a more intense oxidation reaction,at this point,the color of mango juice at the top of the container sharp contrasts with the color of the mango juice at the bottom of the container.While the test group and the control group(strictly sealed)have the same sharp contrast.(2)The production rate of sediment in mango juice was 2.47%.The sediment of mango juice is flocculent structure,accounting for about 40%of the total volume.The contents and sorts of sediment were determined after freeze-drying.The main components of the sediment that is a hybrid system with spatial structure are starch and protein,and the spatial structure are filled with phenolic substances,pigments,monosaccharides,metal ion and volatile components.The density of the sediment was higher than that of the mango juice system,and natural subsidence occurs under the influence of gravity.Starch and protein were further verified as the main components by directional removal test,and the model of "starch-protein" sediment was established.In this part of study,it's found that(3)the presence of pectin is crucial to the stability of mango juice system.Single factor test results show that the reduction of pectin content will cause the mango juice system to collapse.As a result,small molecules including pigment occur natural subsidence along with large molecules,such as starch and protein,resulting in a transparent color on the upper layer of the juice.Increasing pectin content and hydrolyzing the starch of sediment makes the absolute value of Zeta potential of mango juice increase,which is conducive to the stability of mango juice system.(4)Formulation of mango juice process optimization single factor experiment based on previous theoretical analysis results.The color protection and stability of mango juice were tested respectively.The results showed that composite color protection agent is ideal for color protection of mango juice.According to the response surface methodology,the optimal color fixative ratio of mango juice are glucose oxidase concentration:30.29 mg/L,vitamin C concentration:0.73 mg/g,and calcium chloride concentration:0.41 mg/g.The agreement between the experimental value and the theoretical value is 95.14%.The stability of mango juice was adjusted by improving spatial stability of mango juice system and damaging internal sediment structure.The optimal results showed that the dosage of pectin is 0.15%and the dosage of ? amylase is 31500 U/100 g. |
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