Effects Of Ultrafiltration On Physicochemical Parameters And Antioxidant Activities In Jujube Juice

In the process of jujube juice production and storage, it's easy to find the phenomenon of turbidity or deposition which affecting not only the sensory quality but also the warranty period. Therefore, it is very important to take measures to protect jujube juice from turbidity and deposition during processing. The treatment of clarify is one of the key processes to prevent the turbidity and deposition. This article mainly studies the impact of ultrafiltration on physical, chemical parameters, stability of jujube juice, and composition of sediment,as well as the antioxidant activity of jujube juice. The work includes the following five parts:1. It could be found that ultrafiltration affected the physical parameters of jujube juice by analyzing the turbidity, light transmission rate, density, viscosity, the value of L/a/b and the index of browning after ultrafiltration, with the decreases of MWCO (molecular weight cut off) by ultrafiltration membrane, the turbidity, density, viscosity, browning index all had a declining trend,while the light transmission rate increased.In the value of L/a/b, the value of 'L','b'increased, and the value of 'a' decreased, and no significant effect was found on soluble solids.2. Examined the effects of ultrafiltration on the chemical composition of jujube juice, results suggested that:ultrafiltration can effectively reduce the jujube juice in protein and polyphenol content.Besides,the process of ultrafiltration was also found to contribute to the amount of total sugar, reducing sugar, total Vc, prototype Vc, titratable acid methyl furfural and hydroxide methyl furfural content. With the decrease of MWCO, declines occurred in all chemical composition of jujube juice content although at different rates.3. Analyzed the component of sediments in jujube juice, it can be found that jujube juice sediments mainly consisted of protein, polyphenols, sugar and a small amount of pectin, the component and content of the amino acids in the protein were also examined.4. Studied the impact of ultrafiltration on antioxidant capacity of jujube juice by using in vitro method.Declines were observed in the ability to deoxygenate, DPPH radical scavenging activity, the ability to complex with Fe2+, and the ability to protect hydroxyl radical oxidative damage DNA of jujube juice after ultrafiltration though at different rates.Meanwhile the more MWCO decreases, the more obvious the downward trend was.5. Analysis of the samples' storage stability under room temperature both before and after ultrafiltration, jujube juice showed better stability during storage after ultrafiltration at 30K and 10K.