| As polyphenols they have a great impact on non-biological stability and oxidantresistance of beer. Procyanidins in beer mainly come from malt and hops. And procyanidinsare recognized as the most effective free radical scavenger in human body around the world,to be good for human health too.In this study, in order to investigate the properties of procyanidins, extraction andpurification methods of procyanidins from malt were established. Firstly, I optimized theorganic solvent extraction conditions, then the organic extract solution was purified by AB-8macroreticular resin, the purification conditions were researched through adsorption anddesorption experiment. The optimum conditions of organic solvents extraction were asfollows:60%ethanol (v/v) as the solvent, extraction temperature85°C, the ratio of solvent tomaterial at25:1(v/w), extraction time1.5h, pH=4-5. The most suitable adsorption conditionswere: sample concentration0.57mg·mL-1, and flow velocity0.5mL·min-1. And thedesorption conditions were:60%ethanol (v/v), flow rate1mL·min-1, elution volume65mL.The recovery efficiency can be reached95.24%.Take two kinds of malt and three kinds of hops as raw material, to compare theprocyanidins from malt and hops. The experiment contents include the comparison ofprocyanidins content, comparison of radical scavenging activity, and comparison of monomercomposition. Experimental results were as follows: The content of procyanidins in hops wasfar higher than that in the malt; The procyanidins from malt and hops both had scavengingactivity to DPPH·, while hop procyanidins has the better effect than malt procyanidins. Theeffect of scavenging was obvious in the beginning30mins, after this period the reactiongoing gradually smooth, until reached equilibrium in80-90mins; To analysis the averagedegree of polymerization and monomer composition of procyanidins throughthiolysis-RP-UPLC-MS, I found that the main composition units of hop procyanidins wascatechin(>70%), followed by epicatechin(>10%), gallocatechin(<5%). While the maltprocyanidins were mainly composed with catechins(>60%), secondly was gallocatechin(>25%), epicatechin(<4%) was last. After that the RP-UPLC-MS was used to analysisprocyanidins in beer which was fermented by Australian malt and polyphenol particle hops,there were two kinds of monomers and9kinds of dimmers detected.The procyanidins from polyphenol particle hops were classified according to averagedegree of polymerization through AB-8resin. Afterwards, I got five components withdifferent mDP. Then, the antioxidant properties of these five components were measuredtaking catechin and ascorbic acid as control. And the result was shown below. The samples allcould scavenge DPPH·radical, and the effect in order were: five components with differentmDP> catechin> VC. At the same time, the scavenging ability has nothing to do with mDP.The results of reducing ability were as follows: mDP=2.7>(+)-catechin> mDP=4.2>mDP=7.2> mDP=9.9> mDP=12.8> VC. Procyanidins with different mDP could inhibit theoxidation of linoleic acid, and the inhibition had a certain concentration effect. Besides,arranging the samples according inhibition effect as follows: mDP=2.7> mDP=4.2> mDP=7.2>(+)-catechin> mDP=9.9> mDP=12.8> VC. In liposome system, there was also hadsome relationship between the inhibition of the peroxidation of lipid and mDP ofprocyanidins, the inhibition effect increased with the decrease of mDP. At the same time, theinhibition of (+)-catechin was superior to component which mDP=7.2, and similar tomDP=4.2. While, VChad the worst effect. |
PDF Full Text Request