Preparation And Performance Evaluation Of Composite Cyclodextrin Inclusion Complex Based On ?-acids-lycopene

Hops are one of the raw materials for beer brewing,which can give beer special bitterness,unique flavor and antibacterial and antiseptic function.Its main components are?-acids and?-acids.The main source of beer bitterness is?-acids,while?-acids has the ability to coordinate beer flavor,make up for insufficient bitterness and obvious antibacterial activity.As a natural preservative source,?-acids has a weak bitterness,and its stability is poor.It will be oxidized and degraded into a derivative with strong bitterness,so it can not be directly used in food system.Lycopene,as a natural fat-soluble pigment,has strong antioxidant activity and many benefits to human body.However,it has poor stability and insoluble in water,that make it difficult directly add to water-based foods.This paper firstly evaluated the synergistic antioxidant properties of natural pigment lycopene and various active ingredients in hops(hops extract,?-acids,?-acids and hexahydro?-acids),and the synergistic effect of?-acids and lycopene compound system was the strongest.In order to improve the water solubility and stability of the active ingredients,hydroxypropyl-?-cyclodextrin(HP-?-CD)is used as the host molecule,?-acids and lycopene are the guest molecules to prepare?-acids-lycopene/HP-?-CD composite inclusion compound,using ultraviolet spectrum(UV-Vis),Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),scanning electron microscope(SEM),nuclear magnetic resonance hydrogen spectrum(¹H NMR)characterizes the structure of the formed complex clathrate,and the water solubility of?-acids and lycopene in the composite inclusion compound was determined.Single factor combined with orthogonal experiment was used to optimize the optimal process conditions for the preparation of?-acids-lycopene/HP-?-CD composite inclusion compound by grinding method,and then the stability,antioxidant activity and antimicrobial activity of the composite inclusion compound aqueous solution were explored.The prepared?-acids-lycopene/HP-?-CD composite inclusion compound was added to the composite fruit and vegetable juice to investigate its fresh-keeping effect in the water-based food system.The main work and conclusions are as follows:1.The antioxidant activity of single solution of natural lycopene and hops active ingredients(hops extract,?-acids,?-acids and hexahydro?-acids)was evaluated.Then,the synergistic antioxidant properties of mixture solutions of lycopene with hops extract,?-acids,?-acids and hexahydro?-acids were determined and the stability of mixture solutions at different temperatures and under ultraviolet irradiation for different time.The results showed that the IC₅₀ of lycopene,hops extract,?-acids,?-acids and hexahydro?-acids were 8.73,29.60,10.80,35.60 and 179.00 mg/L,respectively.And lycopene had the strongest DPPH·scavenging activity in single solution system.When the mass concentration of lycopene was 4 mg/L,with the active ingredients of hops at low to medium ratio,the synergistic antioxidant effect of each mixture solution was in order lycopene/?-acids>lycopene/hexahydro?-acids>lycopene/hops extract>lycopene/?-acids.Under different temperatures,the stability of?-acids and lycopene in the lycopene/?-acids compound system was improved to varying degrees compared with?-acids single-component solution and lycopene single-component solution.In addition,the change rate of the absorbance value of each compound system was maintained at more than 80%after 10 h of ultraviolet irradiation,showing excellent stability.2.The?-acids-lycopene/HP-?-CD composite inclusion compound was prepared by grinding method,and its solubility in aqueous solution was measured,and its structure was analyzed by UV-Vis,FT-IR,XRD,SEM and ¹H NMR.The results showed that the?-acids-lycopene/HP-?-CD composite inclusion compound was successfully formed,in which the water solubility of?-acids can reach 3.47 mg/m L and lycopene can reach0.53 mg/m L.In the ultraviolet spectrum,the aqueous solution of?-acids,lycopene,and HP-?-CD has no obvious absorption in the range of 200-700 nm.The ultraviolet of?-acids-lycopene/HP-?-CD composite inclusion compound is similar to?-acids in methanol solution;it can be found in the infrared spectrum that the-OH stretching vibration absorption band of?-acids in the composite inclusion compound is broadened,and the stretching vibration absorption peak intensity of C-H bond and C=O bond was obviously weakened,and the characteristic absorption peaks of lycopene(1024 and 958cm^-1)disappeared;in the X-ray diffraction pattern of the composite inclusion compound,the characteristic diffraction peaks of?-acids and lycopene have disappeared,and the diffraction pattern was different from?-acids,lycopene,HP-?-CD and their physical mixtures;the microstructure of the complex was significantly different from that of the?-acids,lycopene,HP-?-CD and the physical mixture under SEM,the long solid morphology of?-acids,the sheet solid morphology of lycopene and the hollow spherical structure of HP-?-CD had all disappeared;¹H NMR spectra also showed that the composite inclusion compound was successfully formed.3.The preparation process of?-acids-lycopene/HP-?-CD composite inclusion compound was optimized by single factor combined with orthogonal experiment.The optimal preparation conditions were as follows:mass ratio of host-guest molecular1:1:80,the grinding temperature was 30? and grinding time was 75 and 90 min.Under these conditions,the inclusion rate of?-acids and lycopene in the?-acids-lycopene/HP-?-CD composite inclusion compound can reach 82.31±1.46(%)and 42.77±1.11(%).The results of stability experiments show that:(1)When stored under natural light and in the dark for 16 days,the preservation rate of?-acids in the aqueous solution of the composite clathrate can reach more than 50%,and the lycopene also showed good photostability.(2)With the increase of temperature,the stability of the complex clathrate aqueous solution gradually decline,and the preservation rate of?-acids can reach more than 95%after 12 h in the temperature range of 10-40?,in the temperature range of 50-90?,the preservation rate of?-acids can still achieve 70%above after 12 h.In addition,the aqueous solution of lycopene also showed good thermal stability.(3)The compound stable under neutral or alkaline conditions.(4)The activity of scavenging DPPH·of the compound can reach more than 80%.(5)The composite inclusion compound has varying degrees of inhibitory effects on Escherichia coli,Salmonella,Staphylococcus aureus,Listeria monocytogenes and Bacillus subtilis.The best inhibitory effect is against on Escherichia coli,with the minimum inhibitory concentration of 37.5?g/m L.4.The prepared?-acids-lycopene/HP-?-CD composite inclusion compound was applied to the preservation of composite fruit and vegetable juice.The results showed that the addition of compound inhibited the growth of microorganisms to a certain extent,0.075%concentration complex clathrate group showed good antibacterial activity.In addition,the addition of the composite inclusion compound delayed the reduction of sugar content and total polyphenol content in fruit and vegetable juice,and had no obvious effect on the loss of total flavonoid content and soluble solids.