Study On Stepwise Extraction And Functional Properties Of High Methoxyl Pectin From Lemon Peel

In this study,lemon peel was used as the raw material to extract primary pectin(HMP-1)and secondary pectin(HMP-2)by organic acid stepwise extraction.The effects of extraction conditions on the extraction efficiency of HMP-1 and HMP-2 were systematically studied.The physicochemical properties of HMP-1 and HMP-2 were investigated characterized.Micromorphological observations were also conducted to explore the differences in structural properties.The influence of different degree of esterification(DE)on the gelation properties of HMP-1 was also studied.According to the application experiment of acid milk beverage(AMD),the dispersion stability of HMP-1 to protein was explored.The gel properties of HMP-2 in jelly candy were studied by the application experiment of gel-type candy.The findings are as follows:(1)According to the single factor exploration experiments,the optimal extraction conditions of HMP-1 were determined as follows: material-liquid ratio 1:20,p H 1.7,extraction temperature 70 ?,extraction time 1.5 h.Under this condition,the yield of HMP-1 was up to 19.22% and the viscosity of the 1% HMP-1 solution was 104.55 m Pa·s.The optimal extraction conditions for HMP-2 were determined as follows: material-liquid ratio 1:10,p H 1.7,extraction temperature 80 ?,extraction time 1.5 h.Under the above condition,the yield of HMP-2 was up to 9.74% and the viscosity of the 1% HMP-2 solution was 49.23 m Pa·s.(2)The physicochemical properties of HMP-1 and HMP-2 were investigated by determining basic physical and chemical indicators,molecular weight(Mw),particle size,Zetapotential,rheological property and Fourier infrared spectroscopy.The microstructure was observed by atomic force microscopy(AFM).The research results showed that both HMP-1 and HMP-2 were high methoxyl pectin with the characteristics of anionic polysaccharides.It was showed that HMP-1 and HMP-2 behaved similar infrared spectral information and some similar properties.However,there are some differences between HMP-1 and HMP-2 such as the degree of esterification,molecular weight and gelation property.AFM results showed that HMP-1 showed a longer linear shape,while HMP-2 showed a more dispersed and finely divided state.(3)The effect of pectin methylesterase(PME)on the properties of HMP-1 was evaluated.PME played a role in reducing the degree of esterification of HMP-1.The degree of esterification(DE)of the obtained HMP-1 was 70.11%,63.24%,60.62%,54.55% and 51.03% respectively.With the decrease of the degree of esterification,HMP-1 also decreased in zetapotential,particle size,viscosity and molecular weight.When the degree of esterification of HMP-1 was higher than 63.24%,the viscoelasticity and TPA texture properties of HMP-1 gel were hardly affected by the changes in the degree of esterification.When degree of esterification was higher than 54.55%,HMP-1 could maintain better and stable gel properties with the changes in the degree of esterification.When the degree of esterification was less than 54.55%,HMP-1 gel showed a large degree of collapse,and the gel properties decreased significantly.(4)HMP-1was a good protein stabilizer that could stabilize casein in acidic milk beverages and achieve stable and uniform.When the addition amount of HMP-1 was 2.5‰,the particle size of the stabilized acidic milk beverage reached 728 nm.HMP-2 can be applied in jelly candy with good gel property with a addition amount of 1.3%.