Studies On Physicochemical Properties Of Lemon Peel Pectin And Its Stabilization Of Acidic Milk Beverage

Lemon peel is a by-product of food processing,was often discarded as waste,which causes environmental pollution.Lemon peel is rich in pectin,and take full use of the pectin resource is one of the major issues facing the whole world.However,little information is available about the pectin of lemon peel.In this study,three pectins were extracted from lemon peel using lactic acid?ALPP?,papain?PLPP?and732-type cation-exchange resin?RLPP?,respectively.The physicochemical properties,rheological properties,emulsifying properties and applications in acidic milk beverage of three pectins were analyzed.The results can provide basic data and theoretical support for the development and application of pectin from lemon peel in the food industry.The main research results were as follows:?1?Comparison of yield of three pectins:Based on single-factor experiments,response surface methodology was employed to obtain the optimum conditions for the extraction of RLPP using the extraction material of 732-type cation-exchange resin.The optimum conditions was liquid-solid ratio 42.5 mL/g,resin dosage 5%,pH 1.3 at90?.The yield of RLPP was 27.07%±0.88.And the yield of ALPP and PLPP was22.78%±0.73 and 31.52%±1.12,respectively.The extraction yield of PLPP was the highest,RLPP took second place,and ALPP was the lowest.?2?Determination of physicochemical properties of three pectins:ALPP and RLPP were high methoxyl pectin,while PLPP was low methoxyl pectin.Total galacturonic acid content of ALPP,PLPP and RLPP were 46.59%±0.78,58.54%±0.79,53.97%±0.41,respectively.The solubility were 76.25%±2.05,92.37%±1.41,94.52%±1.27,respectively.The protein content were 1.74%±0.2,2.09%±0.4,2.64%±0.27,respectively.RLPP had the smallest particle size and was loose and slender.?3?Analysis of rheological properties of three pectins:Three pectin solutions were pseudoplastic fluids.The apparent viscosity of pectin solution decreased with increasing temperature,while increased with increasing Ca²⁺,Na⁺and sugar concentration.Under the same conditions,the apparent viscosity of RLPPs was higher than that of ALPPs and PLPPs.G'and G"of pectin solution increased with the increase of oscillation frequency at the same concentration,and the gel point decreased with the increase of concentration.?4?Analysis of emulsifying properties of lemon peel pectin and gum arabic:Emulsion activity,emulsion stability,droplet size,zeta-potential and freeze-thaw stability of four kinds of emulsion dependented on the concentration distinctly.RLPP emulsion exhibited the best emulsion activity,emulsion stability and freeze-thaw stability,which maybe relate to its own viscosity.With the increase of pH,lemon peel pectin emulsion showed better emulsion activity and emulsion stability under acidic conditions,while the gum arabic emulsion was just the opposite.The zeta-potential of the four emulsions increased with the increase of pH,and the RLPP emulsion was metastable state at pH 11.The emulsions of the three pectins exhibited better freeze-thaw stability than that of gum arabic.?5?The effect of three pectins on stabilizing acidic milk beverages:The weight fraction of AMBs increased significantly with the increase of pectin concentration,especially PAMB.When the concentration of RLPP was 0.2 wt%,the viscosity of RAMB was the lowest and the most stable due to good pectin-casein interaction.The particle size of AMBs was reduced by addition of pectin,and particle size of AMBs was the smallest and almost maintained a constant value by using RLPP.The result was confirmed by the analysis of SEM and CLSM.Therefore,RLPP can be used as a new stabilizer in AMBs.