| Sugar beet pectin has higher content of protein,ferulic acid and acetyl groups compared with traditional commercial pectin.Therefore SBP has better emulsification characteristics.In this study,SBP obtained by sequential extraction was to explore the adsorption behavior of pectin at the oil-water interface and to evaluate the influence factor of each component on the emulsification characteristics.The main research conclusions are as follows:1.SBP obtained by sequential extraction.Using ammonium oxalate and sulfuric acid as the extractants,two oxalate-extracted pectins?denoted OEP1 and OEP2?and four acid-solubilized pectins?denoted AEP1,AEP2,AEP3 and AEP4?were sequentially extracted and characterized regarding their structures and emulsifying properties.The oxalate-extracted sample series was significantly different from the acid-extracted sample series in regards to protein,ferulic acid?FA?and amino acid compositions.OEP1 failed to stabilize oil-in-water emulsions containing 15%middle chain triglyceride?MCT?.In contrast,AEP1-4 were shown to have better emulsifying activities.The D43 values of the emulsions prepared at a 1.5%concentration of AEP2-4 did not markedly change throughout the period of storage?28 days?at 30°C.The correlation between emulsifying properties and the structures among the acid-extracted pectins highlights that the extraction sequence plays an important role in the resulting compositional and emulsifying properties of SBP.2.The study on pectin adsorption behavior.AEP1,AEP3,AEP3h?pectin obtained by continuous extraction of sugar beet pulp with sulfuric acid for 3h?and commercial pectin?C-SBP?were selected as research objects to explore the factors.The study for linear plot of interfacial tension kinetics of four pectin samples found that AEP3h has the fastest adsorption speed and could achieve the lowest interfacial tension value.In contrast,C-SBP had the slowest adsorption speed.The emulsion with AEP3h had the worst stability in compared with AEP3.In emulsion system containing 1.5%emulsifier,the adsorbed composition for AEP1,AEP3,AEP3h and C-SBP was 1.49 mg/m2,1.55 mg/m2,1.66 mg/m2,2.94 mg/m2 for pectin,5.15?g/m2,7.90?g/m2,5.95?g/m2,11.62?g/m2 for FA and 0.08 mg/m2,0.08 mg/m2,0.08 mg/m2,0.06 mg/m2 for protein,respectively.The results showed that the factors affecting the adsorption behavior of pectin were related to the molecular structure.The protein-polysaccharide complex was easily and stably to adsorb the oil droplets surface.3.Structure of pectin adsorbed at oil droplet surface and water phase.The adsorbed sugar beet pectin?A-SBP?and nonadsorbed sugar beet pectin?N-SBP?separated from emulsion systems containing 0.5%whole sugar beet pectin?W-SBP?.A-SBP had the highest protein content?11%?.Additionally,A-SBP contained the highest proportion of neutral sugars?NS?,FA and the highest Mw.Specifically,the mole ratio of?Ara+Gal?to Rha was 2.69 for A-SBP,2.98 for W-SBP and 3.37 for N-SBP.Therefore,A-SBP had a suited length of RG-I branching and exhibits the optimum emulsification capacity.The amino acid analysis suggested that A-SBP had a similar composition with W-SBP but the ratio of each amino acid in A-SBP was higher than W-SBP.In the image of A-SBP observed by AFM,the tadpole and rod-like shape hold most of the molecular structure,while the N-SBP presented linear and globular shape.Due to molecular characteristics,N-SBP failed to stabilize oil-in-water emulsions containing 15%MCT.In contrast,A-SBP was shown to have a better emulsifying activity and stability.This discrepancy in emulsion ability among W/A/N-SBP indicated that protein,FA content,the length of lateral chains and amino acid composition play an important role in emulsifying properties of SBP.4.The effects of added ferulic acid?FA?on the emulsifying properties of pectins were investigated.Three commonly used pectins,namely citrus,apple,and sugar beet pectins,were assessed for their ability to cooperate with FA during emulsification.Three series of pectin solutions,each containing 1%pectin and 0.1-0.3%w/w FA,were prepared,characterized and then used to fabricate oil-in-water emulsion?oil/aqueous phase ratio of 85:15 by weight?.The results from fluorescence spectrum indicated hydrophobic associations between pectin and FA,which protected FA from precipitation in aqueous solution.FA addition increased the interfacial and emulsifying activities of three types of pectins in a concentration-dependent manner.Moreover,the emulsions supplemented with FA were more stable during storage at60°C for 7 days,in comparison with their counterparts.Nevertheless,enhancement in emulsion stability was independent of the FA concentration 0.1-0.3%w/w for each of the three series of emulsions.When FA was supplemented at a concentration of 0.2%w/w,the interfacial concentration of FA was 6.44,8.44,and 0.67 mg/m2 for the AP-,CP-,and SBP-stabilized emulsion,respectively.Taken together,the combination of exogenous ferulic acid and pectin exerts an enhanced stabilizing effect for oil-in-water emulsions. |
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