Effect Of Pectin Structure And Structural Changes On Carotenoid Bioaccessibility In Carrot Juice Systems

In this paper,carrot juice system was taken as the research object.After obtaining the correlations between pectin structure differences and carotenoid delivery,the effects of ultra-high pressure homogenization and pectinase treatment on the endogenous pectin structure,carotenoid bioaccessibility as well as the relationship between pectin variation and carotenoid bioaccessibility were investigated.The purpose of present research was to explore whether ultra-high pressure homogenization and pectinase treatment could be used as new methods to improve the carotenoid bioaccessibility,and provide a theoretical basis for subsequent research on the stability improvement and carotenoid bioaccessibility of carrot juice.The main results are as follows:The effects of pectin sources,sugar types and pH values on carotenoid transfer characteristics were studied in the fruit and vegetable simulated juice systems.For the different pectin simulated systems,the highest carotenoid bioaccessibility?CB?was 16.68%,found in the sugar beet pectin?SBP?simulated system.For the different sugars simulated systems,the highest CB of 7.30%was found with sucrose?Suc?simulated system.For the different pH values,the highest CB was 6.81%at pH 6.8.Correlation analysis results showed that carotenoid bioaccessibility had significant correlations?P<0.05?with pectin characteristics?degree of methoxylation?DM?,degree of acetylation?DAc?,molecular weight?M_W?,neutral sugar,linearity?Ratio A??as well as the physicochemical properties?D[4,3]?during digestion?P<0.05?.Therefore,pectin structure plays an important role in the carotenoid transmission.The effect of homogenization pressures on the structure of water-soluble pectin?WSP?and carotenoid bioaccessibility in the carrot juice were studied.It was found that with the increase of homogenizing pressure,CB increased first and then decreased,reaching a maximum of 16.45%at 180 MPa.Meanwhile,homogenization-pressure could significantly affect the WSP characteristics.With the elevated pressure up to 300 MPa,the galacturonic acid?GalA?content of WSP increased significantly.As the homogenization pressure increased,the M_W of WSP decreased.When the homogenization pressure reached 300 MPa,the M_W increased sharply.And with the increased pressure,DAc gradually increased.Furthermore,the linearity?Ratio A?gradually decreased with the lowest Ratio A at 240 MPa.RG-I branching degree?Ratio C?of WSP gradually decreased and the lowest valued at 300 MPa.Within the experimental pressures,DM and Ratio B had no significant difference.Moreover,CB showed significant correlations with pectin M_W and Ratio C?P<0.05?,respectively,while no significant correlation neither with pectin GalA,DM nor DAc.Based on the above analysis,the stability of carrot juice homogenized at different pressure was observed at 4°C for 28 days.When pressure was greater than 60 MPa,L*,a*,and b*values of samples increased with the extension of storage time.The apparent and suspension stability of carrot juice with 360 MPa treatment remained basically stable.As the homogenization pressure increased,the absolute values of?-potential,D[4,3],D[3,2],and D₅₀ of carrot juice samples decreased.With the extension of storage time,the?-potential of carrot juice with 360 MPa treatment had no significant difference during the storage period,while the?-potential absolute values of samples at other pressures decreased significantly,indicating that ultra-high pressure homogenization treatment?homogeneous pressure 360 MPa?could maintain the stability of carrot juice.Carrot juice samples were treated with polygalacturonase?PG?for different hours to explore its impacts on the physicochemical properties and carotenoid bioaccessibility of carrot juice.With the extension of enzymolysis time?0-16 h?,the pH of carrot juice samples gradually decreased from 6.3 to 4.9.The confocal microscopy images clearly indicated that the carotenoids of carrot juice developed from uniform distribution to uneven aggregation.The absolute value of?-potential increased first,which had a maximum at 4 h,and then decreased.The D[4,3],D[3,2]and D₅₀ of carrot juice without exception decreased,among which the effect of enzymatic treatment on D[4,3]of carrot juice was the most significant.Additionally,the carotenoid bioaccessibility increased first,reaching a maximum value of36.64%at 4 h,and then decreased with the extend enzymatic treatment time.Compared to non-enzyme-treated carrot juice,CB increased nearly two times?176.95%?.