The aim of the present study was to investigate the impact of whey protein isolate (WPI)-beet pectin
conjugation on the physical and chemical properties of oil-in-water emulsions incorporating b-carotene
within the oil droplets. Covalent coupling of WPI to beet pectin was achieved by dry heating of WPI-beet
pectin mixtures of different weight ratios at 80, 90, 100
C and 79% relative humidity for incubation times
ranging from 1 to 9 h. It was confirmed by SDS-polyacrylamide gel electrophoresis that WPI covalently
linked to beet pectin. The physical and chemical stability of b-carotene emulsions was characterized by
droplet size and distribution, transmission profiles using novel centrifugal sedimentation technique,
microstructure and b-carotene degradation during the storage. Compared with those stabilized by WPI
alone and unheated WPI-beet pectin mixtures, b-carotene emulsions stabilized by WPI-beet pectin
conjugates had much smaller droplet sizes, more homogenous droplet size distribution, less change in
centrifugal transmission profiles and obviously improved freezeethaw stability, indicating a very
substantial improvement in the physical stability. Rheological analysis exhibited that emulsions stabilized by WPI-beet pectin conjugates changed from a shear thinning to more like Newtonian liquid
compared those with WPI alone and unheated WPI-beet pectin mixtures. Degradation of b-carotene in
emulsion during storage was more obviously retarded by WPI-beet pectin conjugate than WPI and
unheated WPI-beet pectin mixture, probably due to a thicker and denser interfacial layer in emulsion
droplets. These results implied that proteinepolysaccharide conjugates were able to improve the
physical stability of b-carotene emulsion and inhibit the deterioration of b-carotene in oil-in-water
emulsions.
The aim of the present study was to investigate the impact of whey protein isolate (WPI)-beet pectin
conjugation on the physical and chemical properties of oil-in-water emulsions incorporating b-carotene
within the oil droplets. Covalent coupling of WPI to beet pectin was achieved by dry heating of WPI-beet
pectin mixtures of different weight ratios at 80, 90, 100
C and 79% relative humidity for incubation times
ranging from 1 to 9 h. It was confirmed by SDS-polyacrylamide gel electrophoresis that WPI covalently
linked to beet pectin. The physical and chemical stability of b-carotene emulsions was characterized by
droplet size and distribution, transmission profiles using novel centrifugal sedimentation technique,
microstructure and b-carotene degradation during the storage. Compared with those stabilized by WPI
alone and unheated WPI-beet pectin mixtures, b-carotene emulsions stabilized by WPI-beet pectin
conjugates had much smaller droplet sizes, more homogenous droplet size distribution, less change in
centrifugal transmission profiles and obviously improved freezeethaw stability, indicating a very
substantial improvement in the physical stability. Rheological analysis exhibited that emulsions stabilized by WPI-beet pectin conjugates changed from a shear thinning to more like Newtonian liquid
compared those with WPI alone and unheated WPI-beet pectin mixtures. Degradation of b-carotene in
emulsion during storage was more obviously retarded by WPI-beet pectin conjugate than WPI and
unheated WPI-beet pectin mixture, probably due to a thicker and denser interfacial layer in emulsion
droplets. These results implied that proteinepolysaccharide conjugates were able to improve the
physical stability of b-carotene emulsion and inhibit the deterioration of b-carotene in oil-in-water
emulsions.
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