Influences of the different chemical components of sugar beet pectin on the emulsifying performance of conjugates formed between sugar beet pectin and whey protein isolate

The effects of different sugar beet pectin (SBP) components on the conjugates formed between SBP and whey protein isolate (WPI) under the condition of 80 °C, 79% relative humidity, for 5 h were investigated in this study. SBP samples with different chemical compositions were SBP1 (without any treatment), SBP2 (modified with polygalacturonase), SBP3 (modified with arabinanase/galactanase combination), and SBP4 (control pectin sample). The covalent binding of SBP to WPI was confirmed by SDS-PAGE. Degree of glycosylation (DG) and fluorescence intensity of conjugate samples decreased in the order: WPI-SBP1 > WPI-SBP2 > WPI-SBP4 > WPI-SBP3. The interfacial tension of the WPI decreased significantly after conjugating with SBP1 or SBP2. The interfacial tension of conjugates increased in the order: WPI-SBP1 < WPI-SBP2 < WPI-SBP4 ≈ WPI-SBP3. Emulsifying properties of the WPI were improved significantly after covalent modification with SBP. For the conjugate samples, the higher DG corresponded to the better emulsifying properties. All the results reveal that the neutral sugars region of SBP is easier to occur conjugate reaction with WPI compared to the galacturonic acid region of SBP, and the DG is an important factor influencing the emulsifying properties of the conjugate sample.