Water resistances and bonding strengths of soy-based adhesives containing different carbohydrates

- Carbohydrate effects on the properties of SBA through the Maillard reaction.
- Sucrose and glucose act as a cross-linking agent during the curing process of SBA.
- Sucrose and glucose could improve water resistance and bonding strength of SBA.
- Polysaccharides could decrease water resistance and bonding strength of SBA.

The objective of this study was to determine the effects of carbohydrates on the water resistances and bonding strengths of soy-based adhesives (SBAs). Defatted soy flour (DSF), soy protein isolate (SPI), sucrose, and glucose were used to prepare SBAs, and the mechanisms of water resistance, hydrophilicity, and bonding strength (boiling-water test) were investigated. Fourier-transform infrared and X-ray photoelectron spectroscopies showed that the cross-linking and hydrophobicities of cured SBAs were enhanced by Maillard reactions between soy protein and sucrose and glucose. SBAs prepared with SPI and DSF had the lowest and highest water absorptions, respectively. The highest bonding strength was 0.73 MPa, for a glucose content in the SBA of 71 wt%. The lowest bonding strength was observed in a cured SBA prepared from DSF. A reduced carbohydrate content, or increased sucrose and glucose fractions in the carbohydrate, decreased the hydrophilicity and increased the bonding strength of the cured SBA.