A Novel Soybean Flour-based Sizing and Strength Additive for Replacing the Daily Food Starch in the Papermaking Process

Millions of tons of starches are used as a paper sizing and dry strength additive every year despite the fact that starch is typically in high demand for daily meals. This is important to note because global food demand is increasing due to population growth. Similarly, millions of tons of petroleum-based paper dry strength agents used in the paper making industry have raised environmental concerns, motivating efforts toward developing alternatives.

Soybean flour is a cheap complex polysaccharide compared to starch, modified starches, or petroleum-based strength agents, and may be a suitable substitute. But the main problem associated with using soybean flour is that it poses a bacterial digestion problem that can produce bad odors and fouling, vital issues to consider for use in paper industries.

The goal of this project is to stop the bacterial decomposition of soybean flour by an environmentally sustainable chemical modification in order to benefit paper sizing/strength applications in the paper and paper packaging industries. The key research activities of this work include: 1) synthesis of quaternary positively charged functionalized soybean flour by a specific chemical pathway modification in which modified soybean flour will ultimately demonstrate the antimicrobial activity to overcome bacterial decomposition, 2) investigation of the biological decomposition of modified soybean flour and unmodified soybean flour to determine antimicrobial performance, and 3) characterization of the physical properties and antimicrobial activities of the modified soybean flour and modified soybean flour-treated sized paper.

The goal is for these materials to be used as an alternative to starch-based sizing/strength agents in the paper and paper packaging industries. The proposed modified soybean flour has the potential to address low-cost, high-performance, biodegradable, and food-grade requirements for non-toxic paper products. Additionally, the project holds the potential to lead to the replacement of non-biodegradable and polluting petroleum-based paper dry-strength agents such as polyacrylamide used in the paper industries and thus address environmental and health concerns.

Both graduate and undergraduate students will be members of the project team. In addition, K-12 outreach is planned as part of the total project deliverables.

The project approach is based on exploiting an innovative reaction mechanism for introducing a quaternary cationic charge into soybean flour such that the functionalized soybean flour will exhibit bactericidal activity and overcome biologically-induced decomposition. Preliminary results support the hypothesis that the introduction of this quaternary cationic charge in soybean flour plays a key role in stopping biological digestion and inhibiting soybean flour contamination by bacteria, mold, and fungi.

This hypothesis will be further examined by testing reaction conditions in pursuit of enhancing targeted performance. Modified soybean flour will be analyzed by FTIR, NMR, XPS, SEM, TGA, DSC, and XRD to confirm modification and thermal stability. Cationic charges in cross-linked modified soybean flour will be determined by a charge analyzer and antimicrobial activity will be evaluated by standard AATCC 100 and FTTS- FA-002 test methods.

The biological digestion of soybean flour and quaternary cationic charged-functionalized soybean flour will be evaluated by ASTM test methods. Preliminary lab results have shown that the quaternary cationic charged-functionalized soybean flour significantly enhances the antimicrobial properties of itself and with a sized paper sheet as well as significantly contributing to the tensile strength of paper.

The work will probe not only the chemical transformations but also explore a range of reactants and crosslinking agents, and optimize reaction conditions to make functionally competent and application-motivated antimicrobial soybean flours to potentially replace daily food starch. Likewise, preliminary results indicate that the functionalized soybean flour can be used as a surface sizing agent in paper to change absorption properties and increase the strength of sized paper, potentially replacing starch-based sizing agents.

The project will further confirm these preliminary results. The absorption, strength, stiffness, printability, and other properties of modified soybean flour-treated sized paper will be evaluated and compared with starch-treated sized paper properties. The antimicrobial properties of modified soybean flour-treated sized paper will be evaluated to confirm the inhibition of bacterial decomposition of soybean flour.

Additionally, modified soybean flour will be blended with pulp slurry to fabricate additive-treated paper sheets to characterize physical properties, especially strength compared to commercial petroleum-based strength additive (polyacrylamide)-treated papers.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.