Comparison of the Adhesive Performances of Soy Meal, Water Washed Meal Fractions, and Protein Isolates

Abstract

Adhesive bonding of wood plays an increasing role in the forest products industry and is a key factor for efficiently utilizing timber and other lignocellulosic resources. In this work, we obtained five soy meal products through commercial sources or in-house preparations. The protein content was 49.6%, 56.9%, 66.2%, 86.3%, and 91.9% for untreated defatted soy meal, pH 8.5 water washed meal, neutral water washed meal, commercial protein isolate, and in-house prepared protein isolate. The adhesive performances measured by the maximal dry and soaked shear strength of the bonded maple veneers at break were not exactly in the same order of the protein content, indicating that other components (e.g. carbohydrates, metals) might also have played certain roles in the adhesive ability of these products. Data at two press temperatures (i. e. 100, and 130 o C) with or without the addition of tung oil revealed that water washed soy meals behaved more like untreated meal than soy protein isolates. This observation is different from a recent report on the effect of water washing on cottonseed meal products. Thus, further elucidation of the mechanisms or causes of the differing effects of water washing would shed light on the adhesive mechanisms of the two types of oilseed meal materials, thus optimizing use of these materials and their fractions for wood bonding.

Adhesive properties of water-washed cottonseed meal on four types of wood

“…Two methods were used for evaluation of the water resistance per ASTM D1151-00 [17]: (1) wet strength: the bonded specimens following the two-day conditioning period were immersed in tap water at 23 °C for 48 h, and the wet strength is tested immediately after soaking, and (2) soaked strength: the bonded specimens following the two-day conditioning period were immersed in a water bath at 63 °C for 4 h, then dried at room temperature overnight (18-20 h). The hot water immersion is repeated and the specimens are allowed to dry at normal room temperature and relative humidity for 48 h followed by strength tests.…”

Protein profiling of water and alkali soluble cottonseed protein isolates

“…The potential value-added products of cottonseed protein isolates include but are not limited to bioplastics and films 17 , 18 , superabsorbent hydrogel 19 , antioxidant peptides/extracts 20 , 21 , and bio-based wood adhesives 22 , 23 . Studies 22 , 24 have shown the differences in the adhesive performance between cottonseed protein adhesives and widely-studied soy protein-based adhesives, which may be attributed to the difference in protein structures and composition between the two types of oil seeds.…”

Adhesive Strength of Pilot-Scale-Produced Water-Washed Cottonseed Meal in Comparison with a Synthetic Glue for Non-Structural Interior Application

“…Vegetable proteins are typically isolated from the seed meals by base extraction and acid precipitation. To reduce the cost, researchers have also tried to directly use the seed meals as wood adhesives (He et al, 2016b;Lorenz et al, 2015;Luo et al, 2016;Shi et al, 2017). In recent years, He and his colleagues have demonstrated that water-washed cottonseed meal (WCSM) could serve as promising wood adhesives (He et al, 2014a(He et al, , 2014b(He et al, , 2014c.…”