Comparison of the adhesive performances of soy meal, water washed meal fractions, and protein isolates

Authors: He, Zhongqi; Chapital, Dorselyn; Cheng, Huai

Submitted to: Modern Applied Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2016
Publication Date: 3/29/2016
Citation: He, Z., Chapital, D.C., Cheng, H.N. 2016. Comparison of the adhesive performances of soy meal, water washed meal fractions, and protein isolates. Modern Applied Science. 10(5):112-120.

Interpretive Summary: 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. As synthetic wood adhesives are mostly derived from depleting petrochemical resources and have caused increasing environmental concern, agricultural product and byproduct derived adhesives have attracted much attention in recent decades. Among them, soy protein isolate (SPI) is the most studied for this purpose. In this work, we applied the water washing process to produce water washed soy meal, and compared its adhesive performance with both unwashed soy meal and SPI. One of our purposes is to increase our understanding of the adhesive mechanisms of oilseed meal products. These observations using soy meal products differed from our previous observations for cottonseed meal products. Further investigation is needed to determine the mechanisms and causes of the difference in adhesive performance between the two types of oilseed meal products.

Technical 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. However, 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 oC) 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.