Evaluation of new cassava varieties for adhesive properties

Cassava varieties: Red stick, Butter stick, Maracas Black stick, and M Col 22 were evaluated for pulp yield, starch yield, amylose, and protein contents in a screening exercise of new cassava varieties. Starch content of the tubers was determined. Starch was extracted from freshly harvested nine-month-old tubers using standard method. The starch paste was air dried before final drying at 50°C for 8 h in an oven. Amylose and protein contents of the starch were determined by approved methods. Adhesive was made by heating 10% starch slurry in 0.1 M KOH solution to 70 and 80°C, respectively. Color, pH, viscosities, adhesive force, adhesiveness, stickiness, and storage properties of the adhesives were determined. Pulp yields (74.1–83.1%), starch yields (11.8–20.3%); starch amylose (23.5–26.5%) and protein contents (0.34–0.82%) of cassava tubers differed. Also peak viscosity (297–393 RVU), breakdown viscosity (195–263 RVU), and set back viscosity (43–52 RVU) of the starches were significantly different. Similarly the adhesive force (−77 to −146 and adhesiveness (−1952 gs to −3075 gs) varied significantly. Adhesive from variety M Col 22 resolved into two fractions at two weeks of storage and completely broke down by week three. Pastes produced at 80°C were less viscous, had lower adhesiveness and adhesive force and were darker than pastes produced at 70°C. Storage reduced the adhesive force and adhesiveness of the adhesives. The adhesive pastes were alkaline (pH10.69–11.58). The Maracas Black Stick and Butter Stick varieties produced the best adhesives in terms of stickiness and resistance to degradation than the other two varieties.