Comparative evaluation of physicochemical and functional properties of cassava flour from different fertilizer protocols

Cassava (Manihot esculenta Crantz) is a major food crop in tropical Africa. The root has the potential to bridge the food security gap in Africa. However, yield is generally low due to poor soil fertility and failure of farmers to apply fertilizer during crop cultivation. Fertilizer application to soil is a way of increasing yield of cassava root per unit area. The study was therefore conducted to investigate the flour yield, physico-chemical, functional and pasting properties of flour from Afisiafi, Bankyehemaa and Dokuduade cassava varieties under seven different fertilizer protocols and a control (no fertilizer). The cassava varieties were harvested after 10 months of maturity and processed into flour. Highest dry matter (48.79%) was recorded for Bankyehemaa under NPK (60-30-0) fertilizer protocol with lowest value (36.76%) for Dokuduade for the control. Highest flour yield (65.29%) was recorded for Afisiafi under NPK 60-30-60 and lowest (18.71%) for Dokuduade under NPK (30-15-15) +2.5t/ha Poultry Manure (P. M). The highest flour pH (9.95) was recorded for Afisiafi with NPK 60-30-30 and lowest (5.57) for Dokuduade with 2.5t/ha P.M. Flour pH was significantly affected (P < 0.05) by varietal differences and fertilizer treatments. Starch yield of flour was highest (80.26%) for Afisiafi under NPK (30-15-15) + 2.5t/ha P.M and lowest (49.82%) for Bankyehemaa under NPK (60-30-90). In terms of minerals compositions; calcium range between 779.57 and 1777.75 mg/kg, with the lowest for Bankyehemaa for control and highest for Afisiafi with 5t/ha P.M. while iron range between 5.81 and 79.29 mg/kg, lowest for Afisiafi for control and highest for Afisiafi with 5t/ha P.M. Functional properties such as water binding capacity recorded lowest (91.83%) for Bankyehemaa under NPK (60-30-90) and highest (144.48%) for Bankyehemaa under NPK (60-30-60) treatment, swelling power range between 2.62 and 10.51% for Dokuduade and Afisiafi under control and NPK (60-30-90) protocols, respectively while amylose estimation range between 10.02 and 22.52%, with lowest for Bankyehemaa under NPK (30-15-15) +2.5t/ha P.M. and highest for Dokuduade under NPK (60-30-0). Solubility also recorded lowest of 4.72% and highest of 16.49% for Bankyehemaa under NPK (60-30-0) and Afisiafi under NPK (30-15-15) +2.5t/ha P.M protocols respectively. Pasting temperature (53.40 - 70.10 oC), retrogradation (40.50 – 133.50 BU), breakdown viscosity (259.00 – 394.00 BU) and peak viscosity (334.50 – 657.50) were recorded for the pasting properties of the flour. The cassava flour starches exhibit round/truncated granule shapes with size range between 13.0 and 19.4µm. Bankyehemaa was found to have larger starch granule than Afisiafi and Dokuduade. The value obtained for the flour and starch yield show that Afisiafi can be used for industrial flour and starch production. Afisiafi, Dokuduade and Bankyehemaa cassava varieties are very responsive to potassium (K), however, increased amount of K decreases the dry matter content. Increasing the Level of K in the soil also decreases the starch content of flour. Depending on the characteristic used for the selection of starches and flour for industrial and domestic uses, the result obtained from the study revealed that fertilization of the soil with organic fertilizers such as poultry manure and chemical fertilizers has significant impact on the quality of cassava flour and starches.

Source: KNUST