Effect of Genotype, Age and Location on Cassava Flour Yield and Quality
Flour yield and its solubility, swelling power and water-binding capacity from four genotypes of cassava were studied. This was to study the effect and relative importance of age and environment on cassava flour yield and quality. Trials were conducted at six selected districts from the Forest and the Transition ecozones of Ghana. Harvesting was done at monthly intervals from 12th to the 15th month after planting. At each harvest, 25 kg of fresh tubers of each of the genotypes from each location were commercially processed into flour. Flour yield of the genotypes produced at the ecozones across ages at harvest indicated significant genotype by location interaction effect. While solubility and swelling power steadily increased with age, the opposite was true for water binding capacity. Solubility values ranged from 6.89 to 12.00%. That of swelling power and water-binding capacity was 16.55-20.46 g g-1 and 111.92-139.17%, respectively. Significant differences (p< 0.05) were established between the locations for traits studied. Interaction between genotype and locations were also significant (p< 0.05).
Cassava (Manihot esculenta, Crantz) is the main starch staple of many
people in Africa (Manu-Aduening et al., 2006).
It can yield in relatively infertile soils and tolerates long periods of drought,
making it particularly important for poor rural households farming marginal
lands. In Ghana, a mean per capita production of 465 kg annum-1 provides
about 20% of calories in the diet, far ahead of any other single crop or animal
source (FAOSTAT, 2005. http://faostat.fao.org).
According to Manu-Aduening et al. (2006) most
cassava produced is consumed fresh as fufu but there are many small-scale and
a few medium to large-scale enterprises currently in Ghana that process cassava
into diverse foods and starch for industrial uses.
Cassava has become an important crop in Ghana because of its diverse uses,
potential in the economy and its relatively high productivity under conditions
which many other crops fail. Cassava flour is a potential substitute for wheat
and maize-based flours (Rickard et al., 1991;
Tian et al., 1991). One fifty thousand tons of
wheat flour is imported per annum into Ghana. This is mainly used by the bakeries,
with about 1,200 t annum-1 used by the plywood industry (Dziedzoave
et al., 2000). Much of this can be replaced by cassava flour to reduce
government spending on balance of payment deficit. This is because a preliminary
technical and economic study indicated a potential substitute of local cassava
flour for imported products in the areas of plywood glue extenders and paperboard
adhesives in Ghana (Graffham et al., 2000).
Because cassava has traditionally been the crop of the poor, expanding its
market can bring direct benefit to those who need it most (Porto,
2004). Thus farmers who form about 70% of the population and are mostly
poor will enjoy the benefits leading to solving the problem of poverty. To benefit
from cassava as elaborated, Dziedgoave et al. (2000) indicated that the
logical step to take was to place research emphasis on requirements of end users,
market demands, industrial specification and the development of other technologies
with potential for wider commercial uptake and dissemination. This suggests
that in addition to selecting genotypes for desired agronomic traits such as
higher yield, physicochemical and functional properties such as swelling power,
solubility and water binding capacity should also be known. These traits and
properties are affected by variety, age and the environment. For example, Moorthy
and Ramanujam (1986) observed a number of physicochemical properties to
increase with age up to the sixth month for six varieties studied. According
to Asaoka et al. (1992) and Defloor
et al. (1998), season at harvest has influence on physicochemical
and rheological properties of cassava.
Thus, the objective of this study was to investigate the effect of cassava varieties on flour yield and its functional and physicochemical properties as influenced by different dates of harvesting and location.
MATERIALS AND METHODS
The study was done in 2004/2005. Four elite varieties-NKZ-009, NKZ-015, DMA-002
and WCH-037 were studied at selected districts in the Forest and Transition
ecozones of Ghana. The selected districts were Mampong, Kumasi and Dormaa-Ahenkro
(Forest ecozone) and Techiman, Kintampo and Kwame Danso in the Transition ecozones.
In the Forest locations, land preparation was by slashing and removal of stumps
before planting. For the Transition ecozone, the land was ploughed and harrowed
before planting. The spacing was 1x1 m and four weedings were carried out at
2, 5, 9 and 14 months after planting. Harvesting began at 12 months and continued
at monthly interval until the 15th month. At each harvest, 25 kg of fresh tubers
from the four elite genotypes were commercially processed into flour. This was
done by some women trained by Women in Agricultural Development (WIAD) in agro-processing
at their local factory at Ashanti Mampong. Sample from genotype at each harvest
and location were analysed at the Plant Breeding Laboratory of Kwame Nkrumah
University of Science and Technology (KNUST), Kumasi for their physicochemical
and functional properties. The analysis was carried out in triplicate and parameters
determined were solubility, swelling power and water-binding capacity. The solubility
and swelling power was determined by the method of Leach
et al. (1959). The method of Yamazaki (1953)
as modified by Medcalf and Gilles (1965) was used to determine
the water-binding capacity. Flour yield of the elite varieties at the various
locations were subjected to statistical analysis by line graphs using Excel.
Data from the physicochemical and functional properties were analysed using
the analysis of variance (ANOVA) in a split-split plot design with location
as main plot factor, genotype as subplot factor and age as the sub-subplot factor
RESULTS AND DISCUSSION
Varieties NKZ-009 and WCH-037 gave the lowest and highest flour yield respectively
in the Forest belt occurring at 12 and 15 months after planting. In the Transition
ecozone, the lowest and the highest flour yields were produced at 13 and 12
months after planting and these were produced by NKZ-009 and WCH-037, respectively.
While flour yield of DMA-002 and WCH-037 was highest at 12 months after planting
in the Transition belt, it was highest at 13 and 15 months after planting, respectively
in the Forest ecozone. Again while flour yields of the NKZ-lines appear lowest
at 12 months after planting in both ecozones (Fig. 1a and b),
the highest yield for NKZ-015 occurred at 15 months in the two ecozones but
that of NKZ-009 was at 14 and 15 months, respectively in the Forest and Transition
||Flour yield of the cassava genotypes at different harvest
dates. a): Forest ecozone and b): Transition ecozone
Flour yield of the genotypes produced at the ecozones across ages at harvest
indicated significant genotype by location interaction effect. This indicates
that growing conditions as well as harvesting time are critical for realising
potential flour yield of cassava varieties (Fig. 1a and b).
Quality of flour is explained by its solubility, swelling power and water-binding capacity. Solubility is a solutes ability to dissolve in a solvent while swelling power defines the maximum increase in volume and weight, which a solute undergoes when allowed to swell freely in water. These occur when the adhesive force between the solute and the solvent becomes greater than the cohesive force between the solute molecules. No significant differences were established between the genotypes (Table 1). NKZ-009 and NKZ-015 gave the highest and lowest values respectively in a range of 8.50 to 9.56%.
Solubility steadily increased with age from 7.57% at 12 months to 10.15% at 15 months and the difference was significant (p<0.05) (Table 1). The interaction between age and genotype were also significant (Table 1). The average solubility values across the locations ranged from 8.02 to 10.46%. Values obtained at Mampong and Kintampo did not differ statistically (p>0.05) but were lower than values produced at the other locations (Table 2). A great deal of variation was observed among the varieties across the locations indicating significant interaction between genotype and location (Table 2).
The swelling power values obtained ranged from 16.55 to 20.46 g g-1
(Table 3 and 4) and these agreed with the
range observed by Apea Bah (2003) which was 14.88-26.58
g g-1. DMA-002 and WCH-037 gave the lowest and highest mean values
respectively (Table 3). In a narrow range of 17.55-19.82 g
g-1 swelling power steadily increased with age, but only the mean
value at 15 months was significantly different (p<0.05) (Table
3). Interaction between age and variety was significant (p<0.05). Even
though genotypic differences were not significant (p>0.05) (Table
3), differences between locations were significant (p<0.05) (Table
4). Values obtained were generally higher among the Forest locations than
the Transition locations (Table 4) and the interactions between
genotype and location were significant (p<0.05).
|| Solubility (%) of flour harvested at different ages
|LSD (5%): Variety (V) = 1.06; Age (A) = 1.15; V x A = 2.80
|| Solubility (%) of flour harvested at different locations
|LSD (5%): Variety (V) = 1.06; Location (L) = 1.72; V x L =
2.12; a: Location, MAP: Mampong, DMA: Dormaa-Ahenkro, KSI: Kumasi,
KIN: Kintampo, KSO: Kwame-Danso, TEC: Techiman
|| Swelling power (g g-1) of flour harvested at different
|LSD (5%): Variety (V) = 0.78; Age (A) = 0.84; V x A = 2.04
|| Swelling power (g g-1) of flour harvested at different
|LSD (5%): Variety (V) = 0.78; Location (L) = 0.84; V x L =
1.27, aLocation: DMA-Dormaa-Ahenkro, MAP: Mampong, DMA: Dormaa-Ahenkro,
KSI: Kumasi, KIN: Kintampo, KSO: Kwame-Danso, TEC: Techiman
Unlike the other two rheological parameters-solubility and swelling power which
showed no significant differences (p>0.05) between the genotypes, there was
significant differences (p<0.05) between the genotypes for water-binding
capacity (Table 5). According to Niba et
al. (2001), water-binding capacity relates to the viscosity of the starch
granules. This means that while there may not be major differences in the cohesive
forces between the granules of starch in the flour of the genotypes, their viscosity
when heated could be different. Water-binding capacity also determines the bulking
and consistency of products. The NKZ-lines produced the highest values. This
shows that the NKZ-lines have greater water holding capacity and will be more
viscous when heated than DMA-002 and WCH-037. Thus, the NKZ-lines would provide
more consistency and would therefore, be better genotypes for bakery products
than DMA-002 and WCH-037. Water-binding capacity declined with age from 12 months
at 128.89 to 121.58% at 14 months after planting (Table 5).
Significant differences (p<0.05) were established between the locations.
|| Water-binding capacity (%) of Flour harvested at different
|LSD (5%): Variety (V) = 4.54; Age (A) = 4.90; V x A = 9.93
|| Water-binding capacity (%) of flour harvest at different
|LSD (5%): Variety (V)= 4.54; Location (L)= 4.90; V x L = 15.47,
aLocation:DMA-Dormaa-Ahenkro, MAP: Mampong, DMA: Dormaa-Ahenkro,
KSI: Kumasi, KIN: Kintampo, KSO: Kwame-Danso, TEC: Techiman
The mean range was 117.92-130.69% and Techiman and Kwame-Danso produced the
lowest and highest values respectively (Table 6). Interaction
between genotype and locations was also significant (p<0.05).
The variations and interactions between genotype and environment may complicate evaluation and selection of cassava genotypes for cassava flour utilization. This is due to the wide variation in the environmental conditions during growth period of cassava. Age at harvest of cassava genotypes also has significant effect on flour yield, physicochemical and functional properties of cassava flour.
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