Table 10.1.2 The types of cassava products studied by previous authors
Flour Type | Specific product(s) | Authors
Fermented | Pupuru flour | Osundahunsi (2005)
―"― | Fufu flour | Sanniet al. (2006)
―"― | Fufu flour | Sanniet al. (1997)
―"― | Pupuru flour | Shittu et al. (2001)
―"― | Pupuru flour | Shittu et al. (2005)
―"― | Dark cassava flour | Essers (1994)
―"― | Yeast fermented cassava flour | Oboh and Akindahunsi(2003) Oboh and Akindahunsi (2005) Akindahunsi et al. (1999)
Unfermented | Tapioca flour | Chiste et al. (2012)
―"― | Cassava flour | Aryee et al. (2006)
―"― | Cassava flour | Ogbonna and OkoLi (2010)
―"― | Cassava flour | Hossen et al. (2011)
―"― | Cassava flour | Defloor et al. (1995)
―"― | Cassava flour | Derkyiet al. (2008)
―"― | Cassava flour and gari | Bradbury (2005)
―"― | Cassava flour and starch | Doporto et al. (2012)
―"― | Cassava flour | Shittu et al. (2002)
Composite | Cassava-wheat flour composite | Shittu et al. (2015b)
―"― | Cassava-wheat flour composite | Akinrele (1973)
―"― | Cassava-wheat flour composite | Shittu et al. (2008)
―"― | Cassava-wheat flour composite | EggLeston et al. (1993)
―"― | Cassava-wheat-soybean flour composite | Oluwamukomi et al. (2011)
Properties Related to Industrial Standards and Specification Published documents to guide food trade within and across national boundaries, also known as food standards, are available for different raw and finished food products. Each country and region of the world is separately responsible for developing standards. The international quality standards for food products are developed by the Codex Alimentarius Commission (CAC). The African Organization for Standardization is responsible for development and harmonization of African Standards to enhance trading within the region. The general quality specification for raw and finished food products traded within Nigeria is provided by the Standards Organization of Nigeria (SON). There is some agreement between specification by Codex Standard (CODEX STAN 176-1989), African Standard (ARS 840: 2012) and Nigerian Industrial Standard (NIS 344: 1997) for edible cassava flour.
Codex Standards for edible CF stipulated that CF be free from abnormal flavors, odors and live insects, filth (impurities of animal origin, including dead insects). The various codex standards for CF are presented in Table 10.1.3.
Table 10.1.3 Standards for CF
S. no. | Parameter | Standard
1 | Moisture (max) | 13%
2 | Fiber (max) | 2%
3 | Ash (max) | 3%
4 | Fine flour | 90 % of CF passes through 0.6 mm sieve
5 | Coarse flour | 90 % of CF passes through 1.2 mm sieve
6 | Hydrocyanic acid (db, max) | 10 mg/kg
7 | Sulfated ash (max) | 0.5%
8 | Starch | 65–70%
9 | Total acidity | 1%
Source: CAC, 1989; ARS (2012)
Nigeria is distinctly known to have a history of producing and consuming some fermented CFs (lafun, fufu andpupuru) that have many similar characteristics (Shittu et al., 2005). Out of these, fufu is the most commercially traded world-wide. However, to date, no local industrial standard is available for lafun and pupuru (ikwurikwu), probably due to their lower export (or commercial) values.
Physical Properties The color of CF is an important physical property that influences its acceptability and potential application. It varies according to root variety and processing method. The bitter cassava roots give whitish flours, whereas yellow fleshed roots give off white color. The color of CF may be measured instrumentally (using colorimeters) or may be assessed sensory-wise. The Hunter or CIE-Lab color indices are often used. Both color systems consist of lightness (L), greenness-redness (a) and blueness- yellowness (b) color spaces. It is often reported as whitish (60 < L < 110) with low yellowish tint (12 < b < 15), as found in flours from white fleshed roots (Shittu et al., 2007). Some yellow fleshed or carotenoid cassava roots may have higher values for greenness and yellowness.
Pasting Properties The pasting properties of flour shows the behavior of its flour/water suspension when cooked. It indicates the potential end use of the flour for cooking purposes. The peak viscosity indicates the maximum viscosity attainable during cooking of flour suspension to near boiling point (95 °C). Breakdown viscosity also indicates the stability of the paste when retorted or subjected to prolonged heating. Setback viscosity indicates tendency of the cooked paste to undergo retrogradation. The pasting temperature and peak time are both indices of ease of cooking amount of energy required to cook the aqueous suspension of the flour. The crop type, variety, particle size of flour, relative composition of starch, protein, fiber and fat affect the pasting characteristics. Table 10.1.4 shows the typical pasting behavior of flours from some roots and tubers. CF is known to have an intermediate thickening power among flours (Table 10.1.4). The pasting viscosity is slightly higher than the new cocoyam flour (Xanthosoma sagittfolium). According to Hossen et al. (2011), potato showed the greatest paste viscosity and the least hot paste stability among the different flours studied.
Table 10.1.4 Pasting properties of some flour from root and tuber crops
Crop | Peak Viscosity | Trough | Breakdown Viscosity | Setback Viscosity | Final Viscosity | Peak Time | Pasting Temp | Source
Dioscorea dumetorum | 3180.5 | 1919.0 | 1261.5 | 2806.5 | 887.5 | 4.67 | 83.95 | Abiodun et al. (2014)
Dioscorea alata | 4115.0 | 2326.0 | 1705.0 | 4064.0 | 1750.0 | 4.87 | 68.40 | Babajide and Olowe (2013)
Dioscorea rotundata | 2544.0 | 1301.6 | 1241.0 | 2767.0 | 1469.3 | 5.74 | 880.85 | Babajide and Olowe (2013)
Manihot esculenta (Min) | 2596.8 | 627.6 | 1252.8 | 884.4 | 201.6 | 3.87 | 76.80 | Shittu et al. (2008)
Manihot esculenta (Max) | 3678 | 1850.4 | 2532 | 2706 | 861.6 | 4.47 | 81.72 | Shittu et al. (2008)
Xanthosoma sagittfolium | 1941.6 | 1870.6 | 71.0 | 2926.6 | 1056.0 | 5.77 | 61.73 | Ejoh et al. (2013)
Colocasia esculenta | 2407.1 | 1984.6 | 422.5 | 3244.6 | 1260.0 | 5.04 | 61.93 | Ejoh et al. (2013)
Ipomea batata | 496 | 215 | 281 | 192 | 302 | ― | ― | Hossen et al. (2011)
Solanum tuberosum | 1087 | 131 | 956 | 742 | 345 | ― | ― | Hossen et al. (2011)
Thermal Properties The behavior of starch granules when subjected to heating helps to explain how easily starchy material can be modified with heat treatment. CF, like cassava starch, has a single thermal event associated with the gelatinization of starch. According to Doporto et al. (2012), the onset temperature of gelatinization of cassava starch was about 52 °C, whereas that of flour from the same root material was between 67 and 71 °C. This indicates that presence of other materials like protein, fat and fiber in CF could have influenced the gelatinization behavior. Grated cassava gave flour with a significantly lower onset temperature than chipped cassava.