Cyanogenic Potential The cyanogenic potential (CNP) is a critical quality factor of CF for both trade and utilization purposes. Although the CNP is reduced by fermentation, flours from bitter varieties of cassava may still contain CNP higher than the acceptable limit of 10 mg/kg by standards. Farmers still cultivate high cyanide cassava varieties due to the perceived higher resistance to pests and diseases. The products are also believed to have superior sensory quality compared to the low cyanide varieties (Chiwona-Karltun et al., 1995). Bradbury (2005) reported a simple wetting method for detoxifying CF having a reasonable amount of linamarase activity. The total cyanide content reduced about 3-fold over 5 h. Addition of exogenous linamarase increased greatly the rate of breakdown of linamarin in the flour. The detoxification process was also found to be pH dependent.
Water Vapor Adsorption Properties The study of water sorption phenomenon allows us to predict the stability and quality during packaging and storage of food products. The plot of equilibrium moisture attainable by a material at constant temperature and varying relative humidity or water activity value is called sorption isotherm. CF is highly hygroscopic due to high water affinity of its starch and fiber. Regardless of whether fermented or not, previous studies on the water vapor adsorption properties of different cassava flours at various practical storage conditions indicated that CF has a type II isotherm curve (Chiste et al., 2012; Doporto et al., 2012; Sanni et al., 1997; Shittu et al., 2015a). The water vapor adsorption isotherm of fufu, pupuru and lafun flours at 27 °C is given in Figure 10.1.5. A very wide range of monolayer moisture values have been reported for CF (5-23 % dry basis). This might be due to differences in the composition, processing method, and so on. The monolayer moisture contents of cassava flours from previous studies generally range between 5 and 25 % (dry basis). According to Shittu et al. (2015a), the difference in the drying method employed in producing lafun, fufu and pupuru did not yield significant differences in the adsorption data at 27 and 35 °C.
Figure 10.1.5 Water vapor adosprtion isotherm of fufu, pupuru and lafun flours at 27 °C (source: Shittu et al., 2015a).
10.1.2.3 Utilization of Cassava Flour
Fermented CFs has limited applications. Traditionally, they are used to prepare stiff dough (amala), often consumed by swallowing whole with some special vegetable soups or stews in many West African countries. However, unfermented or high-quality CF (HQCF) has continued to attract growing food and non-food applications. The bakeries and confectioneries mainly use HQCF as an ingredient in gluten-free or composite baked products. Snack foods such as puff-puff, chin-chin, pies, etc. are made from 100 % HQCF or composite cassava-wheat flours. Some chemical industries use HQCF as feed materials in adhesive and glucose syrup manufacture.
Applications of HQCF in Baked Product Manufacture Use of HQCF as a composite material in wheat flour (WF) for bread-making has been explored since the 1970s in Nigeria (Akinrele, 1973). However, substitution of up to 10 % wheat flour with CF has gained legislation support in the country since 2004 (Shittu et al., 2007). The major drawback of commercial use of composite flour in baked goods manufacture is the baker’s poor technical know-how, inappropriate baking facilities and poor process controls. Most bakeries in Nigeria still use mud-baking ovens with poor baking temperature control. The manual dough preparation used predominantly by the bakers is not efficient to handle the more complex and delicate dough system presented by composite cassava-wheat flour. WF mills with government mandate are now compositing WF with varying levels of HQCF. With this development, the government and private sectors have continued to organize periodic participatory training workshops for bakers to improve their technical skills on composite baked product manufacture. A lot of research and development efforts are still required on the commercial scale to optimize the use of HQCF as a bakery ingredient. Lack of enough domestic capacity to generate the quality and volume of cassava flour needed and poor cassava flour supply chains could also militate against the implementation of the HQCF inclusion policy (Ohimain, 2014).
Studies have shown that gradual quality impairment ensued as the amount of HQCF inclusion is increased for composite bread-making (Eggleston et al., 1993; Khalil et al., 2000). In addition, the cassava root genotype had significant influence on the quality of composite bread (Eggleston et al., 1993; Shittu, 2007; Shittu et al., 2008) (Figure 10.1.6). However, studies correlating HQCF quality with product quality are scarce. Shittu et al. (2008) reported that NPK fertilizer application during cultivation of cassava caused significant differences in the cassava flour properties. This further influenced the composite bread quality (Figure 10.1.6). A recent model study has indicated the possibility of predicting the sensory quality of composite cassava-wheat bread from CF properties (Shittu et al., 2015b). Gelation capacity of CF was the most influential flour property affecting the sensory acceptability of composite bread.
Figure 10.1.6 Composite bread sample by substituting 10 % of WF with flours from different cassava genotypes bread by IITA (98/0002, 99/6012, 98/0002, 92b/0061, 82/00058) grown with or without NPK fertilizer (source: Shittu, 2007).
Noodle Archaeological facts have shown that consumption of noodles as a food product dates back about 4000 years (Lu et al., 2014). Currently, it is consumed world-wide across all socio-economic strata. The world’s noodle market is concentrated in Asian countries, with China being the largest, consuming about 46.2 billion packets in 2013 (WINA, 2014). Noodles were originally made from mung bean flour. Later, wheat flour replaced mung bean flour due to the issue of availability and cost. Nowadays, due to some health and economic reasons, gluten-free flours are now being prospected to partially (Charles et al., 2007) or completely replace wheat flour for noodle manufacture (Nwabueze and Anoruoh, 2009; Purwandari et al., 2014).
Few scientific studies on the use of CF for making noodles have been published. Nwabueze and Anoruoh (2009) studied noodle-making properties of flours from eight cassava mosaic disease-resistant clones. The key sensory attribute responsible for difference in the noodle samples was the texture. Composite flour CF-WF mixture was used to make white noodles (Charles et al., 2007). The noodles had high tensile strength, cutting force and bite force. The texture of the product was improved by adding cassava mucilage. Vijayakumar et al. (2010) also reported reduced sensory acceptability of composite flour noodles score with increased CF content. Purwandari et al. (2014) studied the effect of water in pre-gelatinized flour as well as proportion of gathotan (a fungal fermented flour) to pre-gelatinized flour on noodle quality. Increased proportion of gathotan in the flour mixture caused greater hardness and adhesiveness. The main predictors of overall acceptability for the gathotan noodle samples were the mouth feel and aroma.