In West Africa, such as Ghana, the dough is rolled into small balls, dipped in soup and swallowed without being stewed (Figure 9.3.3b). In Cameroon, the dough is enlarged in the pan to give a flat circular form which is open at the middle and yellow soup is poured in (Figure 9.3.3a). The yellow soup is an alkaline emulsion of red palm oil containing 10–20 spices and meat. While in the past achu was reserved for special days to honorary elders, nowadays it has become a popular dish served in many specialized restaurants throughout the towns. With the shortening of the corms, the high demand of achu and the recent reduction of farm production due to the rot root disease, other starchy materials such as Xanthosoma and banana are mixed with taro corm during pounding. But the extent to which this is done and affects the texture of the achu is still to be studied.
Figure 9.3.3 Achu and yellow soup in Cameroon (a) and served form in the West Africa (b).
From the perspective of increasing the shelf life of taro corms, some traditional populations in Nigeria produce taro chips, also locally called achicha (Ihekoronye and Ngoddy, 1985). In achicha processing, the corms are boiled until they soften, the skin is peeled off and the flesh sliced 1 cm thick and sun-dried or smoked to obtained the dried chips. During the annual famine, the chips are ground in a mortar, and the flour is made into a smooth thick paste in hot water. Worth mentioning is the cocoyam flour commercialized by the Ghanaian enterprise TROPIWAY under the brand name Cocoyam FUFU Flour (Figure 9.3.3b). During the past 10 years, we have undertaken studies to determine the conditions of producing instant taro flour for the preparation of achu. The most suited variety, the boiling time to soften the tubers, the drying, grinding and the reconstitution conditions have been determined (Njintang, 2003). The production at industrial scale of instant achu by the National School of Agro-industrial Sciences, University of Ngaoundere, Cameroon is on the way (Figure 9.3.4).
Figure 9.3.4 Proposed flow diagram for the production of instant achu powder.
A market test of the instant taro achu proposed good-quality flour. All panelists knew how to prepare achu and all the constraints associated with it. Concerning the constraints in achu preparation, 84.2 % considered achu labour-intensive, 10.5 % time-consuming, while 10.5 % directed to other constraints. The observations made by the panel confirmed the initial problem that led to research on taro powder currently that is underway. All the consumers are unanimous that an alternative way of preparation of achu, which is less painful and less time-consuming, could foster consumption and increase incomes for producers. The commercialization will not only boost the economy but will pave the way for the commercialization of other different indigenous food products, obtained from roots and tubers.
9.3.12 Production of a Taro-based Spiced Soup: A Case Study
9.3.12.1 Introduction
Achu is very popular and is usually consumed with a yellow soup. Most often, consumers mix the soup with some quantities of achu paste to obtain a more viscous liquid before they swallow. Therefore, there is a need to develop a soup which can be served on different occasions. A soup is a liquid food prepared from meat, fish or vegetables combined with various other ingredients and often containing solid pieces. It can be thickened with different agents, including starch and cream. The spices that compose the yellow soup have been studied recently (Abdou et al., 2010, 2012) for their percentage and contribution to flavor in the soup, their macronutrient and micronutrient composition, phytochemical composition, and antioxidant and anti-inflammatory activities. It has been reported that spices, Dichrostachys glomerata, Scorodophloeus zenkeri and Xylopia parviflora, exhibited higher antioxidant and anti-inflammatory properties and provide the essential flavor of the soup. In order to promote the use of instant taro powder, the present study aimed at preparing a soup called OXISOUP with higher antioxidant properties, was undertaken.
9.3.12.2 Sampling and Oxisoup Preparation
Sampling The spices and taro corms used in this study were purchased from a market in the west region of Cameroon. Spices were carefully cleaned, sorted to remove defective ones and graded according to size followed by drying in a ventilated electric turning dryer (brand Riviera and Bar) at 40 ± 2 °C for 72 h. After drying, processed spice samples were ground into a fine powder using an electric grinder (Culatti, Polymix, France) equipped with a sieve of diameter 250 pm mesh. The powders obtained were sealed in polyethylene bags and stored at 4 °C until analysis. The taro flour used to prepare Oxisoup was produced as described by Aboubakar et al. (2008) with the red variety of Colocasia esculenta corms, locally called Ibo coco.
Preparation of Oxisoup For Oxisoup production, 1 liter of water was heated in a stainless steel container to 100 °C. Then 20 g of taro flour and the mixture of three-spice powder made of Dichrostachys glomerata, Scorodophloeus zenkeri and Xylopia parviflora, as per the Central composite rotatable design (CCRD) shown in Table 9.3.3, was gradually introduced into water. The mixture was stirred with a wooden spatula to avoid lumps. Common salt (NaCl) of 1 g was added and the whole was allowed to boil for 5 min on an electric hotplate. The resulting soup was served to the panelists for sensory analysis. The soup was stored in polyethylene bags at 4 °C for antioxidant analysis within a maximum of 6 h. The spices were mixed using a central composite rotatable design of RSM, as shown in Table 9.3.1. A Central Composite Rotatable Design of Response surface methodology (RSM) was used to estimate the effect of independent variables (D. glomerata], [X. parviflora], and [S. zenkeri],) on the antioxidant and sensory properties of Oxisoup.
Table 9.3.3 Coded and actual values (g/L) of D glomerata, Xparviflora and S zenkeri used in the Central Composite Rotatable Designs
Codes values
Processing factor (g/L) | -1.682 | -1 | 0 | 1 | 1.682
D. glomerata | 1.03 | 1.36 | 1.85 | 2.34 | 2.67
X. parviflora | 0.69 | 0.91 | 1.23 | 1.55 | 1.77
S.zenkeri | 1.06 | 1.35 | 1.78 | 2.21 | 2.50
The antioxidant properties of the soup were determined as the polyphenols content, flavonoids content and ABTS+ free radical scavenging activity. The amount of polyphenol compounds expressed as g gallic acid per 100 g of dry matter of soup was determined with a Folin-Ciocalteu reagent, according to the method of Gao et al. (2000). Flavonoids content (equivalent of mg quercetin per 100 g of dry mater) of soup was determined, as described by Mimica-Dukic et al. (1993). Evaluation of ABTS+ free radical scavenging activity was determined by following Re et al. (1999), and the results were expressed as equivalent of g Trolox per 100 g of dry matter.
All the soups were subjected to sensory parameters by the Hedonic method on a 9-point scale varying from 1 (dislike extremely) to 9 (like extremely). Numerical optimization was also carried out to determine the exact optimum level of independent variables leading to the optimum quality of Oxisoup. The desired goals for the response variable were chosen as maximized, while all the independent variables were kept within range.