Our studies in taro wheat composite dough revealed no remarkable difference on the dough alveographic characteristics of raw and parboiled taro corms (Himeda et al., 2014; Njintang et al., 2008). Table 9.2.2 presents the alveograhic parameters of wheat taro composite dough as affected by parboiling.
Table 9.2.2 Alveographic characteristics of wheat taro composite dough as affected by the level of taro flour, Ibo coco variety
Taro level in the composite
Alveograhic characteristics | Taro treatment | 0 | 10 | 20 | 30
P | Raw | 95 | 115 | 133 | 159
―"― | Parboiled | 99.1 | 117.2 | 137.8 | 165.7
G | Raw | 18.4 | 16.2 | 13.3 | 10.8
―"― | Parboiled | 19.7 | 15.6 | 11.5 | 10.4
L | Raw | 68 | 53 | 36 | 23
―"― | Parboiled | 78.0 | 49.0 | 26.8 | 22.3
W | Raw | 241 | 231 | 203 | 162
―"― | Parboiled | 281 | 235 | 167.5 | 161
Ie | Raw | 55.8 | 50.3 | 0 | 0
―"― | Parboiled | 59.8 | 55.7 | 0 | 0
Rupture pressure (P), extensibility (L), strength (W) and elasticity index (Ie), extensibility index (G), are parameters generated automatically by the Chopin alveograph
Generally, parboiling taro corm of the Ibo coco variety has no significant difference on the alveograhic parameters. In addition, incorporation of taro into wheat flour generally modifies the alveographic characteristics of the composite dough. In particular, up to 10 % substitution of wheat, the elasticity index of the dough, Ie, was in the range values 35–60 % reported for some wheat varieties in France. Beyond 10 % substitution, the elasticity diminished rapidly and a zero percent elasticity was observed at 15 % substitution. Himeda et al. (2014) revealed that the maximum level of substitution with precooked taro flour depends on taro variety. In fact, they obtained an elasticity value of 49.2 % for a 15 % wheat substitution with taro flour variety egg-like, while at the same taro level for the Ibo coco variety, Ie was equal to zero. In theory, the dough must exhibit an elasticity to be used in bread preparation and a minimal limit of Ie (40 %) was suggested for French bread. This suggests that substitution with taro above 10 %, and exceptionally 15 %, is not advisable (Njintang et al., 2008). This level has been shown to be improved by adding gums. In addition, the substitution level of taro can be improved by adding the taro flour to the wheat dough already prepared.
In most of the studies published on the use of taro flour in bread formulation, the wheat and taro flours are mixed at the same time. Under these conditions, the gluten is diluted and the dough gluten network also. It is worth mentioning that bread is a leavened and precisely a yeast raised product. Leavening is produced only if the CO2 gas is trapped and held in a system which expands along with it. In this respect, formation of correct dough and batter to trap leavening gases and the fixing of these structures by the application of heat is the main challenge in the preparation of composite bread. Mondal and Datta (2008) outlined three different methods used in the production of baked products: the straight dough method or one-step ingredient mixing, the sponge and dough method or the two-step ingredient mixed method, and the Chorleywood method where all the ingredients are mixed in an ultra-high mixer for a few minutes.
Adding taro flour after the formation of wheat dough will not affect the strength of the gluten network and in this respect, the expansion of the dough during fermentation. However, such a study of not mixing taro and wheat flour in the one-step method has not been done on taro wheat composite dough and bread, and needs to be investigated. In addition, taro flour has a high ability to absorb water as compared to wheat flour. In this respect the quantity of water added should vary with respect to the quantity of taro in composite, but this has not been investigated yet.
9.2.2.2 Cookies and Biscuits
Also called biscuits in the UK, cookie describes a flat crisp baked product. Biscuits are one of the most popular products, because they are economically cheaper as well as considered as gifts for infants and school-going children. Indeed cookies are made in a wide variety of styles using an array of constituents which include flour, water, sugar and fat. They can be divided into cabin biscuits, semi-sweet and hard-sweet biscuits, sugar-snap cookies, etc. Snap cookies contain 47.5-54 % of flour, 33.3-42 % of sugars and sweetener, and 9.4-18 % of fat (Teckle, 2009). Sugar snap cookies typically are made from 225 g of soft wheat flour, 64.0 g shortening, 130 g sucrose, 2.5 g sodium bicarbonate, 2.1 g salt, 33 g glucose solution (8.9 g of glucose hydrous in 150 ml of distilled water) and 16.0 g distilled water (Ryan and Brewer, 2006). The term “snap” refers to the audible sound when the cookie fails under a load (Pareyt and Delcour, 2008).
Cookies generally have a low final water contents (1–5%) (Pareyt and Delcour, 2008) and other ingredients including milk, salt and aerating agents (Olaoye et al., 2007). Soft wheat is the most widely-used cereal for cookie-making in that it provides the necessary gluten to the biscuit structure. Although gluten was found to be crucial in making cookies, it has been stated that low gluten content and weak gluten strength is generally desired for a good sugar snap cookie. Practically, biscuit manufacturing starts with creaming which is mixing of all ingredients to obtain a soft dough. In the procedure of dough production, shortening, generally margarine, and sugar are mixed for some minutes in a mixer, and refined wheat flour and baking powder are subsequently added with some quantity of water. After mixing, the dough is sheeted to a given thickness, cut into pieces of geometrical size with a die, and is baked at temperature 150–200 °C for 20–30 min.
Several products can be used in cookie production, either by substitution of basic ingredients or by addition, and this may affect its quality, particularly the textural properties. In this respect taro flour has been a subject of wheat flour substitution in the production of cookies. A very long time ago, Payne et al. (1941) reported that in cookies as high as 60 % taro flour could be used. Some 50 years later in the same country, Nip et al. (1994) formulated snap-type cookie with taro flour by replacing wheat flour and drop-type chocolate chip cookie formulation by the replacement of 51 % of the wheat flour with taro flour in a commercial formulation. Both cookie formulations developed were found to be highly acceptable. Ojinnaka et al. (2009) had studied the effect of taro starch modification on functional and sensory qualities of cookie. They concluded that substitution of some part of wheat flour with taro starch in the production of snack products will help minimize the rate of post-harvest losses and encourage taro cultivation.
Teckle (2009) evaluated the physicochemical characteristics and sensory qualities of cookies made from taro-wheat composite flour as affected by the proportion of taro and the baking temperature. Taro flour was used in the blend at varying proportions of 33.3, 66.7 and 100 % following a mixture simplex lattice design, whereas 140, 150 and 160 °C baking temperatures were tested for baking. Sugar snap cookie formulation was produced based on the ingredients shown in Table 9.2.3 according to the standard AACC formulation for baking quality of cookie flour (Method 10-50-D, AACC, 1983).