Table 9.2.3 Formulation of the snap taro cookie
Quantity required (%)
Raw materials | (Teckle 2009) | Ryan and Brewer (2006)
Wheat (and taro) flour | 45.5 | 47.4
Baking powder | 0.5 |
Sodium bicarbonate | ― | 0.5
Vegetable shortening | 13.0 | 13.5
Sugar/sucrose | 27.0 | 27.4
Sweetener/glucose | 7.0 | 0.4
Water | 3.3 | 10
Seasoning | 2.73 | -
The physicochemical characteristics of cookies were evaluated in terms of proximate composition, energy value, water absorption capacity (WAC), oil absorption capacity (OAC), cookie diameter and thickness, spread ratio and cookie breaking strength (texture). The cookie sensory qualities were evaluated in terms of colour, flavour, crispiness and overall acceptability. They observed that increase in taro proportion from 0-100 % in the blend led to a significant increase in moisture (1.75-2.15 %), fiber (0.53-1.67 %), crude ash (2.10-3.89 %) and carbohydrates (73.18–75.30 %) contents in the cookies, while the proteins (5.37-3.70 %) and fat (17.07–13.35 %) content significantly reduced. The change in biscuit composition reflects the difference in the composition of taro and wheat flours used in the composite.
Generally, as reported earlier, taro flours are low in protein and lipid and high in carbohydrate, ash and fiber content (Himeda et al, 2014) as compared to wheat flour. The high moisture content of the biscuit was ascribed to the high water retention capacity of taro, which could have improved resistance to moisture evaporation during the baking process. In fact the water holding capacity of taro flour was 2.37 ml/g, about twice the value determined for wheat flour (1.2 ml/g). The temperature only had a significant effect on the moisture and carbohydrate contents of the cookies and not on protein, fat, crude fiber and ash contents.
Because of the low level of proteins and lipids in the taro flour, their incorporation into wheat flour is expected to reduce the protein content of the composite flour and thus to significantly influence the rheology of dough and texture of products made from such composites (Njintang et al., 2007). In this respect, Teckle (2009) observed that the breaking strength of the cookies significantly increased from 13.5-28.7 N as the taro level increased from 0-100 %. When taro level increased from 0-33.3 % in the blend, no significant change was observed on the breaking strength of cookies. According to Tyagi et al. (2006), the breaking strength of a cookie is one criterion that measures the hardness of a biscuit, an important mechanical characteristic of biscuits since it determines the perception in the mouth and acceptance of a product (Shrestha and Noomhorm, 2002). Similarly, significant decrease in diameter (4.85-4.06 cm), thickness (0.57-0.52 cm) and spread ratio (8.52-7.89) of the cookies was observed as the level of taro in the blend increased with no significant difference between taro proportions of 0 and 33.3 %. Thus increased level of taro flour densified the cookies, which may reflect the high density of taro flour (0.80 g/ml) as compared to wheat flour (0.50 g/ml).
According to some authors (Pareyt and Delcour, 2008), the high initial moisture content of the wheat flour (14 %) could have contributed to less densification of the cookies by decreasing the dough stiffness, consistency and cohesion. Theoretically, rapid partitioning of free water to hydrophilic sites during mixing increase dough viscosity, thereby limiting cookie spread (McWatters, 1978). In addition, the high water holding capacity of taro flour makes water less available to dissolve the sugar (soluble components), and therefore the viscosity will be higher causing slower rate cookie spread (Pareyt and Delcour, 2008). In relation with the texture analysis, the color, flavor, crispness and overall acceptability of the cookies diminished generally as the level of taro in the blend increased with no significant change up to 33.33 % taro level. The results of overall acceptability confirmed that replacing wheat flour with taro flour up to 33.3 % for cookie baking was fairly acceptable. The 33.3 % taro flour cookie was found not to be significantly different from the control cookies with all quality parameters except with protein, ash, carbohydrate, gross energy and crude fiber content.
9.2.2.3 Use of Parboiled Taro Flour in Biscuit Preparation: An Original Study
Teckle (2009) used raw taro flour obtained by the triple process of peeling, drying and grinding to pass through 500-pm mesh sieve (Njintang et al., 2006). As mentioned above, raw flour has the drawbacks of keeping the itching principle even after baking. This was however not highlighted by the sensory panel reported in Teckle (2009), suggesting that some taro varieties are free of the itching principle, but this is not always the case of those cultivated in most countries. We recently reported characteristics of wheat taro biscuit using parboiled taro flour (Himeda et al., 2014). Wheat flour was substituted with parboiled taro flour at 0, 5, 10, 15, 20, 25 and 30 %. Soft dough biscuit was produced by mixing fat (margarine, 150 g) and sugar (commercial sugarcane, 250 g) in the mixer (a Z-blade type, Moulinex, France) and blending for 2 min. The sodium bicarbonate (7 g) and salt (3.5 g) dissolved in some volume of eggs (2 eggs) were added, followed by the vanilla flavoured sugar (10 g). The composite flour was then introduced into the mixer, and the mixture blended for 7-10 min while during this process the remaining egg was added. The dough was sheeted 0.5 cm thickness and cut into circular shapes with a moulding shell. Baking was done at 190 °C for 8-10 min in a Michael Wenze Ideal oven (Michael Wenze, Arnstein, Netherlands).
The results revealed that all the composite biscuits were as acceptable as 100 % wheat biscuits except composite with 5 and 10 % taro variety RIN, which possessed higher hedonic score for all the attributes compared to 100 % wheat biscuits (Himeda et al., 2014). Generally this study showed that composite biscuit made with taro variety RIN had attractive sensory attribute, in particular flavour and taste. The mean nutrient compositions and energy contents of taro-wheat composite biscuits showed no significant changes on the crude lipids of biscuits, while a significant (p < 0.05) decrease in protein and increase in ash was observed following the increase in taro level. In addition, available sugars significantly decreased with increasing level of substitution with taro flour.
In the continuation of Himeda et al. (2014) work, we evaluated some physicochemical and nutritional properties of the biscuits. Soluble sugars and soluble protein content of the biscuits were measured according to Fischer and Stein (1961) and Devani et al. (1989), respectively. In vitro carbohydrates digestibility of biscuits was evaluated using human saliva freshly collected. AACC (1995) Standard method was used to determine biscuit volume, diameter, thickness and spread ratio. Diameter and thickness were measured on 25 randomly selected biscuits using a digital Venier caliper with 0.01 mm accuracy (Cappera precision, China) and the average calculated. The volume of each biscuit was calculated using the equation for a solid cylinder (n.r2.h) where the height (h) was equal to the thickness of the biscuit and r the radius. The biscuit spread ratio was calculated as a ratio of diameter to thickness of biscuits. Bulk density was determined as described by Singh et al. (2008) and the result expressed as g/cm3. The water absorption capacity (WAC) and water solubility index (WSI) of ground biscuits were determined as described by Phillips et al. (1988) and Anderson et al. (1969), respectively.