1 | Selection of raw material, peeling, slicing (5 mm), air drying (60 °C/20 h), freeze drying (60 °C/24 h) and milling (0.18 mm). | Nip et al. (1989)
2 | Selection of raw material, peeling, slicing, soaking(overnight in water), immersion (0.25 % sulphurous acid for 3 h), blanching (boiling water for 4–5 min), drying (57–60 °C) and milling. | FAO (1990)
3 | Selection of taro corms, peeling, trimming, slicing, drying (60 °C/20 h), milling, packaging and heat sealing. | Jane et al. (1992)
4 | Selection of taro corms, washing, draining, drying (45 °C/48 h), milling, screening (35 screen, 0.25 mm diameter) and storage under refrigeration. | Arnaud-vinas and Lorenz (1999)
5 | Selections of taro corms, washing, peeling (0.5 cm), drying (oven at 45 ± 2 °C), milling (500 pm) and storage (4 °C). | Njintang (2003)
6 | Selection of taro corms, washing, hand peeling and trimming, slicing, drying (air convection at 50 ± 2 °C), milling (hammer mill) and screening (500 pm). | Aboubakar et al. (2008)
7 | Selection of taro corms, washing, peeling, jagging, washing (90 °C/5 min), drying (65 °C/5 days), milling (Forplex type grinder) and screening (180–500 pm). | Andre et al. (2009)
8 | Selection of taro corms, cleaning and rinsing, peeling and slicing (2–3 cm), drying (45 °C/24 h) and milling (60 mesh). | Ammar et al. (2009)
9 | Selection of raw material, peeling and washing, cutting (1–2 cm), slicing (5mm), soaking (sodium metabisulfite, 0.075 % for 5 min), drying (hot air oven at 30 °C/40 h), milling, screening (300 pm) and storage (room temperature). | Aprianita et al. (2009)
10 | Selection of taro corms, peeling, steeping (25 °C/10 min), washing, slicing (2 mm), cooking (30 min), draining, drying (oven at 60 °C), milling (hammer mill), screening (300 micron). | Ikpeme-Emmanuel et al. (2009)
11 | Selection of taro corms, washing and slicing, blanching (90 °C/2 min), drying (50 °C, hot cabinet drier for 4 h), grinding (laboratory mixer) and screening (0.26 mm). | Kaur et al. (2013)
12 | Selection of taro corms, washing, peeling and draining, slicing (1/4") and washing, drying (mechanical dryer, 60 °C/24 h), milling (attrition machine for 15 min), packaging (polyethylene bags) and storage. | Sanful (2011)
13 | Selection of taro corms, washing and peeling, cutting (2 cm thick), boiling (0, 20, 35 and 50 min), draining of water, exposure to air (20 min), cutting (5 mm thick), drying (52 °C, ventilated oven for 48 h), grinding (hammer mill), screening (250 pm), packaging (into airtight sealed plastic bags) and refrigerated storage. | Amon et al. (2011)
14 | Selection of raw material, washing, peeling and slicing (2–2.5 cm thick), soaking (tap water), fermentation (24 and 48 h), draining, drying (cabinet dryer at 60 °C/24h), milling and screening (45 pm). | Oke and Bolarinwa (2012)
15 | Selection of raw material, washing, peeling, rewashing, chipping (mechanical chipper), drying (metallic solar drier for 3 days), roasting (15–20 min), grinding, screening (180–500 pm) and packaging. | Darkwa and Darkwa (2013)
16 | Selection of raw material, washing, peeling (5 mm thick), slicing (1 cm thick), dipping in three different solutions (water; corn infusion (45 % m/v and maceration in water for 3 days)); tamarind infusion (45 % m/v and maceration for 3 h in water)], Alteration, sun drying, grinding and sieving (500 pm). | Soudy et al. (2014)
9.1.5.3 Properties of Taro Flour
The method of processing can affect physico-chemical and functional properties of taro flour. Taro flours possessing a higher water absorption capacity and a higher water solubility index give gels with a higher consistency index (Mbofung et al., 2006). Taro flours produced in a pilot level showed similar physiochemical properties to the cereal conventional flours (www.bakeryandsnacks.com).
Heat processing affects the functional properties of taro flour, therefore blanching may also induce changes in different properties. The blanching reduces the oil absorption capacity (OAC) of taro (Kinsella, 1976). Water absorption capacity is desirable in food systems to improve yield and consistency and give body to the food (Osundahusi et al., 2003). The decrease in protein solubility due to heat can impair the foaming and emulsion ability. As a consequence, raw taro flours exhibit a relatively higher foaming capacity than the gelatinized ones. Furthermore, the foam capacity, foam stability and whipping ability are generally inferior compared to wheat flour. Addition of salt up to 2 % concentration in the flour suspension increases the foam capacities of taro and wheat flours (Godoy et al., 1992). Blanching can affect the swelling capacity of taro. Reduction in swelling capacity upon blanching is attributed to starch degradation into dextrin, which does not swell. Taro flours display higher gelatinization temperatures and lower paste viscosities than those of their starch counterparts.
Increasing the drying temperature of taro slices affects the properties of the flour, such as the water solubility index and water absorption capacity, as well as its performance in gel formation (Njintang, 2003). The foaming capacity of taro flour is significantly affected by the drying temperature and the precooking time (Njintang and Mbofung, 2006). Other studies have suggested the negative effect of heat treatment on the foaming properties of flour made from taro or common bean (Tagodoe and Nip, 1994). In general, a significant decrease is observed in foam capacity with an increase in the precooking time. The effect of precooking time on the foam capacity is dominated by the precooking time, 0 and 20 minute (Tagodoe and Nip, 1994).
Large taro corms possess higher solubility than small taro corms (Tattiyakul et al., 2005). Addition of taro flour to wheat flour significantly increases WAC from 132 % (wheat flour) to 156 % (composite flour consisting of 30 % taro flour), while the Ret-rogradation Index (RI) significantly decreases from 38 % to a mean value of 22 % (Njintang et al., 2007). Taro flour is significantly different from other flours, due to its high ash, crude fiber, lower fat and protein content and exhibits lowest L*, AE, foaming capacity (FC) and highest WSI (water solubility index), WAC (water absorption capacity) and OAC (oil absorption capacity), as compared to rice and pigeon pea flour (Kaushal et al., 2012).
Njintang (2003) studied the functional properties of Cameroonian taro flour. The lower protein, fat and starch content and higher sugar and fiber content in taro flour as compared to wheat flour are reported. Water and fat absorption capacities of raw and blanched taro flours are higher, whereas the foam capacity, foam stability, whippability and nitrogen solubility are inferior compared to wheat flour (Godoy et al., 2007). The onset gelatinization temperatures of the taro flours varied from 55.2-65.49 °C, whereas those of the starches were in between 48.08 ± 2.46 °C and 64.37 ± 2.35 °C. The water absorption capacity varied from 240–470 % and 60-250 % for the flours and starches samples, respectively (Aboubakar et al., 2008). Taro flours possess a higher solubility index than their starch counterparts.
The chemical composition and functional properties of taro flour differed significantly from different botanical sources (Table 9.1.6). The sorption study also revealed the high ability of the taro flours to absorb water compared to their starch components (Aboubakar et al., 2008). The taro flour exhibited highest WAC (2.2 g/g) and lowest foaming capacity (12 %) in comparison to other flours (soybean, corn and potato) (Kaur et al., 2013). The high WAC and peak viscosity of taro flour makes it a good body providing agent and can thus be used as a thickener or gelling agent in various food products. The paste formed by taro flour as a result of heating is stable upon cooling, which can prove to be advantageous in formulations where starch stability is required at low temperatures (Kaur et al., 2013).