Nderitu (2010) studied the development of a snack from taro enriched with meat. Taro flours were prepared by peeling, slicing, pretreatment and grinding. Four pretreatments were used: unsoaked slices, soaking in water, soaking in water followed by parboiling, and soaking in water followed by boiling. The paste obtained was mixed with minced meat, comminuted and the mixture extruded into 60 mm artificial casing and the sausage obtained was pasteurized (70–75 °C internal temperature, 20 min), cut into discs and baked (160 °C). Taro and meat were mixed to achieve a product of 10 % protein. In this respect, 16 g of taro (containing 0.16 % protein) were mixed with 9.48 g meat (containing 26 % proteins). The sensory characteristics revealed that soaking in water gives the taro-meat snack of very high acceptability based on the high appearance and taste. Parboiling and boiling seemed to increase the binding characteristics of the sausage, but the products were less accepted than those obtained from soaked and untreated taro sample.
Bhattacharyya et al. (2006) studied physicochemical characteristics of extruded snacks prepared from rice (Oryza sativa L.), corn (Zea mays L.) and taro (Colocasia esculenta L.) by twin-screw extrusion. The corn, rice and taro flours were blended 100: 10: 9). The moisture content of the dough was adjusted to 15 % while three temperatures of the barrel were tested at 141, 150 and 159 °C. The screw speed was 475 rpm while the feed rate was constant at 28 g/min. The results obtained revealed that extractible protein decreased with extrusion probably due to inclusion of protein into new inter-chemical linkage such as non-disulfide covalent bond or the formation. The linkage was shown to be temperature-dependent with the high temperature inducing more chemical linkage, hence less solubility. This may also result from the formation of some polymers with very high molecular weight, as demonstrated by Li and Lee (1996). They observed that the breaking force of the snack decreased as the temperature of the vessel increased. During extrusion, the product expands and the molecules are reorganized, all this contributing to the change in breaking force. One of the significant changes in molecular structure occurred on starch, which was shown to gelatinize more at higher temperatures. Microscopic examination revealed that extruded samples had porous and open-celled structures, and granules at higher temperature were more flattened and sheared.
Rodriguez et al. (2011) developed extruded snacks using blends of taro and nixta-malized maize flours. A single-screw extruder with a barrel of 19 mm diameter and 20: 1 length to diameter ratio (L/D) was used. The screw compression ratio was 1: 1, the die 3 mm in diameter and the screw speed 60 rpm. The feed rate was 28g/min and extrusion temperature was varied from 140–180 °C. Taro and maize flours were mixed and the extrusion temperature varied following a central composite design. The results revealed that increasing the level of taro in the composite increases the expansion of the extrudates. The authors attributed the high expansion of the extrudates to the level of starch, which was higher in taro compared to maize.
Some researchers have reported that the level of expansion during extrusion is not only related to the starch content but also to the amylose content and degree of starch gelatinization during the process (Parker et al., 1999; Rampersad et al., 2003). In this study, the water solubility index, an indicator of degree of starch gelatinization, was shown to increase with increase in proportion of taro in the blend, while the fat absorption index diminished significantly. Overall, this study revealed that flour mixtures made from taro and nixtamalized maize flours, particularly in respective proportion of 85.4 and 14.6 %, produced puffed extruded snacks with good consumer acceptance.
9.2.3.2 Taro Chips or Crisps
Ukpabi et al. (2013) studied the acceptability of taro crisps in Nigeria. In the process of taro crisps production, corms were peeled, washed, chipped and brined with 1 % sodium chloride solution (for 10 min). After the brining operation, the natural mucilaginous materials on the treated corm chippings were removed by manual washing with clean water. The washed slices were deep fried in refined and crude palm oil. The results revealed that the crisps were highly accepted, irrespective of the type of oil used. In addition, the crude palm oil exhibited a very high content of total carotenoid. Therefore producing taro crisps, a snack food, would not only increase the use of taro, but also could play a role in the management of vitamin A deficiency in children and reproductive women in endemic areas in Nigeria.
Emmanuel-Ikpeme et al. (2007) studied the acceptability and storage stability of taro chips made from four different oils. Taro slices (2 mm thick) were deep fried at 220 °C for 20 min. After draining and cooling, the chips were salted and packaged. The sensory evaluation showed that the mixture of palm oil/groundnut oil (60: 40 % v/v) had the most desired flavour, while palm oil was rated significantly greater in colour intensity. The off-flavour was higher for soybean oil as a consequence of high rancidity intensity. The authors referred the off-flavour of the chips to the highest amount of linoleic acid in the soybean oil. Chips fried in groundnut oil and palm oil/groundnut oil blend had the highest rate in taste and the overall preference of chips fried in groundnut oil were rated 5.3/9, similar to palm oil/groundnut oil blend and soybean oil.
During storage, all chips underwent oxidation with the extent of oxidation depending on the type of oil. Irrespective of the storage time and condition, the peroxide value was higher in chips made from soybean flour while palm oil, palm oil/palm olein oil blend and palm olein oil had the lowest. Under dark storage the peroxide value increased less than under light storage; after 3 weeks the peroxide value increased drastically and the chips were no more acceptable.
Chinnasarn and Manyasi (2010) studied the chemical, physical and sensory characteristics of restructured strip product made from taro. Restructured taro strips were prepared by mixing native taro flour, pregel taro flour and rice flour with 15 % mal-todextrin, 1 % lecithin, 13 % shortening, 1.8 % salt, 3.5 % sugar and 75 % water. After mixing, the dough was sheeted and cut into strips of 0.5 cm thickness and 6 cm length before being fried at 160 °C for 1 min. A mixture design was applied to check the optimal mixture of native starch (level 25–60 %), pregel taro flour (0-10 %) and rice flour (25–40 %). Sensory evaluation done by a panel of 30 persons revealed on a 9 point hedonic scale that the optimal mixture was 60 % native taro flour, 10 % pregel taro and 30 % rice flour. With this optimal mixture, the saltiness, the sweetness and the brown colour were highly accepted as compared to the ideal strip, but the intensity rating of crispness was lower.
A test of the effect of baking powder (0–5%) addition to the flour mixture was done and the results revealed that increasing the level of baking powder induced an increase in compression force, suggesting a high expansion of the product during frying with more crispness. At 3 % baking powder, the restructured taro strip had the highest overall acceptance score. Taro chips processing has been an interesting research subject in Hawaii and today is available on a commercial scale. Hollyer et al. (2000) reported technical considerations for taro chips manufacturing, from the farm production of taro corms to the handling and packing of the chips. Generally, low moisture corms performed well in chips processing. In this respect, the wet-grown taro variety performed badly in chips manufacturing, while upland grown taro, particularly the Chinese Bun long variety, is considered to be the best for chips. Under these growing conditions, taro corms are low in calcium oxalate, the itching principle and chips have distinctive purple strand. Because of the difference in moisture distribution in the corms, chips made from the bottom of the corm, with the lowest moisture content, are rated better in appearance than those made from the top part. The level of nitrogen fertilizer also affected the quality of the chips, with higher nitrogen yielding lower dry matter. Taro corms are recommended to peel, to slice 3/64 inches thick, and to soak for removal of sticking materials. The slices are deep fried in oil at 125–180 °C for 2 min. After frying, the chips are drained on adsorbent paper and salted or flavoured while they are still warm. Exposing the chips to light in clear bags reduces shelf life, while opaque laminated plastic is the best material for chip bags.