9.3.5 Taro Yogurt
During the year 1990, taro yogurt was the focus of some research in the United States. This has been a most exciting and far-reaching development of taro-based products. Worth mentioning is the definition of yogurt in the United States, which is a standardized food in the category of dairy products. In this respect, taro yogurt has been renamed taro gurt, but this is still under discussion. Taro yogurt production started with the identification of Lactobacillus sp (Lactococcus lactis, Lactobacillus plantarum, Leuconostic lactis, Tetragencoccus halophilus and Weissela confusa) in the natural poi in Hawaii. All of them form white pin-point colonies, Gram-positive, catalase-negative, facultative anaerobes. These natural LABs were tested in yogurt production as compared to traditional commercial fermentation of yogurt. The first time they tried commercially available LABs used for making regular yogurt or sour milk, these LABs failed to grow in the taro paste medium. The pH did not drop above 4.7, much higher than the pH value of 3.9 common in a sour poi. The analysis of the fermented medium revealed that acetic acid and succinic acid accumulated at the same time as lactic acid. Inversely, when the LABs isolated from poi were used as the starter, they grew much more vigorously. In particular, Weissela confusa yielded the best growth and resilience in the taro paste. However, most of these species did not resist to acid pH and it has been difficulty to sustain the growth and bacteria counts after 3 days.
Studies are required to investigate the effects of using fruit and sugar in taro yogurt, since it is believed that these ingredients highly improve the taste and mouth feel. In addition, research for LAB-producing bacteriocin and pH-tolerant microorganisms isolated from natural fermented taro (poi) is to be encouraged, since these are important attributes for probiotic microorganisms and are great assets to human health.
9.3.6 Taro Noodles
The noodle is a food made from unleavened dough by stretching, extruding or rolled-flattening and cutting. In their fresh form they are refrigerated for short-term storage, while in the dry form they are stored for a long time, mostly for commercialization. They are commercialized throughout the world in a variety of shapes including long and thin strips which are the most common, whereas other shapes may include waves, helices, tubes, strings, shells, etc. The popularity of noodles is increasing because of ease of preparation and desirable sensory attributes, and a long shelf life. The basic ingredient of the noodle is wheat and it is estimated that about 30–40 % of total wheat flour consumption goes into noodles and similar products, especially in Asian countries (Miskelly, 1993). The noodle has been shown to offer alternative uses of tropical root and tubers, including taro. The partial substitution of wheat with taro not only offers other noodles variants with many new functionalities, but also may aid reduction of incidences of celiac disease or other allergic reactions (Rekha and Padmaja, 2002), and increase the use of taro corms.
Maga et al. (1993) evaluated the performance of taro flour in noodle preparation through extrusion. For this to be achieved, the dough temperature and moisture content were adjusted while the protein content of the noodle was enriched by using mung bean flour or soy proteins. Some years later, Arnaud-Vinas and Lorenz (1999) evaluated the cooking properties, the sensory and rheological properties of noodles made from wheat and taro blend. The noodles were prepared by mixing the blend flour (wheat and taro) with eggs (initially whipped for 5 min) and water. For each 100 g flour blend, 22 g of egg was needed. Because taro flour has a high water absorption capacity, more water was required to produce machinable dough. In this respect, while 100 g wheat flour needs 31 g water to obtain the dough, 50 % wheat substitution with taro (50 g wheat and 50 g taro) needs 54.5 g water. The dough was then extruded to obtain long strips 200 mm length, 6 mm width and 2 mm thickness, which were dried and packaged. It was found that as the taro level increased, the cooked weight, which is a measure of the amount of water absorbed during cooking, increased. The highest cooked weights were seen in 50 and 45 % taro level. While recommended solid lost flour should not be more than 9 %, all the noodles from wheat taro composite had solid loss less than 6.1 %. Increasing the level of taro in the flour increased the compression force of the noodle, with no significant difference between 0 % and 20 % taro levels. Increasing taro levels increased mixograph peak times. In addition, Rapid Visco-Analyzer peak viscosities and final setback values increased with increasing levels of taro in the blend. As the substitution level increased, the noodles lost the yellow tint color, one important quality factor for consumers’ acceptance in most markets.
From the sensory descriptors for 10 and 20 % taro samples and control, they found a strongly negative correlation between normal noodle aroma and taro flavor (r = -1.0, p < 0.001) and a strongly positive correlation between normal noodle aroma and overall acceptability (r = 1.0, p < 0.001). Taro aroma correlated with taro flavor (r = 0.96, p < 0.01). Texture was also affected due to substitution of red wheat flour with taro. In this respect, samples lost hardness as well as adhesiveness as the level of taro increased in the blend. In overall the aroma, the flavor and the general acceptability of the noodles decreased with increase in taro level.
Yadav et al. (2014) studied the effect of substituting wheat flour with taro flour (25 %) on the quality of noodles. Taro flour was prepared by peeling slicing, metabisulfite treatment, drying and milling through a 75 pm sieve diameter. The noodles were prepared by mixing flour with water and the dough was extruded (hand operator machine) and air dried. The results revealed that taro noodles exhibited lower cooking time, higher water absorption uptake, higher cooked weight and less gruel solid loss as compared to 100 % wheat noodles. According to Yadav et al. (2014), a good-quality noodle should have a short cooking time with little loss of solids in the cooking water. The cooking time seems to be reversely associated with the other cooking parameters. In fact, incorporation of taro into wheat may cause reduction in the force of the gluten network (Manthey et al., 2004), resulting in the faster moisture penetration and therefore leading to decreased cooking time (Table 9.3.1).
Indeed, the authors observed a negative correlation coefficient between the hardness and the water uptake of the noodles. Compared to 100 % wheat noodles, the taro wheat composite had lower peak and pasting temperature, and lower cold paste, set back and breakdown viscosity. Wheat taro noodles were generally accepted, but less than 100 % wheat noodle and wheat sweet potatoes noodle. In particular, wheat taro noodles had a less slippery surface necessary to help the product slide across tongue, were less firm probably as a result of dilution of gluten, and had a less attractive appearance due to becoming a little brownish instead of the light yellow color.
Table 9.3.1 Comparative cooking, textural and sensory properties of dough made from wheat flour and 50 % blends with taro and sweet potato
Properties | Wheatnoodles | Wheat-taronoodles | Wheat-sweet potato noodles
Cooking time (min) | 8.0 | 6.5 | 6.0