9.3.2 Taro Ice Products
Ice cream is a frozen food typically made from milk and often combined with fruits or other ingredients and flavors. In this respect, the principal components of ice cream are fats (8-20 %), sugars (13–20 %), stabilizers/emulsifiers (0–0.7 %) and total solids (36–43 %) (Arbuckle, 1977). In comparison, ice bars are of solid texture with varying shapes, generally bar-shaped or cube-shape (Lu et al., 2002). According to the US Food and Drug Administration (FDA, 1976), an ice product comprised of at least 10 % butterfat and 20 % total milk solid should be called ice cream. Traditional taro ice products have been classified as unique by the Taiwanese consumers based on the flavor, smooth texture and special color that are particularly appreciated. Taro ice products are now the subject of industrial production throughout the world and particularly in the Pacific region.
Generally, taro ice bar products are more firm than taro ice cream products, and the firmness varies significantly among each group of products (Lu et al., 2002). The firmness of ice products is largely determined by the types of the products. It was observed that the flavor of taro ice products, and in particular ice cream products, were at the lower scores, suggesting that the flavor characteristic of the commercial taro ice products, especially for taro ice cream products, was not satisfied by their panelists. According to Chang (1997), the flavor of taro ice products may be affected more by the heat treatment during taro processing that might result in severe flavor evaporation, rather than the proportion of taro in the product.
The ice bar products were evaluated to be less greasy with better mouth feel properties, as shown by the lower fattiness scores (Lu et al., 2002). The ice bar products also received higher overall scores, indicating that there was an overall preference for the ice bar products over the ice cream products. Their compositions were shown to vary significantly within each ice product group, with differences greater among the taro ice bar products. This was thought to be due to the less homogenized solids in the ice bar products. Based on studies by Budiaman and Fennema (1987) and because the fat content has an effect on the stability of the air bubbles, it was speculated that the stability of the air bubbles in the cream is associated with the viscosity. Based on the free sugars measured from the samples, sucrose was the major sweetener employed for the commercial taro ice products collected in the present study, followed by lactose.
Huang et al. (2003) reported some trials towards the use of cooked taro paste to replace milk and other dairy ingredients in ice cream formulation. Taro ice cream was composed mainly of taro flour, hydrogenated vegetable fat and sugar. Taro ice cream (8 % fat and 1 % protein) had similar nutritional benefit as the frozen sorbet (1 % fat and 0 % protein), but with a taste and sensory attributes similar to a high fat (18 % fat and 4 % protein) premium ice cream. However, a number of minor ingredients had to be used in this taro frozen dessert to prevent the formation of large ice crystals. In addition, the patented technology suggested a longer time for taro ice cream to soften prior to serving due to its high starch content.
9.3.3 Frozen Taro
A ready-to-cook frozen taro was developed in the Northern Marianas Island (Oguromu, 2011). The processing involved boiling the corms followed by peeling, vacuum packaging and freezing. For the sensory analysis, the consumers were asked to boil the sample and analyze. No significant difference was observed among the samples. In addition, the nutritional quality of the samples also did not change significantly with the storage time. These results informed that the low-cost value-added product is highly acceptable and very helpful in extending the shelf life of taro during and after harvesting seasons.
Another variant of frozen taro is reported in Polynesia, where fresh taro corms are peeled, cut into pieces, packed in polyethylene bags and frozen (Garnier, 2004). Under these conditions, the corms are preserved for at least 6 months and highly acceptable to the consumers in that area, but a systematic study is required to look at the quality and safety of the product.
9.3.4 Preparation of Fermented Taro Paste
In Polynesia, taro is preserved and eaten in the form of a fermented paste locally called poi or ’ti’oo (Garnier, 2004). Stable for over a month, it is the most consumed and commercialized form of taro in that area of the world. Traditionally, poi is obtained by boiling the corms, peeling and mashing. The mashed paste is gently diluted in some water, acidified with lemon and pounded in a mortar to obtain a homogenous paste with a consistency of bread dough. During this operation, fibers are removed and the taro dough is wrapped in ti leaves and kept for 3 weeks, during which natural fermentation occurs producing organic acids. The fermented dough, consumed in association to their daily food, are generally mixed with coco milk, banana or boiled fish. Historically, because sea and air links to isolated islands were infrequent and unreliable, poi was an important alternative food source during periods of isolation, inclement weather patterns or low productivity seasons. Today, consumption of poi seems to be increasingly more restricted, and largely confined to traditional and ceremonial feasts and to consumption by older generations.
Gubag et al. (1996) reported the procedure of Sapal processing, a traditional fermented food made from taro in the northern coast of the Papua New Guinea and nearby offshore islands. The technology of Sapal preparation is similar to that of poi in Polynesia, a neighboring area, probably as a consequence of similar ancestral origin. In Sapal preparation, taro corms are cooked, peeled, grated and mixed with coconut cream and subjected to natural fermentation at ambient temperature. Traditionally, Sapal is used as a gift to neighbors on social occasion. Around the Huon Gulf and the Siassi Islands (the north coast of Papua New Guinea), an equivalent of Sapal called porong or polom is prepared, but the grated corm-coconut mixture is directly consumed without fermentation. Similarly, a product made in the Solomon Islands differs from Sapal by the size of the balls which is smaller. Generally the ratio of taro to coconut cream is 5: 1 and the texture is firmer, with a jelly-like consistency.
Gubag et al. (1996) evaluated the microbial population and some physico-chemical properties of Sapal. The taro-coconut cream mixture is a gelatinous pudding which is sweet in taste, and highly preferred by the majority of people in Papua New Guinea. When the cream product placed in a bowl is kept at the ambient temperature for about 6 h, fermentation occurs, and the fermentation seems to be restricted to a relatively few area. Fermentation of taro-coconut cream was identified primarily due to lactic bacteria, which is generally accompanied by a decline in pH value from 6.0–4.1. The lactic bacteria were hetero-fermentative and mainly made of Leuconostoc mesenteroides and L. paramesenteroides. The initial flora of Sapal probably originated from coconut cream. The pH obtained in this fermentation was too high to inhibit microbial alterations. Hence the Sapal preparation also favored the growth of a large population of aerobic and catalase positive bacteria.
The preparation of Sapal then is liable to carry some risk of transmitting food poisoning bacteria. Studies then need to be done to identify Lactobacillus that can grow to induce a drop of pH to about 3.9, the natural sour characteristics not only needed for preservation, but also accepted by consumers. Such natural LAB microorganisms are distributed world-wide, but their identification and growth on the taro substrate needs to be investigated.