Swamp Taro Research Articles

Micronesian banana, taro, and other foods: newly recognized sources of provitamin A and other carotenoids

Vitamin A deficiency (VAD) and chronic diseases are serious problems in the Federated States of Micronesia and other Pacific island countries. Nutrition education programs to address these in Micronesia have had limited success, partly due to lack of information on nutrient content in local foods. The study objective was to identify local plant foods rich in provitamin A and other carotenoids that have high levels of cultural acceptability. Food cultivars likely to be carotenoid-rich (suggested by coloration) were identified using an ethnographic approach including key informant interviews. Raw and cooked samples (mostly cultivars previously not analyzed) of 12 banana, 13 giant swamp taro, 10 breadfruit cultivars and four other local foods were analyzed by high-performance liquid chromatography. Many banana and taro cultivars were found with significant levels of β- and α-carotene; the β-carotene levels ranged from 30 to 2780 μg/100 g (banana) and 50 to 2040 μg/100 g (taro). The results highlight the potential significance of cultivar differences in human nutrition, important for evaluation of the diet, establishment of locally relevant dietary guidelines, and research on the relationship between diet, health, and disease. These highly acceptable food cultivars could play an important role in VAD and chronic disease prevention programs in the Pacific.

Cyanide content of the leaves and stems of edible aroids

AbstractThe edible aroids taro (Colocasia esculenta), tannia (Xanthosoma violaceum), giant taro (Alocasia macrorrhizos), giant swamp taro (Cyrtosperma chamissonis) and elephant foot yam (Amorphophallus paeonifolius) have been shown to contain varying amounts of cyanide in their leaves and stems using a screening assay and a more accurate acid hydrolysis method. The cyanogenic glucoside triglochinin (previously identified in giant taro) was found to be less stable to acid hydrolysis (requiring only 15 min) compared with 50 min hydrolysis for linamarin and lotaustralian (from cassava) under the same experimental conditions. The amounts of cyanide present in the leaves (0‐3 mg HCN/100 g fresh weight) and in the stems (0—0.3 mg HCN/100 g fresh weight) of Colocasia and Xanthosoma are only about 1‐5% of that found in cassava leaves and tubers and are not a cause for concern for human nutrition. Cyrtosperma stems and Amorphophallus leaves contain only small amounts of cyanide. In contrast, all Alocasia varieties contained much more cyanide in leaves (2‐30 mg HCN/100 g fresh weight) and in stems (0.5‐4 mg HCN/100 g fresh weight).

Heat stability of trypsin inhibitors in tropical root crops and rice and its significance for nutrition

AbstractThe heat stability of trypsin inhibitors from rice (Oryza sativa L), sweet potato (Ipomoea batatas (L) Lam), taro (Colocasia esculenta var esculenta (L) Schott), giant taro (Alocasia macrorrhiza (L) G Don) and giant swamp taro (Cyrtosperma chamissonis (Schott) Merr) was studied. Rice trypsin inhibitor (TI) occurred only in the germ, so it is absent from white rice. Taro, giant taro and giant swamp taro (but not rice or sweet potato) showed an initial large increase (one‐ to tenfold) in the amount of TI present on heating at about 80°C. The heat release mechanism, which was accompanied by a change to a rubbery texture in the food, amounted to a breakdown of the cellular structure making TI available for extraction. Such heat release of TI would cause partially cooked food to be deleterious for human consumption. Brown rice, sweet potato, taro and giant swamp taro contained moderate amounts of TI, which was fully inactivated when the boiled or baked food was soft enough to eat. Giant taro, however, contained 10–100 times as much TI (which in this case also inhibited chymotrypsin) as the other foods, and a boiling time of at least 30 min was needed for its inactivation.

Trypsin inhibitors from Colocasia esculenta, Alocasia macrorrhiza and Cyrtosperma chamissonis

Trypsin inhibitors from three edible aroids of the family Araceae, viz. taro ( Colocasia esculenta) var. esculenta) giant taro ( Alocasia macrorrhiza) and giant swamp taro ( Cyrtosperma chamissonis) obtained from the Pacific region, were isolated by affinity chromatography and purified by gel filtration. The M r of these inhibitors, as determined by gel filtration were 35 000–38 000, but were ca 20 000 by SDS gradient PAGE. A time course of heating in SDS showed a ready dissociation of the native protein into subunits of equal size. Further experiments showed that there were no disulfide bonds between these subunits. A single N-terminal sequence was found for each inhibitor showing that the two subunits had similar primary structure. Each of the N-terminal sequences showed homology with that of soybean trypsin inhibitor. To our knowledge, this finding follows only one other example of a Kunitz family inhibitor being located in a monocotyledonous, rather than dicotyledonous, plant species, and indicates that the ancestral gene from which Kunitz family inhibitors originate predates the evolutionary divergence of flowering plants into monocotyledons and dicotyledons.

HPLC determination of vitamin A and vitamin D2 in South Pacific root crops

AbstractAn HPLC method was developed for the analysis of α‐carotene, β‐carotene, retinol and vitamin D2. Sweet potato Ipomoea batatas, taro Colocasia esculenta, taro Xanthosoma sagittifolium, giant taro Alocasia macrorrhiza, giant swamp taro Cyrtosperma chamissonis, yam Dioscorea alata and yam D esculenta contained no appreciable amounts of α‐carotene, retinol or vitamin D2 and the amounts of β‐carotene were equivalent to 0‐300 μg kg‐1 retinol in the fresh samples. This small amount, compared with the WHO/FAO adult RDA of 750 μg day‐1, and the virtual absence of vitamin A related eye diseases in the South Pacific region, demonstrates the adequacy of greens and fiuits, and fish coastal areas, in meeting the vitamin A requirement.

Thiamin, Riboflavin, and Nicotinic Acid Contents of Tropical Root Crops from the South Pacific

ABSTRACTThe thiamin, riboflavin, and nicotinic acid contents of sweet potato (Ipomea batatas, taro (Colocasia esculenta), giant taro (Alocasia macrorrhiza), giant swamp taro (Cyrtosperma chamissonis), taro (Xan‐thosoma spp), yam (Dioscorea alata and D. esculenta) were determined for fresh and 40°C dried material obtained from six South Pacific countries. Losses on drying at 40°C for 2‐3 days were 10‐15% for the three vitamins. Sweet potato contained the largest amount of thiamin (40‐120 μg/100g fresh weight) and along with Colocasia esculenta and Xanthosoma spp. the largest amounts of nicotinic acid. The root crops provided inadequate amounts of thiamin, riboflavin, and nicotinic acid with values ranging from 12‐123, 12‐59 and 220‐1310 Hg/100g fresh weight, respectively. Losses on cooking were about the same for all vitamins and root crops, with about a 20% loss on boiling (water retained) or baking and about a 40% loss on boiling (water discarded).

Ascorbic Acid and Dehydroascorbic Acid Content of Tropical Root Crops from the South Pacific

ABSTRACTThe total vitamin C content (ascorbic acid (AA) plus dehydroascorbic acid (DAA) was estimated by HPLC for sweet potato (Ipomoea batatas), taro (Colocasia esculenta), giant taro (Alocasia macrorrhiza), giant swamp taro (Cyrtosperma chamissonis), taro (Xanthosoma spp.), yam (Dioscorea alata), yam (D. esculenta), cassava (Manihot esculenta) and mean values were 23.6, 15.1, 16.9, 15.7, 13.6, 27.5, 20.3, and 14.9 mg/100g fresh weight, respectively. Standard titrimetric and colorimetric methods gave results only for AA which were generally comparable with HPLC. Drying at 40°C caused loss of AA which was not quantitatively converted into DAA. Storage of sweet potato at 25°C and 15°C for 28 days reduced the total vitamin C content by 17% and 15%, respectively; there was no significant decrease at 0°C. Cooking reduced the levels of AA and DAA by up to 70%.