Nutritional and Phytochemical Content of Underutilized Taro Cultivars From Hawai‘i

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2021

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Taro (Colocasia esculenta) is a starchy root crop that is commonly found in most tropical climates around the world. In Hawai‘i, various taro cultivars exist, each with potentially unique nutritional and phytochemical profiles as a result of their pigmented coloration. However, not much is known about the nutrient and phytochemical properties of these cultivars. The primary purpose of this research is to identify the nutritional and phytochemical aspects in these underutilized taro cultivars from Hawai‘i. The nutrient (proximate and mineral), phytochemical (carotenoid, total phenolic, and total monomeric anthocyanin), and digestibility (bioavailability & bioaccessibility) content of two commercially underutilized taro, Mana Ulu & Pi‘iali‘i, were compared with a commercial variety, Maui Lehua. An immature (colloquially referred to as “Keiki”) Pi‘iali‘i corm was also utilized in this study and compared to the other three. Both raw and cooked forms, through steaming, were utilized in this experiment. Overall findings indicated variation in nutrient and phytochemical content across each taro cultivar. Notable distinctions include a higher carbohydrate content found in the Maui Lehua and Mana Ulu cultivars, 31.92% and 31.76% respectively, while Pi‘iali‘i and the Keiki exhibited a lower content of 16.34% and 15.68%, respectfully. Phytochemical identification determined beta-carotene and lutein as the primary carotenoid compounds across each cultivar. Loss of carotenoid content was observed in all cultivars during their transition from raw to cooked states. Following in vitro digestion, only beta-carotene was retained from the cooked Mana Ulu variety. Bioaccessibility testing indicated a digestive stability of 45.8% and a micellarization efficiency of 13.6% for beta-carotene. Values of total phenolic content reported 83.52, 76.04, 75.44, and 66.86 mg/100 g FW and total anthocyanin content of 10.02, 9.33, 7.32, and 6.93mg/100g FW for Maui Lehua, Mana Ulu, Pi‘iali‘i Keiki, and Pi‘iali‘i, respectively. Cooked taro had significant polyphenol losses with total phenolic contents of 20.55, 17.73, 22.61, 25.93mg/100g FW as well as total anthocyanin contents of 3.19, 2.16, 2.12, and 2.88 mg/100g FW for Maui Lehua, Mana Ulu, Pi‘iali‘i Keiki, and Pi‘iali‘i, respectively. This research can provide a significant insight into the utilization of nutrients in underutilized food crops that would otherwise be absent in conventional crop utilization. This can apply not only to taro cultivars in Hawai‘i but other food sources around the world that have different species varieties.

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Food science, Bioaccessibility, Carotenoids, Nutrition, Phytochemicals, Polyphenols, Taro

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83 pages

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