Nutrient Content and Carotenoid Bioaccessibility of Underutilized Taro Varieties from Hawaii

Abstract

Taro (Colocasia esculenta), a starchy root crop, is widely consumed across Asia and the Pacific and exists as different colored varieties in Hawai‘i. Although nutritional information exists for taro, there is a lack of variety-specific compositional data. In this study, the nutrient content (proximate and mineral via ICP-OES), phytochemical content (carotenoid via HPLC-PDA, total phenolic via Folin-Ciocalteau assay, and total monomeric anthocyanin via pH differential method), and carotenoid bioaccessibility (digestibility and micellarization efficiency via three-stage simulated digestion) were compared for three non-commercial taro, Mana Ulu, Pi‘iali‘i, and immature Pi‘iali‘i (Keiki) with one commercial variety, Maui Lehua. Nutrient and phytochemical contents differed across each taro cultivar based on their raw and cooked forms (P< 0.05). Beta-carotene and lutein were the primary carotenoids across each cultivar, with Mana Ulu containing the highest carotenoid concentration. Beta-carotene exhibited digestive stability of 45.8% and a micellarization efficiency of 13.6% from Mana Ulu samples. Total phenolic content was 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 6.93 mg/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, 25.93 mg/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. These findings indicate unique nutritional and phytochemical profiles amongst underutilized taro varieties, which could be better leveraged to improve nutrition and health outcomes. Overall, expanding variety-specific compositional data is critical to ensure reliable database information to assess the nutritional adequacy of diets.