Physicochemical Variation and In-Vitro Bioaccessibility of Chloroplast-Rich Fraction (CRF) from Sweet Potato (Ipomoea Batatas L.) Haulm

Agricultural waste has become a concern nowadays due to the remarkable quantity produced per year. Sweet potato (Ipomoea batatas L.) is the second largest cash crop in Malaysia. It is harvested after three months of growing, leaving the rest of the plant parts (stems, leaves, and petioles) which are collectively called “haulm”, behind on the field. Sweet potato haulm (SPH) is a potential source of chloroplast that contains highly lipophilic nutrients, namely β-carotene and lutein. This project aimed to establish data on the chloroplast-rich fractions (CRFs) from SPH by, i) investigating the effect of different crop borders (CBs) on the physicochemical variation of CRF, ii) investigating the effect of heat treatments (conventional pasteurisation [CP], steam pasteurisation [SP], and water blanching [WB]) on the physicochemical variation of CRF, and iii) investigating the digestive stability and bioaccessibility of β-carotene and lutein of CRF. The haulm harvested from three CBs (CB 1, CB 2, and CB 3) had variations in proximate compositions, total chlorophyll content and antioxidant activity (DPPH and FRAP assays). CB 2 exhibited the highest chlorophyll content (7.65 mg/g dw) and antioxidant activity (86.57 μg/ml [IC50] and 155.67 mmol Fe [II]/g dw). All CBs showed low antinutrients, ranging from 1.89 to 2.40 g/100 g dw (oxalic acid) and from 55.62 to 71.70 mg/100 g dw (phytic acid). This research found that all heat-treated CRFs had a reduced chlorophyll, total phenolic (TPC), and oxalic acid content, and enhanced solubility (p < 0.05). Heat-treated samples retained TPC (24 – 50 %) and FRAP (36 – 84 %), while increasing the DPPH (20 – 30 %). Most importantly, CP heat treatment was best compared to SP and WB in preserving TPC and antioxidant activity. Lastly, this research found that heat treatments (SP and WB) and the inclusion of oil can improve nutrients' bioaccessibility (BA) and accessible for uptake (NA). SP had the highest BA for β-carotene (17.30 %) and lutein (29.23 %) while WB had the highest NA for β-carotene (12.47 %) and lutein (23.74 %). Oil inclusion further increased the BA of β-carotene (at least 2 to 4 folds) and lutein (at least 1 to 2 folds). This study offers a sustainable source of essential nutrients from agricultural waste, potentially benefiting in new ingredient innovations for human or animal consumption while by-products from the waste may be invented for food and non-food applications.