Among the concerns on the safety of consuming leafy vegetables which are usually eaten raw or minimally processed is presence of contaminants such as pesticide residues and microorganisms. This research studied the effect of ultrasonic treatment (40kHz frequency and 350W power output) for 1,7 and 15 minutes on residue level of a selected pesticide (diazinon), qualitative and quantitative changes in physical appearance and the microbial availability on water spinach (Ipomoea aquatica Forssk.). Diazinon residue level was quantified using QuEChERS extraction method followed by gas chromatography flame ionization detector (GC-FID) analysis. The changes in physical appearance were measured by image comparison, the total colour change and comparison of leaf firmness pre-treatment and post-treatment. Microbial availability was measured by total plate count (TPC). One sample was found to have traces of diazinon at 3.07 mg/kg, which exceeded the permitted maximum residual level (MRL) of 0.2 mg/kg according to Malaysia Food Regulations 1985, while no pesticide residue was detected on other samples treated with control and ultrasonic waves. Prolonging ultrasonic treatment beyond 7 minutes damaged water spinach leaves, thus affecting the physical appearance. Leaves treated with ultrasonic waves showed lower total colour change (ΔE) compared to control treatment. The firmness of water spinach leaves increases with increasing treatment duration with maximum increase obtained with 7 minutes’ ultrasonic treatment. Regardless of sonication time, ultrasonic treatment was found to be more efficient in reducing microbial availability on water spinach compared to soaking alone, with up to 1.82 log reduction after 15 minutes’ treatment. Ultrasonic treatment can be utilised as a decontamination method for water spinach and other leafy vegetables owing to its ability to remove pesticide residues and lowering microbial availability in 7 minutes’ sonication time while preserving the quality of water spinach.

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.