Optimisation of Hot Water Extraction and Thermal Degradation Kinetics of Stink Bean Pod Extract

Tham, Xuan Yun (2026) Optimisation of Hot Water Extraction and Thermal Degradation Kinetics of Stink Bean Pod Extract. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Stink bean (Parkia speciosa) is well known for its nutrient-rich profile, yet its pods are often discarded despite being a potential source of bioactive compounds. However, research on efficient hot water extraction and the thermal stability of bioactive compounds from stink bean pod extract remains limited. This study aims to optimise the hot water extraction conditions for bioactive compounds from stink bean pods using response surface methodology, and to evaluate the thermal degradation kinetics of the optimised extract. A face-centred central composite design was performed to investigate the effect of extraction temperature (40-60 °C) and extraction time (30-90 min) on colour, pH, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities (DPPH, ABTS, FRAP) of stink bean pod extract, while the optimum conditions were identified. The thermal stability of the extract was evaluated under three selected heating temperatures (65, 80, and 95 °C) and times (20, 40, and 60 min), and degradation behaviour was modelled using zero-, first-, and second-order kinetics model. Results showed that both extraction temperature and time significantly (p < 0.05) affected the color, while TPC, TFC, DPPH, ABTS, and FRAP were significantly (p < 0.05) influenced only by extraction temperature. The optimum condition was achieved at 60 °C of extraction temperature and 30 min of extraction time, with a composite desirability of 0.9518, yielding 82.45 ± 0.05 mg GAE/g dry solid of TPC, 71.18 ± 0.30 mg QE/g dry solid of TFC, 152.55 ± 0.73 mg AAE/g dry solid of DPPH, 235.08 ± 0.93 mg TE/g dry solid of ABTS and 512.31 ± 1.91 mg FeSO4E/g dry solid of FRAP. Kinetic analysis revealed that both heating temperature and time significantly (p < 0.05) affected colour, TPC, TFC, DPPH, ABTS, FRAP of optimised stink bean pod extract with the first-order kinetics model best described the thermal degradation of its quality properties (R2 > 0.9601). The reaction rate constant (k) was the highest and the half-life (t1/2) was the lowest at 95 °C. This study provides insight into hot water extraction as an ideal method for recovering phenolics, flavonoids and antioxidants from stink bean pods, demonstrating its strong potential for food applications