Functional and physicochemical properties of Durian seed flour blended with cassava starch

Abstract

Durian (Durio zibethinus Murr.) seed flour (DSF) has very soft gel with high syneresis. Blending it with cassava starch (CS) could deliver strongly advantageous effects. The objective of this work was to investigate the functional and physicochemical properties of blends of CS and DSF. Experimentally, commercial cassava starch CS (18.18 ± 0.11% amylose) was blended with DSF (containing 55.44 ± 4.93% gum and 14.62 ± 0.07% amylose) in various CS/DSF ratios: 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, 10/90, and 0/100 by dry weight. The key properties of those blends were investigated, namely swelling power (SP), solubility, pasting properties by the Rapid Visco Analyzer (RVA), gelatinization temperature, and gel texture and syneresis. CS showed lower SP at 60 °C, but higher SP at 75 and 90 °C than DSF, while DSF had higher solubility than CS at all temperatures tested. The blends had SP and solubility between these extremes. RVA viscosities for all ratios of the CS/DSF blends were often below those of the individual components, with DSF influencing more than expected from its proportion. The peak viscosity (PV) of CS was significantly higher than that of DSF (3955 ± 37 vs. 1918 ± 17 mPa.s). The PV of CS/DSF blends with 10/90–60/40 ratios was slightly different from that of DSF, but increased strongly for the 70/30- 90/10 ratios. As regards gelatinization, CS had lower temperature range (62.66 ± 0.13–72.06 ± 0.21 °C,) than DSF (67.50 ± 0.55–79.35 ± 0.16 °C), while its enthalpy was higher (12.83 ± 0.81 vs. 5.38 ± 0.16 J/g). All the blends showed higher gelatinization temperature than CS but lower than DSF and their enthalpies had the opposite trend. Regarding the gel properties, gel hardness of CS was about five-fold higher than that of DSF (50.9 ± 30.27 vs. 9.59 ± 0.67, p < 0.05), while syneresis of CS was much lower (1.61 ± 0.33 vs. 58.30 ± 0.44%, p < 0.05) than of DSF. For their blends, it turned out that gel hardness increased and syneresis decreased with CS content in the blend. The gel hardness was synergistic for 90/10 and 80/20 ratios with about 50% increase over the pure components, and simultaneously the syneresis relative to plain DSF was reduced by over 50%. The results suggested that improved DSF properties can be achieved by blending with CS, and also a small amount of DSF (10–20%) has synergistic effect on gel hardness of the blend. Gum in the DSF plays an important role in the continuous phase of the paste and the gel.