METHODS: 5'-phosphodiesterase (5'-PDE) enzyme was characterized from adzuki beans, in which the optimum pH and temperature were determined. In addition, the stability of 5'-PDE was assessed at different pH and temperature. The effects of cations and EDTA were evaluated to characterize the 5'-PDE enzymes further.
RESULTS: The alkaline 5'-phosphodiesterase has an optimum pH of 8.5. This enzyme is also thermostable, with an optimum temperature of 80°C. The stability in terms of temperature and pH was also determined, and was found to be stable in the pH range of 7.0-8.5. This enzyme was found to retain more than 80% of its activity for 4 days at 60 and 65°C. In addition, the effects of 14 different metal ions, 4 types of detergents and ethylenediaminetetraacetic acid (EDTA) on 5'-PDE were studied. Ca2+, K+, Mg2+ and Li+ activated 5'-PDE while Na+, Zn2+, Ni+, Hg+, Cu2+, Pb2+, Fe2+, Al3+, Ba2+ and Co2+ were inhibitory. EDTA, Triton X-100 and sodium dodecyl sulfate (SDS) were strong inhibitors of 5'-PDE, while Tween 80 and Tween 20 were slightly inhibitory. The effects of cations and EDTA suggest that 5'-PDE from adzuki beans is a metalloenzyme.
CONCLUSIONS: Although 5'-PDE from adzuki beans has a high temperature optimum of 80°C, the enzyme is more stable at 60°C, and different cations affected the activity of the enzyme differently.
METHODS: The blends were prepared in a volume ratio of 10:90, 20:80, 40:60, and 60:40 (RBO:SO). The changes in the oxidative parameters and fatty acid composition of the samples during heating at frying temperature (170°C) were determined using analytical and instrumental methods. Oxidative alteration was also monitored by recording FTIR spectra of oil samples.
RESULTS: The increase in oxidative parameters (free fatty acid, color, specific extinctions, peroxide value, p-anisidine value, and thiobarbituric acid value) was greater in pure SO as compared to RBO or blend oils during heating. This indicates that the SO samples incorporated with RBO have the least degradation, while pure SO has the highest. Blending resulted in a lower level of polyunsaturated fatty acids (PUFA) with a higher level of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA). During heating, the relative content of PUFA decreased and that of SFA increased. However, the presence of RBO in SO slowed down the oxidative deterioration of PUFA. In FTIR, the peak intensities in SO were markedly changed in comparison with blend oils during heating. The reduction in the formation of oxidative products in SO during thermal treatment increased as the concentration of the RBO in SO increased; however, the levels of the protective effect of RBO did not increase steadily with an increase in its concentration.
CONCLUSIONS: During thermal treatment, the generation of hydroperoxides, their degradation and formation of secondary oxidative products as evaluated by oxidative indices, fatty acids and IR absorbances were lower in blend oils compared to pure SO. In conclusion, RBO can significantly retard the process of lipid peroxidation in SO during heating at frying temperature.
METHODS: The parameters of spray-dried 'cempedak' fruit powder under study include inlet air temperature (140-180°C) and maltodextrin (DE 10) concentrations (5-15% w/w). Response surface methodology involving 14 runs was used to assess the effects of inlet temperature and maltodextrin on the powder flow properties and reconstitution properties of the spray-dried 'cempedak' powder.
RESULTS: Out of the tested responses, only bulk density, change in cake height ratio, and water solubility index had a high coefficient of determination value. Inlet air temperature was found to be the main parameter to affect the bulk density, caking and water solubility index, when compared to maltodextrin concentration. By setting minimization of caking and maximization of water solubility index as the main determinants, the optimal parameters of 160°C inlet temperature and 15% (w/w) maltodextrin DE10 were generated, with a desirability of 0.697.
CONCLUSIONS: The powder produced under optimal conditions (160°C and 15% w/w maltodextrin) had a low bulk density (480.01 kg/m3), low caking properties (0.17 change in cake height ratio), and a high solubility index (88.69). This indicates that the powder is stable to be stored (without caking) and will have good reconstitution when added to water.