Azizah Osman’s research while affiliated with Universiti Putra Malaysia and other places

Dried chilies (Capsicum annuum Variety Kulai) were reconstituted using two different soaking techniques (cold water and boiled water soakings), crushing and stone-grinding into a fine puree and pasteurized with and without citric and acetic acids. The quality attributes of chili puree were evaluated regarding pH, moisture, Hunter surface color (L, a, b and hue angle and chroma), extractable color (ASTA units) and capsaicinoid content. Results showed that different soaking techniques had a pronounced effect on the pH, moisture content, Hunter surface color, extractable color, hue angle and chroma of the puree. However, chili puree prepared by boiled-water soaking had lower capsaicin and dihydrocapsaicin concentrations compared to cold water soaking. Pasteurization did not seem to give an effect on the Hunter surface color (L, a, and b) and pungency of the puree produced. Overall, the combined treatments of boiled water soaking and pasteurization in the presence of a mixture of 1 % acetic acid (AA) and 0.2% citric acid (CA) conferred the best puree quality.

The properties of commercially-graded B10 cultivar starfruit (Averrhoa carambola) namely length, diameter, mass, volume, the five colours values (L, a*, b*, C, h°), firmness, total soluble solids (TSS), titratable acidity (TA) and pH were measured. Coefficients of variation (CV), correlation and property tolerances were evaluated to develop a relationship between the non-destructively measurable external properties and the non-destructively immeasurable internal properties. The length, diameter, mass and hue were found to have low CV levels. Mass appears to have a very strong correlation with volume while hue has a strong correlation with firmness.

This study was carried out to evaluate the feasibility of using ultrasound combined with conventional thermal pretreatment to overcome the limitations of conventional thermal treatment prior to osmotic dehydration. Seedless guava cubes (20 × 20 × 20 mm) were dehydrated in sucrose solution (30% w/w) at 33°C for 180 min. Mass transfer during osmotic dehydration of seedless guava depended on the pretreatment (conventional blanching/thermosonication). The effect of thermosonication on mass transfer terms was more pronounced for the water loss comparatively to the solid gain. Applying thermosonication pretreatment before osmotic dehydration of seedless guava led to limit WL/SG ratio in comparison with conventional blanching treatment. Measuring the conductivity of the medium showed significant (p < 0.05) higher values for both methods of pretreatment than untreated samples. The results proved that combining of ultrasound with conventional thermal treatment offering a feasible methodology for satisfactorily enhancing the mass transfer rates during osmotic dehydration of seedless guava.

The rheological properties of soursop beverage emulsions as a function of main emulsion components, namely modified starch (5–12 % w/w), whey protein isolates (WPI) (0–2 % w/w), soursop flavor oil (5–15 % w/w), and deionized water (67.4–86.4 % w/w) were investigated using a four-component with constrained extreme vertices mixture design. The apparent viscosity, flow index, yield stress, viscoelastic behavior (G′ and G′′) and consistency coefficient were evaluated. In general, analysis of variance (ANOVA) showed high coefficients of determination values (R 2), ranging between 0.795 and 0.999 for the regression models, thus confirming a satisfactory adjustment of the polynomial regression models with the experimental data. Increase in both modified starch and oil phase concentration had increased the apparent viscosity of the emulsions. Contrary, higher concentrations of oil phase had negative effects on flow index and consistency coefficient, resulting in the changes of flow behavior. In addition, modified starch showed solid-like elastic properties at low concentration but behaved as liquid-like viscous as the concentration of modified starch increased. Oil phase concentration had a significant (p<0.05) effect on the viscous behavior of the emulsions. However, WPI had an insignificant (p>0.05) effect on neither the apparent viscosity nor the flow index at low concentrations but was an important element in providing elastic properties to the emulsion film.

This study was conducted to investigate the effect of main emulsion components namely, modified starch, propylene glycol alginate (PGA), sucrose laurate and sucrose stearate on creaming index, cloudiness, average droplet size and conductivity of soursop beverage emulsions. Generally, the use of different emulsifiers or a mixture of emulsifiers has a significant (p < 0.05) effect on the response variables studied. The addition of PGA had a significant (p < 0.05) effect on the creaming index at 55 °C, while PGA-stabilized (PGA1) emulsions showed low creaming stability at both 25 °C and 55 °C. Conversely, the utilization of PGA either as a mixture or sole emulsifier, showed significantly (p < 0.05) higher cloudiness, as larger average droplet size will affect the refractive index of the oil and aqueous phases. Additionally, the cloudiness was directly proportional to the mean droplet size of the dispersed phase. The inclusion of PGA into the formulation could have disrupted the properties of the interfacial film, thus resulting in larger droplet size. While unadsorbed ionized PGA could have contributed to higher conductivity of emulsions prepared at low pH. Generally, emulsions prepared using sucrose monoesters or as a mixture with modified starch emulsions have significantly (p < 0.05) lower creaming index and conductivity values, but higher cloudiness and average droplet size.

In this study, osmotic dehydration of seedless guava was studied through response surface methodology. Seedless guava cubes were dehydrated in sucrose solution at different concentration (30-50% w/w), temperature (30-50 degrees C) and immersion time (15-240 min) with respect to weight reduction, solid gain and water loss. A Box-Behnken design was used to determine the optimum processing conditions that yieldmaximum weight reduction, water loss and minimum solid gain. The models developed for all responses were significant (p < 0.05). The response surface plots were constructed to show the interaction of process variables. Optimum process conditions were found to be sucrose concentration of 33.79% w/w, temperature of 30.00 degrees C and immersion time of 240 min through desirability function method. At these optimum points, weight reduction, solid gain and water loss were found to be 0.189 (gg(-1)), 0.050 (gg(-1)) and 0.237 (gg(-1)), respectively.

The change in backscattering parameters during the appearance of chilling injury in bananas was investigated. Bananas were stored at a chilling temperature for two days and the degrees of the chilling injuries that appeared were measured before, during and after storage using backscattering imaging and visual assessment. Laser lights at 660 nm and 785 nm wavelengths were shot consecutively onto the samples in a dark room and a camera was used to capture the backscattered lights that appeared on the samples. The captured images were analysed and the changes of intensity against pixel count were plotted into graphs. The plotted graph provides useful information of backscattering parameters such as inflection point (IP), slope after inflection point (SA), and full width at half maximum (FWHM) and saturation radius (RSAT). Results of statistical analysis indicated that there were significant changes of these backscattering parameters as chilling injury developed.