Effect of Inulin on Rheological Properties and Emulsion Stability of a Reduced‐Fat Salad Dressing
Sornchai Sinsuwan
Abstract
This study is aimed at investigating the potential use of inulin in a reduced‐fat salad dressing to improve its rheological properties, fat globule size distribution, and emulsion stability. The reduced‐fat salad dressing, which has 50% less fat compared to the full‐fat counterpart (control), was prepared with varying inulin concentrations (10, 12.5, 15, 17.5, and 20% w / w ). The full‐fat and reduced‐fat salad dressings exhibited a non‐Newtonian shear‐thinning behavior. Power law model was used to describe the rheological properties. Results showed that the flow behavior index ( n ) and consistency coefficient ( K ) were greatly affected by the concentration of inulin. A greater pseudoplasticity and apparent viscosity of the reduced‐fat samples were achieved with a higher concentration of inulin. Oscillatory tests showed that the storage modulus ( G ′ ) and loss modulus ( G ″ ) values increased with increasing inulin concentration. All samples displayed characteristics of a viscoelastic solid, as evidenced by a greater G ′ than G ″ . Regarding the size distribution of the oil droplets, the reduced‐fat salad dressing containing a higher inulin content was observed to have a larger droplet size. All reduced‐fat samples, similar to the full‐fat counterparts, exhibited stability with no cream separation over one month of storage at 4°C, as determined by visual observation. Additionally, the reduced‐fat salad dressings supplemented with 17.5 and 20% inulin exhibited stability against cream separation, comparable to the full‐fat counterpart ( p > 0.05), as measured by the thermal stress test (80°C for 30 min) with centrifugation. The sensory acceptance scores for reduced‐fat salad dressing with 15 and 17.5% inulin, ranging from approximately 6.28 to 7.63 on a 9‐point hedonic scale for all evaluated attributes (appearance, color, aroma, texture, taste, and overall acceptability), were not significantly different from those of the full‐fat counterpart ( p > 0.05). This study demonstrated that inulin may be a suitable ingredient in reduced‐fat salad dressings.