Effect of Konjac Gum as a Fat Replacer on Rheological and Sensory Properties of Low Fat Mayonnaise

Considering the increasing consumption of fat-rich foods over the last decades and its relationship with prevalence of cardiovascular diseases, development of low-fat food formulations is of special importance. Hydrocolloids such as gums have great potential for imitating the role of fat in foodstuff. The aim of the present study was to explore the capability of konjac gum to replace the fat in mayonnaise.

Different concentrations of konjac gum (0.25, 0.5, 0.75 and 1%) were incorporated into the formulation of mayonnaise with 20, 30, 40 and 50% oil reductions, respectively. The static (flow behavior) and dynamic (strain sweep and frequency sweep) rheological properties were measured using a rheometer and sensory chracteristics were evaluated by a 10-member sensory panel. The rheological and sensory properties of low-fat mayonnaise containing different concentrations of konjac gum were compared with each other and low-fat control (30% fat) using a completely randomized design at 95% confidence interval.

The results of fitting the rheological data to Power-Law and Herschel-Bulkley models showed that all samples had pseudoplastic behavior. The low-fat samples containing different concentrations of konjac gum had lower flow index and higher consistency index than the control sample. Similarly, the yield stress was enhanced with gum concentration up to 0.5% but decreased after that. The finding of oscillating frequency sweep test showed that all samples had storage modulus larger than loss modulus and loss tangent lower than 1, confirming the viscoelastic characteristics of the samples. Furthermore, the loss tangent steadily decreased with increase in konjac concentration. It was observed that konjac gum had a significantly improving impact on stability index of reduced-fat mayonnaise in a concentration-dependent manner. The results of sensory analysis revealed that konjac gum significantly improved the texture, viscosity and overall acceptability but did not have any significant effect on odor and flavor of low-fat mayonnaise.

It is concluded that the low-fat mayonnaise sample containing 0.5% konjac gum was the best formulation in terms of rheological and sensory properties.