Rheological, Textural, and Sensorial Characterization of Walnut Butter

Abstract

The rheological properties of six formulated walnut semi-solid pastes with 0.5, 1.5, and 2.0% w/w xanthan gum, maple syrup, and Jerusalem artichoke powder were characterized using the Mars 40 rheometer (Thermo Haake, Karlsruhe, Germany). The butter samples’ textural behavior and color parameters (CIE L*, a*, and b*) were analyzed. Sensory evaluation and consumer acceptance were also analyzed. Walnut kernels were roasted at an optimized temperature (120 °C) and time (30 min) and subsequently made into walnut butter (WB). Maple syrup has an appreciable influence on the rheological properties of walnut butter. The prepared butter exhibited non-Newtonian shear thinning behavior and showed excellent stability. The results showed that sample S3 (3% maple syrup and 2% xanthan gum) had a bright color with the highest L* values (47.31 ± 0.32), the lowest a* values (2.72 ± 0.04) and the highest b* values (20.54 ± 0.08). In comparison, sample S6 (5% Jerusalem artichoke powder and 2.0% xanthan gum) had a darker color, with the following mean values obtained: 44.67 ± 0.05 for L*, 6.70 ± 0.09 for a* and 18.34 ± 0.07 for b*. The addition of maple syrup even in combination with xanthan gum (2%) S3 to the walnut butter led to a decrease in the viscosity of the butter samples. The hardness and firmness of the walnut butter samples were affected by the type of sweetener used; thus, the nut butter with xanthan gum and Jerusalem artichoke powder had significantly higher hardness values than the samples with added maple syrup. Therefore, based on consumer preferences, we obtained new formulations of walnut butter with a high sensory quality, suitable for those with allergies to peanut butter.