2. FRM GaleSens, Cergy, France
*Corresponding author
Introduction
Among the critical sensory attributes of solid foaming products, foam remains a pivotal factor. It is often linked to perceptions of cleanliness and efficacy, despite this association being more psychological than scientifically substantiated. Additionally, foam contributes significantly to user satisfaction; a creamy and dense lather enriches the overall sensory experience. The product must also feel pleasant in hand and spread easily through hair (6).
Around 20 solid products available on the European market were selected. Among these:
- 30% used a Sodium Coco Sulfate (SCS) base
- 20% used a Sodium Cocoyl Isethionate (SCI) base
- 20% used a SCI + decyl glucoside (APG) base
- 30% used other surfactants, alone or in combination
These shampoos exhibited wide diversity in visual appearance, ranging in color and gloss, as well as in texture, with noticeable variations in roughness and hardness. This variability highlights the broad formulation spectrum.
Sensory descriptors relevant to foam performance
To define the appropriate descriptors, the team based their approach on consumer gestures when using solid shampoos, which typically involved holding the bar between the hands to create foam before applying it to the hair.
Hand gesture
The foam evaluation on hands begins by activating the solid shampoo previously dipped in hot water through 10 rotations between wet hands. This method ensures consistent foam generation for sensory assessment. The following key attributes are then rated to characterize the foam quality:
- Hand coverage: How uniformly the foam creates a white layer over the hands; a more uniform white effect corresponds to a higher rating.
- Bubble size: Larger bubbles receive higher scores, reflecting specific sensory preferences.
- Foam homogeneity: The uniformity in bubble size throughout the foam; greater uniformity indicates better foam quality. (Figure 1-1)
Strand gesture
Table 1 below presents the key sensory foam attributes of solid shampoos along with their definitions and standardized protocols for evaluation on hair strands.
- Product A: SCS-based
- Product B: SCI-based
- Product C: SCI + decyl glucoside (liquid APG)
- Product D: SCI + solid decyl glucoside (powdered APG)
The results are presented in Figure 2. The developed protocol enables to observe clear differences between the products across all descriptors, except for the cushion effect, which remains a challenging attribute to evaluate. The product A based on SCS and shea butter showed the lowest performance in terms of foam quality. In contrast, the solid APG-based product D, despite being a first, non-optimized formulation, already produced a homogeneous foam
