Relative Effects of Sensory Modalities and Importance of Fatty Acid Sensitivity on Fat Perception in a Real Food Model

Abstract

Introduction: Fat can be perceived through mouthfeel, odour and taste, but the influence of these modalities on fat perception remains undefined. Fatty acids are stimuli and individual sensitivity to fatty acids varies. Studies show association between fatty acid sensitivity, dietary intake and BMI, but results are conflicting. Therefore, this study examined this association, and the effect of modalities on fat perception.

Methods: Two sub-studies were conducted. In study 1 (n = 46), fat intensity was assessed by milk/cream mixtures varying by five fat levels. Fat intensity was rated under four conditions: mouthfeel odour-masked, mouthfeel-masked, odour masked and with no masking. Mouthfeel masking was achieved using thickener and paraffin, odour masking using nose-clips. Fatty acid sensitivity was measured by 3-AFC staircase method using milk containing oleic acid (0.31-31.4 mM). In study 2 (n = 51), more fat levels were added into the intensity rating. A 2-AFC discrimination test was used to confirm whether fat levels could be distinguished. In the sensitivity test, a wider range of oleic acid was included.

Results: Fat intensity was rated higher without nose clips (p < 0.0001), implying that odour increased fat perception. Mouthfeel-masked samples were rated higher, showing that increased viscosity and lubricity enhanced fat perception (p < 0.0001). Participants could distinguish fat levels based on "taste" in rating tests and 2-AFC tests. Participants were divided into high-/medium-/low-sensitivity groups. No significant difference was found in fat intensity between groups; however, the high-sensitivity group discriminated more fat levels. No association between sensitivity groups, nutrient intake or BMI was found.

Conclusion: Mouthfeel and odour can enhance fat perception. Fat level can be discriminated based on taste.

Keywords: Detection threshold; Fat intake; Fat perception; Fatty acid sensitivity; Taste.

Fig. 1

The procedure of fat intensity rating and the rationale for each set of samples. MM mouthfeel-masked, MNM mouthfeel-non-masked, NC nose clip

Fig. 2

The procedure of sample presentation to determine an individual’s detection threshold, which is modified from the rapid ascending 3-AFC method developed by Allen et al. (2014). This figure here is an example based on the result of one participant. The percentage (%) correct if guessing was calculated based on binomial expansion. The participant’s actual percentage (%) correct was calculated as the ratio of the number of correct answers to the total number of sample sets presented to the participant at the corresponding fatty acid level (Formulas are shown in Supplementary Online Resource 2)

Fig. 3

The procedure of fat intensity rating in study 2 and the rationale behind each set of samples; MM mouthfeel-masked, MNM mouthfeel-non-masked, NC nose clip

Fig. 4

Perceived fat intensity under different modalities. Bars not sharing a common letter differ significantly (p < 0.05) between fat levels in one modality condition

Fig. 5

Oleic acid detection thresholds in milk of 46 participants in study 1

Fig. 6

Perceived fat intensity under different sensory modalities for the high fatty acid sensitivity group. Bars not sharing a common letter differ significantly (p < 0.05) between fat levels within each modality condition

Fig. 7

Perceived fat intensity under different modalities. Bars not sharing a common letter differ significantly (p < 0.05) between fat levels within one modality condition

Fig. 8

Oleic acid detection thresholds of 51 participants in Study 2

Fig. 9

Perceived fat intensity under “Taste” modality (a) and under “Overall” modality (b) for three sensitivity groups. Bars not sharing a common letter differ significantly (p < 0.05) between fat levels within one sensitivity group