The processed food industry is renowned for combining sugar, salt and fat in almost all food categories.
But while it is relatively easy to determine the optimal level of sweet or saltiness, the role of fat on food palatability is more complex and difficult to assess.
Researchers from Deakin University in Australia therefore wanted to investigate fat’s role in determining the ‘pleasantness’ of both sweet and salty liquid foods - in this case, soup and custard.
They found that individuals generally preferred much higher concentrations of fat - 30% - in custard rather than soup.
“Interestingly, participants preferred the highest fat concentration custard despite 1) hardly perceiving differences in fat concentrations and 2) not being used to such high fat levels in those food products," they wrote. "The attraction to this high fat concentration remains unclear and needs further investigation.”
While fat and salt separately affected pleasantness in soup, in custard it was fat, sugar and the interaction between the two that affected pleasantness.
“The present study showed that salt and sugar levels are more important determinants of food liking than fat, and therefore considered as the major drivers of food intake. Reducing salt or sugar/sweetness is considered to be more challenging than reducing fat to maintain palatability in liquid foods. However, the role of fat is considered to be more important in appreciation of semi-solid and solid foods due to a higher impact on food texture.”
“There is no consistent effect of fat on perception or on liking across foods, therefore the attractiveness of fat in foods cannot be generalised."
The researchers gave 47 male and female participants with a BMI of between 18.5 and 25 creamy tomato soup and custard, which each contained four fat concentrations (fat-free, 7.5, 15 and 30%).
These variations were combined with four salt concentrations (0.04, 0.35, 0.7, and 1.5%) in the soup, and four sugar concentrations (0.56, 4.5, 9, and 18%) in the custard.
The foods were made with a combination of thickened cream and canola (rapeseed) oil and either salt or sucrose, and each individual tried both soup and custard in two different sessions.
In the non-fat samples, the researchers added acacia gum and liquid paraffin to mimic texture.
After tasting the samples, the individuals rated them for pleasantness, saltiness intensity, sweetness intensity and fattiness intensity and noted their preferred fat concentrations were determined by hedonic ranking.
Sweet, salty and oleo
Does fat have a taste?
According to the authors of the Australian study, the sensory characteristics of fat go beyond mere taste. “Fat affects our perception through somatosensory, taste, and odour pathways, which increases the complexity to study the role of fat on pleasantness,” they write.
However, in 2015, US-based researchers claimed to have demonstrated using perceptual mapping techniques that nonesterified fatty acids have a taste sensation that is distinct from other basic tastes, meaning that fat is the sixth basic taste.
"The taste component of fat is often described as bitter or sour because it is unpleasant, but new evidence reveals fatty acids evoke a unique sensation satisfying another element of the criteria for what constitutes a basic taste, just like sweet, sour, salty, bitter and umami,” said Professor Richard Mattes of Purdue University and lead author of the study.
However, the US scientists said that the fatty taste itself is not actually pleasant. "When concentrations of fatty acids are high in a food it is typically rejected, as would be the case when a food is rancid,” Mattes said.
Source: Food Quality and Preference
“Preference and perception of fat in salty and sweet foods”
Available online ahead of print, doi.org/10.1016/j.foodqual.2017.09.016
Authors: P. Bolhuis, Andrew Costanzo, Russell S.J. Keast