Short communicationDesign and testing of foods differing in protein to energy ratios☆
Introduction
To test feedback effects of macronutrients on energy intake, it is important to disguise the macronutritional composition of foods. This can be done by minimising differences in sensory aspects and in pleasantness, sweetness and savouriness. Stubbs et al. (2001) successfully disguised the fat content of foods, producing covert manipulation in low fat and high fat foods. Overall participants were unable to detect differences with the exception of dairy-based foods. There have been no studies that have attempted a covert manipulation of the protein to energy ratio of foods, however, and that was the primary aim of the present study.
Experimental data indicates that protein is the most satiating macronutrient group for humans and may therefore protect against over-consumption (Barkeling et al., 1990, Rolls et al., 1988). To date, experiments testing the effect of the percentage of protein energy (E) in the diet on total E intake suggest that protein feedback may exert an influence on total E intake over a matter of 1–2 days. Such studies have not however controlled for sensory differences between foods and effects of prior exposure (Simpson et al., 2003, Simpson and Raubenheimer, 2005, Weigle et al., 2005). To test whether feedbacks associated with protein act in the absence of such cues, it is necessary to first test whether the protein to energy ratios of a variety of sweet and savoury test foods can be concealed. This study presents the design and palatability testing of such foods, in two culturally diverse settings—in Sydney, Australia and Kingston, Jamaica.
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Subjects
Approval for the study was obtained from the Sydney South West Area Health Service Ethics Review Committee and The University of West Indies, Mona, Ethics Committee. Males and females aged 18–65 were recruited using the casual employment website at the University of Sydney and via email to School of Biological Sciences. Participants were not paid. Ten male (BMI: 23 ± 0.5 kg/m2 (mean ± sem)) and six female (BMI: 21 ± 1.0 kg/m2) participants were included in the first taste test trials in Sydney,
Effect of the protein to energy manipulation on pleasantness, sweetness and savouriness
Each version (i.e. 10, 15 and 25%) of each food was tested for pleasantness, sweetness and savouriness in Sydney and in Kingston (Appendix A: Supplementary Figs. 1 and 2). Overall there was no main effect of percent protein level on pleasantness ratings of test foods in Sydney (10%: 44 ± 2, 15%: 49 ± 2 and 25%: 49 ± 2, F(2, 28) = 3.307, p = 0.1 (ɛ = 0.703) or in Kingston (10%: 41 ± 3, 15%: 41 ± 3 and 25%: 37 ± 3, F(2, 12) = 2.802, p = 0.1, Greenhouse-Geiser (G–G) corrected: ɛ = 0.604). There were, however, differences
Discussion
This study has described the successful design and testing of near equally palatable versions of sweet and savoury foods with protein contents of 10, 15 and 25% with respect to total energy.
Although considered to be closely similar in pleasantness (the main aim of the study), the 10%, 15% and 25% versions of each food could be distinguished by the subjects when presented side by side. Simultaneous presentation of foods was used to directly test changing the percent protein of foods. After
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We would like to acknowledge Gerry Quinn of Deakin University for his adivce on statistical analysis. This project was funded by a National Health and Medical Research Council of Australia project grant. There is no conflict of interest.
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The recipe can be obtained by contacting the corresponding author.