Background Sweet and salty tastes can influence food intake {Sørensen, 2003 #40}. Increased intensity of these tastes has been shown to decrease food intake and increase satiation compared to the less intense taste, independent of palatability {Bolhuis, 2010 #245;Bolhuis, 2011 #251;Chung, 2007 #253;Lucas, 1987 #258;Vickers, 1998 #252;Vickers, 1998 #249;Vickers, 2001 #246;Yeomans, 1998 #244}. Umami taste intensity has been shown to reduce subsequent food intake {Masic, 2014 #7}, especially when paired with protein content in foods {Masic, 2014 #6}. Taste can be related with nutrient content of the diet, with sweet foods having carbohydrates, salty foods containing sodium, and umami foods containing protein {Teo, 2018 #37}.

However, no study has yet investigated the impact of umami and food intake, using the approach of similar palatability and differing taste intensity levels {Forde, 2016 #254}. Given its relationship with nutrient signaling, it is important to explore the relationship between umami intensity and satiation. Therefore, this study aims to compare ad libitum food intake of two levels with similar palatability and differing umami taste intensities (high and low) to food intake from a meal with optimum taste intensity.

Methods Test session 1 Determine individual's most preferred level of umami taste in 10 risotto samples, use Booth's method {Booth, 1983 #247}. Samples will contain a fixed level of salt, and MSG concentrations ranging from 0.2-1.2 w/w%, based on the optimal amount of MSG added to enhance taste to be 0.1-0.8 w/w% {Wijayasekara, 2017 #70}. Per individual, samples that are closest to those situated at -3.5 and +3.5 from the optimum (at 7) will be selected (figure 1).

Healthy, normal weight participants will be included. Previous studies have applied this method in sweet and salty tastes with 15-59 participants {Bolhuis, 2010 #245;Bolhuis, 2011 #251;Bolhuis, 2012 #255;Vickers, 1998 #252;Vickers, 1998 #249;Vickers, 2001 #246}.

Test session 2, 3 and

In a randomized cross-over design, participants will receive the optimum, high and low MSG risotto. The following will be measured:

• Test meal consumption (primary outcome);
• Liking before meal;
• Liking after meal;
• Water consumption;
• Taste intensity ratings of the meal;
• Habitual dietary taste exposure (tasteFFQ).

Subjects will be asked to eat a similar breakfast and to not consume anything between breakfast and lunch session. They will also be asked to refrain from eating for one hour after the test session. Participants will be asked to fill in the tasteFFQ, to investigate the link between dietary taste patterns and hedonic umami taste ratings.

Data will be analyzed using Rstudio. First, normality will be assessed, and data will be normalized if needed. Difference in food intake in grams between the three intensities will be compared using ANOVA. A post-hoc test will be applied if statistical outcomes are significant. Categorical variables will be compared using Chi-square test.

Inclusion Criteria:

• Self-reported healthy;
• BMI between 18.5 and 25 kg/m2;
• Age between 18 and 55 years old;
• Able to visit the research facilities on the Wageningen campus for hedonic mapping (once) and for the risotto lunch meal (three times);
• Able to provide informed consent.

Exclusion Criteria:

• Diagnosed with smell- or taste disorder(s);
• Use of medication that could influence taste ability and/or food intake behaviour;
• Food allergy or intolerance to any of the ingredients used in the ad libitum test meal;
• Consumption of more than 14 (women) or 21 (men) glasses of alcohol per week;
• Student or personnel of the Health Research Unit at Wageningen University

Individual study participant data will be shared after anonymization upon study publication in an open data repository (e.g. DANS or Yoda).