*2.1. Participants*

Forty healthy participants (30 females and 10 males aged between 20 and 59 yrs. with an average age of 43 yrs.) were recruited from the consumer database of Food, Health, and Consumer Research (Wageningen Food and Biobased Research) after screening with an online survey (EyeQuestion Software, Logic8 B.V., The Netherlands). The database consists of 2945 persons (1015 males and 1930 females all living in or near Wageningen and aged between 19 and 95 yrs). Exclusion criteria were allergies or intolerance to wheat, gluten, soybean, or rice allergy. All participants provided written consent to participate in the experiment. In the recruitment questionnaire, participants were asked to indicate the frequency of their soy sauce use using an 8-point scale (more than three times a week, 1–2 times a week, once a month, once per 3–4 month, 1–2 times a year, less than once a year, never used, and I do not know if I use soy sauce) and daily use soy sauce brand. The participants were assigned to one of two groups depending on their frequencies of use. Twenty-two participants, 17 females and 5 males, who used soy sauce either never or maximum once per month were assigned to the low-frequency user group. Eighteen participants, 15 females and 3 males, who used soy sauce at least once per week were assigned to the high-frequency user group.

The participants received financial compensation of 10 euro after finalizing the study. The study was approved by the Social Ethical Committee of Wageningen University and Research.
