Metodologia dos limiares hedônicos variando mais de um estímulo: estudo sobre delineamentos experimentais

Abstract

The hedonic thresholds methodology (HTM) allows for determining the beginning of the significant reduction in acceptance (CAT – compromised acceptance threshold) and the beginning of sensory rejection (HRT – hedonic rejection threshold) of foods. The HTM can be used by varying more than one stimulus, however, it is necessary to use a treatment design. Among them are mixture design (MD), central composite rotational design (CCRD), and face-centered composite design (FCCD). The objective was to investigate the impact of these designs on hedonic threshold values when varying multiple stimuli, in different foods. Furthermore, it was sought to investigate which design allows obtaining more reliable (precise and exact) results. Three experiments were carried out, in the first experiment, the use of CCRD was investigated in determining hedonic thresholds for the reduction of NaCl and the addition of KCl and MgCl2 to sliced bread. In the second experiment, the use of CCRD and FCCD was evaluated in determining directional hedonic thresholds for sucrose reduction and addition of cocoa powder (CP) in chocolate cake. Finally, in the third experiment, the impact of MD, CCRD, and FCCD on the values of hedonic thresholds and the accuracy of the results was investigated, in addition to investigating the reproducibility of the more accurate design. In this last experiment, the hedonic thresholds were calculated for reduction of NaCl and addition of KCl and MgCl2 to sliced bread. In the first experiment, when adding 0.8091% of KCl and 0.7697% of MgCl2, the sensorial acceptance of the bread becomes compromised only when there is a reduction of 38.58% of NaCl (CAT). When adding 0.6864% of KCl and 0.5504% of MgCl2, the hedonic rejection begins to occur only when there is a 97.48% reduction of NaCl (HRT). Both thresholds proved to be accurate. In the second experiment, it was found that, in general, the use of two different designs (CCRD and FCCD) did not change the CAT and HRT values by varying two stimuli (sucrose and cocoa powder contents), regardless of the sensory attribute investigated (aroma, texture, flavor and overall impression). The thresholds of both designs proved to be accurate. Through the third experiment, it was found that the designs changed the values of the hedonic thresholds. The CATi calculated using the MD was 0.5512% NaCl, 1.1487% KCl, and 0.0002% MgCl2; using the CCRD was 1.0441% NaCl, 0.8091% KCl, and 0.7697% MgCl2; and using the FCCD was 0.7975% of NaCl, without the addition of other salts. The HRTi calculated using the MD was 0.0774% NaCl, 1.6224% KCl, and 0.0004% MgCl2; using the CCRD was 0.0428% NaCl, 0.6864% KCl, and 0.5503% MgCl2; and using the FCCD was 0.0428% NaCl and 1.7% KCl, without adding MgCl2. However, it was found that all designs resulted in exact thresholds, proving that they all really represent regions where it begins to occur the reduction of acceptance (CAT) and the beginning of sensory rejection (HRT). The thresholds determined by the CCRD proved to be more accurate than those obtained with other designs. Furthermore, the results obtained with CCRD were reproducible. This information is of great use to the industry and science of food, in addition to expanding the application of HTM by varying more than one stimulus.