*2.4. Physiological ANS Measures*

*2.4. Physiological ANS Measures*

PPG heart rate was collected using a BIOPAC MP150 system and AcqKnowledge 5.0.4 data acquisition software (BIOPAC Systems Inc., Santa Barbara, CA, USA). Heart rate was measured using the TSD200 PPG transducer attached to the index finger of the non-dominant hand. The TSD200 transducer was also connected to the PPG/EDA transmitter. Data were stored on a desktop PC (sample rate 250 Hz). The PPG signal was

**Figure 1.** The EmojiGrid used in the study to measure valence and arousal [25].

PPG heart rate was collected using a BIOPAC MP150 system and AcqKnowledge 5.0.4 data acquisition software (BIOPAC Systems Inc., Santa Barbara, CA, USA). Heart rate was measured using the TSD200 PPG transducer attached to the index finger of the non-dominant hand. The TSD200 transducer was also connected to the PPG/EDA transprocessed real-time in AcqKnowledge using the Pulse Rate calculation channel, resulting in the pulse/heart rate in beats-per-minute (bpm).

RPPG heart rate was recorded remotely based on photoplethysmography (RPPG), a technique that measures the small changes in color caused by changes in blood volume under the skin epidermis using a multi-wavelength RGB camera [31,32]. Pilot food studies in which RPPG heart rate was compared to the gold-standard ECG and PPG during chewing and not-chewing showed that RPPG heart rate was generally approximately 6 BPM lower than ECG and PPG heart rate, especially during chewing. Overall, the correspondence between RPPG and ECG/PPG heart rate was satisfactory [33].

Heart rate in combination with other physiological parameters have previously been related to food preferences and emotions (see [12]).
