Using the Hilbert Transform to Evaluate the Effects of Functional Foods on Autonomic Nervous System Activity: A Comparison with the Fast Fourier Transform.

Evaluating the autonomic nervous system (ANS) via heart rate variability (HRV) to investigate the effects of food on human health has attracted attention. However, using a conventional HRV analysis via the fast Fourier transform (FFT), it is difficult to remove artifacts such as body movements and/or abnormal physiological responses (unexpected events) from the HRV analysis results. In this study, an analysis combining bandpass filters and the Hilbert transform was applied to HRV data on functional food intake to compare with FFT analysis. HRV data were obtained from six males by recording electrocardiograms on functional food, γ-aminobutyric acid, intake. HRV indices were calculated by both analysis. In the Hilbert analysis, all HRV indices were obtained for the same number of sampling points as the HRV data. The standard errors of all HRV indices tended to be smaller in the Hilbert analysis than in the FFT analysis. In conclusion, the Hilbert analysis was more suitable than FFT analysis for evaluating ANS via HRV on functional foods intake.

Research Note: Detection of Campylobacter spp. in chicken meat using culture methods and quantitative PCR with propidium monoazide.

Globally, Campylobacter spp. are prominent causative agents of food-borne gastroenteritis. These pathogens are commonly detected using conventional culture methods; however, culture methods are unable to detect viable but nonculturable (VBNC) bacteria. Currently, the detection rate of Campylobacter spp. on chicken meat does not correlate with the seasonal peak of human campylobacteriosis. We hypothesized that this may be due to the presence of undetectable VBNC Campylobacter spp. Therefore, we previously established a quantitative PCR assay using propidium monoazide (PMA-qPCR), which can detect viable Campylobacter cells. In this study, PMA-qPCR was conducted to detect viable Campylobacter spp. in chicken meat, and the detection rates of PMA-qPCR and the culture method throughout all 4 seasons were compared. A total of 105 chicken meat samples (whole legs, breast fillets, and livers) were screened for the presence of Campylobacter spp. using both PMA-qPCR and the conventional culture method. The detection rates of the 2 methods did not differ significantly; however, the positive and negative samples were not always consistent. Detection rates in March were significantly lower compared to months with the highest detection rates. These results suggest that, to increase the detection rate of Campylobacter spp., the 2 methods should be used in parallel. In this study, PMA-qPCR could not detect VBNC Campylobacter spp. effectively in C. jejuni-spiked chicken meat. Further studies using improved viability-qPCR should be performed to describe the impact of the VBNC state of Campylobacter spp. on the detection of this bacterium in chicken meat.