3.5. The free amino acid contents in UBM treated by the two-stage
MBCO2
The free amino acid contents in UBM treated by the two-stage
MBCO2 are shown in Table 1. The free amino acid contents except
for PEA and Val were decreased by only mixing vessel of the twostage
MBCO2. In addition, further decrease of Lys was induced by
increasing temperature with the heating coil. Our present result
disagreed with the reports by Cappelletti et al. (2015) and Guo et al.
(2011), where itwas mentioned that the free amino acid contents in
grape juice and coconut water increased and remained unchanged
after pressurized CO2 treatment. However, the two-stage MBCO2
was recognized to decrease the free amino acid contents in unpasteurized
sake and unfiltered beer (Kobayashi, et al., 2014;
Kobayashi & Odake, 2015). The reason for these changes in free
amino acid contents is considered to be the absorption of free
amino acids onto MBCO2, or the precipitation of free amino acids by
the lowering of the pH, although the reason is still unclear.