2.3.2. Combined high pressure–temperature treatment
The double packed sample pouches were treated in a batch mode
high-pressure vessel (model: S-IL-100-250-09-W; maker: Stansted
Fluid Power, UK). The pressurization was accomplished by compressing
30% mono-propylene glycol which served as the transmitting medium.
The pressurizing rate was fixed at 300 MPa·min−1 and a rapid decompression
was achieved (b10 s). The maximum target pressure
(600 MPa) was reached within 133 s after the cycle starts; whereas
for 200 MPa, the corresponding figure was 45 s. The target temperature
near the sample was maintained by the circulating fluid in the jacket
surrounding the vessel. The hysteresis set for pressure and temperature
was 5 MPa and 1 °C, respectively. After the treatment, a refrigerated
condition (2–4 °C) was ensured for the samples prior to biochemical
analysis.
2.3.3. Measurement of pH, total soluble solid and titrable acidity
The pH, total soluble solid (TSS) and titrable acidity (TA) of the sample
were measured according to the methods described in Ranganna
(2007). A digital pH meter (model: CL 46+; maker: Toshcon, India)
and a digital refractometer (model: PAL-1; maker: Atago, Japan) were
used to measure the pH and TSS of the samples, respectively. Acidity
of the puree sample was determined by titrating the sample against a
standard alkali (sodium hydroxide solution) and quantified as g citric