2.6.2. HHP and bioactive coating
Coated or uncoated green bean samples (2.0
102 to
2.2
102 kg each), inoculated with L. innocua, were sealed in
flexible pouches made of multilayer polymer/aluminum/polymer
film (Polyethylene–Aluminum–Polypropylene) under vacuum
before each test. A bench-top vacuum packaging unit, equipped
with a vacuum pump (25 m3/h) and a sealing bar of 0.50 m, was
used to pack the samples at a
final vacuum level of 97%.
The experiments were carried out in a High Pressure pilot
plant MINI Foodlab FPG5620 (Stansted Fluid Power Ltd., UK). The
apparatus, with an internal volume capacity of 0.5 L, was operated
with a mixture of ethanol and castor oil. Being the system
completely adiabatic, a temperature increase rate of 4 C/100 MPa
was recorded during operation. Experiments were carried out for
5 min at a pressure level comprised between 200 and 400 MPa at
25
1 C. The pressurization rate of the HHP unit was set at
10 MPa/s, with the come up times ranging between 20 and 40 s,
depending on pressure. The decompression rate was instead set at