Page 56 - FoodFocusThailand No.239 March 2026

SMART
SMART PRODUCTION PRODUCTION

HIGH-PRESSURE THERMAL

PROCESSING (HPTP) TECHNOLOGY:

A NEW FRONTIER IN HIGH-QUALITY

STERILIZED FOODS

High-Pressure Thermal Processing (HPTP), also known as Pressure-Assisted Thermal Sterilization (PATS), is
an emerging food processing technology that continues to evolve. It is not merely a combination of pressure and
conventional heat; rather, it applies thermodynamic principles to generate uniform internal heating throughout
the product, enabling effective microbial inactivation under controlled conditions. The technology has been
recognized by the U.S. Food and Drug Administration (FDA) as suitable for producing certain low-acid foods,
such as mashed potatoes, at commercial sterilization levels.

From HPP to HPTP: Consequently, process design for products such as coconut
Evolution of Modern Food Sterilization curries, meat sauces, or other high-fat formulations requires
In the global food market in 2025–2026, demand for products greater precision than that for fruit juices.
aligned with clean-label concepts and fresh-like attributes has A key advantage of HPTP is the rapid decrease in temperature
grown rapidly. The high-pressure processing (HPP) market is upon pressure release, which significantly reduces the duration
projected to reach USD 55 billion, positioning HPTP as a next- of high-temperature exposure. For low-acid foods (pH > 4.6), the
generation technological advancement capable of extending primary objective is to inactivate heat-resistant bacterial spores,
HPP toward sterilization-grade food safety. such as Clostridium botulinum, Geobacillus stearothermophilus,
A common misconception is that HPTP involves “boiling and Bacillus subtilis. Pressure alone cannot inactivate these
food under pressure.” In reality, its core principle lies in adiabatic spores; however, when combined with temperatures between
compression heating (ACH). When food is subjected to high 90–121°C, microbial inactivation increases dramatically. Several
pressure (approximately 600 MPa or 6,000 bar), mechanical studies report spore reductions exceeding 5–6 log cycles at
energy from compression is instantaneously converted into substantially shorter processing times than conventional thermal
thermal energy. This rapid, volumetric heating occurs uniformly sterilization.
throughout the product, independent of package size or shape.
Unlike conventional heating, which relies on heat conduction Mechanisms of Spore Inactivation under HPTP
from the surface to the core and often results in overprocessing, Spore inactivation under HPTP occurs through two primary
HPTP minimizes excessive thermal exposure. mechanisms:
The rate of temperature increase (dT) relative to pressure 1) Germination Induction: At pressures around 100–300
change (dP) depends on the thermodynamic properties of the MPa, spore receptors are activated, triggering germination. This
food system, as described by the following equation: process compromises the spores’ inherent heat resistance,
converting them into vegetative cells that can be rapidly
inactivated at temperatures of 90–105°C.
2) Physical Compromise: At high pressures combined with
elevated temperatures—such as pressures above 600 MPa and
temperatures exceeding 100°C—protein structures within spore
membranes are directly disrupted. This results in immediate loss
where α is the coefficient of thermal expansion, of cellular integrity without prior germination.
T is the absolute temperature,
ρ is the density, and Case Studies:
c is the specific heat capacity. Applications in Various Food Products
p
The value of dT/dP is not constant but varies according to Comparative studies in baby food purées demonstrate that HPTP
product composition and initial temperature. For water or foods at 600 MPa and 115°C can reduce G. stearothermophilus spores,
with more than 70% water content, the temperature typically which are more heat-resistant than C. botulinum, by more than 6
increases by 3–5°C per 100 MPa. In contrast, high-fat foods log units within short processing times. The D-value (time required
may experience temperature increases of 8–9°C per 100 MPa. for a 90% reduction) is significantly lower than that observed in
thermal treatment alone.
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