X-Message-Number: 21732
From: "Igor Artyuhov" <>
References: <>

Subject: Pressurized and frozen  food for thought (Re: CryoNet #17788, a bit 
late ... :)
Date: Sat, 10 May 2003 01:53:07 +0400

Both articles [1, 2]* mentioned by Ben Best in CryoNet #17788
seem to me of great interest for cryonicists.

In fact, the method, now known as High-Pressure Shift Freezing
was (AFAIK) first applied experimentally as long ago as 1967 by
Maxim Persidsky in an attempt to preserve a canine kidney [3,
4]. The kidneys exhibited less signs of tissue deterioration
then kidneys, frozen by any other method, but still were not
viable. I don't know about any subsequent attempts in this

Later the method was re-invented under the name HPSF in order to
achieve high-quality preservation of food. Today the area is
under a rather extensive exploration; the outcome is mainly
presented in "Journal of Food Sciences" and "Food Technology"
(see list of references in [1]).

The main idea of the method comes from the fact that, applying
sufficient pressure to water we can reduce its melting
temperature (Tm). At a pressure of 210 MPa (~2100 atm) Tm
is -22C; further increase in pressure results in the rise of
Tm. It was two or three times mentioned in the CryoNet
messages (## 5077 et al.)

It is hardly practical to store either food or human bodies at
2100 atm; as well, -22C is far from the temperatures of interest
for cryonicists. But the good news is that when pressure
released - and that can be done very quickly - we get the water
in the sample being supercooled to -22C at atmospheric pressure.

In the absence of cryoprotectors and ice-blockers it will soon -
in a few seconds - change into ice. But the crystals will be

1. Very small
2. Granular shaped (vs. needle-shaped, when cooled from the
3. Uniformly distributed all through the sample.

So, the damage from ice crystals will be much less than in case
of surface cooling.

Not all of the water will freeze. Since the freezing produces
much heat, the sample will warm to 0C when about 29% change into
ice [1]**. So, HPSF only is not sufficient for cryonics.

Several methods can be applied in order to handle remaining 71%
of water:

  Usage of cryoprotectants. In fact, application of pressure can
reduce the necessary concentration of cryoprotectant by 0.29,
for example from 27% to 19%.
  Cyclic freezing. Persidsky [3, 4] used combination of
cryoprotectant (15% DMSO) and several compression - cooling -
releasing cycles.
  Supercooling. The temperature of homogenous nucleation (the
ultimate temperature to which water can be supercooled) goes
down from -40C at atmospheric pressure to -90C at 2100 atm [5].
So, in theory, water can be cooled down to -90C without
crystallization. In this case the heat of phase transition will
not be enough to warm the water to 0C and it will all change to
ice immediately after the release of the pressure. Usage of
cryoprotectors and ice-blockers may help to achieve the
necessary degree of Supercooling.

Of cause, any combination of these methods is possible.

Another possibility is to use vitrification rather than
freezing. Under high pressure the viscosity of water greatly
increases, up to 1500 times at 2100 atm [5], thus greatly
reducing the nucleation rate. The high pressure method allows
specimens up to 0.2 mm thickness with a total volume of ~1 mm^3
to be vitrified without any cryoprotectants at cooling rate of
200C/sec (vs. 10000 C/sec at atmospheric pressure) [5]. And, as
in case of supercooling, cryoprotectors and ice-blockers may
High pressure can as well be used on the thawing stage to reduce
the recrystallization.

Bad news is that application of such pressures as 2000 atm leads
to denaturation of some proteins [6]. It is hard to say now
whether this kind of damage is inappropriate for cryonics
purposes - as compared to crystallization, osmotic shock,
cracking etc. It is possible, that more compression - cooling -
releasing cycles with say, 1000 or 500 atm pressure will do

Of course, 2100 atm chamber for whole body will be rather an
expensive piece of equipment. But, if they can afford it for
food processing, can't we afford it for processing ourselves?

* Both papers aren't available via Internet, but I can send
copies of them as PDF files on a request.
** In fact, one should consider the total thermal capacity of
the sample/body rather than just capacity of water. So it may
take much more than 29% of water to crystallize to warm all the
tissue to 0C.


1. L. Otero, P. D. Sanz, "High-pressure shift freezing. Part 1.
Amount of ice instantaneously formed in the process",
Biotechnology Progress,  16(6):1030-6, 2000 Nov-Dec.
2. P. D. Santz, L. Otero, "High-presssure shift freezing. Part
2. Modeling of freezing times for a finite cylindrical model",
Biotechnology Progress.  16(6):1037-43, 2000 Nov-Dec.
3. M. D. Persidsky, V. Richards, "Cryopreservation of Organs in
the Absence of Thermal Gradients", Cryobiology, March-April,
1967, pp. 375-376.
4. M. D. Persidsky  et al., "Dog Kidney Cryopreservation Under
Thermal Gradient-Free Conditions", Cryobiology, March-April,
1968, pp. 264-265.
5. "HPM 010 High Pressure Freezing Machine"

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