food product development company

New Technologies Report - #04
Date: 4th November , 2022
ISOCHORIC FREEZING
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INTRODUCTION
• Freezing is a food preservation technique that involves decreasing the temperature to stop bacterial growth. The technique
of freezing food by submerging it in an ice and salt brine has been followed for millennia in cold climates, and a patent for it
was granted in Britain as early as 1842.
• Over the years, several freezing technologies have been evaluated for preserving food and other biological matters. Such
as:-
1.Freezing by Contact with a Cooled Gas.
• It is known by many names, such as cabinet freezing, air-blast freezing, belt freezing, spiral freezing and tunnel freezing.
2.Cryogenic freezing
• Liquefied gases directly contact the foods in cryogenic freezing [1].

EMERGING TECHNOLOGY
• Isochoric is an alternative preservation technique developed by Rubinsky
and his group.
• Isochoric freezing preserves food products at sub-freezing temperatures
without ice formation inside the product.
• The food product is immersed in an isotonic solution and brought to a sub-
freezing temperature inside the closed chamber.
• During freezing, ice expands in volume, increasing the pressure.
• However, some volume remains unfrozen due to the Le chatelier's principle.
• A chamber is designed for food in a non-frozen section, then preserved at
sub-freezing temperature without internal ice formation.
• This separation from ice and food is impossible in the conventional freezing
process.
• ISOCHORIC FREEZING
• Why is it different from other methods
Fresh
Spinach
Frozen
via Isochori
c System
Commercially
Frozen
Roberto Avena-Bustillos (left) and Cristina Bilbao-Sainz
demonstrate the use of isochoric freezing chambers. Photo
courtesy of the U.S. Department of Agriculture [2]

• The food material is immersed in an isotonic solution inside a rigid container capable of withstanding elevated pressure.
• Materials such as stainless steel cylinders, carbon fibre composites, and hard phenolic thermosets with pressure
transducers and rupture disks are employed for isochoric processes.
• Then, ice crystals are introduced into the container as the nucleation site, and the chamber is tightly packed.
• Inserting this nucleator to preserve food materials in their aqueous phase without forming ice crystals is essential.
• The chamber is then sealed with a metal screw to restrict any air passage in and out of the container [3].
In a typical Isochoric process,

• By Cristina Bilbao-Sainz et al., 2021
• This investigation looked into tomato preservation using
isochoric freezing.
• Isochoric freezing was compared with freezing under isobaric
conditions and with methods of food preservation at 10oC cold
storage and quick individual freezing (IQF).
• The nutritional and physicochemical qualities were assessed.
• The findings indicate that it is possible to preserve tomatoes by
isochoric freezing while keeping their physicochemical and
nutritional qualities close to those of fresh tomatoes, which may
have applications in the industrial preservation of tomatoes [4]
[5].
PRESERVATION OF GRAPE TOMATO
BY ISOCHORIC FREEZING
Fig 1: Photograph of fresh grape tomato and
preserved tomatoes after four weeks [4]
Fig 2: Schematic of an isochoric system (two left
panels), photograph of the isochoric system,
right panel [5]

IMPACT ON MICRO-ORGANISMS
IMPACT ON ENZYME
• The isochoric method helps lessen food browning. When potatoes were kept
at 5 °C under isochoric refrigeration as opposed to isobaric freezing, there
were noticeable differences in their colour.
FOOD QUALITY IMPACT
• A constant-volume preservation method in a closed rigid container can
better retain the food's quality. For instance, potatoes lose weight at the
same temperature in an isobaric freezing system. In contrast, when stored in
an isochoric refrigeration system (5 °C) system immersed in a 10% (w/w)
sucrose solution, potatoes experience no weight loss.
• Escherichia coli was shown to suffer from membrane damage, changes in
the size and form of the cell, protrusions, ruptured membranes, and the
outflow of intracellular materials after being isochoric-cooled to 15 °C.
A comparison of freezing-damage during isochoric
and isobaric freezing of the potato [3].

FUTURE PROSPECTS
• Further research needs to be done on commercialisation since some products under high
pressure have a detrimental effect.
• Studies need to be done to understand the mechanism by which delayed enzyme activity
occurs. Similarly, the effects on micro-organisms need to be studied
• The focus of engineering research currently must be on simpler designs establishing
procedures for extensive use.
• Improvements must be made in process economics [3].

NEWS

• https://www.sciencedirect.com/science/article/pii/B9781782424475000071
• https://www.ift.org/news-and-publications/food-technology-magazine/issues/2019/november/columns/isochoric-freezing
• https://link.springer.com/article/10.1007/s12393-021-09284-x
• https://www.researchgate.net/publication/349743182_Preservation_of_grape_tomato_by_isochoric_freezing
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5438586/
REFERENCES

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