Food Protection Trends - May/June 2021 - 295

HAZARD IDENTIFICATION
Although it is not common for LN2 to be applied to foods
and beverages immediately before consumption, this practice
has been gaining popularity in recent years (3, 36). Thus,
case reports of people suffering from food-related injuries
are beginning to appear (3, 36). Whereas cases are still rare,
some of the injuries being reported have been quite severe,
making this food trend a major cause for concern. Despite
limited research in this area, this review of the literature
revealed several health outcomes that may be associated with
improper ingestion and handling of LN2. These are described
in further detail in the following subsections. Although not
all of these have been associated with exposure through foods
and beverages, they provide information that is helpful in
reducing possible LN2 risks to consumers and food handlers.
Potential health outcomes associated with LN2 inhalation
Nitrogen gas is a simple asphyxiant (26). In the event of
a spill or leak in an enclosed area at room temperature, LN2
will evaporate and displace some of the oxygen in the air (3,
26). Without proper ventilation systems in place, individuals
can become oxygen deprived if nitrogen levels in the air
surpass 88% (26). This can lead to asphyxiation and is very
dangerous because it may occur without warning and may
potentially result in death (19, 20, 25). Although this is not a
risk for consumers, it may be a risk for food handlers working
with large amounts of LN2 in a small room.
Potential health outcomes associated with LN2 contact
LN2 can cause severe thermal damage to the skin, eyes,
and internal organs if not handled safely (26, 31). Examples
of thermal-related injuries that may result following contact
with LN2 include frostbite, blisters, ulcers, edema, and tissues
necrosis (9). However, the severity of injury is dependent on
the duration and area of contact. In most cases, injury occurs
when bare skin and other exposed tissues come in contact
with LN2 for more than a few seconds (26). For example,
this can happen if individuals hold LN2-coated treats in their
mouths for too long, or if the snack sticks to their gums. In
other instances, individuals can be fully covered and wearing
protective gloves but can still end up with thermal injuries
after handling or working with LN2 (31). Thus, both direct and
indirect exposure to LN2 should be avoided to prevent injury.
Brief contact with small amounts, e.g., 2 to 3 mL of LN2,
however, does not always result in cryogenic injuries (2,
3). The reason for this has to do with a phenomenon called
the Leidenfrost effect (2, 15). To illustrate this effect, one
can envision LN2 as a droplet encountering a surface with
a temperature far above its boiling point (7). When this
occurs, the LN2 rapidly starts to evaporate and pressure from
the vapor builds up as it tries to escape from beneath the
droplet (7). At a certain level of pressure, the vapors elevate
the droplet, forming an insulating film of vapor between the
droplet and the surface (2, 3, 7). As a result, this insulating

film creates a barrier between the two surfaces, which causes
a reduction in thermal transfer and injury (2).
Potential health outcomes associated with LN2 ingestion
When LN2 is added to desserts and drinks immediately
before consumption, the belief is that it will evaporate and,
therefore, pose no harm to customers (36). Unfortunately,
this is not always the case because sometimes there will
be residual LN2 that remains on the bottom of a serving
container (11). In addition, LN2 is tasteless (26). Thus,
if consumers are not instructed to wait before the LN2
completely vaporizes, they might accidentally ingest it
without realizing it (3).
The most serious injury faced after ingesting LN2 is
gastrointestinal barotrauma, which develops due to an
increase in pressure within the stomach (2, 10, 21-23, 30,
41-43). This occurs because, when LN2 enters the body, it
immediately begins to evaporate upon contact with surface
temperatures higher than its boiling point (39). Furthermore,
as the LN2 travels from the mouth to the esophagus and into
the stomach, the vapors that form along the way can lead to
a large increase in pressure (39). The reason for this is that
LN2 has a liquid-to-gas volume ratio of 1:694 (2, 30). This
means that, when LN2 evaporates, its volume will increase
by about 700 times within the body. As a result, patients
may experience severe and painful abdominal distension
following ingestion, because of the increase in volume and
pressure within the gastrointestinal tract. (2). This rise in
pressure typically leads to tissue necrosis and gastric rupture
in the lesser curvature of the stomach, which requires surgery
to fix (30).
Potential health outcomes associated with biological
contamination
LN2 can also serve as an effective storage medium for
pathogens (29). Microorganisms that can potentially survive
after being cryopreserved by LN2 include bacteria, fungi,
yeasts, and viruses (29, 35). Examples of microorganisms
that have been found in LN2 tanks used to store biological
specimens include Escherichia coli, Bacillus cereus, Mucor
spp., Staphylococcus spp., and Pseudomonas aeruginosa, some
of which can be spread through unhygienic practices (29).
Although there have not been any reported incidents of
consumers coming into contact with biological hazards from
LN2 in their foods and beverages, it is still a potential hazard.
HAZARD CHARACTERIZATION
Given its relatively new applications in the retail food and
beverage industry, no definitive dose-response relationships
have been established for ingesting, inhaling, or coming into
contact with LN2. However, based on the data available, it
is apparent that the severity of injury is dependent upon the
duration and area of contact, as well as the volume of LN2
one comes into contact with. For example, larger amounts of

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