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(38). Thus, its use has been well documented in industries
such as health care, sports, rubber and plastics, research, construction, music, electronics, food and beverage, automotive,
and pharmaceutical and metal manufacturing (1, 38).
Dry ice, known as solid CO2, is often confused with LN2.
However, when LN2 reaches its boiling point temperature of
−196°C, it undergoes vaporization (transition from liquid
to gas) (3). In contrast, dry ice undergoes sublimation
(transition from solid to gas) when it reaches a temperature
of −78.5°C (3). Although both can be used for cryogenic
applications, different industries prefer to use one over the
other depending on their temperature requirements, costs,
and ease of use. In retail food settings, LN2 tends to be used
more often than dry ice, which is why this paper primarily
focuses on LN2.
In the food and beverage industry, the commercial use of
LN2 as a coolant is well established (3). It is an ideal freezing
agent because of its ability to reduce chemical and microbial
spoilage in foods and beverages, while retaining optimum
flavor and quality (1, 34). This is accomplished by using the
cold temperature of LN2 to help slow heat production and
oxidation during processing, packaging, and shipping (3).
Besides chilling to prolong the shelf life of various foods like
meats, dairy products, produce, condiments, sauces, and
desserts, LN2 also has many other applications (3). These
include adding pressure to bottled and canned beverages to
allow for stronger and more rigid packaging, using freezing
processes to grind meats and spices, and speeding up
cooling during product layering to prevent the blending of
constituent parts (3, 18).
Apart from using LN2 as a food processing and preservation aid, retail food and beverage establishments are
now capitalizing on trends that involve using it in more
unconventional ways. Such trends include applying LN2
to foods or glassware just prior to consumption, to create
aesthetically pleasing smoke-like effects and novelty frozen desserts like ice cream in an instant (3, 36). Such effects occur because LN2 is extremely cold, and it produces
a visible fog upon evaporation in warmer air settings (2).
This method of combining scientific techniques with culinary art to prepare and present food is sometimes referred
to as molecular gastronomy (3, 8). Culinary applications
of LN2 include flash freezing foods and liquids to create
garnishes, crafting unique shapes out of food, improving
cooking processes, manipulating textures, and enhancing
visual appeal (3, 8).
To consumers, these novelty foods and beverages seem
like harmless fun. However, there is limited awareness
about the potential health risks LN2 poses to consumers if
foods or liquids are served directly after the application of
LN2. When used in manufacturing as a processing aid, the
risks are minimal because, by the time the product reaches
the consumer, it is no longer as cold and the LN2 has fully
evaporated (36). However, that is not always the case when

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it is applied to desserts and drinks at the point of purchase.
Consequently, case reports are now emerging of patrons
suffering acute, sometimes severe, injuries after improper
ingestion of LN2. Therefore, from a public health perspective,
research on this topic is important to identify and reduce
any risks that may impact the health and well-being of
consumers. To evaluate the likelihood of risk associated with
LN2 consumption, a literature review and qualitative risk
assessment was performed.
METHODS
The focus of the search strategy for this systematic
review was to identify, extract, and analyze data from the
literature that was most relevant to LN2 consumption.
This began with a comprehensive search for scholarly
publications and clinical case reports in the databases Ovid
MEDLINE, Web of Science, and TOXNET. An Internet
search on Google Scholar was also performed to obtain
additional scholarly resources on LN2. These searches were
conducted using the following key words, truncations, and
Boolean operator combinations: ( " liquid nitrogen.m_titl. " )
AND ( " drink*.ti,ab. " OR " beverage*.ti,ab " OR " cocktail*.
ti,ab. " ), ( " ingestion*.ti,ab. " OR " consumption*.ti,ab. " OR
" inhalation*,ti,ab. " ), ( " injury*.ti,ab. " OR " risk*.ti,ab. " OR
" danger*.ti,ab. " OR " effect*.ti,ab. " ), ( " frostbite*.ti,ab. " ),
( " asphyxiation*.ti,ab. " ), ( " ice cream*.ti,ab. " OR " snack*.
ti,ab, " ), and ( " barotrauma*.ti,ab. " OR " gastric perforation*.
ti,ab. " OR " pneumoperitoneum*.ti,ab. " ). A more detailed
outline of this search strategy can be found in Appendix A.
Because studies on LN2 consumption are limited, search
restrictions on language, geographical location, experimental
design, and dates were not applied. Cases of LN2 exposure
via inhalation, ingestion, or physical contact in nonfood
settings were also reviewed for relevant information. When
non-English articles that were related to LN2 consumption
were found, Google Translate was used to interpret the
findings into English. Additional articles were also found by
scanning through the reference sections of articles identified
in the search. Furthermore, to address potential research
gaps and gather additional evidence on LN2 consumption,
gray literature sources were also reviewed. These resources
were retrieved from Google using various combinations
of the following search terms: " liquid nitrogen, " " treats, "
" snacks, " " ice cream, " " cocktails, " " dessert, " " dangers, " " risks, "
" regulations, " and " national/international food surveys. " Due
to the plethora of search results generated, information was
only collected from the top 100 search results. They consisted
of national and international food policy statements,
government publications, newspaper articles, statistical
reports, and other Web-based publications. See Appendix B
for more information regarding the websites and databases
used to retrieve gray literature. Overall, a total of 43 peerreviewed and non-peer-reviewed sources were synthesized
for this review.

Food Protection Trends - May/June 2021

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