Food
Safety Assessment Techniques for Cultured Meat - Part II
As
cultured meat products are novel and there are various food safety concerns
around them, in-vitro tests can be a major starting point for safety testing,
since they are more efficient and less resource intensive than in-vivo testing,
which also can avoid or reduce animal testing. Hence, in-vitro testing can use
to screen and identify potential hazards, which can be used occasionally to aid
in dose selection for conventional animal tests. Thus, in-vitro tests are
typically performed on ingredients rather than whole foods, where test
substances must be solubilized in media or in order to perform these tests on
whole foods, samples need to be freeze-dried and homogenized or processed,
which presents a technical challenge and likely does not accurately represent
the final product. Nevertheless, in vitro methods can also be useful for
endpoint testing for any inputs to the process or novel proteins, contaminants,
degradation products, metabolites, or by-products present in the final cultured
meat product.
At this
stage, there are only a few in vitro tests relevant to food safety have been
validated for stand-alone use on cultured meat products beyond genotoxicity and
allergenicity testing, where nonstandard test methods exist, such as
cytotoxicity, digestion, and microbiome tests. Nevertheless, these types of
tests generally lack regulatory acceptance as a complete replacement for animal
studies. Thus, they may be useful in supporting information as part of a
broader safety assessment strategy, where methods like cytotoxicity studies can
be used as a screening tool, and may be more sensitive than in vivo tests for
demonstrating safety at the cellular level. Hence, primary cells or co-cultures
of cells representing the gastrointestinal tract are used to mimic realistic
scenarios. The stability and digestibility of foods can be analyzed using in-vitro
digestibility tests under the processing conditions such as heating, freezing,
or with simulated saliva and gastrointestinal fluids. the products of these
conditions can then be used in toxicity tests to dose relevant cells, such as
stomach cells to determine their safety.
Further,
the gut microbiome is a complex ecosystem of microorganisms that support
physiological, biochemical, and immunological functions. The presence of
residues such as antibiotics, metabolites, or growth factors, contaminants in
food, or changes in micronutrient composition, such as vitamins, iron, and
fatty acids, can alter the microbiota composition. Hence, it is vital to examine
the relationship between the gut microbiome and cultured meat products, where in-vitro
assays can measure positive or negative impacts on the gut microbiome with
increased recognition of the role of the microbiome in maintaining health. However,
microbiome communities are highly diverse and individualized, where their
relationship to adverse human health outcomes is still not well understood,
even for conventional foods.
Tests
for Allergenicity
There
have been unexpected allergenicity observed in genetically modified plants,
such as potatoes and soybeans, which had generally demonstrated allergenicity
to their conventional counterparts. Allergenicity is a key focus of food safety
assessment, where comparative testing has been used to assess allergenicity frequently
in genetically modified foods, which is also expected in cell-cultured meats
that are manufactured to mimic existing products. On the other hand, it also has
the potential to reduce the allergenicity of products.
If any
novel proteins are expressed in cell-cultured meat, in-silico assessments can
evaluate sequence homology and identify structural similarities to existing
proteins and their characterization can help identify toxic or allergenic
properties. Nonetheless, there is a multitude of existing allergenicity tests,
including the pepsin resistance test, immunochemical cross-reactivity testing
with IgE from the serum of individuals known to be allergic to similar
proteins, in vitro IgE-binding tests such as the radioallergosorbent test or
ELISA, and skin prick testing. The use of animal models to identify human
sensitivity to novel allergens may not be reliable or necessary unless in-silico
or in-vitro tests indicate a need for further testing.
Tests
for Genotoxicity
Many validated in vitro genotoxicity tests screen endpoints such as potential mutagenic activity, DNA strand breaks, and cytogenicity such as OECD 476, 2016; OECD 490, 2016; OECD 487, 2016; OECD 473, 2016; OECD 471, 2020 and the results of these tests may predict mutagenicity or carcinogenicity. These testing will be useful in identifying potentially genotoxic inputs to the manufacturing process. If it is deemed necessary to apply these tests to whole foods rather than select inputs, some of these techniques may require modification. The most common genotoxicity test, for example, the Ames bacterial mutagenicity test (OECD 471, 2020.), may not be appropriate for meats high in histidine (e.g., pork, beef, lamb, chicken, turkey, fish) because this amino acid interferes with the test. If a review of in vitro tests and available toxicokinetic data indicate the possibility of genotoxic effects, in-vivo genotoxicity tests may be considered such as OECD 486, 1997; OECD 478, 2016; OECD 489, 2016; OECD 475, 2016; OECD 474, 2016; OECD 488, 2020, though this is not expected for cell-cultured meats.
In-vivo
Testing
Cell-cultured
meat that is biochemically, genetically, and compositionally similar to
existing foods should theoretically be as safe as its conventional
counterparts. However, there is uncertainty about it as to whether in-vivo
testing will be required for novel inputs or products with significant
differences from existing foods because they contain potentially hazardous
proteins or metabolites, or lack a conventional counterpart. In some regulatory
jurisdictions, testing in rodents remains a required baseline study for novel
foods and may help assuage safety concerns. Yet, from an industry perspective,
where the avoidance of animal use is a key tenet, the performance of in-vivo
testing to demonstrate safety is not desirable. Some regulatory jurisdictions
promote alternative testing strategies like nonanimal testing, but the
availability and validation of reliable and representative in-vitro tests that
represent food consumption and mimic the human gastrointestinal tract that can
fully replace in-vivo testing remains a barrier and a research need.
The tests
such as the Subchronic 90-day feeding trial (OECD 408, 2018), where the rodents
are fed with a test substance daily for 90 days, are typically a fundamental
element of ingredient safety testing. The test serves as a basis to demonstrate
safety for food, feed, pharmaceuticals, agricultural products, pesticides,
contaminants, and industrial chemicals, which assesses body and organ weight,
feed consumption, blood and urine chemistry, histopathology, and animal
behavior to determine direct or systemic effects resulting from consuming the
food. The test is generally accepted as sufficient to identify adverse effects
that could occur after repeat and chronic exposure to a substance. Ingredients
or chemically defined substances such as micronutrients or amino acids can be
mixed into specially formulated diets to test in-vivo safety. However, animal
feeding trials may not be appropriate for whole foods such as meat and seafood.
On the other hand, to improve the reliability of results obtained from
animal-based toxicity testing toward the human safety context, animals are
generally fed the test substance at levels that exceed those expected for human
consumption of the product. However, animals may not find the food palatable,
and feeding abnormally high doses of food may cause nutritional imbalances in
the diet. Therefore, the amount of whole food that can be incorporated into the
test animal diet is limited by bulk and nutritional imbalance, and the
detection of adverse effects resulting from any toxicants or antinutrients is
likely to be missed.
Further
studies may be warranted, where biochemical, in-silico or in-vitro tests also
indicate potential concern. If genotoxicity or subchronic testing of
ingredients suggests a need for chronic or carcinogenicity studies, standard
tests for chronic testing (OECD 452, 2018), carcinogenicity testing (OECD
451, 2018), or combined chronic/carcinogenicity testing (OECD 453, 2018)
exist. If there are any indications from subchronic studies that reproductive
organs or systems involved in development may be affected, then in-vivo
reproductive and developmental toxicity testing may be performed. Tests such as
two-generation reproductive toxicity studies (OECD 416, 2001) or prenatal
developmental toxicity studies (OECD 414, 2018) may be applicable. If
subchronic testing and allergy testing demonstrate possible immunotoxic
effects, further investigation of the endpoints assessed in subchronic tests
may be warranted. For example, histological assessment of lymphoid organs and
tissues, and hematological assessment of various cells and immunoglobulin
levels may give further indication of immunotoxic effects. As with all in-vivo
studies, the development of alternative testing methods to effectively replace
these tests is preferred and is a research priority for the safety testing of
cell-cultured products.
Human
Studies
For
food ingredient safety assessment, there are only a few foods that have
required human studies after a demonstration of similarity to foods that have a
history of safe consumption, and/or alternative testing studies and animal
studies have typically been accepted as sufficient to demonstrate safety for
consumption. On the other hand, human studies may be used for whole foods, but
are typically related to tasting/palatability, short-term testing for
digestibility and tolerance, allergenicity, testing in support of health
claims, or for specialized foods where there is a need to investigate potential
negative nutritional effects or adverse health outcomes on specific vulnerable populations,
such as food for infants and children, pregnant women, patients at increased
risk of disease, etc.
A
research gap regarding the safety of foods derived from modern technology is
whether recombinant DNA (rDNA) in meat is capable of transferring to microbiota
in the gastrointestinal tract. In theory, horizontal gene transfer (HGT)—a process
by which rDNA can pass from one species to another, such as to human gut
microorganisms or microorganisms in the environment could occur. HGT could
result in the development of populations of antibiotic-resistant organisms,
reducing the effectiveness of current antibiotics. However, most research to
date has focused on HGT potential from GE prokaryotes and plants and has
generally demonstrated that HGT events are rare or are eventually lost due to a
lack of conferred advantage and there are only a few studies have researched
the risk of gene transfer from GE mammalian cells.
Post-market
Monitoring
The post-marketing
monitoring, where large populations of consumers are evaluated over the long
term, has been used to complement premarket safety assessment for some novel
foods which may help detect rare and unintended adverse effects such as
allergic responses. Such approaches have already been successfully applied in
the medical field, but it may be challenging to adapt the approach to
cell-cultured products, because pharmaceuticals have well-controlled dosages,
and adverse outcomes are relatively easy to track in the medical context. By
contrast, it is far more difficult to monitor the adverse health effects
resulting from long-term consumption of food. However, pre-identification of
potential hazards, such as growth factors and tracking-related adverse outcomes
may be merited. Some food manufacturers have developed monitoring systems to
obtain feedback from consumers; these systems rely on various strategies such
as consumer reporting of adverse effects via hotlines, performing household
panels, interacting with market research companies and consumer associations,
evaluating supermarket data, and engaging with medical professionals and
scientific agencies.
References:
https://ift.onlinelibrary.wiley.com/doi/full/10.1111/1541-4337.12853
https://www.foodincanada.com/features/the-food-safety-advantages-of-lab-grown-meat/
https://www.frontiersin.org/articles/10.3389/fnut.2020.00007/full
https://www.centerforfoodsafety.org/blog/6458/is-lab-grown-meat-healthy-and-safe-to-consume
https://www.mdpi.com/2304-8158/10/12/2922
Many validated in vitro genotoxicity tests screen endpoints such as potential mutagenic activity, DNA strand breaks, and cytogenicity such as OECD 476, 2016; OECD 490, 2016; OECD 487, 2016; OECD 473, 2016; OECD 471, 2020 and the results of these tests may predict mutagenicity or carcinogenicity. These testing will be useful in identifying potentially genotoxic inputs to the manufacturing process. If it is deemed necessary to apply these tests to whole foods rather than select inputs, some of these techniques may require modification. The most common genotoxicity test, for example, the Ames bacterial mutagenicity test (OECD 471, 2020.), may not be appropriate for meats high in histidine (e.g., pork, beef, lamb, chicken, turkey, fish) because this amino acid interferes with the test. If a review of in vitro tests and available toxicokinetic data indicate the possibility of genotoxic effects, in-vivo genotoxicity tests may be considered such as OECD 486, 1997; OECD 478, 2016; OECD 489, 2016; OECD 475, 2016; OECD 474, 2016; OECD 488, 2020, though this is not expected for cell-cultured meats.
https://ift.onlinelibrary.wiley.com/doi/full/10.1111/1541-4337.12853
https://www.foodincanada.com/features/the-food-safety-advantages-of-lab-grown-meat/
https://www.frontiersin.org/articles/10.3389/fnut.2020.00007/full
https://www.centerforfoodsafety.org/blog/6458/is-lab-grown-meat-healthy-and-safe-to-consume
https://www.mdpi.com/2304-8158/10/12/2922
