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Potassium Sorbate Profile
Active Ingredient Eligible for Minimum Risk Pesticide Use
Brian P. Baker and Jennifer A. Grant
New York State Integrated Pest Management, Cornell University, Geneva NY
Label Display Name: Potassium sorbate Other Names: Sorbic acid, potassium salt;
(2E,4E)-2,4-Hexadienoic acid, potassium salt;
Active Components: Potassium sorbate Potassium (E,E)-1,3-pentadiene-1-carboxylic
acid; 2-propenylacrylic acid; Sorbistat-K; Ka -
CAS Registry #: 24634-61-5 lium-(2E,4E)-2,4-hexadienoat (German); Kali-
um-(2E,4E)-2,4-hexadienoat (French)
U.S. EPA PC Code: 075902
Other Codes: BRN: Obsolete CAS Number: 590-00-
CA DPR Chem Code: 1132 1; SMILES: C/C=C/C=C/C(=O)[O-].[K+]; FEMA 2921;
IFN 8-03-761; INS 202
Summary: Potassium sorbate is a food preservative that has fungicidal and other antimicrobial proper-
ties. It is also an ingredient in insect repellents, and it is often used as to prevent the degradation of other
active ingredients. Formed as the potassium salt of sorbic acid, which occurs naturally in foods, potassium
sorbate inhibits bacterial and fungal growth through biocidal modes of action.
Pesticidal Uses: Primarily used as a fungicide, bactericide and algicide. Used as a seed treatment and a
post -harvest handling fungicide. Also used with various essential oils as an insect repellent.
Formulations and Combinations: Potassium sorbate can be used as a seed treatment with sodium
propionate and various polymers (Patil 2001). It is also used in a number of combinations for control of
spoilage organisms in food and feed processing (Dorko et al. 2014). Citric acid can be used as a stabiliz-
er for sorbic acid and its salts (Montagna and Lashley 1958). Previously registered pesticides contained
potassium sorbate as an active ingredient with parathion.
Basic Manufacturers: Apac Chemical, Celanese Nutrinova, FBC Industries, Spectrum Chemical, Wuxi Daxin.
Safety Overview: Potassium sorbate has been safely used as a food additive with anti -microbial properties.
This document profiles an active ingredient currently eligible for exemption from pesticide registration when used in
a Minimum Risk Pesticide in accordance with the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) section
25b. The profile was developed by the New York State Integrated Pest Management Program at Cornell University,
for the New York State Department of Environmental Conservation. The authors are solely responsible for its con-
tent. The Overview Document contains more information on the scope of the profiles, the purpose of each section,
and the methods used to prepare them. Mention of specific uses are for informational purposes only, and are not
to be construed as recommendations. Brand name products are referred to for identification purposes only, and
are not endorsements.
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Potassium Sorbote Profile
Background
Potassium sorbate is a preservative and antimicrobial agent for foods, cosmetics, and pharmaceuti-
cals(Merck 2015). Specifically, it is used as mold and yeast inhibitors in dairy products, chemically leav-
ened baked goods, fresh and fermented vegetables, dried fruit, beverages, confections, and smoked meat
and fish (Somogyi 2000).
Potassium sorbate is the potassium salt of the carboxylic acid, sorbic acid. Sorbic acid occurs naturally
in small quantities in the fruits of various plants. In the berries of the mountain ash (Sorbus aucuparia) it
occurs as the lactone, and is called parasorbic acid.
The antimicrobial properties of sorbic acid were first discovered in the late 1930s and early 1940s (Dorko
et al. 2014). The potassium salt of sorbic acid is the preferred form for food applications. Potassium
sorbate disassociates in solution to ionic potassium and sorbic acid. Sorbic acid inhibits the transport of
carbohydrates into yeast cells, inhibits oxidative and fermentative assimilation, and uncouples oxidative
phosphorylation in a variety of bacteria (Dorko et al. 2014).
Chemical and Physical Properties
The molecular structure of potassium sorbate is shown in Figure 1.
Figure 1
O
- +
H 3 C O K
Source: (EMBL 2015)
The physical and chemical properties of potassium sorbate appear in Table 1.
Table 1
Physical and Chemical Properties of Potassium Sorbate
Property
Characteristic/Value
Molecular Formula:
C,H,KO,
Molecular Weight:
150.22
Percent Composition:
C 47.97%, K 26.03%, O 21.30%, H 4.70%
Physical state at 25°C/1 Atm.
Crystals
Color
White
Odor
Characteristic
Density/Specific Gravity
Melting point
Boiling point
Solubility
Vapor pressure
1.363 g/ml @ 25°C
Decomposes above 270°C.
446'
At 20°C: water 58.2%; alcohol 6.5%
At 20°C: <0.01 mm; At 143°C: 50 mm
Source
(Merck 2015)
(Merck 2015)
(Merck 2015)
(Merck 2015)
(HSDB 2015)
(HSDB 2015)
(Spectrum 2010; HSDB 2015)
(Spectrum 2010; Merck 2015)
(EPI 2012)
(Merck 2015)
(Merck 2015)
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Potassium Sorbote Profile
Property
pH
Octonol/Water (K j coefficient
Viscosity
Miscibility
Flammability
Storage stability
Corrosion characteristics
Air half life
Soil half life
Water half life
Persistence
Characteristic/ Value
Not found
-2.19
N/A
Not found
Not found
Stable; incompatible with strong oxidizing
agents.
Not corrosive to glass
2.6 hrs
416 hrs
208 hrs
412 hrs
Human Health Information
Source
(EPI 2012)
(Royal Society of Chemistry 2014)
(Spectrum 2010)
(EPI 2012)
(EPI 2012)
(EPI 2012)
(EPI 2012)
Values reported are specifically for potassium sorbate unless otherwise reported. Sorbic acid is not
eligible to be an active ingredient in minimum risk pesticides, however, potassium sorbate is because it
readily disassociates into sorbic acid in solution. Toxicology studies of sorbic acid will generally be buff-
ered with either sodium or potassium in solution QECFA 1966). Sorbic acid has low mammalian toxicity,
including for humans. However, a review of the literature concluded that "a small but ill-defined subgroup
may suffer idiosyncratic reactions to this preservative [sorbic acid]" (Walker 1990). These include contact
dermatitis (Le Coz 2005), urticaria (hives) (Hannuksela and Haahtela 1987), stinging sensations, and'burn-
ing mouth syndrome' (Lamey et al. 1987; Haustein 1988).
Acute Toxicity
The acute toxicity of potassium sorbate is summarized in Table 2.
Study
Acute oral toxicity
Acute dermal toxicity
Acute inhalation
Acute eye irritation
Acute dermal irritation
Skin sensitization
Sub -chronic Toxicity
Table 2
Acute Toxicity of Potassium Sorbate
Results
Rat: 4,920 - 6,170 mg/kg
Not found
Not found
Not found
Not found
Not found
The sub -chronic toxicity of potassium sorbate is summarized in Table 3.
Source
QECFA 1966; Walker 1990)
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Potassium Sorbote Profile
Table 3
Sub -chronic Toxicity of Potassium Sorbate
Study
Repeated Dose 28-day Oral Toxicity Study in Rodents
90-Day oral toxicity in rodents
90-Day oral toxicity in non -rodents
90-Day dermal toxicity
90-Day inhalation toxicity
Reproduction/development toxicity screening test
Combined repeated dose toxicity with reproduction/
development toxicity screening test
Prenatal developmental toxicity study
Reproduction and fertility effects
Results
Source
Not found
Mice: No adverse effects (sorbic
(Hendy et al. 1976;
acid)
LSRO 1975)
Rats: Slight enlargement of liver
Dog: No adverse effects
(Walker 1990)
Not found
Not found
Rat: No significant difference from
QECFA 1974)
control
Not found
Not found
Not found
While allergic reactions to potassium sorbate are considered unusual, there has been a reported incident of
repeated occupational exposure in a dairy plant leading to severe rashes in an exposed worker (Le Coz 2005).
Chronic Toxicity
The chronic toxicity of potassium sorbate is summarized in Table 4.
Table 4
Chronic Toxicity of Potassium Sorbate
Study Results Source
Chronic toxicity Ames: Negative (Walker 1990)
Carcinogenicity Mouse: Negative QECFA 1974; LSRO 1975)
Combined chronic toxicity & carcinogenicity Not found
In evaluating GRAS status of potassium sorbate, the FDA reviewed four animal studies for carcinogenesis.
One was inconclusive and three had no carcinogenesis in the test animals (LSRO 1975). Potassium sorbate
is not identified as carcinogens by the International Agency for Research on Cancer (IARC 2014), is not on
the California Proposition 65 list of known carcinogens (Cal -EPA 1997), and does not appear on the Toxics
Release Inventory (TRI) Basis of OSHA Carcinogens (US EPA Toxics Release Inventory Program 2015).
Human Health Incidents
The National Pesticide Information Center (NPIC) received two human health incident reports involving ex-
posure to potassium sorbate (NPIC 2016). Both involved other pesticides in addition to potassium sorbate.
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Potassium Sorbate Profile
Environmental Effects Information
Effects on Non -target Organisms
No data on the effects of potassium sorbate on non -target organisms were found. NPIC received two ani-
mal incident reports involving exposure to potassium sorbate (NPIC 2016). Both involved other pesticides
in addition to potassium sorbate.
Environmental Fate, Ecological Exposure, and Environmental Expression
No data on the environmental fate, ecological exposure, and environmental expression of potassium
sorbate were found. The EPA predicts potassium sorbate to be readily biodegradable (EPI 2012).
Environmental Incidents
No other studies indicating environmental impacts of potassium sorbate were found. NPIC received two
reported incidents involving potassium sorbate; these were neither human health nor animal related and
contained no narrative details (NPIC 2016).
Efficacy
Fungicidal and Anti -microbial Activity
Given its anti -microbial efficacy and record of safety as a food additive, there is interest in using potassi-
um sorbate as a fungicide, mainly for post -harvest handling, but also as a seed treatment and in field use.
Sorbates have the ability to inhibit the growth of yeast at the surface of food during fermentation, but do
not inhibit yeasts and other organisms that are used in the fermentation process (Somogyi 2000). Salts
of sorbic acid may have a synergistic effect with various synthetic fungicides, such as methylchloroisothi-
azolinone or methylisothiazolinone, and salts such as magnesium chloride, mangnesium nitrate, and so-
dium benzoate when used in plant tissue culture media (Guri and Patel 1998). Over 150 different molds,
bacteria, and yeasts —including most food -borne pathogens —are suppressed by potassium sorbate and
other salts of sorbic acid (Dorko et al. 2014).
Among the molds inhibited are members of the genuses Alternaria, Aspergillus, Botrytics, Cercospora, Fu-
sarium, Penicillium, Rhizoctonia, and Trichoderma. Yeasts inhibited include species of Candida, Cryptococcus,
Rhodotorula, and Saccharomyces. Bacteria inhibited include Acetobacter, Bacillus, Clostridium, Pseudomona,
Salmonella, and Staphylococcus, species as well as Escerichia coli. Potassium sorbate at concentrations of
0.05, 0.10 and 0.15% delayed or prevented Aspergillus flavus and Aspergillus parasiticus spore germination
and initiation of growth. Potassium sorbate also greatly reduced or prevented production of aflatoxin B1
by both species for up to 70 days at 12°C, with aflatoxin production essentially eliminated with concentra-
tions of potassium sorbate above 0.10% (Bullerman 1983).
Various citrus fruits were inoculated with green mold (Penicillium digitatum) and blue mold (Penicillium
italicum). The infected fruit was treated with a potassium sorbate dip 24 hours after inoculation at various
concentrations and temperatures. When compared with a plain water dip control, a treatment with a 3%
solution of potassium sorbate in hot (62°C or 143°F) water for 30 seconds was able to control both molds,
achieving about a 98% reduction in infection on Valencia oranges (Montesinos-Herrero et al. 2009). This
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Potassium Sorbate Profile
was comparable to the results with the thiabendazole post -harvest fungicide imazalil. Although the
results were not conclusive, the same study showed that potassium sorbate significantly reduced the
amount of imazalil needed for efficacy, suggesting that potassium sorbate may have a synergistic effect.
In another set of experiments conducted with P. digitatum, potassium sorbate was found to work best at
a pH of between 4 and 6 (Smilanick et al. 2008). The EC95 of potassium sorbate at a pH of 4 was 0.065%. P.
italicum was able to develop a tolerance, and prolonged exposure produced evidence that it is possible
to select for potassium sorbate resistant strains (Schroeder and Bullerman 1985). P. digitatum did not
develop a tolerance.
Peaches (Prunus persica) inoculated with one of the fungi associated with brown rot (Monilinea laxa), then
treated with potassium sorbate, had significantly lower infection rates and fruit damage than untreated
fruit. Potassium sorbate's efficacy was estimated to be about 90% (Gregori et al. 2008). The study con-
firmed that the potassium sorbate treated fruit also had lower rates of other incidental Monilinea species
and less brown rot damage.
In California, organically grown grapes (Vitis vinifera) treated post -harvest with either 0.5% or 1.0% solu-
tion of potassium sorbate in 20% alcohol, had Botrytis cinera (gray mold) infection levels that were not
significantly different from those on grapes treated by sulfur dioxide (SO) fumigation (Karabulut et al.
2005). Other ingredients in the treatment were not disclosed.
Pre -harvest field applications of potassium sorbate to table grapes as a preventive fungicide yielded vari-
able results over a three-year period. While one year's data under California field conditions showed no
significant difference in incidents between potassium sorbate, various chitosans, and a fungicide program
combining pyrimethanil, cyprodinil, fludioxonil, pyraclostrobin and boscalid. All treatments used the sur-
factant Latron B1956 from BFR Products. The differences in averages over the three years between potas-
sium sorbate—with a 2.8% incidence of gray mold —and the no -treatment control with a 3.9% incidence
was barely significant to insignificant (Feliziani et al. 2013). The potassium sorbate treated grapes also had
lower berry size and higher solids.
Seeds and plant propagants may be treated with potassium sorbate to protect them from soilborne
diseases. In plate studies to evaluate various food preservatives' efficacy to suppress the soil pathogens
Fusarium oxysporum, Macrophonia phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum in a medium
of sand and cornmeal, potassium sorbate suppressed all four species (Arslan et al. 2009). Treatment lev-
els were 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5 and 2.0%, w/v. The only other food additive to do so was ammonium
bicarbonate.
Mature potato (Solanum tuberosum) tubers were dipped in 1 %, 2%, and 4% solutions of potassium sor-
bate, then placed on agar plates inoculated with R. solani and Fusarium roseum. The 4% solution of potas-
sium sorbate was effective at controlling R. solani but not F. roseum (Leach et al. 1983). Silver scurf (Hel-
minthosporium solani) in potatoes was best controlled by 0.1-0.2 M solutions of potassium sorbate when
compared with six other fungicidal salts, although all salts showed inhibitory properties relative to the
control (Olivier et al. 1998). Cowpeas (Vigna sinensis) treated with a seed dressing of 9% potassium sorbate
had an 89% decrease in incidents of Fusarium and a 91 % reduction in Rhizoctonia infections (EI-Mougy et
al. 2004).
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Potassium Sorbate Profile
Standards and Regulations
EPA Requirements
The EPA has explicitly exempted potassium sorbate from the requirement of a tolerance [40 CFR
180.1233].
FDA Requirements
Potassium sorbate is Generally Recognized As Safe (GRAS) for use as a food ingredient by the FDA [21 CFR
182.3640].
Other Regulatory Requirements
Potassium sorbate is synthetic and does not appear on the National List of allowed synthetic substances
allowed for crop production. Therefore, it is prohibited for use in organic production [7 CFR 205.105(a)].
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Potassium Sorbote Profile
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