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Beynen AC, 2019. Sorbate and sorbitol in petfoods



Sorbate and sorbitol in petfoods
Petfood Magazine 2019; Nr 2: 24-25.
Anton C. Beynen
Sorbate and sorbitol in petfoods*
*Based on article in Dutch (1)
Main points
Sorbate and sorbitol are six-carbon chains that serve as petfood preservatives. Sorbate is the acid
residue of sorbic acid (hexa-2,4-dienoic acid), a polyunsaturated, medium-chain fatty acid. Potassium
sorbate is frequently found on labels of dry petfoods. Sorbitol is a polyalcohol with a hydroxyl group
attached to each of its carbon atoms. It is incorporated into some semi-moist petfoods and treats.
Common petfood applications of potassium sorbate are 0.01 to 0.2% in the finished products; for
sorbitol the inclusion range is 3 to 12% (2). In Europe, potassium sorbate is legally classified as
technological additive for feedstuffs (3), while sorbitol is listed as feed material (4).
Potassium sorbate and sorbitol, as declared by petfood labels, are chemically synthesized
compounds. Such chemicals are label unfriendly: many dog and cat owners have an aversion to
synthetic petfood components. An American pet store chain has announced that by February 2020
all food products with potassium sorbate will be removed from the shelves (5). Sorbitol not only
serves as petfood preservative, but also as sugar substitute and oral/rectal laxative. Those
applications may evoke or amplify negative associations in the minds of pet owners.
There is little information on the metabolism of sorbate and sorbitol by dogs and cats, but combining
data from various sources gives a fair view. Sorbate likely is efficiently absorbed and then enters the
hepatic pathway of fatty acid oxidation, yielding ATP, carbon dioxide and water as end products.
Alternatively, sorbate may be converted into ketone bodies. Sorbitol is slowly and inefficiently taken
in. Absorbed sorbitol probably is partly converted into glucose and partly excreted with urine.
Data on toxicity of sorbate (cf. 6) and sorbitol in dogs are limited, while two major research reports
are available in abstract form only. As to cats, the information is even scarcer. When integrating the
accessible archives on toxicological and metabolic characteristics of sorbate and sorbitol, it follows
that their maximum contents in commercial, complete dog and cat foods are safe. This stand is
supported by lack of signals from the market about suspected associations between the
preservatives and negative health effects in dogs and cats.
In bound form, sorbic acid occurs as a natural compound. Potassium sorbate can be isolated from
berries of the rowan tree (Sorbus aucuparia), after their treatment with potassium hydroxide (7).
Fresh berries contain the equivalent of about 0.1% sorbic acid. There are cosmetics and skin care
products with potassium sorbate derived from rowan berries (8). Sorbic acid is factory synthesized
by a reaction between propanedioic acid (malonic acid) and 2-butenal.
Sorbitol occurs naturally, amongst others, in apples, pears, prunes and berries (9). Dried prunes
contain about 10% sorbitol. Industrial sorbitol is usually synthesized with corn starch as starting
material. Glucose is liberated by hydrolysis of the starch, followed by reduction of its aldehyde
moiety into a hydroxyl group, thus yielding sorbitol.
Preservative action
Sorbic acid and its potassium, sodium and calcium salts are allowed as feed preservatives (3). For
petfood, potassium sorbate is typically used, possibly due to its greater solubility in water. In
practice, the dose of potassium sorbate is 0.01 to 0.2% of the finished product (2). In an aqueous
medium, potassium sorbate dissociates after which sorbic acid also arises. The acid can pass the
cellular membrane of fungi and bacteria, accumulate in the cellular liquid and disturb metabolism,
resulting in growth retardation of the microorganisms.
Sorbitol is a humectant: the hydroxyl groups bind free water. Water with dissolved nutrients acts as
growth medium for fungi and bacteria, whereas a water-poor medium leads to dehydration of the
microorganisms. The addition of sorbitol to semi-moist petfood lowers the amount of free water,
thereby blocking growth of fungi and bacteria. Applications of sorbitol range from 3 to 12% in semi-
moist food (2).
In dogs, the digestibility of medium-chain fatty acids in dietary triacylglycerols is higher than that of
longer-chain fatty acids (10). Thus, ingested sorbate likely is efficiently absorbed by dogs and cats.
The metabolic, step-wise processes of fatty acid oxidation and coupled ATP formation probably are
comparable for dogs, cats and rats. The latter species completely degrades orally administered
sorbic acid to carbon dioxide and water (11), following hepatic beta-oxidation and/or ketogenesis.
Furthermore, the intermediary metabolism of sorbic acid was found to be identical with that of
caproic acid (hexanoic acid), pointing to similar caloric values of the two medium-chain fatty acids
In rats, radioactivity in blood and expired air was measured after oral administration of 14C-labeled
sorbitol or glucose (12). Compared with glucose, radioactivity from sorbitol appeared in blood and
expired air at lower rates. This outcome corresponds with the concepts of slow, passive absorption
of sorbitol and hepatic conversion of sorbitol into glucose, via fructose.
In 25-kg dogs, a test meal consisting of a mixture of 276 g wet food and 25 g sorbitol slightly raised
blood glucose and serum insulin concentrations (13). Sorbitol intake was equivalent to feeding dogs
a dry food with 6.7% sorbitol once a day. Under that condition, some of the absorbed sorbitol
probably is excreted in urine (14). The caloric value of sorbitol in dogs may be substantially lower
than that of glucose.
Sorbate: toxicity
There are two communications on the toxicity of potassium sorbate in dogs. A brief notice (15) reads
as follows: “.... eight dogs received 1 percent and eight dogs 2 percent potassium sorbate in the diet
for 3 months and gained the same weight as four control dogs. At autopsy, gross examination
revealed no deleterious effects attributable to potassium sorbate. “
Puppies received a semi-purified control food (n = 3) or food with 5% caproic acid (n = 3) or 5%
sorbic acid (n = 2) in the dietary dry matter (16). For formulation of the test foods, the acids were
added to the control food at the expense of 2.5% margarine fat and 2.5% sucrose. Food intake,
growth and blood hemoglobin were comparable for the three groups. The dogs’ remained in
excellent condition. Examination of organs and tissues did not reveal visible aberrances.
For four weeks, groups of two young male cats with comparable body weight received a commercial
canned food with 0, 0.1, 0.2, 0.5 or 1% sorbic acid (17). The authors gave the following description of
the results: “Sorbic acid was readily acceptable at all dose rates, and the clinical behavior and
appearance of all the cats remained normal throughout the course of the trial.” Two additional cats
were fed for one week at a level of 2%, this dosage not producing any toxic effects.
Sorbitol: toxicity
Dogs fed a dry, extruded kibble diet with 7.2% sorbitol instead of beet pulp had unchanged, good
feces quality. When the sorbitol was level was doubled, the extra addition being at the expense of
brewers’ rice, the dogs did not experience diarrhea, but looser stool was observed (13). The animals
were allowed to eat the diet at their leisure and were not given a large dose at a single time.
Perhaps, some dogs do develop diarrhea when fed a semi-moist diet with 12% sorbitol once daily.
Dietary sorbitol concentrations higher than those studied (13) may not only induce diarrhea, but also
polyuria. Due to the low absorption efficiency, significant amounts of sorbitol will reach the large
intestine, resulting in excessive bacterial fermentation and osmotic diarrhea. In dogs, a considerable
fraction of intravenously administered sorbitol reached the urine (14). This may be associated with a
diuretic effect (18), due to water dragging by the excreted sorbitol. The dietary level at which
sorbitol causes diarrhea and polyuria is unknown.
In excerpt form, a two-year study has been described in which 8 female and 8 male Beagle dogs
consumed a food without or with 20% sorbitol (19). Sorbitol feeding was found to increase weight
gain, while relative organ weights were unchanged or slightly lowered. There were no sorbitol-
related, visible tissue changes. Feces consistency and urine production are not mentioned.
For three days, three times daily, dogs were administered sorbitol by stomach tube (20). A dose of
12 ml distilled water with 25% sorbitol had no visible, irritating effect on the gastrointestinal mucosa
in 9 out of 10 dogs. Three ml with 90% sorbitol caused irritation in 5 of 10 dogs, possibly because the
compound in high concentration is dehydrating to exposed tissue. The observations make clear that
a semi-moist food with 12% sorbitol does not have a gastrointestinal irritant effect.
1. Beynen AC. Sorbaat en sorbitol in petfoods. Petfood Magazine 2019; Nr 2: 24-25.
2. Bone DP. Soft dry pet food product and process. United States Patent 4,039,689 (August 2, 1977).
3. Commission. List of the authorised additives in feedstuffs (1) published in application of Article 9t
(b) of Council Directive 70/524/EEC concerning additives in feedingstuffs (2004/C 50/01). O J EU
(25.2.2004) C 50/1.
4. Commission Regulation (EU) 2017/1017 of 15 June 2017 amending Regulation (EU) No 68/2013 on
the Catalogue of feed materials. O J EU (21.6.217) L 159/48.
5. Better nutrition ingredients - Petco.
6. EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP). Scientific
opinion on the safety and efficacy of potassium sorbate for dogs and cats. EFSA J 2012; 10(6): 2735.
7. Brunner U. Some antifungal properties of sorbic acid extracted from berries of rowan (Sorbus
aucuparia). J Biol Education 1985; 19: 41-47.
8. About potassium sorbate (naturally sourced) I PuraVedaOrganics.
9. Yao CK, Tan H-L, Van Langenberg DR, Barrett JS, Rose R, Liels K, Gibson PR, Muir JG. Dietary
sorbitol and mannitol: food content and distinct absorption patterns between healthy individuals
and patients with irritable bowel syndrome. J Human Nutr Diet 2013. doi:10.1111/jhn.12144
10. Fragua V, Barroeta AC, Manzanilla EG, Codony R, Villaverde C. Evaluation of the use of esterified
fatty acid oils enriched in medium-chain fatty acids in weight loss diets for dogs. J Anim Physiol Anim
Nutr 2015; 99 (Suppl 1): 48-59.
11. Deuel Jr HJ, Calbert CE, Anisfeld L, McKeehan H, Blunden HD. Sorbic acid as fungistatic agent for
foods. II. Metabolism of α,β-unsaturated fatty acids with emphasis on sorbic acid. Food Res 1954;
19: 13-19.
12. Wick AN, Almen MC, Joseph L. The metabolism of sorbitol. J Am Pharm Assoc 1951; 40: 542-544.
13. Knapp BK, Parsons CM, Swanson KS, Fahey Jr GC. Physiological responses to novel carbohydrates
as assessed using canine and avian models. J Agric Food Chem 2008; 56: 7999-8006.
14. Todd WR, Myers J, West ES. On the metabolism of sorbitol and mannitol. J Biol Chem 1939; 127:
15. LSRO (The Life Sciences Research Office). Evaluation of the health aspects of sorbic acid and its
salts as food ingredients. Contract No. FDA 223-75-2004 (SCOGS-57), 1975.
16. Deuel Jr HJ, Alfin-Slater R, Weil CS, Smyth Jr HF. Sorbic acid as fungistatic agent for foods. I.
Harmlessness of sorbic acid as a dietary component. Food Res 1954; 19: 1-12.
17. Bedford PG, Clarke EG. A preliminary study of the suitability of sorbic acid for use as a
preservative in cat food preparations. Veterinary Record 1973; 92: 55.
18. West ES, Burget GE. Sorbitol as diuretic. Proc Soc Exp Biol 1936; 35: 105-107.
19. LSRO (The Life Sciences Research Office). Health aspects of sugar alcohols and lactose. Contract
No. FDA 223-83-2020, 1986.
20. Staples R, Misher A, Wardell Jr J. Gastrointestinal irritant effect of glycerin as compared with
sorbitol and propylene glycol in rats and dogs. J Pharm Sci 1967; 56: 398-400.
... The ingredient composition was 12% rice (dehulled), 31% maize, 19% fish meal, 10% soybean meal, 10% wheat, 8% brewers yeast, 8% soybean oil, 1% dicalcium phosphate, 0.5% sodium chloride, 0.2% multi-vitamins, 0.2% minerals, 0.1% potassium sorbate. The latter compound is used as a preservative with anti-microbial activity (34). ...
Full-text available
Malondialdehyde in petfood MDA (malondialdehyde) results from oxidation of polyunsaturated fatty acids in foods during heat treatment and storage. MDA can also be formed in the body of humans and animals. Ingested and body-derived MDA may react with cellular proteins. The reaction products are considered harmful, but there is no solid evidence for a cause-and-effect relationship between MDA and disease. At low MDA intakes, body cells likely balance damage and repair of proteins (Notes 1-3). MDA amounts in petfood have been assessed by chemical analysis and calculation. The outcomes show wide variation, which may be due to differences in method of analysis, food composition and storage temperature and duration. Due to wide distribution of reported MDA contents in petfood, a reliable estimate of the maximum amount cannot be made, but it is most likely (much) higher than 1 mg/kg dietary dry matter, or per kg of the food's residue after removal of its moisture. In rats, it has been demonstrated that about 65% of ingested MDA is converted into carbon dioxide, which goes along with water forming. About 13% is excreted in urine as unchanged MDA and products of reactions between MDA and proteins. A rat study indicates that MDA in food plus drinking water, at a level equal to 3.6 mg/kg dietary dry matter, causes liver and kidney damage. The design of the study does not permit to deduce the safe upper level of MDA in the diet. The available data on MDA contents in petfood are divergent and those on toxicity are sparse, and without identification of the safe intake level. The designated low-end amount of MDA in petfood is indeed poorly substantiated, but the reported, toxic level of MDA is near that amount. Thus, the presence of MDA in petfood is worrisome. To provide clarity, validated MDA analyses in dog and cat foods are required, and so is assessment of the safe upper limit of MDA.
... There is evidence that orally administered HDE is converted into sorbic acid (hexa-2,4-dienoic acid), a polyunsaturated, medium-chain fatty acid. Sorbic acid enters the hepatic pathway of fatty acid oxidation, yielding ATP, carbon dioxide and water as end products (2). Alternatively, sorbate may be converted into ketone bodies. ...
Full-text available
2,4-Hexadienal in petfood HDE (2,4-hexadienal) is a volatile diene-aldehyde that likely contributes to the flavor effect in various fresh and prepared foodstuffs. As such, HDE is part of complex mixtures of extremely varied compounds that generally include aldehydes, esters, ketones and alcohols. HDE can be formed as a plant metabolite or as a process-induced substance in foodstuffs. As a flavoring agent, synthetic HDE is sometimes added to soft drinks (Note 1). As a process-induced substance in petfood, HDE is probably derived from polyunsaturated fatty acids, including linoleic acid. Since the aldehyde is volatile, lower concentrations could occur in dry dog and cat foods when compared with canned and pouched petfoods. Reports of analysed amounts appear unavailable. It is estimated that the maximum HDE level in petfood is 1 mg/kg dietary dry matter, or per kg of the food's residue after removal of its moisture. No information was found about intestinal absorption and metabolism of ingested HDE. Based on rat studies, it is feasible that the aldehyde group of absorbed HDE is enzymatically converted into a carboxylic group, leading to the formation of sorbic acid, which can be broken down by bodily oxidation. Two-year rodent studies indicate, but do not solidly prove, that HDE intake levels lower than 1 mg HDE/kg dietary dry matter are safe. In the light of the rodent studies on HDE metabolism and toxicity, there is no cause for great concern when it comes to the diene-aldehyde in dog and cat foods. But there are uncertainties. The proposed maximum amount of HDE in petfood is doubtful. Dogs and/or cats might be more sensitive to HDE than rodents. HDE analyses in dry, canned and pouched petfood would be useful, which also goes for assessment of the upper safe limit of dietary HDE. 2,4-Hexadienal 2,4-Hexadienal (HDE, C6H8O) can be described as hexanal with two trans double bonds at positions 2 and 4. The compound can be seen as a polyunsaturated aldehyde. HDE is a volatile organic compound; it has a boiling point of 64 o C, is insoluble in water, colorless and has a citrus odor. HDE is found in various plants and is considered a plant metabolite. HDE can be formed during the processing of foods (see below). Synthetic HDE is used as flavoring agent (1, Note 1); it is produced by condensation of acetaldehyde. HDE is also named sorbic aldehyde or sorbaldehyde. Oxidation of HDE is applied in manufacturing sorbic acid (2,4-hexadienoic acid) or sorbate (ionized form), which is frequently used as preservative in dry petfoods. It was concluded earlier (2), as based on available toxicological and metabolic data, that practical application of sorbate in commercial, complete dog and cat foods is safe. Formation and pathways It is likely that HDE is formed from polyunsaturated fatty acids in chicken and beef fat during heat treatment in the presence of oxygen, but it seems that high temperature and long duration are
Esterified fatty acid oils (EAOs) are obtained from esterification of vegetable acid oils with glycerol. These fat sources have the same fatty acid (FA) composition as their respective native oils but new chemical properties. Several studies have confirmed the potential of medium-chain fatty acids (MCFA) to reduce fat mass (FM) in humans and rodents. This study investigates the use of EAOs with different MCFA proportions on food preferences, digestibility and weight loss management in dogs. A basal diet was supplemented with 8% of three different fat sources: C0: soya bean-canola EAO, C20: soya bean-canola (80%) coconut (20%) EAO and C40: soya bean-canola (60%) coconut (40%) EAO. Food preference of these EAOs was tested using a two-pan preference test. Dogs presented a higher daily food intake of C20 and C40 compared to C0 (C20: 155 ± 18.6 g vs. C0: 17 ± 7.0 g, p < 0.001; C40: 117 ± 13.9 g vs. C0: 28 ± 10.5 g, p < 0.05 respectively). Also, the digestibility of the three experimental diets was tested. C20 and C40 showed higher ether extract, total FA and saturated FA digestibilities (p < 0.05) than C0 diet. Lastly, the three diets were investigated in a 14-week weight loss study, following 16 weeks of ad libitum feeding to induce overweight condition. Body weight (BW) reduction was lower (C0: 20.1 ± 2.32%, C20: 14.6 ± 1.43% and C40: 15.7 ± 1.23%, p < 0.05) and FM was higher (FM, 18.7 ± 3.42%, 27.9 ± 3.90% and 28.2 ± 2.88% for C0, C20 and C40, respectively, p < 0.05) for diets C20 and C40 than for C0. Feeding diets with MCFA at these inclusion levels to experimentally overweight dogs during 14 weeks do not result in faster weight loss compared to unsaturated long-chain FA. Journal of Animal Physiology and Animal Nutrition © 2015 Blackwell Verlag GmbH.
During the last 15 years sorbic acid has become widely used as a food preservative. As sorbic acid is readily available, it can be used in a number of experiments involving the use of microorganisms. These investigations can be carried out with purified sorbic acid or with raw sorbic acid extracted from rowan berries. Extracts may be prepared from fresh berries or dried berries (Fructus sorbi) purchased in pharmacies. These extracts are suitably treated with potassium hydroxide. After this treatment they show antifungal properties. Mould growth on bread and on marmalade as well as mould and yeast growth on grape-agar are inhibited. Further purification and UV examination proves that the antifungal component of the extract is identical with sorbic acid.
Sorbitol and mannitol are naturally-occurring polyol isomers. Although poor absorption and induction of gastrointestinal symptoms by sorbitol are known, the properties of mannitol are poorly described. We aimed to expand data on food composition of these polyols, and to compare their absorptive capacities and symptom induction in patients with irritable bowel syndrome (IBS) and healthy individuals. Food samples were analysed for sorbitol and mannitol content. The degree of absorption measured by breath hydrogen production and gastrointestinal symptoms (visual analogue scales) was evaluated in a randomised, double-blinded, placebo-controlled study in 21 healthy and 20 IBS subjects after challenges with 10 g of sorbitol, mannitol or glucose. Certain fruits and sugar-free gum contained sorbitol, whereas mannitol content was higher in certain vegetables. Similar proportions of patients with IBS (40%) and healthy subjects (33%) completely absorbed sorbitol, although more so with IBS absorbed mannitol (80% versus 43%; P = 0.02). Breath hydrogen production was similar in both groups after lactulose but was reduced in patients with IBS after both polyols. No difference in mean (SEM) hydrogen production was found in healthy controls after sorbitol [area-under-the-curve: 2766 (591) ppm 4 h(-1) ] or mannitol [2062 (468) ppm 4 h(-1) ] but, in patients with IBS, this was greater after sorbitol [1136 (204) ppm 4 h(-1) ] than mannitol [404 (154) ppm 4 h(-1) ; P = 0.002]. Overall gastrointestinal symptoms increased significantly after both polyols in patients with IBS only, although they were independent of malabsorption of either of the polyols. Increased and discordant absorption of mannitol and sorbitol occurs in patients with IBS compared to that in healthy controls. Polyols induced gastrointestinal symptoms in patients with IBS independently of their absorptive patterns, suggesting that the dietary restriction of polyols may be efficacious.
Effects of glycerin, sorbitol, and propylene glycol on the gastrointestinal mucosa were compared in rats and dogs. At equivalent, undiluted doses (ml./Kg.) in both species glycerin was more irritating than sorbitol, and propylene glycol was the least irritating of the three compounds studied. The types of irritant effects observed were qualitatively similar, and the degree of severity was dose-dependent in both species. Studies in rats showed that irritation produced by any of the three compounds was reduced by dilution of the dose.
The objective was to quantify in vitro digestion, true metabolizable energy (TME(n)) content, glycemic and insulinemic responses, and gastrointestinal tolerance to fructose (Fruc), maltodextrin (Malt), polydextrose (Poly), pullulan (Pull), resistant starch (RS), sorbitol (Sorb), and xanthan gum (Xan). Limited digestion of RS, Poly, and Xan occurred. Fruc, Malt, and Sorb resulted in the highest (P < 0.05) TME(n) values, Pull was intermediate, and RS and Poly were lowest. Malt had the highest (P < 0.05) area under the curve for glucose and insulin in the glycemic tests. Gastrointestinal tolerance was examined for diets containing carbohydrates at either 100 or 200% of the adequate intake (AI) value for dietary fiber. At 100% and 200% AI, Malt, RS, and Sorb resulted in ideal fecal scores, while Pull and Xan resulted in looser stools and Poly resulted in diarrhea. The carbohydrates studied varied widely in physiological outcomes. Certain carbohydrates could potentially benefit large bowel health.
Sorbaat en sorbitol in petfoods
  • A C Beynen
Beynen AC. Sorbaat en sorbitol in petfoods. Petfood Magazine 2019; Nr 2: 24-25.
Soft dry pet food product and process. United States Patent 4
  • D P Bone
Bone DP. Soft dry pet food product and process. United States Patent 4,039,689 (August 2, 1977).