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0013 The fermentation must be conducted under

monoseptic conditions, allowing only the specified

culture to grow. To maintain the purity of the culture,

industrial-scale continuous fermentations last up to a

maximum of 6 weeks (1000 h).

Nucleic Acid Content

0014 The nucleic acid content of myco-protein is mostly

ribonucleic acid (RNA). There are potential clinical

problems associated with the consumption of foods

high in RNA, and the maximum intake recommended

by the World Health Organization (WHO) is 2 g per

day. If RNA consumption is too high, blood levels

and urinary excretion of uric acid are increased, and

uric acid crystals may precipitate out in the joints and

soft tissues. This can lead to gout and stones in the

urinary tract.

0015 To remove the excess RNA in myco-protein (on

average c. 10% w/w), the postfermentation broth

(cell suspension) is subjected to a ‘heat shock’ treat-

ment, a procedure specifically developed to reduce

the RNA content. The broth is heated briefly to



C to inactivate enzymes that convert cellular ribo-

nucleic acids into monomer nucleotides, which can

diffuse out of the cell. This process reduces the nucleic

acid content to an acceptable level (< 2% w/w) and

also causes the loss of some protein.

Harvesting

0016 The cell suspension described above is then de-

watered by centrifugation. The harvested cells, col-

lectively known as myco-protein, are paste-like in

consistency and contain around 75% moisture. This

biomass has little, if any, intrinsic flavor or odor.

0017 Quorn production process The harvested hyphae

have a similar morphology to animal muscle cells, i.e.,

they are filamentous with a high length/diameter ratio.

The product assembly process therefore seeks to repro-

duce in Quorn

products the same structural organiza-

tion as that in natural meats, where the muscle cells are

held together by connective tissue. To establish a simi-

lar product texture in Quorn

products, the hyphae

are mixed with binders, flavorings, and other ingredi-

ents, depending on the final product format, and then

heated. This causes the protein binder to gel and hence

‘bind’ the hyphae together.

0018 The resulting structures are similar to those in meat

products, and they also break down in the mouth

during chewing in a manner similar to meat products,

which accounts for their sensory textural properties.

Efficiency of Production

0019 Animal flesh or fish is the most common source of

high-quality protein for humans. However, animals

are inefficient at converting proteinaceous vegetable

material into meat in terms of both energy input

and energy output. The organism described above

converts 1 kg of glucose into 1 kg of wet cell mass,

representing 136 g of pure protein. The efficiency of

conversion is approximately 2:1 on a dry-weight

basis, which is considerably higher than animal con-

version rates. These may be as high as 10:1 for beef,

calculated as dried feed intake against wet carcass

weight. Only part of the animal carcass is eaten,

whereas all of the myco-protein produced can be

consumed.

Properties of Quorn

Products

Acceptability

0020Since the microfilaments in Quorn

myco-protein

are almost identical in size to meat fibrils, Quorn

products have a similar texture and eating quality to

their meat equivalents. Table 1 details some of the

physical characteristics of Quorn

myco-protein.

0021Humans have a long tradition of consuming fungi.

Truffles are an expensive delicacy in the Western

world, and mushrooms and other cap fungi are

eaten across the globe in a variety of forms. Foods

such as Camembert cheese are mold-fermented, and

in the Far East, microfungi are used to ferment soya

beans in the production of miso and tempeh foods. In

southern Africa, a variety of foodstuffs are produced

from fermented cassava.

Safety

0022Myco-protein was safety tested according to the

guidelines of the Protein Advisory Group of the

United Nations. Purified diets were formulated con-

taining myco-protein as the only source of protein at

levels of up to 54% (w/w). Control diets contained

casein in place of myco-protein, and a stock diet

control was included in each trial.

0023The trials were started in 1970 and included tera-

tology, carcinogenicity, toxicity, and multigeneration

studies. Other studies looked at mineral balance,

gastrointestinal effects, and estrogenic effects. There

were no signs of toxicity or carcinogenicity from

feeding myco-protein in any of these trials.

tbl0001Table 1 Physical characteristics of Quorn

myco-protein

Physical characteristics Typical dimensions

Length 400–700 mm

Diameter 3–5 mm

Branch frequency One per 250–300 mm

Data from Marlow Foods, Stokesley, UK.

4074 MYCOPROTEIN

0024 Measurement of serum levels of uric acid was

undertaken in trials conducted at the Massachusetts

Institute of Technology in the USA. Eating 20 g of

myco-protein per day did not significantly increase

serum uric acid levels. Additional daily intake of nu-

cleic acid from the myco-protein did not exceed 2 g.

This confirmed that keeping within this limit main-

tains serum levels of uric acid within the acceptable

range for normal subjects and minimizes the risk of

deposition of uric acid crystals in kidneys, joints, and

other tissues.

0025 Low potential for allergenicity Adverse reactions to

foods have been estimated to occur in 1–4% of the

population. Feeding microbial proteins at a level of

10 g per day is associated with gastrointestinal symp-

toms and skin rashes. To test human tolerance to

myco-protein, over 400 volunteers were involved in

the initial trials conducted at Massachusetts Institute

of Technology in the USA.

0026 In a double-blind crossover trial lasting 67 days,

the myco-protein was baked into experimental bis-

cuits, each containing 5 g of myco-protein (2.7 g of

protein). Identical biscuits were baked for the control

group without myco-protein. One hundred volun-

teers ate two biscuits twice a day, the experimental

biscuits providing 20 g myco-protein per day. After

30 days, subjects ate normal foods for 7 days, and

then the alternative biscuits for the next 30 days.

0027 No subjects had any gastrointestinal reactions or

skin rashes that could be ascribed to ingesting the

experimental material. Myco-protein was well toler-

ated, and the likelihood of adverse reactions was

shown to be no greater than that to most common

foods.

0028 However, trading experience as the distribution of

Quorn

products increased suggested a need for fur-

ther investigation. A small number of reactions had

been reported, which equated to 1.5 complaints for

every million Quorn

products sold. Cross-reactivity

studies showed that Quorn

myco-protein shares

common allergenic determinants with Aspergillus

fumigatus, Cladosporium herbarum, and some with

Alternaria alternata, suggesting the potential for

some mold-allergic patients to react adversely to

myco-protein when it is ingested or inhaled. Screening

of 33 myco-protein production workers over a 2-year

period, for whom any sensitization to myco-protein

would occur via inhalation, suggested that two

workers had increased RAST binding to myco-

protein. However, specific IgE antibody to myco-pro-

tein was not significantly raised in any of the 10

consumers tested who had complained of reactions

to Quorn

products. Overall, these results are re-

assuring as they indicate that the potential for adverse

reactions is extremely low. (See Food Intolerance:

Food Allergies.)

Nutritional Value

0029On a dry-weight basis, myco-protein is 45% protein,

14% fat, and 26% dietary fiber, and on a wet-weight

basis, it is 11% protein, 3% available carbohydrate,

6% fiber, 3% fat, 2% ash, and 75% water. Table 2

shows a comparison of the nutritional value of

Quorn

myco-protein with other protein-rich foods.

0030Quorn products are available as pieces and ‘mince’

for cooking, and also as a range of convenience

products, in which the content of myco-protein may

vary between 50 and 90% myco-protein.

0031Protein content The protein content of myco-

protein is above average for fungal mycelia. However,

myco-protein contains a significant proportion of

nonamino-acid nitrogen, which is in the purine and

pyrimidine bases of the nucleic acids and in the

glucosamine and galactosamine residues of chitin, a

structural component of the cell wall of the filaments

and the form of fiber present in myco-protein. As this

nitrogen is unavailable, it is more practical to express

the protein content as amino-acid nitrogen 6.25

rather than total nitrogen 6.25. Nonamino-acid

nitrogen accounts for about 20–30% of the total

nitrogen. (See Protein: Food Sources.)

0032Net protein utilization (NPU) values before and

after allowance for glucosamine nitrogen reflect the

unavailable nitrogen present in chitin. The usual pro-

cedure for expressing amino acid content in grams per

16 g of total nitrogen underestimates the amino acid

content of myco-protein. Amino acid values will

increase after allowing for nonprotein nitrogen.

0033Although developed as a high-protein food ini-

tially, the protein content of Quorn

myco-protein

on a weight-for-weight basis is less than that of lean

meat, fish, and poultry, but is comparable with egg

(Table 2) and cottage cheese. The NPU is lower

than these foods but higher than wheat and beans

(Table 3). (See Protein: Quality.)

0034Myco-protein provides the complete range of

essential amino acids (Table 4). The limiting amino

acids are methionine and cystine, with a level of 2.9 g

per 100 g of myco-protein. In the UK diet, for

example, threonine is the limiting amino acid overall,

of which Quorn

myco-protein is a good source, in

contrast to most cereals, which have a low content of

lysine and threonine. The relatively high concentra-

tion of these amino acids in myco-protein indicates a

potential value as a supplement to cereal-based diets.

0035Unusually, for a nonanimal food, the protein is of

high biological value and compares favorably with

that of casein. Studies on its biological availability

MYCOPROTEIN 4075

were carried out early in the development stages of

myco-protein.

0036 One way of assessing protein quality is to use the

protein digestibility-corrected amino acid (PDCAA)

scoring method, which is required by the US Food and

Drug Administration (FDA) to be used for most

nutritional labeling purposes. This method compares

the essential amino acid profile of a food, corrected

for digestibility, to the FAO/WHO requirements for

2–5 years olds. This age group is chosen because it has

the most demanding pattern for amino acid use other

than infants. The PDCAA score for myco-protein is

compared with that of other foods in Table 5.

0037Quorn products typically contain between 11 and

15 g protein per 100 g. Most of this protein is from

the myco-protein content, but egg albumen and milk

proteins, added in product manufacture, also contri-

bute some additional protein.

0038Fat content The fat content of myco-protein is ap-

proximately 3%, which is generally lower than that

of most meat and poultry. The cells of the microfungi

do not store fat because of their rapid growth rate,

and the fats present come mainly from the cell

membranes.

0039The content of saturated fat (0.7%) is particularly

low, and no cholesterol is present (Table 6). The ratio

of polyunsaturated to saturated fats (3.5) is also

favorable when compared with braised beef (0.1)

and lean roast chicken meat (0.5). Myco-protein

contains no trans fatty acids and no cholesterol. In

Quorn

products, small quantities of fat may be

added to improve the taste and texture, and these

generally contain between 1.5 and 11 g fat per

100 g. (See Fats: Classification.)

0040Energy content On account of its low fat content,

myco-protein is low in calories. It has fewer calories

Table 2 Comparison of the nutritional value of Quorn

myco-protein with other foods (g per 100 g)

Nutrient Myco-protein

Semi-skimmedmilk Raw egg Braisedbeef Roastchicken Cooked haricot beans

Bakedcod

Energy (kJ) 357 195 617 937 622 406 403

Protein 11.0 3.3 12.5 30.9 24.8 6.6 21.4

Fat: total saturated 3.0 1.6 10.8 11.0 5.4 0.5 1.2

0.7 1.0 3.4 3.1 1.6 0.1 0.5

Fiber 6.0 0.0 0 0 0 6.1 0

Data from Marlow Foods, Stokesley, UK.

Data from Vegetables, Herbs and Spices ^ Fifth Supplement to McCance and Widdowson’s The Composition of Foods. Holland B, Unwin ID and Buss DH (eds),

4th edn. Cambridge: The Royal Society of Chemistry.

All other data from McCance and Widdowson’sThe Composition of Foods (1991) Holland B et al. (eds), 5th edn. Cambridge: The Royal Society of Chemistry.

tbl0003 Table 3 Net protein utilization (NPU) of Quorn

myco-protein

compared with other protein-rich foods

Food NPU

Egg 100

Fish 83

Beef 80

Cows’ milk 75

Myco-protein

Wheat flour 52

Beans 47

Data from Edelman J et al. (1983) Myco-protein – a new food. Nutrition

Abstracts and Reviews in Clinical Nutrition 53: 1–9.

tbl0004 Table 4 Amino acid profile (g per 100 g) of myco-protein

compared to beef

Amino acid FAO/WHO

reference

Myco-protein

Beef

Isoleucine 4.0 5.2 5.0

Leucine 7.0 8.6 7.7

Methionine and cystine 3.5 2.9 3.9

Phenylalanine and tyrosine 6.0 8.9 8.3

Threonine 4.0 5.5 4.3

Tryptophan 1.0 1.6 1.3

Valine 5.0 6.2 5.1

Lysine 5.5 8.3 8.8

Using FAO/WHO (Food and Agriculture Organization, World Health

Organization) (1973) scoring profile.

Data from Marlow Foods, Stokesley, UK.

All other data from McCance and Widdowson’s The Composition of Foods

(1991) Holland B et al. (eds), 5th edn. Cambridge: The Royal Society of

Chemistry.

tbl0005Table 5 Protein digestibility-corrected amino acid score of

myco-protein, compared with other food proteins

Protein source PDCAA score

Myco-protein

0.91

Quorn

pieces

1.0

Roasted chicken (white meat)

1.0

Cooked lentils (canned)

0.52

Calculated from Marlow Foods data, Stokesley, UK.

Calculated from amino acid data in USDA Nutrient Database for Standard

Reference, March 12, 1998 (assumes a digestibility equivalent to beef of

94%).

FAO/WHO Joint Report (1989).

4076 MYCOPROTEIN

than lean chicken (Table 2), making it a useful food

to include in calorie-controlled diets and in weight-

regulating diets. Quorn

products generally have a

significantly lower energy density than their equiva-

lent meat products.

0041 Fiber content In contrast to animal sources of pro-

tein, myco-protein contains nonstarch polysacchar-

ides or dietary fiber (Table 2). The content of fiber

(6%) is higher than that in most vegetables, and the

amount per serving compares favorably with plant

protein foods such as grains, beans, peas, lentils,

nuts, and seeds. (See Dietary Fiber: Properties and

Sources.)

0042 The types of fiber present are chitin (35%) and

b-glucan (65%), which are present in the cell walls.

The fiber is 88% insoluble and 12% soluble.

0043 Vitamins and minerals Myco-protein provides some

minerals and some B vitamins, although it is lacking

in B

(Table 7). The content of iron is approximately

50% that of chicken and 25% that of beef. The iron is

present in an inorganic form, and is therefore not as

bioavailable as heme iron. Myco-protein is rich in

zinc, containing higher levels than meat, making it a

particularly useful source for vegetarians, who gener-

ally tend to have low zinc intakes.

0044 Experimentation has shown that the type of fiber in

myco-protein is unlikely to cause interference with

mineral absorption since it does not contain phytic

acid or phytic salts. Research conducted at the Dunn

Nutrition Laboratory in Cambridge, England, dem-

onstrated that myco-protein had no significant effect

on the absorption of calcium, magnesium, zinc, iron

or phosphorus when compared with a polysacchar-

ide-free diet. (See Vitamins: Overview.)

Known and Potential Functional Health

Effects

Lipid-lowering Effects

0045Studies have demonstrated, under both controlled

and free-living conditions, that myco-protein signifi-

cantly reduces serum total and low-density lipopro-

tein (LDL) cholesterol levels, and that it may raise

high-density lipoprotein (HDL) cholesterol levels.

This suggests that myco-protein consumption has a

beneficial influence on serum lipid variables, in rela-

tion to protection against coronary heart disease. (See

Cholesterol: Factors Determining Blood Cholesterol

Levels; Role of Cholesterol in Heart Disease.)

0046In a metabolic study, nine subjects with mildly

raised blood cholesterol levels ate myco-protein–

based products in place of meat (control diet – eight

subjects) for 3 weeks. The diets were similar in fatty

acid and cholesterol content, and in polyunsaturated:

saturated ratio. The only significant difference was a

29% higher dietary fiber content in the experimental

diet, on account of the high fiber content of the myco-

protein products. The experimental diet produced a

13% decrease in total cholesterol compared with

no change in the controls. LDL cholesterol fell by

9% in the experimental group compared with a

12% increase in controls. HDL cholesterol rose by

11% in the experimental group compared with an

11% decrease in controls.

0047Favorable effects of myco-protein products on

blood lipid levels in subjects with slightly raised

tbl0006 Table 6 Typical fatty acid composition of harvested Quorn

myco-protein

Fattyacid Gramsper100 g of myco-protein

Saturated (S)

Palmitic acid (C16:0) 0.3

Stearic acid (C18:0) 0.1

Total S 0.4

Monounsaturated

Oleic acid (C18:1) 0.3

Total 0.3

Polyunsaturated (P)

Linoleic acid (C18:2) 1.0

a-Linoleic acid (C18:3) 0.4

Total P 1.4

P:S ratio 3.5

Total fatty acids 2.1

Data from Marlow Foods, Stokesley, UK.

tbl0007Table 7 Vitamin and mineral content of myco-protein

compared with chicken (units per 100 g)

Nutrient Myco-protein

Chicken

Vitamins

(mg) 0.01 0.10

(mg) 0.23 0.16

Nicotinic acid (mg) 0.35 11.6

(mg) 0.13 0.42

(mg) 0.00 Trace

Pantothenic acid (mg) 0.25 1.20

Biotin (mg) 15.00 2.00

Folic acid (mg) 10.00 12.00

Minerals (mg)

Calcium 45 10

Phosphorus 254 200

Potassium 100 320

Sodium 4.7 81

Magnesium 45 25

Iron 0.6 0.7

Zinc 10 1.1

Copper 0.5 0.2

Data from Marlow Foods, Stokesley, UK.

Data from McCance and Widdowson’s The Composition of Foods (1991)

Holland B et al. (eds), 5th edn. UK: The Royal Society of Chemistry.

MYCOPROTEIN 4077

serum cholesterol concentrations have been con-

firmed in free-living subjects over an 8-week study

period. The experimental group ate biscuits contain-

ing myco-protein, and the control group ate a

nutrient-balanced biscuit without myco-protein.

Total cholesterol was reduced by 0.46 mmol l

1

and

LDL cholesterol by 0.35 mmol l

1

in the control

group, compared with reductions of 0.95 mmol l

1

and 0.84 mmol l

1

in the myco-protein group, re-

spectively.

0048 This suggests that myco-protein has a beneficial

effect on dyslipidemia and may be a useful dietary

means of improving unfavorable blood lipid profiles.

A potential mechanism for this effect is likely

to involve the high dietary fiber content of myco-

protein.

Blood Glucose Regulation

0049 Myco-protein has also been investigated for poten-

tially beneficial effects on blood glucose and insulin

levels, which may benefit diabetics. A study consist-

ing of two single-meals in a crossover design investi-

gated the effects of myco-protein on acute glycemia

and insulinemia in 19 healthy individuals. Glycemia

was significantly reduced after the meal containing

myco-protein (13% at 60 min) compared with the

control meal. Insulinemia was also significantly re-

duced in the experimental group (19% at 30 min and

36% at 60 min) compared with the control.

0050 These preliminary data suggest a potentially bene-

ficial effect of myco-protein for diabetics, although

further studies are needed before firm conclusions can

be drawn. However the high fiber and low saturated

fat content of myco-protein makes it a suitable com-

ponent of the diabetic diet for other reasons.

Satiety

0051 Several studies have suggested that myco-protein may

help to induce feelings of satiety and to reduce hunger

and calorie intake at subsequent meals following

myco-protein consumption.

0052 In a study (two 3-day study periods), 13 female

subjects, all nonrestrained eaters, ate either an iso-

energetic meal containing myco-protein or chicken.

Energy intake was significantly reduced on the day of

the study (by 24%) and the following day (by 16.5%)

in those consuming the myco-protein meal compared

with the chicken meal. In a further crossover design

study, 18 male and female subjects ate an isocaloric

lunch containing either myco-protein-based products

or chicken, which were similar apart from their diet-

ary fiber content (11 g vs. 3 g, respectively). At the

evening ad libitum test meal, the energy intake was

reduced by 18% in those who had eaten the myco-

protein product-based lunch compared with the

chicken-based lunch. These studies suggest that

myco-protein may play a useful role in weight-

reducing diets.

Other Potential Health Effects

0053Myco-protein has a number of other attributes that

may produce beneficial health effects, and these

warrant scientific investigation.

0054Provision of a-linolenic acid Myco-protein is a

useful source of a-linolenic acid (ALA), an essential

fatty acid belonging to the n-3 family. ALA is a pre-

cursor of the very-long-chain n-3 eicosapentaenoic

(EPA) and docosahexaenoic acids (DHA) in the

body. EPA and DHA are associated with protection

against coronary heart disease through antithrombo-

tic effects in addition to other potential mechanisms.

Research suggests a protective effect of ALA itself

against CHD, through lowering blood cholesterol

concentrations, and beneficial effects on hemostatic

factors and heart arrhythmias.

0055Provision of b-glucans The sources of dietary fiber

in Quorn

myco-protein are chitin (35%) and

b-glucan (65%). b-Glucan occurs in three main

forms, characterized by linkages that are designated

as b 1–3, b 1–4andb 1–6 linked. Myco-protein

contains 16% b 1–3 and b 1–6 glucans on a dry-

weight basis, such that a typical Quorn

product

delivers 2–3gofb glucans per serving. b 1–4 Glucans

are present in certain cereal products such as oats,

and are associated with lowering blood lipids for

which an FDA-approved health claim is permitted.

There is less evidence for beneficial effects of b 1–3

and b 1–6 glucans, but reports to date have suggested

possible immune-stimulating properties and a choles-

terol-lowering effect from these forms of b-glucans

present in yeast.

0056Provision of chitin Chitin is also being investigated

for potential cholesterol-lowering effects. Chitin is a

type of dietary fiber that is found in mushrooms,

fungi, and yeast, as well as in the exoskeleton of

insects and in the hard shells of shellfish. Myco-

protein contains 8% chitin on a dry-weight basis

with a typical serving of a Quorn

product providing

1–1.5 g of chitin.

0057Provision of prebiotics b-Glucan and chitin are both

being investigated as potential prebiotics, which can

be defined as ‘nondigestible food ingredients that

beneficially affect the host by selectively stimulating

the growth and activity of a limited number of

4078 MYCOPROTEIN

bacteria in the colon that have the potential to im-

prove health.’

0058 Provision of glucosamine Research suggests a

potential role for glucosamine in the alleviation of

joint pain arising from osteoarthritis. Free glucosa-

mine is not present in any food sources, but polymeric

glucosamine is present in chitin. Myco-protein there-

fore contains 8% glucosamine in polymeric form

(chitin). There is preliminary evidence that polymeric

glucosamine may also have a beneficial role, as it can

potentially provide sustained release of glucosamine,

but this requires further investigation.

Potential of Myco-protein

0059 Though originally researched and developed as a

high-protein food, the predicted protein gap did not

materialize. However, the ever-changing climate of

consumer demands for food products meant that

the Quorn

range of products could be successfully

marketed in a climate where demand for acceptable

meat-alternatives was growing. This was a response

to an increasing emphasis on healthy eating, for

which, in the 1980s, the context was on removing

elements from the diet considered to be ‘bad’ for

health (Table 8).

0060 However, as we have entered the new millennium,

and the role of food has developed further, there has

been a shift in emphasis towards eating products

that are positively good for health (Table 8). Within

the context of this focus on the functional properties

of foods beyond their nutritional value (so-called

‘functional foods’), Quorn

products would appear

to potentially have a number of positive attributes

that may be of functional value in this context, and

these warrant further investigation.

See also: Amino Acids: Properties and Occurrence; Fats:

Digestion, Absorption, and Transport; Fatty Acids:

Properties; Food Intolerance: Food Allergies;

Functional Foods; Iron: Properties and Determination;

Lipoproteins; Prebiotics; Probiotics; Protein:

Chemistry; Single-cell Protein: Algae; Yeasts and

Bacteria; Slimming: Slimming Diets; Metabolic

Conseqences of Slimming Diets and Weight Maintenance;

Zinc: Properties and Determination

Further Reading

Anderson C (1974) The growth of micro-fungi on carbohy-

drates. In: Tanenbaum SR and Wang DIC (eds) Single

Cell Protein II, pp. 314–329. Cambridge, MA: MIT

Press.

Edelman J, Fewell A and Solomons GL (1983) Myco-

protein – a new food. Nutrition Abstracts and Reviews

in Clinical Nutrition 53: 1–9.

Tee RD, Gordan DJ, Welch JA and Newman Taylor AJ

(1993) Investigation of possible adverse allergic reac-

tions to myco-protein (‘Quorn

’). Clinical and Experi-

mental Allergy 23: 257–260.

Trinci APJ (1994) Evolution of the Quorn

myco-protein

fungus, Fusarium graminearum A3/5. Microbiology

140: 2181–2188.

Turnbull WH, Leeds AR and Edwards DG (1990) Effect of

mycoprotein on blood lipids. American Journal of Clin-

ical Nutrition 52: 646–650.

Turnbull WH, Leads AR and Edwards DG (1992)

Mycoprotein reduces blood lipids in free-living

subjects. American Journal of Clinical Nutrition 55:

415–419.

Turnbull WH and Ward T (1995) Mycoprotein reduces

glycemia and insulinemia when taken with an oral-

glucose-tolerance test. American Journal of Clinical

Nutrition 61: 135–140.

Turnbull WH, Walton J and Leads AR (1993) Acute effects

of myco-protein on subsequent energy intake and appe-

tite variables. American Journal of Clinical Nutrition 58:

507–512.

tbl0008 Table 8 The developing role of food

Time period Context

Early to mid-1900s Focus on adequate vitamin intakes to cure

deficiency diseases

1960s–1990s Eat less of what is bad for you

1990s Eat more of what is nutritionally good for you

2000s Foods that are positively good for health

beyond their nutrient content

MYCOPROTEIN 4079

MYCOTOXINS

Contents

Classifications

Occurrence and Determination

Toxicology

Classifications

L B Bullerman, University of Nebraska-Lincoln,

Lincoln, NE, USA

Introduction

0001 Mycotoxins are a group of structurally diverse,

naturally occurring chemical substances produced

by molds (microfungi). The term ‘mycotoxin’ is de-

rived from the Greek word ‘Mykes’, which means

fungus, and the Latin word ‘toxicum,’ which means

toxin or poison. Thus, mycotoxin literally means

‘fungus toxin’ or ‘fungus poison,’ and its use is re-

stricted to describing the metabolites of microfungi,

as opposed to the toxic principles of certain macro-

fungi, i.e., mushrooms.

Toxicity and Biological Effects of

Mycotoxins

0002 In general, mycotoxins produce a number of adverse

effects in a range of biological systems, including

microorganisms, plants, animals, and humans. The

toxic effects of mycotoxins in humans and animals,

depending upon dose, may include (1) acute toxicity

and death as a result of exposure to high amounts of a

mycotoxin, (2) reduced milk and egg production and

lack of weight gain in food-producing animals from

subchronic exposure, (3) impairment, stimulation, or

suppression of immune functions and reduced resist-

ance to infections from chronic exposures to low

levels of toxins, and (4) tumor formation, cancers,

and other chronic diseases from prolonged exposure

to very low levels of a toxin. In addition, mycotoxins

may be mutagenic, capable of inducing mutations in

susceptible cells and organisms, and teratogenic,

capable of causing deformities in developing embryos.

Other manifestations of mycotoxins that can affect

the food supply in economic terms are reduced growth

rates and increased reproductive problems in food-

producing animals and livestock. (See Carcinogens:

Carcinogenic Substances in Food: Mechanisms;

Mutagens.)

Mycotoxin-producing Molds

0003Most molds that produce the mycotoxins of greater

concern can be found in three main genera, Asper-

gillus, Penicillium,andFusarium. Organisms of the

Aspergillus and Penicillium genera tend to be sapro-

phytic and often attack commodities while in storage,

though some aspergilli can also invade in the field.

The genus Fusarium contains a number of plant

pathogenic species as well as saprophytic types. A

number of factors affect mycotoxin production by

molds, including moisture, relative humidity, tem-

perature, substrate, pH, competitive and associate

growth of other fungi and microorganisms, and stress

on the plant such as drought and damage to seed

coats from hail, insects, and mechanical harvesting

equipment. The major commodities that are suscep-

tible to contamination with mycotoxins include corn

(maize), wheat, barley, peanuts, cottonseed, and some

tree nuts (Table 1). Dairy products, primarily milk,

can become contaminated as a result of feeding

contaminated feed to dairy animals. Cheese made

from contaminated milk will also be contaminated.

(See Cereals: Dietary Importance; Spoilage: Molds in

Spoilage.)

Specific Mycotoxins

Aflatoxins

0004Aflatoxins are produced primarily by some strains

of Aspergillus flavus and most, if not all, strains of

A. parasiticus and A. nomius. There are four main

aflatoxins B

, and G

, plus two additional

aflatoxins that are of significance, M

and M

(Figure 1). The M toxins were first isolated from the

milk of lactating animals fed aflatoxin preparations;

hence the M designation.

0005Aflatoxins are potent liver toxins, in all animals in

which they have been tested, and carcinogens in some

species. Aflatoxin B

is the most toxic of the group.

Effects of aflatoxins in animal tests vary with dose,

length of exposure, species, breed, and diet or nutri-

tional status. These toxins may be lethal when con-

sumed in large doses; sublethal doses produce a

4080 MYCOTOXINS/Classifications

tbl0001 Table 1 Commodities in which mycotoxin contamination has been found and the resulting effects on animals and humans

Mycotoxin Commodities contaminated

Effects of mycotoxins

Affected species Pathological effects

Aflatoxins (B

)

Peanuts, corn (maize), wheat, rice,

cottonseed, copra, nuts, various

foods, milk, eggs, cheese

Birds:

Duckling, turkey poult,

pheasant chick, mature

chicken, quail

Mammals:

Young pigs,

pregnant sows, dog, calf,

mature cattle, sheep, cat,

monkey, human

Hepatotoxicity (liver damage)

Bile-duct hyperplasia

Hemorrhage:

Intestinal tract

Kidneys

Carcinogenesis (liver tumors)

Fish

Laboratory animals

Citrinin Cereal grains (wheat, barley, corn

(maize), rice)

Swine, dog, laboratory animals Nephrotoxicity (tubular

necrosis of kidney)

Porcine nephropathy

Cyclopiazonic acid Corn (maize), peanuts, cheese, kodo

millet

Chicken, turkey, swine, rat,

guinea-pig, human (?)

Muscle necrosis

Intestinal hemorrhage and

edema

Oral lesions

Fumonisins (FB

,FB

)

Corn (maize) Horses and other equidae Equine

leukoencephalomalacia

(ELEM), death

Swine Porcine pulmonary edema

(PPE) and hydrothorax,

death

Rats Liver cancer

Monkey Atherosclerotia,

hypercholesterolemia

Human Possible esophageal cancer

Moniliformin Corn (maize), wheat, triticale, rye,

oats

Chicken Cardiotoxicity myocardial

degeneration

Muscular weakness

Death

Human Possible myocardial

impairment (Keshan

disease)

Plants (corn, tobacco) Necrosis, chlorosis

Ochratoxin A Cereal grains (wheat, barley, oats,

corn (maize), dry beans, moldy

peanuts, cheese, tissues of swine

Swine, dog, duckling, chicken,

rat, human

Nephrotoxicity (tubular

necrosis of kidney)

Porcine nephropathy

Mild liver damage

Enteritis

Teratogenesis

Carcinogenesis (kidney

tumors)

Patulin Moldy feed, rotten apples, apple juice,

wheat straw residue

Birds:

Chicken, chicken embryo,

quai

Edema:

Brain

Lungs

Mammals:

Cat, cattle, mouse, rabbit, rat

Hemorrhage:

Lungs

Others:

Brine shrimp, guppy,

zebra fish larvae

Capillary damage:

Liver

Spleen

Kidney

Paralysis of motor nerves

Convulsions

Carcinogenesis

Antibiotic

Continued

MYCOTOXINS/Classifications 4081

chronic toxicity, and low levels of chronic exposure

result in cancers, primarily liver cancer in a number of

animal species. In general, young animals of any

species are more susceptible to the acute toxic effects

of aflatoxins than are older animals of the same

species. Susceptibility also varies between species.

Of all the mycotoxins, the aflatoxins are of greatest

concern because they are highly toxic and potently

carcinogenic. Mold growth and aflatoxin production

are favored by warm temperatures and high humidity,

typical of tropical and subtropical regions. (See Afla-

toxins.)

Sterigmatocystin

0006 Sterigmatocystin is produced by several species of

Aspergillus, Penicillium luteum, and a Bipolaris

species. Chemically, sterigmatocystin resembles afla-

toxins and is thought to be a precursor in the

biosynthesis of aflatoxin. The acute toxicity of

sterigmatocystin is low, and the main concern is that

it is carcinogenic, about one-tenth as potent a car-

cinogen as aflatoxin B

. Sterigmatocystin has been

detected at lower levels in green coffee, moldy

wheat, and rind of hard Dutch cheese.

Ochratoxins

0007Ochratoxins are a group of related compounds that

are produced by Aspergillus ochraceus and related

species, Aspergillus niger, as well as Penicillium ver-

rucosum and certain other Penicillium species. The

main mycotoxin in this group, ochratoxin A, is a

potent toxin that causes kidney damage in rats, dogs

and swine (Figure 2). Ochratoxin is thought to be

involved in a disease of swine known as porcine

nephropathy, which has been associated with the

feeding of moldy barley. Ochratoxin has also been

Mycotoxin Commodities contaminated

Effects of mycotoxins

Affected species Pathological effects

Penicillic acid Stored corn (maize), cereal grains,

dried beans, moldy tobacco

Mouse, rat, chicken embryo,

quail, brine shrimp

Liver damage (fatty liver, cell

necrosis)

Kidney damage

Digitalis-like action on heart

Dilated blood vessels

Antidiuretic

Edema in rabbit skin

Carcinogenesis

Antibiotic

Penitrem Moldy cream cheese, English walnuts,

hamburger bun, beer

Dog, mouse, human Tremors, death,

incoordination, bloody

diarrhea

Sterigmatocystin Green coffee, moldy wheat, Dutch

cheeses

Mouse, rat Carcinogenesis

Hepatotoxin

Trichothecenes (T-2 toxin,

diacetoxyscirpenol,

neosolaniol, nivalenol,

diacetylnivalenol,

deoxynivalenol, HT-2

toxin, fusarenon X)

Corn (maize), wheat, commercial

cattle feed, mixed feed

Swine, cattle, chicken, turkey,

horse, rat, dog, mouse, cat,

human

Digestive disorders (emesis,

diarrhea, refusal to eat)

Hemorrhage (stomach, heart,

intestines, lungs, bladder,

kidney)

Edema

Oral lesions

Dermatitis

Blood disorders (leucopenia)

Food-borne illness (nausea,

vomiting, abdominal pain,

diarrhea)

Immune disfunction

(suppression and

stimulation)

Zearalenone Corn (maize), moldy hay,

pelleted commercial feed

Swine, dairy cattle, chicken,

turkey, lamb, rat, mouse,

guinea-pig

Estrogenic effects (edema of

vulva, prolapse of vagina,

enlargement of uterus)

Atrophy of testicles

Atrophy of ovaries,

enlargement of mammary

glands

Abortion

Table 1 Continued

4082 MYCOTOXINS/Classifications

reported to be teratogenic to mice, rats and chicken

embryos, and has been suggested as a possible causa-

tive factor, though never proven, in a human disease

known as ‘Balkan endemic nephropathy’.

Citrinin

0008 Citrinin is a yellow-colored compound that is pro-

duced by several Penicillium species as well as Asper-

gillus species (Figure 3). Like ochratoxin A, citrinin

causes kidney damage in laboratory animals similar

to swine nephropathy. Citrinin may be involved with

ochratoxin A in cases of swine nephropathy in Den-

mark. However, the toxicity of citrinin is low com-

pared with ochratoxin, although possible synergistic

activity with ochratoxin A cannot be ruled out.

Patulin

0009Patulin is toxic to many biological systems, including

bacteria, mammalian cell cultures, higher plants, and

animals, but its role in causing animal and human

disease is unclear. Patulin has a lactone structure

and is carcinogenic when injected intradermally into

mice (Figure 4). Patulin is produced by numerous

Penicillium and Aspergillus species and Byssochla-

mys nivea. Penicillium expansum, which commonly

occurs in rotting apples, produces patulin. Patulin is

of some public health concern because of its potential

carcinogenic properties, and because it has been

found in commercial apple juice and other apple

products. Patulin appears to be unstable in grains,

cured meats, and cheese. When administered orally

to rats, patulin showed no toxicity or carcinogenicity.

Penicillic Acid

0010Penicillic acid has a low oral toxicity. The concern

about penicillic acid in foods is based on the fact that

the compound bears structural similarity to known

carcinogens such as patulin, and has in fact been

shown to be carcinogenic to rats when injected sub-

cutaneously (Figure 5). However, the potencies of

penicillic acid and patulin as carcinogens are much

lower than aflatoxins. When given in lethal doses,

penicillic acid caused fatty-liver degeneration in

quail and liver-cell necrosis in mice. Mixtures of peni-

cillic acid with ochratoxin A are synergistic and cause

OCH

Aflatoxin B

OCH

Aflatoxin G

OCH

Aflatoxin M

OCH

Aflatoxin B

OCH

Aflatoxin G

fig0001 Figure 1 Chemical structures of aflatoxins.

COOH

19 20

17 16

1312

fig0002 Figure 2 Chemical structure of ochratoxin A.

HOOC

fig0003 Figure 3 Chemical structure of citrinin.

fig0004Figure 4 Chemical structure of patulin.

CCCC

COOH

OCH

fig0005Figure 5 Chemical structure of penicillic acid as the straight-

chain acid and the lactone configuration.

MYCOTOXINS/Classifications 4083