Anti-nutritional factors and toxins in food

presented by

• Krishnegowda ks ,• FST\2014\015,• M.Sc. food technology,

Anti-nutritional factors

Compounds or substances which act to reduce nutrient intake, digestion, absorption and utilization and may produce other adverse effects are referred to as anti-nutrients or anti-nutritional factors.

Secondary plant metabolites, also referred to as anti-nutritional factors (ANFs), cause depressions in growth performance and animal health due to a variety of mechanisms including reducing protein digestibility, binding to various nutrients or damaging the intestinal wall, thereby lowering digestive efficiency

Anti-nutritives can also cause toxic effects by

causing nutritional deficiencies. interference with the functioning and

utilization of nutrients.Antinutritives can interfere with food

components before intake, during digestion in the gastrointestinal tract, and after absorption in the body

1. type A: substances primarily interfering with the digestion of proteins or the absorption and utilization of amino acids antiproteins

2. type B: substances interfering with the absorption or metabolic utilization of minerals antiminerals

3. type C: substances that inactivate or destroy vitamins or otherwise increase the need for vitamins antivitamins

Type of Antinutritives

Antiproteins

Protease inhibitor proteins which inhibit proteolytic enzymes by binding to the active sites of the enzymes.

Source: many plants (soybean, potatoes), and in a few animal tissues, eggs

Stability: heat labile : Autoclaving soybeans for 20 min at 115°C or 40 min at 107 to 108°CPrior soaking in water for 12 to 24 h makes the heat treatment more effective. Example: Boiling at 100°C for 15 to 30 min is sufficient to improve the nutritional value of soaked soybeans.

Continued….heat resistant: Pasteurization for 40 sec at 72°C destroys only 3 to 4%, heating at 85°C for 3 sec destroy 44 to 55%, heating at 95°C for 1 hr destroy 73% of the inhibitor.

Ex: trypsin inhibitor in milk, chymotrypsin inhibitor in potatoes

Lectins Lectins is proteins that have highly specific binding sites

for carbohydrates.The majority of the lectins are glycoproteins.

Source: plants (legumes such as peanut, soybean, etc), potato, banana, mango, and wheat germ.

Mechanism: disrupt small intestinal metabolism and damage small intestinal villi via the ability of lectins to bind with brush border surfaces in the distal part of small intestine.

Reduction: Heat processing can reduce the toxicity of lectins, low temperature or insufficient cooking may not completely eliminate their toxicity, as some plant lectins are resistant to heat.

Antiminerals

Substances interfering with the utilization of essential minerals.

Source: vegetables, fruits, and cereal grains.It includes; phytic acid, oxalic acid, dietary

fiber and gossypol

Phytic acid Phytic acid, the hexphosphoric ester of myo-inositol, is a strong acid. Phytic acid has been shown to have a negative effect on iron

absorption in humans. Mechanism: Phytic acid prevents the complexation between iron and

gastroferrium, and iron-binding protein secreted in the stomach.

Reduction: phytase activity can reduce the phytic acid level. vit D consumption Calcium absorption is influenced not

only by dietary phytate but also by vitamin D and lipids. If vitamin D is limiting in the diet, calcium absorption will be less efficient and the phytate effect will become more pronounced.

food processing: the activity of phytase drastically reduces the phytate content of dough during bread-making.

Source Phytase: plants (soybeans, cereal grain) Phytase is an enzyme which catalyzes the

dephosphorylation of phytic acid.

Oxalic acid Oxalic acid (HOOC–COOH) is a strong acid, it can

induce toxic as well as antinutritive effects. To humans, it can be acutely toxic (4 to 5 g to induce any toxic effect)

Interference on calcium absorption

Negative effects oxalate/calcium ratio of foods higher than 1 may decrease the calcium availability

Reduction: Consumption of foods rich in calcium, such as dairy products and seafood, and enhanced vitamin D

intake

Dietary fiber food components derived from plant cell walls that are

not digested by the endogenous secretions of the human digestive tract.

Dietary fiber consists of pectic substances, hemicelluloses, plant gums and mucilages, algal polysaccharides, celluloses, and lignin.

dietary fiber is a protective factor against many diseases e.g., colon cancer.

The various types of dietary fiber components have many reactive groups, including –COOH, –HPO3H, –OH, –SO3H and –NH2, to which metals, amino acids, proteins, and even sugars can be bound.

There are different ways of binding to dietary fiber

First, fiber components of many food products act like ion exchangers. Their binding capacity depends on pH and ionic composition of the bowel contents.

Secondly, amino acids and proteins are bound to dietary fiber.

A diet containing 15% cellulose can cause a decrease in nitrogen absorption of as much as 8%. Carrageenan's, which are highly indigestible, can cause a decrease in nitrogen absorption of about 16%.

Gossypol This antinutritive is a yellow pigment present in all

parts of the cotton plant. The highest levels are found in cottonseed.

Gossypol exists in three tautomeric forms: phenolic quinoid tautomer (I), aldehyde (II), and hemiacetal (III).

It forms insoluble chelates with many essential metals, such as iron, and binds to amino acid moieties in proteins (esp. lysine)

gossypol can reduce the availability of food proteins and inactivate important enzymes.

Processing removes 80 to 99% of the gossypol.

Antivitamins

Mechanism: a group of naturally occurring substances which :- can decompose vitamins, - form unabsorbable complexes with them, - interfere with their digestive or metabolic utilization.

ascorbic acid oxidase, antithiamine factors, and antipyridoxine factors

Ascorbic acid oxidase

is a copper-containing enzyme that mediates : 1. oxidation of free ascorbic acid dehydroascorbic acid2. dehydroascorbic acid diketogulonic acid, oxalic acid, and other oxidation products

Source: fruits and vegetables such as cucumbers, pumpkins, lettuce, bananas, tomatoes, potatoes, carrots, and green beans.

The enzyme is active between pH 4, about 38°C.

Being an enzyme, ascorbic acid oxidase can be inhibited effectively by blanching of fruits and vegetables.

Antithiamine factors Antithiamine factors can be distinguished as thiaminases,

tannins, and catechols.

The interaction with vitamin B1 can lead to serious neurotoxic effects as a result of vitamin B1 deficiency

Source: Thiaminases are found in many fish species, freshwater, saltwater species, and in certain species of crab.

Mechanism: interact with vitamin B1 (thiamine), antithiamine factors are enzymes that split thiamine at the methylene linkage

• Reduction: cooking destroys thiaminases in fish and other sources.

• Antithiamine factors can also be of plant origin. Tannins, occurring in a variety of plants, including tea inhibition of growth in animals and for inhibition of digestive enzymes.

• Tannins are a complex of esters and ethers of various carbohydrates. A component of tannins is gallic acid.

Tannins Tannins are a heterogeneous group of broadly

distributed substances of plant origin. Two types of tannins can be distinguished on the basis

of degradation behavior and botanical distribution, namely hydrolyzable tannins and condensed tannins.

The hydrolyzable tannins are gallic, digallic, and ellagic acid esters of glucose or quinic acid.

An example of this group is tannic acid, also known as gallotannic acid, gallotannin. Tannic acid has been reported to cause acute liver injury, i.e., liver necrosis and fatty liver.

TanninsTannins The condensed tannins are flavonoids. They are

polymers of leukoanthocyanidins.

The contribution of the tannins in tea, coffee, and cocoa to the total tannin intake by humans is of particular importance. Tea has the highest tannin content.

Other important sources of tannins are grapes, grape juice, and wines.

A person may easily ingest 1–5g tannins per day.

Antipyridoxine factors A variety of plants and mushrooms contain pyridoxine (a form

of vitamin B6) antagonists The antipyridoxine factors have been identified as hydrazine

derivatives Source: mushroom Reduction: Immediate blanching after cleaning and cutting

can reduce the substance Mechanism: condensation of the hydrazines with the

carbonyl compounds pyridoxal and pyridoxal phosphate — the active form of the vitamin — resulting in the formation of inactive hydrazones

SaponinsSaponins Saponins are a heterogeneous group of naturally occurring

foam-producing triterpene or steroidal glycosides that occur in a wide range of plants, including pulses and oil seeds such as kidney bean, chickpea, soybean, groundnut, and sunflower.

saponins can affect metabolism in a number of ways as follows: erythrocyte haemolysis, reduction of blood and liver cholesterol, depression of growth rate.

Reduction; Saponins from beans can reduced by Sprouting & roasting.

Other antinutrional compounds

Cyanogenic glycosidesCyanogenic glycosides

Some legumes like linseed, lima bean, kidney bean and the red gram contain cyanogenic glycosides from which Hydrogen Cyanide may be released by hydrolysis.

Hydrolysis occurs rapidly when the ground meal is cooked in water and most of the liberated HCN is lost by volatilization.

HCN is very toxic at low concentration to animals. it can cause dysfunction of the central nervous system, respiratory failure and cardiac arrest.

GoitrogensGoitrogens

Goitrogenic substances, which cause enlargement of the thyroid gland, have been found in legumes such as soybean and groundnut.

They have been reported to inhibit the synthesis and secretion of the thyroid hormones.

Goitrogenic effect have been effectively counteracted by iodine supplementation rather heat treatment.

Chlorogenic acid

Sunflower meal contains high levels of chlorogenic acid, a tannin like compound that inhibits activity of digestive enzymes including trypsin, chymotrypsin, amylase and lipase.

chlorogenic acid is a precursor of ortho- Quinone that occur through the action of the plant enzyme polyphenol oxidase.

These compounds then react with the polymerize lysine during processing or in the gut.

it can be controlled by dietary supplementation with methyl donors such as choline and methionine. And readily removed from sunflower seeds using aqueous extraction methods

Main non-nutrient compounds and their main beneficial and adverse effects

compounds Beneficial effects Adverse effects Main source

Protease inhibitors

Anticarcinogenic. growth inhibition. Soya, cereals.

Amylase inhibitors

Potentially therapeutic in diabetes.

- Starch digestion. Cereals

Lectins help in obesity treatment. -nutrient absorption. Beans

Phytates Hypocholesterolaemiceffect.

- Bioavailability of minerals.

Wheat bran, soya

Oxalates Anticarcinogenic. Same as for phytates Spinach,rhubarb.

tannins -risk of hormone related cancer.

Astringent taste, -food intake.

Tea, sorghum,Rapeseed.

Lignans - Risk factors forMenopause.

growth inhibition. Linseed

Saponins Hypocholesterolaemiceffect.

Bitter taste, -food intake.

soybean, groundnut.

Elimination of anti-nutritional substances bytechnological treatments

A number of treatments of food material are able to eliminate some bioactive substances partially including soaking, dry and moist heat treatment, filtration, germination, fermentation and enzymatic treatments.

chemical and physical characteristics determine the choice of appropriate treatment used to eliminate an undesirable compound from food

Heat treatment

Heat processing is widely accepted as an effective means of inactivating the thermo-labile anti-nutritional factors in food material.

This improves protein quality by inactivating anti-physiological factors, particularly trypsin inhibitor and haemagglutinins and by unfolding the protein structure.

Heat treatment process includes boiling, autoclaving, pressure cooking, extrusion cooking, toasting

Cooking (boiling)Cooking (boiling)

Cooking generally inactivates heatsensitive anti-nutritive factors such as trypsin and chymotrypsin inhibitors and volatile compounds.

Cooking for 60 minutes at 1000C was sufficient to inactivate over 90% of the trypsin inhibitor activity in food materials.

Autoclaving Autoclaving cooking under pressure includes the

food materials are autoclaved for 30 minutes at 125oC and 15 Ib pressure, thermo-labile inhibitory substances such as cyanogenic glycosides, saponins, terpenoids and alkaloids could be eliminated from the food materials.

Pressure cooking the food material is cooked under pressure for 30

minutes to remove trypsin inhibitors in food.

microwave treatment

microwave treatment is the heats food by passing microwave radiation through it. Microwave ovens use frequencies  2.45 (GHz) and a wavelength is 12.2 centimetres for 10 minutes to eliminates the trypsin inhibitor and haemagglutinating activity in food.

Extrusion cooking The cooking process takes place within the extruder where

the product produces its own friction and heat due to the pressure generated (10–20 bar). The process can induce both protein denaturation and starch gelatinization, complete inactivation of haemagglutinins in food materials

Soaking Soaking could be one of the processes to remove soluble

antinutritional factors, seeds were soaked in water at 22oC for 18 h to decreases in trypsin inhibitor activity in the food.

Germination (sprouting) Germination has been documented to be an effective

treatment to remove some anti-nutritional factors in legumes by mobilizing secondary metabolic compounds which are thought to function as reserve nutrients.

Germination can lower the phytate content in legume seeds depending upon the type of bean and germinating conditions

Main anti-nutritional factor are eliminated by particular process are

Bioactive substance Commonly used elimination processes

Enzyme inhibitors Heat treatment

Phytic acid Enzymatic degradation, germination, and fermentation

Oxalate Cooking, dehulling

Phenolic compounds Dehulling

Saponins Sprouting

Lectins Heat treatment

Toxins in Foods

Toxin is a poison of biological origin, specifically a protein molecule produced by a plant or animal.

Most toxins in foods are natural and are made by microbes. Toxins from bacteria are large protein molecules,

Mycotoxins from molds are much smaller. Interact with enzymes, cellular receptors Cleave essential protein residues in DNA replication

Toxin Characteristics Toxin Characteristics Non replicative Non infectious Non communicable Non transmittable (human to human) Nonvolatile Colorless Odorless, and Tasteless

main toxins in foods

neurotoxin enterotoxin plant tissue toxin fungal toxin Marine toxins

Botulism Etiological agent: Clostridium botulinum

Reservoir : soil, mud, water, and intestinal tact of animals. Toxins A-G; A,B,E, and F cause human disease.

Toxicity = 1 mg/kg Approximately 500 g is enough to kill the human.

Mechanism of action Blocks release of acetylcholine at neuromuscular junction in the

peripheral and central nervous system.

Incubation period: 2 hours-8 days Symptoms ; nausea, vomiting, diarrhea , abdominal pain,

dry mouth, weakness, constipation

Enterotoxin Etiological agent: Staphylococcus aureus

Reservoir: anterior nares of humans, hands and skin toxins A-F

Toxicity-less than 1 mg can cause illness Incubation period: 1-7 hours (usually 2-4 hours) Symptoms

Sudden onset of nausea, excessive salivation, vomiting, retching, diarrhea, abdominal cramps, dehydration, sweating, weakness.

Ricin ToxinRicin Toxin Etiological agent: Ricinus Communes

Castor bean plant Toxicity-lethal dose = 3-5 mg/kg (ingestion) Mechanism of action

Interferes with protein chain elongation leading to cellular death (cytotoxin)

Incubation period: 1-3 days Symptoms

Early: burning sensation in mouth, nausea, vomiting (blood), abdominal pain, diarrhea.

Death due to severe electrolyte imbalance and fluid loss.

Marine toxinsMarine toxins Very fast acting GI and neurological symptoms

Saxitoxin• Paralytic shellfish poisoning.• Sodium channel blocker.

Ciguatoxin• Reef fish including grouper, snapper and mackerel.• GI, itching, cardiovascular disorder, CNS dysfunction.

Conotoxin• Paralytic poison of Pacific cone snail• Blocks nerve impulse from nerve to muscle

Fungal toxinsFungal species Toxin Foods it may contaminate

Aspergillus flavus aflatoxins corn, peanuts, copra

Aspergillus parasaticus aflatoxins some nuts

Fusarium moniliforme fumonisins corn

Claviceps pupurea ergot alkaloids rye

Penicillium verrucosum ochratoxins barley

Target Organs of Some Mycotoxins

Mycotoxins Target Organ

Aflatoxins liver

Ochratoxins A kidney

Zearalenone Female genital tract

Processing effects on Mycotoxins

Mycotoxins Mycotoxins(toxins produced by molds) are

completely destroyed at their melting point, which is generally at high temperatures:

• 164C (327F) for Zearalenone• 170C (338F) for Rubratoxia.

When roasting peanuts, the toxicity of aflatoxinB1 is reduced by 70%, and that of aflatoxin-B2 by 45%. Thus, heat treatment cannot be considered as a satisfactory means to eliminate Mycotoxins

SummarySummary Non-nutrient compounds are one of the largest group of

secondary metabolites present in the plant kingdom.

This class of natural products has a wide range of biological activity, ranging from beneficial to adverse effects in both plants and animals.

Currently non-nutrient chemicals are substances that are found in food that could potentially affect human health but are not identified as nutrients. Non- nutrients can be found in food as texture and food physic-chemistry, color, taste or smell. 

References

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Bender AE (1983) Hemagglutinins (lectins) in beans. Food Chemistry 11, 309–320.

Cont. Ferguson LR & Harris PJ (1999) Protection against

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Montgomery RD (1969) Cyanogens. In Toxic Constituents of Plant Foodstuffs, pp. 143–157 [IE Liener, editor]. New York: Academic Press

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