Food Safety

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Food Safety Toxicology (3)
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Antinutritives

• Antinutritives can also cause toxic effects by
• by causing nutritional deficiencies or
• by 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.

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1. type A substances primarily interfering with
the digestion of proteins or the absorption and
utilization of amino acids? antiproteins2. type
B substances interfering with the absorption or
metabolic utilization of minerals ?
antiminerals3. type C substances that
inactivate or destroy vitamins or otherwise
increase the need for vitamins ? antivitamins
Type of Antinutritives
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1. 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
  115C or 40 min at 107 to 108C
• Prior soaking in water for 12 to 24 h makes the
  heat treatment more effective.
• Example Boiling at 100C for 15 to 30 min is
  sufficient to improve the nutritional value of
  soaked soybeans.

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Continued.

• heat resistant
• Pasteurization for 40 sec at 72C destroys only
  3 to 4, heating at 85C for 3 sec destroy 44 to
  55,
• heating at 95C for 1 hr destroy 73 of the
  inhibitor.
• Ex trypsin inhibitor in milk, chymotrypsin
  inhibitor in potatoes

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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.

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2. Antiminerals

• Substances interfering with the utilization of
  essential minerals
• Source vegetables, fruits, and cereal grains.

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Phytic acid

• Phytic acid, the hexaphosphoric 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, an iron-binding
  protein secreted in the stomach.

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• 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.

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Oxalic acid

• Oxalic acid (HOOCCOOH) 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

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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.

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• 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.
  Carrageenans,
• which are highly indigestible, can cause a
  decrease in nitrogen absorption of about 16.

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Gossypol

• This antinutritive is a yellow pigment present in
  all parts of the cottonplant. 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. lysin)
• gossypol can reduce the availability of food
  proteins and inactivate important enzymes.
• Processing removes 80 to 99 of the gossypol.

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3. 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

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Ascorbic acid oxidase

• is a copper-containing enzyme that mediates
• 1. oxidation of free ascorbic acid ?
  dehydroascorbic acid
• 2. 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 38C.
• Being an enzyme, ascorbic acid oxidase can be
  inhibited effectively by blanching of fruits and
  vegetables.

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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

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• 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.

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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

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Effect processing on antrinutritional content
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Food Chemistry. Volume 58, Issues 1-2,
January-February 1997, Pages 59-68

• Effect of processing methods on nutrients and
  anti-nutritional factors in cowpea
• N. Wanga, , M. J. Lewisa, J. G. Brennana and A.
  Westbyb
• a Department of Food Science and Technology,
  University of Reading, Whiteknights, Reading RG6
  6AP, U.K.b Natural Resources Institute, Central
  Avenue, Chatham Maritime, Chatham, Kent M E4 4TB,
  U.K.
• The combined effects of soaking, water and steam
  blanching on the nutrients, oligosaccharides and
  trypsin inhibitor activity (TIA) in cowpea were
  investigated. The combination of soaking and
  steam-blanching had less effect on losses of
  nutrients than did soaking and water-blanching.
  Steam blanching resulted in higher reduction in
  TIA than water blanching. However, water
  blanching reduced more oligosaccharides in cowpea
  than steam blanching did. The effect of soaking
  on starch gelatinization was not significant
  during water-blanching. However, the influence of
  soaking on starch gelatinization was significant
  when it was combined with steam-blanching

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Food ChemistryVolume 88, Issue 1, November 2004,
Pages 129-134

• Changes in sorghum enzyme inhibitors, phytic
  acid, tannins and in vitro protein digestibility
  occurring during Khamir (local bread)
  fermentation
• Magdi A. Osman
• Food Science and Nutrition Department, College of
  Agriculture, King Saud University, P.O. Box 2460,
  Riyadh 11451, Saudi Arabia
• Abstract
• Effects of traditional fermentation on enzyme
  inhibitors, phytic acid, tannin content and in
  vitro digestibility of three local sorghum
  varieties were investigated. During a 24 h
  fermentation, enzyme inhibitory activities were
  significantly decreased. Trypsin inhibitory
  activity was reduced by 58, 43 and 31 in
  Hamra, Shahla and Baidha, respectively, whereas
  amylase inhibitory activity was reduced by 74,
  75 and in the three varieties after a 24 h
  fermentation. Phytic acid contents of the three
  varieties were markedly reduced as a result of
  fermentation. Tannin content of Hamra, Shahla and
  Baidha were significantly reduced by,
  respectively, 31, 15 and 35 after
  fermentation. Fermentation significantly improved
  the in vitro digestibility of sorghum proteins.