9. Mould and mycotoxins Flashcards
Describe Zygomycetes
What does it digest?
What does it produce?
Where is it used?
Invade very quickly on easily digestible substrates: starch, sugars, hemicellulose.
Can’t degrade cellulose.
Saprohytes, plant pathogen.
Common spoilage organism on fruit, vegetables.
Where is Zygomycetes used?
Industrial production of: amylases, lipases, rennin’s, alcohol, and various organic acids – lactic acid, citric acid, succinic acid and oxalic acid.
Production of fermented food: tempeh, sufu.
How is tempeh made? - Rhizopus oligosporus
Rhizopus oligospourus is used to partially digest the proteins of soybeans, which is nutritional enriched (increased digestibility of proteins, higher levels of riboflavin, niacin and B12.
- Soybean are soaked and dehulled
- Soybeans are boiled
- Beans are inoculated with Rhizopus oligosporus by adding piceses of tempeh, use same wrapper as former batch or add spore suspension.
- Beans are wrapped and incubated in RT.
- Tempeh is slices, dipped in salt water and cooked.
How is zygomycetes reproduced?
Both asexual and sexual.
What is hyphae, sporangium, sporomigofor, rhizoid
A hyphae is a long, branching filamentous structure of a fungus, oomycete, or actinobacterium.[1] In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Sporangium - the hat of the hyphae
Sporomigofor is the shaft of the hyphae
Rhizoid is the “rots” of the hyphae.
Describe Mucormycosis (Zygomycosis)
In humans with severe underlaying stressing deceases: metabolic acidosis, immunosuppression, trauma.
Spread via the bloodstream can cause growth in/on skin. Very high mortality when proliferation occurred in the body (70-100%).
Direct provisioning via soil/water with spores infect the severe wounds – natural disasters, accident, war injuries. Tattoos, insect stings, scorpion stings. Common in infections – Rhizopus arrhizus (R. oryzae), mucor sp, Licgthemia sp.
Describe . Deuteromycetes (Fungi imperfecti).
Where can it be found?
How is it reproduced?
Common in air. Ex. Aspergillus life cycle
Hyphal growth -> spore formation -> spores -> spores germination -> hyphal growth.
20 genera: 100 species in food. Ex. Aspergillus, penicillium, fusarium.
Most important food/air contaminants.
Only vegetative reproduction (why they are fungi imperfect).
Growth demands – medium aw 0.75-0.85. Growth media: MEA 2%, CYA, CYA+20%S. You need to mimic the product when you want to insolate them.
Mycotoxin producers, pathogenic.
Describe aspergillus.
Where can it be found?
Common in food spoilage.
20 of 100 species in food air.
20-35 C, 0.75-0.8 aw
mycotoxin producers.
Pathogen (ex A. Fumigatus, A. parasiticus, A. niger)
How does aspergillus look?
Like a dandelion (maskros), with bowlingpins on top.
Hypne bottom, condidphore shaft, vesicle (head), filalid as the thick part of the bowling pin and conodies as the small part of the pin.
The vesicle can look like a sphere, oval or rod.
Describe Aspergillus fumigatus.
Spores in the air.
200 spore/day
immun deficiencies, diabetes, impaired respiratory function is affected.
Spores tiny 2-3 mikrom passes to bronchioles/alveoles.
Thermotolerant mould 37C (50%).
High temp induces stress response that increases virulence.
Discribe pencillium
50 species in food. T: 0-30. aw: 0.8-0.85 many mycotoxin producers. No pathogenic species. Penicillium occurrence: bread, butter, cheese fruit.
Can branch in multiple directions.
Describe ascomycotes
30 species in food. Fungi and yeast. Ex eurotium, emericella. Plantpathogens, saprophytes. Temp 0-35 C, aw 0.8-0.7. Myctoxin producers.
Reproductive with anamorph (asexual) and teleomorph(sexual) reproduction.
Ascospores product ex eurotium sp. Occurrence: bread, nuts, grain.
Give four examples on problem with fungi (4)
- Fungi growing at low aw
Ex. Eurotium spp aw 0.75
EX sweet pastry, confectionary. Spores common in air and food. Slow growth (6 weeks -9 months) Ascospores survives baking. pH 5,5-6,5 > preservatives “ineffective”
. mycotoxins. Hygiene important! More examples Wallemia sebi, Aspergillus penicilloides.
Combination low aw 0.75, low baking temperature and ascospores -> the high suger concentration increases the heat resistance!
- Fungi producing heat tolerant spores.
Ascomycetes commin in soil, air. Ascospores “survive” 85-90 C in 50 min. Growth during storage at 25-30 C. Products: fruit concentrates, juice, dairy products, jam, sweet pastry. Species: Talaromyces sp., Byssochlamys sp., ex Neosartiry fischeri D88=1.4 min. - Fungi tolerating preservatives.
Sorbate, benzoate and propionate. Pencilomyces variotii, trichoderm spp. Problem in: jam, beverage, bread.. Degarding of sorbat to 1,3-pentadiene -> penicillium roqueforti, pencillium glabrum m.fl and yeast Debaryomyces hansenii. Trichoderma on light fat product, lens liquid, p. roque I still beverage. - Fungi growing in MA (low O2-conc)
Spores distributed by air. Common on bake-off bread. Penicillium roquefortii, P. commune. Fusarium oxysporum, F. solani, F. moniliforme, Rhizopus sp. Mucor sp.
Describe problem in production and product because of fungal growth
Dematerializing of raw material and product. Unwanted metabolites: organic acids, enzymes, alchols etc. Volatile compounds. Taste problems. Mycotoxins, heat table ascospores.
Changed production/new products – low fat content, low sugar/salt content, preservatives not wanted, increased imports, extended shelf life, climate change.
What is a mycotoxins?
Toxin produced by fungi. >400 known: 30 found in food.
