Mycophagy, fungi in food and drink, food spoilage

biofilm

a biofilm is a community of microorganisms embeddedin a slimy matrix provides protection from external pressures such as dessication antimicrobial agents or disinfectants or the host’s immune system

mycophagy

practice of eating fungi such as mushrooms, fungivorous

fungivory

• synonym for mycophagy

• when organisms consume fungi for nutrition

• birds, mammals, insects, plants, amoeba, gastropods, nematodes, bacteria and other fungi

• ones that only eat fungi are obligate fungivores

fungi poisons

• renowned for their poisons which are believed to have evolved to deter animals from eating them

  • may have pressured the evolution of a squirrel species to diversify diet

mycotoxins

leaf cutter ants

• they farm fungi, they chew the leaves they cut, then integrate them in to a fungi garden

• mutualism because the fungi provides for the ants and the ants feed them

what are edible mushrooms? what do they need to be?

• are the edible fruit bodies of several species of macro fungi

• they do not contain poisonous metabolites although some people may display allergic reactions

• in the US most are agaricus, button and portabella are strains

“exotic” mushrooms in the USA arent… and where are they from

• enoki : flammulina velutipes

• shitake: Lentinula edodes, also grown on logs sometimes

• grown on wood Oyster mushrooms (pleurotus ostreatus) and wood ear (auricularia auricula)

Oyster Mushroom, where can it be grown

• can be on logs, as well as on wheat or rice straw, cotton waste, wood chips and saw dust

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what is a problem cultivating some of the better tasting mushrooms

• THEY ARE MYCORRHIZAL

• have to forage because certain mushrooms like chicken of the wood, or truffle have very specific symbiotic relationships with trees and cant be grown by us

• ephemeral fruiting bodies of persistent underground colonies of myccorrhizal species

• the easier ones are saprophytic and just eat decaying matter

what should the word mushroom refer to only

• limited to the fruiting bodies of basidiomycetes

• truffles are ascomycetes

truffles

• a subterranean ascomycetes with a mycorrhizal association with oak and beech

Corn smut

• diseaseof maize caused by the pathogen Ustilago maydis, or in mexico huitlacoche

  • “mexican truffle”

• imporves the nutritve value of corn, adds lysine and beta glucans which is what oatmeal is know for

fungal fermentations

• the fungal substrate (fungal food) into more digestible and delectable substances

• molds and yeasts have been have been used for processing human foods since antiquity

filamentous fungal food fermentation

• used in many food processes often in complex fermentations with yeasts and bacteria

examples of mold ripened cheeses

• camembert and brie made of Penicillium camberti

• blue cheeses Penicillium roqueforti

blue cheeses

• classification of cow’s milk, sheep’s milk, goat’s milk with penicillium cultures

• veined with blue or blue green mold

• aged in temperature regulated caves

• stilton is english blue cheese

• roquefor is specific to ewe’s milk in french cave

• gorgonzola is an italian blue cheese

camembert ad brie

• a mold penicillium camemberti used on the outside of the cheeses making the crust

asian foods and molds, fermentation

soy sauce, fermented soybean sauce

miso fermented soybean paste

tempeh fermented soybean cake

sufu fermented soybean curd

ang-kak fermented rice

Koji, japanese

• grain or bean overgrown with a mold culture

• koji is a mold started for many different mold fermentations

  • miso, soy sauce, and sake

• Aspergillus oryzae and A. sojae

soy sauce

• two stages of fermentation

• soy beans are soaked and cooked and mixed and roasted with wheat and the fungus Aspergillus oryzae

• first fermentations the fungal enzymes degrade the soy bean wheat mixture in to a paste

• second fermentation is placed in a deep vat and brine and a mixture of yeast and lactobacilli

miso

• soy bean paste

tempeh, why is it a “cake”

• partl cooked whole soybeans and fermentation starter containing Rhizopus oligosporus is mixed in

• the mycelium makes the cake texture

sufu

• fermented tofu inoculated with Actinomucor elegans and it is mold tofu or chinese cheese

Ang-kak, why is it red

• red yeast rice, red koji

• used to color a lot of food products

• Monascus purpureus, is a Mucorales profuce beta carotenes

what is fermentation? What conditions? three types?

partial degradation of sugars or any organic molecule that occurs in the absence of oxygen, different types of fermentation

• alcholic

• lactic acid

• acetic acid

glucose

• central molecule of metabolism in all living things

• sucrose sugar beet and cane only natural plant crop source

• monosaccharide most important for fermentation

polysaccharide

• long chains of monosaccharide units bound together by glycosidic linkages

starch plants

• the main food storage molecule of plants is a polysaccharide called starch

glycogen

• animal and fungal cells long temr storage

glycolysis

• splitting of sugar 6-C sugar to 3-C sugar, pyruvic acid

• oldest biochemical processes to evolve, aerobes and anaerobes

anaerobic conditions

absence of oxygen, lactic acid fermentations or alcohol fermentations, humans don’t do alcohol femrentations only lactic acid

alcoholic ferentation

• pyruvate is converted to CO2, ethanol, and energy after glycolysis produces the pyruvate

• yeasts and other organisms do this

budding yeast

• most fungi reproduce by spores while many yeasts produce buds

fission yeast

• divide but do not bud

• Schizosaccharomyces pombe, tanzanian beer not all yeasts used by humans are Saccharomyces

yeast

• 1,500 described species, but that is only 1% of all described fungal species

• they are not a single taxonomic or phylogenetic grouping they are is either ascomycota or basidiomycota

• unicellular but may become multicellular during life cycle when string of connected bydding cells known as pseudohyphae or false hyphae

• oldest industrial microorganisms

• “foam” “bubble”

true yeasts order

saccharomycetales and are ascomycetes

saccharomyces

• many species used in commercial/ industrial products

• S. cerevisiae is bakers’ yeast

• Saccharomyces pastorianus and S. uvarum are associated with lage rbeer

• S. bayanus strains are associated with wine

• Dekkera/ Brettanomyces is a genus of yeast know for its important role in the production “lambic”

bread

• bread is baked from kneaded dough or batter made from ground cereal grains wheat or water

• leavened or unleavened

leavened bread: yeast fermentation

• ethanol is one product of yeast fermentation but CO2 is the gas trapped in gluten that leavens bread

• saccharomyces cerevisiae is the culture that is use, had to be wild found then maintianed but now there are standarized industrial starters

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leavens

• an agent such as yeast that causes batter or dough to rise especially by fermentation but can be baking powder

• leavens, leavening agents, leaveners

alcholic fermentation

• the conversation of glucose to carbon dioxide and alcohol (ethanol for our purposes) by yeast in the absence of oxygen

• self limiting

  • wine yeast can tolerate 10-15% but brewers only 5-6% but special cared for ones can get up to 21%

enology and viticulture

• process of wine making, the outside portion is viticulture

1. grapes are crushed (skins are broken to yield a mixture of skins, seeds, and juice = must)

2. the must is pressed, juice is saved and the skins and seeds are used as fertilizer

3. juice is fermented

beer

• slightly bitter alcoholic drink made from grain, yellow brown alcoholic drink made from malt and hops

1. cereal grain (wheat, corn, rice, barley) is mixed with water and malt this mixture is called a mash

2. mash is strained it yields an amber liquid called a wort

3. wort is boiled with hops and strained and placed in to fermentation tank where yeast is added

4. Lagers are fermented by yeast that settles on the bottom and ale is on the top

starch and yeast, in the context of beer

• yeast does not have the enzymes to turn starch in to glucose so they have to add a starch degrading enzyme (amylase or diastase) through germinating grains and made to malt powder

malt and malting

• barley or other grain that has been steeped, germinated, and dried used especially for brewing or distilling and vinegar making

• malting is when that powders have the enzymes to turn starch to sugar

saccharomyces cerevisiae - beer context

• top fermenting, ale yeast

  • could be nutritional drink essentially like kombucha in olden times

saccharomyces uvarm - beer context

• bottom fermenting, lager yeast

• leaves greater amount of sugar

cider

• is a fermented alcoholic beverage made from the juice of apples

mead

• fermenting honey with water and in adulterated form with various fruits spices grains or hops

• 8-20% alcoholic content

sake

rice “wine: main diff uses mold rather than malt

made with aspergillus oryzae “koji” mold secretes amylases, rice is then fermented with bacteria and yeast

food spoilage

• anything we can eat microbes can eat too

wheat rust

“polio of agriculture” is a fungal infection is made of Puccinia graminis attacks plant stems, forming lethal, scaly red pustules

methods of preservation can accomplish what

• most methods of preservation do not kill all the resident microbes but rather merely lower the number and make it difficult for them to grow

ancient methods

• drying salting smoking fermentation

• drying in ancient egypt

drying: preservation

• removal of water (dessication) if used with adequate storage no microbial growth will occur

  • sun dried, dehydrated (artificial), condensed (moisture removed from a liquid food), smoked

• sun drying is the oldest method

smoking: food preservation

• dries the food and adds chemical preservatives and flavor from the wood

salting: food preservation

• salting dessicates foods

fermentation as preservation

• acidifies foods, dynamic between fungi and bacteria

• fermentation involves the action of desirable microorganisms, or their enzymes, on food ingredients to make biochemical changes, which cause significant modification of the food

• yeasts can convert to alcohol, active molds in cheese, or most often lactic acid bacteria for things like yoghurt, cheese, pickles

pickling: preserving foods

• vinegar or other acid produced from starches or sugars fermented first to alcohol then the alcohol is oxidized by bacteria to acetic acid

  • wines, beers, ciders frequently have this

canning: food preservation

• Nicolas Appert performed canning with glass vessiles in 1795

• peter durand in england patented the packaging process in 1810

what three groups of mircroorgansism are in food spoilage?

• bacteria

• molds

• yeasts

why are fungi so good at spoiling food?

• extracellular enzymes

• can grow in very little water (water activity) (why dessication or curing)

• can tolerate low pH aka acidic conditions (why fermenting)

water and food spoilage

• water is one of the single most factors infleuncing microbial growth

a_w= water activity refers to the unbound water that is not in food molecules that can support bacterial, yeast, and mold growth

• not moisture, but likely coincided with moisture like bread is about 0.9 a_w

how to change water activity (a_w)

• adding salts or sugars

• corned beef, pepperoni,

• jams and jellies are around 0.8 a_w can get moldy

water activity tolerance bacteria vs fungus

most disease causing bacteria do not grow below 0.94 a_w

where as most mold that spoil food can grow in as low as 0.80 a_w

• there are some below

lowest a_w values permitting growth of spoilage organisms 2 fungi

xerophilic fungi at 0.65

osmophilic yeasts 0.60

fungal xerophiles (osmophiles)

• fungi capable of growth at or below 0.85 a_w water activity

• can spoil foods and feeds, stored commodities sugary product and salted foods

Acidity and food preservation

pH as in hydrogen concentraition pH = -log10[H+]

• many foods are naturally acidic, fermentations make foods more acidic

what condition are molds are more tolerant of than yeasts and bacterias

• pH thats why you see molds on tomatos, fruit, jams, jellies and pickles

acid tolerant v acidophiles

• most organisms are acid tolerant but not acid loving

• acidophiles can thrive under acidic conditions as strong as 2.0

  • mucor racemosus is one

list food spoilage mold genera important in food

• Rhizopus

• Mucor

• Penicillium

• Aspergillius, many many types

• fusarium

• neurospora

• trichothecium

• wallemia

tend to appear in mixtures of different species

Aspergillus genus in food spoilage

• 30 species associated with food spoilage

• tends to be associated with tropical and warm temperate crops

  • oilseeds and nuts

mucor and Rhizopus (zygomycetes)

• typically affect fruits and vegetables since they can only grow at relatively high water activites

• soft rot in fleshy fruits like tomatos

penicillium

• blue green mold common on fruits, cheese, cold mets, bread, cereals, and cereal products

osmophilic yeasts

• grow well in conditions with high concentrations of sugars or salts, high osmotic pressure

• contaminate brines and syrups sometimes wine

film yeasts and food spoilage

grow o the surface of acid products like pickles and sauerkraut

• oxidize the organic acids thereby allowing a succesion of less acid tolerant microorganisms to grow

• candida, debaryomyces, hanseula, Pichia, Trichosporon