Transcript fermentation

Fermented products are:
Fermented products are those whose
production involves the action of
microorganisms or enzymes which
cause desirable biochemical changes
and significant modification to the
food.
Origins of Some Fermented Products
Food
Mushrooms
Soya sauce
Wine
Fermented milk
Cheese
Beer
Bread
Fermented meat
Sourdough bread
Fish sauce
Tea
Approx. year of
introduction
4000 BC
3000 BC
3000 BC
3000 BC
2000 BC
2000 BC
1500 BC
1500 BC
1000 BC
1000 BC
200 BC
Region
China
China, Korea, Japan
North Africa, Europe
Middle East
Middle East
North Africa, China
Egypt, Europe
Middle East
Europe
Southeast Asia, North Africa
China
Fermentation processes:
 Lactic acid
 Alcoholic
 Acetic acid
 Propionic acid
Fermented foods
 Beverages
 Dairy products
 Cereals
 Meat and fish
 Fruits and vegetables
Beverages
Beer
Wine
Sake
Cider
spirits
Dairy products
Cheese
Yoghurt
Kefir
Kurut -dry yoghurt ball
Kumis – alcoholic beverage from
mari’s milk
Cereals
Breads
Rolls
Dosa (fermented crepe made from fermented rice and black
lentils), idli (cakes 2-3 inches in diameter made by steaming
a batter consisting of fermented rice and black lentils), adai
(dosa); lao-chao (rice) , kenkey (sourdough dumpling made or
corn such as sadza or ugali), ogi (fermented cereal porridge)
Injera (flat pancakes made of iron rich teff (grass specie)
flour)
Meat and Fish
Jerky, country ham, salami, pepperoni
pickled meat
Fish sauce, bagoong (mixture fish and brine,
traditionally left to ferment for 10 to 12 months until
it produces bubbles and acquires its characteristic
pungent odor.
Fruits & vegetables
Pickled fruits & vegetables
Olives
Sauerkraut
Contribution of the fermented
foods:
Enrichment of the human diet
 Preservation of substantial amounts of food
 Enrichment of nutritional value of food (vitamins,
proteins, essential amino acids etc]
 Detoxification of food (flatulence-causing
sugars, lectins, phytates etc]
 Decrease the cooking time and fuel requirements

Preservation principle:
To hinder (delay) the growth of
food spoilage microorganisms
Alcoholic fermentation:
Simple sugars
yeasts > ethanol
Saccharomyces cerevisiae
Major Reaction: Glucose to Carbon
Dioxide and Ethanol
Special flavors and aromas of beers arise from minor
biochemical reactions
Yeast
Saccharomyces sp.
Yeasts involve in fermentation
should possess:
 Rapid and relevant carbohydrate
fermentation ability;
 Appropriate flocculation and
sedimentation characteristics;
 Genetic stability;
 Osmotolerance
Yeasts involve in fermentation
should possess:
 Ethanol tolerance
 Ability to produce elevated concentration
of ethanol;
 High cell viability for recycling;
 Temperature tolerance.
Alcoholic fermentation is
affected by:
Oxygen supply
Sugar content
Alcohol content
Temperature
Alcoholic fermentation:
Unlimited oxygen supply
- cell
growth
Limited oxygen supply - alcohol
production
Beer
A diluted solution of ethanol with a
characteristic flavour arising from the
use of malt as predominant source of
carbohydrates and other yeast
nutrients and hops as a source of bitter
components.
Kinds of beer
 Lager -
produced by bottom fermenting yeasts ( Saccharomyces uvarum) .
 Ale -
produced by top fermenting
yeasts ( Saccharomyces cerevisiae)
Production of beer:
Malting
 Mashing
 Boiling of wort with hops
 Fermentation
 Storage

Production of beer
Malt

Made from barley that has been
allowed to germinate.

Germination produces enzymes
that during mashing converts
starch into simpler sugars and
proteins into peptides.

This malt is then used by the
yeast in the fermentation
process.

Before mashing the malt may be
roasted to darken the color and
harden a beer.
barley
Malting (preparation of malt):
Soaking barley grains in water at
10-15 0C
 Germination of barley grains at
16-21 0C for 5-7 days
 Separation germs and sprouts
 Crushing the malt

Mashing (preparation of wort)
 Mixing malt with water
at 38-50 0C
(protein hydrolysis)
 Saccharafication of malt at 65-70 0C
(hydrolysis of starches to simple
sugars)
 Inactivation of enzymes at 75 0C
 Separation of insoluble materials.
Wort
• Brewers' wort commonly has 8-14% total solids.
• 90-92% are carbohydrates: glucose, fructose, maltose,
sucrose, maltotriose.
• Nitrogenous compounds, such as, amino acids.
• Vitamins: biotin, inositol, pantothenic acid, pyridoxine,
and thiamine are present in wort and utilized by
Brewers' yeast.
• Phosphates, chlorides, sulfates and other anions are
present with the cations Na, K, Ca, Mg, Fe, Cu, and Zn.
HOPS
Hops are the flowering portion of the hop vine.
These flowers not only fight off bacterial infections in
the beer, they aid in clarification of the beer, stabilize
the flavor, help retain head, and aid in ones ability to
drink the beer.
Hop oils are produced in the Lupulin glands of the
flower. These oils are non-polar, and can only be
extracted through a short boiling and contribute to the
bitterness of a beer.
Boiling of wort with hops is done to:
 concentrate it
 sterilize it
 inactivate enzymes
 extract soluble substances from hops
 coagulate and precipitate proteins
 contribute antiseptic resins:
humulone, cohumulone, adhumulone.
Fermentation
Fermentation of beer
 Pitching (inoculation)- 1lbs of yeasts per
barrel of wort
 Lager beer is fermented at 7-15 0C
 Ale beer is fermented at 18-22 0C
 Fermentation - 9 days
 At the end of fermentation yeasts are
skimmed (top-fermenting) or are cropped
(bottom-fermenting).
Fermentation of Ales
 Top fermenting-rise to the surface.
 Warmer temps- 60-70F
 More rapid growth
 Create more esters
 Complex and Fruity
 Ales, porters, stouts, and
wheat beers.
Fermentation of Lager
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Bottom fermenting-yeast settle to
the bottom of the fermenter as
fermentation reaches completion.
Colder tempeatures: 47-58F
Slower growth
Crisp and hoppy like a pilsner or
sweet and malty like a Dopplebock.
Examples: Pilsners, Bocks, and
American malt liquors.
Storage and packaging
after fermentation beer is stored (lagered) at 0 C
(several weeks to several months) to remove the
“green” flavors caused by diacetyl and
acetaldehyde which can impact the taste
adversely as humans can taste them at very low
concentrations
 clarified or filtered
 pasteurized at 60 C shortly
 carbonated to CO2 content 0.45-0.52%
 packaged to cans or bottles.

Beer defects (off flavour) may be
due to:
butyric (Clostridium sp.) or lactic acid
fermentation during mashing process.
 Inoculum contaminated with wild yeasts or
lactic acid bacteria.
- Yeasts may produce off flavor.
-Bacteria may produce sour taste and/or
silky turbitidy.

WINES
Products obtained by alcoholic
fermentation of grapes, grape
juices, fruit juices, berries,
rhubarb, honey etc by yeasts.
Wine –definition of terms
Vintage – year grapes are grown and harvested.
 Dry – wine with no sugar after fermentation
 Sweet – wine with small amount of sugar left over
 Body – the weight of wine
 Style – overall impression of wine
 Bouquet – a wine scent that comes from wine
making process
 Aromatic – components of wine scent that comes
from grape itself

Wine – Basic types
Five basic types of wine are:
 Red Wine
 White Wine
 Rose Wine
 Sparkling Wine - carbonated
 Fortified Wine - high alcohol content
– Sherry - Spanish style wine (amber to brown) can be
made sweet or not sweet.
– Port - Sweet red wine originally from Portugal
– Madeira - from Madeira Islands made from cooked
grapes & aged
– Marsala - Italian wine made from concentrated grape
juice.
Kinds of wines
still wines
 sparkling wines
 artificially carbonated wines

Kinds of wines
 Dry vs. sweet wines
 Unfortified vs. fortified wines
 Red vs. white wines
 Grape vs. fruit wines
 Table vs. dessert wines
How wine is made
 Harvesting
 Pressing
--- Sugar/Acid Ratio
Techniques -- Red, White or
Rose?
 Fermentation
 Maturing
 To
bottle
Grape used for production of wine

Varies in grape species and cultivars
• Vitis vinifera, V. labrusca
• Cabernet Sauvignon, Chardonnay, Gamay, Mission, etc. refer to
different varieties or cultivars of the Vitis vinifera
Cabernet Sauvignon
Chardonnay
Gamay
Mission
• Different in compositions (sugar contents, pigmentation, etc.)
• Different climates and soil preference
• Wine quality varies greatly
– Climate factors have important effect on grape quality and maturity
Grape Composition
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Water 70-85% of the juice volume
About 20% sugar
• Simple sugars largest constituent of grapes or must
• Important for S. cerevisiae to produce ethanol
• Glucose (~50%), Fructose (~50%, increase in over-ripened grapes),
sucrose (<1%, in V. labrusca up to 10%)
• Other sugars very low conc.
Sugar content in final product
• “dry”: 0.1%-0.2%
• “sweet” >10g/L
• “very sweet” as much as 100g/L-200g/L
Organic Acids
• Second in content constituent in must
• Very important in wine quality
– Provide low and well buffered pH (3.0-3.5)
– Antimicrobial activities
– Stabilizes anthocyanins (color, antioxidant,
desirable flavor)
– Volatile acids (acetic acid and others) very low
– Fixed acids (malic acid and tartaric acid ~5:1)
important to maintain the right acidity of wine and
anti-spoilage, affected by environmental factors
Nitrogenous Compounds
Total N content in must range from 0.2g/L to
0.4g/L
 Generally adequate for rapid growth of yeast
 Biogenic amines (histamine and tyramine) in
wine (by wine bacteria) can cause adverse
reactions
 Ethyl carbamate potential carcinogen,
concentration increased by heat treatment and
high urea concentration.

Polyphenols
 Polyphenolic compounds naturally
occurring in grapes, some are introduced
later
 Contribute to color, flavor, aroma, mouth
feel to the wine
Production of wine
After harvesting:
The grapes are transported to the
winery where they undergo
destemming and crushing.
 There are a variety of presses that
are used to produce the juice,
which is called “must”.
 The sugar in the wine is used by
the yeast to produce ethyl alcohol
and carbon dioxide gas, thus
making wine.
 The type of yeast can affect
the qualities of the wine as
will other compounds in the
wine - some naturally
occurring and some that are
byproducts of the
winemaking process.

Small Bladder Press
Crusher
Large Rotary Press
Steps involve in fermentation of
wine:
 Preparation of must
(grape juice, crushed
grapes, fruit juice].
 inoculation of must with wine yeasts
(2-5% ].
 aeration of must to encourage the growth
of yeasts and to facilitate the extraction of
pigments from a skin (mixing must twice a
day ].
Steps involve in fermentation of
wine:
Active fermentation:
- red wines 24 -27 0C; 3-5 days;
- white wines 10-21 0C; 7-14 days;
 separation of fermented juice from residue
(pomace);
 placing fermented juice under light CO2 pressure
 secondary fermentation: 21-29 0C, 7-11 days.
 aging of wines.

Differences in making red and white wine
White Wine:
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Grapes for white wine are
harvested and pressed.
The must is fermented in
stainless steel tanks.
Some white wines, such as
Chardonnay, is aged in oak
barrels.
The wine is bottled
Most white wines are not
bottle aged but consumed
with in 3 years of bottling.
However, an exception is
particularly fine wines made
from Chardonnay and
Champagne.

Red Wine:
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Grapes for red wine are
harvested, crushed.
The must is left with the
skins during fermentation to
produce the red color.
Red wine is commonly aged
in oak barrels for 6 to 24
months.
The wine is bottled.
Many red wines are ready to
drink after bottling.
However, some red wines,
such as Cabernet
Sauvignon, will benefit with
some bottle age.
Production of Blush & Sparkling Wines
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Blush Wine:
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Red grapes are harvested
for Rose or Blush wine.
Before fermentation the
must is left with the skin for
a short time.
The must is fermented in
stainless steel tanks.
If a sweet wine is desired
then the fermentation is
stopped before all of the
sugar is consumed.
The wine is bottled
Blush wines are not
commonly bottle
aged but consumed
within 3 years of
bottling.

Champagne (Sparking) Wine:
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Grapes for sparking wine are
harvested and pressed.
It is fermented like a white wine.
More sugar and yeast is added to
the wine.
The wine is bottled.
The additional sugar and yeast
produce carbon dioxide, which
carbonates the wine.
The second fermentation is
stopped.
Most sparkling wines are made to
drink young. But, fine Champagne
will benefit with additional bottle
age.
Production of fortified wine
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Grapes for fortified wines are
harvested like for other wines.
Depending on the type of wine,
the must may be handled in
different ways to intensify the
flavor before and during
fermentation.
Most fortified wines have an
addition of alcohol (brandy) to
stop fermentation and increase
the alcohol content.
Fortified wine maybe aged in
oak barrels before bottling.
Many fortified wines will benefit
with bottle age.
Aging of wine
Once fermentation is complete, the wine
can be transferred to oak barrels for aging
for 6 to 24 months. But, not all wine is oak
aged.
 The barrels are usually made from either
French or American Oak, which give
differing qualities to the wine.
 Some wine is aged in old barrels and some
in new to produce different characteristics,
as well.
 The wine maker will then blend the various
lots of wine to produce a finished wine
ready for bottling.

Active Yeast Cells
Fermentation Tanks
Barrel filling
Barrel aging
Bottling and storage of wine
After the aging of wine is
complete it is transferred to
bottles.
 Most wine is consumed within
three years of bottling.
 But some fine wines gain
added flavor and bouquet with
time in the bottle if it is stored
at 50 to 60 F. But, humidity is
also important so that the
corks do not dry out, which
spoils the wine.
 The wines commonly aged in
the bottle are:
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–
–
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Cabernet Sauvignon (Red)
Pinot Noir (Red)
Chardonnay (White)
Champagne (White Sparkling)
Port
Sherry
Bottles being filled
Bottling line
Large Commercial Cellar
Small in-home cellar
Problem solving
Calculate the % [w/w] of EtOH in wine.
Assume that at fermentation starting
point 30 kg of must contained 26% of
sucrose. The fermentation ceased at
2% concentration of sugar. The yield
of conversion of sugar to ethanol was
94%.
Calculation steps:
C6 H12O6 = 2 C2 H5 OH + 2 C02 
1. Calculate the amount of sugar in must.
M1 = 30 * 0.26 = 7.8 kg
Calculation steps:
2. Calculate the final weight of must (M)
at the end of fermentation process.
M = M0 - M2 + M3
M0 - initial weight of must;
M2 - weight of sugar used during fermentation;
M3- weight of produced alcohol.
Calculation steps:
3. Calculate the weight of sugar in wine.
M4 = M * 0.02
4. Calculate the weight of sugar fermented to alcohol.
M5 = (7.8 - M4 ) * 0.94
M5 = (7.8 - M * 0.02) * 0.94
Calculation steps:
5. Calculate the weight of produced alcohol.
C6 H12O6 = 2 C2 H5 OH + 2 C02 
180
92
M5
M3
--------------------------------M3 = 92 * M5 /180 = 92 * ( 7.8 - M4)*0.94/180 =
92 * ( 7.8 - M * 0.02) * 0.94/180
Calculation steps:
6. Calculate the final weight of wine (M)
M = M0 - M2 + M3
M = 30 - (7.8 – M*0.02)+
+ 92*(7.8 - 0.02*M) *0.94/180
M = 26.22 kg of wine
Calculation steps:
7. Calculate the weight of produced
ethanol.
M3 = 92 * (7.8 - 26.22 *0.02) * 0.94/180
M3 = 3.495 kg of ethanol
Calculation steps:
8. Calculate [ % ; w/w) of ethanol in wine.
[%] = M3/M * 100
[%] = 3.495/26.22 *100
[%] = 13.3%
Factors affecting the wine
spoilage:
 Acidity - the lower the pH the less likely the
wine will spoil. Molds, yeasts, acetic acid
bacteria would not be stopped by any pH
normal to wines: most wines - pH 3.5-4.0;
 Sugar content < 0.1%;
 Ethanol content . 14%
 Temperature - spoilage most rapid at
20-30 oC.
Yeasts of the genera Dekkera
& Brettanomyces
Responsible for the
production of
off-flavours
in wine (known
as “phenolic
taint”, “horse
sweat”,or“Brett
flavour”)
o
I
II
III
R= H  I=p-coumaric acid; II=4-vinylphenol; III=4-ethylphenol
R=OCH3  I=Ferulic acid; II=4-vinylguaiacol; III=4-ethylguaiaco
“Brettanomyces sp. has been identified
in spoilage
from all wine-producing areas of the world”
Fugelsang, K.C. (1997) In Wine Microbiology, Chapman & Hall
Evaluating Wine

Body
• Light, medium, or full? (think about the difference between skim
milk, whole milk, and cream)

Texture
• How does the wine feel in your mouth (e.g. soft, sharp, smooth)?
• If you had to describe the wine as a fabric, what would it be?

Flavor
• What specific components can you taste? It may help to run
through lists of choices.

Balance
• Is the wine overwhelmed by any components (alcohol, acidity,
tannin, fruitiness, sugar)?

Length
• How long do the flavors and aromas linger after swallowing?
Evaluating Wine – Smell (aroma and
bouquet)
• Aerate the wine by swirling it in the glass
• Stick your nose in the glass and inhale
• Aroma traditionally refers to grape-associated smells
• Bouquet refers to other smells (e.g. oak, vanilla, nutty
or buttery)
Aroma Wheel
Evaluating Wine - Taste
• Evaluate the first impression of a wine on your
tongue by taking a sip but don’t swallowing yet
Following this:
• Swirl the wine around in your mouth, draw in some
air
• Evaluate body & texture as well as flavor and balance
• Evaluate the flavors and aromas that last after
swallowing the wine
• Evaluate length of finish (the longer the better) (ie.
How long the flavor last)
Production of ethanol
 Starch pretreatment:
-gelatinization,
-liquefaction,
-saccharification
 Fermentation
 Distillation
Type of whisky
•
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•
•
Malt whisky
Pot still whisky
Grain whisky
Blended whisky
Straight whisky
By location
• Scotch whisky (Scotch)
• Irish whiskey
• Kentucky whiskey (Bourbon)
• Tennessee Whisky
• Canadian whisky
Production of Whisky

Fermentation
• The dried malt (or other
grains) is ground and
soaked in water, dissolving
the sugar and producing
wort
• Yeast is then added, and
the wort is allowed to
ferment, producing wash
or low beer.

Distillation
Distillation - Pot Still
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Heat is applied directly to the pot
containing the fermented wort
Alcohol, water and flavor components
evaporate
The first distillation produces so-called
'low wines', (25-35%)
The second distillation produces the
colourless spirit, collected at about (70%)
Whisky production

Aging
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Bottling
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In new (for Bourbon) or old, charred (Bourbon & Scotch)
or uncharred (Irish Whiskey) oak barrels/casks
Typically causes the brown color to develop over time
0.5 – 2.0% volume evaporates each year of aging (making
long-aged whiskies more expensive to produce)
Mature whisky is usually blended
Water is usually added (to reduce alcohol content)
Chill Filtration
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•
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Whisky is chilled to near 0°C (32°F) and passed through a
fine filter
Removes some of the compounds accumulated during
distillation or aging, prevents the whisky from becoming
hazy when chilled
Can also remove some of the flavor and body from the
whisky
Scotch Whisky (Barley Malt Whisky)
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Distilled at a Scottish distillery
from water and malted barley
Only other whole grains may be
added
Must have an alcoholic strength
of less than 94.8% by volume
Must be matured in Scotland in
charred oak casks for at least
three years (giving it smoky &
earthy overtones)
Most single malts are aged for
at least 8 years
Must not contain any added
substance other than water and
caramel colour
Typically distilled twice
Irish Whisky (Barley Malt Whisky)
Similar to Scotch whisky in
ingredients & production
 Typically distilled 3 times
 Aged in uncharred barrels
(unlike Scotch or Bourbon)
 Pure pot still whisky

Canadian Whisky
Must be barrel aged at
least three years
 Most are blended
multi-grain whiskies
 Traditionally called
“rye whisky," contains
proprietary blends of
corn, barley, and rye.

Lactic Acid Bacteria

The lactic acid bacteria can be divided into two groups based
on the end products of glucose metabolism.

Those that produce lactic acid as the major or sole product
of glucose fermentation are designated homofermentative.

Those that produce equal amounts of lactic acid, ethanol and
CO2 are termed heterofermentative.

The homofermentative bacteria are able to extract about
twice as much energy from a given quantity of glucose as the
those heterofermentative .
Lactic Acid Bacteria

All members of Pediococcus, Lactococcus, Streptococcus,
Vagococcus, along with some lactobacilli are
homofermenters.

Carnobacterium, Oenococcus, Enterococcus,
Lactosphaera, Weissells and Lecconostoc and some
Lactobacilli are heterofermenters

The heterolactics are more important than the
homolactics in producing flavour and aroma components
such as acetylaldehyde and diacetyl.
Lactic Acid Fermentation
 Lactobacilli
 Streptococci (dairy streptococci)
 Pediococci
 Leuconostocs
Lactic bacteria
Pediococcus - used in production
of fermented meats
Leuconostoc cremoris – used in the
production of buttermilk and sour cream
Lactobacillus bulgaricus – used in
the production of yogurt
Benefits from Lactic Acid
Fermentation
Alteration of flavour, texture, and appearance
 enhancement of nutritional value
 Retardation of food spoilage and reduction of
microbial contamination
 Probiotic effect- prolongation of life: (Metchnikoff
1908) due to lactase, metabolism of dietary
cholesterol, detoxification of potential
carcinogens.

Sequence in changes in raw milk in
relation to acid concentration
Sauerkraut Production
Lactic acid bacteria are
the primary group of
microorganisms
involved in sauerkraut
fermentation
 Shredded cabbage is
placed in a jar and salt is
added to a final
concentration of 2- 2,5%

Sauerkraut Production

sugar contained in the cabbage is converted to
lactic acid  lactic acid fermentation
Fermentation is
completed approx.
after 20 days at room
temperature,
Sequence of acid fermentation in
sauerkraut manufacture
Leuconostoc mesenteroides an acid
and gas producing coccus
Lactobacillus plantarum and bacilli
that produce acid and a small
amount of gas
L. Cucumeris
Lactobacillus pentoaceticus acid and
gas producing bacilli
(L. Brevis
Are fermented foods safer than
fresh foods?
Cases of microbial food-borne infection have
been reported in association with fresh cheese,
sausages, fermented fish and fermented cereals.
 Cases of microbial food intoxications due to
mycotoxin contaminated raw material,
production of microbial toxins, production of
mycotoxins by fungal have been reported.
 Toxic by-products (ethyl carbamate and biogenic
amines) may be produced.

Toxic by-products of fermenta tion:
 Ethyl Carbamate: a carcinogenic and
mutagenic compound which results from
the esterification of ethanol with carbamic
acid (NH2COOC2H5- also known as urethane)
 Biogenic amines - a mildly toxic
substances. 100-200 ppm; >1000ppm is
supposed to elicit toxicity.
Biogenic amines
Biogenic amines in fermented foods
Major risk enhancing factors:
 Use of contaminated raw materials.
 Lack of pasteurization.
 Poorely controlled natural fermentations.
 Sub-optimal
fermentation starters.
 Inadequate storage and maturation
conditions.
 Consumption without prior cooking
How can these risk be minimized
By ensuring wholesomeness of raw materials.
 Optimization of starter cultures by conventional
selection and mutation or by recombinant DNA
manipulations.
 Good hygienic practices during manufactu- ring
 Adequate storage
