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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.
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Fermentation processes:
Lactic acidAlcoholic
Acetic acid
Propionic acid
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Fermented foods
Beverages
Dairy products
Cereals
Meat and fishFruits and vegetables
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Beverages
Beer
WineSake
Cider
spirits
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Dairy products
Cheese
Yoghurt
Kefir
Kurut
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Cereals
Breads
Rolls
dosa, idli, adai, vada (cereals& legumes)
lao-chao, kenkey, ogi
injera
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Meat and Fish
Jerky, country ham, salami, pepperoni
pickled meat
fish sauce, paak, bagoong
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Fruits & vegetables
Pickled fruits & vegetables
olivessauerkraut
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Contribution of the fermented
foods:
Enrichment of the human dietary
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] a decrease the cooking time and fuel
requirements
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Preservation principle:
To hinder (delay) the growth of
food spoilage microorganisms
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Alcoholic fermentation:
Simple sugars yeasts > ethanol
Saccharomyces cerevisiae
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Yeasts involve in fermentation
should possess:
Rapid and relevant carbohydrate
fermentation ability;
appropriate flocculation and
sedimentation characteristics;
genetic stability;
osmotolerance
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Yeasts involve in fermentation
should possess:
ethanol tolerance
ability to produce elevated concentration
of ethanol;
high cell viability for recycling;
temperature tolerance.
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Alcoholic fermentation is
affected by:
Oxygen supply
sugar content
alcohol content
temperature
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Alcoholic fermentation:
Unlimited oxygen supply - cell
growth
Limited oxygen supply - alcohol
production
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Beer
A diluted solution of ethanol with a
characteristic flavour arising from theuse of malt as predominant source of
carbohydrates and other yeast
nutrients and hops as a source of bittercomponents.
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Kinds of beer
Lager - produced by bottom fermen-
ting yeasts ( Saccharomyces uvarum) .
Ale - produced by top fermenting
yeasts ( Saccharomyces cerevisiae)
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Production of beer:
Malting
Mashing
Boiling of wort with hops
FermentationStorage
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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 sproutsCrushing the malt
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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.
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Boiling of wort with hops is done to:
concentrate it
sterilize itinactivate enzymes
extract soluble substances from hops
coagulate and precipitate proteins
contribute antiseptic resins:
humulone, cohumulone, adhumulone.
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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).
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Storage and packaging
after fermentation beer is stored (lagered)
at 0 C (several weeks to several months)
clarified or filtered
pasteurized at 60 C shortly
carbonated to CO2
content 0.45-0.52%
packaged to cans or bottles.
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Beer defects (off flavour) may be
due to:
butyric (Clostridiumsp.) 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/orsilky turbitidy.
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WINES
Products obtained by alcoholic
fermentation of grapes, grapejuices, fruit juices, berries,
rhubarb, honey etc by yeasts.
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Kinds of wines
still wines
sparkling winesartificially carbonated wines
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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 ofpigments from a skin (mixing must twice a
day ].
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Steps involve in fermentation of
wine:
Active fermentation:
- red wines 24 -27 0C; 3-5 days;
- white wines 10-210
C; 7-14 days; separation of fermented juice from residue
(pomace);
placing fermented juice under light CO2pressure
secondary fermentation: 21-29 0C, 7-11 days.
aging of wines.
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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%.
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Calculation steps:
C6H12O62 C2 H2OH + 2 C02
1. Calculate the amount of sugar in must.
M1 = 30 * 0.26 = 7.8 kg
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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 fermented sugar;
M3- weight of produced alcohol.
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Calculation steps:
3. Calculate the weight of sugar in wine.
M4 = M * 0.02
4. Calculate the weight of sugar fermen-
ted to alcohol.M2 = (7.8 - M4 ) * 0.94
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Calculation steps:
5. Calculate the weight of produced alcohol.
C6H12O6 2 C2 H2OH + 2 C02 180 92
M2 M3
---------------------------------M3= 92 * M2 /180 = 92* ( 7.8 - M4)/180 =
92* ( 7.8 - M * 0.02) * 0.94/180
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Calculation steps:
6. Calculate the final weight of wine (M)
M = M0 - M2 + M3
M = 30 - (7.8 - 0.02*M)+
+ 92*(7.8 - 0.02*M) *0.94/180
M = 26.22 kg of wine
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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
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Calculation steps:
8. Calculate [ % ; w/w) of ethanol in wine.
[%] = M3/M * 100
[%] = 3.495/26.22 *100
[%] = 13.3%
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Production of ethanol
Starch pretreatment:
-gelatinization,-liquefaction,
-saccharification
Fermentation
Distillation
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Lactic Acid Fermentation
Lactobacilli
Streptococci (dairy streptococci)
Pediococci
Leuconostocs
B fit f L ti A id
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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.
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Sequence in changes in raw milk in
relation to acid concentration
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Sequence of acid fermentation in
sauerkraut manufacture
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Are fermented foods safer than
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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.
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Toxic by-products of fermenta tion:
Ethyl Carbamate: a carcinogenic and
mutagenic compound which results from
the esterification of ethanol with carbamicacid (NH2COOC2H5- also known as urethane)
Biogenic amines - a mildly toxic
substances. 100-200 ppm; >1000ppm issupposed to elicit toxicity.
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Biogenic amines
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Biogenic amines in fermented foods
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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
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