Download Food processing and Preservation-fermentation

Food processing and
Preservation
Fermentation
History
• Since fruits ferment naturally, fermentation
precedes human history. Since ancient times,
however, humans have been controlling the
fermentation process. The earliest evidence of
winemaking dates from eight thousand years
ago, in Georgia, in the Caucasus area.
• Seven-thousand-year-old jars containing the
remains of wine have been excavated in the
Zagros Mountains in Iran, which are now on
display at the University of Pennsylvania
• French chemist Louis Pasteur was the first
known zymologist, when in 1854 he connected
yeast to fermentation. Pasteur originally defined
fermentation as "respiration without air".
Pasteur performed careful research and
concluded;
• "I am of the opinion that alcoholic fermentation
never occurs without simultaneous organization,
development and multiplication of cells.... If
asked, in what consists the chemical act
whereby the sugar is decomposed ... I am
completely ignorant of it."
• When studying the fermentation of sugar to
alcohol by yeast, Louis Pasteur concluded
that the fermentation was catalyzed by a vital
force, called "ferments," within the yeast
cells. The "ferments" were thought to
function only within living organisms.
• "Alcoholic fermentation is an act correlated
with the life and organization of the yeast
cells, not with the death or putrefaction of
the cells,” he wrote.
Worldwide production of some
fermented foods
Food/beverages
Cheese
Yogurt
Mushroom
Fish sauces
Dried stockfish
Beer
Wine
Quantity
15 million tons
3 million tons
1.5 million tons
300,000 tons
250,000 tons
1000 million liters
350 million liters
Fermentation
• Fermentation in food processing typically is
the conversion of carbohydrates to alcohol
and carbon dioxide or organic acids using
yeast, bacteria or combination thereof, under
anaerobic conditions.
• A more restricted defination of fermentation
is the chemical conversion of sugar into
ethanol. The science of fermentation is
known as zymology
• Fermentation usually implies that the action
of microorganisms is desirable, and the
process is used to produce alcoholic
beverages such as wine, beer, and cider.
• Fermentation is also employed in
preservation techniques to create lactic acid
in sour foods such as sauerkraut, dry
sausages, Kimchi and yogurt, or vinegar
(acetic acid) for use in pickling foods.
Food fermentation
• Definition
• Fermentation is the slow decomposition process
of organic substances include by-microorganism
or by complex nitrogenous substances
(enzymes) of plant or animal origins
• It can be describe as a biological change, which
is brought about by the anaerobic or partially
anaerobic oxidation of carbohydrates by either
microorganisms or enzymes
• Bacteria derive their energy during
fermentation
• A relatively incomplete biochemical reaction
– final product is still in organic compound
• Conversion of food components in to other
components by microorganisms
• Sugar
alcohol
• Protein
peptide, amino acids,
• Lipid
fatty acids
• Typical substrates include sugars (e.g.
glucose) & amino acids.
• Typical products depend upon the substrate
but include organic acids (lactic acid, acetic
acid), alOH (etOH, metOH, butOH), ketones
(aceton) and gases (H2 & CO2)
• Also used to describe other microbiological
related reactions (digestion in the lower
intestine for example)
• Usually involves the production of some
compound inhibitory to other
microorganisms
• e.g. organic acids, diacetyl, acetoin. Hidrogen
peroxide, nicin (bacteriocin produced by
Lactococcus lactis)
Benefits of Fermentation
Benefit
Raw material
Fermented food
Preservation
Milk
Enhancement
of safety
Acid production Fruit
Yoghurt, cheese
Vinegar
Acid & alcohol
production
Barley, Grapes
Beer, Wine
Production of
bacteriocin
Meat
Salami
Benefits of Fermentation
Benefit
Removal of toxic
components
Enhancement of
nutritional value
Improved
digestability
Retention of
micronutrients
Increased fibre
content
Raw material
Cassava,
soybean
Fermented food
Gari, soysauce
Wheat
Bread
Leafy vegs
Kimchi
Coconut
Nata de coco
Benefits of Food Fermentation
• Preservation/food safety – due to acid &
alcohol: pH < 4.6, no pathogens grow
(including C. botulinum)
– Certain lactic acid bacteria (e.g. Lactobacillus
acidophilus) and moulds have been found to
produce antibiotics and bacteriocins
– Alcohol is germicidal & acetic acid is bactericidal
• Improve nutritive value
– Bacteria breakdown several complex
compound
– Synthesis of vit B12, riboflavin, precursor of
vit C – increase vit levels – exmp Idli (a lactic
acid bacteria fermented product consumed in
India) is high in thiamine & riboflavin
– Saccharomyces cerevisiae is able to
concentrate large quantities of thiamin,
nicotinic acid & biotin & thus form enriched
products
• Improve nutritive value cont…
– Release of nutrients by rupturing cellulosic &
hemicellulosic str – more availability of
entrapped nutrients (e.g. moulds with
cellulose-splitting enzymes)
– Removal of anti-nutritional factors; e.g.
cyanogenic glucoside in cassava removed
upon fermentation; trypsin inhibitors, phytate
• Improve nutritive value cont…
– Improve digestability – Microbial cellulases
hydrolyse cellulose into sugars which are then
readily digested by humans
– The beneficial health effects of lactic acid
bacteria on the intestinal flora are well
documented
• Improve the textural & sensory properties of
food
– Distinct aroma & flavour compounds: acids,
carbonyl compounds, esters, ethanol, ketones,
lactones, pyrazines, etc
– Altered texture, e.g. milk – cheese/yogurt,
cereals – bread, soybean – soysauce.tempe
• Salvaging food waste
– Tempe-bongrek – a protein rich food made in
Indonesia by fermenting peanut and coconut
press-cake, remaining after oil extraction
– Ontjom – from waste groundnut press cake,
tapioca waste and the solid waste of tahu
Typical organisms involved in
fermentation
• Lactic acid bacteria
– Lactobacillus
– Lactococcus
– Leuconostoc
– Acidophilus
– Pediococcus
• Yeast
– Saccharomyces
• Moulds
– Penicillium
– Rhizopus
– Aspergillus
– Botrytis
Common Fermentation Activities
• Alcoholic/Ethanolic fermentation
 Generally yeast fermentation (S.
cerevisiae, S. ellipsoideus), or yeast-like
moulds (Amylomyces rouxii) & mould-like
yeasts (Endomycopsis)
C6H12O6
2C2H5OH + CO2
Common Fermentation Activities
cont..
The yeasts multiply & ferment rapidly –
other organisms (aerobic) cannot compete
 CO2 flushes out residual O2 & maintains
the fermentation anaerobic
 Examples: Wine & Beer, leavening of
bread, tapai, rice wines
• Mixed alcoholic and Acid Fermentations
 If the products of alcoholoc fermentation are
not kept anaerobic, Acetobacter bacteria may
oxidize portions of the ethanol to acetic
acid/vinegar
 C6H12O6 + O2
CH3COOH
Examples: vinegar from cider or wine, palm
wines, Keffir beers, Kombucha tea
Acetic acid is bacteriostatic
• Lactic acid fermentations
– Fermentable sugars are converted to lactic acid
by lactic acid bacteria: Leuconostoc
mesentroides, Lactobacillus brevis, Lactobacillus
plantarum, Pediococcus cerevisiae, Streptococcus
thermophilus, etc
– Provide a wide variety of flavours, aroma &
textures
– Examples: Sour milk, yogurt, Kimchi, sauerkraut,
pickled vegs
Classificationof Food Fermentations
• Fermentations producing textured vegetable
protein meat substitutes in legume. cereal
mixtures; e.g. Indonesian Ontjom and tempe
• High salt/savory meat – flavored/amino
acid/peptide sauce & paste fermentations;
e.g. Chinese soysauce, Japanese shoyu &
miso, Korean kanjang, Indonesia tauco, fish
sauces. Malaysian budu & belacan etc..
• Lactic acid fermentations – sauerkraut,
cucumber & olive pickles, Korean Kimchi.
Malaysian tempoyak, yogurts, Russian kefir,
India dahi, cheese etc…
• Alcohol fermentations – grape wines, beers,
palm wines, rice beer, Japanese sake, sugar
cane wines etc…
• Acetic acid/vinegar fermentation – Apple
cider, wine vinegars, palm wine vinegars,
coconut water vinegar, tea fungus/kombucha
tea, nata de coco, nata de pina
• Alkaline fermentations – Nigerian dawadwa,
African iru, ogiri, Thai thua-nao
• Leavened breads – Yeast & sourdough breads
• Flat unleaved breads
Controlling Fermentation Process
• Wild/Uncontrolled Fermentation
– Sauerkraut, pickles and olives
– Coffee, tea and cocoa
– Tempoyak
• Controlled Fermentation
– Adding specific microorganisms to get the desired
product every time or to support the activity of only
desired microbes
– Most common controls are: acid level, alcoh level,
use of starter, level O2, amount of salt
1. Control of Acid
• Acid suppresses the growth of non-acid
tolerant spoilage organisms
• Contaminated moulds can further ferment
the acid in presence of O2, the inhibitory
effect of acid is lost and some other
proteolytic & lipolytic organisms start to
grow at the surface, e.g. defect in Cheddar
cheese
• Certain yeasts tolerant to high acid – produce
alkaline end products (e.g. ammonia) from
the breakdown of protein – acid preservation
is lost
• Example: Raw milk fermentation
• Various microbial contaminants
• Acid development by Str. Lactis – inhibit
other organisms
• Lactobacillus organism more tolerant to acid
– take over the acid fermentation
• Example: Raw milk fermentation cont…
• High acidity itself inhibitory to genus
Lactobacillus, they start dying
• Acid- tolerant yeast & moulds start growing –
gassy product
• Alkaline end products from proteolysis –
neutralization of acid by alkaline products
• Example: Raw milk fermentation cont…
• Proteolytic & lipolytic bacteria find a
favourable enviroment
• Proteolysis brings down the milk acidity than
the fresh one
• Final product – gassy, putrefied, off-odour
2. Control of Alcohol
• Alcohol can be preservative depending on
concentration
• Example: Wine production
• Alcohol level in wine depends on: Sugar
content of grapes, types of yeast
fermentation temperature, level of oxygen
• Yeast cannot tolerate their own alcohol &
other fermentation product
• Example: Wine production cont…
• Natural wine contain 9-13 % alcohol by
volume – this concentration not enough for
preservation – pasteurization needed
• Fortified wine products (20% alcohol) do not
need pasteurization
3. Use of Starter Cultures
• Starter cultures – preparations of one or
more strains of one or more species of
microorganisms: they are subcultures
• Better control on fermentation
3. Use of Starter Cultures cont..
• Domination of desired organism right from
beginning
• Special cultures available for: wine, butter,
cheese, yogurt, pickles, vinegar, beer,
sausage, bread and other fermented foods
3. Use of Starter Cultures cont..
• Examples: Butter (mixed culture containing
Lactococcus lactis sub spp, lactis cremoris,
Leuconostoc mesenteroides sub spp).
• Yogurt (Lactobacillus casei, L. acidophilus,
Bifidobacterium).
• Sausage (Lactic acid bacteria).
3. Use of Starter Cultures cont..
• Beer (Geotricum candidum – inhibit
undesirable moulds)
• Normally food heated to inactivate
detrimental types of organics prior to starter
addition
4. Control of Temperature
• Each organisms has its own optimum growth
temperature
• Control of temperature to encourage the
growth of desirable organism
• Example: Sauerkraut production
• Three types of bacteria:
– Leuconostoc mesenteroids (opt. temp. 21 °C) –
acetic acid, lactic acid, alkoh, CO2
• Lactobacillus cucumeris (opt temp 21 °C) –
produce acetis acid when leuconostoc stop
growing
• Lactobacillus pentaceticus – still more acetic
acid when L. cucumeris ceases
5. Control of Oxygen
• Mould – require oxygen
• Yeast – for alcohol production better with O2
• Bakers yeast Saccharomyces cerevisiae –
better in aerobic condition
• Rapid fermentation of sugar under anaerobic
condition
• Commercial production of yeast – air
bubbling in molasses solution
• Example: Vinegar Production
• Initial aerobic condition – stimulate growth &
increases cell mass
• Anaerobic condition – fermentation sugar to
alkoh
• Aerobic condition – alcoh to acetic acid
(oxidative fermentation)
6. Control of Salt
• Various organisms - different salt tolerance
• Lactic salt bacteria (used in fermenting olives,
sauerkraut, meat sausages) tolerant up to 1018% salt concentration
• Proteolytic & other spoilage organisms not
tolerant above 2.5% salt
• Growth of lactic acid bacteria at higher acid &
salt concentration
• Different salt levels: 2-2.5% in sauerkraut
production; 7-10% in olive fermentation;
15%-18% in cucumber fermentation
• Salt added in cheese curd – prevention from
proteolytic bacteria.