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CHE1010 Grand Challenges in
Chemical Engineering
Fermented foods and beverages
Part I
Outline – Learning objectives
Understand fermentation as a form of food and beverage processing
Purposes of food and beverage fermentation
Major microorganisms used for food & beverage fermentation
Chemical engineering principles including biochemical reactions, mass transfer,
heat transfer, fluid mechanics
Unit operations for fermentation at scale
What is fermentation?
• Oldest form of food processing e.g. fermented milk products have been
produced since around 10,000 BC
• Involves addition/presence of safe-to-humans microorganisms to food
materials to undergo change
• Sugars (e.g. glucose, sucrose, lactose, galactose, fructose, starch etc) of
varying forms are converted to products via microorganisms forming acids
• Proteins and lipids may also be partially digested to form peptides, fatty acids
• Range of metabolites may be produced including acids, alcohols, aldehydes,
esters, ketones, vitamins
Biochemical
reactions
Foods
Examples of fermented food and beverages
Drinks
Cheese Salami
Sauerkraut Injera
Chocolate Breads
Kimchi Pickled vegetables
Miso Fermented fish and shrimp
Tempeh Dosa
Yogurt Black beans
Olives
Non-alcoholic
Kefir
Kombucha
Brewed soft drinks
Cider and wine vinegars
Buttermilk
Probiotic drinks e.g. Yakult
Alcoholic
Beer – corn, barley, rice etc
Wine – grapes, fruits, berries
Photo: Harvard Medical School
Purposes of fermentation
• Protection of foods from spoilage by pathogenic = disease causing
microorganisms
• Improves flavours e.g. miso
• Lengthens storage life
• Makes some foods more tolerable e.g. lactose glucose + galactose
• Breakdown of anti-nutritional components occurring naturally in foods
e.g. lectins, phytates
• May improve digestibility and nutrition e.g. vitamins
What microorganisms are used in fermentation?
Yeasts
e.g. Bakers/Brewers yeast
Saccharomyces cerevisiae
Filamentous fungi or mould
e.g. Aspergillus oryae
Bacteria
e.g. Lactic acid bacteria (LAB)
such as Lactobacillus sp.
195 bacterial and 69 species of yeasts and fungi have demonstrated safe food usage
Relative size of microorganisms
Yeast
Principle: Biochemical reactions
• is the transformation of one molecule to a different molecule inside
a cell.
• mediated by enzymes (biological catalysts) that can alter the rate
and specificity of chemical reactions inside cells.
Ribbon diagram of beta-galactosidase
enzyme which hydrolyses lactose to
galactose and glucose.
Enzymes are proteins made of a chain of
amino acids, precisely folded to enable
catalysis of reactions.
See Advanced Content
folder on Moodle for
more information
Enzymes involved in common
fermentation processes
Enzyme
β-galactosidase (lactase)
Amylase
Protease
Lipase
Substrate and product
Lactose galactose + glucose
Starch glucose molecules
Protein amino acids
Fats/lipids fatty acids
All are examples of hydrolysis reactions
Fermentation steps undertaken by microbes in limited oxygen
What happens with oxygen present?
‘Brewers yeast’ Saccharomyces
cerevisiae ferments glucose to ethanol in
presence of oxygen but other organisms
will progress metabolism to CO2
Sugar released from starch or lactose by enzymes
Typical product of
Saccharomyces
yeast
Typical product of
Lactobacillus
bacteria
Major food-borne human pathogens
• major human pathogens include Salmonella, Listeria, Campylobacter,
pathogenic Escherichia coli
• fermentation organisms cause unfavourable conditions for pathogenic
microbes
• Lactic acid bacteria:
produce lactic acid and other functional antimicrobial metabolites, such as
diacetyl, acetoin, hydrogen peroxide, bacteriocins
Salmonella sp. bacteria
Photo: MedicineNet
