Samenvatting
Samenvatting Food Flavour Design (FQD37806)
- Instelling
- Wageningen University (WUR)
summary of knowledge clips, slides, and important information for the course food flavor design in period 2
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Flavour generation by Food Ferrmentation FFD (09/11/20) Part of flavour generation
Made first spontaneously/ by accident with wild yeast or other microbe landing in a
bowl of food
Definitions and and informations
Flavour: what you smell and eat, within eating product, senses will be activated and
send signal to brain whether you like it or not
Fermentation: metabolic process that poduces chemical changes in organic
substrates through the action of enzymes
Fermented food: food or beverages produced through controlled microbial growth
and conversion of food components through enzymatic conversion
- Enzymatically converted food like vanilla and tea are also often included in this
group-> same process but difference in the source of enzymes
Fermented food: preservation (ex. Kimchi and milk product), unique flavour, texture,
appearances, functionalities
- Flavour generated during fermentation can be quite distinctive and different
from the raw material
History
Consumed for thousands of years
Fermentation used to magical or spontaneous-> human doesn’t not invent but
discover and harness it, occur without intervention
Microbes domesticated by human
- Looking at wild yeast-> metabolic capacity to produce ethanol, Co2 and other
important compounds
- Man’s favorite yeast saccharomyces cerevisae -> baker’s/ brewer’s yeast->
cultivated for the purpose
Now starter cultures are used
Create right condition to enable the growth of the desired microorganisms -> control
type of metabolic activity and conversions that will occur
Main purposes of fermentation
Increase shelf life -> historically helped us get through periods of relative scarcity like
on winters
Safer food -> microorganisms display competitive exclusion and have various
mechanisms to prevent growth of other microbes (ethanol, Co2, organic acids)
- Beer consumed instead of water in the past
Increase of nutritional value of foods beyond their raw materials
- Synthesis of vitamins and bioactive components
- Antinutrient breakdown and pre-digestion-> increases nutrient availability
Used as condiments: add excitement to boring meals like kimchi
As flavour enhancers: especially protein rich food
- Meat and fish stored in vats wuth salt -> until nothings left but a concentrated
liquid filled with umami rich glutamates
- Called garums-> like fish sauce
Opportunities for fermentation and flavour
Industrial opportunities
, - Clean label flavours
- Valorization of by products: agroresidues suitable for production of bioflavours
through conversion by microbial enzymes-> more natural and sustainable
alternative to synthethic flavour production
- Functional foods with bioactive components
- Started culture imporvements
- Genetic engineering
Culinary opportunities
- Using known method on novel substrates to develop novel products
- Flavour diversification
Type of fermentations
Can occur in any biological system under the right condition
Our bodies perform anaerobic fermentation and produce lactic acid when
performing high intensity exercise
Product such as alcohol, dairy, bread, legumes, cereal, fruit, vegetable ,meat, fish,
etc.
Majority of fermented food by lactic acid bacteria and fungi particularly yeasts but
also mold to lesser extent
Flavour formed during fermentation through production of volatile and non-volatile
aroma, and other compounds related to taste
Aroma formation consists of complex conversions that can be divided into 2
subprocesses:
1. Generation of aroma precursors
2. Conversion of precursors into the actual aroma compounds
- Processes do not necessarily take place in the same compartment, they can take
place inside/ outside the cell (with the help of extracellular enzyme)
Flavour formed depend on substrate, processing conditions and microorganisms
involved
Fermentation can occur spontaneously through endogenous microbes on food
surfaces/ environment-> complex flavor profile -> less predictable and feasible on
larger scale
- Higher repeatability when mother culture is propagated (ex. Kombucha, sour
dough starter)
- Starter culture technology-> better consistency, safety, quality-> additional
control over fermentation process on flavour generation
Tweak of started culture composition based on genetic content (available
metahbolic pathway), flavour produced can be steered in the desired direction
1. Lactic acid fermentation
LAB can be found in plant surfaces, fruits and human/animal intenstines
- Genetically diverse group of microorganisms that can grown on nutrient rich
foods of animal origin (milk, meat) as well as plant origin
(cereal,fruits,vegetables)
- because of their abundance and association with foods-> main drvers of
many natural/ spontaneous fermentation
- for production of inexpensive wholesome food like sauerkraut, kimchi,
pickles, yogurt, sourdough
, - applied as started cultured on industrial scale for fermentation and
preservation
LAB convert fermentable carbohydrates into mainly lactic acid but also other organic
acid like acetic acid, formic acid, ethanol.
Rapid acidification and consumption of fermentable sugar-> LAB have competitive
edge-> prevent growth of unwanted MO in nutrient rich fermentable raw food
LAB split into 2 pathways that is used to metabolize glucose
a. Homofermentative LAB
- Perform glycolysis through EM pathway with addition of lactate
dehydrogenase
- End product: lactic acid -> generates 2 ATP
b. Heterofermentative LAB
- Use pentose phospohatase pathway = phosphoketolase pathway
- End product depend on conditions
Aerobic: CO2, lactate, acetate are formed
Anaerobic: CO2, lactate, ethanol are formed
- Only 1 ATP/ glucose molecule
Have other metabolic activities that make biochemical changes affecting texture,
nutritional quality, aroma
Metabolic pathways: proteolysis, lipolysis, glycolysis, malolactic fermentation, citrate
metabolism
Aroma formation: affected by metabolic activity of LAB and cell lysis to release the
cell content (cytoplasmic enzymes into food matrix)
- Enzume remain functional outside of cell -> continue to substrate conversion
- Main substrated for cytoplasmic enzumes-> aroma profile: protein,
oligopeptides, lipids, fats, FA
- Lysis of LAB starter culture-> maturation of cheese
Partially hydrolyzed caseins are further hydrolyzed into free amino acids-
> acts as substrates for subsequent catabolism by the remaining intact
cell
- Hydrolysis of peptides by peptidases from lysed LAB -> affect taste-> reduce
quantity of bitter peptides
2. Alcohol fermentation
Beer wine-> alcoholic fermentation by yeasts
Alcohol fermentation not only for alcoholic beverages
Halo tolerant and yest-> meat, cocoa, coffee fermentation
Yeast grow more affectively aerobically but number of yeast can also grow
anaerobically with fermentative metabolisms
Saccharomyces cerevisae-> fermented beverages based on fruits, vegetables and
grains
- All strains can ferment glucose also other plant associated carbs like sucrose,
maltose, raffinose but not lactose
Primary metabolism of yeast: Conversion fermentable sugars into alcohol and
carbon dioxide
Flavour also generated through secondary metabolic activities like amino acid and
sulfur metabolism
Ethanol removal
, - Ethanol -> important sensory for alcohol-> acts as solvent for flavors and
enhance sensory attributes
Excessive: undesirable0> masking aroma and flavour
Desirable to remove to make alcohol free products
- Can be removed postproduction through various physical (thermal and
membrane) methods: reverse osmosis, adsorption distillation, centrifugation,
evaporation, extraction, freeze concentration
Effective but costly and may remove or modified aroma flavor
compounds
- Biological method: enzymatic treatment, use special yeasts, continuous
fermentation
Impossible complete removal but overcome limitations of physical
method
Highest percentage of end product: ethanol
3. Acetic acid fermentation
Vinegar and kombucha
Produced through 2 step process requiring microbial action from both yeasts and
acetic acid bacteria
- Fermentation phase: Sugar from fruits-> converted into ethanol by yeast
- Respiration phase: ethanol converted into acetic acid by acetic acid bacteria-
> sour tasting vinegar and condiments
Yeast facultative anaerobe, AAB -> obligate aerobes
- The 2 steps of acetic fermentation can occur synergistically
Vinegar: expose finished alcoholic ferments to oxygen and AAB
Kombucha: yeast and AAB simultaneously active-> synergy-> Scoby (symbiotic
culture of bacteria and yeast) for starter
- Sugar from fruit converted into ethanol by yeast and subsequently ethanol
converted into acetic acid by acetic
Metabolic Pathways
Formation flavour-> through complex reaction-> part of functional metabolic
pathway
Carbohydrates, protein and lipids can be broken down into minor components that
function as flavour precursor in subsequent reaction series
Primary biochemical pathways: proteolysis, glycolysis, lipolysis-> release flavor
precursors to be converted in subsequent reactions
- Primary conversions: performed by microbial and endogenous enzymes
1. Proteolysis and amino acid metabolism
Proteolysis: breakdown of proteins into peptides by proteinases, and peptides into
free amino acids by peptidases
In protein rich environments, supply of amino acids exceeds the biosynthetic
requirements/ aa composition of protein source doesn’t match aa composition of
biomass of fermenting microbes-> liberated aa converted by catabolic reactions->
formation of volatile aroma compounds depending on the available enzymes and
metabolic pathways
Different enzymes involved in aa catabolism:
- Decarboxylases
- Transaminases
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