cocoa, tea, and coffee products

Question 1

Coffee beans are produced by the genus ….

Answer 1

Coffea

Question 2

which species are commonly available on the market for coffee fermentation?

Answer 2

coffea arabica

coffea robusta

Question 3

how do you make coffeee beans for making coffee?

Answer 3

It is necessary to first remove the parchment and the pulp layer to obtain the green coffee beans, which can then be dried, roasted, milled, and used for making coffee

Question 4

what are the three coffee processing methods?

Answer 4

1. dry process
2. wet process
3. honey processing

Question 5

what is the dry processing method for coffee?

what does this process yield?

Answer 5

Coffee cherries’ pulp layer is partially dried in the sun while the coffee fruit is ripening. It can take 10-25 days of sun drying. During this time microbial fermentation occurs, enzymes secreted by bacteria, yeasts, and pectinolytic molds break down the pulp and mucilage.
During the drying the sugars and flavors from the pulp are absorbed by the bean.
This process yields NATURAL COFFEE

Question 6

what is the wet processing method for coffee?

what does this process yield?

Answer 6

• after harvesting the mature beans are mechanically de-pulped
• this is followed by a fermentation step (5-7 days) to convert the remaining mucilage around the parchment skin into water-soluble products that are removed by washing prior to the final drying
• this enhances acidity and provides a final floral aromatic property to the coffee bean.
  This process yields WASHED COFFEE
• Over-fermentation will cause spoilage and the development of off-flavours

Question 7

what is honey processing for coffee?

Answer 7

Coffee cherries can be striped of the pulp (outer fruit) and dried without washing. Some pulp will remain on the bean. The beans are dried. They must be turned hourly for 10-15 days

Question 8

what organisms are involved in coffee fermentation?

Answer 8

molds, yeasts, several LAB species, and a few Gram-negative bacteria that originate from the surface of the fruit and soil.

Question 9

the mucilage of coffee berries is mostly composed of …, therefore the microorganisms that are involved in the fermentation must have…

Answer 9

pectin

pectinases

Question 10

how do you determine the end of the coffee fermentation?

Answer 10

when the mucilaginous tissues changes from viscous to liquid

Question 11

what climate condition leads to a quicker coffee fermentation process?

Answer 11

hot temperatures

Question 12

which microorganisms are detected during the fermentation steps of coffee?

Answer 12

Most of the microorganisms detected during these fermentation steps belong to Enterobacter and Escherichia
Pectinolytic species then colonize and dominate the fermentation including Bacillus, Fusarium, Penicillium, Aspergillus

Question 13

what does the uniqueness and flavour of coffee depend on?

Answer 13

Microorganisms present during fermentation

Question 14

the rate at which demucilagination occurs depends on … and … and due to its thicker mucilage, … coffee takes longer for complete demucilagination

Answer 14

altitude and temperature

robusta

Question 15

what is civet coffee?

Answer 15

This coffee is produced following consumption of ripe coffee cherries by the civet
The coffee cherries undergo fermentation in the animal’s gastrointestinal tract and the animal excretes the hard, indigestible coffee beans
Exported finished coffee beans: $227usd / pound

Question 16

about roasting coffee beans:

Answer 16

• Roasting is a necessary step for the preparation of the final bean
• Industrial roasting ranges from 90 s to 6 min, while handcrafted roasting may range between 18-20 minutes
• Roasting conducted using rotary drums at temperatures from 200-250C
• Coffee produced in each country by various processes have its own unique flavor

Question 17

manufacturing of cocoa powder, cocoa butter, and chocolate must first be preceded by ……

Answer 17

post-harvest fermentation of the cocoa beans (box fermentation - cascade where fermented cocoa beans are transferred every 24h to a lower box)

Question 18

why do we ferment cocoa beans?

Answer 18

induce biochemical transformations within the beans that lead to the color, aroma, and flavor precursors of chocolate (amino acids, peptides, reducing sugars, and polyphenols)

Question 19

what is the substrate of the fermentation of cocoa beans?

Answer 19

the white, carbohydrate rich mucilaginous pulp surrounding the cocoa pods

Question 20

cocoa bean fermentation process

Answer 20

• The carbohydrate rich pulp has a pH of 3.0-4.0 and is anaerobic because the pulp/bean mass is stored in heaps or boxes => This favors the growth of YEAST (which originates from the flowers or fruit of the cocoa plants)
• The yeasts initiate an anaerobic alcoholic fermentation and convert carbohydrates (sucrose and glucose) into ethanol and CO2
• Pectinolytic enzymes are also produced by the yeast and they degrade pectin allowing the air to progress into the mass during fermentation since the pulp becomes less viscous and begins to drain
• The presence of air and ethanol then favors LAB, which can ferment carbohydrates (glucose and fructose) via the homofermentative pathway into lactic acid, or the heterofermentative pathway into lactic aid, acetic acid, ethanol, and CO2
• In the final stages of cocoa bean fermentation the conditions become favorable to AAB due to the aeration caused by further breakdown of the pulp and the availability of ethanol and organic acids => the AAB oxidize the ethanol into acetic acid
• The acetic acid diffuses into the cocoa bean and is responsible for the death of the embryo, and this marks the end of the fermentation

Question 21

why is bean death during cocoa fermentation, a critical event (3)? when does it occur?

Answer 21

Day 3: The production of ethanol during anaerobic yeast growth correlates well with bean death

• allows the biochemical reactions necessary for flavor development to occur within the cocoa bean
• germination will not use valuable components of the bean (cocoa butter)
• allows cellular membranes to leak and permit enzymes and substrates to react and form flavor precursor compounds

Question 22

hydrolytic enzyme reactions in cocoa bean fermentation

Answer 22

Sucrose is the major sugar in unfermented cocoa beans (it is not a reducing sugar and does not participate in non-enzymatic browning) => During the fermentation reaction invertase converts 95% of sucrose to glucose and fructose, which are reducing sugars and contribute to browning
Glycosidases digest the the purple anthocyanins that give the bean the deep purple colour. This results in a bleaching of the purple, and the release of further reducing sugars that participate in flavor development -> Cocoa beans that still contain significant purple colour are considered as poorly fermented and are less desirable

Question 23

oxidative enzymatic reactions

Answer 23

In the late aerobic phase of the fermentation significant oxidative enzyme activity occurs, and this continues into drying: Polyphenol oxidase is the major oxidase in cocoa and is responsible for much of the brown colour that occurs, it becomes active when oxygen is able to penetrate the bean in the final stages of fermentation
The oxidation of polyphenols reduces astringency and bitterness associated with the native, unfermented polyphenols

Question 24

which major classes of polyphenols are subject to oxidation in cocoa beans?

Answer 24

catechins (oxidation of these is responsible for the brown color during fermentation) and leucocyanidins

Question 25

what does fermentation of cocoa beans decrease?

Answer 25

the native polyphenol and antioxidant contents of cocoa beans

Question 26

… is undesirable in cocoa beans that are used to make chocolate

Answer 26

germination

Question 27

when drier cocoa beans are roasted, … occur, to produce flavor and color compounds that are characteristic of chocolate

Answer 27

non-enzymatic browning reactions

Question 28

why should dry fermented cocoa beans?

Answer 28

After the beans are fermented they have a moisture content of 40-50%, and this must be reduced to 6 to 8% for safe storage or mold growth may become an issue

Question 29

How can the cocoa beans be enhanced during storage?

Answer 29

due to slow oxidation and acid loss but prolonged storage can result in staling

Question 30

what is kombucha?

Answer 30

beverage obtained by fermenting tea (with added sugar) with a microbial consortium composed of several bacteria and yeasts

Question 31

what is SCOBY?

Answer 31

Symbiotic Culture Of Bacteria and Yeast - a true symbiosis that inhibits the growth of potentially contaminating bacteria
-> it contains a mixture of several species of yeast, acetic acid bacteria, and lactic acid bacteria

Question 32

what does the fermentation of tea + sugar produce?

Answer 32

production of a cellulose pellicle due to the activity of certain Acetobacter sp.

Question 33

why is there vitamin B12 is kombucha

Answer 33

it is produced by the microorganisms

Question 34

which yeast is used in kombucha?

Answer 34

saccharomyces cerevisiae

Question 35

what is the dominant bacteria in Kombucha?

Answer 35

AAB (aerobic bacteria able to use alcohol as a substrate to produce acetic cid)
- Acetobacter sp. and Gluconobacter sp.

Question 36

how is cellulose (SCOBY) made during kombucha fermentation?

Answer 36

Cellulose production is primarily by Komagataeibacter xylinus (increase in population initially through the consumption of dissolved oxygen) which synthesizes uridine diphospho-glucose (UDPGlc), a cellulose precursor (Each single cell can polymerize up to 200,000 glucose residues per second into B-1,4-glucan chains)
Cellulose is produced extracellularly in the form of fibrils that are attached to the bacterial cell. Each cell has between 50 and 80 pores or complex terminals (CTs) for extruding cellulose out of their membrane
=> These chains are later assembled to form thicker fibrils called macrofibrils
Production of cellulose is done maintain their position at the air/medium interface (SCOBY floats) and only bacteria that do this can maintain activity (so they become dominant)
Eventually, the SCOBY will become dormant due to insufficient nutrients and oxygen and some bacteria will remain dormant in the liquid phase, but can be reactivated and used as a starter in a later fermentation

Question 37

what conditions for pathogenic microbial contamination in kombucha?

Answer 37

right after boiling step up until the pH drops below 4.2 - above this pH pathogenic bacteria can outgrow SCOBY and be dangerous -> Bacillus enteritis
Mold can also contaminate kombucha

Question 38

what happens when there’s over fermentation of kombucha?

Answer 38

excessive acetic acid production, resulting in a low pH environment that can leach out some chemical contaminants