Fermented Cocoa, Tea, and Coffee products

Question 1

How coffee beans look like

Answer 1

Coffee is grown as coffee cherries , bean are covered in the silverskin that are inside the pulp

Question 2

By what plant genus coffee beans are produced? how many species of coffee are commercially produced and where

Answer 2

Coffee beans are produced by the genus Coffea
More than 40 species are known, but only a few are commonly available on the market including: C. arabica, C. robusta

• *C. arabica** originated from Brazil, and are currently cultivated in South America, Central America, and some African countries
• *C. robusta** is grown in Cote de Ivorie, Cameroon, Uganda, Indonesia, and India

Question 3

•It takes approximately ___ from flowering for the coffee cherries to reach maturity

Answer 3

1-year

Question 4

Why fermentation is used in coffee?

Answer 4

•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

That is why fermentation is used, it is made to remove the pulp to obtain the green coffee beans

•The fermentation of coffee causes the degradation or breakdown of the mucilage around the parchment skin, which gives the bean a better appearance

Question 5

What is the harvesting and processing for coffee? Three types of drying processes

Answer 5

Question 6

What is the principle of wet processing fermentation

Answer 6

1. •After harvesting the mature beans are mechanically de-pulped
2. •This is followed by a fermentation step to convert the remaining mucilage into water-soluble products that are removed by washing prior to the final drying
3. •The de-pulped berries are held under water in wood or concrete bins
4. •Once the sticky pulp layer is converted into water-soluble products the beans are washed with water and then sun dried or washed with a mechanical drier

Question 7

Over fermentation in wet coffee processes will cause what

Answer 7

•Over-fermentation will cause spoilage and the development of off-flavours

Question 8

What types of enzymes bacteria used in wet processing fermentation should have

Answer 8

Pectinases:

•The mucilage is mostly composed of pectin, therefore the microorganisms that are involved in this reaction must have pectinases

Question 9

What types of microorganisms perform wet processing fermentation: in general and then specific types+ specific types for pectinolytic species and the ones that have been isolated from Kona Coffee beans

Answer 9

• Coffee beans undergo a fermentation step to prepare the fruit for commercial use
• This fermentation involves molds, yeasts, several LAB species, and a few Gram-negative bacteria that originate from the surface of the fruit and soil
• 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
• Erwinia dissolvens have been specifically isolated from Kona Coffee beans

Question 10

How wet-process fermentation is carried out? How long? What is the end result?

Answer 10

• The fermentation reactions is conducted in concrete tanks or bins 1 to 10 m deep, with the bottom of the tank able to allow the water to drain
• The fermentation can last from 24-90h based on climatic conditions
• The end of the fermentation is based on when the mucilaginous tissues change from viscous to liquid

Question 11

How the dry processing for coffee fermentation is carried out?

Answer 11

Question 12

What factors effect the rate of demucilagination? What does it depend on? What type of coffee takes longer to complete it

Answer 12

•The rate at which demucilagination occurs can depend on altitude and temperature

and due to its thicker mucilage, robusta coffee takes longer for complete demucilagination

Question 13

Are starter cultures used for coffee?

Answer 13

•Although starter cultures have the potential to speed this process and improve coffee quality, little research has been conducted on using or making commercial starters

Question 14

what is civet coffee?

Answer 14

Question 15

What is the roasting stage in coffee making? What are the conditions?

Answer 15

• 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 16

What is the raw material for chocolate? any other related products?

Answer 16

•Cocoa beans are the raw material for the production of several products including cocoa powder, cocoa butter, and chocolate

Question 17

Histrorically how fermentation of cocoa beans was used

Answer 17

•In historical times its thought that fermentation was conducted simply to remove the mucilaginous pulp surrounding the cocoa seed and facilitate drying

Question 18

Why fermentation is done today for cocoa beans

Answer 18

• The main reason for this fermentation is to induce biochemical transformations within the beans that lead to the color, aroma, and flavor precursors of chocolate
• Cocoa pods are opened after harvest
• Cocoa pods contain cocoa beans surrounded by a white, carbohydrate rich mucilaginous pulp
• This pulp is the substrate for the fermentation

Question 19

What is the initial microorganism that starts cocoa fermentation? Conditions favoring its growth? What is happening? (pH of CHO pulp, mention end products at this stage), what enzymes these microorganisms have

Answer 19

• 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

Question 20

What is the next microorgnanism after yeast? what do they do? why particular them

Answer 20

•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

Question 21

What bacteria comes after LAB in the final stage? What do they contribute

Answer 21

• 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 22

What happens with sugars during cocoa bean fermentation?

Answer 22

• Glucose at the beginning of the reaction is used by yeast which is the best competitor for this nutrient
• Glucose not used by yeast remains to be fermented by LAB into lactic acid, acetic acid, carbon dioxide, and ethanol
• Fructose is fermented by LAB
• Heterofermentative LAB use fructose as a terminal electron acceptor
• When the fructose is reduced it generates mannitol as a biproduct

Question 23

By-product of fructose as a terminal electron acceptor by heterofermentative bacteria

Answer 23

Mannitol

Question 24

How the fermentation process is arranged for cocoa?

Answer 24

• Box fermentation is the most common method.
• There is a cascade of three boxes. The fermented cocoa beans are transferred every 24 hours to a lower box.
• At the end of the process the fermented cocoa beans are collected

Question 25

What is the critical step during cocoa fermentation and why

Answer 25

•Bean death is a critical event during cocoa fermentation that allows the biochemical reactions necessary for flavor development to occur within the cocoa bean

Question 26

why bean death is important? What induces it?

Answer 26

• The production of ethanol during anaerobic yeast growth correlates well with bean death
• Death is important so that germination will not use valuable components of the bean (cocoa butter)
• From a flavor perspective, death also allows cellular membranes to leak and permit enzymes and substrates to react and form flavor precursor compounds

Question 27

What hydrlytic enzymes are acting on sucrose? and how it is related to browning

Answer 27

• 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

Question 28

Why purple color is a sign of poorly fermented cocoa bean?

Answer 28

•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

Question 29

When oxidative enzymes start play a role in bean fermentation?

Answer 29

•In the late aerobic phase of the fermentation significant oxidative enzyme activity occurs, and this continues into drying

Question 30

What oxidative enzyme plays a role in browning in cocoa beans and when it becomes active

Answer 30

•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

Question 31

What are the major polyphenols in cocoa beans that are subjected to oxidation? how color is related to it

Answer 31

• Catechins and leucocyanidins are the major classes of polyphenols that are subject to oxidation in cocoa beans
• Oxidation of catechins is responsible for the brown colour during cocoa bean fermentation

Question 32

How oxidation of polyphenols is related to taste?

Answer 32

•The oxidation of polyphenols reduces astringency and bitterness associated with the native, unfermented polyphenols

Question 33

Polyphenols are oxidized during fermentation to give a nice flavor. Consumers are more aware of health benefits of polyphenols, so what the industry is trying to do?

Answer 33

• fermentation has been shown to decrease the native polyphenol and antioxidant contents of cocoa beans
• In recent years, consumers have become very interested in the health benefits of polyphenols and their antioxidant activity (especially from chocolate products)
• Therefore, the flavor enhancing properties of cocoa fermentation must now be balanced against the polyphenol- and antioxidant-lowering effects of fermentation

Question 34

Do we want germination in cocoa beans

Answer 34

No, undesirable

Question 35

How drying and storage of cocoa beans is performed? (mention the moisture level after fermentation and what is sage for storing)

Answer 35

• 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)
• Dried beans may be stored for 3-12 months
• Cocoa quality can change during storage depending on the conditions
• However, during storage, slow oxidation and acid loss can enhance the product somewhat, but prolonged storage can result in staling

Question 36

What is Kombucha?

Answer 36

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

Question 37

What is SCOBY?

Answer 37

• The Symbiotic Culture Of Bacteria and Yeast (SCOBY) is a true symbiosis that inhibits the growth of potentially contaminating bacteria
• SCOBY contains a mixture of several species of yeast, acetic acid bacteria, and lactic acid bacteria

Question 38

Why there is somewhat of a mat on the top? (mention specific type of bacteria)

Answer 38

•The fermentation leads to the production of a cellulose pellicle due to the activity of certain Acetobacter sp.

Question 39

What types of yeast are usually used in kombucha? Is it changing?

Answer 39

• Most alcoholic fermentations use S. cerevisiae due to its efficiency
• However, non-Saccharomyces yeasts are becoming more popular in industry to enrich the aromatic profiles and to enhance the complexity of the final product

Question 40

What is the dominant bacteria in kombucha> What species?

Answer 40

• The dominant bacteria in Kombucha are AAB (aerobic bacteria able to use alcohol as a substrate to produce acetic acid)
• Several AAB are known to be present including Acetobacter sp. and Gluconobacter sp.

Question 41

What is the biochemistry of kombucha?

Answer 41

Question 42

The bacteria responsible for cellulose production

Answer 42

Komagataeibacter xylinus,

Question 43

How cellulose is produced by Komagataeibacter xylinus,

Answer 43

• K. xylinus synthesizes uridine diphospho-glucose (UDPGlc) which is 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

Question 44

Why cellulose is produced in kombucha? How it is related to other bacteria?

Answer 44

• Initially when the fermentation is started cellulose producing bacteria increase in population though the consumption of dissolved oxygen (no need to float)
• The bacteria then start to synthesize cellulose to maintain their position at the air/medium interface and only bacteria that do this can maintain activity (so they become dominant)
• As the fermentation advances, the membrane thickness increases by the generation of new layers of cellulose, forming a suspended structure in the culture medium
• Eventually, the SCOBY will become dormant due to insufficient nutrients and oxygen

Question 45

Why can you start your own SCOBY from unpasteurized kombucha?

Answer 45

•Some bacteria will remain dormant in the liquid phase, but can be reactivated and used as a starter in a later fermentation

Question 46

Why there can be concerns for kombucha safety?

Answer 46

• Pathogenic microbes can contaminate kombucha right after the boiling step up until the pH drops below 4.2→ that is why back sloping with old kombucha to drop pH immediately
• Until this pH is reached pathogenic bacteria could outgrow your SCOBY and result in dangerous kombucha
• There has been one case of unhygienic kombucha exposure that led to an anthrax infection
• Mold can also contaminate kombucha and result in poisoning

Question 47

What is the chemical safety concerns for kombucha?

Answer 47

• Over-fermentation can result in excessive acetic acid production, resulting in a low pH environment that can leach out some chemical contaminants
• For example, cases of lead poisoning have been associated with kombucha brewed or stored in glazed earthenware
• Kombucha can change the uptake of some medical drugs in the stomach, and should not be drank by anyone taking medical drugs