Cocoa, Tea, Coffee

Question 1

The 2 common species of coffee bean:

Answer 1

Coffea arabica (South and central America, Africa)
Coffea robusta (Africa, Asia)

Question 2

What are the 3 methods of coffee processing? Describe them

Answer 2

1. Dry process: directly dry entire coffee bean -> NATURAL COFFEE
2. Wet process: remove fruit pulp through fermentation -> wash off -> dry -> WASHED COFFEE
3. Honey process: fruit mostly removed, some mucilage remain -> dry -> HONEY COFFEE

Question 3

What is the purpose of the ferment step in washed coffee?

Answer 3

1. degrade fruit pulp/mucilage (make water soluble) for easy removal
2. develop flavor/aroma

Question 4

What are common microbes found during coffee bean fermentation?

Answer 4

Escherichia, Enterobacter

Bacillus, Fusarium, Penicillium, Aspergillus

Erwinia dissolvens (from KONA COFFEE)

Question 5

How long does the coffee bean wet ferment usually last?

Answer 5

24-90 hrs

Question 6

Does fermentation occur with naturally dried coffee?

Answer 6

Yes; pulp and mucilage still present, fermented by yeast, bacteria, molds

Question 7

True/False: starter cultures are used in coffee bean fermentation

Answer 7

False; not commercially used, little research

Question 8

Which bean variety takes longer for the demucilagination process? Why? What other factors have an effect?

Answer 8

robusta
thicker layer
temperature, altitude

Question 9

___ is an important step in preparing the final coffee bean. What are the common industrial conditions?

Answer 9

roasting

90s-6min at 200-250C (rotary drum)

Question 10

True/False: all cocoa beans are fermented. Why or why not?

Answer 10

True.

need to remove pulp, develop flavor/color/aroma

Question 11

What is fermented in the cocoa bean pod?

Answer 11

pulp surrounding cocoa bean (rich in carbs)

Question 12

What organism grows first in the cocoa bean ferment? Why?

Answer 12

yeast

favorable conditions: anaerobic, high in sugar, pH 3-4

Question 13

What occurs in the cocoa pod composition during the yeast growth period?

Answer 13

ethanol and CO2 produced
sugars decrease
pectinolytic enzymes -> degrade pectin

Question 14

What creates favorable conditions for LAB to grow in cocoa?

Answer 14

yeast will create degrade pectin -> permeable to allow air in -> AEROBIC CONDITIONS

Question 15

What organism is present at the end of the cocoa bean ferment? What allows it to grow?

Answer 15

AAB
more breakdown of pulp -> more air
ethanol made by yeast, organic acids made by LAB

Question 16

what is the cause of the end of cocoa fermentation?

Answer 16

AAB make acetic acid -> diffuse into bean -> BEAN DEATH

Question 17

At the beginning of the cocoa ferment, glucose is used by ____. Fructose is used by: ______. Citric acid can be used by: ___.

Answer 17

yeast (best competitor); some used by LAB

LAB

Some LAB (citrate positive): use as co-substrate

Question 18

What organism is NOT present in the beginning of the ferment? why?

Answer 18

AAB
anaerobic conditions (stored in heaps/boxes)

Question 19

How is a cocoa bean fermentation usually set up?

Answer 19

box fermentation most common
stacked boxes containing beans
every 24 hrs, move to lower box -> collect at end

Question 20

Why is bean death important in cocoa fermentation?

Answer 20

prevent germination (which uses up nutrients in bean)
flavor development (enzymes/substrates in bean react after death -> flavor precursors)

Question 21

What is the main sugar in UNFERMENTED cocoa beans? How does this change during fermenting?

Answer 21

sucrose

invertase converts to glucose, fructose

Question 22

Why is the conversion of sugars during cocoa fermentation significant?

Answer 22

sucrose NOT reducing sugar (no browning)

glucose and fructose are reducing, can contribute to browning/flavor during roasting

Question 23

What gives fresh beans their purple hue, and what happens to those compounds during the ferment?

Answer 23

anthocyanins
broken down by GLYCOSIDASES -> bleaching, more reducing sugars
(lose purple color, gain browning/flavor)

Question 24

Is a purple fermented cocoa bean acceptable?

Answer 24

No (sign of poor ferment)

Question 25

In the late aerobic phase of cocoa fermentation, significant ___ enzyme activity occurs. What is the major one?

Answer 25

oxidative

PPO

Question 26

When does PPO become activated in cocoa ferment? What does this cause?

Answer 26

final stages of ferment, when air can penetrate
oxidize polyphenols in bean (enzymatic browning)
reduce astringency

Question 27

The main polyphenol classes in cocoa:

Which is responsible for browning?

Answer 27

Leucocyanidins

Catechins (browning)

Question 28

True/False: polyphenols are undesirable in cocoa

Answer 28

False: antioxidant properties, may want to leave some in chocolate

Question 29

What does the drying of cocoa beans accomplish?

Answer 29

reduce moisture from 50% to 8%

prevent mold, longer storage life

Question 30

How does storage affect cocoa beans?

Answer 30

can be good: slow oxidation/acid loss -> enhance quality

too long -> staling

Question 31

What is a SCOBY? What is it used for?

Answer 31

symbiotic culture of bacteria and yeast
combination of LAB, yeast, AAB in cellulose matrix
for making kombucha

Question 32

What organism type in the SCOBY is responsible for making the cellulose?

Answer 32

AAB

Question 33

True/False: the finished kombucha is non-alcoholic

Answer 33

true; ethanol concentrations low (converted to acetic acid)

Question 34

Why is S. cerevisiae usually used for kombucha? Why might alternative yeasts be used?

Answer 34

most efficient

other yeasts -> different flavor profiles, complexity

Question 35

The main microbe type present in the final kombucha is _____, including ___ and ___.

Answer 35

AAB

acetobacter, gluconobacter

Question 36

What species produces the cellulose? How do the other species in the SCOBY contribute?

Answer 36

komagateibacter xylinus (AAB)
yeast break down sucrose -> glucose + fructose (needed as materials)

Question 37

K. xylinus synthesizes _____, which is used to polymerize into ____.

Answer 37

UDP-glucose

B-1,4 glucan chains (cellulose)

Question 38

Where is the cellulose produced in K. xylinus?

Answer 38

extruded out of cell pores (complex terminals)

extracellular fibrils attached to membrane -> assemble to macrofibrils

Question 39

Why is there delay in forming the SCOBY?

Answer 39

bacteria can use dissolved oxygen; only form raft when need to stay afloat

Question 40

Can a SCOBY grow without limit?

Answer 40

NO, too thick -> insufficient nutrients/oxygen -> dormant

Question 41

True/False: all the fermentation organisms in kombucha are contained in the SCOBY

Answer 41

false; some are dispersed in liquid (dormant but can revive)

Question 42

Describe the basic process of making kombucha (backslopping).

Answer 42

use dormant sessile microbes -> incubate at room temp, aerobic -> form SCOBY
(or use preexisting SCOBY)
rinse and add to tea + sugar
ferment aerobically 7-14 days

Question 43

What is the period of greatest safety risk when making kombucha?

Answer 43

time between after boiling until pH drops below 4.2 (risk of pathogen or other bacteria contamination, outgrow SCOBY)

Question 44

True/False: molds are not a health concern in kombucha

Answer 44

false

Question 45

What are the chemical safety concerns with kombucha?

Answer 45

overferment -> too acidic -> possible leaching of chemical contaminants from container

interfere with medications (affect acidity of stomach)