Cocoa, Tea, Coffee Flashcards
The 2 common species of coffee bean:
Coffea arabica (South and central America, Africa) Coffea robusta (Africa, Asia)
What are the 3 methods of coffee processing? Describe them
- Dry process: directly dry entire coffee bean -> NATURAL COFFEE
- Wet process: remove fruit pulp through fermentation -> wash off -> dry -> WASHED COFFEE
- Honey process: fruit mostly removed, some mucilage remain -> dry -> HONEY COFFEE
What is the purpose of the ferment step in washed coffee?
- degrade fruit pulp/mucilage (make water soluble) for easy removal
- develop flavor/aroma
What are common microbes found during coffee bean fermentation?
Escherichia, Enterobacter
Bacillus, Fusarium, Penicillium, Aspergillus
Erwinia dissolvens (from KONA COFFEE)
How long does the coffee bean wet ferment usually last?
24-90 hrs
Does fermentation occur with naturally dried coffee?
Yes; pulp and mucilage still present, fermented by yeast, bacteria, molds
True/False: starter cultures are used in coffee bean fermentation
False; not commercially used, little research
Which bean variety takes longer for the demucilagination process? Why? What other factors have an effect?
robusta
thicker layer
temperature, altitude
___ is an important step in preparing the final coffee bean. What are the common industrial conditions?
roasting
90s-6min at 200-250C (rotary drum)
True/False: all cocoa beans are fermented. Why or why not?
True.
need to remove pulp, develop flavor/color/aroma
What is fermented in the cocoa bean pod?
pulp surrounding cocoa bean (rich in carbs)
What organism grows first in the cocoa bean ferment? Why?
yeast
favorable conditions: anaerobic, high in sugar, pH 3-4
What occurs in the cocoa pod composition during the yeast growth period?
ethanol and CO2 produced
sugars decrease
pectinolytic enzymes -> degrade pectin
What creates favorable conditions for LAB to grow in cocoa?
yeast will create degrade pectin -> permeable to allow air in -> AEROBIC CONDITIONS
What organism is present at the end of the cocoa bean ferment? What allows it to grow?
AAB
more breakdown of pulp -> more air
ethanol made by yeast, organic acids made by LAB
what is the cause of the end of cocoa fermentation?
AAB make acetic acid -> diffuse into bean -> BEAN DEATH
At the beginning of the cocoa ferment, glucose is used by ____. Fructose is used by: ______. Citric acid can be used by: ___.
yeast (best competitor); some used by LAB
LAB
Some LAB (citrate positive): use as co-substrate
What organism is NOT present in the beginning of the ferment? why?
AAB anaerobic conditions (stored in heaps/boxes)
How is a cocoa bean fermentation usually set up?
box fermentation most common
stacked boxes containing beans
every 24 hrs, move to lower box -> collect at end
Why is bean death important in cocoa fermentation?
prevent germination (which uses up nutrients in bean) flavor development (enzymes/substrates in bean react after death -> flavor precursors)
What is the main sugar in UNFERMENTED cocoa beans? How does this change during fermenting?
sucrose
invertase converts to glucose, fructose
Why is the conversion of sugars during cocoa fermentation significant?
sucrose NOT reducing sugar (no browning)
glucose and fructose are reducing, can contribute to browning/flavor during roasting
What gives fresh beans their purple hue, and what happens to those compounds during the ferment?
anthocyanins
broken down by GLYCOSIDASES -> bleaching, more reducing sugars
(lose purple color, gain browning/flavor)
Is a purple fermented cocoa bean acceptable?
No (sign of poor ferment)
In the late aerobic phase of cocoa fermentation, significant ___ enzyme activity occurs. What is the major one?
oxidative
PPO
When does PPO become activated in cocoa ferment? What does this cause?
final stages of ferment, when air can penetrate
oxidize polyphenols in bean (enzymatic browning)
reduce astringency
The main polyphenol classes in cocoa:
Which is responsible for browning?
Leucocyanidins
Catechins (browning)
True/False: polyphenols are undesirable in cocoa
False: antioxidant properties, may want to leave some in chocolate
What does the drying of cocoa beans accomplish?
reduce moisture from 50% to 8%
prevent mold, longer storage life
How does storage affect cocoa beans?
can be good: slow oxidation/acid loss -> enhance quality
too long -> staling
What is a SCOBY? What is it used for?
symbiotic culture of bacteria and yeast
combination of LAB, yeast, AAB in cellulose matrix
for making kombucha
What organism type in the SCOBY is responsible for making the cellulose?
AAB
True/False: the finished kombucha is non-alcoholic
true; ethanol concentrations low (converted to acetic acid)
Why is S. cerevisiae usually used for kombucha? Why might alternative yeasts be used?
most efficient
other yeasts -> different flavor profiles, complexity
The main microbe type present in the final kombucha is _____, including ___ and ___.
AAB
acetobacter, gluconobacter
What species produces the cellulose? How do the other species in the SCOBY contribute?
komagateibacter xylinus (AAB) yeast break down sucrose -> glucose + fructose (needed as materials)
K. xylinus synthesizes _____, which is used to polymerize into ____.
UDP-glucose
B-1,4 glucan chains (cellulose)
Where is the cellulose produced in K. xylinus?
extruded out of cell pores (complex terminals)
extracellular fibrils attached to membrane -> assemble to macrofibrils
Why is there delay in forming the SCOBY?
bacteria can use dissolved oxygen; only form raft when need to stay afloat
Can a SCOBY grow without limit?
NO, too thick -> insufficient nutrients/oxygen -> dormant
True/False: all the fermentation organisms in kombucha are contained in the SCOBY
false; some are dispersed in liquid (dormant but can revive)
Describe the basic process of making kombucha (backslopping).
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
What is the period of greatest safety risk when making kombucha?
time between after boiling until pH drops below 4.2 (risk of pathogen or other bacteria contamination, outgrow SCOBY)
True/False: molds are not a health concern in kombucha
false
What are the chemical safety concerns with kombucha?
overferment -> too acidic -> possible leaching of chemical contaminants from container
interfere with medications (affect acidity of stomach)
