Fruits and vegetables - Purdue University and vegetables Plant parts we eat (APK) ... Fruit and...
Transcript of Fruits and vegetables - Purdue University and vegetables Plant parts we eat (APK) ... Fruit and...
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Fruits and vegetables
Plant parts we eat (APK)
• See page 247, Lecture Notes.• We eat
– Leaves• Cabbage• Lettuce• Spinach
– Stems• Asparagus• Celery
Plant parts we eat
– Bulbs• Garlic
• Onion
– Roots• Beet
• Carrot
• Radish
• Sweet potato
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Plant parts we eat
– Tubers• Potato
– Flowers• Broccoli• Broccoli
• Cauliflower
– Fruits• Tomato
• Pepper
• Cucumber
– Seeds -- beans, corn, peas, soybeans
Fruit and vegetable characteristics to preserve
• In preparation, processing, or preservation of fruit and vegetables we want to preservep– Color
– Flavor
– Texture
– Nutrient value
Plant tissue types
• Dermal– Outer covering, usually rich in waxes and
lipids (cutin). Protects and waterproofs dj t tiadjacent tissue.
• Vascular – Xylem
• Transports water from roots to leaves
– Phloem• Transports food from leaves to roots for storage
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Plant tissue types
• Ground tissue– Parenchyma
• Most abundant
U diff ti t d• Undifferentiated
– Collenchyma• Strength cells
• Strings on green beans and celery
– Sclerenchyma• Even stronger than collenchyma
• Strings in green beans, grittiness in pears
Parenchyma
Image courtesy of Plants and Society, Levitin and McMahon(www.life.umd.edu/pbio100/contact1.html)
Parenchyma
Middle lamella is fluorescent due to staining
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Collenchyma
Image courtesy of Plants and Society, Levitin and McMahon(www.life.umd.edu/pbio100/contact1.html)
Sclerenchyma
Image courtesy of Plants and Society, Levitin and McMahon(www.life.umd.edu/pbio100/contact1.html)
Plant cell
Middlelamella
Vacuole
Image courtesy of Beginner’s guide to Molecular Biology (www.res.bbsrc.ac.uk/molbio/guide/cell.html)
Amyloplast
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Plant cell wall polymers
• Cellulose
• Hemicellulose• Hemicellulose
• Lignin
Cellulose
Hemicellulose
• Non-cellulose polymers utilizing the monosaccharides shown below
Image courtesy of www.eng.rpi.Edu/dept/chem-eng/Biotech-Environ/FUNDAMNT/hemicel.htm
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Cell wall xylan
O
O
OH
O
O
OH
O OH
OH
O O
OH
H H
H
A cell wall xylanBeta-1,4-linkage
LigninA polymer comprised of phenylpropane molecules such as those shown below. Provides strength and woodiness toplant materials when it occurs in large concentration.
Lignin monomers
Image courtesy of www.eng.rpi.edu/dept/chem-eng/Biotech-Environ/FUNDAMNT/lignin.html.
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Proposed lignin sub-structure
Image courtesy of www.eng.rpi.edu/dept/chem-eng/Biotech-Environ/FUNDAMNT/lignin.html.
Vacuole
• Contains the cell sap. Basically a drop of water contained in the cell in which various substances are dissolved.– Tannins
– Sugars
– Salts
– Organic acids
– Flavanoids
Plant acids
• Malic acid– Found in apples and many other fruits and
vegetables
• Citric acid– Main acid in citrus fruits, many berries,
pineapple
• Oxalic– Spinach, rhubarb (especially the leaves)
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Silly stuff
• Dr. James van Meeter, speaking in 1830 to a crowd in Salem, Massachusetts, about Colonel Robert Gibbon Johnson, ,who was going to publicly eat a tomato…
Silly stuff• "The foolish colonel will foam and froth at the
mouth and double over with appendicitis. All that oxalic acid, in one dose, and you're dead. If the Wolf Peach (tomato) is too ripe and warmed by the sun he'll be exposing himself towarmed by the sun, he ll be exposing himself to brain fever. Should he, by some unlikely chance, survive, I must warn him that the skin ... will stick to his stomach and cause cancer."
Plant acids
• L-tartaric– Grapes
• Benzoic• Benzoic– Cranberries--a natural preservative
• Shikimic– Intermediate in secondary metabolism
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Plant acids
O
O
O
O
H
OH
OH
O O
OO
HO
O HH
OO
O O
H HO
Hm a l i c a c i d
H
c itr ic a c idoxalic acid
O
O
O
O
O
O
H
H
H
H
L-tartaric acid
OOH
b e n z o ic a c id
OO
O
O
O
H
H
HH
s h ik im ic a c id
Chlorophyll
Chlorophyll/pheophytin
acid
h t
chlorophyll pheophytin
heat
Mg++
Images courtesy of NYU/ACF Scientific Visualization Laboratory(www.nyu.edu/pages/mathmol)
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Chlorophyll in broccoli
Carotenoids
• These are the most stable class of pigments in fruits and vegetables– Carotene--orangeCarotene orange
• Carrots
– Lycopene--red• Tomato
– Xanthophylls--yellow• Corn
Carotenoids
O
H
v i t a m i n A
b e ta -c a ro te n e
lyc o p e n e
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Carotene in carrots
Flavonoids
O+
B a s ic r in g s t r u c tu r e f o ra n t h o c y a n in p ig m e n t s
Anthocyanin reactions
OO
O
O
OH
H
H
H
-H+
+H+O
OH
OO
O
O
O
OH
flavylium or oxonium ion (red)
Anhydrobase (violet)
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Anthocyanin reactions
OO
O
O
O
H
H
Na
+Na+
-Na+
OH
H
Anhydrobase (violet)OO
O
O
O
OH
HH
Na
Sodium salt of the anhydrobase(blue)
Anthocyanins in red cabbage
Anthoxanthins in onions
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Betalins (beet pigments)
O
O
O
OO
N
O
H
H
O
H+N
O
NO
O
H
H
H
H
O
O
H
O H
b e ta lin
Enzymatic browning
OH
OH
O
Opolyphenoloxidase
+ H 0
Cell wall phenolic
Ortho-quinone
1/2 O2
+ H20
Enzymatic browning
Image courtesy of Robertson and Christiansen (www.orst.edu/instruct/nfm425/phenolic/index.html)
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Browning inhibition
• Remove (or reduce) enzyme activity– Heat
– AcidAcid
• Remove oxygen– Vacuum pack
– Inert gas pack (He, Ar, Carbon dioxide)
Browning inhibition
• Remove substrate– Genetic breeding program
• Use antioxidants• Use antioxidants– Vitamin C is commonly used
• Physical barrier– Cover with heavy syrup, as in freezing
Sulfur compounds -- garlic
SO
N
OOH
H
H2
SO
Sallinase
w ater
Step one
O O
(+)-S-allyl-L-Cysteinesulfoxide (alliin)
Diallyl thiosulfinate(allic in)
O
O
O
H2
pyruvic acid
NH3
+
+
w ater
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Sulfur compounds -- garlic
S
SS
S2
Step two
SO
D ia lly l th io s u lf in a te(a ll ic in )
SO
SO
d ia lly l d is u lfid e(ty p ic a l g a r lic o d o r)
a lly l th io s u lf in a te
+
Sulfur compounds -- onion
SO
OO
N
H
H
H
SH
O
propenylsulfenic acid
enzyme
water
(+)-S-(pro-1-enyl)-L-Cysteinesulfoxide
p p y(lachrymatory factor)
O
O
O
H
pyruvic acid
NH3
+
+
Sulfur compounds -- cabbage
S
O
OO
O
O
H
H
HH
Nmyrosinase
N
S
OS
O
O
O
K
sinigrin
N
Sallyl isothiocyanate(a mustard oil)
C6H12O6
KHSO4
+
+
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Changes in fruits and vegetables on ripening
• Color– Green of chlorophyll may give way to other
colors
• Texture– Goes from hard to tender-crisp to mushy.
Principally a function of changes in the middle lamellar pectic substances.
Changes in fruits and vegetables on ripening
• Flavor
Starch Sugarbanana
sweetsweetcorn
Tannins decrease on ripening
Acids generally decrease on ripening(except for citrus fruits)
Pectic substances
Protopectin Pectinicacid
Pectic acid
Underripe Ripe OverripeInsoluble Colloidal Soluble
No gel Gel No gelLots ofmethyl
Less methyl Almost nomethyl
Hard Optimum Mushy
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Ripening
• To speed ripening– Treat with ethylene (C2H4)
• To slow ripening– Store in modified atmosphere (low in
oxygen, high in carbon dioxide)
Ethylene treatment
Air only Air + lowconcentrationof ethylene
Ethylene treatment
Air only Air + lowconcentrationof ethylene
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Ethylene treatment
Air only Air + lowconcentrationof ethylene
Controlled (modified) atmosphere storage
Nitrogen 78%Oxygen 21%Carbon dioxide
95% Carbon dioxide5% Oxygen
<0.04%
Controlled (modified) atmosphere storage
Nitrogen 78%Oxygen 21%Carbon dioxide
95% Carbon dioxide5% Oxygen
<0.04%
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Controlled (modified) atmosphere storage
Nitrogen 78%Oxygen 21%Carbon dioxide
95% Carbon dioxide5% Oxygen
<0.04%
Controlled (modified) atmosphere storage
Nitrogen 78%Oxygen 21%Carbon dioxide
95% Carbon dioxide5% Oxygen
<0.04%
Controlled (modified) atmosphere storage
Nitrogen 78%Oxygen 21%Carbon dioxide
95% Carbon dioxide5% Oxygen
<0.04%