NUSCTX 108A MIDTERM 2 EXAM
QUESTIONS AND ANSWERS
Chloroplasts - ANSWER-Chlorophyll, photosynthesis
Chromoplasts - ANSWER-Carotenoids (yellow, red, orange pigment)
Leucoplasts - ANSWER-Produce and store starch
Vacuole - ANSWER-Large portion of cell, water, nutrients, organic acid, flavonoids
(pigment)
Responsible for texture of fresh fruit and vegetables
Cellulose - ANSWER-Major carbohydrates in cell wall
Structural component
Glucose polymer
Cannot be digested (insoluble fiber)
Broken down at high heat or with chemical treatment
Hemicellulose - ANSWER-Strengthens cellulose cross-links
Polymer of pentoses and hexose sugars
Cooking partially dissolves
Pectin & Pectic Substances - ANSWER-Cement, binds cell wall component
Also found in middle lamella
Not digestible in human gut
Changes during heating and plant ripening
Extracted after long cooking (breakdown with heat)
Chlrophyll - ANSWER-Predominant pigment in plants
Degrades with heating and chemicals
What is the difference between chlorophyll a and b? - ANSWER-a has methyl group,
b has aldehyde group, a is more abundndant
Chlorophyll Alterations - ANSWER-Decrease intercellular air space (IAS)
Phytyl tail (hydrophobic) removed, driven by chlorophyllase
Magnesium replaced
Lose of both Mg2+ and phytyl tail
Increasing pH (neutralize organic acid and Mg cannot be replaced)
What happens when Phytyl tail (hydrophobic) is removed in chlorophyll? - ANSWER-
Chlorophyllide (water-soluble) is formed
What happens when Magnesium is replaced in chlorphyll? - ANSWER-H+ replaces
in porphyrin ring
Happens at increased temp and facilitated by low pH
Pheophytin a and Pheophytin b is formed
, What happens when Mg2+ and phytyl tail is lost in chlorophyll? - ANSWER-
Pheophorbide is formed
What does increasing pH in chlorophyll do? - ANSWER-Chlorophyllin is formed
Carotenoids - ANSWER-Isoprene polymers
Chemically more stable than chlorophyll
With heat, less intense color
Higher pH, may be brighter but softer
Carotene
Xanthophylls
Carotene - ANSWER-Only carbon and hydrogen
Vitamin A activity (provitamin A)
Β-carotene is the most prominent
Xanthophylls - ANSWER-Carbon, hydrogen and oxygen
NOT provitamin A
Enzymatic Browning - ANSWER-Phenolic compounds (polyphenol)
Natural enzyme in plant (polyphenol oxidases - PPO)
Due to Oxygen
Forms melanin
How do you prevent Enzymatic Browning? - ANSWER-Eliminate oxygen
Add acid to prevent enzyme activity
Reduce time after cutting/temperature
Maturation of fruits and vegetables lead to? - ANSWER-More cellulose,
hemicellulose and lignin
Less protopectin
What does gelatin do? - ANSWER-Bind and trap water
What is gelatin influenced by? - ANSWER-pH and salt concentration
At what rate of cooling forms a more stable gel? - ANSWER-slower rate
Does water or milk make more stable gel? - ANSWER-milk
What are factors of gel stability? - ANSWER-Rate of cooling
Nature of disperse phase
pH value of the system
Sugar concentration
Agitation
Temperature/Enzymatic hydrolysis
Gel is most stable at which pH range? - ANSWER-5-10
QUESTIONS AND ANSWERS
Chloroplasts - ANSWER-Chlorophyll, photosynthesis
Chromoplasts - ANSWER-Carotenoids (yellow, red, orange pigment)
Leucoplasts - ANSWER-Produce and store starch
Vacuole - ANSWER-Large portion of cell, water, nutrients, organic acid, flavonoids
(pigment)
Responsible for texture of fresh fruit and vegetables
Cellulose - ANSWER-Major carbohydrates in cell wall
Structural component
Glucose polymer
Cannot be digested (insoluble fiber)
Broken down at high heat or with chemical treatment
Hemicellulose - ANSWER-Strengthens cellulose cross-links
Polymer of pentoses and hexose sugars
Cooking partially dissolves
Pectin & Pectic Substances - ANSWER-Cement, binds cell wall component
Also found in middle lamella
Not digestible in human gut
Changes during heating and plant ripening
Extracted after long cooking (breakdown with heat)
Chlrophyll - ANSWER-Predominant pigment in plants
Degrades with heating and chemicals
What is the difference between chlorophyll a and b? - ANSWER-a has methyl group,
b has aldehyde group, a is more abundndant
Chlorophyll Alterations - ANSWER-Decrease intercellular air space (IAS)
Phytyl tail (hydrophobic) removed, driven by chlorophyllase
Magnesium replaced
Lose of both Mg2+ and phytyl tail
Increasing pH (neutralize organic acid and Mg cannot be replaced)
What happens when Phytyl tail (hydrophobic) is removed in chlorophyll? - ANSWER-
Chlorophyllide (water-soluble) is formed
What happens when Magnesium is replaced in chlorphyll? - ANSWER-H+ replaces
in porphyrin ring
Happens at increased temp and facilitated by low pH
Pheophytin a and Pheophytin b is formed
, What happens when Mg2+ and phytyl tail is lost in chlorophyll? - ANSWER-
Pheophorbide is formed
What does increasing pH in chlorophyll do? - ANSWER-Chlorophyllin is formed
Carotenoids - ANSWER-Isoprene polymers
Chemically more stable than chlorophyll
With heat, less intense color
Higher pH, may be brighter but softer
Carotene
Xanthophylls
Carotene - ANSWER-Only carbon and hydrogen
Vitamin A activity (provitamin A)
Β-carotene is the most prominent
Xanthophylls - ANSWER-Carbon, hydrogen and oxygen
NOT provitamin A
Enzymatic Browning - ANSWER-Phenolic compounds (polyphenol)
Natural enzyme in plant (polyphenol oxidases - PPO)
Due to Oxygen
Forms melanin
How do you prevent Enzymatic Browning? - ANSWER-Eliminate oxygen
Add acid to prevent enzyme activity
Reduce time after cutting/temperature
Maturation of fruits and vegetables lead to? - ANSWER-More cellulose,
hemicellulose and lignin
Less protopectin
What does gelatin do? - ANSWER-Bind and trap water
What is gelatin influenced by? - ANSWER-pH and salt concentration
At what rate of cooling forms a more stable gel? - ANSWER-slower rate
Does water or milk make more stable gel? - ANSWER-milk
What are factors of gel stability? - ANSWER-Rate of cooling
Nature of disperse phase
pH value of the system
Sugar concentration
Agitation
Temperature/Enzymatic hydrolysis
Gel is most stable at which pH range? - ANSWER-5-10
