15 Fruits and Vegetables

Ripening Cont'd

Once the fruit is picked, cell division (synthesis) stops but numerous physiological changes continue during storage.

Antisense RNA

Prevents production of ripening compound polygalaturonase (digests pectin in cell wall resulting in fruit softening & loss of resistance to rotting)

Ethylene Increases...

--Amylase: breakdown makes sweeter; starch to sugar --Pectinase: causes cell walls to breakdown & create a softer product --Enzymes that breakdown chlorophyll: causes color change

Commercial Methods to Control Ripening

-SmartFresh Technology: 1-MCP inhibits ripening process by blocking ethylene receptor -Low Temperatures -Control Gases: decrease oxygen & increase carbon dioxide = a decrease ethylene -Irradiation: inactivates enzymes

Reactions with Chlorophyll: Canning

-Lose nice, bright green pigment. This method ultimately leads to an olive/drab color. Water soluble, mushy, gross color

Examples of Carotenoids: Alpha-Carotene

Carrots

Rate of Respiration

Directly related to the perishable character of fruits and veggies. Those that have a rapid rate of oxygen consumption and carbon dioxide production are more perishable. Rate of respiration reaches maximum right before ripening. So, ripening is a process in fruits that causes them to become more palatable, fruit becomes sweeter and less green and becomes softer.

Changes due to Ripening

Even though acidity of fruit increases as it ripens, it doesn't make it more tart. Produces sugars and creates a taste sweeter. Color change is observed because of the breakdown of chlorophyll.

Ethylene: Good or Bad?

Good - ripens fruit commercially; can help while transferring the fruit to continue maturing Bad - yellowing of vegetables due to loss of chlorophyll

Exceptions to Ripening Prevention at Low Temperatures

Potatoes, Apples, Carrots

Types of Tissues

--Dermal: protective covering; skin or rind/ changes but always provides protection function --Vascular within Dermal Tissue: transports nutrients (food & water) & waste products; composed of xylem - moves water and philoum - transports organic matter in solution. Ground system - edible portion & consists of parenchyma cells --Parenchyma: ground tissue, makes up leaves, roots, pulps, & pits of stems. Makes up most of edible portion of fruits & veggies

Composition of Plant

-75%-90% water -1%5-25% carbs: sugar, starches (corn, peas) , celluloses, pectins, hemicelluloses -Low in protein & fat: except avocados & olives -Minerals: low in Ca, P, Fe (actually contain a lot of Ca but it's bound & not bioavailable to us) -Vitamins: low in B, high in C (citrus fruits & also a good source of folate) - red/yellow/orange bell peppers -ß-carotene: yellow fruits; sweet potatoes

Examples of Ethylene

-Apples & pears produce ethylene during ripening. It softens, changes their texture, and sweetens -Blueberries & cherries don't produce much ethylene & it doesn't affect their ripening process

Prevention of Ripening

-Avoid mechanical damage to cell -Protect from oxygen & denature/inhibit enzymes : antioxidant, salt/sugar coating, acid to cut surface, sulfur dioxide & sulfites

Climacteric Fruits

-Can ripen after harvest --bananas, peaches, pears, apples, tomatoes, plums, papaya, mango, & some melons

Non-Climacteric Fruits

-Can't ripen after harvest --citrus, grapes, strawberries, cherries, pineapples, berries, some melons

Carotenes vs. Xanthophylls

-Carotenes: hydrocarbon -Xanthophylls: CHO molecule

Enzymatic Browning

-Caused by polyphenoloxidases -Primary affects caused by anthoxanthins because of light color -Substrates: polyphenol groups, or tyrosine & react with oxygen to produce brown color -Other colors: Potatoes: first a reddish color, then a grayish black

Chlorophylls

-Chlorophyll A: CH3 (R group) - most abundant in nature, blue/green color -Chlorophyll BL CHO (R group) - yellow/green color (in stalks) -Broccoli is a 50:50 mix of both chlorophylls -Chlorophyll is generally hydrophobic because of long carbon chain attached. If it is cut off, it becomes water soluble. When heated in water, intensification of chlorophyll green color is noted. This change is followed by another change to an olive color

Reactions with Chlorophyll: Heat + Acid

-Chlorophyll loses magnesium & causes green/gray color change

Pigments

-Colors due to pigments that absorb & reflect light -All contain conjugated double bonds -Chlorophyll also contains metal coordinated porphyrin rings -Resonance

Xanthophylls

-Contain CHO, oxygenated hydrocarbons, yellow-orange, plant pigment deposited in egg yolk gives a yellow color. -Generally more yellow/orange while carotenes are more red/orange. Xanthophylls make up corn.

Reactions with Chlorophyll: Base

-Dissolves hemicellulose. Makes veggies tender & mushy. Actually get a brighter green color & eventually get chlorophyllin color

Ripening

-Flavor: acids & sugars -Color: breakdown of chlorophyll & synthesis of carotenoids, anthocyanins -Textures: softening

Carotenes

-Hydrocarbons, some have vitamin A activity -Lycopene: most abundant, red pigment. In apricots, tomatoes, papaya, & grapefruit. Anti-oxidant & resistant to heat -a-Carotene = yellow/orange pigment -b-Carotene = Vitamin A activity, orange, in carrots

Chlorophyll and Base

-Increases retention of chlorophyll. Pigment change when pH reaches about 7, when adding base. Lose phytol group & becomes water soluble & causes mushiness -With correct amount of alkaline product added, only enough to neutralize, formation of chlorophyllin can be avoided

Retain Green Color in Veggies?

-Keep cooking time to a minimum, cook with lid of pot off, or boil water first. All of these ideas can help prevent undesirable color change -Pickles and canned green beans are examples of ugly color

Anatomy

-Mitochondria: produces ATP -Vacuole: holds flavor components; flavinoid pigments & protein. Also holds 90% of cellular water -Golgi: combines simple molecules to make more complex molecules. Stores them or sends them out for use "post-office" of cell -Starch-storing Plasmid: where starch is stored. Made up of chloroplasts & glucoplasts

Composition of Plants Cont'd

-Organic acids (in vacuole): citric -> main acid in citrus fruits & tomatoes; malic -> apples & peaches; malic & tartaric -> grapes

Inactivated Enzymes by Irradiation

-Pectin Esterase: softens fruit -Protopectinase: softens fruit -Cellulose & Hemicellulose: increases sweetness -Amylase: increases sweetness -Invertase: increases sweetness -Phosphorylase: increases sweetness

Carotenoids

-Polymers of isoprene groups -Color Ranges yellow-orange-red -Soluble -Types: Carotenes & Xanthophylls -Reactions: easily oxidized by light, oxygen, metals; some trans -> cis with cooking; lighter color; blanching somewhat protects color

Reactions with Chlorophyll: Blanching

-Put veggies into boiling, then ice-water. Dry out and put in freezer. Cold temp denatures enzyme that causes ripening. Result is a bright green color because of expulsion of air from intercellular spaces. Color is retained during freezing and subsequent boiling when preparing the veggies.

Carotenoids Cont'd

-Some have anti-oxidant properties -But oxidation can cause some color loss. Double bonds are susceptible to oxidation -Can change color during cooking because double bonds are typically in trans formation (resonance, more conjugated double bonds, most intense color) but some change to cis configuration with heat (bend in double bond, less conjugation, less intense color)

Ripening: Ethylene

-small hydrocarbon gas that is naturally occurring. it's responsible for the changes in texture, softening, color & other processes involved in ripening.

pH Variances in Fruit

2.0-2.2 - lemons & limes 2.7 - cranberries 3.0-3.4 - current, g berries, prunes, apples, grapefruit, blackberries, & strawberries 3.5-3.9 - peaches, raspberries, oranges, pears 6.0 - bananas, figs, watermelon

Flav'r Sav'r Tomato

Tomato that suppressed gene expression of the protein, and halted the ripening process. Could you picked once ripe and shipped without damaging produce. Never made it to shelves due to consumer wariness

Carotenoids and Anthocyanins

White pigment on older fruit and veggies

Examples of Carotenoids: Beta-Carotene

pink grapefruit, peaches, pineapple, navel oranges, italian prunes, muskmelons, tomatoes, red-bell peppers, green-bell peppers, carrots

Examples of Carotenoids: Lycopene

pink grapefruit, watermelon, peaches, tomatoes, carrots