Fruit Composition and Preservation

Flashcards on Fruit Composition and Preservation

Carbohydrates in Fruits

Fruits are high in carbohydrates, starting as starch and converting to monosaccharides and disaccharides during ripening.

Fats in Fruits

Fruits are generally low in fat, except for avocados, coconuts, and olives.

Proteins in Fruits

Fruits have a low protein content.

Water Content of Fruits

Fresh fruits contain 75-95% water.

Vitamin C in Fruits

Found in citrus fruits, tomatoes, cantaloupe, and strawberries.

Beta Carotene in Fruits

Found in yellow/orange colored fruits.

Iron in Fruits

Found in berries, dried plums, raisins, apricots, dates, and figs.

Calcium in Fruits

Found in leaves, citrus fruits, and figs.

Potassium in Fruits

Found in bananas, avocado, dates, figs, oranges, plums, prunes, melons, and raisins.

Carotenoids

Pigments that give fruits a yellow/orange color.

Anthocyanin

Pigments that give fruits a red/blue color.

Anthoxanthin

Pigments that give fruits a white color.

Chlorophylls

Pigments that give fruits a green color.

Citric Acid

Organic acid found in citrus fruits which creates a tart flavor.

Malic Acid

Organic acid found in apples and cherries which creates a tart flavor.

Tartaric Acid

Organic acid found in grapes which creates a tart flavor.

Tannins

Phenolic compounds found predominantly in unripe fruits, causing a bitter/astringent flavor.

Enzymatic Browning

The process where phenolic compounds in fruits turn brown when exposed to oxygen.

Fruits and enzymatic browning

Apples, apricots, avocados, bananas, cherries, dates, grapes, nectarines, papayas, peaches, persimmons, pears, and strawberries are fruits that contain phenolic compounds and will turn brown.

Oxygen, Enzyme (polyphenol oxidases), Phenolic Compound

Substances are required for enzymatic browning.

Methods to Slow Enzymatic Browning

Denaturing enzymes, adding acid/reducing pH, lowering temperature, and blocking exposure to oxygen.

Pectic Substances

Protopectin, Pectin, and Pectic acid.

Pectin

General term describing peptic polysaccharides which act as a cementing substance between cell walls and are responsible for plant structure.

Climacteric Fruit

Fruit that continues to ripen after being harvested, characterized by an increased rate of respiration and a spike in ethylene (e.g., peaches, bananas, apples, and avocados).

Non-Climacteric Fruit

Fruit that needs to be fully ripened before being harvested and does not have a peak of ethylene production or respiration during ripening (e.g., cherries, grapes, strawberries, and blueberries).

Protopectin

Present in immature fruit.

Pectic Acid

Present in overripe fruit.

Osmosis: Hypotonic Solution

Water is driven into the cells, causing cell enlargement and swelling. Keeps fruit crisp and turgid.

Osmosis: Hypertonic Solution

Water driven out of the cell, resulting in syrupy, soft, mushy fruit.

Effects of Cooking Fruit

Converts protopectin to pectin, degrades cellulose and hemicellulose, and denatures cell membrane proteins.

Simple Diffusion (Cooking Fruit in Water)

Solutes move from area of high concentration (fruit cells) to area of low solute concentration (water), resulting in a loss of sweetness.

Simple Diffusion (Cooking Fruit in Sugar)

With solute concentration higher outside cells, solutes move into the cell. With equilibrium, get water leaving the cells, resulting in sweeter fruit & better texture.

Pectin Gel Formation Requirements

Sugar (hygroscopicity, preservative, flavor) and Acid (helps extract pectin, flavor).

Preservation - Drying

Water decreases, then carbohydrate content and calories concentrate.

Freezing Advantages

Convenience, availability, taste, preservation of color, and good nutrient content.

Freezing Disadvantages

Ruptures cell wall, texture is flabby when thawed, requires defrosting in refrigerator, ice crystals may remain.