exam 3 Flashcards
(63 cards)
Phytochemicals
non nutritive components in plants considered to have positive health benefits (flavonoids, carotenoids, tocopherols)
vegetable pigments
responsible for color, evidence of functional food properties
carotinoids
fat soluble pigment that is a yellow-orange color
- carotenoids (alpha, beta, gamma): yellow-orange (carrots)(beta carotene converted to vitaminA in body)
- lycopene: red-orange (tomato)
- xanthophyll: yellow (pineapple)
flavonoid pigments
water soluble pigments, flavones
- betalains: purplish-red (beets)
- anthoxanthin: creamy to white (cauliflower)
- anthocyanin: red-blue (eggplant, radish)
cell wall
fibrous
- cellulose and hemicellulose
- pectin compounds and hemicellulose
- lignin
- vegetable gums
cellulose and hemicellulose
found in greater proportion in skin/peel, protective layer secretes waxy cutin (protects the plant)
pectin compounds and hemicellulose
found within ad between cell walls, give firmness and elasticity to plant tissue
lignin
made form polymers and phenolic alcohols, increase in concentration as plant matures
vegetable gums
polysaccharides that can absorb water, added to processed foods to increase viscosity
parenchyma cell
thin flexible cell walls, major food source of plant structure, carries out most of plant’s metabolism (photosynthesis, storage), contains cytoplasm and organelles
structure of parenchyma cell
- cytoplasm: sticky gel-like compound found within the cell wall
- plastids: surrounds and bathe the organelles
- compounds are responsible for plant’s starch content, color, water, volume, flavor
types of plastids
- chloroplasts: contain chlorophyll, provide green color of plants
- chromoplasts: contain carotene or xanthrophyll pigments, provide orange-yellow color of plants
- leucoplasts: location of starch storage and some water, major digestible portion of plant
vacuole
an organelle in parenchymal cell that stores water, anthocyanin (red-blue pigment), flavor compounds (sugar, salt, organic acids); responsible for turgor
turgor
term applied to describe the firmness of a cell based upon its water content
- relates to juiciness
- crunch or snap of raw vegetables
- heat or humidity can reduce turgor in plants
effect of heat on vegetables
changes occur
- texture: starch gelatinizes, cellulose softens, water is lost
- flavor: flavor rich components in organic acids, s-compounds, salts, volatile oils, carbohydrates and phenolic compounds
- odor: cruciferous and allium vegetables are harsh
- color: affect pH, heat and metals
- nutrients: most are water soluble, use minimal water in preparation
effect of heat on texture
reduces bulk by water loss, increases tenderness (cellulose soften, digestibility does not change), heat vegetables until barely cooked (lignin not softened by heat: broccoli stems, end of asparagus)
effect of pH on heating vegetables
pH 4-4.5 retards softening (acidic foods), pectic substances are least soluble (resistant to softening), above or below this pH tissues will soften, adding baking soda over softens tissue and destroys nutrients
hard water
Ca or Mg; combines pectic substances to form insoluble complexes, interfere with softening, vegetables remain hard
enzymatic oxidative browning
oxygen reacts with natural iron content, acid containing ingredients will reduce browning (vinegar, lemon juice, orange juice)
phenolic compounds
tannins (unripe fruits) have bitter taste, astringent mouthfeel, degrades with ripening; found in abundance in apples, bananas, grapes, peaches, pears, and strawberries; responsible for enzymatic oxidative browning by activity of enzymes (phenols, catecholase, tyrosinase)
fruit respiration
respiration occurs as fruit grows, matures, and ripens; ethylene gas is a ripening hormone produced by fruit cells during maturation; unripe fruits may be stored in environment with ethylene gas to promote ripening
changes that occur as fruit ripens
- green color diminishes: carotenoid and flavone pigments develop
- flesh softens: changes in pectic substances
- acids develop: volatile and nonvolatile acids develop to create unique flavor
- organic acids decrease: sourness decreases, sweetness (monosaccharides) increases
purchasing fresh fruits and vegetables
USDA is responsible for voluntary producer quality grades from fresh fruits and vegetables; grades for fresh fruit are US fancy and US No. 1,2,3; based upon physical appearance (shape, color, ripeness, uniformity)
buying guide for fruits and vegetables
buy in season (flavor, nutrient content, cheaper), choose mature product (good appearance, no decay), buy for intended use, purchase by the pound, store at 36-40 degrees (tropical, subtropical: room temp) (roots, tubers: dry, constant temp)