Intro to Food Science- Fruit/Vegetable Textures, Flavors and Colors

parenchyma cells

the most common edible parts of plants that have thin cell walls and synthesize and store plant food; can be closely packed in rows or loosely packed.

collenchyma cells

elongated cells with irregularly thick cell walls made of cellulose and pectin; typically found in young stems and leaf veins

sclerenchyma cells

have the thickest cell walls and more lignin; give pears a gritty texture

lignin

part of cell walls that gives rigid structure and "woody" texture

hemicellulose

smaller branched carbohydrate than cellulose that can be composed of different monosaccharides; can be broken down by cooking in alkaline solution

turgor pressure

the pressure of cell contents on the cell wall; higher turgor pressure = more crispness, structure

plastids

a small organelle (i.e. chloroplast) that contains pigments or aromas

polyphenols

organic structures made of several phenolic rings; cangive fruits an astringent flavor when unripened

6-n propothiouracil (PROP)

a bitter-tasting compound that can indicate taste sensitivity in different people; about 25% of the population does not have the PROP receptor

allicin

a sulfur compound in garlic that gives a sharp, pungent smell/flavor/trigeminal sensation

allium

the genus that includes onions, garlic, chives, etc. that have a sharp pungent taste

cruiciferae

includes cabbage, cauliflower, brussels sprouts, turnips; have strong flavors when raw. Contain an enzyme + sinigrin that can create mustard oil

sinigrin

a glucosinate that is toxic to insects

mustard oil

synthesized from enzymatic action on sinigrin

capsaicin

spicy compound in chili peppers

trigeminal sensation

a sensation in the oral and olfactory areas that is not quite a taste or smell; pungency in garlic, onions

flavonoid

compounds that give fruits/veggies their color

anthoxanthin

yellow/white color compounds (pears, apples, potatoes, onions, flour)

chlorophyll

green pigment found in chloroplasts

carotenoids

fat soluble orange-pigmented compounds (i.e. beta carotene)

explain how the organization of cells in a plan influences whether the plant floats or sinks in water

the tighter-packed cells are, the less air there is, so a plant will sink. Loosely packed cells have air in them allowing them to float.

explain the function of pectic substances in foods

they are part of the middle lamellar layer that cements cells together. They change during ripening and cooking to give fruits/vegetables a softer texture.

explain how pectic substances change during ripening

They are broken down enzymatically into shorter chains, and methyl esters are removed and replaced by carboxyl groups by pectin esterase. These changes make a fruit/veggie more soluble and softer.

explain how pectic substances change during cooking

they break down from the heat into smaller chains, and can react with calcium or protons to become firmer.

explain how changes in the pectin substances alter the texture of fruits

breakdown of and addition of carboxyl groups will make pectic substances softer; blanching them with calcium or protons will firm up the fruit.

explain why pectin esterase activity can produce firmer canned vegetables

when cooking with added calcium/hydrogen, the pectin esterase activity firms fruits/veggies during cooking, which will maintain a firmer texture when heat-treating canned vegetables.

explain why cooking softens fruits and vegetables

no

explain how turgor pressure relates to firmness and crispness of vegetables

the higher the turgor pressure, the more firmly the cells hold their shape, giving a crispness. If there is low pressure, the cells aren't as "tight" so they get floppy.

explain why cooking in acid tends to firm fruits and vegetables

acid reacts with the pectic substances broken into shorter chains by pectin esterase, firming them.

explain why cooking in base tends to soften fruits and vegetables

explain why pectinase is added in the processing of fruit juices

it makes juices clear and a more appealing color to the customer

explain the relationship between PROP taster status and the intensity of other tastes

since PROP is a bitter-tasting compound, PROP-tasters are more likely to taste the bitterness of compounds in foods

explain the sensations that contribute to flavor

explain what's responsible for the flavor of fruits and of some vegetables

explain how the flavor of fruits change on ripening

explain how the flavor how the flavor of different classes of vegetables changes on heating

explain why some vegetables have sharp pungent flavors

explain why hydrogen sulfide is produce when some vegetables are cooked

explain how tea is made

explain why black tea is darker than green tea

explain how coffee is made

explain how to control coffee brewing to get a brew with more aroma and less bitterness

explain how people learn to like capsaicin

explain color changes in fruits and vegetables during various preparation/processing steps

explain why pigments are colored