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what is the difference between starch and cellulose?
animal cells have Endoplasmic reticulum, ribosomes, Golgi body, cell membrane, mitochondria,
plant cell has vacuole, cell sap, plastids, cell wall, plasma membrane have fiber cellulose that is indigestible by humans
both have nucleus and cytoplasm
how does the presence of fluid affect vegetable texture.
the more fluid a vegetable has the more crispness
how does the presence of vacuole affect vegetable texture.
store water and other compounds create juicer vegetables
how does the presence of intercellular spaces affect vegetable texture.
fill with air adding volume and crispness to vegetables
how does the presence of fiber affect vegetable texture.
2 indigestible fibers pectic and hemicellulose found within and between cell walls serve as inter and intracellular cement giving firmness and elasticity
what are the different pigments
yellow-orange and some red color
- acid increases red color
- alkaline changes red to blue then green
- cream/white color
- acid makes it whiter
- alkaline turns yellow or blue-black
- red-yellow color
- acid makes it purplish red to brighter red
- alkaline red turns yellow
by law ice creams are required to have a minimum of ---- % of millk
why does sherbet feel colder
sugar depresses the freezing point and causes lower fat frozen dairy desserts to have a more solid form which conveys a colder sensation to the tongue
what is the difference between sherbet, gelato, and ice cream
gelato- denser, contains more mil and less cream, churned slower at lower temperatures creating smoother and creamy texture
sherbet- made w frozen fruit juice or purees, gelatin and or eggs are added to make it creamier, has higher sugar content
ice cream- has atleast 10% milk fat the more the creamier
How may improper heating affect the products (hint: egg proteins)?
over heating can denature protein
What is the first step in ice cream preparation (basic mix that involves milk, cream, milk solids non fat, sugar) ?
it involves cooking (creates custard like base) or heating ingredients
Why are commercial ice creams smoother in texture as opposed to home-made ice creams that are grainier?
it contain commercial additives that add viscosity to the unfrozen part of the water making it firmer to chew
What is the objective of aging and churning during ice cream preparation
- aging process improves ice cream because fat begins to solidify
- churning makes small ice crystals form though out mixture rather than large clumps which makes it creamier, fat cells are broken down and reformed into larger masses which also improve texture
Candy making involves cooling a super-saturated sugar solution. How may the cooling process affect the crystal size of the candy?
- undisturbed cooling will produce large crystals
- rapid cooling with agitation will produce small crystals
- crystal formation can be reduced by adding an acid
What is the difference between crystalline and amorphous candies?
- crystalline are soft, smooth and creamy crystals are very tiny
- amorphous(noncrystalline) without form, higher sugar syrups are viscous chew caramels and hard brittles
Under what conditions will a crystalline candy be softer than expected? (lower cooking temperatures, slower cooking rate, humidity)
- lower temperature will cause candy to be soft
- if its heated too slow
- if an acidic ingredient is present it will have the same effect
- rainy weather high humidity also makes it softer
How is crystallization prevented in amorphous candies?
- cooking at high temperatures
- adding interfering substances(butter or corn syrup)
- combination of both
Role of sugar in dental caries
sugar contributes to acid production in the mouth which promotes dental caries
What causes dental caries?
disease that is initiated when acids in the mouth demineralize tooth enamel
How may food composition and combinations affect the ability to cause dental caries?
foods containing carbohydrates, all simple sugars can promote caries, dried fruits or starch/sugar combinations are more potent, starch and sugar may be more harmful than sugar alone
How should vegetables be stored (hint: respiration
- the faster respiration the more quickly it deteriorates
- cooler temp reduces resp rate
- water loss speeds resp rate
Flatulence and legumes
gases such as hydrogen, methane and carbon dioxide are produced by intestinal bacteria when they ferment the beans, indigestible carbs such as raffinose and stachyose
Nutritional advantages of legumes
excellent source of fiber, protein, iron and complex carbs
Pigments and their behavior under different pH conditions
- acids cause fruits to have ph below 5
- pigment same as vegetables
- organic acid such as citric acid give tart flavor
The role of pectin in jelly making
- used as emulsifier stabilizer thickener and texturizer
- forms a gel bet cell walls
Climacteric and non-climacteric fruits
climacteric fruits will experience increased phase of resp rate right before becoming fully ripened. fruits continue to ripen after being harvested
other fruits and vegetables are no climacteric, they continue to respire at the same or even lower rate after harvested they are best ripened fully before harvested
Enzymatic browning and its prevention
denaturing enzymes, adding acid, lowering storage temperature, blocking exposure to oxygen
Difference between amylose and amylopectin (structure and behavior)
amylose-linear molecule starch has 25% tend to gel
amylopectin- branched molecule starch has 75% non gelling some what gummy
Difference between gelatinization, gelation, retrogradation, dextrinization
- gelatinization- when starch granules are heated in a liquid ex pasta rice their texture changes
- gelation- sufficient amount of amylose must be present so it can gel ex cornstarch
- retrogradation- seepage of water out of an aging gel bonds tighten between amylose bonds (weeping)
- dextrinization- breakdown of starch molecules to smaller sweeter tasting dextrin molecules in the presence of dry heat
What are the factors that influence gelatinization?
- water- sufficient water is needed
- temp- temp varies
- timing- heating too much decreases viscosity
- stirring- required to ensure uniform consistency
- sugar, acid fat/protein
How may the addition of sugars, acids and fats impact gelatinization?
- acid- weaken ability of starch to thicken
- sugar- increases temp and delays gelatinization
- fat/protein- delays gelatinization by coating starch preventing water absorption
Difference between regular and cornstarch, cereal and tuber starches
Pre-gelatinization, Cross-linking and acid modification of starches and its use in foods.
- cross linked starch has been treated chemically to link the starch molecules together with cross bridges makes starch more heat resistant and less likely to lose viscosity
- pre gelatinization is ready to use just add cold water and it will expand
- oxidation marshmallows and chewing gum
Apply the above principles to puddings, rice cookery, pasta, and potato salad
Milk protein: difference between casein and whey and their stability (unstability) in the presence of heat, acid, rennin
- casein- flour proteins 80% protein in milk
- large atmospheric random coils
- heat- doesn't coagulate unless boiled for a long time
- acid-causes coagulation
- whey 18% of milk, liquid portion that remains after cheese production
- compact globular and helical shape cell
- heat- proteins lactalbumin and lactoglobulin become insoluble
- acid- whey doesn't coagulate
- enzyme- coagulates milk
Lactose and lactic acid bacteria (yogurt and lactose intolerance)
inability to digest lactose form of sugar found in mild
Fermentation and its advantages
the conversion of carbohydrates to carbon dioxide and alcohol by yeast or bacteria
Difference between ripened and un-ripened cheeses
- ripened chemical and physical changes that occur during the curing period
- curing period expose cheese to controlled temp and humidity during aging process
For what purpose would process cheese have greater advantage over natural cheese?
last longer, longer shelf life
What does milk powder refer to in terms of chemical composition?
non fat dried milk fortified with vitamin a and d
Concept of pasteurization and the effect of different heat treatments on milk shelf life
- destroys 100% of bacteria
- heating milk for a short time to below its boiling point ultra pasteurization 280 degree c 138 Celsius provides longer shelf life
Homogenization and its effect on sensory acceptability
results in creamier texture whiter color and blander flavor