Flashcards in CHAPTER 9: THICKENING AND GELLING AGENTS Deck (298):
The simplest way to thicken food is what?
Add an ingredient that is thickened or gelled itself.
Name some (8) ingredients that can be added to thicken food.
Heavy cream, sour cream, many cheeses, jams and jellies, fruit purees, thick syrups, yogurt, and buttermilk.
Do these ingredients only thicken?
No, they add flavor, alter appearance, and they contribute to the nutritional value of a final product.
What ingredients are added exclusively to thicken and gel?
Gelatin, vegetable gums, and starches.
How do gelatin, vegetable gums, and starches function in thickening and gelling?
Absorbing or trapping large amounts of water.
Most common thickening agent in a bakeshop that is not often thought as one.
What is an emulsion of butterfat droplets in milk?
What are other ways to thicken and gel food products besides adding an ingredient? Example.
Emulsions or foams provides thickening and sometimes gelling. Whipping heavy cream causes it to foam and thicken.
What one thing do thickening and gelling agents (gelatin, starch, vegetable gums) have in common?
They are all composed of very large molecules.
Are starches and gums polysaccharides? What are gelatins?
Yes, while gelatins are proteins.
What are polysaccharides?
Many (poly) sugar molecules (saccharides) linked to the next.
Often ________ of molecules are linked together in a single polysaccharide molecule.
Sometimes, are all sugar molecules in a polysaccharide the same?
Yes, but often there is a mix of two or more different sugars.
What distinguishes one polysaccharide from another?
The type of sugar that makes it up, how many are linked together, and how they are linked.
Do starch and inulin differ in their amount of sugars?
Yes, starch usually contains thousands of sugar units while inulin has 60 at most.
What is a more effective thickening, starch or inulin? Why?
Starch has more sugar units making it a much more effective thickener.
Very large molecules made of many amino acids linked one to the next.
Often, how many amino acids are linked together in a single protein molecule?
More than ____ common amino acids make up proteins.
What distinguishes one protein from another?
The number and arrangement of these amino acids within the protein molecule.
What occurs when water and other molecules or particles in a product move around rather slowly? Examples.
Thickening. Polysaccharides and proteins bump and entangle, water is absorbed and trapped by starch granules, or air bubbles (in foams) or fat droplets (in emulsions) slow water.
What occurs when water and other molecules in a product are prevented from moving around at all? Examples.
Gelling. When large molecules, such as protein and polysaccharides, bond with one another, forming a large we or network that traps water and other molecules. Also happens when extremely large amount of air bubbles or fat droplets are incorporated into food.
Do some thickening and gelling agents do both? Explain.
Yes, gelatin, cornstarch, and pectin thicken when used at low levels and gel when used at higher levels.
What happens if you use ingredients other than cornstarch, pectin or gelatin for gelling? Examples.
Other ingredients will only thicken, not gel. Instead, they will get thicker and gummier. Examples include guar gum, gum arabic, and waxy maize starch.
When properly prepared, gelatin form what?
An appealing crystal-clear gel with bounce back and spring. Best of all, gelatin melts quickly and cleanly in the mouth.
Is gelatin necessary in Bavarian creams, fruit mousses and cold soufflés?
Gelatin is a good stabilizer for what?
Whipped creams and many cakes fillings.
Gelatin provides the characteristic texture of what?
Marshmallows and many gummy confections.
Gelatin mixtures, when cooled to thicken, can be _________, much as egg whites can be.
What is gelatin?
An animal protein.
Most food-grade gelatin is extracted from what?
Pigskin, although small amounts are from cattle bones and hides.
Is gelatin found in any vegetable source?
Food-grade gelatin is sometimes called what?
Type A gelatin. A for the acid treatment it receives.
How do you produce Type gelatin?
Clean, chopped pigskins are soaked for several hours or days in cold acid. This breaks down pigs connective tissue, transforming its rigid, replace protein fibers (called collagen) into smaller, invisible strands of gelatin. Hot water is then used for dissolving gelatin and extracting it from the pigskins. This process is repeated up to 6 times, with each extraction occurring at a progressively higher temperature. By the last extraction, water is at a boiling point and the last bits of usable gelatin are removed.
Best-quality gelatin comes from which extraction? Why?
First, it has the strongest gel, the clearest, lightest color, and mildest flavor.
Later extractions produce what?
Weaker gelatin that is darker in color and slightly meaty in flavor.
To standardize gelatin from batch to batch, manufacturers do what?
Blend solutions from several extractions. Once blended, gelatin is filtered, concentrated, formed into sheets or "noodles," dried, and ground.
What happens to the ground gelatin?
It is either sold as is or formed into sheet gelatin.
How is sheet gelatin made?
Powdered gelatin is redissolved, reheated, then cast, cooled, and dried as a del film.
Gelatin is rated by what?
Its gel strength, also called Bloom rating.
Is Bloom rating related to gelatin quality? What does this mean?
Yes, it mean gelatin with a high Bloom rating also has a light color and clean flavor. It sets fast and produces a short, less stringy gel than gelatin with lower Bloom rating.
Early recipes calling for gelatin describe how to first boil what?
When was purified gelatin available for purchase?
Early 1800s, although a British patent for its manufacturer was issued as early as the mid-1700s.
Throughout the 1800s, gelatin was sold as what?
Shredded or in sheets.
When did powdered gelatin come about?
In America during the late 1800s, at the request of housewives.
Who responded to the American housewives' powdered gelatin inquiries?
Knox Gelatin dried gelatin sheets until brittle, then pulverized them into granules, which were easy to measure with spoons. A few years later, Jell-O gelatin was born.
What dissolves faster, shredded or powdered gelatin?
Bloom scale is a rating that was invented when?
Who created the Bloom scale? What was made to measure?
French chemist who devised a standard test and an instrument--the Bloom gelometer--for measuring gel strength.
How does the gelometer measure?
The force it takes for a small plunger to sink a certain distance into a gelatin gel prepared under standardized conditions.
Most food grade gelatins range from 50 to what?
300 on the Bloom scale.
Gelatin sold to pastry chefs is rarely, if ever, labeled with what?
Bloom rating, but manufacturers can provide that information.
Most powdered gelatin in North America is rated about _____ Bloom.
Sheet geltain is often designated by the name of what?
A precious metal.
At about 250 Bloom, platinum-labeled gelatin sheets are closest in Bloom rating to what?
Platinum sheets weigh how much?
0.06 ounces (1.7 grams)
Gold-labeled sheets are rated about _____ Bloom and weigh how much?
200 Bloom; 0.07 ounces (2 grams)
Silver-labeled are about ____ Bloom and weigh how much?
160 Bloom; 0.09 ounces (2.5 grams)
Bronze-labeled sheets are about _____ Bloom and weigh how much?
140 Bloom; 0.12 ounces (3.3 grams)
Does weight of gelatin sheets increase as Bloom rating decreases?
Yes, which makes it easy to switch from one quality of sheet gelatin to another, as long as sheets are counted, not weighed.
What is bovine spongiform encephalopathy?
Mad cow disease
What is mad cow disease?
A disease that infects the brain and spinal cord of cattle.
Has mad cow disease been found in gelatin products?
Not to date, but North America and EU follow strict quality control guidelines for gelatin manufacturing. They were even reviewed and updated since mad cow disease spread through cattle herds in Great Britain during the late 1980s.
Bloom rating is also called what?
Bloom value or Bloom strength
With a gelometer, the more force required for the plunger to drop the higher the what?
Are precautions taken to ensure all raw materials used in gelatin manufacture are from healthy animals that have been approved for human consumption?
Does the term bloom have another meaning besides gelatin strength? What is it?
Yes, it also refers to the method used for hydrating gelatin; adding it to cold liquid to swell.
Gelatin is first hydrated so it is less likely to ______ later in use.
To bloom gelatin, add powder to how much cold liquid?
5 or 10 times its weight.
How are sheets generally bloomed?
Added to excess water and gently squeezed later.
Can you use almost any liquid to bloom gelatin as long as it's cold?
Why must certain fruit juices, such as kiwi, pineapple and papaya be heated before use with gelatin?
Heat inactivates the protease enzymes in these fruits. Protease enzymes break down gelatin and other proteins, preventing them from gelling.
Liquids high in acid, such as lemon juice, may do what to gelatin?
Weaken it slightly, but they will not liquefy it. A slightly higher amount of gelatin may be needed with these ingredients.
To avoid lumps in a gelatin solution, how hot must the liquid be?
At least 140ºF (60ºC), not just warm.
How does hot liquid go to soft solid using gelatin?
Invisible strands are moving around rapidly. As the mixture cools, the strands slow and could up like telephone cords, and the coiled sections double over onto themselves. Over time, they stack up forming junctions. Water trapped in the 3D web is unable to move around. Now its a soft solid.
Gelatin generally melts completely to a liquid at what temp?
80-90ºF (27-32ºC), which is lower than body temp.
What does actually melting temperature depend on?
Bloom rating and the level of gelatin used.
How quickly do most of the gelled junctions in a gelatin web form?
Within the first one to two hours of chilling, but the process continues over the next 18 hours or so.
Are mousses and creams prepared with gelatin always firmer the second day?
Gelatin powder and sheets take how long to hydrate properly?
5 to 10 minutes.
Can gelatin be heated in a sauce pan before adding?
Yes, after it has been bloomed. But it is faster and easier to add with a hot liquid.
What happens if you allow gelatin to boil?
Extended heat damages gelatin and lowers bloom rating.
Is powdered or sheet gelatin better?
There is no right answer. Sheet gelatin is more popular is Europe than anywhere else.
Benefits of sheet gelatin.
It cannot spill, sheets can be counted (many find it easier than weighing), great for small-scale recipes.
Benefits of powder.
High volume allows to keeps prices low, in large production you don't worry about losing powder to dissolving water. Because it is produced in the US there are no import taxes to worry about.
True or false: It is produced worldwide and in much lager quantities than sheet gelatin.
What temp should water be when blooming sheets?
70ºF (21ºC) or cooler.
Is water in the tap warmer in the summer than the winter?
Yes, this also goes for different parts of the world (Arizona vs Ontario).
Is sheet gelatin a specialty item?
Yes, it's imported from Europe.
What is instant gelatin?
A new product that does not need to be bloomed or heated before use. It has undergone a special drying process. It is fine grained that dissolves instantly in cold water.
To prevent lumping, how must instant gelatin be mixed?
Mixed with other ingredients, such as sugar, before it is added to water.
How quickly does instant gelatin firm up?
In theory, can sheet and powdered gelatin be used interchangeably?
For powdered gelatin with a 230 Bloom rating, the following conversion holds.
17 gelatin sheets = 1oz (28g) gelatin powder.
Does the conversation for 230 Bloom powdered gelatin means that 17 sheets weigh 1 ounce?
No, although that is essentially true for platinum sheets. It just means that 17 sheets of any grade provide about the same gelling strength as 1 ounce of powdered gelatin.
How much water does gelatin absorb? Is this water always listed in formulas?
5 times its weight. It's only listed in powdered gelatin formulas.
What are vegetable gums?
Polysaccharides that absorb large quantities of water, swelling to produce thick liquids and gels.
Do some gums have a gummy texture?
Yes, but most don't when used properly.
Are all vegetable gums vegetable in origin?
Yes, they are extracted and purified from trees, bushes, shrubs, seeds, seaweed, or microorganisms. Many are natural.
Is cellulose gum natural?
It's from a natural source but chemically modified to improve its properties.
Are all vegetable gums a good source of soluble dietary fiber?
Dietary fiber consist of what?
Polysaccharides that are not digested by the human body.
Is pectin present in all fruits?
Yes, but the amount varies.
Fruits high in pectins include what?
apples, plums, cranberries, raspberries, and citrus peel.
Can fruits high in pectin be made into jams and jellies without any added pectin?
Pectin thickens, but what does it do in the presence of acid and high amounts of sugar?
Are pectin gels clear or cloudy?
Clear with an attractive sheen and clean flavor.
Pectin is commonly used in what?
Mirrors, glazes, jams and jellies, bakery fillings, and fruit confections.
Pectin can be purchased as what?
Powdered pectin is generally extracted and purified from what?
Citrus peel or apple skins.
What is agar called in Japan?
Agar is derived from what?
Any of several species of red seaweed (gracilaria or gelidium, for example).
Agar is also called what?
How long have Asian cultures used agar?
Where is agar harvested today? How is it sold?
Worldwide and commonly sold in the US as dry powder or as strands.
What do strands and powdered agar require before use? How quickly do they gel?
Strands require soaking and several minutes of boiling in water to dissolve, agar powder dissolves in water water in about a minute. Both gel quickly as they cool, much faster than gelatin.
Is agar a polysaccharide or a protein?
Polysaccharide, but it is sometimes nicknamed a vegetable gelatin because gels made from agar are similar to those made from gelatin.
Are agar and gelatin gels identical? Why?
While they are similar they are not identical. For one, much less agar is needed than gelatin, and agar gels stay firm without refrigeration. This makes agar useful for firming piping gels and in certain jellied confections. Agar is also a good warm weather stabilizer for icings and fillings, and it can be used to replace pork-based gelatin whenever dietary or religious restrictions warrant its use.
Does agar have the same mouthfeel as gelatin?
No, because it does not melt as readily as gelatin.
Can agar be whipped as gelatin can? What does this mean for substitutions?
No, this means it cannot be substituted for gelatin is aerated products.
The often cited conversion from gelatin to agar is what?
8:1 meaning that agar is 8 times stronger than gelatin. However, they are both natural products, and like the rest they vary in strength between manufacturers.
What's the only way to be certain with how much agar is needed?
Testing several products with different levels of agar.
What red seaweed was once a popular gelling agent in Europe?
Carrageenan, which was found off the coast of Ireland near a town called Carragheen. Cooks made a flan type pudding by boiling the seaweed with milk, then cooling.
What is carrageenan?
Like agar, is extracted from a red seaweed (Chondrus).
Where is carrageenan used?
Pastry chefs are generally less familiar with it than agar, but it's used in many commercial food products for thickening and gelling.
Where is carrageenan particularly effective?
Milk products, which is why it's added to eggnog, chocolate milk, ice-cream, and instant flan mixes.
Another form of carrageenan is what?
Where is Irish moss popular? For what?
In the Caribbean for thickening beverages and as an aphrodisiac.
What is guar gum and locust bean gum?
They're from the endosperm of beans growing in pods that look much like string beans or pea pods.
Guar gum is from where?
The beans of a plant (Cyamopsis tetragonoloba) that grows in India and Pakistan.
Locust bean gum is also called what?
Where is locust bean gum from?
Beans of an evergreen tree (Ceratonia siliqua) that is originally from the Mediterranean.
While locust bean gum is from the ______, another food ingredient, carob flour, is from the ______.
How is carob bean flour made?
Pods are roasted, then ground, and used as a cocoa powder substitute.
Both guar gum and locust bean gum are used as what?
Thickeners in a broad range of products, including cream cheese and sour cream. Also commonly used in frozen foods, such as ice cream and frozen pasteurized egg whites, to prevent ice crystal growth and freezer damage.
What is gum arabic?
Purified and dried from the exudate--gummy sap--of a tree (Acacia) that grows in northern Africa. The sap forms when a tree trunk or branch has been damaged, either through extreme climatic conditions or deliberate knife cuts.
Gum arabic is good at what?
Stabilizing emulsions while maintaining a pleasing, non gummy mouthfeel. That is why it continues to be used in icings, fillings, and certain flavoring, even when its supply in scarce.
What is gum tragacanth?
Obtained in a way similar to gum arabic, but it is from a shrub (Astragalus) that grows in the Middle East. Much thicker than gum arabic, gum tragacanth is probably best known to pastry chefs as an ingredient in gum paste, used by cake decorators for making flowers and other designs.
Is gum tragacanth expensive?
Extremely because its main supply is in a politically unstable part of the world. For this reason, its is being replaced by other gums in most foods.
What is xanthan gum?
A fairly new gum, in use since the 1960s. It is produced when a certain microorganism (Xanthomonas campestris) undergoes fermentation.
Why is xanthan gum used in salad dressings?
It thickens without feeling heavy or thick.
Xanthan gum is often used along with starch, often rice starch, to replace what?
Wheat flour in gluten free baked goods.
Xanthan gum, used at about ___ to ___%, helps batters and doughs hold in gases, leaven, and provide an acceptable crumb to these baked goods.
What is methylcellulose?
One of several gums derived from cellulose. It is made commercially by chemically modifying wood or cotton cellulose fibers. It is not considered a natural gum because of these modifications.
What makes up cell walls of all plants?
Cellulose, the most plentiful polysaccharide on earth.
Methylcellulose is also called what?
Modified vegetable gum.
What unique property does modified vegetable gum have that makes it useful in bakery fillings?
While most gels thin out at oven temperatures and thicken as they cool, modified vegetable gum gels at oven temperatures and thins out as it cools. Instead of bleeding and running as it is baked in Danish pastries, a bakery filling made with modified vegetable gum holds its shape.
Like gums, starch molecules are ___________.
What is starch?
Polysaccharides, or large, complex carbohydrate molecules made of many sugar units bonded one to the next. In the case of starch, the sugar units are glucose molecules.
Are all starch molecules alike?
How many ways can glucose units be arranged in starch?
What are the two ways glucose units can be arranged? What are they called?
As long straight chains (amylose) or as short but highly branched ones (amylopectin).
Although amylose is a straight chain, that chain typically twists into a _________ shape, while amylopectin, with its many branched looks like a _______ _______.
helical (spring or DNA); coral fan.
Are starch molecules tightly packed in an orderly fashion?
How can you tell if a starch is high in amylose?
Cloudy when cooled
Forms a firm heavy-bodied gel when cooled
Gel tightens and weeps over time
Not freezer-stable; tends to tighten and weep
Much thicker cold than hot
Tends to mask flavors
How can you tell if a starch is high in amylopectin?
Relatively high clarity
Thickens, does not gel
Much less likely to weep over time
Much less likely to weep when thawed
Essentially the same thickness hot or cold
Less likely to mask flavors
Small, gritty particles that are found in the endosperm of cereal grains.
Are starch granules found in the tubers and roots of certain plants? Examples.
Yes, including potatoes, arrowroot and yuca.
Yuca is also called what?
Cassava or manioc.
What is a tuber?
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months, to provide energy and nutrients for regrowth during the next growing season, and as a means of asexual reproduction.
Do starch granules vary in size and shape?
Yes, depending on the starch.
What starch granules are very large and oval in shape?
Are cornstarch granules the same size and shape as potato starch?
No, much smaller and more angular.
How are starch granules like trees?
They grow larger over time and form rings of starch molecules, much like tree rings.
Do different types of starched have properties uniquely their own? Why?
Yes, some differences occur because of the distinctive size and shape of each starch's granule. Other differences occur because of the amount of amylopectin and amylose in each.
Is cornstarch high in amylopectin or amylose?
Is waxy maize high in amylopectin or amylose?
Root starches, which could be considered _______-______, have properties somewhere between the two.
All starched begin as what?
Cereal or root starches. Instant starches and modified starches are manufactured from these.
Cereal starches are extracted from what?
Endosperm of cereal grains.
Name some cereal starches.
Cornstarch, rice starch, wheat starch, and waxy maize.
Most common starch used in the bakeshop.
Advantage of cornstarch in America.
Inexpensive and readily available. Should be your first choice unless it somehow doesn't meet your needs.
Is waxy maize a type of cornstarch? Explain.
Yes, one that is extracted from a very different corn kernel and has different properties than regular cornstarch.
While most cereal starches are high in _______, waxy maize is high in ______.
Waxy maize starch is sometimes called what?
Root starched are extracted from where?
Various root or tuber plants.
How do root starched differ from cereal starches?
Mostly because they are lower in amylose and higher in amylopectin. They are generally more expensive than cornstarch, don't have a cereal taste, have much better clarity, and produce a softer gel.
Examples of root starches.
Potato starch, arrowroot (Maranta arundinacea), and tapioca.
How are all root starches sold?
As fine powders, also called flours.
Tapioca is extracted from what?
Yuca root, also called manioc or cassava.
Yuca would not be confused with what?
Yuca is a versatile root used where?
South America and the Caribbean in the same way potatoes are commonly used.
The most common starch, besides cornstarch, in America.
Yuca, or tapioca flour.
Why is tapioca flour more expensive than cornstarch?
It is imported, primarily from Thailand or Brazil, to America.
Besides being sold as finely-ground flour, tapioca is available as what?
Quick-cooking granules or as various-sized pearls.
Tapioca granules and pearls are made from tapioca starch that has been what?
Agglomerated, or clumped, and gently heated. The heating gelatinizes the other layer of starch.
Granules and pearls tend to cook into a _____, less ____ texture than unmodified tapioca flour.
Do quick-cooking granules, such as Minute brand tapioca, dissolve quickly? What about pearls?
Yes, while pearls must be soaked for several hours before using.
Do tapioca pearls become translucent when cooked?
Yes, but they retain their size and shape in the finished product.
What are modified food starches?
Starches that have been treated by the manufacturer with one or more chemicals approved for use by government agencies.
Modified food starches are "designer starches." What does that mean?
They are designed by the manufacturer to have certain desirable features.
While any native starch can be modified, most modified food starches are made from what?
Waxy maize starch.
Difference between waxy maize and regular cornstarch.
Waxy maize is relatively clear and clean tasting. It is modified in one or more ways to increase its stability against excessive heat, acid, and freezing.
Main reason to use a modified starch in a bakeshop.
Its added stability.
What other ways can starched be modified?
To slow or increase gelatinization or change their texture.
Why is Cloflo 67 called a cook-up starch?
Because it must be cooked like any regular starch.
Instant starches thicken and gel without what?
Are instant starches different from modified starches?
Yes, although most instant starches are modified.
Instant starches are sometimes called what?
Pre-gelatinized or cold-water swelling.
How do manufacturers make a starch instant?
They either precook (pre-gelatinize) and then dry the starch, or make some other change to the starch so that the granules absorb water without heat.
While instant starches do not require heat, will heat damage the product?
No, they are safe to heat.
Why should you be careful when whisking instant starch into cold liquids?
The starch thickens so quickly that it's easy to whisk and trap air bubbles. If necessary, the mixture can be gently heated after whisking to allow air bubbles to dissipate.
How do you prevent an instant starch from clumping when adding it to liquids?
First, blend it with sugar or another dry ingredient. The rule is to blend four parts sugar with one part instant starch. However, some instant starches are designed to easily mix with liquid, so not every instant starch require a high amount of sugar.
Give an example of instant starch being good for kiwi coulis.
Because instant starches do not require heat, they are ideal for heat sensitive products like kiwi, keeping the bright color and delicate flavor.
How much more do specialty starches cost than regular?
Usually 2 to 3 times more.
Do instant starches have the same texture as regular starches? Can they replace cornstarch?
Not necessarily, which is why they can't totally replace cornstarch in the bakeshop.
Are starch molecules packed in tight order inside of starch granules?
When starch granules are placed in cold water, the molecules inside attract water and the granules swell slightly. If the water is heated, the granules undergo an irreversible process called what?
Which granules typically gelatinize faster, bigger or smaller?
Bigger ones typically gelatinize first, with smaller granules taking longer time to fully absorb water and swell.
As heating continues, the granules continue to swell and starch molecules, especially ______ molecules, leach into the hot liquid. At this point, the starch mixture is properly ______ cooked.
What happens if the starch granules are heated past the point of "properly cooked?"
If there's enough water present, the granules continue to release their contents, becoming smaller and more deformed in shape, until finally they rupture completely. At this point, all that's left are small granule fragments and freed starch molecules.
Does mixing and stirring speed up the rupturing of starch granules?
As the starch solution cools, starch molecules slow down and _______, tripping additional water and thickening.
If there is a high enough concentration of entangled _______ molecules, the solution gels as it cools.
Is there an optimum amount of heat for maximizing thickening?
What happens if you heat too much or too little?
Too few granules swell, let alone release starch molecules. Too much heat and too many granules degrade.
Why is under gelatinization a problem?
Raw granules are hard and dense, undercooked starch feels gritty in the mouth. Undercooked starch is more opaque and typically has a raw starch taste.
If stored for a day or more, undercooked starch mixtures tend to what?
Weep, meaning unattractive droplets or even pools of water form around the gel.
Because undercooked starch has a different characteristic than overcooked, is it easy to tell if a too-thin starch mixture has been over or undercooked?
Does each type of starch have an optimum amount of heat for proper gelatinization?
The amount of time to fully gelatinize root starches varies with the formula, but it is always less than the amount of time to fully gelatinize ________.
Most times, unmodified root starches should not be brought to a _______.
When cooked for too long, unmodified root starches become excessively _______ in _______. If this happens, the sauce or filling should be remade.
If a formula for a starch-thickened sauce or pie filling is high in sugar, what should you do? Why?
Withhold half the sugar until after the starch has gelatinized. This way the starch has a chance to absorb water before the hygroscopic sugar grabs the water and prevents the starch from gelatinizing.
The tendency of starch to be overcooked when acid is present can be somewhat compensated for by what?
Reduced cooking time, increasing the amount of starch, or by adding acid after the starch mixture has fully gelatinized and cooled.
What is by far the best solution to dealing with starch and acid?
Switching to a starch that is acid resistant.
The most acid-resistant starches are what?
Modified food starches, but root starches and waxy rice starch are somewhat more resistant than...?
Do sweeteners and fats slow the rate at which starch granules absorb water?
The more slowly they absorb water, the longer it takes starch granules to ________.
If enough sugar is present, what happens to gelatinization? How is this helpful in baked goods?
It completely prevents starch from gelatinizing. This is one of the ways that sugars and fats tenderize baked goods: they reduce the amount of structure building starch gelatinization that occurs.
Does sugar increases translucent of starch0thickened mixtures?
How does acid affect starch molecules?
Acid hydrolyzes large starch molecules into smaller ones, reducing their thickening power. Acid also disrupts starch granules so that they gelatinize more quickly and easily.
If enough acid is present, gelatinization occurs so quickly that what?
The starch mixture appears not to thicken at all.
Describe undercooked starch mixture.
Raw starch taste
Tends to weep
Describe overcooked starch mixture.
Too thin; may be stringy
No raw starch taste
Does not weep
Name 5 native starches.
Cornstarch, potato, rice, arrowroot, tapioca
Questions to consider when selecting a thickening and gelling agent: Is clarity important?
If yes, use a root starch or a modified food starch; better yet, don't use a starch. Use gelatin or a vegetable gum such as agar or pectin.
Questions to consider when selecting a thickening and gelling agent: Are you thickening or gelling a heat-sensitive product, such as kiwi or strawberry?
If yes, use an instant starch or use gelatin.
Questions to consider when selecting a thickening and gelling agent: Is a sharp, clean flavor important, such as in a fruit pie filling or glaze?
If yes, use a root starch; better yet, use gelatin or pectin.
Questions to consider when selecting a thickening and gelling agent: Are you planning to freeze the product?
If yes, use a root starch; better yet, use a modified food starch.
Questions to consider when selecting a thickening and gelling agent: What is the desired consistency? For example, would you prefer a soft gel to a firm, heavy-bodied one?
If yes, use a root starch, or use cornstarch and stir the mixture as it cools.
Questions to consider when selecting a thickening and gelling agent: Are there price constraints?
If yes, your best choice is cornstarch, but all starches are relatively inexpensive when compared to most other thickening and gelling agents.
Properties of cornstarch.
Cloudy when cooled; good sheen.
Heavy body; gels if concentration is high.
Not stable to excessive heat, acid, freezing, mixing.
Gel tightens and weeps over time.
Masks many flavors.
High gelatinization temperature.
Ideal uses of cornstarch.
Puddings, cream pies.
Properties of arrowroot.
Moderate to high clarity; high sheen.
Soft gel; can be stringy.
Relatively stable against acid, heat, mixing, freezing.
Relatively low gelatinization temperature.
Relatively clean flavor.
Ideal uses for arrowroot.
Fruit pies and sauces.
Properties of tapioca.
Moderate to high clarity; high sheen.
Soft gel; can be stringy.
Relatively stable against acid, heat, mixing, freezing.
Relatively low gelatinization temperature.
Relatively clean flavor.
Available as pearls, granules, powder.
Ideal uses of tapioca.
Fruit pies, sauces, tapioca pudding.
Properties of waxy maize.
Moderate to high clarity.
Thickens, does not gel.
Relatively stable against acid, heat, mixing, freezing.
Relatively clean flavor.
Ideal uses of waxy maize.
Base for many modified starches; not typically available unmodified.
Properties of modified food starch.
High stable against acid, heat, mixing, freezing.
Variable gelatinization temperature.
Other properties vary with brand.
Ideal uses for modified starches.
Steam table applications
High acid products
Properties of instant starch.
No heat required
Properties vary with brand
Ideal uses for instant starch.
Properties of flour.
Cloudy; yellow-tinged color.
Imparts a flavor; masks or mellows flavors.
Ideal uses for flour.
Home-style pie uses
Properties of gelatin.
High clarity, high sheen
Forms firm, bouncy gel
At typical usage levels, melts in mouth and at room temp
Available as sheets, powder
Ideal uses of gelatin.
Stabilized whipped cream
Confections (gummy bears)
Properties of agar.
Moderate to high clarity
Forms very firm, bouncy gel
Stable (does not melt) at room temp or in mouth
Usage levels vary with purity
Available as sheets, strands and powder
Ideal uses of agar.
As gelatin substitute for:
a. vegetarians and people with religious dietary restrictions.
b. use with raw pineapple, etc.
Properties of pectin.
High clarity, high sheen
Thickens or gels
Generally requires high acid and high sugar concentrations.
Ideal uses of pectin.
Fruit jams, jellies, fillings
High-quality jelly confections.
To say that an ingredients provides a thickened or gelled texture to sauces, fillings, glazes, and creams is to say that it provides what?
Thickening and gelling is the formation of a very soft _____.
Are thickening and gelling agents sometimes called stabilizers?
Yes, they provide undesirable changes in food.
What is starch retrogradation in simple terms?
The formation of too much structure.
What is starch retrogradation?
A process in which starch molecules in a cooked or baked and cooled product bond more and more closely over time, increasing structure.
What happens to starch-based food when starch retrogradation happens?
Starch based creams and pie fillings shrink and firm up, becoming tough and rubbery. And the shrinking network of starch molecules squeeze out water, causing weeping.
Weeping is also known as what?
It is starch retrogradation that makes high-amylose starches, such as cornstarch, inappropriate for creams and fillings that are to be ______ or _______ for any length of tie.
What happens when starches retrograde in baked goods?
The soft crumb becomes dry, hard, and crumbly. In other words, its the primary cause of staling in baked goods. Water may be squeezed out of the starch, but it is not evident in baked goods because other ingredients are likely to absorb the water.
How can starch retrogradation be prevented in baked goods?
By covering products to prevent moisture loss; by storing products at room temp or in the freezer--not in the refrigerator, where retrogradation is fastest; and by adding ingredients that slow down the process.
What ingredients delay starch retrogradation?
Sugars, proteins, fats and emulsifiers.
Why are pastries slower to stale than breads and rolls?
They contain more starch retrogradation delaying ingredients.
How does gelatin stabilize whipped cream?
Primarily by gelling. This solidifies the walls surrounding air bubbles in whipped cream and prevents them from breaking.
What stabilizes frozen eggs whites primarily by thickening them?
How do the thickening properties of guar gum stabilize frozen egg whites?
It prevents the formation of large, damaging ice crystals and allows the eggs whites to whip fully.
How do many thickening and gelling agents provide a gloss or sheen?
Many form a smooth layer that clings to the surfaces of ingredients. This smooth layer reflects light in a way that provides gloss or sheen to many sauces, fillings, and glazes.
Starch added to baked goods interferes with what? When is this especially true?
The formation of gluten and egg structure. This is especially true when there is not enough water for starch to gelatinize, as is the case for cookies and pie doughs.
It is only through what the starch forms structure? Otherwise it consists of what?
Gelatinization, or it consists of hard, gritty particles that interfere with protein webs that gluten or eggs form.
Why are all starches and gums driers?
Because they absorb moisture and, often, fats and oils.
Why is cornstarch added to dry powdered mixtures?
To absorb moisture. This prevents caking and keeps dry powder free-flowing.
Is cornstarch added to confectioners' and icing sugar?
Why is cornstarch commonly added to baking powder?
Besides keeping it free-flowing, cornstarch serves as a bulking agent to standardize baking powders. It also prevents losses in activity. As it absorbs moisture, it prevents the reaction of acid and baking soda and the release of carbon dioxide.
How should thickening and gelling agents be stored? Why?
Covered so it prevents moisture absorption.
Before heating starches, and many other thickening and gelling agents, why should dry particles be separated?
If granules are not separated before heating, they will clump. If this happens, they must be sieved out, which reduces thickening ability.
Three main ways of separating dry granules.
Blend granules with other dry ingredients, such as sugar.
Add granules first to cold water, making a paste or slurry.
Blend granules with fat, such as butter or oil.
Rule of thumb for blending granules with other dry ingredients.
Add at least four or five parts sugar to one part dry starch (or gelatin, or gum).
Making a slurry can be used with most starches except what? Why?
Many instant starches, and many other ingredients like guar gum that absorb cold water quickly, clump when added to cold water. These ingredients must be blended with dry ingredients first, or blended with fat.
Why must creams containing egg yolks in addition to starch not be undercooked?
Besides the possibility of bacteria growth, egg yolks contain amylase, which breaks down starch molecules and destroys thickening and gelling power.
What destroys amylase and other enzymes?
Why shouldn't chefs double-dip into starch based products.
The amylase in saliva is particularly strong, and it can thin out starch based products in minutes.
Do cornstarch mixtures start to thicken before coming to a boil?
Yes, but you should continue cooking to ensure all starch granules are fully hydrated.
Good rule of thumb for cooking time of cornstarch.
Bring to a boil and boil gently for 2 or 3 minutes.
Should root starches be brought to a boil?
No, heating them like cornstarch mixtures is too much.
Should starch mixtures be constantly stirred?
Yes, to prevent scorching or burning.