CHAPTER 9: THICKENING AND GELLING AGENTS Flashcards
1
Q
The simplest way to thicken food is what?
A
Add an ingredient that is thickened or gelled itself.
2
Q
Name some (8) ingredients that can be added to thicken food.
A
Heavy cream, sour cream, many cheeses, jams and jellies, fruit purees, thick syrups, yogurt, and buttermilk.
3
Q
Do these ingredients only thicken?
A
No, they add flavor, alter appearance, and they contribute to the nutritional value of a final product.
4
Q
What ingredients are added exclusively to thicken and gel?
A
Gelatin, vegetable gums, and starches.
5
Q
How do gelatin, vegetable gums, and starches function in thickening and gelling?
A
Absorbing or trapping large amounts of water.
6
Q
Most common thickening agent in a bakeshop that is not often thought as one.
A
Egg
7
Q
What is an emulsion of butterfat droplets in milk?
A
Heavy cream.
8
Q
What are other ways to thicken and gel food products besides adding an ingredient? Example.
A
Emulsions or foams provides thickening and sometimes gelling. Whipping heavy cream causes it to foam and thicken.
9
Q
What one thing do thickening and gelling agents (gelatin, starch, vegetable gums) have in common?
A
They are all composed of very large molecules.
10
Q
Are starches and gums polysaccharides? What are gelatins?
A
Yes, while gelatins are proteins.
11
Q
What are polysaccharides?
A
Many (poly) sugar molecules (saccharides) linked to the next.
12
Q
Often ________ of molecules are linked together in a single polysaccharide molecule.
A
thousands
13
Q
Sometimes, are all sugar molecules in a polysaccharide the same?
A
Yes, but often there is a mix of two or more different sugars.
14
Q
What distinguishes one polysaccharide from another?
A
The type of sugar that makes it up, how many are linked together, and how they are linked.
15
Q
Do starch and inulin differ in their amount of sugars?
A
Yes, starch usually contains thousands of sugar units while inulin has 60 at most.
16
Q
What is a more effective thickening, starch or inulin? Why?
A
Starch has more sugar units making it a much more effective thickener.
17
Q
Very large molecules made of many amino acids linked one to the next.
A
Proteins
18
Q
Often, how many amino acids are linked together in a single protein molecule?
A
Thousands
19
Q
More than ____ common amino acids make up proteins.
A
20
20
Q
What distinguishes one protein from another?
A
The number and arrangement of these amino acids within the protein molecule.
21
Q
What occurs when water and other molecules or particles in a product move around rather slowly? Examples.
A
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.
22
Q
What occurs when water and other molecules in a product are prevented from moving around at all? Examples.
A
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.
23
Q
Do some thickening and gelling agents do both? Explain.
A
Yes, gelatin, cornstarch, and pectin thicken when used at low levels and gel when used at higher levels.
24
Q
What happens if you use ingredients other than cornstarch, pectin or gelatin for gelling? Examples.
A
Other ingredients will only thicken, not gel. Instead, they will get thicker and gummier. Examples include guar gum, gum arabic, and waxy maize starch.
25
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.
26
Is gelatin necessary in Bavarian creams, fruit mousses and cold soufflés?
Yes
27
Gelatin is a good stabilizer for what?
Whipped creams and many cakes fillings.
28
Gelatin provides the characteristic texture of what?
Marshmallows and many gummy confections.
29
Gelatin mixtures, when cooled to thicken, can be _________, much as egg whites can be.
whipped
30
What is gelatin?
An animal protein.
31
Most food-grade gelatin is extracted from what?
Pigskin, although small amounts are from cattle bones and hides.
32
Is gelatin found in any vegetable source?
No
33
Food-grade gelatin is sometimes called what?
Type A gelatin. A for the acid treatment it receives.
34
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.
35
Best-quality gelatin comes from which extraction? Why?
First, it has the strongest gel, the clearest, lightest color, and mildest flavor.
36
Later extractions produce what?
Weaker gelatin that is darker in color and slightly meaty in flavor.
37
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.
38
What happens to the ground gelatin?
It is either sold as is or formed into sheet gelatin.
39
How is sheet gelatin made?
Powdered gelatin is redissolved, reheated, then cast, cooled, and dried as a del film.
40
Gelatin is rated by what?
Its gel strength, also called Bloom rating.
41
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.
42
Early recipes calling for gelatin describe how to first boil what?
Calve's hoofs.
43
When was purified gelatin available for purchase?
Early 1800s, although a British patent for its manufacturer was issued as early as the mid-1700s.
44
Throughout the 1800s, gelatin was sold as what?
Shredded or in sheets.
45
When did powdered gelatin come about?
In America during the late 1800s, at the request of housewives.
46
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.
47
What dissolves faster, shredded or powdered gelatin?
Powdered
48
Bloom scale is a rating that was invented when?
1800s
49
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.
50
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.
51
Most food grade gelatins range from 50 to what?
300 on the Bloom scale.
52
Gelatin sold to pastry chefs is rarely, if ever, labeled with what?
Bloom rating, but manufacturers can provide that information.
53
Most powdered gelatin in North America is rated about _____ Bloom.
230
54
Sheet geltain is often designated by the name of what?
A precious metal.
55
At about 250 Bloom, platinum-labeled gelatin sheets are closest in Bloom rating to what?
Powdered geltain.
56
Platinum sheets weigh how much?
0.06 ounces (1.7 grams)
57
Gold-labeled sheets are rated about _____ Bloom and weigh how much?
200 Bloom; 0.07 ounces (2 grams)
58
Silver-labeled are about ____ Bloom and weigh how much?
160 Bloom; 0.09 ounces (2.5 grams)
59
Bronze-labeled sheets are about _____ Bloom and weigh how much?
140 Bloom; 0.12 ounces (3.3 grams)
60
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.
61
What is bovine spongiform encephalopathy?
Mad cow disease
62
What is mad cow disease?
A disease that infects the brain and spinal cord of cattle.
63
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.
64
Bloom rating is also called what?
Bloom value or Bloom strength
65
With a gelometer, the more force required for the plunger to drop the higher the what?
Bloom rating.
66
Are precautions taken to ensure all raw materials used in gelatin manufacture are from healthy animals that have been approved for human consumption?
Yes
67
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.
68
Gelatin is first hydrated so it is less likely to ______ later in use.
clump
69
To bloom gelatin, add powder to how much cold liquid?
5 or 10 times its weight.
70
How are sheets generally bloomed?
Added to excess water and gently squeezed later.
71
Can you use almost any liquid to bloom gelatin as long as it's cold?
Yes
72
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.
73
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.
74
To avoid lumps in a gelatin solution, how hot must the liquid be?
At least 140ºF (60ºC), not just warm.
75
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.
76
Gelatin generally melts completely to a liquid at what temp?
80-90ºF (27-32ºC), which is lower than body temp.
77
What does actually melting temperature depend on?
Bloom rating and the level of gelatin used.
78
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.
79
Are mousses and creams prepared with gelatin always firmer the second day?
Yes
80
Gelatin powder and sheets take how long to hydrate properly?
5 to 10 minutes.
81
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.
82
What happens if you allow gelatin to boil?
Extended heat damages gelatin and lowers bloom rating.
83
Is powdered or sheet gelatin better?
There is no right answer. Sheet gelatin is more popular is Europe than anywhere else.
84
Benefits of sheet gelatin.
It cannot spill, sheets can be counted (many find it easier than weighing), great for small-scale recipes.
85
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.
86
True or false: It is produced worldwide and in much lager quantities than sheet gelatin.
True
87
What temp should water be when blooming sheets?
70ºF (21ºC) or cooler.
88
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).
89
Is sheet gelatin a specialty item?
Yes, it's imported from Europe.
90
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.
91
To prevent lumping, how must instant gelatin be mixed?
Mixed with other ingredients, such as sugar, before it is added to water.
92
How quickly does instant gelatin firm up?
30 minutes.
93
In theory, can sheet and powdered gelatin be used interchangeably?
Yes
94
For powdered gelatin with a 230 Bloom rating, the following conversion holds.
17 gelatin sheets = 1oz (28g) gelatin powder.
95
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.
96
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.
97
What are vegetable gums?
Polysaccharides that absorb large quantities of water, swelling to produce thick liquids and gels.
98
Do some gums have a gummy texture?
Yes, but most don't when used properly.
99
Are all vegetable gums vegetable in origin?
Yes, they are extracted and purified from trees, bushes, shrubs, seeds, seaweed, or microorganisms. Many are natural.
100
Is cellulose gum natural?
It's from a natural source but chemically modified to improve its properties.
101
Are all vegetable gums a good source of soluble dietary fiber?
Yes
102
Dietary fiber consist of what?
Polysaccharides that are not digested by the human body.
103
Is pectin present in all fruits?
Yes, but the amount varies.
104
Fruits high in pectins include what?
apples, plums, cranberries, raspberries, and citrus peel.
105
Can fruits high in pectin be made into jams and jellies without any added pectin?
Yes
106
Pectin thickens, but what does it do in the presence of acid and high amounts of sugar?
It gels.
107
Are pectin gels clear or cloudy?
Clear with an attractive sheen and clean flavor.
108
Pectin is commonly used in what?
Mirrors, glazes, jams and jellies, bakery fillings, and fruit confections.
109
Pectin can be purchased as what?
Dry powder.
110
Powdered pectin is generally extracted and purified from what?
Citrus peel or apple skins.
111
What is agar called in Japan?
Kanten
112
Agar is derived from what?
Any of several species of red seaweed (gracilaria or gelidium, for example).
113
Agar is also called what?
Agar-agar
114
How long have Asian cultures used agar?
For centuries.
115
Where is agar harvested today? How is it sold?
Worldwide and commonly sold in the US as dry powder or as strands.
116
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.
117
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.
118
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.
119
Does agar have the same mouthfeel as gelatin?
No, because it does not melt as readily as gelatin.
120
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.
121
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.
122
What's the only way to be certain with how much agar is needed?
Testing several products with different levels of agar.
123
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.
124
What is carrageenan?
Like agar, is extracted from a red seaweed (Chondrus).
125
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.
126
Where is carrageenan particularly effective?
Milk products, which is why it's added to eggnog, chocolate milk, ice-cream, and instant flan mixes.
127
Another form of carrageenan is what?
Irish moss.
128
Where is Irish moss popular? For what?
In the Caribbean for thickening beverages and as an aphrodisiac.
129
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.
130
Guar gum is from where?
The beans of a plant (Cyamopsis tetragonoloba) that grows in India and Pakistan.
131
Locust bean gum is also called what?
Carob gum
132
Where is locust bean gum from?
Beans of an evergreen tree (Ceratonia siliqua) that is originally from the Mediterranean.
133
While locust bean gum is from the ______, another food ingredient, carob flour, is from the ______.
bean; pod
134
How is carob bean flour made?
Pods are roasted, then ground, and used as a cocoa powder substitute.
135
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.
136
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.
137
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.
138
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.
139
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.
140
What is xanthan gum?
A fairly new gum, in use since the 1960s. It is produced when a certain microorganism (Xanthomonas campestris) undergoes fermentation.
141
Why is xanthan gum used in salad dressings?
It thickens without feeling heavy or thick.
142
Xanthan gum is often used along with starch, often rice starch, to replace what?
Wheat flour in gluten free baked goods.
143
Xanthan gum, used at about ___ to ___%, helps batters and doughs hold in gases, leaven, and provide an acceptable crumb to these baked goods.
2-3%
144
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.
145
What makes up cell walls of all plants?
Cellulose, the most plentiful polysaccharide on earth.
146
Methylcellulose is also called what?
Modified vegetable gum.
147
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.
148
Like gums, starch molecules are ___________.
polysaccharides.
149
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.
150
Are all starch molecules alike?
No
151
How many ways can glucose units be arranged in starch?
2
152
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).
153
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.
154
Are starch molecules tightly packed in an orderly fashion?
Yes
155
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
156
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
```
157
Small, gritty particles that are found in the endosperm of cereal grains.
Starch granules.
158
Are starch granules found in the tubers and roots of certain plants? Examples.
Yes, including potatoes, arrowroot and yuca.
159
Yuca is also called what?
Cassava or manioc.
160
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.
161
Do starch granules vary in size and shape?
Yes, depending on the starch.
162
What starch granules are very large and oval in shape?
Potato starch
163
Are cornstarch granules the same size and shape as potato starch?
No, much smaller and more angular.
164
How are starch granules like trees?
They grow larger over time and form rings of starch molecules, much like tree rings.
165
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.
166
Is cornstarch high in amylopectin or amylose?
Amylose
167
Is waxy maize high in amylopectin or amylose?
Amylopectin
168
Root starches, which could be considered _______-______, have properties somewhere between the two.
medium-amylose
169
All starched begin as what?
Cereal or root starches. Instant starches and modified starches are manufactured from these.
170
Cereal starches are extracted from what?
Endosperm of cereal grains.
171
Name some cereal starches.
Cornstarch, rice starch, wheat starch, and waxy maize.
172
Most common starch used in the bakeshop.
Cornstarch.
173
Advantage of cornstarch in America.
Inexpensive and readily available. Should be your first choice unless it somehow doesn't meet your needs.
174
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.
175
While most cereal starches are high in _______, waxy maize is high in ______.
Amylose, amylopectin
176
Waxy maize starch is sometimes called what?
Waxy cornstarch
177
Root starched are extracted from where?
Various root or tuber plants.
178
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.
179
Examples of root starches.
Potato starch, arrowroot (Maranta arundinacea), and tapioca.
180
How are all root starches sold?
As fine powders, also called flours.
181
Tapioca is extracted from what?
Yuca root, also called manioc or cassava.
182
Yuca would not be confused with what?
Cactus yucca.
183
Yuca is a versatile root used where?
South America and the Caribbean in the same way potatoes are commonly used.
184
The most common starch, besides cornstarch, in America.
Yuca, or tapioca flour.
185
Why is tapioca flour more expensive than cornstarch?
It is imported, primarily from Thailand or Brazil, to America.
186
Besides being sold as finely-ground flour, tapioca is available as what?
Quick-cooking granules or as various-sized pearls.
187
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.
188
Granules and pearls tend to cook into a _____, less ____ texture than unmodified tapioca flour.
short, stringy
189
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.
190
Do tapioca pearls become translucent when cooked?
Yes, but they retain their size and shape in the finished product.
191
What are modified food starches?
Starches that have been treated by the manufacturer with one or more chemicals approved for use by government agencies.
192
Modified food starches are "designer starches." What does that mean?
They are designed by the manufacturer to have certain desirable features.
193
While any native starch can be modified, most modified food starches are made from what?
Waxy maize starch.
194
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.
195
Main reason to use a modified starch in a bakeshop.
Its added stability.
196
What other ways can starched be modified?
To slow or increase gelatinization or change their texture.
197
Why is Cloflo 67 called a cook-up starch?
Because it must be cooked like any regular starch.
198
Instant starches thicken and gel without what?
Heat
199
Are instant starches different from modified starches?
Yes, although most instant starches are modified.
200
Instant starches are sometimes called what?
Pre-gelatinized or cold-water swelling.
201
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.
202
While instant starches do not require heat, will heat damage the product?
No, they are safe to heat.
203
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.
204
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.
205
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.
206
How much more do specialty starches cost than regular?
Usually 2 to 3 times more.
207
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.
208
Are starch molecules packed in tight order inside of starch granules?
Yes
209
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?
Gelatinization
210
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.
211
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.
Amylose, properly
212
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.
213
Does mixing and stirring speed up the rupturing of starch granules?
Yes
214
As the starch solution cools, starch molecules slow down and _______, tripping additional water and thickening.
entangle
215
If there is a high enough concentration of entangled _______ molecules, the solution gels as it cools.
amylose
216
Is there an optimum amount of heat for maximizing thickening?
Yes
217
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.
218
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.
219
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.
220
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?
Yes
221
Does each type of starch have an optimum amount of heat for proper gelatinization?
Yes
222
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 ________.
cornstarch
223
Most times, unmodified root starches should not be brought to a _______.
boil
224
When cooked for too long, unmodified root starches become excessively _______ in _______. If this happens, the sauce or filling should be remade.
stringy, texture
225
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.
226
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.
227
What is by far the best solution to dealing with starch and acid?
Switching to a starch that is acid resistant.
228
The most acid-resistant starches are what?
Modified food starches, but root starches and waxy rice starch are somewhat more resistant than...?
229
Do sweeteners and fats slow the rate at which starch granules absorb water?
Yes
230
The more slowly they absorb water, the longer it takes starch granules to ________.
gelatinize
231
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.
232
Does sugar increases translucent of starch0thickened mixtures?
Yes
233
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.
234
If enough acid is present, gelatinization occurs so quickly that what?
The starch mixture appears not to thicken at all.
235
Describe undercooked starch mixture.
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Too thin
Gritty
Opaque
Raw starch taste
Tends to weep
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236
Describe overcooked starch mixture.
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Too thin; may be stringy
Smooth
Extremely clear
No raw starch taste
Does not weep
```
237
Name 5 native starches.
Cornstarch, potato, rice, arrowroot, tapioca
238
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.
239
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.
240
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.
241
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.
242
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.
243
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.
244
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.
245
Ideal uses of cornstarch.
Puddings, cream pies.
246
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.
247
Ideal uses for arrowroot.
Fruit pies and sauces.
248
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.
249
Ideal uses of tapioca.
Fruit pies, sauces, tapioca pudding.
250
Properties of waxy maize.
Moderate to high clarity.
Thickens, does not gel.
Relatively stable against acid, heat, mixing, freezing.
Relatively clean flavor.
251
Ideal uses of waxy maize.
Base for many modified starches; not typically available unmodified.
252
Properties of modified food starch.
High stable against acid, heat, mixing, freezing.
Variable gelatinization temperature.
Other properties vary with brand.
253
Ideal uses for modified starches.
Frozen foods
Steam table applications
High acid products
254
Properties of instant starch.
No heat required
| Properties vary with brand
255
Ideal uses for instant starch.
Last-minute plating
| Heat-sensitive products
256
Properties of flour.
Cloudy; yellow-tinged color.
Heavy body
Imparts a flavor; masks or mellows flavors.
257
Ideal uses for flour.
Pastry cream
| Home-style pie uses
258
Properties of gelatin.
```
High clarity, high sheen
Forms firm, bouncy gel
At typical usage levels, melts in mouth and at room temp
Clean flavor
Available as sheets, powder
```
259
Ideal uses of gelatin.
Gelatin desserts
Stabilized whipped cream
Confections (gummy bears)
260
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
```
261
Ideal uses of agar.
As gelatin substitute for:
a. vegetarians and people with religious dietary restrictions.
b. use with raw pineapple, etc.
262
Properties of pectin.
High clarity, high sheen
Thickens or gels
Clean flavor
Generally requires high acid and high sugar concentrations.
263
Ideal uses of pectin.
Fruit jams, jellies, fillings
Glazes
High-quality jelly confections.
264
To say that an ingredients provides a thickened or gelled texture to sauces, fillings, glazes, and creams is to say that it provides what?
Structure
265
Thickening and gelling is the formation of a very soft _____.
structure
266
Are thickening and gelling agents sometimes called stabilizers?
Yes, they provide undesirable changes in food.
267
What is starch retrogradation in simple terms?
The formation of too much structure.
268
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.
269
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.
270
Weeping is also known as what?
Syneresis
271
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.
frozen, refrigerated
272
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.
273
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.
274
What ingredients delay starch retrogradation?
Sugars, proteins, fats and emulsifiers.
275
Why are pastries slower to stale than breads and rolls?
They contain more starch retrogradation delaying ingredients.
276
How does gelatin stabilize whipped cream?
Primarily by gelling. This solidifies the walls surrounding air bubbles in whipped cream and prevents them from breaking.
277
What stabilizes frozen eggs whites primarily by thickening them?
Guar gum
278
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.
279
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.
280
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.
281
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.
282
Why are all starches and gums driers?
Because they absorb moisture and, often, fats and oils.
283
Why is cornstarch added to dry powdered mixtures?
To absorb moisture. This prevents caking and keeps dry powder free-flowing.
284
Is cornstarch added to confectioners' and icing sugar?
Yes
285
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.
286
How should thickening and gelling agents be stored? Why?
Covered so it prevents moisture absorption.
287
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.
288
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.
289
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).
290
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.
291
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.
292
What destroys amylase and other enzymes?
Heat
293
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.
294
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.
295
Good rule of thumb for cooking time of cornstarch.
Bring to a boil and boil gently for 2 or 3 minutes.
296
Should root starches be brought to a boil?
No, heating them like cornstarch mixtures is too much.
297
Should starch mixtures be constantly stirred?
Yes, to prevent scorching or burning.
298
Best way to cool for a creamy, smooth texture.
Stir while cooling for smooth, creamy texture; for maximum thickening and gelling, cool without stirring.
