CHAPTER 9: THICKENING AND GELLING AGENTS Flashcards
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.
Egg
What is an emulsion of butterfat droplets in milk?
Heavy cream.
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.
thousands
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.
Proteins
Often, how many amino acids are linked together in a single protein molecule?
Thousands
More than ____ common amino acids make up proteins.
20
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?
Yes
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.
whipped
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?
No
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?
Calve’s hoofs.
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?
Powdered
Bloom scale is a rating that was invented when?
1800s
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.
230
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?
Powdered geltain.
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?
Bloom rating.
Are precautions taken to ensure all raw materials used in gelatin manufacture are from healthy animals that have been approved for human consumption?
Yes
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.
clump
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?
Yes
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?
Yes
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.
True
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?
30 minutes.
In theory, can sheet and powdered gelatin be used interchangeably?
Yes
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?
Yes
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?
Yes
Pectin thickens, but what does it do in the presence of acid and high amounts of sugar?
It gels.
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?
Dry powder.
Powdered pectin is generally extracted and purified from what?
Citrus peel or apple skins.
What is agar called in Japan?
Kanten
Agar is derived from what?
Any of several species of red seaweed (gracilaria or gelidium, for example).
Agar is also called what?
Agar-agar
How long have Asian cultures used agar?
For centuries.
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.
