Fats & Oils
Fruits & Vegetables
Hydrocolloids, Vegetable Gums
Meat, Fish, Poultry
Frequently Asked Questions
The learner will be able to --
- relate the molecular and granule structure of various native starches to starch paste and gel characteristics.
- explain the process of sol and gel formation in starch-water dispersions.
- understand and predict how sugars, acids, lipids, and other ingredients affect the quality characeristics of starch-containing products.
- predict how processing, production, preparation, and storage of starch sols and gels affect the quality characteristics of the final product.
- summarize processing and modification of starches and relate this to dispersion characteristics.
Starch is found in almost every typical meal from the Northern Hemisphere. For a truly useful nutrient it is critical that there be some understanding of what starch is and how preparation processes will influence it.
Starch is a polysaccharide (meaning "many sugars") made up of glucose units linked together to form long chains. The number of glucose molecules joined in a single starch molecule varies from five hundred to several hundred thousand, depending on the type of starch. Starch is the storage form of energy for plants, just as glycogen is the storage form of energy for animals. The plant directs the starch molecules to the amyloplasts, where they are deposited to form granules. Thus, both in plants and in the extracted concentrate, starch exists as granules varying in diameter from 2 to 130 microns. The size and shape of the granule is characteristic of the plant from which it came and serves as a way of identifying the source of a particular starch.
The structure of the granule of grain is crystalline with the starch molecules orienting in such a way as to form radially oriented crystals. This crystalline arrangement is what gives rise to the phenomenon of birefringence. When a beam of polarized light is directed through a starch granule, the granule is divided by dark lines into four wedge-shaped sections. This cross-hatching or cross is characteristic of spherocrystalline structures.
There are two types of starch molecules amylose and amylopectin. Amylose averages 20 to 30 percent of the total amount of starch in most native starches. There are some starches, such as waxy cornstarch, which contain only amylopectin. Others may only contain amylose. Glucose residues united by a 1,4 linkage form the linear chain molecule of amylose. Amylose is the linear fraction and amylopectin is the branched fraction.
Amylose molecules contribute to gel formation. This is because the linear chains can orient parallel to each other, moving close enough together to bond. Probably due to the ease with which they can slip past each other in the cooked paste, they do not contribute significantly to viscosity. The branched amylopectin molecules give viscosity to the cooked paste. This is partially due to the role it serves in maintaining the swollen granule. Their side chains and bulky shape keep them from orienting closely enough to bond together, so they do not usually contribute to gel formation. Different plants have different relative amounts of amylose and amylopectin. These different proportions of the two types of starch within the starch grains of the plant give each starch its characteristic properties in cooking and gel formation.
Starch in its processed, commercial form is composed of starch grains or granules with most of the moisture removed. It is insoluble in water. When put in cold water, the grains may absorb a small amount of the liquid. Up to 60 to 70C the swelling is reversible, the degree of reversibility being dependent upon the particular starch. With higher temperatures in irreversible swelling called gelatinization begins.
Composition of Starch
| || Potato || Cassava || Wheat ||Cornstarch |
|Moisture,% || 19 || 13 || 13|| |
|Ash,% || 0.4 || 0.2 || 0.2|| |
|Protein, % || 0.06 || 0.1 || || 0.4|
|Lipid,% || 0.05 || 0.1 || 0.8|| |
|Phosphorus% || 0.08 || 0.01 || 0.06|| |
|Amylose,% || 21 || 17 || 28|| |
|Micrograph || || || || |
1.Muhrbeck, P. and A.-C. Eliasson. 1987. Influence of pH and ionic strength on the viscoelastic properties of starch gels- a comparison of potato and cassava starches. Carbohydrate Polymers 7: 291-300.
Starch begins to gelatinize between 60 and 70C, the exact temperature dependent is the specific starch. For example, different starches exhibit different granular densities, which affect the ease with which these granules can absorb water. Since loss of birefringence occurs at the time of initial rapid gelatinization (swelling of the granule), loss of birefringence is a good indicator of the initial gelatinization temperature of a given starch. The largest granules, which are usually less compact, begin to swell first. Once optimum gelatinization of the grains has occurred, unnecessary agitation may fragment the swollen starch grains and cause thinning of the paste.
The gelatinization range refers to the temperature range over which all the granules are fully swollen. This range is different for different starches. However, one can often observe this gelatinization because it is usually evidence by increased translucency and increased viscosity. This is due to water being absorbed away from the liquid phase into the starch granule.
| Raw starch that has not had moisture added does not undergo gelatinization. By definition, gelatinization is a phenomena which takes place in the presence of heat and moisture. The dry raw starch, if heated, would undergo dextrinization. This certainly would affect the starch paste viscosity and starch gel strength. The paste viscosity would be decreased and gel strength decreased.|
If a "limited amount" of moisture is added to the raw starch you may get partial gelatinization. This condition exists in baked products.
| ||Cornstarch at a 5% level in 95% water would have a slight change occur if heat is initiated. Water might be slightly ADSORBED onto the surface of the granule. Actually, in the research from which these images came, I found that I got a difference in paste viscosity and ultimate op as measured by viscosity if I allowed cornstarch to sit in water at room temperature. This led me to believe that there is some initiation adsorption upon the granule at room temperature (27C).
| If this 5% dispersion of cornstarch was heated to 40C I would expect more water would be ADSORBED onto the surface of the granule, the hydrogen bonding between the starch polymers within the granule might begin to be loosened slightly. In some types of starches water might even begin to be ABSORBED into the granule. |
| If this 5% dispersion of cornstarch was heated to 50C I would expect more water would be ADSORBED onto the surface of the granule, the hydrogen bonding between the starch polymers within the granule would begin to be loosened.. This would allow the water to penetrate into the granule becoming ABSORBED by the granule. Additionally, some of the amylose may begin to work itself off the granule surface, thus, opening the structure even more.
| || If this 5% dispersion of cornstarch was heated to 60-65C I would expect more water would be ADSORBED onto the surface of the granule, the hydrogen bonding between the starch polymers within the granule would loosen. This would allow the water to penetrate into the granule becoming ABSORBED by the granule. Additionally, some of the amylose would work itself off the granule surface, thus, opening the structure even more. This in turn would allow even more of the water to become ABSORBED and more amylose to work itself out into a colloidal dispersion outside of the granule. The long amylose polymer is a colloid in characteristics. |
| ||This is intermediate between 60 and 70C. The precise changes are affected by rate of heating, condition of the starch and other factors.|
| If this 5% dispersion of cornstarch was heated to 70-90C I would expect more water would be ADSORBED onto the surface of the granule, the hydrogen bonding between the starch polymers within the granule would loosen. This would allow the water to penetrate into the granule becoming ABSORBED by the granule. Additionally, the amylose would work itself off the granule surface, thus, opening the structure even more. This in turn would allow even more of the water to become ABSORBED and more amylose to work itself out into a colloidal dispersion outside of the granule. The long amylose polymer is a colloid in characteristics.|
At some point between 60-95C we would likely have gelatinization occur. This might be measured by loss of birefringence, increased viscosity, translucency, increased susceptibility to enzyme action, x-ray diffraction or some other chemical or physical means. At this point, the starch granule is swollen as much as possible. It is a starch sol until you remove it from the heat and begin to allow the amylose and some amylopectin to recrystallize, i.e. realign.
| In some instances, when heated to 90C the starch granule could reach optimum gelatinization and be a nice swollen granule sack. In other cases, this may allow the sack to "implode" and loose their contents as there is not enough structure and hydrogen bonding to hold the polymers together. It is interesting that overcooking, as with overstirring, will decrease the starch paste colloidal sol viscosity. |
If a typical starch paste is allowed to stand undisturbed, inter-molecular bonds begin to form, causing the formation of a semirigid structure or gel. This gel is a structure of amylose, molecules bonded to one another and, slightly, to the branches of amylopectin molecules within the swollen granule. This phenomenon is sometimes called retrogradation. The conditions of gelation is critical to the ultimate rigidity of the final product. Gelation of starch occurs due to its 3-D structure.
A starch dispersion generally has high opacity and little clarity. The changes that occur during gelatinization concurrent with the swelling of the granule increased in translucency. However, it must be made clear that different starches will have different abilities. The clarity and translucency is affected not only by the degree of gelatinization and swelling of the granule but by the association of amylopectin and amylose. Craig et al.  indicates that a high clarity and almost no whiteness occurs within a starch paste itself because of few swollen granular remnants and the amylose and amylopectin have a stable conformation due to inter- and intra chain repulsion with little association. Moderate clarity and high whiteness occurs because, even with few granular remenants, the amylose and amylopectin have collapsed conformation due to interchain association of the polymers. Finally, he suggests that low clarity and low whiteness occurs when the grnules are swollen remnants and the amylose and amylopectin starch molecules have either collapsed or associated.
CHANGES IN GELATINIZATION OF STARCH
- hydration and swelling to several times original size
- loss of birefringence
- increase in clarity
- marked, rapid increase in consistency and attainment of peak
- "dissolution" of linear molecules and diffusion from ruptured granules.
- with heat removal, retrogradation of mixture to a paste-like mass of gel.
All these changes may occur with a typical "native" starch. We know they occur with a 5% cornstarch mixture. The problems and the "unusual" occurs primarily when we deal with modified starches.
|If gelatinization has occurred correctly and IF the starch is the correct type and concentration, upon removal from heat a three dimensional structure may form. This is a messy structure made up of cross-linking of amylose as an intra- and inter-molecular bonding within and exterior to the swollen starch granule. |
Factors Affecting Starch Paste Viscosity and Starch Gel Strength
|STRESS OR OTHER FACTOR||Stirring Amount and Type This is a gelatinized cornstarch dispersion that, likely due to stirring, the granules broke apart.|
|Types and Amount of Starch||Certain the type of starch will influence the characteristics of the starch paste viscosity and gel strength. Generally speaking, with "native starches" the greater the amount of amylopectin the more viscous the starch paste, whereas, the greater the amount of amylose the firmer the gel (greater the gel strength).|
|heating rate||It is of interest that, generally, the faster you heat a starch-water dispersion the thicker it will be at the identical endpoint temperature. This is of importance to those interested in household versus foodservice dispersions. |
|Each type of starch has the unique endpoint temperature at which it will undergo optimum gelatinization. |
If starch is not completely gelatinized it certainly will not have optimum starch paste viscosity or gel strength. If over gelatinized, the dispersion may have decreased starch paste viscosity and gel strength because the swollen granule easily fragmented with stirring or actually imploded due to the extensive loss of amylose from the granule.
|cooling and storage conditions|
|Research has well established that the cooling conditions will impact the strength of the gel. Generally, if cooled too fast, the amylose will not have time to form the vital micelles necessary for the three dimensional structure. If cooled too slowly, the amylose fractions will have a chance to align too much and become too close together and the liquid portion will not be trapped in the micelles. In both instances there will be weeping and syneresis. |
|dextrinization: heat||Heat dextrinization frequently occurs during the household production of gravies with meat drippings. Essentially, the heat will hydrolyze the starch polymers and the short chains mean that the granule will not remain intact. This means that the starch paste will be more runny with the dextrinization.|
Sugar affects the gelatinization of starch, whether a starch pudding or a high-moisture cake. In either instance, both research and qualitative observations have shown that sugar will delay or inhibit gelatinization of starch. The starch pudding may be less viscose or have a less firm gel. The cake may collapse as the structural contribution of starch is delayed or inhibited.
The type of sugar also influences the degree of gelatinization. As seen in the graph the types of sugar impact the degree, temperature and/or speed of gelatinization.
Bean, M.M. and W.T. Yamazaki. 1978. Used with permission, Institute of Food Technology
The reason for sugars delay upon the gelatinization of starch is still not clear. Generally, researchers indicate that it is likely due to the competition for water. It becomes less clear as to how this competition actually influences the water structure. Does it actually form the "hydrate" structure, does it affect its plasticity or mobility, or does it actually prevent the adsorption of water. This is the easy logical answer; however, there has been a number of researchers that indicate that sugar actually interacts with the amorphous areas of the starch granules. This interaction also leads to increased starch gelatinization temperature.
Johnson and other researchers observed not only was their a linear relationship between sugar concentration and onset of starch gelatinization. Bean and Yamazaki observed similar results. That is, as sugar concentration increased the onset of gelatinization temperature increased. Additionally, Johnson et al observed the order of effectiveness at delaying the onset of gelatinization, it was found that fructose was most effective followed by glucose, maltose, and sucrose.
fat: triglycerides, surfactants. Fats, particularly if surfactants or emulsifiers, may interfer with full gelatinization of the granules and thus decrease viscosity. Of course, one must not forget the actual formation of a physical barrier to water from fat.
|Dextrinization may occur due to acid and enzymes. In the making of lemon pudding or pie, if the lemon juice is added early in the gelatinization process, dextrinization of the starch will occur. This means that the amylopectin would not be as "bushy" as previously and the amylose would be of a shorter chain length. Thus, there would be decreased starch paste viscosity and gel strength.|
Fat, composed of triglycerides and surfactants, will serve to "waterproof" the starch granules so that water will not penetrate as readily during the gelatinization process. Thus, since the granules do not swell and the amylose does not exude from the granule and there will be a decreased starch paste viscosity and decreased gel strength.
The addition of sugar to a typical starch dispersion will serve to decrease starch paste viscosity and gel strength because the sugar will compete for water and it won't be available for gelatinization.
Johnson, J.M., E.A. Davis, and J. Gordon. 1990. Interactions of starch and sugar water measured by electron spin resonance and differential scanning calorimetry. Cereal Chemistry 67(3): 286-291.
Bean, M.M. and W.T. Yamazaki. 1978. Wheat starch gelatinization in sugar soutions. I. Scurose: Microscopy and viscosity effects. Cereal Chemistry 55(6): 936-944.
Just a note, one can determine the viscosity by a simple linespread test. This is the dumping of a portion of hot starch sol onto a diagramm of concentric circles. The spread determines the viscosity.
The first step would appear to be to understand the roles and functions of starch. Quality characteristics of the starch itself depends upon which role or function. These may be listed as:
gel forming agents
Modified Starches may be prepared as follows:
-"pear" and powdered starches
-acid-modified starches (thin cooking)
-white dextrins (dry heat)
-starch ethers and esters
-cationic (+) starch ethers
-linear starch fractions
|Many different parts of the plant may contain the amyloplasts or leucoplasts in the cytoplasm. This storage mechanism in the cytoplasm is present as organized plastids. In reviewing starch as food sources, it has been observed that the plastid and associated granules may take up much of the cell in seeds, tubers and root vegetables. |
It is of interest to know that the storage of starch in the leucoplasts is part of the photosynthetic cycle. A number of years ago, a forester was attempting to evaluate the affect of the light cycle and photosynthesis. The starch in pine needles was able to plot the day night photosynthetic cycle.
Modified from Lineback, D.R. 1984. The starch granule organization and properties. Baker's Digest 58: 16, 18.
| The starch granule is held within the plastid. The granule itself has an organized structure which can be seen in the diagram to the left. The amylose and/or amylospectin is laid down from the interior outward. There has been some interesting research that indicates that not only does the starch have a structural radiation out from the center of the granule, but there is other organizational patterns. There are different types of patterns to the x-ray diffraction. They are called either A, B or C pannterns This arrangement contributes to different crystallinities. X-ray diffraction patterns indicate that cereals give an A pattern; legumes, roots, and tuber starches give a B patterns; andC patterns occur as a between the two. It is likely that the A and B patterns are due to the crystallized amylopectin. |
| representation from T.J. Schoch. Brewer's Digest 37(2): 43. ||
There appears to be concentric layers of starch from the center. This historical representation indicates the light and dense packing. These may be due to the light-dark [daytime-night time] time periods. Work done at Oregon State University looked at these concentric circles using a scanning electron microscope to view the photosynthesis of pine starch. From this, they could plot the active light and dark periods in the forest, relating to the availability of light during the day. |
| ||Actually, the organized pattern is due to the arrangement of amylose, amylopectin and the lipid complex. The arrangement of these components will differ for different starches and within starch granules. This arrangement forms different gelatinization [swelling] characteristics and ultimate food quality characteristics.|
absorption: penetration of liquid into solid which contains a porous structure
adsorption: adherence of molecules of liquid, gas or solid to surface of a solid.
amorphous: has no crystalline structure. Amorphous candy are those such as lollipops, marshmallows, caramels.
amylase: an enzyme that hydrolyzes starch to produce dextrins, maltose, and glucose
amylopectin: is a larger molecule also linked 1,4 but with 4-5% of the glucose units linked alpha-1,6 at branch points (purplish color with iodine).
amylose: is the straight-chain fraction of starch made up of a polymer of glucose.
bacteria: microscopic, unicellular plants which do not contain chlorophyll; mostly 0.5-3um in size. They are responsible for much food spoilage and for disease; but are also made use of, as in biological oxidation, and fermentation, such as the pickling process and the souring of milk
beta-amylase: an enzyme that hydrolyzes starch by breaking off two glucose units at a time, thus producing maltose.
birefringence: the ability of a substance to refract light in two directions; this produces a dark cross on each starch granule when viewed with a polarizing microscope
blanc mange: is a milk dessert, flavored and thickened with cornstarch, flour, or gelatin and usually shaped in a mold.
carbohydrate: a category of organic compounds with carbon, hydrogen, and oxygen. In sugars, the ratio is approximate C:H:O [1:2:1] ratio.
carbonyl group: a ketone (-c=o) or an aldehyde (hc=o) group
cold water-swelling starch(CWS):
colloidal dispersion: state of subdivision of dispersed particles; intermediate between very small particles in true solution and large particles in suspensior; usually refers to the state of subdivision of dispersed particles; intermediate between very small particles in true solution and large particles in suspension
complex carbohydrates: carbohydrates made up of many small sugar units joined together, for example, starch and cellulose
corn syrup: is a corn sweetener which is a viscous liquid containing maltose, dextrin, dextrose, and other polysaccharides. It is obtained from the incomplete hydrolysis of corn starch. It is classified according to the degree of conversion which is expressed as the dextrose equivalent (DE), which is the measure of sweetness of the corn syrup as compared to that of a sucrose syrup.
covalent bond: a strong chemical bond that joins two atoms together
D.E.: Term used to indicate the degree of hydrolysis of starch into glucose syrup. It is defined as the total reducing sugar content expressed as dextrose, calculated as a percentage of the dry solids content (i.e. the higher the DE the more sugar and the less dextrins are present).
Liquid glucoses are commercially available ranging from 2DE to 65DE. A complete acid hydrolysis converts all the starch into glucose but produces bitter degradation products.
crystalline: the aggregation of molecules of a substance in a set, ordered pattern, forming individual crystals. Crystalline candy generally has sugar crystals.
crystallization: the formation of crystals from the solidification of dispersed elements in a precise orderly structure
crystallize: is to coat and impregnate (fruit or petals) with sugar as a means of preserving them: a box of crystallized fruits.
the formation of crystals from the solidification of dispersed elements in a precise orderly structure
dendritic: are fibers which carry message impulses toward the nerve cell from other cells and sensory areas of the body.
dextrins: mixture of soluble compounds formed by partial breakdown of starch by heat, acid or enzymes (complete breakdown yields maltose). Formed when bread is toasted. Nutritionally equivalent to starch; industrially used as adhesives in the sizing of paper and textiles, and as gums.
dextrinization: is the process of forming dextrins.
dextrose: is a corn sweetener which is commercially made from starch by the action of heat and acids or enzymes, resulting in the complete hydrolysis of the cornstarch. There are two types of refined dextrose commercially available. Dextrose hydrate, containing 9% by weight of water of crystallization and being the most often used and anhydrous dextrose which contains less than 0.5% of water. Corn sugar is a reducing water and produces a high temperature browning affect in baked goods. It is used in ice cream, bakery products, and confections. It is also termed glucose and corn sugar.
enzyme: catalyst produced by living cells. Composed of protein and destroyed by heat and protein coagulation; responsible for most of reactions carried out in living tissues. Some are composed of two parts: the apoenzyme, the protein which is inactive alone; and its prosthetic group, a small non-protein molecule normally derived from a vitamin.
enzymatic reactions: those that are catalyzed by enzymes, which are special proteins produced by living cells; a catalyst changes the rate of a reaction without itself undergoing permanent change.
fermentation: the transformation of organic molecules into smaller ones by the action of microorganisms; for example, yeast ferments glucose to carbon dioxide and alcohol. The products are used for "esthetics" in beverages and leavening in selected baked products such as bread and rolls.
freeze-thaw stability: usually used in connnection with starch to describe the ability of a starch paste or gel to be frozen and thaw without syneresis or weaping.
gel: a colloidal dispersion that shows some rigidity and will, when unmolded, keep the shape of the container in which it had been placed; a semi-rigid structure at room temperature.
gelatinization of starch: the sum of changes that occur in the first stages of heating starch granules in a moist environment; includes swelling of granules as water is absorbed and disruption of the organized granule structure.
gelation: the process of the formation of a gel, a semi-rigid structure at room temperature.
glucoamylase: an enzyme that hydrolyses starch by breaking off one glucose unit at a time, thus producing glucose immediately.
grain size: in regard to sugar is the size of a crystal as measured by the smallest sieve opening through which it can pass.
grind: is to reduce a foodstuff to small particles or powder by crushing it, such as to grind some black pepper over the salad | they grind up fish to make fish cakes. Also refers to the size of ground particles, especially ground coffee beans as only the right grind gives you all the fine flavor.
strong>hydration capacity: the ability of a substance, such as flour, to absorb water
hydrocolloid: a substance with particles of colloidal size that is greatly attracted to water and absorbs it readily; colloidal materials such as vegetable gums, that bind water and have thickening and/or gelling properties; large molecules, such as those that make up vegetable gums, that form colloidal dispersions, hold water, and often serve as thickeners and stabilizers in processed foods
hydrogen bond: the relatively weak chemical bond that forms between a hydrogen atom and another atom with a slight negative charge, such as an oxygen or a nitrogen atom; each atom in this case is already covalently bonded to other atoms in the molecule of which it is part.
hydrolysis: a chemical reaction in which a linkage between subunits of a large molecule is broken; a molecule of water enters the reaction and becomes part of the end products
hydrolyze: To split a substance and add the OH and the H of the water to the two halves. For example, cane sugar, C12H22O11, is hydrolyzed to glucose, C6H12)6, and fructose, C6H12O6; proteins are hydrolyzed to amino acids. Acid or alkali is usually needed as catalyst.
immiscible: describing substances that cannot be mixed or blended
malt processed barley: has been steeped in water, germinated on malting floors or in germination boxes or drums and later dried in kilns for the purpose of converting the insoluble starch in barley to the soluble substances and sugars in malt.
maltase: Enzyme that splits maltose (malt sugar) into two molecules of glucose; present in the pancreatic juice and intestinal juice.
maltodextrins: is the product obtained form the partial acid or enzymatic hydrolysis of starch, in the same manner as corn syrup except the conversion process is stopped at an earlier stage. It has a dextrose equivalent of less than 20 and basically is not sweet and is not fermentable. It has fair solubility. It functions as a bodying agent, bulking agent, texturizer, carrier, and crystallization inhibitor. It is used in crackers, puddings, and candies.
maltose: malt sugar, maltobiose; 4-ortho-gamma-D-glucopyranose. Double molecule of glucose which is hydrolyzed during digestion to glucose. Does not occur in foods (unless specifically added as malt) but is formed as an intermediate during acid or enzymic digestion of starch. 33% as sweet as sucrose; a reducing sugar.
mill: to beat, it is best done with a rotary beater, milk dishes, such as cocoa, are milled to remove scum formed during heating; refers to grinding of flour - "to mill"
modified starches: are natural starches that have been treated chemically to create some specific change in chemical structure, such as linking parts of the molecules together or adding some new chemical groups to the molecules. The changes alter physical properties that improve the performance of the starches in food preparation.
non-reducing end: in a polysaccharide or oligosacchride is the end which does not have a reducing agent. It lacks a free glycosidic hydroxyl.
oxidized starches: is starch which is produced by treating aqueous starch suspension with dilute sodium hypochlorite containing a small excess of caustic soda (NaOH) untile the desired degree of oxidation is reached. The slurry is then treated with an antichlor, such as sodium bisulfate, adjusted to the desired pH, filtered, washed, and dried. It still retains its original granule structure and is insoluble in water. It is extremely white, has decreased viscosity, is relatively clear and shows a reduced tendency to thicken when cooled. Its food applications are those where high solids and low viscosity are desired.
pasting: as applied to wine or cidermaking, pasting is a professional word meaning clarifying or fining.
polymerization: the formation of large molecules by combining smaller chemical units.
pregelatinized starch: is starch which has been processed to permit swelling in cold water, unlike natural starch which requires heating. The processing usually consists of cooking starch slurries, drying, and grinding to a fine powder. It is used in instant puddings, cake mixes, and soup mixes at from 1 to 5%.
retorted: canned or sterilized by processing in a pressurized retor or vessel in order to raise the temperature to 121 C to kill microorganisms.
retrogradation: the process in which starch molecules, particularly the amylose fraction, reassociate or bond together in an ordered structure after disruption by gelatinization; ultimately a crystalline order appears
roux: means russet. It is simply flour and butter fried together, and used for thickening and coloring soups and gravies. There are two kinds, one brown, and the other white.
starch: is a carbohydrate consisting of glucose units containing amylose and amylopectin which contribute to varying starch properties. Starch is insoluble in cold water but upon heating, the starch granules swell and burst, forming starch paste. Starch sources include arrowroot, corn, potato, rice, sago, tapioca, waxy corn, and wheat. Starches are modified by treatment to alter their functional properties. Terminology designating these starches include: acid modified corn starch, food starch modified, modified food starch, oxidized corn starch, pregelatinized starch, thin boiling starch, and wheat starch, gelatinized.
starch granule: a particle formation starch is stored; composed of millions of starch molecules laid down in a very organized patter; the shape of the granule is typical for each species; starch molecules are organized into tight little bundles, called granules, as they are stored in the seeds or roots of plants, the granules with characteristic shapes and sizes, can be seen under the microscope.
syneresis: Oozing of liquid from gel when cut and allowed to stand (e.g. jelly or baked custard).
the oozing of liquid from a rigid gel; sometimes called weeping
tapioca: Starch prepared from the root of the cassava plant. The starch paste is heated to burst the granules, then dried either in globules resembling sago or in flakes. The term is also used for starch in general, as in manioc tapioca and potato flour tapioca.
texture: Combination of physical properties perceived by senses of kinaesthesis (muscle-nerve endings), touch (including mouth feel), sight and hearing. Physical properties may include shape, size, number and conformation of constituent structural elements
viscosity: term used of liquids to define their resistance to flow (i.e. the internal friction).
waxy maize starch: is the starch portion of waxy corn, consisting essentially of amylopectin. It yields pastes that are almost clear upon cooling and are noncongealing. It forms a translucent, water soluble coating when dried in thin films. It is used to thicken a variety of foods such as sauces and puddings. It is also termed waxy starch, amioca.
waxy rice starch: is a rice starch which contributes freeze-thaw stability to sauces and puddings but may provide objectionable flavor. It is used in sauces and puddings.
whitesauce: is generally used to denote the best class of pastry-flour, but in the baking-trade it is a term used to disguise the intorudction of alum into breadmaking. They are then known as sharp whites, stuff, or bakers' stuff, consisting of powdered alum and flour in equal parts, or one pound of coarsely-ground alum to three pounds of salt.
Updated: Wednesday, May 23, 2012.