Continuous production of pretzels

A continuous process for producing pretzels is disclosed in which an essentially dry mixture containing flour, corn syrup solids and salt is introduced into an extruder; water is injected into the extruder barrel to bring the water level of the mixture to between 19% and 25%; the material is extruded at non-cooking temperature to form a self-supporting ribbon of extrudate; the extrudate is sprayed with a caustic solution; and the sprayed extrudate is baked. The claimed process is adaptable to the continuous production of a filled pretzel product.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to methods for the continuous production of pretzel 
products. In particular, the invention relates to a method of producing 
pretzels on a continuous basis which employs relatively low moisture. In 
one embodiment, the invention relates to the continuous production of a 
pretzel product which is subsequently continuously filled with an edible 
material such as a creamy or paste-like material. 
2. Prior Art 
The making of pretzels is an art which has been practiced for many years. 
Pretzels are baked products which are produced from essentially rather 
simple recipes containing flour, water, salt and other ingredients. 
Pretzels have a characteristic flavor which is imparted by chemical 
reactions occurring during baking and by flavoring ingredients such as 
malt and yeasts. They are especially characterized by the presence of a 
darkly browned exterior surface. It has long been known that the browned 
surface effect can be obtained by coating the surface of the dough 
mixture, prior to baking, with a caustic solution such as 0.5% aqueous 
NaOH. Caustic treatment not only imparts the desired browning during the 
baking cycle, but also contributes to the development of characteristic 
pretzel flavors. 
In the prior art, pretzels have been produced from dough mixtures 
containing relatively high water contents, i.e , about 40% to 50%. Since 
the final pretzel has a moisture content of only about 2.0%, this requires 
a considerably high energy input during the baking cycle in order to drive 
off water and achieve the desired final moisture content. The high 
moisture content of prior art pretzel doughs makes them relatively soft, 
so that they tend to lose their shape easily. This is particularly true 
during the caustic treatment where the pretzel dough tends to become very 
pliable. Consequently, it has beeen difficult to maintain a shaped dough 
profile, such as a tubular or C-shaped profile suitable for injection of 
filling materials, using uncooked pretzel doughs of the prior art. This 
has made it difficult or impossible to produce filled pretzel products in 
a continuous process. 
U.S. Pat. Nos. 4,162,333 and 4,241,649 disclose a method for producing a 
filled pretzel product. In accordance with this method, short tubular 
pieces of pretzel dough are extruded onto supporting pegs on a conveyor 
belt. Extrusion is conducted in a discontinuous manner as the pegs on the 
conveyor belt are indexed past the extruder die. The supporting pegs are 
required to prevent the central cavity of the pretzel dough from losing 
its configuration, thereby ensuring a cavity of appropriate dimensions for 
receiving the filling material. The individual tubular pieces are 
subjected to a number of further processing steps, including baking and 
filling. In addition to being discontinuous in nature, the process is 
extremely cumbersome inasmuch as it requires complex material handling 
equipment to handle each small tubular piece of dough without allowing it 
to lose its tubular configuration. 
U.S. Pat. No. 3,615,675 describes a process for continuously producing a 
filled, puff-extruded farinaceous product. In this process, a farinaceous 
mixture having a moisture content of 10% to 25% is extruded through an 
annular die at a temperature exceeding the boiling point of the moisture 
in the mixture so that the farinaceous material expands due to the 
flashoff of moisture upon emerging from the extruder. An edible, creamy or 
paste-like material is continuously deposited into the hollow core of the 
puff-extruded material by pumping the filling material through a filling 
tube which extends coaxially through the die orifice into the central core 
of the extrudate. In this process, the puffed extrudate sets up to form a 
dimensionally stable cylinder, susceptible of continuous processing, due 
to the flashoff of moisture upon emerging from the die. The puffed product 
which is produced has texture and flavor characteristics which are 
different from those of pretzels. 
It is an object of the present invention to provide a method for producing 
pretzels in a continuous operation which enables the pretzels so produced 
to be continuously filled with an edible filling material. 
It is a further object of this invention to provide a method for 
continuously producing pretzels which is energy efficient and which 
minimizes the amount of energy input required to dry the product to its 
final moisture content. 
Other objects and advantages of the invention will be apparent to those 
skilled in the art from the following description. 
SUMMARY OF THE INVENTION 
The present invention provides a method for the continuous production of a 
pretzel product. The method of the invention employs a dough composition 
containing about one-half the moisture of a conventional pretzel dough 
composition so that the amount of energy required to reduce the product to 
its final moisture content in the baking oven is minimized. The dough is 
more self-supporting than conventional pretzel doughs of the prior art 
when formed into a shape such as tubular or C-shaped profile. The method 
of the invention involves the production of a self-supporting continuous 
ribbon of unbaked pretzel dough, whose cross-section can be of any desired 
shape, preferably a generally annular or C-shaped cross-section having a 
hollow core suitable for filling with an edible creamy or paste-like 
material. Because the dough ribbon produced in the process of the 
invention is more dimensionally stable than shaped pretzel doughs of the 
prior art, it maintains its cross-sectional configuration during 
subsequent baking and filling operations. 
In accordance with the teachings of the invention, there is provided a 
method for the continuous production of a pretzel which is capable of 
being continuously filled, the method comprising introducing to the feed 
zone of an extruder a mixture comprising flour, corn syrup solids and 
salt, said mixture having a moisture content not greater than about 14%; 
injecting water into the mixture in the extruder barrel to raise its 
moisture content to between about 19% and 25%; mechanically mixing the 
ingredients in the extruder barrel through the action of the extruder 
screw(s) while maintaining the temperature of the mixture below about 
140.degree. F.; extruding the mixture through a die to form a continuous 
ribbon of extrudate; transporting the extrudate ribbon through a spray 
zone where it is sprayed with a caustic solution; and transporting the 
sprayed ribbon through an oven where it is baked to a final moisture 
content from about 1.0% to 3.0%. Optionally, after spraying with the 
caustic solution and before baking, the pretzel surface can be salted with 
pretzel salt. 
In one embodiment, the invention provides a method for continuously 
producing a filled pretzel product. The extrudate, produced as described 
above, is produced by extrusion through a die having a generally C-shaped 
cross-section to produce an extrudate having a filling cavity running 
continuously along its length. An edible material, preferably having a 
creamy or paste-like texture, is continuously injected into the filling 
cavity either before or after baking, preferably after baking. 
An essential feature of the method of the invention is the maintenance of 
relatively low temperature of the material in the extruder, i.e., below 
about 140.degree. F. Accordingly, the extruder is not employed to 
partially or completely cook the pretzel dough, nor is it employed for the 
purpose of puffing the extrudate by causing moisture to flash off when the 
extrudate emerges from the die.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with the practice of this invention, an essentially dry 
mixture of materials is provided to the feed zone of the extruder. By 
"essentially dry" is meant that no water other than the moisture 
inherently present under ambient conditions is added to the feed materials 
prior to introduction into the extruder. With the exception of added 
water, which is introduced once the materials are inside the extruder 
barrel, any materials which are conventionally employed in pretzel dough 
formulations can be employed in the feed mixture. The predominant 
ingredient in the feed mixture is flour, preferably wheat flour. 
Generally, the feed mixture contains from about 70% to 85% flour, 
preferably from about 73% to 85% flour. All percentages given herein are 
by weight, unless otherwise indicated. 
The feed mixture also contains corn syrup solids. Corn syrup solids serve 
several functions in the dough mixture employed in the method of the 
invention. They enhance surface browning, which is highly desired in a 
pretzel product. Moreover, the corn syrup solids have a plasticizing 
effect on the mixture when exposed to the shearing action of the extruder 
screw(s), without which it would be difficult or impossible to extrude the 
mixture at the low moisture level employed. As those skilled in the art 
are aware, corn syrup solids are produced by dehydrating partially 
hydrolyzed corn starch (starch hydrolysates). Starch hydrolysates are 
generally classified on the basis of dextrose equivalence (D.E.) values. 
As used herein, the D.E. value refers to the reducing sugars content of 
the dissolved solids in starch hydrolysates, expressed as percent 
dextrose, as measured by the Luff-Schoorl method. The method is described 
in NBS circular C-40, page 195 as appearing in "Polarimetry, Saccharimetry 
and the Reducing Sugars" by Frederick J. Bates and Associates. Corn syrup 
solids are dehydrated corn starch hydrolysates having D.E. values greater 
than 20. We prefer to employ corn syrup solids having a D.E. value from 
about 34 to about 38. Typically, such corn syrup solids have a 
carbohydrate composition with about 7% monosaccharides, 32% disaccharides, 
13% trisaccharides, and 48% tetrasaccharides or higher (dry basis). The 
feed mixture contains from about 9% to 15% corn syrup solids, preferably 
from 10.5% to 13.5%. 
The feed mixture also contains salt. Salt contributes to the characteristic 
flavor of the pretzel and helps to develop dough elasticity. Salt is 
present in the feed mixture in an amount from about 0.5% to 1.5%, 
preferably from 0.6% to 1.2%. 
Other additives which are conventionally present in pretzel dough 
formulations or which assist in extrusion can also be present in their 
usual effective amounts. Advantageously, a monoglyceride is present in the 
feed mixture in an amount from about 1.0% to 2.5%. Monoglycerides are 
monosubstituted fatty acid esters of glycerol in which the fatty acid 
moiety can be partially or completely saturated. They are usually employed 
in the food industry in the form of a steam-distilled fraction of 
vegetable oil containing at least 90% monoglyceride molecules. 
Monoglycerides which can be employed include, for example, Panalite 90 D 
(Paniplus, Inc., Olathe, Kansas). The monoglycerides act as a dough 
softener, if present in appropriate amounts. The monoglycerides can also 
act as extrusion aids to impart a smooth surface to the extrudate and 
ultimately to the finished product. Without such an extrusion aid, the 
extrudate tends to have a rough surface which is not consistent with the 
consumer's perception of a pretzel surface. It has also been found that 
the use of non-stick die surfaces such as Teflon.RTM. die surfaces, 
enhances product surface smoothness. These can be provided either by 
coating the die surfaces with Teflon.RTM. or by milling the die from a 
Teflon.RTM. block. 
The feed mixture may also incorporate, as an extrusion aid, an oil or a 
fat. The fats or oils which can be used can be derived from animal or 
vegetable sources, with vegetable oils generally being preferred. The fat 
or oil, if present, is generally present in the feed mixture in an amount 
from about 1.0% to 4.0% thereof. If desired, the fat or oil, in a liquid 
state, can be metered into the extruder separately from the other feed 
mixture ingredients. In addition to acting as an extrusion aid, the fat or 
oil tends to prevent swelling, shape deformation, or bubble formation in 
the product during baking. 
Other ingredients which optionally can be present in the feed mixture 
include, for example, conventional pretzel flavoring agents. Foremost 
among these are malt and yeast. Malt, in the form of liquid malt, is 
generally present in an amount from about 1.5% to 2.5% of the feed 
mixture. Alternatively, dry powdered malt can be used in an amount from 
about 1.0% to 2.0% of the feed mixture. Yeast, in the form of dry baker's 
yeast, is generally present in an amount from about 1.5% to 2.5% of the 
feed mixture. 
As previously indicated, no water other than that inherently present in the 
ingredients is added to the feed mixture prior to feeding to the extruder. 
Consequently, the moisture content of the feed mixture provided to the 
extruder does not exceed about 14%. 
The method of the invention can be understood with reference to the single 
FIGURE. FIG. 1 represents schematically a preferred embodiment of a 
production line suitable for the continuous production of filled pretzels 
by the method of the invention. The essentially dry mixture described 
above is provided to an extruder, indicated generally by 10, by feeding 
the mixture in preblended form from the extruder feeder hopper 36 into the 
extruder 10 by means of a metering screw 50 and feed port 44. Preferably, 
the feed mixture is fed to the extruder 10 at a rate such that the 
extruder screws 40 are maintained in a starved condition; that is, the 
feed rate is less than the maximum conveying capacity of the screws 40. To 
produce a uniform extrudate from the feed mixture, it is preferred to 
employ an extruder of the twin-screw variety. A twin-screw extruder is 
preferred because it provides a homogeneous extrudate having a uniform 
extrudate velocity which is important to the drying and continuous filling 
of the product. The extruder consists generally of two screws 40, one of 
which is shown in FIG. 1, which are disposed in parallel within an 
appropriately configured extruder barrel 38. The screws 40 are driven by a 
motor 34 through appropriate gears, thrust bearings, etc. (not shown). The 
extruder screws 40 co-rotate. The flights and shafts of the two screws 40 
are disposed in relation to each other in such a way that when they are 
rotated in the same direction, they wipe each other clean of material 
being extruded. This type configuration is preferred over a single-screw 
configuration because soluble and insoluble proteins and carbohydrates 
present in the pretzel dough mixture could otherwise cause the material to 
stick to the screw, blocking the needed conveying action of a single-screw 
extruder. Advantageously, the extruder can be jacketed for the circulation 
of cooling water to control the temperature of the material in the 
extruder barrel. Extruders of the type described are widely commercially 
available. A suitable extruder for use in the practice of the invention is 
a Baker Perkins Model No. MPF-50D twin-screw extruder (Baker Perkins, 
Grand Rapids, Michigan). The configuration of the screws 40 is preferably 
such that they impart relatively low shear to the mixture in the extruder. 
Low-shear screw configurations are well known to those in the extrusion 
art. The screw configuration should be one which is conducive to thorough 
mixing of the ingredients in the mixture. The design of an appropriate 
screw configuration is well within the skill of those in the art without 
undue experimentation. 
After the dry mixture has been introduced to the extruder 10 at feed port 
44, the conveying action of the screws 40 causes the material to move 
forward in the direction of the extruder die 46. Immediately downstream of 
the feed port 44, water is injected into the material through an injection 
port 42. Water is injected at a rate which brings the water content of the 
material in the extruder barrel 38 to between about 19% and 25%, 
preferably 20% to 22%, based on the total weight of the material and 
included water. Additionally, oil may be metered into the barrel if it has 
not been premixed with the other dry ingredients. 
As the material moves forward in the extruder barrel 38, the mixing action 
of the screws 40 causes the ingredients to be thoroughly admixed. An 
essential feature of the invention is the maintenance of noncooking 
conditions in the extruder 10. Cooking generally begins with starch 
gelatinization which occurs at temperatures exceeding about 150.degree. F. 
Accordingly, the temperature of the mixture is maintained below about 
140.degree. F. This can be facilitated by the external application of 
cooling, as necessary. For example, cooling water can be circulated in 
jackets around the extruder barrel. The circulation of cooling water can 
be regulated using conventional temperature sensing and control equipment 
to maintain the desired material temperature in the barrel. 
The mixture emerges from the extruder 10 through a die 46 to form a 
continuous ribbon 32 of extrudate. The configuration of the die orifice 
can be selected to provide any desired cross-sectional configuration to 
the ribbon 32. Generally, a round cross-section or, in the case of a 
pretzel which is to be filled, an annular or generally C-shaped 
cross-section, will be preferred. If desired, the die 46 may contain 
several adjacent orifices to form parallel ribbons 32 of extrudate. Due to 
the relatively low moisture content of the extrudate, it forms a ribbon 32 
which is self-supporting. The ribbon 32 can be assisted in its forward 
movement by conventional takeoff devices (not shown). 
The ribbon 32 of extrudate is passed through a spraying station, indicated 
generally by 16, where it is sprayed with caustic solution. The caustic 
solution is preferably an aqueous solution of from about 0.4% to 1.5% 
NaOH, most preferably 0.5% aqueous NaOH. The caustic solution is applied 
at a temperature from about 180.degree. F. to 200.degree. F. The spray 
station has a supply tank 24 equipped with temperature control means, from 
which the caustic solution is drawn by means of a pump 22 through piping 
20 and thence through spray nozzles 18 located so as to spray the top and 
sides of the moving ribbon 32 of extrudate. A collector 26 located below 
the moving ribbon 32 collects the caustic runoff and recycles it to the 
tank 24 by means of a pump 48. A sufficient amount of caustic solution is 
sprayed to completely coat the outer surfaces of the ribbon 32. 
In the embodiment shown in FIG. 1, following the spraying station 16, the 
ribbon is salted with pretzel salt at a salting station 52. Conventional 
seasoning distribution equipment, such as a vibrating pan, can be used to 
apply the pretzel salt at the salting station 52. The ribbon 32 is next 
transported to an oven 28. 
Typically, the oven temperature is from 450.degree. F. to 550.degree. F. 
The residence time in the oven 28 is such that the product is cooked to a 
final moisture content of from about 1.0% to 3.0%, preferably from 1.5% to 
2.5%, and the desired surface browning effects are achieved. 
The baked ribbon 32 of pretzel dough is then cooled at a cooling station 
54, where it is cooled by conventional means such as by blowing cool air 
across its surfaces. 
In the embodiment of the invention shown, the extrudate is produced in an 
annular or generally C-shaped configuration by extrusion through an 
appropriately configured die. There is thus created a ribbon 32 which has 
a central cavity running axially therethrough. An edible material, 
preferably an edible creamy or paste-like material is employed to fill the 
cavity, e.g., cheese paste, sugar starch paste, peanut butter, etc. The 
edible material can be continuously injected into the cavity of the moving 
ribbon 32 of baked pretzel product at a filling station 56 by means of 
conventional filling nozzles, metering pumps or manifolds (not shown). 
Injection of filling material is indicated schematically by means of an 
arrow. The baked and filled ribbon is then passed to a cutting station 30, 
where it is cut into pieces of desired length using conventional cutting 
equipment. 
Alternatively, a filled pretzel product may be formed by injecting the 
edible filling material into the cavity of the moving ribbon of extrudate 
prior to baking. However, this requires that the filling material be 
thermostable at the baking temperatures employed. For example, the filling 
material can be introduced continuously into the hollow core of the 
unbaked extrudate by pumping it through a filling tube that extends 
through the extruder die 46 coaxially into the hollow core of the 
extrudate. A suitable filling tube and die arrangement for accomplishing 
this is described, for example, in U.S. Pat. No. 3,615,675. 
The following example is intended to illustrate further the practice of the 
invention and is not intended to limit its scope in any way. 
EXAMPLE 
The following ingredients were dry blended: 
______________________________________ 
Ingredient Parts by Weight 
______________________________________ 
Pretzel flour 79.40 
Salt 1.00 
Monoglycerides (Panalite 90 D) 
1.30 
Corn Syrup Solids (Maltrin M365, D.E. 36) 
12.25 
Soybean oil (75.degree. F. melt) 
2.00 
Liquid malt 2.00 
Dry yeast 2.00 
______________________________________ 
The dry blended ingredients were fed to the feed port of a Baker Perkins 
Model No. MPF-50D twin-screw extruder equipped with low-shear screws. The 
extruder had the following screw configuration, proceeding from the inlet 
of the barrel towards the die: 
(1) a 10" long metering screw; 
(2) a 31/2" long 30.degree. forward paddle section; 
(3) a 3" long single lead screw; 
(4) a 2" long 60.degree. forward paddle section; 
(5) a 6" long lead screw; 
(6) a 2" long 60.degree. forward paddle section; 
(7) a 3" long single lead screw. 
The extruder was equipped with a water injection port about 3 in. 
downstream of the material feed port. The extruder die contained 2 
C-shaped orifices arranged in a horizontal row with the openings of the 
"C's" at the top. The extruder was operated at a screw speed of 70 rpm to 
achieve a throughput of approximately 100 lb/hr. Water was injected 
through the injection port at a rate of 8.4 lb/hr. The temperature in the 
extruder barrel just prior to discharge achieved a steady state at 
approximately 104.degree. F. The material exiting the extruder was 
uncooked, had a moisture content of 20.6% and formed self-supporting 
C-shaped ribbons capable of being baked and filled continuously in 
downstream processing steps.