Zhiyin Qin
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Improvement in the Making of the All-Time
American Treat: Deep-fried Doughnut
Abstract
Have you ever wondered where did doughnuts come from and how did it come about?
Most importantly, how do you make doughnuts? What does it take and what’s the process
of producing such a delicious sweet treat? Doughnuts have had a long history so let me
tell you all about the making of doughnuts. In addition, the engineering behind
developments and improvements of doughnut making are also a focus of discussion.
Keywords
Snacks, doughnuts, deep-frying, food engineering, processing
Introduction
Think about some of the most popular sweet treats, pies, danishes, croissants,
cakes, cookies, and brownies. Seems like something is missing from the list, come on,
Think harder. Yes, you got it. It is the all-time famous sweet treat, the Big-O-Ring,
doughnuts. Have you ever wondered where did doughnuts come from and how did it
come about? Most importantly, how do you make doughnuts? What does it take to
produce it and what’s the process of producing such a delicious sweet treat? Lastly, how
have doughnut making changed or could be changed technologically to keep doughnuts
remain popular on the market?
History
The exact beginning of doughnut is unclear but existences of food that resemble
doughnuts did appear very early in history. Ancient Egyptians were believed to have
eaten fried cakes [1]. Doughnut-like fossil remains have been discovered by
archaeologists in prehistoric Native American settlements [2]. It was around the 15th
century that the Portuguese adopted the Hawaiian malassada, which is fried dessert
dough, and spread it around the globe during colonization [1]. These food items all
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familiarly resemble doughnuts because they were also fried dough. They could possibly
be the early origin of doughnuts indicating primitive existence of doughnuts.
The historical evidences and development of doughnuts have also been recorded.
The term doughnut first came from Washington Irving in 1809 when he wrote about
Dutch settlers boasting about dishes of balls of sweetened dough in the “History of New
York” [1]. Thus, doughnuts were believed to be derived from the Dutch olykoeks
meaning oily cakes. The origin of the hole in the doughnut was believed to have
originated from a New England ship captain named Hanson Gregory [2]. The captain’s
mother made deep-fried dough for the captain so he can bring it along with him on his
voyage [2]. The captain claimed he gave the doughnut its hole in the middle when he cut
the hole using the top of a round tin pepper box [2]. This gave doughnuts their common
ring shape. In 1872, John F. Blondel patented the doughnut cutter but the first doughnut
machine did not come until around 1920 in New York City [1]. Since then, the inventor
of the doughnut machine, Adolph Levitt, had made a fortune from selling fried doughnuts
[2]. Doughnuts became a popular sensational food in the 1930s and continued to flourish
since then. The first Krispy Kreme opened in 1937 [1]. Thereafter, numerous Krispy
Kreme stores continuously opened and the first Dunkin’ Donuts opened in 1950 [2].
Engineering Influences in Doughnut Making
The growth of the doughnut industry was largely enabled due to the engineering
innovations and development of the doughnut machine. When Adolph Levitt sold fried
doughnuts from his bakery, the tasty treat brought in numerous customers and that
induced Levitt to invent the first doughnut machine [2]. The doughnut machine allowed
faster production of doughnuts to satisfy high customer demand. As a result, greater
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consumption of doughnuts spurred the growth of the doughnut industry. This trend
continued when the Ring King Junior came to existence in the early 1950s [2]. The Ring
King Junior was an advanced automatic doughnut maker that produced 60 dozen
doughnuts per hour [3]. With the Ring King Jr., Krispy Kreme quickly expanded into a
chain of 29 store-factories in 12 states by late 1950s [2]. As the Ring Kind Jr. was
replaced by newer and more elaborate equipments, doughnut making and doughnut
production were furthermore influenced. A modern Belshaw doughnut making Century
system can make 90 to 720 dozen doughnuts per hour [4]. Whereas the Belshaw HV
Industrial Systems can make 1000 to 3000 + dozen doughnuts per hour [4].
Besides faster doughnut production of uniform quality, there are other
improvements in doughnut making such as shape and flavors to ensure doughnuts remain
popular on the market. The technological creation of doughnut cutters was key to the
development of greater variety in doughnut shapes. Doughnut cutters can cut the dough
into different shapes before frying giving a variety of after-frying doughnut shapes. As
shown in figure 1, besides the typical ring-shaped doughnut, doughnuts can come in
spheres, twists, and more.
Nicole Saidi
Figure 1. A selection of sweets from Sublime Doughnuts in Atlanta, Georgia.
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As for development of flavors, some of the engineering innovations include doughnut
glazer, tumbler, filler machine and more. A doughnut glazer can produce glazed
doughnuts with chocolate or icing surface layer. A tumbler is a revolving drum into
which doughnuts can be sent for sugar coating. Jelly filled doughnuts can be produced
with a filler machine where filling is injected into the doughnuts. All of these different
flavors are pictured in figure 1. Study had shown that business in the U.S. doughnut
market alone valued 3 to 4 billion dollars annually [5]. This showed that doughnuts
remain a popular sweet treat today. Since we have come to discuss the shapes and flavors
of doughnuts today, before discussing further engineering influences in doughnut making,
let’s do an overview of the modern doughnut making process to give you a little more
background.
Process
The two common types of doughnuts are yeast-raised doughnuts and cake doughnuts.
The process in making one type of doughnut is different from the other type. From figure
2, you can see a flowchart of the doughnut making process for both types of doughnuts.
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Figure 2. Donut Flowchart
The first step in making doughnuts is mixing all the ingredients from a formulated
doughnut recipe. Uniform mixing is very important. Hydrating the ingredients will cause
leavening effects in the dough [6]. Cake doughnuts undergo an alkali and acid reaction to
produce carbon dioxide but yeast doughnuts undergo fermentation where yeast consumes
sugar in the flour to release carbon dioxide. Thereafter, the carbon dioxide causes the
dough to expand and rise up. Although it takes longer, yeast provides better inflation in
the dough and so yeast doughnuts have a lighter and fluffier texture than cake doughnuts.
Cake doughnuts are cake-like and denser than yeast doughnuts. Referring to figure 3,
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when the dough is ready, it will be extruded out of the mixer through the doughnut cutter.
For cake doughnuts, the batter extruded out of the cutter is directly transferred to the fryer.
However, for yeast doughnuts, cut doughnut batter must undergo the proofing stage
where the cut doughnuts are conditioned for transfer to the fryer. Look at figure 4 for a
visual. During the frying stage, the dough loses moisture and fry oil would be absorbed.
After frying, the doughnuts are to be cooled to an internal temperature of 32-35 degrees
Celsius [7]. The last stage would usually be some type of coating or glazing to add
sweetness to the doughnuts and for aesthetic appeal reasons. That is how ring-shaped
doughnuts are generally made. The following media links can provide more detailed
description and visualization of the doughnut making process and equipments.
Belshaw Donut Robot® Mark 6 Doughnut System producing yeast-raised doughnuts:
http://www.youtube.com/watch?v=_D2Q99X3Db8
Belshaw Donut Robot® equipment use in cake doughnuts making process:
http://www.belshaw.com/donutrobot/video
madehow.com
Figure 3. Doughnut making: mixing and extruding
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madehow.com
Figure 4. Doughnut making: proofing, frying and glazing
Engineering Influences in Doughnut Making Continued
Although the improvements in shape and flavors in addition to its delicious taste
have kept doughnuts remain popular on the consumers market today, these developments
might not be enough to keep it a popular consumer treat in the future. Consumers today
are driven to demand food products that are lower in oil or fat content because of health
concerns. Although deep-fried doughnuts are delicious sweet treats, discussion centered
on their potential health hazards repeatedly catch people’s attention. As a result, new
food engineering technologies that comply with both health concerns and consumer
preferences are developing. Some of such technologies are vacuum frying and edible
coatings or bio-films in food engineering. These developing engineering technologies
might be key to keeping doughnuts popular on the consumer market when consumers are
so driven for healthier food products today.
Vacuum Frying
Vacuum frying can possibly be an alternative to traditional frying in providing
food products with reduced oil content that still retain the desired flavor and texture of
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traditionally fried foods. During vacuum frying, food product is heated at a pressure well
below atmospheric pressure so the boiling points of oil and water in food product are
decreased [8]. There are five main advantages in the vacuum frying process. They
include reducing oil content in the fried food, preserve natural color and flavors of the
food due to low temperature and oxygen control during the process, giving less negative
effects on oil quality, decreasing acrylamide content during frying and preserving
nutrients in the food [8]. Referring to figure 5, during the process, the food product will
be placed in the fryer in the vacuum chamber. Then the transport belt will carry the
finished product out of the fryer and into a container.
Food Engineering Reviews
Figure 5. Schematic diagram of semi-continuous vacuum fryer designed by Pe´rez-Tinoco et al.
Unfortunately, the vacuum frying method seemed to be unrefined and imperfect for
doughnuts. As study shown, the oil content of cake donuts was lower with vacuum frying
than with atmospheric frying [9]. However, the oil content of yeast-raised donuts was
lower with atmospheric frying in comparison to vacuum frying [9]. The doughnuts deepfried under atmospheric conditions at 140°C for 5 minutes had higher sensory scores than
any of the other processing conditions for both cake and yeast-raised doughnuts. This
indicated that although vacuum frying has shown to work for fruits, vegetables and other
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food products in providing its five given advantages compared to atmospheric frying,
further research for vacuum frying doughnuts still need to be done to ensure it is indeed a
better alternative method to traditional frying in terms of less oil uptake and equal or
better sensory taste.
Edible Coating
Edible coating is another method used in food engineering processing of various
food products for lower oil content. Edible coatings are directly applied to the surface of
food products before frying. Edible coatings have various uses like protecting perishable
food products from deterioration by retarding dehydration, suppressing respiration,
improving textural quality, helping to retain volatile flavor compounds and reducing
microbial growth [10]. Methylcellulose(MC) and Hydroxypropyl Methylcellulose
(HPMC) are hydrocolloid
coatings discussed specifically for doughnuts [10]. Another
coating discussed for deep-frying doughnuts is gum tragacanth(GT) [5]. The application
of these edible coatings is that they act as barrier to lipid absorption
by food during deep fat frying [10]. “Cellulose derivatives like methyl cellulose exert
thermogelation when heated, and on cooling, it reverts back to the solid
state [5]. As a result, these coatings prevent oil absorption during deep-drying and
sometimes even help doughnuts retain more moisture content because of the coatings’
hydrophilic character [5]. The “effect of coatings in preventing oil absorption is
determined by its mechanical and barrier properties, which depend on its composition
and microstructure, and on the characteristics of the substrate being applied to [7]”. MC
coating was highly selected for doughnuts because it showed the minimal oil absorption
compared to HPMC coatings. “MC coatings also have better moisture barrier
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performance than HPMC coatings due to the lower hydrophilic character of MC [7]”.
Both MC and GT coatings are effective in reducing lipid absorption during the deepfrying of doughnuts. However, it was shown that GT coating is more effective than MC
coating in preventing oil absorption during deep-frying of doughnuts [5]. Sensory
evaluation results indicated that edible coatings had no significant effect on quality
attributes (texture, flavor, color) of the doughnuts. Fermented doughnut with GT coating
had the highest quality score in terms of taste, appearance, aroma and more [5]. Thus, it
can be strongly concluded that the application of certain coatings like GT could be an
alternative solution to traditional frying in order to comply with both health concerns and
consumer preferences.
Conclusion
As shown, the technological development of the doughnut making process and
equipments greatly influenced doughnut making and doughnut production. However,
fried foods have been highly related to obesity and other health problems. Thus, reducing
the fat content of fried foods is at focus. Improvements in reducing fat absorption during
deep-frying of doughnuts have continuously been developing. Vacuum frying can
potentially be used in place of traditional frying when the method is more refined and
improved for doughnuts. The application of coatings is believed to be an alternative
solution to traditional frying that complies with both health concerns and consumer
preferences. The reason is because edible coatings appear to be an effective method for
reducing oil uptake as demonstrated on studies carried out on traditional frying. Although
not all of these techniques have been 100 percent refined and put to use, it is in hope that
as food engineering technology advances, more and more improvements will hopefully
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continue to happen. For example, improvement in vacuum frying for doughnuts could
possibly be achieved by combining both vacuum frying and edible coatings, resulting in
doughnuts with much lower fat content but with equal or better taste than traditionally
deep-fried doughnuts. Unfortunately, journals articles on the application of coating
combined with vacuum frying have not been found [8]. However, further research could
easily be done in the future to make doughnuts more consumer-friendly by lowering
health hazards but at the same time maintain the quality and sensory tastes of doughnuts.
Consequently, the public can benefit from the improvements in food engineering while
doughnuts can remain a competitively popular sweet treat on the market even though
consumers demand healthier food products.
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Reference:
[1] Wayne Creekmore. "Fried Dough History." OSO-ONO. 2003.
[2] David A. Taylor. "The History of the Doughnut." Smithsonian. 03 1998:1-3.
[3] “Krispy Automatic Ring-King Junior Doughnut Machine.” National Museum of
American History. 1997.
[4] “Commissary and Industrial Donut Systems.” Belshaw. 2011.
[5] Z.S. Zolfaghari, M. Mohebbi, and M.H.H. Khodaparast. (2013). Quality Changes of
Donuts as Influenced by Leavening Agent and Hydrocolloid Coatings. Journal of Food
Processing and Preservation, 37(1), 34-45.
[6] "Cake Doughnuts." Bake Info. Baking Industry Research Trust, 2011.
[7] "Yeast Raised Doughnuts." Bake Info. Baking Industry Research Trust, 2011.
[8] A. Andres-Bello, P. Garcia-Segovia, and J. Martinez-Monzo. (2011). Vacuum Frying:
An Alternative to Obtain High-Quality Dried Products. Food Engineering Reviews, 3(2),
63-78.
[9] Hwang, J., Sung, W., & Shyu, Y. (2009). Effects of Atmospheric and Vacuum Frying
on the Quality of Donuts. Taiwanese Journal of Agricultural Chemistry and Food
Science, 47(5), 238-249.
[10] M. Garcia, V. Bifani, C. Campos, and M.N. Martino, et al. Food
Engineering:Integrated Approaches. New York: Springer, 2008. 225-41.