Yeast Donut Technical Help

Yeast Donut Technical Help 

Remember, Yeast Raised Donuts are not cakes, but are living systems due the yeast fermenting the dough. The fermentation is vital to the end product. Always trust fermentation in making yeast donuts. It is extremely rare for any production problems to originate from excess fermentation of the yeast donut. It is better to think of a yeast donut as a fried bread product. 

There is usually more than one way to solve anyone problem in yeast donuts. However, there is usually only one way that will solve the problem without creating new problems. Bakery Science is here to assist you through these problems. Call us when you need help. 

Fermentation of Yeast Donuts 

Yeast must ferment the dough in order to produce a satisfactory donut. NEVER underestimate the importance of fermentation in yeast donuts. The fermentation process is a complex series of reactions that produces carbon dioxide, alcohol, and other chemicals. The pH level of the donut dough drops as the fermentation continues. These chemicals and the yeast activity mellow the wheat gluten. The result is a far superior dough that has better volume, shelf life and taste. 

When yeast is first added to the donut dough, it is still in a relatively dormant state induced by the final stages of its manufacturing process. This is especially true if dried yeast is being used. proof times are very short when compared to bread and it is vital to take advantage of every opportunity to gain fermentation during this short process. If no prefermented dough (Scrap) or brew is added to the dough, the yeast activity is relatively low. The semi dormant yeast will still produce carbon dioxide to leaven the dough but the other by-products will not be produced giving the donut dough the strength that is needed. 

High sugar levels and salt will retard fermentation, high water levels speed up fermentation. Since these factors can not be changed, the only good way to get adequate fermentation is by controllinq temperature, time and yeast levels. Low levels of sugar act as food for yeast and sugar will speed up the fermentation. However, at the higher sugar levels, the osmotic pressure exerted by the sugar will slow down the yeast. In a lean yeast donut sugar will speed up fermentation, but in a rich dough, the sugar will slow it down. It is vital to be aware of this difference.
The goal of fermentation is matching the time when the yeast is producing the maximum amount of carbon dioxide when the gluten is the strongest. This will produce yeast raised donuts with the best volume.

Age and Development of Yeast Donuts 

Fermentation of yeast donuts is one of the most import aspects of yeast donut production. Lack of fermentation of yeast donuts is also the number one issue in bakeries with problems.
Age or fermentation can come from three sources, biochemical, chemical, and mechanical development. Biochemical age comes from the yeast fermentation. The longer the yeast donut dough and the flour is exposed to fermentation, the 

older the dough is. This biochemical fermentation is due to the activity of the yeast forming a variety of acids and alcohols that interact with the flour. Chemical age comes from additives added to the dough such as L cysteine, acids, enzymes etc, that react with the flour and/or enhance the yeast environment. Mechanical age comes from mixing. A slightly over mixed dough will act like a old dough to a limited degree. The opposite will happen to a slightly under mixed dough. 

Using these principles, fermentation, mixing and formulation will results in the correct parameters. For example if your doughs are acting a little old, reduce mix time, fermentation or both. 

Scrap Dough and Yeast Donuts

Scrap dough and brew are the two primary sources of pre-ferment in yeast donuts. The flour coming from the brew is only 30% of the total flour in the dough. In other words only a small portion of the flour in the final yeast donut dough has been fermented when only brew is used. The scrap dough will add more fermented flour as well as some very active yeast. Scrap will always improve the quality of your yeast raised donuts. 

Two things to remember are to never use scrap fresh off the table and never use too much very old scrap. Very old scrap is broken down and is wet. Very old scrap will ruin any yeast donut dough. It is best to fill the scrap buckets 2/3 of the way full. When the scrap has fermented to the point where the bucket is full, the scrap has enough fermentation. Scrap that is 1 to 2 hours old is ideal.
 
Old scrap that is to old will be over gassed bucky, wet and sticky. Once the dough gets to the point where it gets very warm (approximately 120F) The yeast will begin to die releasing glutathione which is a powerful reducing agent. The glutathione will begin to break down the gluten releasing the water resulting in a very wet sticky dough. Never used more than a small amount of this type of scrap in a dough. As a rule it is usually better to trash the old scrap rather than use it. 

The amount of scrap and the amount of fermentation the scrap has received will drastically effect the mix times. In other words the more the gluten has been exposed to fermentation before mixing to the lower the amount of time is needed to develop the dough in the mixer. Adding scrap to the beginning of the mix will reduce the mix time as well since the new flour will be exposed to the by products of fermentation during the mixing. 

Floor Time of Yeast Donuts

Floor time is the time the donut dough needs to relax after the mixing process. The mixing process puts a lot of mechanical abuse on the dough. The donut dough needs to recover from the abuse before it is allowed to continue. There is not a right time or a wrong time but the dough and the final product must be observed to determine the proper floor time. Floor time also serves as additional fermentation. Remember the yeast added to the dough takes over 45 minutes to become fully active.

A freshly mixed yeast raised donut dough will be softer and highly extensible. A donut dough that has received a little floor time will start to get spongy and will break clean when stretched. A fully matured dough will be dry and very mellow, it will break clean and sharp with minimal elasticity.

Floor time is related to mixing. If a dough is over mixed, it requires more floor time for the gluten to recover. An under mixed dough will require less floor time due to less mechanical abuse.

In yeast donuts, a dough with inadequate floor time will exhibit the tendency to have the beginning of the dough to be sticky, This results in misshaped donuts. The first donuts at the fryer will also be small with the donuts getting bigger as the dough experiences more fermentation.

Excessive floor time can also cause problems. Excessive gassing will cause problems during extrusion. The end of the dough may be too old.

Proofing of Yeast Donuts

Proofing is the final fermentation stage. If everything is correct during the proofing stage the donut dough will reach its maximum strength during the latter stages of the proof when the yeast activity is at its greatest. This will result in a yeast donut with good volume with good spread.

The first zone of the proofer should be slightly more humid allowing the yeast donut to spread more. The donut should feel velvety soft but never wet and sticky. The second zone should always be slightly dryer. This allows the skin of the yeast donut to dry out slightly. This helps with gas retention and strength. The proofer should be monitored frequently to determine if the conditions are right. Slight variations in the dough and in the fermentation will require changes in the dry and wet bulb settings.

Blisters on yeast donuts are caused by excessive dryness in the proofer. A very dry skin will form a skin that moisture can no escape during the first stages of frying. The rapid release of steam will form a pocket (blister) during the first 10 seconds in the fryer. I have never seen dockers, needle wheels and the like actually work in production. The best way to eliminate blisters in yeast donuts is by increasing water in the dough and/or moisture in the proofer. A quick way to test this is to spray the donuts with water on the side that is getting the blister (after proofing) and watch the results.

The best way to judge the proof of yeast donuts is by final product. The internal temperature can also be used to determine the degree of proof. The internal temperature will vary from process to process and product to product. However, it should be fairly constant in your operation. A yeast donut with a normal proof time of approximately 30 minutes should reach an internal temperature of 105F plus or minus 3F at the end of the proof. Short proof times require higher internal temperatures of 110F and higher.

Too Iow an internal temperature can result in raw spots in the finished donut. The fryer can not be expected to cook out the donut if it is too cold before entering the fryer

Never proof by the dry bulb and wet bulb settings. Always feel the yeast donuts and observe the product in the fryer. Compare the beginning of the doughs to the ends before making adjustments. Proofers with higher air velocities will need a wetter proofer and low velocity proofers need a drier proofer. 

Another fault caused by incorrect proofing is white spots on the surface of donuts. White spots on yeast donut surface can be caused by too wet a proofer. When the donuts get sticky in the proofer, they stick to the tray and will get concave bottoms. This will result in white spots. Do not proof wet. A drier box is critical to getting a good donut. 

This advice may sound contradicting. But the most important thing is to feel the product and adjust from experience.
Frying of Yeast Donuts 

The fryer is the point where all decisions concerning fermentation, mix time, mix temperature, floor time, and proof time are made. Never bake by numbers always observe the final product and make adjustments.
Most yeast donuts will fry in 90 to 110 seconds at 375F. Never increase the fry time to increase the fat absorption. If the fat is too low, there is a problem in formulation.
 
Critical Control Points of Yeast Donuts  

Yeast Donut Brew

Set temperature of brew determines rate of fermentation. Higher temperatures speed up fermentation drastically. This temperature should be recorded for every brew. This is not the temperature of the water, it is the temperature of the brew after it has been set.

Rise temperature is final temperature set temperature. This is an indication of the amount of fermentation. The fermentation activity of the yeast creates heat. This temperature should be recorded for every brew.
Ferment Time Increasing and decreasing the total ferment time will change the age of the brew.

TTA and pH Measure at least once a day. The value should be compared to the rise temperature. There should be consistency between the values or the set temperature and/or the ferment time should be adjusted

Scrap in Yeast Donuts

The amount of scrap should not vary as this will alter the age of the dough. Scrap is very important in order to obtain the desired level of age as the level is not high enough to depend on it exclusively.

Ferment time on scrap Fresh scrap should never be used. Fresh scrap has practically no value. also allow the scrap to proof up before use. Very old burnt out scrap should be added only in small quantities as this will have a negative effect on the Ratio of age of scrap and amount of scrap The older the scrap is, the less is needed. The younger the scrap is the more that is needed. The two are directly related.

Mixing of Yeast Donut Dough

Mixing times will vary. Each donut dough must be evaluated by the mixer. The age of the brew and the scrap will alter the mix times. Changes in the flour will also alter the mix time. It is vital to monitor this closely.

The final temperature will determine the rate of proof. The final product should determine the yeast donut dough temperature. The final mix temperature should be recorded for each dough.

Degree of development Since there is a possibility of changes in the brew, scrap and flour, the donut doughs must be evaluated for mix development. Elasticity and extensibility of the doughs must be evaluated.

Floor Time of Yeast Donuts

Floor time is related to the amount of development from mechanical, biochemical and chemical sources. The more the donut dough is over developed the longer the floor time must be to allow the dough to recover. Underdeveloped doughs need less time. If there is consistency in the development of the doughs there will be consistency in floor times.

Temperature and humidity of first zone. The first zone of the proofer should be moister than the second zone. donuts should be evaluated in the box several times per shift to determine if the conditions are correct. The yeast donuts should feel velvet like and not dry. The yeast raised donuts should not feel sticky. This allows the yeast raised donut to flow on the shelf with out sticking to the shelf.

Proofing of Yeast Raised Donuts

Temperature and humidity of second zone The second zone needs to be dryer to allow a skin to form. The skin will give the donut support and help retain gases during frying. If blisters are forming, the box is too dry. Once again, this should be evaluated several times per shift.
Internal temperature of donut leaving proofer The internal temperature will determine the degree of proof.

Proof box temperatures and dough temperatures need to be adjusted to optimize final product characteristics. Optimal temperature can vary slightly but for your current product it should be 105. F.

Fat Absorption

Yeast donut fat absorption is an important quality parameter that should be monitored. Low fat levels produces a yeast raised donut that has a shorter shelf life and will have glazes and icings that break down more quickly, Too high a fat level will produce a donut that is more expensive and will have a greasy mouth feel.

Yeast donut fat levels (% of fat of the finished donut with no icings or glazes) should range from 24% to 33%. Type of donut being produced, size, shape and desired shelf life and eating characteristics will determine the fat level.

The most important factor that will alter the fat level is the shortening added to the dough. As more shortening is added the fat level goes up.

A yeast donut with more fat in the dough will be more tender and will absorb more fat from the fryer. A yeast donut ring dough (honey dip) will have about 6 to 10% fat based on flour or approximately <5% fat and a very rich fried honey bun will have 20% fat based on flour or approximately 9.5% fat. The higher fat product will absorb more fat from the fryer resulting in a finished fat level that is up to 10% higher than the very lean product.
 

Flour protein will change the fat absorption. Gluten will form a film that will block the fat from entering the donut. The higher the level of protein, and the higher the strength, the more that the gluten will block the fat. There is a Significant difference between the varieties of flours (spring wheat vs. winter wheat, clear flours vs. normal extractions) Spring wheat flour has the highest level of strong proteins. Clear flours are high in protein, but the quality is very low. Do not  use clear flours in donuts, (More on this listed below.).

Sugar acts a tenderizer and will increase fat absorption. Higher sugar levels will weaken the gluten and will allow more fat to be absorbed. The osmotic pressure of the sugar will draw water from the gluten. This has 2 effects. First the donut dough will appear to be wetter (softer) and the fermentation will slow down as the levels increase.

As you can see, the function of the ingredient influences the fat absorption of the finished donut. In addition, the dilution effect is another factor. As more shortening and sugar and other non strengthening ingredients are added the more the strengthening ingredients are diluted. The addition of sugar and shortening can have quite dramatic effects on the finished fat level.

Critical Ingredients in Yeast Donuts

 
No technical discussion on yeast raised donuts can be complete with out a discussion on ingredients. The most important ingredient is flour,Sugar, Yeast, Shortening.

Flour for Yeast Donuts

Yeast donuts are made from wheat flour. Wheat flour is the only flour that contains gluten which is the protein responsible for the cell formation. All other flours (rye, barley, corn etc) do not contain gluten.

Types of Wheat

There are many types of wheat (soft wheat, hard wheat, red wheat, white wheat). Soft wheats are low in protein and the proteins are weak. Soft wheats are used to produce cake and pastry flours. Hard wheats are higher in protein and the proteins are stronger.

Hard wheats are used to produce bread flours. Yeast donuts are made with hard wheat flours but can be supplemented with soft flour depending on geographical location and/or elevation. Just remember to much hard flour will result in donuts that are tough to eat and too much soft flour will collapse donuts when iced or glazed..

Spring Wheat vs. Winter Wheat

There are basically two types of hard wheats, spring and winter. Normally a winter wheat flour is used in table cut donuts. In some regions a winter/spring blend is used. A yeast donut should be tender. Pressure cut donuts need a stronger flour due to the abuse of pressure extrusion. Spring wheat flours are normally used.

Spring wheats are planted in the spring in the northern states and harvested in the fall. Spring wheats are much higher in protein than the winter wheats are used to produce high gluten flours. Average high gluten flours range in protein from 12.5% protein to 14% protein. The proteins in spring wheat flour is much stronger than winter wheat proteins.

Winter wheat are planted in the winter in the central and southern states and are harvested in the late spring. Winter wheats are used to produce bread flours. Average hard red winter wheat flours contain 10.0 to 11.0% protein.

Flour Specifications for Yeast Donuts

The most important specification is the protein level. Lowering the protein level to save money will result in collapsing donuts with high fat levels. Using too high a protein will result in tough donuts with low fat levels.

The next most important specification is ash. Ash level indicates the degree of extraction or how many pounds of flour was produced from the wheat. The higher the extraction, the higher the ash, the higher the protein and the lower the protein quality. DO NOT ACCEPT HIGH ASH LEVEL FLOURS. These flours are no good for producing quality donuts. Winter wheat ash levels should be below .49 and spring wheat ash levels should be below .53.

There are many other parameters that measure protein quality such as the farinograph which accurately predict protein quality.

Abuse

High gluten flour can produce a much richer product than winter wheat due to the dilution of the proteins. The richer the product, the stronger the flour should be. Other factors are the abuse the flour receives during mixing and processing. Very high speed mixers and abusive pumping will require a stronger flour. Gentle mixing and no pumping does not require a stronger flour

Which Flour to Use
Picking the correct flour is vital to producing quality yeast raised donuts. Flour can effect many different aspects of the finished donuts such as volume, toughness, fat absorption, and shelf life. All of the parameters of the finished product must be taken into consideration when selecting the flour.

SUGAR in Yeast Donuts

Sugar has several functions in a yeast raised dough. The obvious is sweetness, however, this is the least important. In a yeast donut there is Dextrose, Sucrose and other sugars.

Sugar acts as a tenderizer which will make the donut less chewy and will increase the fat absorption. Sugar will also under go browning reactions during frying to give crust color, dextrose is gives more crust color than sucrose.

The most important function is a food for the yeast. The yeast need a supply of quick energy for the quick fermentation that is used. Dextrose will be the primary source of food for the yeast during the fermentation.
Low levels of sugars speed up fermentation considerably, but as the sugar levels rise, sugar will inhibit fermentation due to the osmotic pressure exerted on the yeast.

Sugar will also compete with the gluten for the available water. To see this, mix a dough with no sugar and very low water. The dough will be very stiff. Add sugar at the end of the mixing and the dough will soften up considerably. This is why high sugar doughs are so low in sugar. This magnifies the osmotic pressure and slows the fermentation down even more. Doughs with very high sugar levels need very high levels of yeast to compensate for the slow fermentation.

SHORTENING in Yeast Donuts

There are many types of shortenings on the market. The best shortening to use is a yeast raised vegetable shortening. Animal shortenings have too much flavor for a yeast donut and animal shortenings are very bad tasting on shelf life. Animal shortenings go rancid too fast. Use vegetable shortenings for the bland flavor.

A yeast raised shortening is a partially hydrogenated oil with monoglycerides added. Partial hydrogenation makes an oil solid at room temperature. Oils can be used but they will make a donut that collapses more and with a higher fat absorption. There are Trans Fat Free Shortenings available. Avoid esterified shortenings as they can have off flavors. Palm based fats work, but the flavor is different and is not a pleasant as soy. New shortenings are coming out every month, the best choice is to test and see the results.
 
Monoglycerides is a very general term. Only one monoglyceride is functional in yeast raised dough and that one is glycerol monostearate (GMS). GMS is the only monoglyceride that functions as a crumb softener. GMS content of a good yeast raised shortening will be 5 to 10%. Powdered monoglycerides are a blend of GMS and GMO. The GMO is used to make the GMS soluble in water. Straight GMS must be melted into fat in order for it to be functional. GMO is not functional in yeast raised products even though it is a monoglyceride. In other words you are paying top dollar for a non functional ingredient!

YEAST in Yeast Donuts  

Yeast is a living ingredient. Care must be taken with yeast so that it is not stressed or killed. Compressed yeast or cream yeast is the best yeast to use. This yeast has been stressed the least. Compressed yeast is in a semi dormant state that will allow the yeast to have a shelf life of about 7 days. Do not use old yeast. Do not use hot yeast that has broken down. Yeast should feel cold and dry, not sticky. Many yeast companies are putting codes of 2 weeks on yeast. Do not keep your yeast that long. Get more frequent deliveries. Compressed yeast must be kept cold and not allowed to warm up.

Once compressed yeast is warmed up the yeast starts fermenting itself (eating itself) and the temperature increases more. This process is very hard to stop and will destroy the yeast. Once the yeast cell has been ruptured due to this process the enzymes that where contained in the yeast are released into the dough. These enzymes will destroy the dough. Yeast must be kept in a sealed bag, this will also keep the yeast in a dormant stage. Dry yeast takes much too long to come out of dormancy.

The dry process stresses the yeast far too much and the short fermentation of yeast donuts does not give the yeast a chance to "come back". Dry yeast requires much longer fermentation times. Pure granulated sugar and salt are poisonous to yeast. Never scale the yeast directly on top of sugar or salt. Keep the two separated until mixing.

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