| Donut Glaze and Icing Technical Help |
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| Written by Rick Cavanaugh | |
| Thursday, 09 August 2007 | |
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Donut Glaze Technical Help The most important thing to know in shelf stable donut glazes and icings is that a cooked glaze must be used. There are many RTU (ready to use) glazes and icings on the market. They are very convienent, but they have very little stability. If you want a glaze or icing that has a shelf life of greater than 6 hours, the glaze must be a cooked type glaze and it must contain a high quality stabilizer that is activated by boiling in water for 3 minutes. There is currently no way around this. Icing and glazes for sweet goods and donuts are water icings that are non aerated and consist of mostly sugar and water. Typically glazes are used on yeast raised donuts and honey buns where icings are used on sweet dough, Danish, honey buns, cake donuts and yeast raised donuts. For icings the water content is 12 to 15% and the sugar content is 82-85%. The will be a more viscous product that is applied to the top surface only. Usually more white in color. Many icings contain white color such as titanium dioxide. The lower water content and the fact that it is applied on a cooled baked good allows for an improved weepage free shelf life. For donut glazes the water content is 20-25% and the sugar content is 70-75%. This will make a less viscous product that will flow over the entire product almost enrobing the donut. The end glaze will be slightly clear. Glazes are usually applied on hot donuts and glazes have more weepage and breakdown issues on shelf life. Moisture from the donut will transfer to the glaze. The water activity of a donut is around 0.93 aw where the water activity of a glaze approximately 0.71 aw. As long as there is a significant difference in the water activities of the 2 phases, there will always be moisture migration going from the donut to the glaze causing problems. A high quality agar in the donut glaze stabilizer helps minimize this. The icing or glaze system is a two phase system consisting of small sugar crystals dispersed in a saturated sugar solution stabilized with agar. The key to making a successful glaze or icing is to develop a product which contains the minimum amount of syrup. Therefore, maintaining the quality of a glaze or icing is dependent on controlling the syrup in the system. The worst mistake is adding water to the glaze to thin it down. Never add water to thin down a donut glaze or icing. Ingredients in Donut Glaze Sugars in Donut Glaze Stability of donut glazes and icings is dependent on maintaining a constant sugar crystal to syrup ratio during shelf life. Changes of more syrup during shelf life results in weepage. Loss of moisture will result in cracking and chipping of the icing. Moisture loss from the glaze or icing can also result in osmotic pressure of the lower water activity glaze or icing pulling moisture from the higher water activity dough. This will cause substantial drying of the crumb. Maintaining the syrup to sugar ratio is critical in maintaining a satisfactory product over shelf life. Granulated sugar is used in the boiling phase (syrup phase) of the process. This sugar is important for several reasons. First the sugar will raise the boiling point of the syrup allowing a hotter glaze or icing to be made. In addition this hot syrup will create a super saturated sugar solution upon cooling which will help maintain the sugar solids to syrup ratio. Powder sugar usually 6x sugar is used for the fine sugar crystal phase. Humectants such as corn syrup or invert sugar can absorb water and help prevent evaporation from the donut icing or glaze to a limited extent. However, they can also create sticky glazes and icings and will retard drying. Melting of the glaze or icing can occur during shelf life. Humectants are used to a very limited degree usually used to help improve shine and limit cracking. Typical levels are 2-4% of the powdered sugar content. Water in Donut Glaze The amount of water in an icing or glaze is usually the controlling factor in the stability of the glaze or icing. It is very important to limit the amount of water. Even a small amount of extra water in the syrup can have significant increases in glaze weepage. Glazes and icings with higher water content are thinner and are easier to apply. This is especially true for donut glazes. Using higher water levels will result in significantly more glaze weepage. A better way would be to add more granulated sugar to the syrup to increase the glaze temperature. Higher glaze and icing temperatures will result in thinner easier to apply glazes and icings. Shortening in Donut Glaze Two types of fats are typical in glazes and icings: Hard fat flakes with a melting point of 120F and higher and standard bakery shortenings with melting points of 110-120F. Shortenings help speed up drying rates of glazes and icings and they can provide some stability. Fat can also help maintain the sugar to syrup ratio by making fat barriers that prevent sugar and syrups from migrating. Shortening also assists with helping the icing or glaze adhere to the baked good. Levels vary with climate and packaging types. In the past levels of 1% to 4% or the powder sugar levels were typical. We have seen improved packaged glaze stability for levels up to 10%. Higher levels are useful in items to be frozen. However, excess levels of hard fat flakes can produce brittle icings and glazes that can chip and flake and can set too fast and can be waxy. In packaged donuts the fault level is well above 10% fat. Soybean oil is occasionally used at low levels to improve gloss. Emulsifiers in Donut Glazes Emulsifiers such as high melting point monoglycerides can be added to the boil phase at 1/2% of powder sugar to help bind water by creating an emulsion with bound water. Excess levels can cause a dull glaze. Processing glazes and icings The process of making donut glazes and icings is a 2 or better yet a 3 stage process. The first stage is the boiling of the stabilizer. The agar MUST be boiled to fully hydrate the gum. This must be done if you wish to have a stable donut glaze or icing. The water and the stabilizer is added to the steam kettle and this is brought to a rolling boil for 3 minutes. Enough time and temperature is needed to fully hydrate the agar to gain full functionality. Do not skimp on this stage. The second stage is to add the sugar to the boil and reboil. Sugar will compete with the agar during the hydration stage. That is the reason why you should do this in 2 steps. Many do this in a single step, but the results are not as consistent. Bring the syrup to a boil a second time for 2 minutes and add the hard fat, shortening and emulsifiers. The syrup should then be mixed into the powdered sugar. The process for a liquifier vs. a vertical mixer are slightly different. Vertical mixer- slowly add syrup over 3 to 4 stages to prevent lumps. Liquidifier- add all powdered sugar and allow the high shear machine smooth out glaze. Application of Donut Glazes Apply donut glazes and icings at 140 to 145F. This recommendation is much higher than those of the past. Lower water levels are needed in the syrup phase at these temperatures and will allow the glaze to flow well and set fast. Our experience shows much better results with these higher application temperatures. Do not allow the temperatures to exceed 150F. Avoid thinning glaze. If it must be done use simple syrup. If your production staff is using simple syrup on a regular basis, this indicates the batch size is too large. Remember, the syrup ratio is critical and constantly adding simple syrup to thin out the glaze is an indicator that the syrup to sugar ratio is changing too much. |
