Frying Fat Technical Help

Overview

Frying fat is the major part of the process environment in which all donuts must perform.  Donuts are the only bakery product which do not use some type of rigid form to set the product.

The frying fats used in the bakery can have different compositions which can cause profound differences in the performance of donuts.  Various compositions of frying fats are used in our industry for reasons such as price, availability, dietary laws and regional preferences.  In addition, fats can change chemically in the frying process. This can increase the variations of frying fat compositions.

There are many good frying fat specifications which are based on field tested products,  but we must remember that no two shops are the same, and it pays to pre-test and select the correct frying fat for your operation and the field conditions.

Bakers will have many questions on frying fats and it is wise that they not only talk to the shortening manufacturers, but also, the mix manufacturers.

 

Composition
Fats are compounds of glycerine and fatty acids.  The various fats differ in the type of fatty acids in their composition:

Examples:
Saturated fatty acids, such as stearic and palmitic, when bound to glycerine, form the hard fats.  Unsaturated fatty acids such as oleic, linoleic and linolenic, when bound to glycerince form liquid fats or oils.

 

Function

Frying fat serves as a heat transfer medium, as well as being absorbed into the donut to improve the eating quality and shelf life.  Fat contributes to the flavor of the product and causes the sugar coating to adhere to the donut.

Frying fat is one of the more costly ingredients in a finished donut.  When frying fat breaks down with use, the product quality not only suffers, but the cost of the donuts goes up due to the increase in the amount of fat absorbed by the donuts.

 

Fat Breakdown

The following are some of the general indicators of fat breakdown:
                    Darkening of the fat
                    Development of off flavors
                    Smoking of the fat
                    Foaming on the fat surface
                    Gum formation on exposed metal parts of the fryer


Some of the Chemical changes of the frying fat due to  breakdown:
          Density                        Increases
          Viscosity                      Increases
          Titratable Acidity        Increases
          Melt Point                    Decreases
          Flash Point                  Decreases
          Solid fat index SFFI      Decreases
          Congeal Point              Decreases
          Iodine Value                  Decreases
          Crystallization Rate      Decreases
          Cloud Point                  Decreases

Free Fatty Acids
Fat breakdown at normal frying temperatures is caused by hydrolysis of the fat at the point where the fatty acid connects to the glycerol. The addition of a water molecule at this point will release a fatty acid. The result is a free fatty acid (FFA)and a diglyceride. The normal frying process releases steam which will cause this reaction to occur. In addition oxidation (from air or air jets blowing into the fat) can cause an increase in the FFA.

A small amount of FFA in the donut frying fat is desirable. Fats with a FFA of over 0.1% will just begin to smoke. FFA must be present in the donut shortening to obtain a quality product. FFA in the fryer should be between 0.3% and 0.75%. Donut shortening that is too fresh or not broken in will have too low a FFA content. The FFA content increases as the donuts are fried and the addition of fresh shortening will lower the FFA. It is a balance between these two that maintains the FFA level.

Donuts fried in fresh fat will be light in color and will have a low fat absorbtion, ragged break.

Donuts fried in a fat with too high a FFA will be dark and will have high fat absorbtion. Poorly shaped donuts and can have off flavors.

Free Fatty Acid Testing

Beakers and bottles
E 07211-20 2 oz ss ladel 1 x $9.50
E-06004-13 250 ml PTFE beaker 12 each    1 x $28.40
E-06088-15 250ml drop bottle ld polyethylene 4pk 1 x $15.79
E-07879-20 15ml self zero self supporting burette 1 x $122.40

Chemicals
00039PD 0.1N Sodium Hydroxide 1 liter size  6 x $9.95
00016MU Ethyl Alcohol 90% denatured 6 liter  1 x $112.50
00034SI Phenolphthalein    1 x $9.50
hotplate stirrer
E04765-14  1" starburst stir rod    2 x $6.75
E84303-00 120v hot plate stirrer    1 x $275.00
____________________________________________________________________
Total  $646.29

Cole Parmer 800-323-4340
625 East Bunker Ct
Vernon Hills, Illinois, 60061-1844

Prep
1.  Fill drop bottle with Phenolphthalein and label
2.   Fill burette bottle with .1N Sodium Hydroxide

Sampling
1.  Use SS ladel to remove fat from fryer and place in PTFE Beaker

Testing
1. Wear Eye protection
2. Weigh 50 g of fat into clean PTFE beaker.  Record Weight
3. Add approximately 100ml of ethyl alcohol to fat. 
4. Add 5 drops of phenolphthalein to fat/alcohol.
5. Put stir bar into beaker
6. Place beaker on hot plate and heat on med low  heat.  PTFE Beaker will melt above 500F.  Heat until alcohol boils.
7. Add sodium hydroxide to burette so that it reads zero (0)
8. Turn on stirrer
9. Slowly drip sodium hydroxide into boiling solution until the color changes and stays light pink.  Record ml of sodium hydroxide added.  Do not add too fast or you could go past endpoint

FFA=  ml of sodium hydroxide*.1*28.2
                         Grams of Fat

 

Types of Frying Fat

There are several sources of stock materials for frying fats.

Animal Fats
Beef Tallow and Lard

Vegetable
Soy Oil, Cottonseed Oil, Palm and Coconut Oils are the most common.  Corn, peanut, Safflower, sunflower and Canola are not as common due to flavor, cost and functionality issues.

Animal fats have been used for years in the baking business.  Animal fats have been phased out of most  bakeries for health and religious reasons.  The majority of bakeries on the east and west coasts need to be Kosher certified for the large Jewish populations found there.  There are several other groups such as vegetarians and Muslims who look for the kosher label to indicated the absence of these fats as well.  Animal fats are still used on a limited basis in the central United States.  Animal fats will impart a distinct flavor and are usually more cost effective.  Animal fats can impart a very strong flavor on shelf life that can be of concern.

Compound shortenings are combinations of animal and vegetable fats.  The ratios and type vary with manufacture and the market.

Vegetable Fats are the most popular with soy oil being by far the most predominate fat.  Soybean oil is partially hydrogenated to increase the melt point.  Very often a second fat such as cotton seed is added.  The use of palm and coconut oils being used as the second fat is not as common.


 

Stabilization of fats

Hydrogenation is the addition of hydrogen to the fatty acids at the points of unsaturation  as well as the addition of antioxidants and other chemicals can help eliminate some of the oxidative reaction.  These steps slow down the rate of oxidation but do not eliminate it.


 

Trans Fatty Acids

Trans fatty acids occur naturally in beef, butter, milk and lamb fats and in commercially prepared, partially hydrogenated margarines and solid cooking fats. Partially hydrogenated vegetable oils were developed in part to help displace highly saturated animal and vegetable fats used in frying, baking and spreads. Their use in margarines probably provides a more healthful alternative to butter, beef tallow and lard because they have less saturates. The main sources of trans fatty acids in the American diet today are stick margarine, shortening, commercial frying fats and high-fat baked goods.

Some clinical studies show that at high levels of intake, trans fatty acids may raise food levels of LDL cholesterol, the so-called "bad" cholesterol, much like saturated fatty acids do, only less markedly. In addition, some studies have shown that trans fatty acids, again at high levels of intake, modestly lower HDL levels, the "good" cholesterol. However, at levels of intake typical in the American diet, trans fatty acids may not reduce HDL cholesterol.
New developments in fat substitutes coupled with Americans' demand for low-fat and fat-free foods and a gradually diminishing consumption of all fats will likely keep overall consumption of trans fatty acids in the current range, if not reduce intake. Therefore, current dietary advice to reduce consumption of saturated fatty acids far outweighs any cause for alarm about trans fatty acids in foods.

Trans fatty acids are produced during the hydrogenation of vegetable oils, a process that adds hydrogen to unsaturated fatty acids in vegetable oil and changes the fat from a liquid to a soft or solid state. Partially hydrogenated vegetable oils can replace naturally solid, saturate-rich fats, such as lard and beef tallow, in margarines and baked foods, as well as commercial frying, where vegetable oils cannot be used. Margarines in the U.S. contain anywhere from 0-30% trans fatty acids; stick margarines contain more trans fatty acids that soft tub margarines and spreads.

Much of the research that has negative results for trans fat were financed by the Palm Oil board. Palm oil and coconut oils (tropical oils that were the "bad" rage of the 80's) are naturally low in trans fatty acids, but are very high in saturated fats. Current trends of 2006 indicate a return of palm and coconut oils to replace hydrogenation. The end result will be more consumer confusion and no net improvement in the diets.

The USDA did a study http://www.ars.usda.gov/is/AR/archive/sep98/spred0998.htm in which they compared diets high in saturated fats (actually Butter), to diets high in trans fats (hydrogenated margarine) as well as a diet high in poly unsaturated fats (specially made margarine).

A direct quotation from the result "There's only one conclusion that can be reached," says Judd. "You limit trans fats in the diet where you can. But don't get overly concerned to the point where you substitute saturated fats for trans fats. Saturated fats average about 12 percent of the total calories in the diet and are a major dietary factor in cardiovascular disease risk. "

The only choices for frying donuts at this point are:

1. Partially hydrogenated Vegetable oil ( contains trans fat)

2. Animal Fats (contain some trans fat)

3. Vegetable oils containing  Palm oil, palm kernel oil and/or coconut oils.

Esterified oils are NOT a good choice for donut frying at this time.  The off flavors are far too objectionable.  I feel they have a rancid fish like flavor.  Not a good choice for a sweet donut.  Maybe in the future the shortening companies can correct this.

As you can see, none of the choices are healthy. 

Season Specifications of fats

Most large producers of frying fats offer seasonal changes in frying fats (summer and winter blends).  The summer formula will be slight ly harder and will have a higher SFI in the 92 to 104 range which will cause it to set faster in the hot conditions of a bakery.


 

AOM Stablity

The AOM (Active Oxygen Method) is an accelerated rancidity test. This test is to determine ho w well the fat will hold up to oxidation (off flavors) on shelf life. The fat is held at 208F while air is bubble through at a constant rate. The AOM number is the number of hours required to develop a peroxide value of 100.

Usually an AOM stablity of 100 hours is desired for donut shortening. There are fats with much higher AOM stablities but most bakers do not use them due to cost. Lower AOM stablity fats should be avoided as they will produce product that goes rancid too fast.

Peroxide Value

This is a measure of the amount of oxidation the fat has already undergone. Oxygen can react at the points of unsaturation creating peroxides. During the initial stages of oxidation, the peroxides formed are relatively stable. As the fat oxidizes more the peroxides become more reacive. This is a measure of how rancid a fat is.

This peroxides will liberated lodine from potassium iodide in glacial acetic acid. A maximum of 1.0 milli-equivalent per kg is recommended for fresh frying fats. Rancid fats will have peroxide values in the range of 50 to 100. A high initial peroxide value means that the fat was already abused.

Solid Fat Index