Frozen Dairy Desserts

Ice Cream

Periods: Three lab periods + one extra session

Period 1: Planning, and mix formulation 
Period 2: Mix preparation
Extra: Freezing and hardening
Period 3: Product evaluation

Objectives:

a. To familiarize the students with the principles of preparation and processing of mix for frozen dairy desserts.

b. To acquaint the students with the freezing and hardening of frozen dairy desserts and the effect of selected variables on processing and product quality.

c. To develop an appreciation for the various factors that the processing must consider in the manufacture of a frozen dessert, using ice cream, sherbet or frozen yogurt as a model.

Introduction:

Frozen dairy desserts include a variety of products, such as ice cream, ice milk, and sherbet, each of which may come in a number of different flavors. The composition of frozen dairy desserts is governed by state and federal regulations. These specify the types of ingredients and the minimum and maximum quantities of each that may be used. This project deals with the preparation and freezing of ice cream of specified composition. For information concerning the types of frozen desserts and factors that affect their characteristics, see the frozen desserts information page on the web site.

Procedure:

Ice cream is the most widely consumed frozen dessert product.  The group, in consultation with the instructor shall determine the type of ice cream or other frozen dessert to manufacture and the method of mix preparation and freezing. The group should determine what three variables either in formulation or processing that they think will alter the characteristics of the ice cream

A. Formulation and Processing of Mix

Ingredients

The ingredients in ice cream include a source of milk fat, a source of milk solids, sweetener, stabilizer and emulsifier. A typical combination of ingredients might include:
Cream
Non-fat Dry Milk (97% TSS)
Milk
Sucrose
Corn Syrup Solids
Stabilizer-Emulsifier Blend

Mix Formula:

To be determined by group in consultation with instructors.

Mix preparation:

[The amount of mix to be prepared will depend on the freezer utilized and the variables to be used in the manufacture of the ice cream]
    1. Manually blend the NFDM into the milk portion of the mix while it is still in the 10 gallon can. (the agitator in the tank is not fast enough to provide for adequate mixing.)
    2. Blend sugar and stabilizer together in a dry container.
    3. Pour the liquid ingredients into the processing tank and warm to 80 to 90oF.
    4. When the milk and cream have reached 80° F, add the dry ingredients and blend slowly.
    5. Increase the mix temperature to 120° F to for-warm the mix and permit the dry ingredients to solubilize.
    6. Start the HTST on water. Adjust the HTST temperature to at least 175° F and adjust the homogenization pressure.
    7. Transfer the mix to the HTST balance tank when the water level is at the balance tank outlet.
    8. Time four minutes and forty five seconds before putting outlet tube in a clean, sanitized stainless steel can. (there will be some product loss due to product/water mixing).
    9. As the last of the mix settles in the balance tank outlet, add cold water.
    10. Time two minutes and thirty seconds before withdrawing product tube from can. (Again, there will be product loss due to water/product mixing).
    11. Cool the mix to 40° F or below, and store (not less than 24 hours of storage) until the group can meet again for freezing (make arrangements with pilot plant manager and instructor).
    12. Take a representative sample of the mix for analysis and store under refrigeration.
    13. Determine the viscosity of the freshly prepared mix using an appropriate method, such as using a Brookfield viscometer.
    14. Clean all equipment and the laboratory area.

B. Freezing and Hardening of Ice Cream

  1. Repeat the viscosity measurement on the mix before freezing.
  2. A counter batch freezer will be used for freezing of ice cream. The instructor will provide supervision. Three batches of mix of approximately two gallons each will be frozen. See overrun graph on web page to determine the amount of mix to use to achieve the desired overrun.
  1. Assemble the freezer and sanitize
  2. Add flavoring to the total mix according to label directions.
  3. Determine the unit weight of the mix and record for overrun calculations. (Use overrun cup as demonstrated by instructor).
  4. Freeze the mix to achieve the desired overrun and draw temperature.
  5. Record drawing temperature
  6. Measure overrun.
  7. Place ice cream in a suitable container and place in hardening room.
  8. Clean the utensils, freezer, and laboratory area according to instructions provided.

C. Evaluation:

1.  Evaluate mix viscosity as determined in the planning session

2. Set up a sensory panel of students to evaluate the texture and flavor of the frozen dessert.

3. Determine melt-down of ice cream (how fast it melts).

4. Evaluate for coliform organisms, using Petrifilm sheets as supplied 

 

 

 

 

References:

Buchheim, W. 1998. Ice Cream: Proceedings of the International Symposium held in Athens, Greece 18-19 September, 1997. International Dairy Federation, Belgium

Marshall, R. T. & Arbuckle, W. S. 1996. Ice Cream. Chapman and Hall NY