Milk & Dairy Products (Lesson 19)
- University of Wisconsin - Madison
- Food Science
- Food Science 120
- Milk & Dairy Products (Lesson 19)
Last Modified: 2011-07-05
Related Textbooks:Food-Medication Interactions
- Milk is an excellent source of calcium and protein.
- Whole Milk (per cup): 146 kcal; 8 g fat; 49% calories from fat; 4% fat.
- Skim milk (fat free)
- 1% milk (low fat)
- 2% milk (reduced fat)
- In the process of homogenization, milk is forced under pressure through fine holes that reduce the size of the fat globules and emulsify the fat globules with protein.
- Most milk is pasteurized at 161F for 15 seconds (HTST) to destroy pathogens and enzymes.
- Sometimes milk is pasteurized at 180F for 3 seconds (UHT).
- Before milk is pasteurized, it is fortified with vitamins A and D.
- Lactose-intolerant individuals do not produce enough lactase.
- Symptoms include bloating, gas, diarrhea, and general intestinal discomfort.
- Lactose (0.2) ---> Glucose (0.7) + Galactose (0.3)
- Lactose ---> Lactic acid + CO2
- In the production of cheese, added bacteria convert lactose to lactic acid.
- As the pH drops, a protein gel forms.
- Chymosin or rennet is added as a coagulant.
- Important chemical changes take place during ripening:
- Lactose ---> Lactic acid
- Fats ---> fatty acids
- Proteins ---> shorter amino acid chains
- Processed cheese can not actually be called cheese, but it is made from cheese.
- It is a blend of aged and green cheeses that are ground, stabilized with emulsifiers, salt, and preservatives, pasteurized, and packed.
- Cream or Milkfat: In the form of whole milk, cream, or butter; comprises 10-20% of the weight of the final product; fat lends flavor and creamy texture to the final product.
- Milk Solids: In the form of nonfat milk powder or condensed skim milk; supply protein and carbohydrate and lend texture to the final product.
- Sugar: Often added as cane or beet sugar or corn syrup solids; sugar adds sweetness and lowers the freezing point of the mix, ensuring that there is some unfrozen water in the final product.
- Emulsifiers: May be lecithin, monoglycerides, or diglycerides; emulsifiers keep fat emulsified in the watery mix and aid in air distribution.
- Stabilizers: Either protein-based (gelatin) or carbohydrate based (guar gum or alginate); Stabilizers add thickness to unfrozen water and prevent large ice crystals from forming.
- Flavoring Agents and Colorants are also added.
- Preparing the mix: Ingredients are blended and the mix is pasteurized at 180F for 15 sec. to destroy bacteria and dissolve powdered ingredients.
- Freezing the mix: The pasteurized mix is chilled and colors/flavors are added. The mix is frozen in a scraped-surface barrel freezer which freezes the water and whips air into the product.
- Hardening the mix: The mix is rapidly frozen at -20F in a blast freezer.
- The hidden ingredient in ice cream is not listed on the label: it's air!
- The amount of air that is introduced into the mix is called over-run.
- Lower quality ice cream has high over-run and is lower in fat.
- Premium ice cream is low in air with low over-run and is higher in fat.
- The air that is whipped into the product is held in place by cold temperature and protein. Ice cream is a protein foam stabilized by cold.
- Remember: ice cream is sold by volume, not by weight.
- Lactose ---> Lactic Acid + CO2
- Added bacteria (controlled fermentation) convert lactose to lactic acid.
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