Unit

1. Unit Food Science

2. Problem Area Processing Animal Products

3. Lesson The Science of Curing Meats

4. Student Learning Objectives • 1. Explain the effects of salt and nitrites on meat products. • 2. Explain why curing increases the shelf life and palatability of meat products. • 3. Distinguish between cured and fresh meat products and describe the effects of temperature on meat curing.

5. Terms • Curing • Dry Curing • Fibrils • Myofibrillar Protein • Myoglobin • Nitrites • Osmosis • Oxidation

6. What are the effects of salt and nitrites on meat products? • Salt (sodium chloride) and nitrates are commonly used substances in the curing and preservation of meat products. • A. The term curingrefers to any method of preserving meat by salting, smoking, and the like. Salt in the curing mixture provides flavor, preserves the meat product (by reducing meat moisture), and extracts myofibrillar proteins. Myofibrillar proteinsare proteins that contain fibrils in the muscle cells that are capable of contracting. Fibrilsare small, thread-like fibers in muscle. They are the structural unit of striated muscle.

7. B. Nitrates or nitrites promote color development, flavor, and preservation by inhibition of microorganism growth and prevention of fat oxidation. Oxidationis the addition of oxygen to a compound. Oxidation is always accompanied by a reduction. As fat is oxidized in the meat, the meat will have a rancid flavor. • C. Cured meat often has a traditional reddish color. The color of the meat depends on the amount of muscle pigment, or myoglobin, contained in the muscle tissue. Myoglobinis a hemoglobin-like, iron-containing protein pigment found in muscle fibers. The compounds resulting from the use of sodium nitrite (NaNO2) react with the myoglobin to change the color of meat from grayish-pink to a bright pink.

8. D. The use of sodium or potassium nitrates or nitrites(salts or esters of nitrous acid (HNO2) is still permitted in meat and poultry products. However, the safety of these products continues to be investigated, and nitrates are generally no longer used.

9. Why does curing increase the shelf life and palatability of meat products? • Curing increases the shelf life and palatability of meat products by interfering with processes that would normally degrade the quality of the meat. • A. One method of meat curing is known as dry curing. Dry curingis a process of rubbing the curing mixture on the surface of the meat, and then curing occurs as the ingredients are dissolved into the meat by the natural moisture of the meat. This mixture then permeates throughout the meat by osmosis, or the diffusion of a substance from a high to low concentration through a semi-permeable membrane.

10. B. Common ingredients in a pickling (curing) solution are salt, nitrite, phosphates, sodium erythorbate, sugar, and starch. This solution is pumped into the meat muscle using small diameter needles. Erythorbate stabilizes color, reduces fat oxidation, and inhibits undesirable nitrite reactions. • Phosphates improve color development, inhibit fat oxidation, and promote myofibrillar protein extraction, which improves tenderness. Sugars and seasonings are primarily used for improving taste, although dissolved sugar molecules also reduce the activity of water and growth of microorganisms.

11. C. The smoking of meat is an ancient practice to preserve meat products and enhance flavor and color. However, today refrigeration has replaced smoke as a preservative. Wood smoke contains compounds, including acids, phenols, and carbonyls, that are major contributors to smoke flavor and color, respectively. • The acidic compounds in smoke accelerate curing and contribute to the pink color of the cured meat. Smoke also has a bacteriostatic effect on meat products and a drying effect that inhibits bacterial growth.

12. How can we distinguish between cured and fresh meat products and what effect does temperature have on meat curing? • Fresh and cured meats can easily be distinguished due to the color of the meat after the cooking process. • A. All fresh meat is red in color when an animal is first butchered. As fresh meat is stored, oxygen in the meat is used up as fat oxidizes, and the meat begins to turn brown. In cured meat, sodium nitrite compounds cause the myoglobin to be converted into nitric oxide myoglobin. Heat will then convert the nitric oxide myoglobin to nitrosyl hemochrome, a more stable pigment in cured meat that provides a bright pink color.

13. B. Very small amounts of nitrite (20–30 ppm) are needed to produce this pink color in cured meat. When meat is cooked without the addition of sodium nitrite, the myoglobin becomes denatured and the meat turns brown. This is why fresh ground beef turns brown when cooked, while a piece of smoked ham will appear pink after cooking.

16. Review/Summary • What are the effects of salt and nitrites on meat products? • Why does curing increase the shelf life and palatability of meat products? • How can we distinguish between cured and fresh meat products and what effect does temperature have on meat curing?