Question

1. Discuss how chemical changes in the iron molecule in myoglobin can alter the color of meat and what colors are produced. (5 pts) 2. Discuss the various roles that pH plays in overall meat quality this includes how it changes under various conditions. (8 pts) 3. Chose a specific food product and discuss all of the various types of packaging you will need to employ to bring that product from the food plant in which it is produced to the consumer for end use of the product. Please include if you have a choice of packaging material at various points why you choose one material over another. An example of this would be one type of film over another. Beyond maintaining product integrity from production to consumer, discuss any other items that may enter into your choice of packaging. (22 points)

Answer 1

1. On exposure to oxygen the purple ferrous haem pigment, myoglobin, forms the bright red covalent complex, oxymyoglobin. In fresh meat oxidation of oxymyoglobin to metmyoglobin, the unattractive brown pigment, is affected principally by the reducing capacity of the muscle, oxygen availability and temperature. In frozen meat, light is the major factor affecting the oxidation rate. Oxidation of nitric oxide myoglobin, the ferrous pigment in cured meats, is prevented by excluding oxygen but proceeds rapidly in light, if oxygen is present.

Stress, pre-slaughter handling of the animal and post-slaughter treatment of the carcass affect the light scattering properties of the meat. Glycogen depletion in the live animal results in translucent, dark firm and dry (DFD) meat with high pH and high oxygen uptake. Rapid post-mortem glycolysis causes structural changes in muscle which becomes opaque, pale soft and exudative (PSE). Electrical stimulation of the carcass and the rate of chilling also affect light scattering of meat. On storage, increase in light scatter is accompanied by a decrease in colour stability.

Color is used by consumers to determine if meat is fresh and safe to eat. It is the single most important driving factor in a consumer’s decision to purchase meat. Myoglobin is the heme iron containing protein that gives meat its color, and it is a great source of dietary iron. Myoglobin stores oxygen in muscle cells and is similar to hemoglobin that stores oxygen in blood cells.

The more myoglobin content meat contains the darker red it will appear in color. Myoglobin content is higher in beef and lower in poultry with lamb and pork having intermediate amounts. The age of an animal will also impact the myoglobin content of the muscles with older animals having more myoglobin and darker meat. Muscles that are used for movement also have more myoglobin content than muscles used for support. Along with water from muscle, myoglobin is what is found in meat packages that leaks out of the muscles during storage and most people think is blood. Almost all of blood is removed from muscle at the time of slaughter.

Myoglobin has three natural colors depending on its exposure to oxygen and the chemical state of the iron. If no oxygen is present, the meat appears purple red, like in vacuum packaged meat, and is in the deoxymyoglobin state. Meat is bright red when exposed to air and is typical of meat in retail display. Bright red color indicates oxymyoglobin is present. Meat appears tan or brown when only very small amounts of oxygen are present such as when two bright red pieces of meat are stacked on each other excluding the oxygen. Meat can also appear brown when the meats color life is exhausted late in display when the iron in the pigment becomes oxidized. Metmyoglobin is the state when the iron has oxidized and is tan or brown in color.

Although brownish-red colored meat can indicate spoilage, it doesn’t always mean that meat is spoiled

2.  The pH of muscle/meat is a measurement of acidity. In a normal living muscle the pH is approximately 7.2. Glycogen is broken down to lactic acid when muscle turns into meat. The pH of meat can range from 5.2 to 7.0. The highest quality products tend to fall in the pH range of 5.7 to 6.0. Both the rate and extent of post-mortem pH fall will influence pork quality characteristics. Pale, Soft, and Exudative (PSE) pork commonly results from a rapid breakdown of glycogen into lactic acid after slaughter.

The ultimate pH is determined by the extent of the pH decline at 24 hours after slaughter. The variation in ultimate pH influences factors such as colour and the ability of the meat to retain water. A low ultimate pH results in meat proteins having decreased water-holding capacity and a lighter colour. Conversely, a higher ultimate pH will give a darker colour and less drip loss.

A low ultimate pH results in meat proteins having decreased water-holding capacity and a lighter colour. Conversely, a higher ultimate pH will give a darker colour and less drip loss. ... Ultimate pH also impacts eating quality characteristics such as juiciness, tenderness, and taste.

3. To protect products and materials during transport, distribution and storage, a variety of packaging types is available. In warehouse and manufacturing applications, packaging includes containers, protective dunnage, unitizing materials that hold several items together to form a complete load, and pallets that provide a stable platform for transport. All of these packaging components come in varying sizes, shapes and materials, depending on the items or products they are protecting. Typical applications include holding and protecting bulk materials, cases, loads or individual items for shipping and receiving, organizing products in static or automated storage systems, and acting as a receptacle to hold picked items for a discrete order.

Product packaging in the food industry is unique because it must allow the contents inside to stay fresh and safe for consumption, even after long hours of shipment and distribution. Because of this, certain products will require specific types of packaging materials that protect them against temperature, manhandling, etc. Frozen food, dry grocery items, and perishables each need a different type of packaging to maintain freshness. It is also important to choose a packaging material that will withstand contamination.