Meat Quality

Meat quality is defined by the compositional quality (lean to fat ratio) and palatability (appearance, juiciness, tenderness, and flavor) of meat.

The appearance of meat deals with the visual identification of quality meat based on color, marbling, and water holding capacity. The meat should have a normal color that is uniform throughout. In addition, it should have marbling throughout the cut. Marbling can be defined as small streaks of fat dispersed within the meat; it is an indication of tenderness and juiciness as well as flavor. The water holding capacity can be determined by looking in the meat package. If excess water is seen at the bottom of the package, this may be an indication of decreased juiciness and increased risk of drying.

Juiciness depends on the amount of water retained in the cooked meat product. It increases flavor, helps soften meat, and stimulates saliva production in the mouth. Juiciness is determined by water retention and lipid content. Marbling and fat around the edges of the cut of meat also help to keep the water in. Water losses can result from evaporation or dripping. The use of proper cooking methods is another way of increasing meat juiciness.

Tenderness can be attributed to a person's perception of meat such as ease of chewing, softness, etc. Tenderness is a result of the lamb's age and sex as well as the location of the muscle from which the cut of meat was taken. Meat from young lambs will be more tender.

Flavor is another factor in meat quality. Meat flavor can be described as salty, sweet, bitter, etc. Meat flavor can be affected by age, water retention during cooking, and fat within the muscle.

Grading and Evaluation

Lamb and mutton are graded by two USDA grading systems: quality and yield grade. The purpose of these grading systems is to aid in ranking lambs both as live animals and as meat products. These grading systems are useful in pricing as well as marketing.

Quality Grades

This type of grading helps distinguish the predicted palatability of the meat product. Lamb quality grades are prime, choice, good, and utility with prime being the highest, most desirable and choice a close second. A prime grade is characterized by an abundance of marbling while being very juicy and tender. Choice grade meat has less marbling than prime, but is still of high quality and juiciness. Good and Utility grades are seldom sold in stores and are characterized by even less marbling and juiciness. Most market lambs in the United States grade prime. These grades are determined based on flank streaking, conformation (specifically leg conformation), maturity, kind and class, firmness, and finishing. Table 1.1 illustrates how lamb carcasses are quality graded according to flank streaking and age.

Degree of Flank Streaking

Young Lamb

Older Lamb

Abundant

Prime

Prime

Moderately Abundant

Prime

Prime

Slightly Abundant

Prime

Prime

Moderate

Prime

Prime

Modest

Prime

Prime

Slight

Choice

Choice

Trace Amounts

Choice/Good

Good/Utility

Nearly Devoid

Good/ Utility

Utility

Table 1.1

Flank streaking is an indication of marbling, visible intramuscular fat. As can be seen in Table 1.1, flank streaking is considered to be an important meat quality.

The use of kind and class in evaluating meat quality refers to the division of each species into kinds and the kinds then being divided into classes based on gender and maturity. Some species naturally have a better meat quality while younger lambs will naturally be of higher quality meat as well. This is because maturity, the physiological age of the lamb, has a large impact on meat quality. Meat from younger animals can be expected to be more tender than those of older lambs. To determine maturity through carcass characteristics, analyze the bone and cartilage. Young lambs tend to contain more cartilage than older lambs because cartilage turns to bone as the lamb matures. In addition, young lambs will have break joints in their shanks. This is a good indication of maturity. Furthermore, the color of the meat becomes a much darker red as the lamb matures.

Firmness is another factor in quality grading. This refers to the firmness of the flank area or lean cut surface. Carcasses containing a greater amount of fat will be more firm because, when chilled, fat is more firm than muscle. Although this quality does not contribute directly to the palatability, firm retail cuts are more attractive because they hold their shape better. This is also important if the meat will undergo extensive processing.

Conformation refers to the proportionate development of the carcass parts and the ratio of muscle to bone. This is not a factor in palatability, but is important for the shape and attractiveness of retail cuts.

Finishing is the amount, character, and distribution of external, internal, and intramuscular fat. A small amount of fat is desirable to increase tenderness and decrease the risk of the meat drying out, but too much fat decreases the retail cut yield.

Yield Grade

The yield grade determines the quantity of retail cuts that can be expected from a lamb carcass. There are five yield grades ranging from 1-5. The lower the yield grade, the better because a low yield grade indicates that the carcass was most likely exhibiting more pounds of meat as compared to waste. Wastes include fat, bone, and any other unused by-products. The kidney, pelvic, and heart fat must also be removed leaving less than 1% of it in the carcass. To determine the yield grade, the external fat thickness is measured between the 12th and 13th ribs of the lamb's carcass. Adjustments can be made to the fat thickness score by evaluating the amount of fat in the body wall, crotch, udder, sirloin juncture, shoulder, and breast. Also, the leg conformation score is considered with a higher, larger leg score making a lower more desirable yield grade. Superior leg scores are given to those lambs with very wide and thick legs indicating a high lean to bone ratio. Narrow, angular legs will receive a higher leg score due to the lower proportion of edible meat to bone. See Figure 1. An easy way to figure yield grade is by multiplying 10 by the amount of backfat and then adding 4.8. Although ribeye area is not a yield grade factor, ribeye size is important in evaluating the carcass merit of a market lamb. This is measured at the 12th rib using a grid to determine size. Although the consumer is not told the yield grade, it is reflected in the price of the meat because it is an important factor in pricing meat carcasses.

Factors Affecting Meat Quality

There are many factors that can affect meat quality. It is important that producers and packers are aware of these factors in order for maximum lamb quality to be obtained.

Stress as a result of change of environment, rough handling, temperature, humidity, light, sound, and even confinement can decrease meat quality at the time of slaughter. Stress can result in meat that is pale, soft, firm, and dry.

Genetic factors also affect meat quality. It has been determined that color, firmness, and even marbling is inheritable. Furthermore, the sex of the animal affects meat quality due to varying amounts of sex hormones in the blood. Young rams tend to have meat that is darker and tougher than that of whethers or ewes of the same age.

The manner in which the lamb is slaughtered can also have an effect on meat quality. Slaughtering the lamb with stunning renders it unconscious but does not stop the heart. The beating heart helps remove blood from the lamb more quickly. This is important because extra blood in meat is unappealing to consumers. Furthermore, this method reduces the risk of hemorrhages, which cause blood spots in the meat and is also unacceptable to consumers. In addition, the removal of excess blood removes media for microorganisms responsible for meat spoilage.

The diet fed to the lamb is also a factor in meat quality. Consumption of wild onions or garlic may leave an undesirable meat flavor and grazing can result in the accumulation of yellow fat that is badly perceived by consumers.

 

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