University of Nebraska Cooperative Extension MP 76-A

Summary

Twenty-seven and 12 muscles, respectively, from the chuck and round were analyzed for objective color, expressible moisture, emulsion capacity, pH, total collagen content total heme-iron content, and proximate composition. Observations of these physical and chemical properties showed a vast range of results. The range in data reveal the variation within and among muscles. Knowledge of this variation can lead to proper usage, thereby increasing value of the beef chuck and round. Quality grade had the most pronounced effects, whereas yield grade and weight showed fewer effects on these traits across all 39 muscles.

Introduction

With the increasing popularity of value-added products and the decline in value of the beef chuck and round (20 - 25% over a five-year period), it s necessary to characterize the muscles from these two primals. Muscle has unique physical and chemical properties, which when known and understood can allow for development of valueadded products. Information (physical and chemical properties) of many muscles within the chuck and round was lacking until this study was undertaken. It is also important to describe the effects of quality grade, yield grade, and weight of carcass on these properties. Therefore, the objectives of this study were to determine the physical and chemical properties of 39 muscles from the beef chuck and round and the effects of quality grade, yield grade, and weight on these properties.

Procedure

Ninety-four chucks and 94 rounds were selected at the IBP Inc., Dakota City, Neb. plant based on quality grade (upper 2/3 Choice, low Choice, and Select), yield grade (1, 2, 3, and 4 and 5 together), and carcass weight (550 - 650 lb and 850 - 950 lb). Twenty-seven and 12 muscles, respectively, were dissected from chucks and rounds. Each individual muscle was then trimmed of all external fat and connective tissue. Objective color (L*, a*, and b* values) was observed using a Hunter Lab Mini Scan device with a 1- inch port. Expressible moisture, a method of measuring water holding capacity, was measured as the percentage of moisture lost due to centrifugation. Muscle pH was determined using a pH meter with a spear tip combination electrode. Emulsion capacity, which determines the amount of oil a specific muscle/protein system can bind, was expressed as mL oil bound/2.5g of lean tissue. Total collagen measures the amount of connective tissue within a given muscle. It was quantified by measuring the total content of hydroxyproline in a sample, which is related to collagen. Total collagen was expressed as mg of collagen/g of lean tissue. Total heme-iron measures the amount of myoglobin and hemoglobin within a given muscle. Acetone and hydrochloric acid were used to separate myoglobin and hemoglobin from the sample. This solution then was read using a spectrophotometer; results were expressed in parts per million (ppm). Proximate composition (fat, moisture and ash) was determined using Soxhlet ether extraction procedures and a LECO Thermogravimetric Analyzer (a continuous weighing and heating device). Fat, moisture and ash were expressed as mg/g (%) of lean tissue. Data were analyzed statistically using mixed and least square means procedures.

Results

Across all 39 muscles, variation was evident in all analyzed physical and chemical properties (Tables 1, 2, 3, 4). Objective color (L*, a*, and b*) values represent a color scale. The higher the L* (ranging from 0 = black to 100 = white), the lighter the muscle. As a* (ranging from negative 60 = green to positive 60 = red) increases, the muscle becomes more red. As b* (ranging from negative 60 = blue to positive 60 = yellow) increases, the muscle becomes more yellow. The overall means and standard deviations observed for L*, a*, and b* were 41.06 ± 4.55, 29.57 ± 4.05, and 22.78 ± 4.32, respectively. The measurement of objective color can be correlated to other chemical properties such as pH and total heme-iron, which together can be related to the shelf-life of a specific muscle and the ultimate color of a processed product.

The mean and standard deviation for expressible moisture was observed to be 37.50 ± 5.15%. Expressible moisture (along with pH) can reveal a good understanding of protein functionality. Knowledge of the amount of moisture lost due to centrifugation allows product developers to use technologies to minimize the loss of moisture (loss of yield and palatability).

The mean and standard deviation of pH was observed to be 5.78 ± 0.32. Muscle pH as previously mentioned reveals a better understanding of protein functionality. As muscle pH increases, expressible moisture decreases. However, higher pH meat appears to be darker in color (lower L* values) and also tends to have a shorter shelf-life.

The mean and standard deviation for emulsion capacity were observed to be 174.2 ± 18.8 mL oil bound/2.5 g of lean tissue. This property of muscle can also characterize a specific muscle, as higher amounts of oil bound in a protein system can be related to the amount of saltsoluble protein (major binding protein) within that system. Such information can allow for increased yield and therefore increased profit in the production of sausage-type products.

The mean and standard deviation of total collagen was 11.69 ± 6.54 mg/g of lean tissue. This property of muscle can be related to the tenderness and texture of meat.

The mean and standard deviation for total heme-iron was 20.78 ± 4.43 ppm. Total heme-iron can reveal information about a muscle s physical appearance (appearance to the eye), which is a major factor in consumer acceptance. The concentration of these color pigments is also an important determinant of processed meat color.

Fat, moisture and ash had mean percentages and standard deviations of 6.86 ± 3.45, 72.28 ± 2.83, and 1.26 ± 0.28, respectively.

To envision the variation between these 39 muscles, each muscle was categorized for each trait into three groups desirable (white), intermediate (gray), or undesirable (black). These charts (Tables 5 and 6) show specific physical and chemical properties (fat, pH, expressible moisture, emulsion capacity, total heme-iron, and total collagen) which provide a quick, overall picture of a particular muscles characteristics. This can be useful in selection of candidate muscles for value-added products.

Through investigation of the effects of quality grade, yield grade and weight on the physical and chemical properties, quality grade was the effect that was most frequently significant (P < .05). Across all physical and chemical properties, 2 to 31, 1 to 9, and 0 to 8 muscles out of 39 showed an effect due to quality grade, yield grade, and weight, respectively. For muscles with a significant quality grade effect, moisture (19 of 23 muscles) and ash (6 of 15 muscles) decreased while fat (26 of 31 muscles) and pH (7 of 16 muscles) increased with an increase in quality grade. It was also observed that properties showing an increase with an increase in quality grade were fat (26 out of 31 muscles) and pH (7 out of 16 muscles).

Significant (P < .05) yield grade effects were seldom linear, reflecting inconsistent trends as yield grade increased or decreased.

Moisture (4 out of 5 muscles), L* value (7 out of 7 muscles), a* value (8 out of 8 muscles), b* value (6 out of 6 muscles), and expressible moisture (5 out of 6 muscles) increased with an increase in weight of carcass. However, pH (4 out of 4 muscles), fat (4 out of 5 muscles), and emulsion capacity (5 out 5 muscles) decreased with an increase in weight of carcass. Total collagen showed no effect across all 39 muscles due to weight.

These data indicate a vast amount of variation in physical and chemical properties among muscles of the beef chuck and round. Knowledge of these properties now allows individual muscles to be identified and utilized for production of value-added products.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Elbert C. Dickey, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources.

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