Introducing an Angle Adjustable Cutting Box for Analyzing Slice Shear Force in Meat

Summary

Slice shear force is a reference method for beef texture analysis. Using an angle adjustable cutting box could increase its accuracy for research purposes. The results from different locations within the longissimus muscle show a high correlation with Warner-Bratzler shear force methodology and high potential adaptability for different muscles.

Abstract

Research indicates the fibre angle of the longissimus muscle can vary, depending upon location within a steak and throughout the muscle. Instead of using the original fixed 45 ° or 90 ° cutting angle for testing shear force, a variable angle cutting box can be adjusted so the angles of the knives correspond to the fibre angle of each sample. Within 2 min after cooking to an internal temperature of 71 °C on an open-hearth grill set at 210 °C, a 1 cm by 5 cm core is cut from the steak, parallel to muscle fibre direction, using 2 knife blades set 1 cm apart. This warm core is then subjected to the Slice Shear Force protocol (SSF) to evaluate meat texture. The use of the variable angle cutting box and the SSF protocol provides an accurate representation of the maximal shear force, as the slice and muscle fibres are consistently parallel. Therefore, the variable angle cutting box, in conjunction with the SSF protocol, can be used as a high-throughput technique to accurately evaluate meat tenderness in different locations of the longissimus muscle and, potentially, in other muscles.

Introduction

Tenderness is one of the most important quality attributes in meat¹. Inconsistency in beef tenderness has been identified as one of the major problems facing the beef industry². The Warner-Bratzler shear force (WBSF) test, characterized by a triangular hole in a precisely machined shear plate, is the most widespread method used to indicate meat sensory tenderness^3,4, as it is the instrumental method that arguably has shown the best correlation with sensory panel scores for meat toughness⁵. However, the slice shear force protocol (SSF) has become an important technique for analyzing muscle texture and tenderness⁶, as an alternative to the standard WBSF protocol⁷. It is beneficial in instances where rapid analysis or a high number of samples need to be processed. For the SSF, only one core is taken from the steak when it is still warm, versus the multiple cores (3-6) taken from the steak usually after 24 hr of refrigeration for the WBSF⁶. From this one slice, the SSF analyzes the average texture of the whole steak⁸, as it has been found that tenderness varies between the lateral to medial sides of the steak⁹, with the center and middle of steaks having the best representation for average WBSF. The downfall to the SSF is that, within a steak, from the lateral to medial sides, there is variation in the shear force values⁹; however, by consistently using the sizing box to make 5 cm sections, it may reduce variability that could come from using different sections of the steak. However, since some steaks are different sizes, a 5 cm slice may occur in different locations on the steak, which could then affect shear force values¹⁰.

On the other hand, the original cutting box designed to obtain the section to be analyzed in the SSF protocol allows only 2 fixed angles, 45 ° and 90 °; however, muscle fibre orientation changes within steaks, and within the muscle¹¹. Shackelford and Wheeler¹² stated that the average longissimus angle was 43.8 °, which was close to 45 ° and therefore deemed appropriate when samples were always collected from the same location. However, Derington et al.¹¹ reported a range in the angle of the fibres along the longissimus muscle between 33.1 ° and 53.9 °. Thus, when, for research purposes, several steaks from the same animal need to be analyzed, assigning all fibre angles to either 45 ° or 90 ° potentially reduces accuracy. The use of a variable angle cutting box may provide a more accurate depiction of maximal shear force, as having the capacity to measure and adjust the cutting angle allows for the slice to consistently run parallel with the muscle fibres.

Protocol

1. Steak Collection

1. Following grading at 24 hr - 48 hr post slaughter, the longissimus muscle (either the thoracic and/or lumborum end) is removed from beef carcasses and collected for quality analysis.
2. The muscle is trimmed of subcutaneous fat and squared off. The muscle is then cut into 2.5 cm (1 in) steaks following safety and food handling protocols. Following the cutting of individual steaks, appropriate labels (animal number, side, muscle location, or time) are placed on the respective steak.
3. Steaks are then prepared for storage. If they are to remain fresh, they are placed on a tray and taken to the grill. If the fresh steaks cannot be cooked immediately, they need to be covered with plastic until cooking can begin, to prevent dehydration. If steaks are to be aged in a cooler, or frozen, the weight is recorded to two decimal places before being placed in an oxygen impermeable vacuum-package bag and sealed using a vacuum packaging machine. Steaks are then placed in their respective long term storage locations.

2. Cooking Procedure

1. If the sample has been frozen, remove from the freezer and place in a 4 °C cooler to thaw overnight.
2. On the day of cooking, pre-heat an open-hearth grill to 210 °C for sample cooking, and prepare the temperature logger system and computer by inserting the thermocouples into the outlets of the scanning device. Lightly grease the grill with vegetable shortening approximately 10 min before cooking begins.
3. Before beginning to cook, remove steaks from the cooler. Remove the sample from its package and blot excess moisture from the steak with paper towel. Record the raw weight of the steak to two decimal places.
4. Insert a thermocouple into the midpoint of the steak along its longitudinal axis. Start the thermocouple scan to record cooking data.
5. Place the steaks on the grill, keeping the thermocouple parallel to the flat cooking surface of the steak and the grill. If the probe is not kept parallel, it can result in improper temperature readings.
6. Cook steaks to an internal temperature of 35.5 °C, then flip the sample over and continue cooking to a final internal temperature of 71 °C. Once the internal temperature is 71 °C, remove the sample from the grill and pull the thermocouple out of the steak.
7. If a cooking weight is desired, allow the steak to cool slightly (1-2 min), then blot the sample with a paper towel to remove excess moisture and weigh sample to two decimal places.
8. If cooking data are required, save the thermocouple scan data.

3. Angle Adjusting and Sample Preparation

1. While the sample is still warm from the grill, make a cut 1 - 2 cm from the lateral end of the steak to create a square end.
2. A 5 cm section across the width of the steak is prepared by using a 'sample sizing box' with a knife notch at 5 cm, parallel to the original cut.
3. The orientation of the muscle fibre angle can be measured by placing a protractor on the knife-cut surface of the steak.
4. The variable angle cutting box is then set to the corresponding angle of the sample by sliding the lower metal plate customized with the bottom holes for guiding the double bladed knife. Tighten the knobs to secure the lower metal plate at the corresponding angle.
5. Place the 5 cm section of the steak into the cutting area of the variable angle cutting box so that the muscle fibre direction is parallel to the angle of the double bladed knife.
6. The double bladed knife is used to cut a 1 cm slice across the previously cut 5 cm piece, so ensure that the knife will pass through the whole sample at the corresponding angle. When placing the steak, ensure that it is touching the edge of the cutting area closest to the user, as the cutting motion will pull the steak towards the user.
7. To cut, insert the double bladed knife into the cutting box and pull the knife to cut the meat into a 1 cm strip. To prevent tearing of the meat, use a slight sawing motion while pulling the knife towards the user. Keep the knife blades against one edge of the guide plate to maintain equal cutting proportions.
8. The result should be a warm, 1 cm thick slice that is 5 cm long, with the fibres consistently running parallel to the slice. This slice is then used for slice shear force analysis of texture in meat.

4. Shear Force Analysis

1. To determine shear force analysis, the slice shear force protocol (SSF) uses the 1 cm by 5 cm slice obtained with the variable angle cutting box. Using a texture analyzer machine with a flat shear slice blade, the analysis is performed on the warm slice.
2. Prepare the Texture Analyzer with a 50 kg load cell and set the shear distance to 48 mm, with a cross head speed of 500 mm/min.
3. The shear is performed once, perpendicular to the muscle fibres to provide an accurate analysis of the maximum force required to shear the fibres in the slice.
4. Once the slice has been sheared completely through the center, save and record the data.

Results

Thirty-one finished commercial beef steers were slaughtered and their carcasses (528 - 601 kg) were split. In order to create variability in tenderness, right sides were immediately stored at 2 °C, while the left sides were held at 10 °C for 3 hr and then at 2 °C. The longissimus muscles from right and left sides were removed 24 hr after slaughter. Samples from the right sides ("TOUGH" treatment) were analyzed that day, while samples from the left side ("TENDER" treatment) were aged for 6 d before being analyzed...

Discussion

The angle adjustable box ensures the SSF blade always shears muscle fibres at a true perpendicular angle, rather than approximately perpendicular which could happen with a fixed 45 ° angle cut⁸. The application of the variable angle cutting box allows for more accurate depictions of the maximal shear force in a sample, and it is on this basis of improving objective quality analysis techniques that the variable angle cutting box was developed. Furthermore, the wide range of angles presented by the angle adj...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Vacuum Packager	Koch Equipment, Kansas City, MO, USA	Model UV2100
Vacuum bags	Winpak Ltd., Winnipeg, MB, Canada
Thermocouples and Scanning Device	Agilent / Hewlett Packard, Santa Clara, CA, USA	34970A Data Acquisition Switch Unit
Grill	Garland Commercial Ranges Ltd., Mississauga, ON, Canada	Model ED-30-B
Crisco Vegetable Shortening	The J.M. Smucker Company, Orrville, OH, USA
Sample sizing box	G-R Manufacturing Co., Manhattan, KS, USA
Angle adjustable box	Innovation Centre, Red Deer College, Red Deer, AB, Canada
Texture Analyzer Machine	Texture Technologies, Hamilton, MA, USA	Model TA-XT Plus
Load Cell, 50 kg	Texture Technologies, Hamilton, MA, USA	TA-XT Plus
USDA Warner-Bratzler knife w/guillotine block	Texture Technologies, Hamilton, MA, USA	TA-7
Flat rectangle Blade for Slice Shear Force	Texture Technologies, Hamilton, MA, USA	TA-7C