Project Summary

Strategies to Improve the Tenderness of Vastus Lateralis Muscles   

Principle Investigator(s):
D.A. King, S.D. Shackelford, T.L. Wheeler, & M. Koohmaraie
USDA-ARS-US Meat Animal Research Center
Completion Date:
May 2009

The majority of beef carcass value is attributable to cuts from the rib and loin, which are typically used for steak entrees, particularly in foodservice establishments. As a means to increase overall carcass value, research efforts have focused on identifying muscles from the chuck and round with characteristics suitable for use as steak items. Previous work has identified the rectus femoris (tip center) as having sufficient tenderness and flavor attributes to substitute or alternative for gluteus medius (top sirloin) steaks.

Currently, the rectus femoris is marketed as part of a muscle complex that makes up the beef knuckle subprimal. In order for the rectus femoris to be economically feasible, purveyors must also be able to use the vastus lateralis (tip side). Previous checkoff-funded research has found that the vastus lateralis has unacceptable tenderness characteristics to be suitable to consumers as a foodservice steak item.

The objectives for this project were to develop and evaluate tenderization strategies for beef vastus lateralis muscles.


Beef knuckles were obtained from a commercial processor, transported to a large purveyor’s facility, and aged until 35 days postmortem. Muscles were separated along natural seams to produce rectus femoris and vastus lateralis muscles. Muscles were assigned to one of four tenderization treatments: 1) non-tenderized control, 2) blade tenderized, 3) enhanced up to 15% of initial weight with a solution containing 3% salt and 2% sodium tripolyphosphate, and 4) blade tenderized and enhanced with salt and phosphate solution. After tenderization treatments were applied, muscles were cut into steaks, which were vacuum packaged and frozen until further analysis could be performed.

Steaks were thawed and cooked to a medium degree of doneness before being served to the panel or sampled for slice shear force. Palatability attributes were assessed by an eight-member trained sensory panel. Additionally, tenderness was further assessed using slice shear force. After shearing, slices were retained and used to measure sarcomere length (extent of muscle contraction) and the extent of protein degradation as a result of aging and tenderization treatments. 


Applying blade tenderization and injection treatments improved the tenderness of vastus lateralis (tip side) and rectus femoris (tip center) steaks. The effects of the salt and phosphate injection treatment were much larger than the effect of blade tenderization. Additionally, blade tenderization and phosphate injection had a synergistic effect on reducing thaw and cooking losses and trained sensory panel juiciness ratings.

Non-injected rectus femoris steaks received higher trained sensory panel ratings for overall tenderness than non-injected vastus lateralis steaks (Table 1). Similarly, injected rectus femoris steaks received higher tenderness ratings than injected vastus lateralis steaks. However, vastus lateralis steaks injected with a solution containing salt and phosphate received higher overall tenderness ratings than non-injected rectus femoris steaks.

Previous research in this lab found that rectus femoris steaks were similar in palatability attributes and consumer acceptance to top sirloin steaks. Thus, it appears that injection with a salt and phosphate solution will improve vastus lateralis tenderness sufficiently to justify its use as a steak item in foodservice establishments and thus making the rectus femoris an economically viable steak item.


Rising beef prices have increased the cost of beef entrees at restaurants. Industry contacts indicate that prices have risen to the point at which consumers will seek other, less expensive protein sources. The development of muscles from the chuck and round that are comparable to traditional “middle meat” cuts would increase overall carcass value and provide more affordable options for cost-conscious consumers.

Previous work indicated that rectus femoris aged for 21 to 35 days and blade tenderized was similar in tenderness and consumer acceptance to top sirloin steaks that had been aged for 21 to 35 days and then blade tenderized. However, the rectus femoris is currently marketed as part of the knuckle subprimal, which also contains the vastus lateralis muscle. Unfortunately, consumers found vastus lateralis steaks to be unacceptably tough.

The findings of the current experiment indicate that injection with a salt and phosphate solution can improve tenderness to a level greater than that of blade tenderized rectus femoris steaks. Thus, vastus lateralis can be made suitable for use as a steak menu item. Enabling the use of vastus lateralis and rectus femoris steaks by the foodservice segment of the beef industry should improve demand among cost-conscious consumers, improving restaurant profitability and add to carcass value.

Table 1. Least-squares means for the effects of injection and blade tenderization treatments on purge losses and palability traits of rectus femoris and vastus lateralis steaks.

  • 11=extremely tough; 8 =extremely tender
  • 21= extremely dry; 8 =extremely juicy
  • 31= extremely bland; 8 = extremely intense
  • wxtzLeast-squares means within a column, within an effect, with differing superscripts, differ (P < 0.05)