Evaluating the Shelf Life and Sensory Properties of Beef Steaks from Cattle Raised on Different Grass Feeding Systems in the Western United States

Abstract

Consumer interest in grass-fed beef has been steadily rising due to consumer perception of its potential benefits. This interest has led to a growing demand for niche market beef, particularly in the western United States. Therefore, the objective of this study was to assess the impact of feeding systems on the change in microbial counts, color, and lipid oxidation of steaks during retail display, and on their sensory attributes. The systems included: conventional grain-fed (CON), 20 months-grass-fed (20GF), 25-months-grass-fed (25GF) and 20-months-grass-fed + 45-day-grain-fed (45GR). The results indicate that steaks in the 20GF group displayed a darker lean and fat color, and a lower oxidation state than those in the 25GF group. However, the feeding system did not have an impact on pH or objective tenderness of beef steaks. In addition, consumers and trained panelist did not detect a difference in taste or flavor between the 20GF or 25GF steaks but expressed a preference for the CON and 45GR steaks, indicating that an increased grazing period may improve the color and oxidative stability of beef, while a short supplementation with grain may improve eating quality.

Keywords: flavor profile; grain-fed beef; grass-fed beef; palatability; shelf life; tenderness.

Figure 1

(a) Lean muscle L* values (lightness) of steaks over a six-day retail display period from conventional grain-finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-grain-finished beef (45GR), and 25-months-grass-fed beef (25GF). Steaks in the CON group possessed higher L* values throughout display time compared to the other groups (p < 0.05), while the 20GF group possessed the lowest L* values (p < 0.05). The L* values decreased for all the steaks regardless of treatment group at the end of retail display. (b) Lean muscle a* values (redness) of steaks over a six-day retail display period from conventional grain-finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-grain finished beef (45GR), and 25-months-grass-fed beef (25GF). After D2, a* values decreased dramatically for the 20GF group (p < 0.05) while the CON group had the highest a* values towards the end of the display period (p < 0.05). The a* values decreased for all the steaks regardless of treatment group at the end of retail display. (c) Lean muscle b* values (yellowness) of steaks over a six-day retail display period from conventional grain-finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-rain-finished beef (45GR), and 25-months-grass-fed beef (25GF). Treatment groups 20GF and 45 GR had the lowest b* values while the CON and 25GF groups had the highest b* values (p < 0.05). The b* values decreased for all the steaks regardless of treatment group at the end of retail display.

Figure 1

(a) Lean muscle L* values (lightness) of steaks over a six-day retail display period from conventional grain-finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-grain-finished beef (45GR), and 25-months-grass-fed beef (25GF). Steaks in the CON group possessed higher L* values throughout display time compared to the other groups (p < 0.05), while the 20GF group possessed the lowest L* values (p < 0.05). The L* values decreased for all the steaks regardless of treatment group at the end of retail display. (b) Lean muscle a* values (redness) of steaks over a six-day retail display period from conventional grain-finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-grain finished beef (45GR), and 25-months-grass-fed beef (25GF). After D2, a* values decreased dramatically for the 20GF group (p < 0.05) while the CON group had the highest a* values towards the end of the display period (p < 0.05). The a* values decreased for all the steaks regardless of treatment group at the end of retail display. (c) Lean muscle b* values (yellowness) of steaks over a six-day retail display period from conventional grain-finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-rain-finished beef (45GR), and 25-months-grass-fed beef (25GF). Treatment groups 20GF and 45 GR had the lowest b* values while the CON and 25GF groups had the highest b* values (p < 0.05). The b* values decreased for all the steaks regardless of treatment group at the end of retail display.

Figure 2

(a) Values of L* (lightness) for external fat of steaks over a six-day retail display period from conventional grain finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-grain-finished beef (45GR), and 25-months-grass-fed beef (25GF). All the groups were significantly different from each other (p < 0.05). Values of external fat L* were highest in 25GF followed by the CON group, while the 45GR group had the lowest values of L* for external fat. (b) Values of a* for external fat of steaks over a six-day retail display period from conventional grain finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-grain-finished beef (45GR), and 25-months-grass-fed beef (25GF). External fat a* values were lowest for 25GR throughout the retail display (p < 0.05). At the beginning and end of retail display, the 45GR group had the highest a* values for external fat. (c) Values of b* for external fat of steaks over a six-day retail display period from conventional grain finished beef (CON), 20-months-grass-fed beef (20GF), 20-months-grass-fed + 45-day-grain-finished beef (45GR), and 25-months-grass-fed beef (25GF). External fat b* values were highest in the 45GR group followed by the 20GF group (p < 0.05).

Figure 3

Principal Component Analysis (PCA) relating the flavor profile and consumer panel score of steaks from conventional grain finished beef (CON, n = 12), 20-months-grass-fed beef (20GF, n = 12), 20-months-grass-fed + 45-day-grain-finished beef (45GR, n = 9), and 25-months-grass-fed beef (25GF, n = 12).