A comparison of meat quality and sensory attributes in fresh and frozen American lamb using two different muscles

NDSU-raised lambs (n = 12) were slaughtered at the NDSU Meats Laboratory. After a 24-hour chill, loin and leg subprimals were collected from each carcass and assigned to either fresh (FRSH) or frozen (FRZN) treatment. Meat quality and sensory tests were performed on each sample. Consumer panelists (n = 84) were given paired samples of LL and SM and were asked to evaluate overall like, flavor, tenderness and juiciness on a continuous line scale. No differences were observed (P ≥ 0.10) between treatments for primal weight loss, cook loss or Warner-Bratzler shear force in either the LL or SM. However, LL and SM samples in the FRSH treatment had less drip loss compared with samples in the FRZN treatment (P = <0.001). In LL, sensory samples in the FRSH treatment had greater (P = 0.01, P = 0.02, P = 0.03, respectively) overall like, tenderness and juiciness scores compared with samples in the FRZN treatment. However, no differences in flavor scores were observed in LL sensory samples in the FRSH treatment compared with samples in the FRZN treatment. Additionally, no differences in overall like, flavor, tenderness or juiciness scores were observed (P ≥ 0.77) in SM sensory samples in the FRSH treatment compared with samples in the FRZN treatment. Results indicate retailers may use frozen storage on lamb legs, however, consumers do discriminate against loin chops treated to frozen storage due to water loss and perceived tenderness issues.

A common challenge in the U.S. lamb industry is inconsistencies in the supply of fresh lamb related to lambing time and rates in the traditional U.S. lamb system, with about 80% of the U.S. lamb crop being born in the first five months of the year (Redden et al., 2018). The use of frozen lamb could resolve some of these issues during spikes in lamb demand around the Christmas and Easter holidays. However, retailers often discriminate against frozen lamb in the retail case.

Some research has been performed on meat quality and sensory attributes of frozen lamb. However, conclusions are inconsistent on whether frozen lamb is a viable option for U.S. retailers (Smith et al., 1968; Muela et al., 2016). Therefore, additional research is needed to understand how freezing affects meat quality and sensory attributes of American lamb to provide better research-based guidance to retailers and food service on the consumer perceptions of frozen lamb and whether frozen lamb is a viable option for U.S. consumers.

NDSU-raised lambs (n = 12) were slaughtered at the NDSU Meats Laboratory. After a 24-hour chill, loin and leg subprimals were collected from each carcass. Subprimals were split in half and each side was assigned to either fresh (FRSH) or frozen (FRZN) treatment. Each half was weighed before being vacuum sealed.

Subprimals assigned to the FRSH treatment were stored in a cooler at 3 C for 14 days while subprimals assigned to the FRZN treatment were stored in a freezer for 13 days at 3 C + one day of thawing. Before fabrication, subprimals were removed from bags and reweighed for primal weight loss. After weighing, loin subprimals were fabricated starting at the cranial end, while the SM was removed from the leg subprimal and fabrication began at the distal end.

For both muscles, an approximately 1.27-centimeter (cm) chop was removed for drip loss analysis, an approximately 2.54-cm chop was fabricated, vacuum-sealed and stored at 3 C for Warner-Bratzler shear force (WBSF) and cook loss evaluation, and the remaining chop samples were used for sensory evaluation. Drip loss was determined during a 24-hour period from suspended 25-gram (g) samples. Warner-Bratzler shear force and cook loss analysis was conducted in accordance with American Meat Science Association guidelines.

Sensory evaluation was conducted 24 hours after sample fabrication. Consumer panelists (n = 84) were given paired samples of LL and SM and were asked to evaluate overall like, flavor, tenderness and juiciness on a continuous line scale. Data were analyzed using the PROC Mixed procedure SAS Studio® (SAS Institute, Cary, N.C.) with means being separated with the PDIFF option and were considered significant when P ≤ 0.05.

No differences were observed between treatments for primal weight loss, cook loss or WBSF in the LL or SM (P ≥ 0.10; Table 1). However, LL and SM samples in the FRSH treatment had (P = 0.01, P = 0.02, P = 0.03, respectively; Table 2) less drip loss compared with samples in the FRZN treatment (P = <0.001; Table 1).

a,b - Means in same row without common superscript differ (P < 0.05).

Sensory samples in the FRSH treatment had greater overall like, tenderness and juiciness scores compared with samples in the FRZN treatment. However, no differences in flavor scores were observed in LL sensory samples in the FRSH treatment compared with samples in the FRZN treatment. Additionally, no differences (P ≥ 0.77; Table 2) in overall like, flavor, tenderness or juiciness scores were observed in SM sensory samples in the FRSH treatment compared with samples in the FRZN treatment.

10 = greatest disliking, 100 = greatest liking
a,b - Means in same row without common superscript differ (P < 0.05).

Our results indicate minimal influence on meat quality and sensory attributes of SM in lamb when frozen. Industry application of frozen storage may be beneficial for supply of legs. However, we did identify negative influences on sensory attributes to lamb LL by freezing, specifically related to water-holding capacity and juiciness.

Overall consumer like differences are attributed to the perceived juiciness and tenderness, while flavor profiles of fresh vs. frozen lamb were indistinguishable. Therefore, maintaining fresh lamb loin chops in retail and food service offers the greatest opportunity for consumer satisfaction. However, further research is warranted due to the short freezing time of samples in this project.

This project was supported by a grant from the North Dakota State Board of Agricultural Research and Education. The authors also greatly appreciate the contributions from the members of the NDSU Meat Lab.

Muela, E., P. Monge, C. Sanudo, M.M. Campo, J.A. Beltran. 2016. Sensory quality of lamb following long-term frozen storage. Meat Sci:114 32-37.

Redden, R., E. Sanko, R. Ehrhardt, C. Hiemke. 2018. Seasonality of the U.S. Lamb Industry. American Lamb Board. 1-17.

Smith, G.C., C.W. Spaeth, Z.L. Carpenter, G.T. King, K.E. Hoke. 1968. The effects of freezing, frozen storage conditions, and degree of doneness on lamb palatability characteristics. J Food Sci:33 19-24.