Nontargeted Metabolomics to Understand the Impact of Modified Atmospheric Packaging on Metabolite Profiles of Cooked Normal-pH and Atypical Dark-Cutting Beef

Abstract

Background: Limited knowledge is currently available on the effects of modified atmospheric packaging (MAP) on the metabolite profiles of cooked beef. The objective was to evaluate the impact of packaging on the cooked color and cooked metabolite profile of normal-pH (normal bright-red color) and atypical-dark-cutting beef (inherently slightly dark-colored) longissimus lumborum muscle. Methods: Normal-pH (pH 5.56) and atypical dark-cutting (pH 5.63) loins (n = 6) were procured from a commercial meat processor. Steaks were randomly assigned to one of three different packaging methods: vacuum packaging, carbon monoxide (CO-MAP), and high oxygen (HiOx-MAP). Following 5 d of retail display, steaks were cooked to 71 °C on a clamshell-style grill, and samples were collected for untargeted metabolites using gas-chromatography mass spectrometry. Results: Raw atypical dark-cutting steaks were less red (p < 0.05) than raw normal-pH steaks. However, there were no differences in internal cooked color between normal-pH and atypical dark-cutting steaks. Steaks packaged in HiOx-MAP steaks had a lower (p < 0.05) cooked redness than vacuum and CO-MAP steaks. A total of 129 metabolite features were identified in the study. Serine and tryptophan were over-abundant in cooked atypical dark-cutting beef compared to raw atypical samples. Citric acid levels were greater in HiOx-MAP packaged beef compared with VP both in normal and atypical dark-cutting beef after cooking, while no differentially abundant metabolites were shared between vacuum and CO-MAP steaks after cooking. Discussion: A slight increase in pH did not influence metabolite profiles in different packaging. However, there were packaging effects within normal and atypical dark-cutting beef. Conclusions: This study suggests that packaging conditions change metabolite profiles, which can influence cooked metabolites. Therefore, the metabolomics approach can be used to better understand cooked color defects such as premature browning.

Keywords: beef; cooked color; dark-cutting; metabolomics; packaging.

Figure 1

Projections to latent-discriminant analysis plot (PLS-DA) of the metabolites present in the raw normal and raw atypical dark-cutting beef longissimus lumborum at the beginning of retail display. Red color denotes atypical dark-cutting samples, while green denotes normal samples.

Figure 2

Projections to latent-discriminant analysis plot (PLS-DA) of the metabolites present in (a) raw normal longissimus lumborum at the beginning of retail display and normal longissimus lumborum following 5 d of retail display and cooking to 71 °C and (b) raw atypical dark-cutting longissimus lumborum at the beginning of retail display and atypical dark-cutting longissimus lumborum following 5 d of retail display and cooking to 71 °C. Red color in both figures corresponds to the respective cooked product, while green indicates raw.

Figure 3

Projections to latent-discriminant analysis plot (PLS-DA) of the metabolites present in cooked (a) atypical dark-cutting beef and (b) normal in different packaging. The red color in both plots corresponds to CO-MAP packaged steaks, green corresponds to HO-MAP (high-oxygen MAP), and blue denotes vacuum packaged steaks.