Identification of Microbial Flora in Dry Aged Beef to Evaluate the Rancidity during Dry Aging

Sejeong Kim,Sunhyun Park,Jong-Chan Kim,Yohan Yoon,Jinkwi Kim,Heeyoung Lee

doi:10.3390/pr9112049

Abstract

Dry aging creates a unique taste and flavor in beef; however, the process also causes rancidity, which is harmful to humans. During dry aging, the microbial flora in beef changes continuously; thus, this change can be used as an indicator of rancidity. The objective of this study was to analyze the correlation between microbial flora in beef and rancidity during dry aging. The round of beef (2.5–3 kg) was dry aged under 1.5 ± 1 °C and 82 ± 5% moisture for 17 weeks. The microflora in the dry aged beef was analyzed by pyrosequencing. The volatile basic nitrogen (VBN) and thiobarbituric acid reactive substance (TBARS) values were also measured. Primers were designed to detect and quantify bacteria using real-time polymerase chain reaction (RT-PCR). The VBN and TBARS values in the dry aged beef depreciated from week 11 of aging. The levels of Streptococcus spp., Pantoea spp., and Pseudomonas spp. significantly changed at around week 11. Quantitative RT-PCR showed that the levels of Pantoea spp. and Streptococcus spp. could be used to identify rancidity during dry aging. Thus, among the microbial flora in dry aged beef, Pantoea spp. and Streptococcus spp. can be used to determine the rancidity of dry aged beef.

Highlights

Dry aging, a process that involves the long-term storage of meat at low temperatures and relative humidity, can improve meat quality, which is represented by the development of tenderness and a unique flavor
Pseudomonas spp., the main spoilage bacterium, metabolizes glucose, lactate, and amino acid, which results in the formation of slime and generation of off-odor, while lactic acid bacteria cause greening as a consequence of H2 O2 generation [7,8]
Lipid oxidation and protein putrefaction are highly related to a decrease in taste and flavor in spoiled meat, which are reflected in the thiobarbituric acid reactive substance (TBARS) and volatile basic nitrogen (VBN) values, respectively

Summary

Introduction

A process that involves the long-term storage of meat at low temperatures and relative humidity, can improve meat quality, which is represented by the development of tenderness and a unique flavor. These quality factors are considerably affected by aging conditions, such as temperature, air velocity, and humidity [1]. Pseudomonas spp., the main spoilage bacterium, metabolizes glucose, lactate, and amino acid, which results in the formation of slime and generation of off-odor, while lactic acid bacteria cause greening as a consequence of H2 O2 generation [7,8] Psychrotrophs, such as pseudomonads and lactobacilli, largely contribute to the spoilage of meat at chilling temperatures and continuously compete with each other during the storage time

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