## 4 Conclusions  
The volatile profiles of raw beef steak samples initially packaged in MAP, VP, and CP were determined over a 7-day period. SPME combined with GC-accurate mass QTOFMS was utilised for sample analysis, and 35 volatile compounds were identified across the three packaging systems. Two compounds (acetoin and carbon disulphide) and one contaminant (2-vinyloxyethanol) were detected in meat from all three packaging systems and a further five compounds (2,3-butanediol, 7-ethyl-1,3,5-cyclohexutriene, 1,3-bis(1,1-dimethyl-ethyl)benzene, hexanal, and toluene) were present in at least two systems. The trends in relative abundance of these compounds over time differed between packaging systems and can also possibly be related to packing dates. Many compounds that were previously reported from cooked meat were assumed to be generated by thermal processes; for instance, the Maillard reaction or lipid oxidation. The current work shows that these compounds are also released from packaged raw beef without any heat treatment. Therefore, it can be concluded that heat is not the primary release factor, and that the packaging conditions play an important role in the release profile of volatile compounds from raw beef. Many of the common compounds detected in this qualitative study are indicative of meat spoilage and information about their presence, absence, and abundance over time could be used to indicate packaged meat freshness. The demonstrated relationships between packaging systems, volatile compounds, and storage times therefore have potential application in the development of packaged raw meat freshness and quality sensors. The following are available online at [[https://www.mdpi.com/article/10.390/foods10092018/s1](https://www.mdpi.com/article/10.390/foods10092018/s1)]([https://www.mdpi.com/article/10.390/foods10092018/s1](https://www.mdpi.com/article/10.390/foods10092018/s1)). Table S1: Summary of the volatile compounds detected from or associated with raw and cooked meat samples. Figure S1: Total ion chromatogram of blank sample. Figure S2: Total ion chromatogram of VOCs of raw beef steaks from MAP; the compounds identified are summarised in Table S2. Table S2: Volatile compounds identified in this study from MAP packaged raw beef steaks. Figure S3: Total ion chromatogram of VOCs of raw beef steaks from CP; the compounds identified are summarised in Table S3. Table S3: Volatile compounds identified in this study from CP packaged raw beef steaks. Figure S4: Total ion chromatogram of VOCs of raw beef steaks from VP; the compounds identified are summarised in Table S4. Table S4: Volatile compounds identified in this study from VP packaged raw beef steaks. Figure S5: The average area, expressed as a percentage of all analytes, of 2-(vinyloxy)ethanol; \(n=3\), \(\pm\)S.E. Figure S6: The average area, expressed as a percentage of all analytes, of 2,3-butanediol; \(n=3\), \(\pm\)S.E. Figure S7: The average area, expressed as a percentage of all analytes, of 7-ethyl-1,3,5-cyclohexutriene; \(n=3\), \(\pm\)S.E. Figure S8: The average area, expressed as a percentage of all analytes, of 1,3-bis(1,1-dimethyl-ethyl)benzene; \(n=3\), \(\pm\)S.E. Figure S9: The average area, expressed as a percentage of all analytes, of hexanal, \(n=3\), \(\pm\)S.E. Figure S10: The average area, expressed as a percentage of all analytes, of toluene; \(n=3\), \(\pm\)S.E. Table S5: Volatile compounds from this study which are identified only by molecular features (containing hydrocarbon or alcohol) along with peaks observed in the GC experimental results which were unable to be identified. Conceptualization, Y.N. ; Data curation, Y.N. ; Formal analysis, D.B. ; Funding acquisition, J.T. and K.L.T. ; Investigation, D.B. ; Methodology, D.B. ; Resources, P.J.M. ; Supervision, J.T. and K.L.T. ; Writing--original draft, D.B. ; Writing--review and editing, P.J.M., J.T. and K.L.T. All authors have read and agreed to the published version of the manuscript. M.A.M.