Abstract :
[en] Stewed beef, a famous Chinese dish, contains beef and other auxiliary ingredients like vegetables and spices. It is highly popular for its attractive flavor and high nutritional value. In China, the precooked Chinese dish (PCD) sector is expanding rapidly. Precooked Chinese stewed beef (PCSB), a representative PCD, has been widely developed because its cooking procedure is more stable and simpler than other Chinese cooking methods such as stir-frying and pan-frying. Most of PCSB dishes are refrigerated and need to be reheated before consumption. Nevertheless, even after a short period of refrigeration within their shelf life, they still develop a characteristic warmed-over flavor (WOF), an off-flavor that diminishes consumer acceptance. Simultaneously, the meaty aroma of PCSB gradually weakens, affecting its sensory quality. The development of WOF is inextricably associated with lipids. On the one hand, an increase in secondary lipid oxidation products is primarily responsible for WOF formation. On the other hand, the lipophilic nature of these odorants allows them to dissolve in lipids and to be gradually released during processing or consumption. Therefore, it is very important to characterize the key aroma-active compounds contributing to WOF in PCSB and identify the lipid markers as potential precursors of WOF, aiming to maintain and improve the flavor quality of PCSB dishes. The objective of the present research was to investigate and confirm the key aroma-active compounds contributing to WOF and the differential lipid markers as potential precursors of WOF, elucidating the pathways involved in WOF formation in PCSB.
Firstly, a sensomics approach was used to characterize the key aroma-active compounds contributing to WOF in reheated PCSB. 36 odorants were identified, and based on flavor dilution factors, odor activity values, aroma recombination, and omission test, hexanal, (E,E)-2,4-decadienal, (E,E)-2,4-nonadienal, pentanal, decanal, octanal, heptanal, (E)-2-octenal, (E)-2-undecenal, 1-octen-3-ol, and (E)-2-nonenal, mainly derived from lipid oxidation were characterized as the key aroma-active compounds contributing to the formation of WOF. In particular, 3-(methylthio)propanal, which was positively correlated with meaty aroma, was also associated with an overall increase in WOF. Thus, these odorants were elected as potential markers of WOF in PCSB. In summary, the WOF in PCSB could be attributed to an overall increase in lipid oxidation products and a decrease in the odorants with desirable aromas. The characterization of WOF in PCSB will aid in the flavor quality control of PCSB dishes.
Secondly, lipidomics was used to investigate the role of lipids in the formation and development of WOF in PCSB. A total of 1236 lipids were detected in cooked and reheated stewed beef. Triacyclglycerols (TGs), notably TG(18:0/18:1/18:1) and TG(16:0/18:1/18:1), were considered key lipids associated with predominant odorants. Among 153 differential lipids (VIP > 1, P < 0.05), phosphatidylserine (PS)(18:0/18:2) and PS(16:0/17:2) were identified as potential markers for distinguishing all samples. A total of 142 differential lipids were significantly correlated with the predominant odorants, with ether-bonded phosphatidylethanolamines (ePEs), particularly PE(P-18:0/18:2), serving as crucial precursors in WOF formation. Furthermore, lysophosphatidylcholine (LPC)(20:3) and phosphatidylcholine (PC)(16:0/18:1) notably facilitated WOF development. The results provide a theoretical basis for flavor correction in precooked Chinese stewed beef dishes.
Finally, the role of tomatoes in mitigating WOF in PCSB was elucidated through analyses of aroma profiles, lipid composition, protein secondary structure, and sensory attributes. Adding tomatoes at 25%, 50%, 75%, and 100% of the raw beef weight significantly inhibited lipid oxidation, reducing losses in phospholipids (e.g., PE, LPC, and PC) and TG, thereby reducing WOF development. Tomato-originated 2-isobutylthiazole exhibited a potent flavor endowment effect on PCSB, with its endowment rate increasing from 602.64% to 2860.10%, thus masking the WOF in PCSB. Tomato additions also altered the secondary structure of beef protein, potentially affecting WOF retention in PCSB. Sensory evaluation revealed that the 75% tomato group achieved the highest overall acceptability, balancing meaty and tomato-like aromas while significantly reducing the WOF. This research offers a viable strategy for reducing WOF in PCSB, thereby enhancing its commercial appeal and consumer acceptance.
In conclusion, the present study has identified lipid oxidation as the primary driver of WOF. Eleven key aroma-active compounds, including hexanal, (E,E)-2,4-decadienal, (E,E)-2,4-nonadienal, pentanal, decanal, octanal, heptanal, (E)-2-octenal, (E)-2-undecenal, 1-octen-3-ol, and (E)-2-nonenal, were confirmed as critical contributors to WOF in the reheated PCSB using sensomics approach. Lipid oxidation was confirmed as the primary driver of WOF. Lipidomics analysis revealed the importance of e-PEs, which are key contributors to WOF formation. Additionally, the study demonstrated the potential of tomato additives to mitigate WOF by inhibiting lipid oxidation and enhancing sensory quality. Specifically, the tomato-originated compound 2-isobutylthiazole played a major role in flavor enhancement, thus masking WOF and improving the sensory quality of the dish. These results provide valuable insights into the molecular mechanisms behind flavor changes in PCSB and offer practical solutions for improving the flavor stability of stewed beef dishes, ensuring better quality control in the production of precooked meat products.
