Using Advanced Analysis to Track Amino Acid and Scent Changes in Growing Onions

Greg Howard
26th June, 2024

Using Advanced Analysis to Track Amino Acid and Scent Changes in Growing Onions

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Ningxia University studied Lou onions to find the best time to harvest for optimal flavor
  • They identified 17 amino acids and 61 volatile substances in the onion pseudostems
  • The best flavor occurs just before the flower stems emerge, making this the ideal harvesting time
The Lou onion, prized for its unique flavor, has traditionally been harvested based on size and market price rather than optimal flavor quality. This study conducted by researchers at Ningxia University aims to provide evidence-based insights into the optimal harvesting time to maximize the flavor quality of the Lou onion pseudostem[1]. To achieve this, the researchers employed amino acid analysis and gas chromatography-ion migration spectroscopy (GC-IMS) to identify and quantify the various compounds present in the pseudostem at different growth phases. They discovered a total of 17 amino acids and 61 volatile substances. Among these, 18 compounds were identified as key determinants of the pseudostem's flavor characteristics. These compounds included arginine (Arg), aspartic acid (Asp), glutamic acid (Glu), valine (Val), and a range of volatile substances such as (E)-2-nonenal, decanal, and linalool. The study's findings are significant because they provide a detailed profile of the flavor compounds in Lou onion pseudostems, allowing for a more informed decision on the optimal harvesting period. The key flavor compounds were identified using taste activity value and relative odor activity value calculations, which are methods to assess the contribution of each compound to the overall flavor profile. Correlation analysis further highlighted five amino acids and 38 volatile compounds with variable importance for predictive components scores of greater than 1. This analysis pinpointed anisaldehyde, eugenol, (Z)-6-nonen-1-ol, 2,4-decadienal, and 3-sec-butyl-2-methoxypyrazine, along with Arg, Asp, and Val, as major contributors to the pseudostem's flavor profile. The study concluded that the most prominent flavor of Lou onion pseudostems occurs during the rapid growth phase just before the emergence of the flower stems. This stage is thus recommended as the optimal harvesting time, compared to the regreening growth stage and the rapid growth period of the aerial bulbs. This research ties into previous studies on the importance of volatile compounds in determining the quality of traditional Chinese medicines like Peucedanum praeruptorum Dunn (PPD)[2]. Similar to the PPD study, where the abundance of volatile components was found to peak at a specific time, the Lou onion study emphasizes the significance of timing in harvesting to maximize flavor quality. Furthermore, the broader context of plant volatile compounds, as discussed in the study of plant-derived volatiles for commercial use[3], supports the importance of understanding and optimizing these compounds for better flavor and aroma profiles. In summary, the research conducted by Ningxia University has provided valuable insights into the optimal harvesting time for Lou onion pseudostems by identifying key flavor compounds and their growth phases. This evidence-based approach can help farmers and consumers make more informed decisions, ultimately enhancing the flavor quality of Lou onions.

VegetablesBiochemPlant Science


Main Study

1) Combining multivariate statistical analysis to characterize changes in amino acids and volatiles during growth of Lou onion pseudostems.

Published 24th June, 2024

Related Studies

2) Determination of Characteristic Volatile Component Fingerprint of Peucedanum Praeruptorum Dunn at Different Harvest Periods Based on HS-GC-IMS.

3) Biosynthesis of plant-derived flavor compounds.

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