*Allium fistulosum*, or green onion, is a globally consumed vegetable valued for its polyphenols and health benefits. Its stalk contains approximately 16% polysaccharides with complex structures beneficial for gut microbiota. However, allicin, responsible for the characteristic pungent odor, limits its use in dietary fiber supplements. While allicin offers various health advantages, including antioxidant and antimicrobial properties, its odor remains a significant barrier. Numerous methods exist for allicin removal, including thermal decomposition, blanching, and treatments involving tea polyphenols or citric acid. However, a comprehensive comparison of these methods’ efficiency is lacking. This study aims to address this gap by systematically evaluating various allicin removal techniques from *Allium fistulosum* stalks to identify the most efficient and cost-effective method for producing odorless dietary fiber supplements.

Previous research on allicin has focused on its various biological activities, its thermal decomposition kinetics (following first-order reaction kinetics), and its retention during freezing. While studies suggest that tea polyphenols may interact with allicin, reducing odor, and citric acid's effect on allicin content in garlic has been observed, its impact on *Allium fistulosum* remains unexplored. Moreover, methods for determining allicin content have typically relied on its reaction with cysteine, followed by DNTB measurement; however, these methods often lack optimization for maximal allicin extraction from *Allium* sources.

The study began by optimizing the allicin extraction protocol. The effects of water incubation time (5-35 min) and ethanol concentration (45-95%) were examined. Allicin was determined using a modified spectrophotometric method based on its reaction with cysteine and DNTB, measuring absorbance at 412 nm. Various allicin removal methods were then evaluated: **Chemical Removal:** * **Tea Polyphenols:** Experiments varied tea polyphenol concentration (4-12 g/L), processing time (5-25 min), and solid-liquid ratio to determine optimal conditions for allicin removal. Orthogonal partial least squares discriminant analysis (OPLS-DA) was used to analyze the impact of these factors. * **Citric Acid:** Different concentrations of citric acid (0.125-2.0 g/L) were tested, assessing their effects on allicin removal. **Physical Removal:** * **Freezing:** The chopped stalk was frozen at 4 °C, -20 °C, and -80 °C for varying durations (0.5-1.5 h). * **Blanching:** Blanching was performed at 60 °C (1-5 min) and 100 °C (4-32 sec). Allicin content was measured in each treatment group using the optimized extraction and spectrophotometric method. Statistical analysis (one-way ANOVA with Duncan's test) was conducted using SPSS to determine significant differences between treatment groups.

The optimal allicin extraction was achieved by incubating chopped *Allium fistulosum* stalk in water for 20 min, followed by extraction with 75% ethanol. Chemical methods showed varying degrees of effectiveness. Tea polyphenols treatment yielded a maximal allicin clearance rate of 51.4% under optimized conditions (20 min processing time, 6 mg/mL concentration, 1:1.5 solid-liquid ratio). Citric acid treatment showed a maximum clearance rate of 54%. Regarding physical methods, freezing at all tested temperatures yielded a maximal clearance rate of approximately 43%, while blanching at 60°C reached a maximum of 13%. However, blanching at 100°C exhibited a significantly higher clearance rate, reaching 73.3% at 32 sec. This method was considerably more efficient than all other techniques examined. The OPLS-DA analysis of the tea polyphenol treatment revealed that processing time was the most influential factor for allicin removal, followed by polyphenol concentration and solid-liquid ratio.

The findings indicate that high-temperature blanching is the superior method for removing allicin from *Allium fistulosum* stalks, providing a practical and efficient way to eliminate the undesirable odor while preserving dietary fiber. The effectiveness of blanching at 100 °C might be attributed to the thermal decomposition of allicin into less odorous compounds, as previous research has demonstrated. The lower efficacy of the chemical treatments, while showing some effect, suggests that these methods may not be as effective as the direct thermal degradation of allicin. This study provides valuable data for the development of a green and efficient method for producing dietary fiber supplements from *Allium fistulosum* stalks.

This study successfully optimized allicin extraction and comprehensively compared various allicin removal methods from *Allium fistulosum* stalks. High-temperature blanching at 100 °C emerged as the most efficient technique, achieving a 73.3% clearance rate. This provides a practical and environmentally friendly approach for producing high-quality dietary fiber supplements. Future research could explore the impact of blanching on other bioactive compounds in the stalk and investigate the detailed chemical transformation of allicin during the high-temperature blanching process.

The study focused solely on the removal of allicin and did not extensively investigate the effect of these treatments on other valuable bioactive compounds present in the *Allium fistulosum* stalk. Further research is needed to evaluate the overall nutritional profile and functional properties of the dietary fiber produced after allicin removal by different methods. The study was conducted using *Allium fistulosum* from a single source; therefore, the generalizability of the findings to other sources and cultivars of *Allium fistulosum* needs to be confirmed.