Effects of different processing methods on the flavor quality of green huajiao (Zanthoxylum bungeanum) oil

Huajiao (Zanthoxylum bungeanum) oil is one of the most important condiments in China, especially in Sichuan and Chongqing. Cold pressing, vegetable oil extraction, and blending are the main technologies to produce huajiao oil at present. There are some differences in the flavor and quality of huajiao oil, due to its processing modes. Among them, pungency and aroma are two indexes to measure the quality of huajiao oil. However, the existing studies focus mostly on the single characteristics of aroma or pungency. In this study, a systematic investigation was implemented to explore the influence of processing modes on the flavor quality of huajiao oil. The pungency and volatile substances were also combined with sensory evaluation. The research objects were taken as the cold-pressed fresh green huajiao oil (LZO), hot-boiled fresh green huajiao oil (RXO), hot-boiled dried green huajiao oil (RGO) and high-temperature oil drenched fresh green huajiao oil (GWO). Gas chromatography-mass spectrometer (GC-MS) and quantitative descriptive analysis (QDA) were adopted to determine the types, contents, and aroma characteristics of volatile organic compounds (VOCs) in green huajiao oil samples. Then high-performance liquid chromatography (HPLC), time intensity (TI), and quantitative descriptive analysis (QDA) were used to qualitatively and quantitatively analyze the pungency substances and pungency of green huajiao oil samples. The experimental results showed that 24, 23, 26, and 19 kinds of VOCs were detected in RGO, RXO, LZO, and GWO, respectively. Among them, alcohols (40.91%-90.95%) and terpenes (7.34%-56.39%) accounted for the largest proportion. The content of linalool was the highest among the four kinds of green huajiao oil (282.29-359.66 μg/g), followed by D- limonene, Sabinene, β-myrcene, Sabinene hydrate, Terpinen-4-ol, and α-Terpineol. Odor activity value (OAV) analysis showed that the OAV of linalool was the highest among the four kinds of green huajiao oil, followed by α-terpineol, nerolidol, β-myrcene, and D- limonene. Compared with the first five kinds of volatile substances, there was a lower OAV of volatile substances. But they were all greater than 1, which contributed to the aroma presentation of green huajiao oil. In terms of aroma attributes, LZO samples shared the strong green, citrus, and camphor smell, as well as light floral and piney; RXO was rich in cocoa aroma, sweet aromatics, floral floral, piney, and fatty; RGO was rich in fatty and slightly sweet aromatics; GWO was mild sweet aromatics and fatty. Furthermore, the total amount of pungency flavor substances in four samples of green huajiao oil was between 3.01 and 5.86 mg/g. The total amount of GWO was the lowest (3.01 mg/g), but the rest three (5.63-5.86 mg/g) shared no significant difference (P＜0.05). Finally, the evaluation of pungency sensation showed that LZO, RXO, and RGO had similar pungency sensation-time characteristics. The overall pungency sensation intensity was significantly higher than that of GWO (P<0.05). In addition, there was the close numbing, vibrating, burning, tingling, and salivating of RXO, RGO, and LZO. In contrast, the pungency properties of GWO samples all showed the lowest level. Consequently, there were great differences in the aroma and pungency sensation in the green huajiao oil that was produced by different processing. For example, LZO shared the strongest overall pungency sensation, where the aroma type was pristine. While the RXO and RGO exhibited a stronger overall pungency sensation, where the aroma types were full-bodied and stimulating, respectively. The GWO had the lowest overall pungency sensation and mild aroma type. The green huajiao oil with different aroma types and pungency intensity can be expected to produce, according to their favorite aroma and pungency taste. Thus, there were specific effects of different processing modes on the aroma and pungency sensation of green huajiao oil. The finding can also provide a strong theoretical basis to optimize the processing technology and market application of green huajiao oil.