Study on the effects of granularity of paprika on physicochemical properties and volatile flavor compounds of chili oil

<b>Objective:</b> This study aimed to investigate the effects of granularity of paprika on the physical and chemical properties and volatile flavor compounds of chili oil. <b>Methods:</b> Chili oil samples（KLD2-KLD5）were prepared from mechanically crushed paprika with different granularity （35, 30, 26, 20 mesh）, and the content of capsaicinoids, chromatic aberration value, and peroxide value of oil samples were determined by high performance liquid chromatography（HPLC）, colorimeter and other methods. The types and contents of volatile flavor compounds were detected and analyzed by gas chromatography-ion mobility spectrometry （GC-IMS） combined with principal component analysis （PCA）, partial least squares discriminant analysis （PLS-DA）, and heat map cluster analysis. In addition, a comparative analysis was performed with the traditional hand-milled chili oil sample （KLD1）. <b>Results:</b> In the KLD2-KLD5 chili oil samples prepared with mechanically crushed paprika, the concentration of capsaicin, dihydrocapsaicin and capsaicinoids, scoville heat units （SHU） and pungency degree decreased with the increase of the granularity of paprika. The peroxide value increases with the increase of the granularity, and the brightness <i>L</i>* increased first and then decreased with the decrease of the granularity, and there was a significant difference（<i>P</i>＜0.05） had been observed. A total of 58 volatile organic compounds （VOCs） were identified by GC-IMS, mainly including: alcohols, aldehydes, ketones, carboxylic acids, esters, heterocyclics and thioethers, with 10, 18, 12, 4, 7, 5 and 2 types respectively. GC-IMS fingerprints combined with the relative percentage of VOCs showed that the types of VOCs in KLD2-KLD5 samples were the same, but the contents were different. The types and content of VOCs in KLD1 were quite different from those in KLD2-KLD5. Fourteen key differential markers of 5 chili oils were screened by PLS-DA. The results of principal component analysis, nearest neighbor analysis, and heat map clustering analysis of VOCs in five kinds of chili oil samples were consistent with the results of GC-IMS fingerprints. These samples could be accurately distinguished and the flavor of KLD1 was the most unique. <b>Conclusion:</b> The granularity of paprika had a significant impact on the dissolution rate of capsaicin and dihydrocapsaicin in chili oil, peroxide value, and brightness <i>L</i>* （<i>P</i>＜0.05）, but has no effect on the types of volatile flavor compounds in chili oil. However, the content of volatile flavor compounds in each sample had a certain difference.