Effects of Three Peeling Methods on the Quality of White Pepper

In this study, the effects of three peeling methods: mechanical peeling, soaking in still water and soaking in flowing water on physical and chemical indicators of white pepper such as whiteness value, black fruit percentage, broken fruit percentage, bulk density, moisture content, piperine content, and essential oil content were investigated. The composition and content of volatile compounds in the essential oils of white pepper were qualitatively and quantitatively analyzed by gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS). The quality of peeled white pepper was evaluated by weighted analysis. Our results showed that there was no significant difference in the whiteness value between mechanically peeled white pepper and that peeled by flowing water soaking, but their whiteness values were higher than that of white pepper peeled by still water soaking. Mechanical peeling resulted in lower black fruit percentage and piperine content, but higher essential oil content, broken fruit percentage and bulk density compared with water soaking. A total of 33 volatile compounds were identified from the essential oils obtained by the three peeling methods, 21 compounds of which were common to all the oils, the predominant ones being 3-carene (41.96, 37.77 and 39.16 mg/mL, respectively), β-caryophyllene (36.43, 41.57 and 41.02 mg/mL, respectively), and limonene (29.38, 23.38 and 39.38 mg/mL, respectively). The electronic nose data showed that the flavor of the three white pepper samples was significantly different. The sensory evaluation showed that mechanically peeled white pepper had a stronger aroma and no odor. Furthermore, the weighted score of mechanically peeled white pepper was higher than that of white pepper peeled by water soaking. Therefore, the comprehensive quality of mechanically peeled white pepper is good, and it is suitable for large-scale production. The experimental results can provide a theoretical basis for pepper quality evaluation and industrial production.