par Morm, Elen 
Président du jury Gilis, Dimitri
Promoteur Debaste, Frédéric
Co-Promoteur Haut, Benoît
Publication Non publié, 2021-06-21
Président du jury Gilis, Dimitri
Promoteur Debaste, Frédéric
Co-Promoteur Haut, Benoît
Publication Non publié, 2021-06-21
Thèse de doctorat
| Résumé : | Pepper (Piper nigrum L.) production has a centuries-long history linked to the Cambodian territory. This spice was first grown in Kampot province and has now spread widely to other provinces in Cambodia. Pepper has myriad health benefits for consumers due to the presence of various bioactive compounds. This work aimed to improve understanding of the key elements influencing the quality of the Cambodian pepper. The research is divided into four main parts: a review article on piperine content and drying conditions of pepper (Piperaceae family); an observational study of traditional processing and evaluation of bioactive compounds, piperine, and essential oil content of several black pepper (P. nigrum) varieties grown in different regions of Cambodia; an experimental characterisation of drying Kampot red pepper; and an exploration of the effect of processing operation on colour, bioactive compounds, piperine and essential oil content of white pepper (P. nigrum).The first section describes research on piperine extraction and quantification in peppers from the Piperaceae family. This includes the various processing techniques as well as extraction and analytical methods. Based on the review, Soxhlet extraction and high-performance liquid chromatography coupled to an ultraviolet detector have been most and commonly used to qualify and to quantify the piperine content in peppers. In the second section, traditional pepper processing in Cambodia was observed by using a questionnaire given to farmers. The survey was conducted in five provinces in Cambodia: Kampot, Kep, Tboung Khmum, Ratanakiri, and Mondulkiri, where pepper varieties such as Khmer, Malaysian, and Indian were collected for analysis. The processing operation including pre-treatment and drying technique of white, black, and red pepper varies from farmer to farmer and from region to region. The different varieties of pepper cultivated in Cambodia have distinct qualities. The total phenolic content (TPC) rangedfrom 4.33 to 12.57 mg gallic acid equivalents/g dry mass and antioxidant activity was from 1.03 to 3.75 mg vitamin C equivalents/g dry mass. The piperine content was 2.72%-4.31%, while the essential oil content was 1.75%-4.05%. The Khmer variety had the highest piperine content whereas the Indian variety had the highest TPC. The location of the pepper plantation did not influence TPC, antioxidant activity, piperine content, and essential oil content; however, pepper variety impacted TPC, piperine, and essential oil content.The third section includes the experimental characterisation of drying mature Khmer cultivar pepper (P. nigrum) harvested from Kampot province in Cambodia. Different pre-treatment in boiling water (0, 5, 10, and 15 min) and drying temperatures (55 and 65°C) were evaluated. TPC, total flavonoid content (TFC), and piperine content of mature peppers were determined after processing. The drying temperature altered significantly colour, TPC, and TFC of mature peppers but did not affect the piperine content. Increasing the drying temperature caused more degradation. Nevertheless, pretreatment in boiling water reduced the alterations and increased the drying rate. To produce the dry mature pepper, the Khmer cultivar should be pre-treated in boiling water for 5 min before drying at 55°C because this condition best preserves the colour of mature pepper and the content of bioactive compounds.The fourth section addresses the effect of the processing operation (pre-treatment in boiling water, soaking, and drying) on colour and content of bioactive compounds, piperine, and essential oil of Khmer cultivar white pepper (P. nigrum). The white pepper was produced from different maturation stages such as green mature, mid-ripe, and fully ripe harvested from Ratanakiri province in Cambodia. All of the samples were pre-treated in boiling water for 0, 10, 15, or 30 min and soaked in water for 2 days for mid-ripe and fully ripe and 4 days for green mature. After removing the skin, the pepper grains were oven dried at 65°C for 24 h. The colour was measured and TPC, antioxidant activity, and piperine content were determined. The processing operation did not affect the essential oil and piperine content of white pepper. However, it had a significant influence on the colour, TPC, antioxidant activity, and drying kinetics of white pepper. The TPC and antioxidant activity were lost after the skin removal and pre-treatment in boiling water for 10 min, changes that led to increased drying kinetics. However, when boiled for more than 10 min, the drying kinetics remained stable.Overall, this research has contributed new insights and information related to the processing of black, red, and white pepper. The results of this work could help farmers to understand more about traditional practices towards pepper processing. Moreover, farmers could choose the right variety for the pepper plantation and valorise their peppers so that they could compete with the peppers from protected geographical areas such as Kampot and Kep provinces |
