Abstract
Harvesting makhwaen (Zanthoxylum myriacanthum Wall. ex Hook. f) fruits at the appropriate maturity is the key to ensure that the essential oil quality meets the need of consumers. In common practice, the fruits are usually harvested when their pericarps start to open and fruits are greenish-red in colour depending on the judgment of the farmers. This leads to inconsistencies in the essential oil quality. This research aims at characterising the aromatic profiles of makhwaen essential oil thereby for consumers to choose the quality that best fits their need and eventually identify the optimum harvesting index of the fruits. The effects of maturity states viz. 15, 36, 45 and 60 (MK15-60) days after fruiting on chemical and sensorial quality of the essential oil was evaluated. Fruit sizes ranged from ~3.3–3.7 mm and fruits appeared to dry initially when they reached 45 days. Essential oils were extracted from these fruits after they had been oven dried (60 °C) to the same moisture content, about 10%. The chemical profiles of the essential oil were different. L-limonene and sabinene were evaluated as key components for good quality essential oil and they were found to be higher in MK45 and MK60 (max = 139.04 µg·mL−1 and max = 146.27 respectively). NIR spectral patterns of pure extracted oil for every different harvesting time (of every different harvesting time of MK60 and MK36) were similar. Sensorial descriptive analysis by semi-trained panellists defined six terms for characteristics (woody, citrus, herb, sweet, pine and spice). The panels provided the highest rating score (15 numeric scale) of citrus and pine scents at MK45, while sweet and woody aromas were the highest at MK15. The spice scent was maximum when the fruits were harvested at 36 days after fruiting. From this study we suggest that the optimum harvesting index for the distinctive aroma of essential oil ought to be at late harvesting (45–60 days after fruiting). The findings contribute to our understanding of the harvesting maturity, which can also provide significant benefit for the perfumery industry, i.e., the optimum harvesting stage that imparts the essential oil with highest quality.
Highlights
The Zanthoxylum genus of the Rutaceae family comprises ~250 plant species [1]
Nine species of Zanthoxylum are found in Thailand and four of them, viz. Z. acanthopodium, Z. armatum, Zanthoxylum rhetsa (Roxb.) DC. and
The information we provide can be used as a guideline harvesting index for high quality raw material for the perfumery industry
Summary
The Zanthoxylum genus of the Rutaceae family comprises ~250 plant species [1]. These aromatic crops can be found in tropical and temperate regions [2]. In Thailand, most Zanthoxylum species are known for uses as spices, and to cure many ailments. Nine species of Zanthoxylum are found in Thailand and four of them, viz. Z_acanthopodium, Z. armatum, Zanthoxylum rhetsa (Roxb.) DC. Z. myriacanthum is locally known in Northern Thai as makhwaen and its fruits yield essential oils as high as 4% dry weight [5,6]. The major volatile component of makhwaen essential oil is L-limonene, comprising as high as ~60% [8,9]. The other constituents are α-pinene (6.49%), β-myrcene (3.87%)
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