Introduction:

Nutmeg, Myristica fragrans Houtt. is a very important export agricultural crop which gives two products from a fruit namely, nutmeg seed and mace. A serious problem in the nutmeg industry is harvesting at immature stages for the market. This affects the yield and quality of nutmeg. Therefore this study was conducted as a laboratory experiment at the Export Agricultural Research station, Matale to identify the impact of stage of maturity on chemical changes of nutmeg.

Methodology:

Fruits were labelled at the time of initiation and harvested at one month intervals from the 4th month of fruit set upto 8 month of fruit maturity Chemical characteristics (oil, oleoresin contents and chemical constituents in mace and seed oils) were determined. For determination 90-100 fruits were harvested from 15 trees at each maturity stage.

Oil contents were determined by water distillation method. Oleoresin contents of mace and seed were determined by soxhlet extraction method. Mace and seed oil samples were analysed by Gas Liquid Chromatography (GLC). SHIMADZU GC – 9A Gas Chromatograph equipped with Flame Ionization (FI) detector and 10% Carbowax column 20 M WAW.

Results and Discussion:

Mean oil contents were 20% and 9% respectively in mace and seed at 4 months and significantly decreased with maturity (Figure 1). Essential oil content declined and fixed oil content increased in mace and seed with maturity. Seeds also contain higher amount of fixed oils than essential oils.
The highest oleoresin content in mace and seed were observed in 5 month old fruits and it decreased significantly with the maturity (Figure 2).


Figure 1: Changes in mean oil content Figure 2: Changes in mean oleoresin
with maturity content with maturity

Chemical analysis identified 10 major chemical constituents in mace and seed oils. Elemicin and myristicin were 2 major compounds which are toxic. The highest elemicin concentrations were 15.86% and 19.81% respectively in 4 month and 5 month mace and seed oils. The lowest were 8.9% and 10.81% in 8 month old mace and seed oils. The highest myristicin concentrations were 14.78% and 17.23% respectively in 4 month and 5 month mace and seed oils. The lowest concentrations were 7.72% and 10.54% in 8 month mace and seed oils. Changes in other chemical constituents did not show a clear pattern with maturity.

Conclusions:

The chemical characteristics in nutmeg and mace, gradually declines with maturity. The maximum values can be obtained at immature stages. If seed and mace are used for extraction of oils and oleoresins the best time period for harvesting is 4-5 month after fruit set.
The changes in chemical constituents in seed and mace oils vary with maturity. The most important compounds such as elemicin and myristicin content decreases with maturity. However further studies are required to determine and confirm there variations observed in this study.

References:

Anonymous., 2006. Nutmeg: Wikipedia, the free encyclopaedia [online]. Available from: http://en.wikipedia.org/wiki/Nutmeg/ [Accessed 15 November 2006]


Dorman, H.J, Damien, D, Stanley, G., March/April 2004. Chemical composition,
antimicrobial and in vitro antioxidant properties var. citriodora, Myristica fragrans,
Origanum vulgare spp. Hirtum, Pelargonium spp. And Thymus zygis oils: Journal of
essential oils research (JEOR) [online]. Available from:
www.findarticles.com/p/articles/mi_qa4091/is_200403/ai_n9367972/pg_2
[Accessed on 31 December 2006]