Introduction:

Nutmeg, Myristica fragrans Houtt. is one of the most important export agricultural crops of Sri Lanka, which does not need intensive management practices for growth and development. Unlike other spice crops, nutmeg trees bear fruits throughout the year with two peak seasons in January to March and June to August. Thus growers could obtain incomes from two harvests soon after picking.

A serious problem in the nutmeg industry is harvesting at immature stages for the market. Due to improper identification of correct stage of maturity, availability of fruits throughout the year, the demand and the high price, farmers tend to harvest immature fruits. This affects the yield as well as the quality of the product. Hence, a research program was initiated at the Export Agricultural Research Station, Matale to identify maturity indices of nutmeg.

Methodology:

Fruits were labelled at the time of fruit initiation and harvested at one month intervals from the 1st month of fruit initiation upto 8 months maturity. Maturity indices (colour of the fruit rind, mace and seed, fresh weight of the whole fruit, rind, seed and mace, volume of the whole fruit, diameter of the whole fruit and moisture content of mace and seed) were determined. For determination 90-100 fruits were harvested from 15 trees at each maturity stage.

Colour of the fruit rind, mace and seed were visually observed and a colour code was prepared. Fresh weights were measured using an analytical balance. Volumes of the fruits were measured by immersing individual fruit in a beaker of water and determining the volume displaced. Diameter was measured using vernier calipers.


Results and Discussion:

Fresh weights of the whole fruit and rind increased significantly with maturity as 75-80% whole fruit is the rind. Seed weights increased significantly upto 5-51/2 months and gradually decreased because food reserves in the seeds are converted to essential and fixed oils with maturity (Figure 1).Mean moisture content of seeds and mace declined with maturity. Highest moisture contents were observed at immature stages in both mace and seed (Figure 2).

Figure 1: Changes in mean fresh weights Figure 2: Changes in mean moisture percent
with maturity with maturity

The volume of whole fruit increased significantly with maturity, the lowest volume was 1.014*10-5m3 observed at 1month old fruits and the highest volume was 7.65*10-5 m3 observed at 8 month old fruits. Fruit volume significantly increased with maturity because the fruit size is increased with maturity.

Diameter of the whole fruits was enhanced significantly with maturity upto the fully mature stage. The lowest diameter was 26mm in 1 month old fruits and the highest diameter was 56mm in 8 month old fruits.

Conclusions:

The study illustrates that the most suitable time period is the fully mature stage (8 months) to obtain the best quality product and the highest income.

References:

Anonymous., 2006. Nutmeg: Wikipedia, the free encyclopaedia [online]. Available from: http://en.wikipedia.org/wiki/Nutmeg/ [Accessed 15 November 2006] Bavappa, K.V and Ruettimann, R.A., 2002. Nutmeg: Cultivation and processing, Technical bulletin- 2. Department of Export Agriculture, Matale, Sri Lanka

Purseglove, J.W.. Brown, E.G., Green, C.L., Robbin, S.R.J., 1981. Spice Vol. 1:
Nutmeg and mace. London: Longman.