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Nutmeg: Post-harvest processing, potential applications
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Monday, 14 March, 2016, 08 : 00 AM [IST]
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R Mahendran
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fiogf49gjkf0d Nutmeg is one of the unique and costly spices in the world which yields two spices viz. nut and mace, each has its own aroma and taste. Its scientific name is Myristica fragans and it belongs to the family Myricaceae. Nutmeg and mace contain several chemical compounds that are known to have antioxidant, disease-preventing and health-promoting properties. Nutmeg also has many therapeutic applications in various traditional medicines for its anti-fungal, anti-depressant, digestive and carminative properties.
Kerala is blessed with tropical climate where nutmeg grows abundantly in the homesteads as an intercrop. Trissur and Ernakulam districts of Kerala state accounts for a major share of nutmeg production and marketing. India produces around 12,000 tonne of nutmeg per year, with Kerala accounting for more than 90 per cent. Out of the total production only 30 percent has been exported. Kerala contributes to 98 per cent of the country’s nutmeg exports.
Nutmeg has huge demand in the West. The possible earnings from Europe will be multifold if quality standards are maintained. Western countries reject the Indian produce because of the presence of Aflatoxin, a poison from Aspergillus fungus. The permissible levels of Aflatoxin is 10 ppb (parts per billion) in Europe, 20 ppb in the U.S., and 30 ppb in the Indian market. Exploiting the export opportunities to European countries is the best available option for profitable farming. Since guaranteeing highest quality alone can ensure enhanced export, systematic post-harvest handling of the produce is imperative.
Nutritional Composition
Nut contains fixed oil trimyristin and many essential volatile oils like myristicin, elemicin, eugenol and safrole. These oils give a sweet aromatic flavour to Nutmeg. The other volatile oils are tineme, camphene, dipentene, cineoil, linalool, sabinene, safrole, terpeniol. Fixed oil content in the nutmeg varies from 25-40% and that of mace varies from 20-30%. The nutritional composition of Mace and Nutmeg are given in Table - 1.
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| COMPOSITION | Mace per 100g | Nutmeg per 100g |
| USDA (Ground) | ASTA | USDA (Ground) | ASTA |
| Water | 8.17 | 4.5 | 6.23 | 4 |
| Food energy (Kcal) | 475 | 565 | 525 | 565 |
| Protein (g) | 6.71 | 8 | 5.84 | 7 |
| Fat (g) | 32.38 | 38.8 | 36.31 | 38.9 |
| Carbohydrates (g) | 50.51 | 46.1 | 49.29 | 47.3 |
| Ash (g) | 2.23 | 2.3 | 2.34 | 2 |
| Calcium (g) | 0.252 | 0.2 | 0.184 | 0.2 |
| Phosphorous (mg) | 110 | 110 | 213 | 200 |
| Sodium (mg) | 80 | 70 | 16 | 10 |
| Potassium (mg) | 463 | 500 | 350 | 400 |
| Iron (mg) | 13.9 | 11.3 | 3.04 | 2.2 |
| Thiamine (mg) | 0.312 | 0.37 | 0.346 | 0.36 |
| Riboflavin (mg) | 0.448 | 0.56 | 0.057 | 0.25 |
| Niacin (mg) | 1.35 | 1.2 | 1.299 | 9.4 |
| Vit-A | 80 | 80 | 10 | 10 |
Post-Harvest Processing
Market value of nutmeg mace is fixed based on the colour and nutritional composition. Even though post-harvest processing includes decortication, husk removal, separation of nut and mace, the most important processing with respect to colour of mace is drying. The harvest season of nutmeg coincides with heavy rain in Kerala. Hence, nuts should be dried within 24 hours of harvest and moisture level should not exceed 10 per cent.
Conventional Drying
Nutmeg and mace are dried separately as the moisture content of wet nutmeg is higher than that of mace and time required for drying is different. Mace takes four to five days for drying and nutmeg takes 10 to 12 days depending upon the intensity of the sunlight. In sun drying, the disadvantages are the products are exposed to direct sunlight, no uniformity in drying, presence of mould and infections (Aflatoxin) and contamination. In the processing of mace, the red coloured aril is removed from the nutmeg that it envelops and is flattened out and dried for 10 to 14 days under shade; its colour changes to pale yellow, orange, or tan. The mace is detached, flattened and dried in sun on mats for 3-5 days (Kissan Kerala).
Mechanical Drying
Mechanical drying is the solution to tide over the aflatoxin problem in nutmeg and mace. Mechanical and firewood-based driers can be used for drying both nutmeg and mace. In case of nutmeg drying, a temperature of 40°C may be adopted for about 6 to 8 hours for three days. Mace will take only 5 hours to dry at 40°C, but the colour will be yellowish which is not desirable. Maintenance of better quality, drying even in unfavourable climatic conditions at reduced drying time are the main advantages of mechanical drying.
Both nutmeg and mace need to be dried to a maximum moisture level of 10%. Artificial drying of nutmeg at 50°C, which takes 28 hours to reduce moisture content from 36% to 9% showed “case hardening” effect after drying. Hence slow drying is preferable in case of mechanical drying.
Pulsed Microwave Assisted Hot Air Drying of Mace
Since nutmeg is a spice of high commercial value due to its importance in many fields like food and medicine, the processing is very important. The drying of nutmeg in quick time with colour retention is still a challenge. Conventional methods of drying nutmeg is associated with many disadvantages. Normal sun drying or mechanical drying takes several hours to weeks for attaining the desired moisture content. Implementation of novel methods of drying and processing will lead to the production and processing of nutmeg with better quality attributes at a lesser cost.
Microwave-assisted convective hot air drying reduces drying time compared to convective drying and improves product quality compared to simple microwave drying. Pulsed microwave assisted hot air drying of mace takes two to three hours on an average. Preliminary post-harvest studies of nutmeg mace at Indian Institute of Crop Processing Technology in Thanjavur ensured that microwave drying helps to retain the red colour of the mace. Flavour component analysis of the raw, market, and microwave dried sample with best colour retention was done using GC-MS. Application of novel processing methods, such as pulsed microwave assisted hot air drying may be having the potential to solve this problem. More research should be done in this field to optimise a best drying method for nutmeg which will overcome all the disadvantages of the conventional drying systems.
Packaging And Storage
The dried mace can be well packed and stored in air tight containers or polybags which are approved for organic products with protection from sunlight so as to protect the red coloured pigment lycopene which is highly susceptible to oxidation in light. According to Agmark, nutmeg whole shall be packed in clean, sound and dry jute and cotton bags or in pouches made of food grade plastic. Nutmeg powder shall be packed in new, clean sound and dry containers made of tin, glass or in pouches made of laminated, extrusioned and metallised multilayer food grade plastic materials. The net weight of the nutmeg whole and nutmeg powder packed in a container shall be 25 gram, 50 gram, 100 gram, 500 gram, 1 kg and thereafter in multiples of 500 gram. Well packed nutmeg and mace can be stored normal temperatures in dry place. Moisture should be avoided so as to avoid mould attack and contamination with aflatoxin.
Potential Applications
- Nutmeg and mace are used to flavour drinks and foods such as cakes, sources, pickles and relishes.
- Used as an ingredient in ground spice mixtures like garam masala in Indian cuisine.
- Oil extraction, usually by hot manual pressing, produces nutmeg butter (also known as concrete or fixed oil or expressed oil). The butter is a highly aromatic, orange coloured fat which can then be processed into ointments and perfumes.
- Nutmeg jelly can be made from the pericarp.
- Nutmeg and mace oleoresins are extracted from the plant using organic solvents. They are produced for commercial flavourings and perfumes.
- Mace is typically used for seasoning seafood in West Indies.
- Ground nutmeg is mixed with petroleum jelly and warmed and used as balm (FAO, 1995).
- Medically, nutmeg is said to have stimulative, carminative and aphrodisiac properties.
(The author is assistant professor, IICPT (ministry of food processing industries, GoI), Pudukkottai Road, Thanjavur, Tamil Nadu. He can be contacted at mahendran@iicpt.edu.in)
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