Clove - Production and uses in food processing

Clove

1 Introduction The clove, Syzygium aromaticum (L.) Merrill et. Perry, belongs to the family Myrtaceae. The species is indigenous to certain volcanic islands of North Molucca, in the eastern part of Indonesia, where cultivated varieties and wild forms are found, that is Ternate, Tidore, Motir, Makian and Bacan, and the western part of Irian Jaya, where a considerable wild population occurs. The common synonyms are Caryophyllus aromatica L., Eugenia aromatica Kuntze, E. Caryophyllata Thunb. and E. Caryophyllus (Sprengel) Bullock & Harrison.

The tree is of medium size, fine, evergreen, reaching up to 20 m in height and varies in its canopy shape from cylindrical to pyramidal, depending on the variety. The tree can live up to 100 years and there are individual records of trees over 350 years old in Ternate. The trunk diameter can reach 30 cm in mature plants. The leaves are opposite, oblong obovate in shape, bright pinks in newly-formed leaves which turn to dark green when mature. The inflorescent is a terminal, with flowers borne in clusters, varying in flower numbers from 15 to 50, depending on variety and cultural practices. The flower is a hermaphrodite with a fleshy hypanthium that is surmounted by the sepals. The colour of unopened buds at the young stage is usually green, turning to flushed pink when they reach their full size, at which time they are ready for harvest. At that stage the stamens are still inside and covered by the petals which form the head of the dried cloves. Early picking or overripe buds will produce lower quality clove bud (Table 1). The tree is grown primarily for the unopened flower buds which are dried to produce the familiar spice of commerce.

The main products of clove are:

 whole or ground clove buds

 essential oils, produced from clove buds, stem and leaf

 clove oleoresins.

Whole or ground clove contains 15 to 20% by weight of volatile oil. The major com- ponents of clove bud oil are eugenol 7095%, eugenol acetate up to 17% and 1215% -

Table 1 The characteristics of clove bud from Zanzibar type at several stages of maturity

Bud maturity stage

Characteristic Fallen Undeveloped Fully Overripe flower bud developed bud

bud

Clove bud

Water content (% v/b) 3 5.0 8 6.5

Oil content (% v/b) 13.9 14.9 16.4 16.1

Ask content (%) 4.7 3.8 4.7 6.11

Fibre content (%) 11.8 10.8 8.5 13.3

Si content (%) 0.15 0.11 0.11 0.10

Clove bud oil

Total eugenol content %* 91.0 90.0 94.0 93.0

Eugenol content (%)** 54.2 55.6 68.5 72.2

Eugenol acetate content (%)** 34.4 36.5 22.0 9.4

Notes:

* Cassia method.

** By gas chromatography

Source: Balittro (1986) in Nurdjannah et al. (1977).

caryophyllene. For clove stem oil (the flower stem contains 57% oil by weight), the principal component is still eugenol 9095%, others being eugenol acetate and caryophyllene at lower amounts. Clove leaf oil (comprising up to 3% oil by weight) is a rather lower quality oil than the former and is less expensive, with the principal component being eugenol 8088%. The chemical structures of eugenol, eugenol acetate and -caryophyllene are illustrated in Fig. 1.

2 Production The world annual demand stays at 4 0005 000 t, with the USA consuming 1850 metric tonnes in 1990. Indonesia became the worlds largest producer of cloves in 1996 with total production 90 000 t, mostly consumed by the Indonesian kretek cigarette manufacturers, with exports of 9 000 t. Despite a rapid increase in Indonesian clove production, Zanzibar and Madagascar remain the main sources for international markets

Fig. 1 Chemical structures of eugenol, eugenol acetate and -carophyllene (Guenther 1950).

with 15 000 t in Madagascar and 6 000 t in Zanzibar (Verheij and Snijders 1999). Several thousand tonnes are produced by other Asian countries such as Sri Lanka, India and Malaysia, and smaller amounts by other African countries.

2.1 Dried clove bud Clove buds are harvested when they have reached their full size and the colour has turned reddish. After being harvested, the buds are separated from the stems, by hand or thresher machine. The thresher machine produced by the Research Institute for Spice and Medicinal Crops (RISMC), Indonesia, with 1 hp electric power could separate 76 kg fresh clove bud/hour. Immediately after separation, the buds are dried under the sun or using an artificial dryer. The colour and oil content of artificially dried cloves are not significantly different from sun dried (Hidayat and Nurdjannah 1992).

2.2 Storage Dried whole clove bud is usually packed in gunny bags and should be stored in a clean, dry room with good ventilation. This way of storing should not cause any significant changes except loss of sheen. Storage usually causes loss of oil by evaporation, the rate depending on the physical condition of the spice, mainly the moisture content of the products, temperature and relative humidity during storage (Purseglove et al. 1981). The essential oil and eugenol acetate content of whole clove decreased slightly after storing for six months, while eugenol content increased (Table 2). Loss of volatile oil during storage from whole clove is relatively slow compared to ground clove. Ground clove is more sensitive to high ambient temperature and moisture content which can change its stability and flavour value. Moisture content and temperature storage of ground clove should fall within 810%, and 1015%, respectively, with relative humidity 5565%. Poor storage conditions could cause more loss of volatile oil, mould growth and development of musty flavour and odour (Reineccius 1994).

Storage can also change the composition of carbon dioxide extracted clove bud. Reduction in caryophyllene content is 11% at 01sC, while at ambient temperature reduction of CO₂ extracted oil is higher (up to 18%) compared to commercially distilled oil (only up to 13%) (Gopalakhrisnan 1994). Moreover eugenol content increased after storage, whereas eugenol acetate remained fairly constant (Table 3).

Table 2 The changes of quality of dried clove bud during storage

Clove oil *

Storage duration Oil content of

Place of origin (months) clove bud (%) Eugenol content Eugenol acetate

(%) content (%)

Samalayu 0 17.22 78.30 7.97

6 16.48 80.25 6.80

Cigombong 0 17.04 77.56 11.20

6 14.10 78.10 8.78

* Analysis using gas chromatography.

Source: RISCM (1988).

Table 3 Changes in composition of CO₂ extracted clove bud oil during storage

Days of storage

Component Carbon dioxide extracted oil (%) Commercial distilled oil (%)

0 45 90 45 90 0 45 90

-cububene 1.5 1.1 1.3 1.2 1.2 0.7 0.7 0.6

-copaene 1.7 1.4 1.5 1.4 1.4 1.0 1.0 1.0 caryophyllene 16.6 15.0 14.7 15.1 13.6 10.8 10.5 9.4 eugenol 62.2 61.4 64.8 61.3 65.7 71.0 70.1 72.6 isoeugenol 0.9 0.9 0.8 0.8 0.6 0.6 0.6 0.5 nerolidol 1.2 1.2 1.2 1.2 1.2 0.4 1.2 1.1 eugenol acetate 14.3 13.8 13.6 14.6 13.6 1 13.4 3 farnesol 0.1 0.3 0.3 0.4 0.3 0.2 0.3 0.4

MVMC 0.2 0.1 0.3 0.1 0.2 0.1 0.1

LVMC 1.1 2.7 1.4 3.6 2.2 2.2 2.3 1.8

Source: Gopalakhrisnan (1994).

2.3 Ground clove

Ground clove is produced by milling and/or grinding of the dried clove buds. The process is usually conducted at low temperature (25s35sC) to prevent the loss of valuable volatile constituents during processing. Various techniques such as pre-chilling, water cooling or refrigeration of the grinding chambers have been developed to minimize the heat formed during processing. The results are powder with several degrees of fineness, depending on the nature of the spice, the ultimate application and the country. For extraction and distillation, coarsely ground material are accepted, while for direct use in food seasonings, a finer product is required. To obtain a very fine clove powder a two- step procedure is usually conducted; the buds are firstly reduced to a very coarse powder by passage through a slow speed breaker or cutter mill, then they are ground to the desired fineness. The United States requires finer powder than the United Kingdom.

2.4 Clove oil

Depending on the raw material, three kinds of oil are produced. The yield and quality of the oils are influenced by origin, variety, quality of raw materials, pre-treatment before distillation, distillation method, and post-distillation treatment. Clove buds and stem are comminuted before distillation to break the oil cell and widen the surface so that the oil can be released more easily from the cells. Clove leaf does not need pre-treatment as it is already in thin form. The materials are distilled using water and steam or steam distillation for between 8 and 24 hours. The highest yield derived from high quality clove bud (20% oil content) is 17%. In the United Kingdom, the finest oil is obtained by water distillation containing 8589% eugenol (Purseglove et al. 1981).

According to Gildemeister and Hoffimer, cited by Guenther (1950), the distillation of whole clove bud produces clove oil with high eugenol content, and specific gravity above

1.06. Comminuted clove buds produce clove oil with a slight lower eugenol content, and specific gravity lower than 1.06, because evaporation of the oil occurred during comminution. To prevent evaporation, distillation of comminuted material should be done immediately. Belcher (1965) stated that the eugenol content of the oil is dependent

on the time taken to distill the charge. Rapid distillation produces oil with eugenol content far higher than that normally found in commercial practice. Commercially CO₂ can be used to extract clove bud oil at subcritical condition using extraction conditions of

5080 bar pressure and temperature 0 to 10sC. This method is used as an alternative to steam distillation. The oil product has better characteristics, i.e. no solvent residue, no off notes, more top notes, more back notes, better solubility and concentration of aromatic components (Moyler 1977).

Clove stem oil of Indonesian clove, using water and steam distillation, yield 56% with eugenol content 9098%, variation in yield and eugenol content dependent on distillation time (Nurdjannah et al. 1990). According to Purseglove et al. (1981), in Zanzibar, distillation using stainless steel steam stills, which hold 680 kg of steam for 16 hours yielded 57% of almost water white oil. The colour darkens to yellow, sometimes violet-tinted, as the oil ages.

Clove leaf oil is usually produced from dried fallen leaf (in Indonesia) or fresh leaf after trimming the upper part of the clove tree (in Zanzibar). The oil may vary considerably in composition but eugenol content is usually 8088%, with low eugenyl acetate and high content of caryophyllene. Distillation of leaf in a 100 l still capacity for eight hours yielded 3.5% oil with total eugenol content 76.8% (water content 712%)

(Nurdjannah 1993).

2.5 Oleoresin

Clove oleoresin prepared by solvent extraction of clove bud, yielded about 1822%

oleoresin (9092% volatile components) using benzene and 2231% using alcohol

(Weiss 1997). Ground clove is extracted by suitable solvent(s) then evaporated or distilled to obtain oleoresin. According to Somaatmadja (1981) ethanol is a very safe solvent because it is not toxic. Oleoresin is an extremely concentrated product, containing all the flavouring ingredients soluble in the particular solvent used, so that much closer to the original clove odour and flavour (Heat 1973). Oleoresin can also be produced by supercritical CO₂ extraction, which is conducted at 200300 bar pressure at 5080sC. In situ fractionation is possible at 80100 bar and temperature 050sC. This could extract all the soluble components of oleoresin in a similar way to organic solvent extraction. The product is free of solvent residue(s), and can be further fractionated to produce oil. Solvent(s) extraction is, however, more cost effective than supercritical extraction

(Moyler 1977).

3 Main uses in food processing

The use of clove in whole or ground form is mainly for domestic culinary purposes and as a flavouring agent in the food industry. Clove can also be used as food. Whole cloves are seldom used in food processing as they are not a ready source of flavour. In some cases, whole clove is inserted into ham and baked apples, and for pickles. Usually only small amounts, perhaps as many as five whole cloves are used for pickling sauce blend, for meat such as corned beef and stews.

In the food industry, cloves are often used in the form of ground, extracted essential oils or oleoresin in a small amount because of their intense flavour. The advantages of using ground cloves is that they retain a considerable degree of their original stability during storage and are better able to withstand high-temperature processing (e.g. baking)

than many of the extracted processed products. Oleoresin is preferred over other clove products, because it contains both volatile essential oil as well as non-volatile resinous material, which accounts for the flavour mimicking the original ground spice. Oleoresin also has low risk of bacterial contamination.

Food products which use clove are mainly curry powder, sauces and baked foods. According to Farrell (1990) curry powder uses 2% (mild) to 3% (sweet) by weight of ground clove buds, meat sauces 0.37% clove ground or 0.111% clove oil, food seasonings such as Bologna seasoning A, B and C use 0.39% ground clove, 0.07% clove oil, and

0.45% clove oil, respectively. Chili sauce uses 0.025% oil, mustard 0.111% and 0.222% ground clove in Dijon and Dusseldorf, respectively, tomato ketchup uses 0.139% clove oil, whereas sausages (Sweet Italian) use 0.111% ground clove (Farrell 1990). The highest average maximum use level reported for cloves is 0.236% in condiments and relishes, and 0.06% clove stem oil and 0.078% clove bud oleoresin in alcoholic beverages

(Leung 1980). Clove leaf oil is not suitable for food flavouring because of its harsher note, and does

not reproduce the genuine clove flavour. It is mainly produced for production of eugenol and caryophyllene (Weiss 1997). Eugenols have flavour and antiseptic properties, therefore they have been used in soaps, detergents, toothpaste, perfumery and pharmaceutical products. Maximum use levels of bud and stem oils are 0.15% and

0.25% in soaps, 0.7% and 1.0% in perfumery. The major use of clove is, however, in the manufacture of kretek cigarettes in Indonesia which accounts for more than 90% of Indonesian clove production.

4 Functional properties Besides being a source of natural flavour, cloves also contain nutrients, such as proteins, vitamins, minerals, etc. The composition of nutrients in 100 g is illustrated in Table 4.

Table 4 Nutritional composition of clove, per 100 g

Composition USDA ASTA

(ground)

Water 6.86 5

Food energy (kcal) 323 430

Protein (g) 5.98 6.0

Fat (g) 20.06 14.5

Carbohydrate (g) 61.22 68.8

Ash (g) 5.88 5.0

Ca (g) 0.646 0.7

P (mg) 105 110

Na (mg) 243 250

K (mg) 1102 1200

Fe (mg) 8.68 9.5

Thiamin (mg) 0.115 0.11

Riboflavin (mg) 0.267 ND Niacin (mg) 1.458 1.5

Ascorbic acid (mg) 80.81 81

Vitamin A activities (RE) 53 53

Source: Tainter and Grenis (1993).

It appears that clove contains fat and carbohydrate in high concentration and has relatively high food energy.

Clove has long been used in traditional medicine, particularly to aid digestion, cure stomach disorders and in pain relief (Rosengarten 1969; Rumphuis 1741). Some of these therapeutic properties have been investigated, particularly the role of eugenol as an antiseptic. Clove oil has been used successfully for inflamed oral and pharyngeal mucous and for topical anesthesia in dentistry. RISMC has also successfully made balm with clove oil as the active ingredient which is used for soothing pain caused by rheumatism

(Nurdjannah et al. 1997). The oil is also a potent bactericide, nematicide and fungicide. It is believed that clove has antioxidant properties, which can neutralize free radicals associated with cancer. Antioxidant content varies depending on the type of clove product. Ground clove contains 1.8%, while in soluble fraction 1.4% (petroleum ether

soluble fraction) and 1.7% (alcohol soluble fraction).

Shahidi et al. (1995) reported that the antioxidant activity of ground clove, ginger, oregano, sage and thyme in meat lipids was concentration dependent, but clove was most effective, followed by sage and then rosemary. Ginger and thyme exerted the weakest effect.

Gallic acid and eugenol 110 have been identified as the major components in clove

(Eugenia caryophyllata) (Kramer 1985). It has been established that iso-eugenol 111, more rarely found in nature, exhibited higher antioxidative efficiency than eugenol during methyl oleate (Davcheva et al. 1992) and sunflower oil oxidation (Ivanov and Davchera 1992). Eugenol and iso-eugenol also have an inhibiting effect on the peroxidation of lecithin induced by the Fe²⁺-H₂O₂ system (Toda et al. 1994).

Table 5 Whole clove chemical and physical specification

Organization Suggested limit

Whole clove Ground clove

ASTA cleanliness specification:

Whole dead insect by count 4 Mammalian excreta, by mg/lb 5 Other excreta, by mg/lb 8.0 Mould, % by weight 1.00 Insect defiled/infested, % by weight 1.00 Extraneous, % by weight 1.00

A 5% allowance for unattached clove stems over and above the tolerance for other extraneous matters is permitted

FDA DALs:

Adulteration with stem by weight Ave. of 5%

Volatile oil 16. 0% min. 14.0% min. Moisture 8.0% max. 8.0%

Ash 5.0% max. 5.0% Acid insoluble ash 0.5% max. 0.5% Military specification (EE-S-635J) 5% or more by weight of stem Average bulk index (mg/100 g) 240

Source: Tainter and Grenis (1993).

Table 6 Specifications of oil of cloves

Sources of oil

Characteristics Flower bud Flower stem Leaf

Colour colourless to yellow to dark straw coloured pale yellow brown or very pale

Specific gravity (25s/25sC) 1.038 1.060 1.048 1.056 1.036 1.046

Optical rotation (20sC) 1s 30 to 0 1.5s to 0 0 to 2s Refractive index (20sC) 1.527 1.535 1.534 1.538 1.531 1.535

Solubility (70% ethanol) 2 vol 2 vol 2 vol

Total phenols (min. by volume) 85% 89 95 84 88

Source: Reineccius (1994).

5 Quality and regulatory issues The quality required for clove products depends on each country, for use in domestic or export and nature of the product. The ASTA (American Spice Trade Association) and FDA (Food and Drug Administration) recommendations for whole spice are described in Table 5. The specific requirement for clove ground is 12% for minimum quercitannic content, clove stem content maximum 5%, and volatile ether extract minimum 15%

(Reineccius 1994). For clove oil, specifications are illustrated in Table 6. For oleoresin, Salzer (1975) recommended determination of volatile oil content and subsequent assay of eugenol content as the measure of quality. There are specifications on the maximum residues limit in the foodstuff as a result of the use extraction solvents on the preparation of food flavourings from natural flavouring materials which should be applied to solvent extracted clove oleoresin (Table 7).

6 References

BELCHER E.F.M. (1965) The Distillation of Clove Oils. In Christian, Karl (ed.), Perfume and Essential Oil Review . pp 14851.

CROFTON, R.H. (1936) A Pageant of the Spice Islands. John Bale, Sans and Danielson Ltd., London.

Table 7 The maximum solvent residues limit in foodstuff

Solvent name Max. residue limits Solvent name Max. residue limits

(mg/kg) (mg/kg)

Diethyl ether 2 Ethyl methyl keton* 1

Hexane* 1 Dichloromethane 0.02

Methyl acetate 1 Methyl-propan-1-ol 1

Butan-1-ol 1 Propan-1-ol 1

Butan-2-ol 1 Cyclohexane 1

* Combined used is forbidden.

Source: Ziegler and Ziegler (1998).