1501

2: Edible fruits and nuts

Diospyros kaki L.f.

Suppl. pl.: 439 (1781).

EBENACEAE

2n = 90

Oriental persimmon, Chinese or Japanese persimmon, kaki (En). Plaqueminier, kaki, raquemine (Fr). Indonesia: kesemek, buah kaki. Malaysia: buah kaki, buah samak. Cambodia: tonloëp. Thailand: phlap chin (central). Vietnam: thi, hông. The name 'kaki' is of Japanese origin.

The oriental persimmon is one of the classical fruits of China, from where it was introduced in ancient times to Japan. China and Japan remain the main areas of commercial cultivation but smaller centres have developed in Italy, Israel, Brazil and United States (California). In South-East Asia it is grown on a limited scale in Java, Sumatra, Malaysia and northern Thailand; the material — astringent types — was introduced from China in recent times.

The soft ripe fruits, which have lost their astringency after harvest, can be eaten fresh or the pulp can be processed into puree, ice-cream, jam, jelly, etc. Some astringent cultivars can be made into an excellent dried product, not unlike dried figs.
Kaki-tannin is used for painting cloth or paper to make them durable; the main application now is in some kinds of handicraft. Kaki-tannin is also used as a proteolytic agent in the brewing of Japanese rice wine and medicinally to reduce high blood pressure.

There is little information on areas and production. In 1986 Japan's crop was 291 000 t from a total area of 27 000 ha. There is much interest in the crop and commercial production is spreading to New Zealand and Australia. International trade is also expanding; fruit from Israel's 1500 ha of oriental persimmon is finding its way to Europe, where it is sold as 'Sharon fruit'.
In South-East Asia the area north of Lake Toba in Sumatra used to ship as much as 1500 t per year to Singapore, a trade that is facing increasing competition from better-quality fruit supplied by other countries. Production in eastern and western Java, the Cameron Highlands in Malaysia, and northern Thailand is of only local importance.

Astringency is due to the presence of a soluble form of tannin, 'kaki-tannin', in specialized tannin cells distributed throughout the fruit tissues. When astringent fruits are deep-frozen at —20°C and thawed, the cells are ruptured. The released tannin binds itself to proteins in the fruit, thereby becoming de-activated. Such fruits are soft and have a fine smooth texture. When unripe fruits are eaten, the tannin cells are ruptured and the released tannin binds itself to the protein in the tissues of the mouth, producing a dry unpleasant sensation. The reaction is like the tanning of animal skins to make leather. It is not clear how the tannin is de-activated under natural or artificial ripening, but the coagulation of the contents of the tannin cells to insoluble form is regarded as the most important step.
Nearly the whole fruit is edible, but the skin may remain astringent. Per 100 g edible portion the fruit contains approximately: water 80 g, protein 0.7 g, fat 0.4 g and carbohydrates 19.6 g, mainly fructose and glucose. The fruit is rich in potassium and vitamin A. The energy value is 320 kJ per 100 g.

A slow-growing, shrubby, dioecious (sometimes monoecious), deciduous tree, to 15 m tall, with a short crooked trunk and a profusely branched crown. Leaves distichous, alternate, short-petioled; petiole up to 3 cm long; blade ovate-orbicular to elliptic, 5—25 cm x 2.5—15 cm, apex obtuse or rounded and short acuminate, coriaceous, shiny dark green. Inflorescences consisting either of small 3—5-flowered cymes of male flowers or of solitary female flowers; in some cultivars the central flower of an otherwise male cluster is hermaphrodite; flowers 4-merous, greenish-yellow; male flowers with corolla twice as long as the calyx, 14—24 stamens inserted in pairs on the base of the corolla; female flowers stalked and pendulous, with two oblong-lanceolate foliaceous green bracts, up to 2.5 cm x 1 cm, a campanulate 4-lobed calyx up to 4 cm x 6 cm and a tubular-campanulate 4-lobed corolla, 8 or 16 staminodes and a 8- or 10-celled ovary with 1 ovule per cell. Fruit a depressed, obtusely quadrangular-globose berry, resembling a tomato and even more variable in size, yellowish-green to red, with enlarged persisting calyx; mesocarp thick, edible, in which thin jackets of edible endocarp are embedded around each seed or locule; seeds 0—10, ovoid-oblong, flattened on one side.

Oriental persimmon has an annual cycle of shoot growth, flowering, fruiting and leaf fall, even in equable climates in the tropics. Shoots emerge from resting buds formed in the previous cycle. They extend for 4—6 weeks and flower buds appear, usually in the axils of 2—4 basal leaves on the shoot. The terminal shoot meristem aborts and by the time the leaves mature the flowers open. At the same time the formation of leaf primordia in the axillary buds is stepped up; it slows down again halfway through the growing season when flower initiation begins in the axils of the basal primordia in the bud. Normally only the 2 or 3 uppermost buds on a shoot contain flower initials. In vigorously growing trees with few fruits there may be a second flush of shoot growth from the uppermost leaf axil; in this way potential flowering shoots for the next cycle are lost. At about the time of fruit ripening — some 7 months after bloom — the leaves are shed and the trees remain leafless for several months.
The main cultivars bear only male-sterile flowers. Parthenocarpic fruit set is common, but pollination is often desirable to reduce early fruit drop and to improve fruit quality, especially for non-astringent cultivars. Hence the choice of cultivars — and where necessary, pollinators — is complex and testing of cultivars introduced in South-East Asia should include study of floral biology to explain success or failure.
In the subtropics the trees flower in spring and the fruit ripens in autumn. In eastern Java the trees come into bloom in November—December, that is early in the rainy season and the harvest is in June—July. In the Cameron Highlands various cultivars are grown which flower between January and May and the fruits are available between August and December. Dwarf cultivars come into bearing 2—3 years after planting; more vigorous cultivars take 2 more years to produce an appreciable crop. There is a tendency towards biennial bearing, aggravated by heavy drop of fruitlets in some years, in South-East Asia in particular caused by excessive rainfall during fruit set.
It has been found that the size of the fruit is influenced strongly by the size of the calyx. If the calyx is artificially reduced while the fruit is small, the growth of the fruit will be reduced. The calyx has many stomata, unlike the fruit skin, and acts as the respiratory organ of the fruit.

The progenitor of the oriental persimmon is believed to be Diospyros roxburghii Carriere, a species of the subtropical forest in Assam, Burma, Yunnan, Thailand and Indo-China. Diospyros roxburghii is more hairy, the fruit in particular, and it is diploid (2n = 30), whereas Diospyros kaki is hexaploid (2n = 90). Diospyros roxburghii has the characteristic Diospyros architecture, in which there is a dominant leader with branches arranged in pseudo-whorls (Massart's architectural model). The branching of Diospyros kaki is much more diffuse, probably partly a result of vegetative propagation.
Over 1000 oriental persimmon cultivars have been distinguished in China and Japan. They vary greatly in tree vigour and habit and in all fruit attributes: shape, size, colour, taste, etc. They are usually classified into astringent (e.g. 'Hachiya') and non-astringent (e.g. 'Fuyu', the leading cv.) cultivars. An intermediate group is formed by cultivars which remain astringent when seedless and lose their astringency before ripening, if they contain sufficient seeds. Cultivars with non-astringent fruit have been selected in Japan. Such fruit loses astringency while it ripens on the tree and can be eaten when still firm. These cultivars have the lion's share of the fresh fruit market in the subtropics, also because the shelf life is much longer. The flavour is mild, sweet and melon-like. However, non-astringent cultivars have not yet proved themselves in the tropics.
In Indonesia trees with female flowers are grown which bear seedless astringent fruit; the stock is believed to have been introduced from China a century ago. Other cultivars introduced in the Garut area (Java) in the 1930s, have not thrived. Cultivars in Malaysia are astringent and seeded; the most common are trees with 3-flowered cymes, the terminal flower being hermaphrodite, the other two male.

Although of subtropical origin, oriental persimmon is adaptable to a range of warm temperate climates, including those in tropical highlands. Experience in South-East Asia indicates that a prominent seasonal climate is not required. Cultivation is successful in the highlands above 1000 m; but there are examples of bearing trees in the lowlands, e.g. in Kuching (Sarawak). Sheltered sites are important to prevent wind damaging the tender young foliage and to prevent blemishes occurring on the fruit. The trees tolerate a wide range of soils, but it is much easier to sustain high yields on well-drained deep soils that are not too heavy. The recommended pH is between 5.5—6.5.

Propagation in Indonesia and Malaysia is normally by separation of root suckers which are several years old. Plants produced from seed tend to be whippy and weakly branched. In the subtropics propagation is normally by grafting mature buds onto seedling stock. Cuttings are very difficult to root.
Proper timing of propagation is of utmost importance, for if the natural shoot growth period is missed growth may stagnate for years, a peculiar problem in oriental persimmon. The same applies to the timing of transplanting; field planting is done when the trees are leafless, taking care to keep the roots intact. Spacing depends on the vigour of the cultivar; recommendations range from 6 m x 4.5 m (370 trees/ha) to 5 m x 2.5 m (800 trees/ha). In the tropics growth tends to be more vigorous and wider spacings are common.

Disbudding and flower thinning are recommended to suppress the tendency towards biennial bearing. In addition fruitlets should be thinned to one or at the most two per shoot to obtain quality fruit. The main application of manure or fertilizer is 1—2 months before harvest. Excess nitrogen should be avoided, as it induces more vigour, worsens early fruit drop, and makes fruit grow so fast that a cavity forms beneath the calyx.

Numerous diseases and pests occur in the major production centres, but their importance in South-East Asia has not been confirmed. Black leaf-spots, pink disease (Corticium salmonicolor), leaf rollers, leaf-eating beetles and — in the dry season — various aphids have been found on the trees in Java.

The fruit is harvested by clipping it from the tree, so that the calyx remains attached to the fruit. Immature fruit fails to develop flavour and sweetness, and in Japan colour charts are used to ensure that each cultivar is picked when the skin colour is optimal. Most cultivars can be kept in cold stores at —1°C to +1°C for 2—4 months.

Yields of 20—50 t/ha per year are reported from the main centres for mature, approximately 8-year-old orchards, the lower yields applying to non-astringent cultivars. Observations on 50 trees in western Java from 1931—1934 established a mean annual yield of 220 fruit per tree.

To overcome astringency and to maintain a succulent crispy texture, fruits are harvested semi-ripe in Indonesia and soaked in slaked lime for 24 hours. Fruits so treated are sweet and firm but have patches of powdery white lime on the skin. Other methods of removing astringency include treating the harvested semi-ripe fruits in sealed rooms or containers with ethyl alcohol or carbon dioxide. The treatments are exacting, cultivar-specific and time-consuming; the results depend on the uniformity of the fruit. The fruits may also be dropped into boiling water and allowed to soak and cool overnight. Ethylene treatment also accelerates ripening.
Astringency also disappears when the fruit is dried. Drying is used to prepare an excellent fig-like product. The fruit is peeled and strung up by the stalks to dry in the sun or in rooms kept at 35°C. The semi-dry fruits are flattened gradually in a wooden press and dried again. The final product is white because sugar crystallizes on the surface. In Indonesia ripe fruits are sometimes steamed soft and then pressed flat and dried into 'red figs'.

In South-East Asia there is an interest in testing a wide range of cultivars, especially non-astringent ones, and the Malaysian Agriculture Research and Development Institute (MARDI) has imported many plants for this purpose. Other germplasm collections are present in e.g. China (Fruit Breeding Institute, Mei County, Shensi Province), Japan (Akitsu Branch Fruit Tree Research Station, Akitsu, Hiroshima) and Thailand (Department of Horticulture, Kasetsart University, Bangkok).

Oriental persimmon is one of the best fruit trees for tropical highlands. It may also be of value for the conservation of montane soils. So far most fruit has been sold locally. Expansion of the market would require fruit of better quality; this might be achieved through more intensive husbandry, harvesting at the right moment and more attention to post-harvest handling, including the treatments to remove astringency. There are also prospects for extending the range of cultivars to include non-astringent ones.

George, A.P. & Nissen, R.J., 1985. The persimmon as a subtropical fruit crop. Queensland Agricultural Journal 111(3): 133—140.
Kitagawa, H. & Glucina, P.G., 1984. Persimmon culture in New Zealand. DSIR Information Series No 159. 74 pp.
Namikawa, I. & Higashi, M., 1928. On the number of chromosomes in Diospyros kaki and D. lotus. Botanical Magazine (Tokyo) 42: 436—438.
Ng, F.S.P., 1978. Diospyros roxburghii and the origin of Diospyros kaki. Malaysian Forester 41: 43—50.
Somego, M., 1978. Chromosome number of Diospyros roxburghii. Malaysian Forester 41: 51—52.
Terra, G.J.A., 1935/1936. De stand van de cultuur van kesemek in het regentschap Garoet [The condition of the culture of Diospyros kaki L.f. in the regency of Garut (Java)]. (Dutch, English summary). Landbouw 11(7,8): 326—336.

F.S.P. Ng

Ng, F.S.P., 1991. Diospyros kaki L.f.. In: Verheij, E.W.M. and Coronel, R.E. (Editors): Plant Resources of South-East Asia No 2: Edible fruits and nuts. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea