It is indeed not an easy task for the legislator to intervene in the consumption of a liquid derived from a natural juice for which he gave permission to be harvested and which spontaneously has changed its properties within a matter of hours. The fact that the natural (sweet) and the fermented juice in Arabic are known under the same name, lagbi or lagmi, does not simplify the matter either.

It is generally agreed that palm tapping can have, potentially, undesirable side effects and the safest way to prevent these from happening is to prohibit it altogether, a measure that more than often has been applied.

However if one looks at the thousands of tons of sugar produced from the Wild date palm (Phoenix Sylvestris), the Coconut palm, Palmyra, the Sago (Caryota Urens) and the Nipa palm, the question is raised whether sugar from date palm sap would under certain circumstances not be profitable. Or put in another way: the date palm offers its "produce" in two ways, as fruits and, alternatively, as a sugar (sucrose) containing sap; does a choice exist?

Compared with the Indian experience where tapping the Wild date palm is a very well developed cottage industry, two points emerge immediately: the Wild date palm does not offer an alternative product because its fruits are not attractive for human consumption hence it is not a choice anymore; secondly palm tapping has developed in India in a much less drastic way. It is done annually and it does not remove the whole crown of leaves, thus leaving a great part of the productive capacity of the palm. To illustrate the differences further both methods of tapping are briefly described (Fig. 99).

Table 26
Palm sap yields

Together with the (scarce) literature references (169, 138, 363) major conclusions on yield for the varieties recognized as the more adapted for tapping are that:

i. total yield in litres for one tapping period may easily reach 500 l but higher yields are known (1,212 l in one particular case, (138))

ii. a daily yield of 8-10 l is an acceptable range as an overall average

iii. the average solids contents of the juice is around 10%, with higher levels possible but these are mainly due to lower moisture excretion

iv. the daily yield of solid matter (mainly sugar) turns out to be rather constant for the different palms and amounts to about 1 kg/day

Apart from quantitative appraisal there is also a qualitative appreciation of the juice and there are varietal preferences.

The tapping operation eventually will leave a scar on the trunk in the form of a circular indent (Fig. 100). By the number of those rings one can tell how many times a palm has been tapped, normally not more than once every 5 years. A number of six rings is seldomly seen, but three and four is rather common. In this respect it should not be forgotten that each ring adds another relatively weak spot in the trunk and the risk for the tapper proportionally increases.

After tapping is finished in March the cut surface will dry out and heal but leaving an indent in the trunk. The next cut will be made on the other side of the trunk (180° ) a little higher because the palm has grown, and leaving again a similar scar. Eventually after several years of tapping the trunk will assume a zig-zag configuration (Fig. 101).

Yields of juice are, because of the reduced exposed surface area, much less than for the method described before, but the palms can be tapped every year, which can go on for an average of 25 years, though higher productive life spans have been recorded (32).

Together with some yield figures from literature (32) for the Wild date palm and the measured results from the earlier referred to tests between local and Indian tapping (61) some indicative figures on yields are given in Table 27.

Table 27
Yields of palm sap (Indian and Local Method)

With due appreciation for the possible variations caused by varietal differences, height/age of the palms and length of the tapping period, certain tendencies can be discovered from these yield figures:

i. the yields of juice and solid matter by the Indian method on the date palm (Ph. Dactilyfera) are consistently higher than for the Wild date palm (Ph. Sylvestris).

ii. the daily and seasonal yields by the local method are higher than for the Indian method, but taking into consideration that by the local method the palm will not produce sap or dates for 2 years after tapping and in India the palms are tapped every year, the picture looks different. If indeed Ph. Dactilyfera could be tapped every year by the Indian method with the same result, most likely the total yield over three years would be higher than for the local method. This belief is reinforced by the fact that at least part of the crown leaves is left on and the palm's photosynthetic capacity is only partially impaired in contrast to the local method.

iii. in consequence of the lower daily yield but with the same if not more daily work required to harvest the palm sap for the Indian method, the labour hours involved per unit sap harvested is definitely higher.

With the production of sugar from palm sap as an alternative to the date crop in mind, the process of the different forms of sugar as practised in India as a cottage industry, will be briefly described. It is of vital importance to start work with a sound raw material, which involves a continuous fight against infection and multiplication of yeast. A freshly harvested sap will for the greater part consist of sucrose (say around 10%), minimal invert sugar, say less than 0.5% and small amounts of protein, gums, and minerals. To keep it in this form tools and pots should be kept clean, stagnant juice on the palm should be avoided and collected early in the morning. Time between collection and processing of the juice should be kept to a minimum. Artificial means to keep down the yeast are smoking the collecting pots by putting them head down on smouldering leaves before being used or by adding a small amount of quick lime to the pots. The latter method is definitely more effective to reduce the sugar inversion but for good quality gur (jaggery) production the lime has to be removed again by precipitation and filtering during processing (Fig. 99j, k, l).

Four main sugar products are made from palm sap:

i. jaggery (gur), the crystallized whole (sometimes clarified) sap
ii. crystalline sugar with remaining molasses
iii. sugar-candy, large sugar cyrstals
iv. sugar syrup

In the most traditional method the juice is boiled down in earthenware pans filling in the holes of an arched clay oven (Fig. 99n). Fuel, e.g. palm leaves, is fed on one side of the stove and the smoke leaves from another hole or primitive chimney. The end point of boiling which may take a couple of hours is different for each of the intended products and usually recognized by the type of bubble which appears during boiling. In the case of jaggery making a separately prepared starter to accelerate crystallization is mixed in the boiling liquid just before pouring into a mould and left to cool and crystallize. Removed from the moulds jaggery presents itself as a light to dark brown crystallized block. The less invert sugar was present in the raw juice the better quality jaggery results. As an average the outturn of jaggery is 10-15% of the weight of the raw juice (32).

A typical composition of jaggery is:

Table 28
Composition of jaggery

Strong promotional campaigns to encourage cottage industries in India have helped much to modernize jaggery making.

The use of lime is now common, which during processing is neutralized with phosphoric acid with P_H indicator paper as a guide. The precipitated calcium phosphate is filtered off. In determining the end point of boiling also use is made of refractometers. Improved stoves have resulted in reduced fuel use and better controllable fires. Though remaining a cottage industry performed with simple means the qualitative aspects have greatly improved.

On the basis of the foregoing the question posed at the beginning of this Chapter (d) whether sugar from palm sap could become an alternative to a date crop, has become a little more but not fully answerable.

Physiologically it would seem that in sugar value the yield in the form of dates or in the form of sugar from sap are about equal, also in terms of the total productive lifespan of the palm (following the Indian method). Production-wise it would appear that it requires more labour hours and a longer annual involvement to produce one unit of sugar from sap than from dates. An economical evaluation therefore depends on the appreciation, organoleptically or monetary, attributed to the different products and the effect of their diversity and applicability. Each situation will have its own conditions and an on-the-spot feasibility is necessary. Technically however the date palm offers the possibility of alternative sugar production.

Be it, that the date palm historically has been so closely interknit in the farmer's life and environment, or that the "Tree of Life" with its single head and trunk and division into male and female sexes with a corresponding reproductive system, was felt to resemble that of humans, the fact has transpired that the date palm has always had an aura of mystique around it, which at times devleoped into a palm cult. In Assyrian times, for instance, the palm was worshipped and depicted frequently in decorative art and for the embellishment has been witnessed in different times and places and, perhaps less pronounced, skill persists to date in the traditional date producing countries.

This esteem and adulation has probably also contributed to a sometimes overestimated belief in the medicinal powers of dates and other parts of the palm. There are many references to this effect in literature and if not for a desire of the search for alternative medicines, it is interesting (and sometimes amusing) to have a closer look at what benefit people obtained or thought to obtain from the different cures based on date palm products. In the foregoing text, in passing, mention has already been made of the depurative properties attributed to the terminal bud by Saharian palm growers (363) or the use of pollen to enhance fertility in (ancient) Egypt (128). Medically, dates were recommended in mouth washes (an application most likely frowned upon by a present-day dentist); as a purgative or in gynaecologically related interventions (128). Dates formed part of various ointments, bandages and opthalmic prescriptions and Plinius reports: "dates are applied with quinces, wax and saffran to the stomach, bladder, belly and intestines. They heal bruises" (128).

A notable Sheikh in the 16th Century elaborates: "dates fortify the body, enrich the blood, cure pains in the back, invigorate the loins whey they are atrophied and when boiled with milk they cut short fever and ague" (445). And from the same source: "the sap of leaves is a remedy for nervousness, kidney trouble and putrid wounds and calms the effervescence of the blood. Burnt seeds are made in an ointment for ulcers or a collyrium that produce long eyelashes". And this sampling of medicinal use of date palm products could not end without reference to the invigorating power bestowed on man when consuming male flowers and male spathe (445, 341). Though the possible responsible agents to this effect have not been isolated scientifically, one wonders whether the chewing of spathe (Ch. V 1.c.i.) is practised for its flavour only.

A chapter on the traditional uses of date palm products could not close without making mention (again) of an abstract but ever so real attribute of the date palm: giving shade and protection from wind, thus creating a micro-climate in which the harsh conditions of a hot and dry climate are tempered to make living conditions somewhat more sustainable. In the traditional date orchards especially in the oasis the density of palms is so great as to form an almost closed canopy.Extreme density and irregular stands of palms, however, diminish the opportunities for growing secondary crops and the introduction of mechanization in date palm cultivation.

Closely related to being a provider of shade is the ornamental value of the palm and indeed in several date producing countries where date production has declined as a consequence of a fast economic growth, the date palms are maintained and planted also as an ornamental tree.

5.2 Palm products development

In the previous section it has been demonstrated that, historically, palm parts were extensively used but that there has been an overall decline in their application due to alternative materials becoming available which proved better or more convenient for the intended purpose.

In consequence of this trend there have been several attempts to find new outlets for the annual crop of leaves and empty bunches that are obligatory by-products of date production. It concerns mainly ligno-cellulosic materials with scarce protein and fat content but a high ash content. Their potential use has mainly concentrated on animal feed, soil amendments and board where it concerns use of the whole material. Another field of attention has been extraction of components to be used as industrial feedstock such as cellulose and hemicellulose but also the search for minor constituents which might have an economic importance.

Lactating dairy cows divided in two groups were fed ad lib on alfalfa hay plus a rationed 16% CP (crude protein) concentrate in the first group and an ad lib mixture of NaOH treated date palm leaves (40%), wheat bran (30%), broken wheat residues (15%) and poultry manure (15%) (DPLS), plus the same (rationed) 16% CP concentrate, in the second group. Although the mean daily and total milk yields were consistently lower in the DPLS fed group than for the hay-fed group the fact that 40% of the ration was composed of an unused but plentiful resource, prompted the conclusion that the lower milk yield may be economically justified (381). It is to be noted, however, that date leaves were treated with NaOH and supplemented with wheat bran, wheat residues and poultry manure, which all represent additional cost factors.

In an evaluation in vitro of the non-fruit components of the date palm (frond bases, midrib, leaflets, spikelets, fruit stalks, spathes) for feed value it was concluded that all components have a certain but limited value for ruminant feeding. Digestibility values were highest, though still modest, for spathes and spikelets (98).

There seems therefore to be some scope, albeit very modest, for the use of palm by-products in animal feed.

Whilst the use of date fibre and date leaflets as a mulch in a maize growing experiment in comparison with transparent plastic, black plastic and straw, was negative both in time to reach maturity and in yield (267), there seems to be some scope to use shredded palm leaves (SPD) as a potting medium in greenhouse cultivation of certain vegetables. A good horticultural substrate must provide good drainage, aeration, and have a high cation exchange and water holding capacity. Shredded date palm leaflets (about 8 cms long and less than 3 mm in width) were combined in different proportions of either/and peat moss, sand, perlite and vermiculite and tested as substrate for tomatoes and cucumbers, in otherwise similar growth conditions.

Though peatmoss combinations came out as the medium with the highest yield for both tomato and cucumber attributed to its good cation exchange capacity, shredded date palm leaves in combination with sand, perlite and vermiculite gave good result in tomato yield (1.82 kg/plant) versus 2.13 kg/plant in a similar combination based on peatmoss (3).

Experimental work (164) and feasibility studies (574) have led to the establishment of at least one board factory based on palm leaves. It is located in Iraq which alternatively uses also reeds as raw material. Practically all ligno-cellulosic waste materials can be turned into board by disintegration, pressing and addition of binders, usually synthetic resins. The ultimate economic feasibility depends on the raw material and production costs and the quality of the board expressed as density (kg/m³), % moisture, bending -, tension -, and impact strength, and swelling %-age upon soaking. An important cost factor is the amount of resin to be added, which is inversely related to the lignin content (which under high pressure and temperature liquifies and starts to act as a binder). Unfortunately palm wastes have a tendency to have a lower cellulose and lignin content than wood and a higher than usual amount of water soluble substances which tend to increase the water absorption and swelling. One machinery supplier rated the fruit stalks best for board making, followed by the midribs. Palm sheath fibre and the trunk are considered unsuitable (574).

General conclusion is that board making from midribs and fruit stalks is possible with satisfactory results but that cost of production because of the intensive necessary disintegration (accompanied by much dust formation) and more than usual resin requirements, tends to be higher than for wood boards. Tests on making gypsum fibreboard were not entirely satisfactory with the process needing further perfection (164).

Major contenders for extraction of industrial rawstock are: cellulose, pentosans (hemicellulose) and lignin, the main three components of the fibrous parts of the date palm. For a general impression of their importance the composition of the various parts of the palm are given as percentage ranges (adapted from 96):

Table 29
Composition of fibrous date palm parts

* on dry weight basis
** Furfural is a derivative of pentosans (by hydrolysis and subsequent dehydration). Pentosans form the major part of the difference between holocellulose and cellulose and are often indicated as hemicellulose. (Furfural yield is about 1/3 of the pentosan content, e.g. 10 furfural out of 30-32 pentosans in corn cobs (234), which make the furfural yield figures in above table seem somewhat on the high side). Actually in another study (92) the pure furfural yield from midribs ranged from 6.3-10.2 (average 9%).

From this table it can be concluded that:

- for cellulose preference goes to midrib, fruitstalk and spathes as the raw material

- for lignin the frond bases and leaflets and

- for furfural midribs, fruit stalk, frond bases and spikelets are quoted the best source (234)

For lignin extraction further references can be found in (97, 479, 480, 266, 481).

Cellulose extraction for paper making is technically feasible: the midribs yield a pulp easily bleachable and of good quality, whilst the pulp derived from the leaflets lends itself better to kraft paper or corrugating medium (152). See also (485, 184, 68, 19).

All three industrial rawstocks: cellulose, furfural, and lignin have in common that they have to be produced on a large scale to be competitive on a worldwide basis. In the case of palm waste products this may create problems of supply because, though they are produced in large quantities, they are quite dispersed and transport costs for this bulky raw material may become a limiting factor.

Various other attempts to make use of palm by-products are reported in technical literature, some of which are more of an academic nature than having a clear practical objective:

i. date palm fibre was analyzed for length, strength and crimp and it was concluded to be best suited for needle-punched fabrics or in blends with jute (173). Suggestions have also been made to use the fibre as a filtration medium to cover sub-surface drainage pipes in Iraq (617).

ii. spathe: inspired by some traditional uses of the spathe studies were carried out (343) to isolate and analyze organic compounds responsible for the pleasant fragrance (and flavour) of spathe and its purported pharmaceutical properties for certain intestinal disorders. In a first attempt a distilled extract (pentane and ether) of freshly harvested spathes the analysis by gas chromotography revealed a prominence of 1,2-dimethoxyl-4-methyl benzene of up to 75% of total isolated volatiles. Male spathes contained about 40% more of this substance than female spathes and its content in absolute terms ranged from 0.7-1.1 g/kg spathe. It has a pleasant characteristic flavour somewhat like vanilla. In a subsequent investigation (338) a conventional chemical analysis of the major components of the spathe was carried out resulting in the following composition:

Table 30
Composition of spathe
%-age on fresh weight

The aqueous distillate was tested for antimicrobial activity (proved negative), and for biological activity in mice, rabbits, guinea pigs and frogs, without any effect on heart, blood pressure and muscle reactions.

Analysis of the distillate by gas chromotography revealed a number of organic compounds a.o. of the camphor family besides the earlier mentioned cyclohexenes. It is, however, clear that no final conclusions can be drawn at this stage of research on the active components in spathe distillate related to its flavour and pharmaceutical properties. Some work was carried out on the oil of the spathe (591).

iii. Pollen contains around 50% moisture and an average chemical analysis (on dry weight basis) of 5 Iraqi varieties is shown in Table 31. (95)

Pollen, also from other plant species claims to have high nutritive value which seems to be confirmed by above analysis with its relatively high protein, sugar and fat values. As mentioned previously early young male flowers when not yet required for pollination are eaten voluntarily by the date farmer. There is, however, more to the claim of nutritive value and a sort of mystique has built around it to the extent that pollen (of all kinds), collected from bees through special devices attached to beehives, is abundantly available in health food stores. In how far this is overrated by advertising and promotional efforts is difficult to judge. Isolation of micro elements has revealed the presence of estrone (30, 80), sterols, saponins, triterpenes and flavonoids (301). Snack foods have been supplemented with date pollen (2), but before indulging in pollen as a nutrient it is better to check for symptoms of allergy, otherwise the consumer may be in for an unpleasant surprise.

Table 31
Composition of pollen (dry weight basis)

iv. fibre: the cellulosic material of different parts of the palm (stalks, leaves) were hydrolyzed and tested on different strains of yeasts for production of single cell protein. A mixed culture of Candida Utilis and Saccharomyces sp. gave the best results (420).