d. Additional treatments

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Whilst, given the right variety and maturity, fumigated, sorted and cleaned dates, are ready to be packed, either in bulk or retail packs, in a number of cases additional treatments are given to upgrade their quality and prolong their storage life, before being packed and going to markets. These treatments, which vary according to need, are briefly discussed:

i. Maturation (curing): what has been described in former chapters on sun curing and drying of khalaal and rutab, can also be achieved by artificial heat treatment in circumstances where ripening is not completed entirely on the palm or early rains threaten to damage the crop. In its pure form artificial maturation consists of imitating the optimum conditions for ripening on the palm. The process requires rooms in which temperature, humidity and air ventilation can be controlled. Maturation is quite often accompanied by dehydration, i.e. removal of moisture. Optimal temperature for Deglet Noor should not exceed 35° C, but most other varieties will permit higher levels, though not exceeding 50° C. Relative humidity also varies according to variety and the need to remove moisture or not. Because of these moderate conditions, the time required is usually rather long, a matter of days rather than hours. Artificial maturation is therefore a delicate, time-consuming process, and very variety-specific. Taking into account also the non-stable conditions of the incoming dates from week to week and season to season, it stands to reason that artificial maturation requires much practical experience by the date packer.

At this point mention should also be made of the steam treatment to Deglet Noor in North Africa to promote the enzymatic inversion of sucrose into invert sugar to render them more pliable and soft. The treatment consists of submerging the dates in water for 8-15 hours, after which they are treated with live steam at 60° C for 3-7 hours in an enclosed environment. After having been left in baskets for 24 hours to "settle" the dates are heat treated for 1 hour at 70° C in a cabinet dryer. After cooling they are ready for packing. During the process the dates increase in moisture, become softer and obtain an attractive gloss. A U.S. company has drawn out a patent on a similar process to turn "light-coloured U.S. grown dates into the darker, soft, chewy texture of Middle East dates". The temperature of steam treatment in this process is at 175° F (almost 80° C) (553). These treatments could be considered a combination of maturation and hydration.

ii. Dehydration: The aim of dehydration is to remove moisture artificially from the fruit without affecting its desirable qualities. It is a common process in the dried fruit industry (prunes, apricots, peaches, apples, etc.). Dehydration becomes necessary when dates contain too much moisture and will not be consumed immediately or stored under refrigeration. For instance, a desirable moisture content for Deglet Noor, acceptable to the consumer, is 23-25%, self-preserving with soft texture (478). Dehydration can be carried out in maturation rooms or in specialized cabinets (for small quantities) and tunnel dryers for large-scale operations. In all cases the principle is the same: moving air of a certain temperature and humidity over the dates. Moisture from the dates absorbed by the air has to be disposed of through air vents. Drying time and drying rate is a function of temperature, relative humidity and velocity of the air. For drying of soft dates 65° C is recommended, which will ensure a reasonable drying rate (a date by nature is rather resistant to losing moisture) without affecting the basic qualities. Relative humidity, to avoid case-hardening and also for fuel economy, should be maintained (by recirculation of drying air) at over 40%, but should not exceed 60% (at the cold end). Sometimes, but this is only possible in batch-wise cabinet dryers, at the final stage of drying the temperature is raised to obtain a pasteurizing and glazing effect and insect kill. The limitations of dehydration and possibilities for these combined treatments depend very much on the type of date and the desired result. Natural dark dates will suffer less from darkening caused by high temperature than the light coloured ones. A special case presented itself when deep frozen khalaal were thawn and dehydrated artificially to rutab in a tunnel dryer. Drying temperature had to be reduced to 45° C to prevent frothing which occurred at higher temperatures.

iii. Hydration: Dates that are considered too dry because they have been left longer than usual on the palm, or excessive dry hot weather has dried them out, can in many cases be restored to a pliable, soft fruit by hydration, i.e. adding moisture. There are several methods of hydrating date fruit, the most simple one being the sprinkling of water on a heap of dates and leaving them in the sun under a cover of mats (139). But it may take weeks before the results are visible. Soaking in cold water and later by hot water was applied for some time but this fell out of use, mainly because of the time factor and related microbial infection problems. The most common method of hydration is with low-pressure live steam in an enclosed environment. Apart from a much quicker uptake of moisture than soaking, steam may at least partially inactivate insects and micro-organisms and it also leaves the dates with an attractive gloss.

Typical condition for Deglet Noor hydration in California is 4 to 8 hrs at 60° C with steam of 5 PSI (about 0.4 atm) (478) which corresponds with the example for North Africa given under heading i. Maturation. During this treatment the dates will gain several percentage points in moisture. Another method of hydration consists of evacuating the air from sub-merged dates under vacuum. Upon release of vacuum, water (or in a modified version live steam) will penetrate the date in proportion to the vacuum applied. This batch-wise vacuum method with its disadvantages has been ingenuously turned into a continuous operation by making use of a natural difference in pressure occurring in the two legs of a syphon, as illustrated in Figure 48. Two vessels at different heights are connected with an overhead syphon and a second pipe fitted with a centrifugal pump connecting the two tanks at bottom level. To set the system going the two vessels are filled with water and an air suction pump fitted at the highest point of the syphon will suck water into both legs until the water from the shorter leg will overflow into the longer leg and syphon action is established. At this point the in-line centrifugal pump in the bottom pipe is switched on to recirculate the water from the lower to the higher tank. Dates fed into the upper tank will be carried along with the water stream and subjected to a slight under pressure in the shorter leg, just enough to draw some air from the inside of the date to be replaced by water when the pressure returns to normal (in the longer leg). Dates are separated in the lower vessel by a continuous chain elevator.

iv. Glazing: A short high temperature treatment, quite often at the end of hydration, with vigorous air movement will make the wax on the date surface melt and upon cooling reset in an attractive gloss. 5 minutes at 130° -140° C is recommended for Deglet Noor (467), whilst for Zahdi dates also a satisfactory lustre was produced at 130° C for 5 min. (329). Steam treatment for 10 min. also gave acceptable results (437). This gloss will eventually disappear, especially during storage exposed to air, but normally will last sufficiently for the expected marketing period.

In conclusion of these additional treatments (i to iv) which are all based on the manipulation of temperature and moisture content, and incorporating heat treatments for enzyme inactivation and microbial and insect control, dealt with under b: "Storage", it is felt useful to review the time/temperature relationships for the different operations in a diagram (Fig. 49). It is evident that the application of heat has a promotional effect asfor instance in maturation, hydration, moisture removal and glazing whilst in others it is applied to prevent, such as in enzyme inactivation, insect control and pasteurization. In all cases, restricted by the degree of the susceptibility of the date to heat, care should be taken to depress undesirable side effects from heat treatment. This will not always be possible and a compromise will have to be sought.

v. Coating: Apart from glazing, which makes use of the naturally available wax on the date surface, several materials have been used to improve the appearance of the date by giving it more lustre and protection and reduce stickiness when it concerns soft dates. Some examples are: a 37° Bx date liquid sugar solution, starch derivatives, sodium alginate and commercial pectin proved excellent coating and glazing agents, especially when dates were kept in cool storage (329). A British patent (52) refers to coating dates in a fluidized bed of heated air with a mixture of partially acetylated monoglycerides from hydrated cottonseed oil. After cooling the coat is reportedly impermeable to bacteria and prevents moisture loss upon storage. Literature makes further mention of the use of sugar syrup, mineral oil, glycerine (139), 6% cold-water soluble starch, and 3% methylcellulose (527).

Whatever the merits of the above materials, the present trend in date coating is to "stay natural" and not to add foreign materials to the product that may be frowned upon by the law and by the consumer.

vi. Pitting: The traditional, and by no means abandoned, method of removing the pit from the date is by hand, mostly with the use of a knife cutting open one side of the fruit, removing the pit and folding the two sides of the date together to make the cut almost invisible (Iraq). If done properly this method also provides an opportunity to check on insect infestation. In Iran field pitting is done in certain areas with a blunt needle piercing the pit out end-wise. This method can be considered the manual forerunner of the mechanical date pitters that have been devised. As can be expected hand pitting is rather slow and yield per hour does not normally exceed 5 kg (139, 363). Pitted dates pressed into blocks and sliced create an attractive marbled product (Fig. 50).

For soft dates the pit can be squeezed out between the fingers at the same time removing the skin. This is done for the preparation of agwa, a soft date paste preserved in jars (a.o. in Egypt) (139). This principle of removing the pit could be compared to mechanical date maceration, by which the pits are removed but the date loses its identity and is produced as a coarse date pulp.

The working principles of both mechanical date pitters are as follows: in the whole date pitter incoming dates are lined up vertically in cups, by a special feeder. The cups are tightened around the date to hold them in position and move them intermittently along an endless belt (90-130 strokes per minute) up to the pitting head. Here pins will descend and pierce out the pits end-wise. The pits drop underneath the belt and are collected whilst the cups with pitted dates move on. The grip on the date is released and the conveyor turns down at which point the pitted fruit drops out of the cups and is collected. Because most dates and their pits are longitudinal in shape, the vertical alignment in the cups is of utmost importance. Preferably dates should be graded for size and correlated to the cup size. Output of these machines is in the order of 250-400 kgs/hr. (38, 160, 580).

The date macerator works on the principle of feeding dates between two almost touching rollers turning in opposite directions. One roller is covered with a thick layer of rubber of a determined density, the other consists of notched steel disks separated by washers about 2 cm smaller in diameter and 0.5 cm wide. When dates are fed between the rollers they are squashed, where the two rollers touch and the flesh penetrates in the slits between the notched disks but the pits, being too big for these, are momentarily pushed in the rubber. Whilst the pit will almost immediately again be pushed out of the rubber the date flesh will rotate along the toothed roller until being removed by scrapers positioned after about half a turn of the roller. Both flesh and pits are collected in separate chutes.

The operation will now be repeated with two rollers with all dimensions reduced with the aim of removing the calyces. The machine can give good results, up to 1,000 kg/hr, provided dates are used of the right moisture content, which if necessary should be obtained by artificial means prior to maceration. The resulting macerated dates are a starting point for the manufacture of date products (see Chapter 2).

e. Packing whole dates: Loose tamr is frequently sold in the markets, not only in date producing countries, but they are also still commonly found on the stalls of the weekly open- air markets around the Mediterranean and Northern Europe (Fig. 51). Here they are part of the dried fruits and nuts assortment such as apricots, prunes, carob, peanuts, almonds etc. The type of container and packaging material used for tamr in the national and international date trade is varied and can be subdivided in:

- traditional bulk packs
- export bulk packs
- retail packs

Bulk packs for dates have been traditionally jute bags for the harder types and baskets woven of palm leaflets or tins in which the softer types of dates are pressed. Both types are still in use, the basket specificially for export of lower quality dates as popular food or for industrial use. Bags, amongst other means, are used for the transport and sale of khalaal matbuukh. Dates are sold straight from the baskets or bags in the local markets. The process of pressing dates has at least partially been mechanized by the introduction of semi-automatic presses, which however require a standard size basket or tin. In North Africa the traditional bulk pack for transport and bulk sales is a wooden box holding 20 to 30 kgs of side in layers is seldomly found anymore (Fig. 52).

The standard size bulk case of 70 lbs for the specialized export trade from the Gulf area to the USA and to Europe which amounted to thousands of tons at one time, has been in use for a long time. The prepared sides, bottoms and covers for the boxes had to be imported from European countries to be reassembled on the spot. Later developments have seen also the use of carton boxes, with or without inner plastic bags for extra protection. Filling and pressing of wooden and carton boxes has been fully mechanized, usually in two stages, that is, approximately half the amount of dates are filled automatically and compressed by a plunger, after which the second half is added to be compressed by a second plunger in the continuous production line. Later sizes adopted for the export trade have been boxes of 45 lbs unpitted, and 50 lbs pitted select quality dates for repacking (-use) in the country of destination and 55 lbs good average quality (GAQ) dates for use in the baking, sauce, pickle and confectionery industries.

By far the most variety of packing style, size and materials developed over the last century is in the packs intended for retail sales. Perhaps part of the inspiration for this diversification was obtained from a study in the U.S. (437) which clearly showed that the more variety was put into the presentation of the product, the more volume was sold. A few historical lines in retail packing can be traced which persist up to today. The most well-known confection for North African dates, principally Deglet Noor, has been the glove box ("boîte à gants"), originally totally made of wood strips, in which the dates are packed in fish bone arrangement along a central piece of spikelet. Contents ranged from 200 to 250 g. Making and handfilling of the pack is costly, and the wood material has now been replaced by carton or plastic, but the form persists (Fig. 53). Deglet Noor, probably following the trend of consumer preference for natural products, are also marketed whilst still attached to the spikelets as they come off the palm, mostly in cellophane bags or window carton (Fig. 54). In the Near East much use is made of polythene bags (Fig. 55) and cellophane for pressed dates (Fig. 56). Small moulds with a sheet of cellophane and label underneath are filled in layers with a weighed quantity of dates, after which with a weight or by a simple lever press the lined-up dates are compressed in the mould. The mould is removed and the cellophane is wrapped around the block and heat sealed. This type of pack, usually ranging from 100 g up to 1 kg in size and used for soft dates, has the advantage of additional keepability because of the pressing and tight fit of the cellophane which keeps the original appearance and gloss for a longer period. On the other hand, to the consumer the tightly pressed dates may be less appetizing. For loose dates the closed window carton and transparent plastic cup are popular, because filling is quicker and for the latter two the product can be seen (Fig. 57).

In California dates are packed in cellophane bags, overwrapped trays, plastic cups, fibreboard cans, all-metal cans (478) in sizes varying from 8 ounces (about 250 g.) to 3 lbs. (about 1 and a third kgs) (Fig. 58). The dates for bulk trade are packed in 15 lbs (6 3/4 kg) reinforced cartons or wooden boxes. For longrange transport, also overseas, they are usually pallatized. For softer types, flatter cartons of 10 lbs are used.

Vacuum packed dates, either in bags (Iraq) (Fig. 59) (289) or in cans (US) has met with some success but has not taken the market in any appreciable way. Trays overwrapped with stretch cellophane, gives a very attractive appearance and has been successfully applied to frozen khalaal (Bahrain) (Fig. 32) and is also found in use for tamr (Fig. 60).

Whatever small packs have been designed, tried and sometimes failed, one of the major problems has been the cost of the packing operation itself. The date as a fruit, even in a dry form, does not lend itself well to mechanical packing in small packs, though some semi-automatic bag fillers are in operation (Fig. 61). However, progress has been made and there are now several machines on the market that will fill and seal small packages of dates, of 100, 125, 200 and 250 g at the rate of 360 to 900 kgs/hr (290, 580) (Fig. 62).

A further sampling of the great variety of date packs found in various markets is represented in Figure 63.

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