Microbial degradation of animal hides and skins begins immediately after slaughter when the degradable enzymes that are naturally present in live animals remain active on the slaughtered hides. Micro-organisms from air, water and sea salt will also affect the hide quality.

Short-term preservation measures can be employed to slow down the rate of microbial attack during transport to the tannery. In Bangladesh, traditional preservation processes such as wet salting with Chittagong sea salt does nothing to slow down the rate of microbial attack and its growth on raw hides and skins as a whole.

At normal temperatures, freshly flayed hides and skins are particularly susceptible to attack by enzymes, resulting in decomposition of the collagen. They destroy the epidermal layer and hair follicles and turn the natural quality of the raw material from superior to inferior.

The most common salt loving halophilic bacteria such as Micrococcus roseus and others can reproduce, even in the salty environment of the curing process, causing low grain, red heat and other post mortem defects. The bacteria penetrate the skin via the exposed flesh surface where they can quickly multiply. Under ideal conditions, a single bacterium can divide rapidly and within 24 hours can have multiplied to give a population of 4,000 million.

Some of the typical problems in leather which can be caused by putrefaction are:

* grain damage

* weakness

* looseness

* staining

* chrome soaps

* spue

* uneven dyeing

Under normal storage conditions, red heat and purple heat bacteria take a relatively long time to grow. However, at higher temperatures, 30-40°C, growth of such bacteria will be more rapid. Warm, humid conditions favoured by red heat bacteria are also favoured by non coloured spoilage bacteria, so if the salt concentration is not high enough, putrefaction may still occur.

The bacteria from water and air also start functioning if there is a delay in salting, and poor preservation techniques, especially around the Qurbani Eid festival, coupled with the favourable atmospheric conditions, mean that decay sets in rapidly.

The annual availability of raw material in the country is now more than 180 million sq ft, of which 50% is collected within 2-3 days of Qurbani Eid.

During that period, the ultimate raw hide collection system through professional raw hide merchants could be bought under a specific awareness programme.

The establishment of six to eight hide centres is a new concept to protect raw hide resources from non-scientific preservation, smuggling and mishandling during the major raw hide collection season.

Raw hides and skins have great economic and commercial value to Bangladesh’s foreign exchange. Indeed in the fiscal year 2000-2001, the country earned US$289 million by exporting crust and finished leather, leathergoods, and footwear.

But the standard of leather quality, and hence the amount of foreign exchange that could be received, is greatly reduced by poor post mortem defects, mainly caused during preservation.

A major concern is the preservation of raw material using sea salt from Coxes Bazer’s offshore area. The grading of stock from the area means that six months after Qurbani Eid, the A and B grade wet-blue stock is totally unavailable.

Meanwhile, the availability of the lower grade leather, locally known as Kafa, has become a great problem in terms of the price offered by foreign buyers.

The local sea salt has a high hygroscopic tendency, which reduces the salt concentration in the preserved hides, and reduces the quality of the raw material.

The high quantity of tannery rejection grade skins is a hindrance to the development of the industry.

It is also costing Bangladesh a lot of money with estimates of loss income running into several hundred crore Taka (1 crore = 10 million).

To overcome this, a project sponsored by the Ministry of Science and Technology set out to develop a specific hide curing salt, which could successfully be used to increase the quantity of quality raw material collected during Qurbani Eid.

Research objectives

Preservation is an established part of leather manufacturing and correct preservation of raw hides and skins is indispensable in the leather industry for a country like Bangladesh, where the average temperature is 30°C and humidity is more than 80%.

The main objective of this research project is to develop a specific hide curing salt which could be used for raw hide preservation purposes.

During Qurbani Eid festival, Bangladesh has a raw hide collection of 50% of the annual availability and a need for a hide curing salt is substantial to save huge quantities of raw hides and skins.

This specific hide curing salt will be economically cheaper but not cheaper than common salt. This specific salt will be scientifically suitable for preservation with a sustainable economic importance to tanners as a whole. The hide curing salt could be prepared in the country with locally available chemical ingredients along with a very small quantity of imported items.

Present situation

The present situation in the preservation of raw hides and skins is mostly unscientific and due to ignorance, raw hide merchants are not aware of the modern and correct preservation methods for raw materials procured in such a hot tropical climate.

In India/Pakistan, they always use Khari salt (mine salt) for the preservation of hides and skins, which naturally contains specific chemical ingredients like magnesium sulfate, sodium sulfate as well as sodium chloride.

Hence Khari salt is very effective against micro-organisms and mostly suitable for the short-term preservation of raw hides.

Moreover, the hygroscopic nature of Khari salt is very poor, hence traditionally Khari salt is known as a very suitable salt for raw hide preservation.

Bangladesh does not have deposits of Khari salt and it is not commercially viable to import Khari salt and use it for hide curing purposes, so the country has to develop hide curing chemicals, where local sea salt will be the main element of the total preparation.

The present availability of knowledge on this subject is not adequate and, for the first time, research work is underway on this matter.

The chemical analysis of local sea salt has been carried out in Germany and India.

The details of the analysis are as follows:

1) TFL Ledertechnik GmbH & Co KG – Germany (research carried out in March 2000)

Ca (calcium) – 38 mg/kg

Mg (magnesium) – 13 mg/kg

NaCl (sodium chloride) – not checked.

2) Central Salt & Marine Chemicals Research Institute, Gujarat, India (research carried out in April 2000)

Ca (calcium) – not checked

Mg (magnesium) – 22 mg/kg

NaCl (sodium chloride) – 98.75%

The above analysis indicates the abnormal presence of Mg, which actually absorbs moisture from the air and also from the raw hides. This decreases the concentration of sodium chloride solution inside the preserved raw material.

A temperature of more than 35°C inside the pile of hides and skins also accelerates the growth of micro-organisms very quickly.

The preparation of a specific hide curing salt in a commercial manner would be possible after extensive research work and close observation has been carried out.

This was done at the last Qurbani Eid in March 2001. Several options were available and researchers selected one or two among them. A total 3,300kg of developed hide curing salt was handed over to Dhaka Hide & Skins Ltd on the eve of the last Qurbani Eid.

The authority of Dhaka Hides & Skins cooperated with the researchers and applied the salt on Qurbani hides on March 7, 2001, and on May 6 the first of the preserved hides were sent for the beamhouse process of soaking.

Physical properties of the hides preserved with the hide curing chemicals:

* Normal observations showed the hides remained fresh

* Any bad odour was totally absent

* The raw hides become drier than normal hides preserved with normal salt

Microbiological observations:

* Halophilic bacteria were absent

* Hide substance was found to be good


Rapid and appropriate curing is key in the preservation of raw hides and skins in any country in the world.

Raw hides and skins should be cooled immediately after flaying in order to dissipate any remaining body heat and should be kept cool until the hide is salted.

As soon as possible, the raw materials should be treated with clean salt or especially prepared salt in a quantity equivalent to no less than 35% of the green weight.

The development of a hide curing salt will provide great support and service to the leather industry of Bangladesh by improving the quality of raw hides and skins and the grading of the leather during the export process.

The project, if implemented in a proper way in the country, will protect the country’s raw hide and skin resources from degradation during preservation, especially in the Qurbani Eid season. So with the development of hide curing chemicals instead of normal sea salt, Bangladesh can expect qualitative changes in the basic quality of their raw hide and skins.

The development of a specific hide curing salt for raw hide preservation will mean that Bangladesh will have the opportunity to study and identify the scope for upgrading leather quality in the practical field. The scientific value of this hide curing salt is very high but commercially the cost per kg may be higher than the normal sea salt, but this should be absorbed by the post curing benefits.


A common fund has to be created for taking subscriptions from all the exporters of leather and leather products from the country.

This fund will be used for the commercial production of developed hide curing salt and its distribution system.

The BFLLFEA, BTA, the Hide Merchants Association and Leather technologist societies should come forward and urgently support the implementation of the developed hide curing salt project.

Foreign agencies such as the World Bank UNDP, Unido and Sida should back the establishment of the six or eight hide centres in Bangladesh.

Posters should be printed to create awareness among raw hide traders, Foria, hide merchants and Madrasha & Orphans about the benefits of using developed hide curing salt during raw hide and skin preservation.