Abstract

Under the present marketing system in this country by which hides and skins are transported from the abattoir to the hide market before any effective cooling and salting takes place, quite severe deterioration can take place during the inevitable delay between flay and cure. The restricted space in most abattoirs for hides and skins, the current high rate of through-put and labour costs restrict or prevent any cooling being given at the abattoir. Sheepskins are particularly vulnerable to deterioration at this stage, as they are flayed in a far shorter time than cattle hides and so cool less during this operation and in addition the dense fleece slows the rate of cooling. In 1971 the BLMRA showed the advantage to be gained by forced cooling of sheepskins: skins cooled to 10°C remained in a good state of preservation for 30 h. This can readily be done with no extra labour by conveying skins under cold air fans. Putrefaction can also be retarded by spraying the flesh surface of the skin with a biocide. Imperial Chemical Industries Ltd (ICI), Organics Division, have produced a biocide—Vantocil IB, which in laboratory trials was found to retard putrefaction for several days when sprayed over the flesh surface of a newly flayed skin. Large-scale trials under normal working conditions of pile size and storage conditions have been carried out with the co-operation of ICI and are described in detail in this paper. These have shown that by spraying the flesh surface of newly flayed sheepskin with a 10% aqueous solution of Vantocil TB and then piling the skins wool to flesh, putrefaction was prevented for two days. Chemicals sprayed on the flesh side of a raw skin can have adverse effects on the final leather such as the levelness of dyeing, the way the flesh surface reacts to sueding and the general handle and strength of the leather, as was found with sodium chlorite. These present trials, however, have shown Vantocil IB to have no such adverse effect, rather to the contrary that the sprayed skins yielded a higher percentage of first-grade clothing suedes. The evidence obtained from these trials allows Vantocil IB to be recommended as an agent for the temporary preservation of hides and skins. The length of time for which Vantocil lB can protect hides and skins is highly dependent on the circumstances prevailing at its use, hence the difficulty in quoting “safe limits.” In the first trial described here, had the skins been forced cooled to 10°C before or after spraying, no doubt putrefaction would have been delayed for longer than the two days. On the other hand had the skins retained most of the body heat to remain at about 30°C, putrefaction could well have begun earlier. In this same trial the skins were piled wool to flesh so that there was maximum contamination of the flesh by dung and dirt on the wool. Had the skins been folded flesh to flesh immediately after spraying again the “time limit” could well have been longer than the two days. To obtain maximum benefit from a biocide spray such as Vantocil IB it needs to be applied immediately the skin is flayed. This can readily be done by passing the skin on an arm conveyor from the flay line, under sprays of biocide. Ideally the skin could be forced cooled whilst still on the same conveyor. Spraying the skins can have economic advantages above the cost of the spray itself in that skins can be safely left in pile overnight at the hide market and be handled the following day. At times when the kill is sufficiently small as to make it uneconomic to collect skins daily, skins sprayed and effectively cooled could remain at the abattoir or in a waiting truck and be collected with the following day’s skins. The danger in this practice lies in the delay extending for some batches of skins to three, four or five days by which time putrefaction could be advanced. Spraying the skins at the point where they are loaded into the lorry at the abattoir, by using a small portable spray unit would protect the skins during transport delay and overnight delay before salting at the hide market. However, the time interval between flaying and spraying in this way needs to be no longer than 4 h. The trade has also expressed interest in the use of Vantocil TB with the aim of eliminating the use of salt. This entirely depends on whether the skins and hides can be transported and put into process within the protective period provided by the Vantocil lB spray. If skins or hides are sprayed immediately after flay and folded flesh to flesh this may provide a time limit of 3-5 days. As in some instances hides are washed, green fleshed and this clean surface then sprayed with Vantocil IB, and protected by folding flesh to flesh, then it is likely the time limit can extend to seven days, although hides treated in this way have not been examined by the BLMRA. Again care must be taken not to regard such time limits as safe limits irrespective of the ambient temperature and precautions need to be taken in the summer months not to delay too long. To conclude this work it would be a major advance in the handling of hides and skin in this country if equipment were to be installed in abattoirs by which hides and skins are sprayed with a biocide such as Vantocil lB immediately after flaying and then cooled to 20°C or below. The raw material reaching the tanner would be in a very good state of preservation, and this would eliminate one of the main causes of variation between hides and between skins. When the raw material is so high priced as it is today, it is regrettable that quality is lost at such an early stage in the production of leather.