To purge or not to purge...
Effectiveness of a Saltwater Bath in Purging Crawfish
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Immersing farm-raised crawfish in a water bath prior to cooking, even for as little as 10 minutes, aids in removing mud and debris from the exterior of the animal as evident from the immediate increase in turbidity of the wash water. As crawfish rub against each other in a crowded water bath, it loosens material from the exoskeleton. The results of this study also suggest that a water bath may aid in lessening the amount of content contained in the hindgut by a small percentage.
The amount of hindgut content in crawfish was greatest among the nonwashed specimens. Regardless of whether gut contents were expressed as a percentage of whole wet crawfish weight (0.07 percent) or as dry abdominal weight (1.9 percent), the relative hindgut content weight of fully purged crawfish was significantly lower, approximately 60 percent less than that of crawfish not washed (Figure 4). The 10-minute water baths, with or without salt, resulted in from 17 percent to 26 percent less gut content weight than nonwashed specimens. Salt provided no significant advantage in this study despite the numerous claims that continue to be made to the contrary.
To address the question posed by some regarding the effect of salt in a water bath on crawfish mortality, death was assessed immediately after the bath and then again after 72 hours under refrigerated storage. Less than 1 percent of dead crawfish were observed immediately after the water bath, and these may have been simply due to handling. While mortality was typically low after 72 hours of refrigerated storage, more deaths were observed in association with the saltwater bath (6.2 percent) than the freshwater bath (1.9 percent). This effect may be a moot point because in nearly all cases, crawfish are cleaned shortly before cooking only. The home consumer will likely not store live crawfish after cleaning, and the retail or restaurant trade, which typically receives live crawfish chilled, will likely keep the animals in a chilled condition until cleaning immediately prior to cooking.
In conclusion, preparing crawfish for cooking by immersion in a water bath, with or without salt, for a short time will often provide some degree of cleansing, although this is mainly associated with exterior surfaces and the gill cavity where debris can accumulate. The amount of digesta in cooked crawfish subjected to an adequate wash may not be discernible from nonwashed crawfish; however, washing will lessen the amount of debris shed during the cooking process. There is no evidence from this study that suggests the use of salt in cleansing crawfish was beneficial, but results do indicate that a saltwater bath may contribute to increased mortality, if washed crawfish are subjected to refrigerated storage for several days prior to cooking. Conventional commercialstyle purging for 12 hours or longer is the only known way to significantly reduce the size of the hindgut in cooked crawfish, and that method is usually not practical for consumers.
