![]() Crandall, in Food and Feed Safety Systems and Analysis, 2018 Chemical Dehairingīowling and Clayton (1992) developed a chemical dehairing process designed to remove hair and contaminants from the hide before removal of the hide from the carcass. In some cases, hides are washed with surface-active or emulsifying agents (i.e., quaternary ammonium salts of higher fatty alcohols).Ĭorliss A. ![]() Degreasing is done by warming hides in water and pressing them in a hydraulic press, followed by washing and rinsing. Some hides such as kidskins, sheepskins, and pigskin contain a large quantity of fat ( Table 9). ![]() Weaker tanning solutions for longer lengths of time are used. Either chrome or the vegetable process can tan this type of product, but the wool must be cleaned and degreased. Some leather is tanned with the hair or wool remaining on the hide (e.g., shearling leather) that is produced from sheepskins (uniformly clipped to short lengths). This technique has the advantage that the hair comes out by the roots, and it yields more hair and a cleaner hide grain. Enzymes can also accomplish dehairing and dewooling. If all of the hair is not removed by the chemical reaction, the dehairing machine removes the remainder. Pigskin requires higher concentrations (4–5%) of sulfide than cattle hides. Hair can be totally dissolved in a few hours. More concentrated solutions that have a higher pH (>11.5) and are applied at higher temperatures can be used. In 2–4 days, hair is collected, washed with water, rewashed in water (100 parts) with acetic acid (1 part), and dried. If hair is to be saved, a weak solution and a low temperature is used, and only the hair roots are loosened. Dimethylamine sulfate is also often used and allows reduction of lime and sulfide concentrations. Another formulation uses 30% water, 6–12% sodium sulfide, 2–3% sodium bisulfide, and 4% hydrated lime. Other mixtures used to remove hair might include milk of lime (CaO) fortified with sodium sulfide (NaS), sodium bisulfide (NaHS), arsenic sulfide (As 2S 2), or dimethylamine ((CH 3) 2NH). The most common chemical depilatory agents are a saturated solution of calcium hydroxide (Ca(OH) 2 hydrated lime) and sodium sulfide (Na 2S) or sodium bisulfide (NaHS) at a pH of 12.5. The dehairing process is chemical in nature however, mechanical dehairing equipment is sometimes used after hair has been chemically loosened. Basu, in Encyclopedia of Meat Sciences (Second Edition), 2014 Dehairing Carcasses are then subjected to spot decontamination and trimming to once again adhere to USDA-FSIS (1993) ‘zero-tolerance’ performance standards. This is followed by a buffing and singeing process to remove any remaining hair. The second step in dehairing is the scraping process which incorporates physical contact with simultaneous washing to remove hair. The submersion water utilized in this process can be problematic as it becomes highly contaminated with feces, dirt and other environmental contaminants which are carried on the external surfaces of animals and the water temperature is not sufficient to instantly kill many microbes. This step is complete when the hair follicles are loosened such that hair sloughs from the skin. Scalding is accomplished by submerging the entire carcass in hot (60–63 ☌) water for several minutes. ![]() Generally the process commences immediately following exsanguination of the animal and begins with the scalding process. This procedure again requires multiple steps for completion, but it is much less invasive and therefore does not create similar opportunities for subcutaneous carcass contamination. Scanga, in Improving the Safety of Fresh Meat, 2005 13.2.4 Carcass dehairingĭehairing of carcasses is a process which is practised widely in swine processing facilities.
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