Autolysis of bovine skin, its endogenous proteases, protease inhibitors and their effects on quality characteristics of extracted gelatin

Effect of different dehydration methods on the properties of gelatin films

The properties of gelatin film fabricated by ethanol precipitation effect dehydration, Hofmeister effect dehydration and hot air drying dehydration were investigated. The results revealed that the mechanical properties were significantly improved by ethanol precipitation and Hofmeister effect. The tensile strength and elongation at break of the film prepared by ethanol precipitation were increased by 83.28% (20% gelatin concentration) and 122.42% (5% gelatin concentration) respectively compared with that of hot air-dried gelatin film. The water contact angle was increased and water solubility was reduced by ethanol precipitation, which could attribute to the formation of compact structure, more triple helix content, and non-covalent interactions. However, the water contact angle of Hofmeister effect fabricated films was decreased compared with that of hot air drying owing to the adhesion of ammonium sulfate. Moreover, ethanol precipitation effect improved the color difference and opacity due to the ethanol decolorization effect.

Broad range of substrate specificities in papain and fig latex enzymes preparations improve enumeration of Listeria monocytogenes

Numerous applications of proteolytic enzymes include dissociation of fermented meat products for the enumeration of `foodborne pathogenic bacteria. The use of trypsin for this cause is abandoned due to the high concentration of the enzyme affecting released bacteria. Papain, as a suggested replacement, and fig latex preparation with high extent of papain-like enzymes have the potential to be applied for bacteria enumeration. Both enzymatic preparations, originating from papaya and fig, showed a broader range of substrate specificities including gelatinolytic activity, especially prominent in the case of ficin and attributed to both, cysteine protease ficin and serine protease by the analysis of 2D zymography with specific inhibitors. The activity towards native collagen, mild in the case of papain, and extensive in the case of fig latex was proved by structural analysis of digested collagen by infrared spectroscopy. Further exploration of their potential for dissociation of fermented meat products showed that both papain and fig latex enzymes are stable in the presence of detergents Tween 20 and Triton X-100 and effective in the enumeration of Listeria monocytogenes. Gelatenolytic activity, and at least partial collagenolytic activity and stability in procedure conditions make papaya and fig latex proteases potent for this application in significantly lower concentrations than previously used enzymes. As a mixture of proteolytic enzymes with divergent characteristics, fig latex preparation shows higher efficiency in Listeria monocytogenes release than papain, conserved even in the presence of stronger non-ionic detergent Triton X-100.