Crioprotetores e inibidores de proteases na proteólise e geleificação do surimi de tambaqui (Colossoma macropomum) e matrinxã (Brycon amazonicus) sob estocagem congelada

Abstract

This study evaluated the yield, chemical composition, autolytic activity, texture, and color of surimi of tambaqui and matrinxã, and proposed improvements in the frozen storage and thermal gelation steps through the use of cryoprotectants and protease inhibitors. Studies have shown that losses during processing reduce the yield from 40%, for mechanically deboned meat (MDM), to 36%, for tambaqui surimi, and in the case of matrinxã species, the results were 48.5% and 40.5% for MDM and surimi, respectively. The centesimal composition of MDM revealed that successive washes increased the moisture content in both fish, thus, obtaining a special class of surimi according to the moisture criterion. There was a reduction in protein content during the washing step due to the removal of sarcoplasmic proteins. This process also reduced the mineral content of the fish; however, it was not efficient in removing lipids. The water-holding capacity (WHC) data showed a tendency to decrease after 90 days of storage, regardless of the type of cryoprotectant used. Protein solubility did not show great variations until the end of the experiment. The texture was significantly affected by the length of the storage time, as it started, decreasing after 90 days. These results were confirmed by electrophoresis, which revealed significant denaturation of myosin after 120 days of storage. The use of a cryoprotectant mixture containing 4% sucrose, 4% sorbitol, and 0.5% sodium tripolyphosphate gave us the best results for both the species studied. The results for autolytic activity levels showed that 5% soy protein isolate treatment was most effective, inhibiting around 60% of the autolytic activity in surimi of tambaqui and matrinxã. Both soy and potato extracts gave good results which indicated that serine proteases play an important role in the muscle proteolytic activity of both species. The addition of inhibitors improved the elasticity of gels measured via a folding test, where all treatments obtained AA concept. The results obtained for gel strength measurements (g.cm) for tambaqui kamaboko showed that only potato extract treatment at 1% did not improve the texture, however this value was statistically equal to the control. In matrinxã kamaboko, the gel strength improved after the treatments with ovalbumin (5%) and soy protein isolate (3% and 5%), but decreased after treatment with potato extract. The soy protein isolate and potato extract caused losses in the “whiteness” of the product, however this value remained above 70%. To conclude, soy protein isolate is the most efficient inhibitor for both the species of fish studied here.