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Transglutaminase (TGase) from the threadfin bream ([TB]Nemipterus sp.) liver was partially purified using ion exchange, size exclusion and affinity chromatography. Three protein bands with molecular weight (Mw) of 95, 63 and 43 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were observed. Only one distinct fluorescent band appeared on the TGase activity staining of the native-PAGE. When the protein band was eluted and analyzed on the SDS-PAGE, it showed a single band with an Mw of 95 kDa. The enzyme required Ca2+up to 1 mM for full activation. TGase was also activated by 10 mM Sr2+. Dithiothreitol had no effect on activity. TGase activity was unaffected by NaCl up to 0.6 M and reduced to 75% at 1.2 M NaCl. Optimum pH and temperature was 8.5–9.0 and 50C, respectively. TGase activity was markedly inhibited by the sulfhydryl reagents. The enzyme catalyzed the cross-linking of the TB myosin heavy chains. PRACTICAL APPLICATIONS Threadfin bream (TB) liver transglutaminase (TGase) exhibited Ca2+-dependent characteristic similar to muscle TGase. The enzyme catalyzed the cross-linking of myosin, and therefore, could be applied to improve the textural properties of muscle proteins. The enzyme remained its high activity up to 1.2 M NaCl (≈7% w/v), indicating its potential application in foods containing a relatively high NaCl. The biochemical characteristics of the TB liver TGase are critical information leading to more understanding in the nature of the enzyme as well as determining the optimum conditions for food applications. Moreover, the presented purification scheme could be adopted to recover TGase from the TB liver, which is currently a solid waste of the surimi industry.

The protein solubility and molecular-weight distribution of freeze-driedsarcoplasmic proteins (SPs) from rockfish treated under low and high pH aswell as various NaCl concentrations were elucidated. The solubility of SPswas significantly suppressed at an acidic pH (2.0–4.0) and in the presence ofhigh salt concentration (0.5 M NaCl). The least amount of protein was lostwhen SPs were treated at pH 2.0 or 3.0 followed by precipitation at pH 5.5.The interaction of SPs with Alaska pollock surimi (myofibrillar proteins) wasalso investigated. The addition of SPs appeared to delay the thermal denatur-ation of myosin and actin. The SPs positively contributed to the gelation ofmyofibrillar proteins as judged by breaking force. INTRODUCTION A new method for preparing fish protein isolate using pH shift hassignificant advantages over conventional surimi processing. This revolutionaryapproach can reduce water usage and subsequently minimize wastewater prob-lems. The new method can also provide extremely high yields (35–40%)because it solubilizes nearly all myofibrillar and sarcoplasmic proteins (SPs)through homogenization and pH adjustment before centrifugal recovery. Incontrast, the conventional process removes SPs through washing and dewater-ing, which results in significant protein loss and excessive water usage, andcontributes to wastewater problems (Hultin and Kelleher 1999; Hultin

Microwave-vacuum drying was investigated as a potential method for drying cranberries. Cranberries were pretreated with either 30°B or 60°B high fructose corn syrup solution for 24 h. They were dried using a laboratory-scale microwave-vacuum oven operating either in continuous or pulsed mode until the final moisture content reached 15% (wet basis). In the continuous mode, two levels of microwave power (250, 500 W) and absolute pressure (5.33, 10.67 kPa) were applied. In the pulsed mode, microwave power of 250 W and two levels of pressure (5.33, 10.67 kPa) were used with two levels of power-on time (30, 60s) and three levels of power-off time (60, 90, 150s). Pulsed application of microwave energy was more efficient than continuous application. In both cases, drying efficiency improved when lower pressure (5.33 kPa) was applied. Shorter power-on time and longer power-off time provided more favorable drying efficiency in pulsed mode. Power-on time of 30 s and power-off time of 150 s was the most suitable setting for maximum drying efficiency.

Color, texture and water activity of microwave-vacuum dried cranberries were evaluated and compared with the corresponding properties of hot-air dried and store-bought cranberries. The microwave drying was done both in the pulsed and continuous modes. The microwave-vacuum dried cranberries were redder and had a softer texture than those dried by the conventional hot-air method. The storage stability of the product dried by microwave-vacuum method was comparable to that of conventionally-dried cranberries. The microwave operating conditions have an effect on the quality of the dried cranberries.