Myosin and actin denaturation in frozen stored kuruma prawn Marsupenaeus japonicus myofibrils
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ORIGINAL ARTICLE
Food Science and Technology
Myosin and actin denaturation in frozen stored kuruma prawn Marsupenaeus japonicus myofibrils Thitima Jantakoson • Wichulada Thavaroj Kunihiko Konno
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Received: 26 September 2012 / Accepted: 9 December 2012 / Published online: 1 January 2013 Ó The Japanese Society of Fisheries Science 2012
Abstract Myosin and actin denaturation in kuruma prawn myofibrils stored frozen (0.1 M NaCl, pH 7.5) at -20 °C was investigated. The inactivation profile of Ca2?ATPase in the myofibrils was identical to that for myosin, indicating that myosin in myofibrils was not protected by actin. The presence of myosin detached from actin in the soluble fraction was proven by ammonium sulfate fractionation in the absence and presence of Mg-ATP. Actin denaturation in myofibrils was further confirmed by its increased susceptibility to chymotryptic degradation. In the frozen myofibrils, actin denatured more rapidly quicker than myosin: actin had completely denatured by storage day 1, followed by a gradual denaturation of myosin. Both myosin and actin in the frozen stored myofibrils retained their high salt-solubility, which decreased slowly during the frozen storage period. The presence of aggregated inactivated myosin in the salt-soluble fraction was proven by precipitation at 40 % saturation of ammonium sulfate in the presence of Mg-ATP, leaving active monomeric myosin in the soluble fraction. Almost no actin denaturation was observed with heated myofibrils.
T. Jantakoson W. Thavaroj K. Konno (&) Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan e-mail: [email protected] T. Jantakoson Faculty of Agricultural Technology, Songkhla Rajabhat University, Mueang Songkhla, Songkhla 36000, Thailand W. Thavaroj Faculty of Liberal Arts, Rajamangala University of Technology Srivijaya, Mueang Songkhla, Lampang 52000, Thailand
Keywords Myosin
Actin Freeze denaturation Kuruma prawn
Introduction Shrimp and prawn are very important fishery resources worldwide. With the aim of ensuring a controlled supply, both shrimp and prawn are extensively farmed, especially in Southeast Asian countries where their production by farming is steadily increasing. White leg shrimp Litopenaeus vannamei and black tiger shrimp Penaeus monodon are the two most abundantly cultivated shrimp species [1]. After harvest, some of the farmed shrimp are distributed as a fresh product, but the largest portion is distributed in the frozen state in various forms, i.e., whole, beheaded, peeled, etc. The best storage form for maintaining a high quality of shrimp meat for long periods is freezing. However, the quality of shrimp meat deteriorates even when frozen, although the process is very slow on account of the low temperature. Both the temperature and the type of packaging for frozen storage affect the deterioration rate. Generally, the lower the temperature for storage, the slower the protein denaturation, as has been established with fish meat [2], with the quality of the muscle-based
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