PHYSICOCHEMICAL CHANGES OF SARDINES (SARDINA PILCHARDUS) AT –18C AND FUNCTIONAL PROPERTIES OF KAMABOKO GELS ENHANCED WITH Ca2+ IONS AND MTGase
The physicochemical changes in sardine flesh during frozen storage at −18C were studied in terms of salt-soluble protein extractability, nonprotein nitrogen (NPN), pH, myosin and actin denaturation enthalpies, color, fatty acid methyl esters and proteolytic activity in surimi wastewaters. Furthermore, the functional properties of the produced kamaboko gels were studied based on two experimental factors: (1) frozen storage time (five levels) and (2) various additives (three levels). The NPN and pH changes showed a similar trend (P < 0.05) throughout the storage. Myosin transition enthalpy significantly decreased throughout the storage and strongly negatively correlated with storage time (r = −0.987). Color deterioration was evidenced by the decrease in lightness (L*) and whiteness index (WI) as well as the increase in greenness (−a*) and yellowness (+b*) of sardine mince (P < 0.05). Protease activity in surimi wastewaters increased on day 20, due to either sample variation or better extraction, and showed a downward trend thereafter. A gradual increase was noticed in gel hardness and cohesiveness after 10 days of storage due to protein aggregation. Hardness and cohesiveness, as well as L* and WI, were positively affected by the addition of CaCl2 and microbial transglutaminase (MTGase), while springiness was only affected by MTGase addition. Overall instrumental evaluation showed that kamaboko gels of acceptable quality could be produced from sardines frozen stored up to 20 days. PRACTICAL APPLICATIONS
The use of alternative fish species in order to obtain surimi of good gel-forming ability is one of the aims of the fishing industry. Because of its high potential for capture and its low price, there is a sustained interest at present in small pelagic fish species. In Greece, small pelagic fish species are mainly processed by salting, drying, smoking and canning, and preferably when these species are large and fatty. However, these species are often too small for processing and thus have no commercial value, particularly around the spawning season (low lipid content), and are usually being dumped. Thus, in Greece, the lack of utilization of small fish may also have an adverse effect on the environment.
Document Type: Research Article
Affiliations: 1: Alexander Technological Educational Institute (ATEI) of ThessalonikiSchool of Food Technology and NutritionDepartment of Food Technology57400 Thessaloniki, PO Box 141, Greece 2: Faculty of TechnologyUniversity of LincolnBrayford Pool, Lincoln LN6 7TS, U.K.
Publication date: 2008-06-01