30D-10 |
Thermal analysis of Tilapia fish muscle: effect of NaCl and sucrose on denaturation temperature of osmotic dehydrated myofibrillar proteins |
M. MEDINA-VIVANCO1, P. J. Sobral, A. M. Sereno, and M. D. Hubinger1. (1) Department of Food Engineering, Faculty of Food Engineering, State University of Campinas, PO Box 6121, Campinas, 13083-970, Brazil Osmotic treatments have often been suggested as a preliminary step in conventional air drying operations.It is known, when working with fish/meat that solutes are incorporated in flesh muscular tissue. Such solutes are supposed to affect denaturation temperature (Td) and heat of denaturation (DHd) of the proteins present. The objective of this work was to observe the influence of sodium chloride and sucrose alone or combined on denaturation temperature and enthalpy of the proteins of tilapia (Oreochromis niloticus L.) fillet after immersion in aqueous solutions of those solutes. To achieve such objective, thermal behavior of fish fillet was studied in a temperature modulated differential scanning calorimeter from TA Instruments Inc. (MDSC 2920), operating in conventional way. Temperature and enthalpy calibrations were done using water and indium. In order to obtain samples with increasing solute concentrations skinless tilapia fillets were soaked in NaCl solution (26% w/w), sucrose solution (40% w/w) and a mixed solution of salt and sucrose (35.1/66.7 g of each solute per 100 g of water), for different times, at 20oC and at a product/solution ratio of 1/10. Moisture, salt and sugar contents were measured. Samples weighting 10 to 15 mg were placed in aluminum pans, hermetically sealed and scanned at 15 oC/min over the range of 15 to 90 oC. DSC thermograms obtained showed a consistent decrease of denaturation temperature (in the order of 5-7ºC) and denaturation heat with increasing salt content in the muscle. Thermal transitions of myosin were completely lost at elevated salt content. When soaked in pure sucrose solutions no significant effect in transition temperatures was observed. In the presence of both solutes salt effect was only slightly attenuated.
Session 30D, Food Engineering: Physical and chemical properties
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