29D-23 |
Thermal denaturation of herring (Clupea harengus) protein and protein hydrolysates |
S. SATHIVEL1, C. Crapo1, P. J. Bechtel2, I. I. Negulescu3, and W. Prinyawiwatkul4. (1) Fishery Industrial Technology Center, Univ. of Alaska, Fairbanks, School of Fisheries & Ocean Sciences, 118 Trident Way, Kodiak, AK 99615-7401, (2) Subarctic Agricultural Research Unit, USDA-ARS-Pacific West Area, Univ. of Alaska, Fairbanks, 245 O'Neill Bldg., Fairbanks, AK 99775-7220, (3) School of Human Ecology, Louisiana State Univ. Agricultural Center, 125 Human Ecology Bldg., Baton Rouge, LA 70803-4200, (4) Dept. of Food Science, Louisiana State Univ. Agricultural Center, 111 Food Science Bldg., Baton Rouge, LA 70803-4200 The functional and physical properties of fish proteins (e.g., water holding capacity, gelation, foaming and emulsifying capacity) are altered by thermal denaturation. Differential scanning calorimetry (DSC) provides a direct method to study the thermal transition of protein. We developed both extracted protein and protein hydrolysates from herring and evaluated conformational changes using a DSC. The objective of this study was to investigate the thermal behavior of concentrated herring protein and hydrolysates by monitoring the peak temperature maxima (Tmax) and denaturation enthalpies using DSC. Both intact extracted proteins and hydrolyzed proteins were made from both herring heads and fillets. For the intact extracted protein the tissues were minced, water added (water:mince=1:1 V/W), then mixture heated at 85 C for 60 min after which the soluble protein was recovered and freeze-dried. For the hydrolyzed protein from herring heads and/or fillets were separately hydrolyzed at 50 C for 60 minutes using Alcalase (Novozyme). The enzyme was added at 0.5% (w/w) of protein content in the mince. The enzyme activity was terminated by increasing the temperature to above 85 C for 15 min, after which the soluble protein was recovered and freeze-dried. DSC was used to determine the (Tmax) and enthalpy of the fish protein powders. DSC thermograms of hydrolyzed protein powders from both fillet and head showed one endothermic transition (Tmax) at 83.5C and 63.6 C, respectively. Intact extracted protein powders showed multiple (Tmax) at 61.9, 67.3, 79.7, 85.2, 91.9, and 96.9 C for the head protein, and 42.6, 59.9 and 65.4 C for the fillet protein. The highest denaturation enthalpy was found in hydrolyzed herring head protein (82.7 j/g) whereas the lowest enthalpy (0.3 j/g) was found in the intact extracted herring head protein. Large differences were detected between the hydrolyzed and intact herring head and fillet proteins. This study reported information on thermal denaturation of protein powders from herring head and fillet portions, which is useful to predict the functionality and the potential use of thes protein powders.
Session 29D, Food Engineering: Thermal processes
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