Microstructure and instrumentally measured textural changes of rainbow trout (Oncorhynchus mykiss) gravads during production and storage
Article first published online: 16 JUN 2009
Copyright © 2009 Society of Chemical Industry
Journal of the Science of Food and Agriculture
Volume 89, Issue 11, pages 1942–1949, 30 August 2009
How to Cite
Michalczyk, M. and Surówka, K. (2009), Microstructure and instrumentally measured textural changes of rainbow trout (Oncorhynchus mykiss) gravads during production and storage. J. Sci. Food Agric., 89: 1942–1949. doi: 10.1002/jsfa.3678
- Issue published online: 6 JUL 2009
- Article first published online: 16 JUN 2009
- Manuscript Accepted: 12 MAY 2009
- Manuscript Revised: 23 MAR 2009
- Manuscript Received: 16 OCT 2008
BACKGROUND: Gravad fish belong to a group of low-processed products obtained from fresh fish by rubbing fillets with a mixture of sugar and salt and then placing them in cold storage. Little is known about changes in the tissue during the production and storage of gravads. The aim of the present study was to investigate the microstructural and textural changes in rainbow trout (Oncorhynchus mykiss) gravad during processing and vacuum storage at 3 °C and −30 °C.
RESULTS: Microscopic observations of gravad showed greater compactness of structure when compared with raw trout muscle, characterised by the disappearance of the divisions between adjoining myofibrils in gravad. Freezing, on the other hand, caused the myofibrils to again become more clearly distinguishable despite being partly agglomerated into lamellae. The above changes in structure were accompanied by changes in the textural and rheological properties of the product. It was observed that the texture profile (TPA) changed, resulting in an increase in the cohesiveness and chewiness of the gravads when compared to the raw fillets. There was also a lowering of stress decay during the relaxation test and a decrease in the value of the storage modulus (G′) as analysed by oscillatory rheometry. Further changes observed during storage were mainly concerned with an increase in the hardness and chewiness of gravads.
CONCLUSION: Gravading significantly changes the rainbow trout fillets by making the microstructure more compact. This process is accompanied by changes in texture and rheological properties, which next are running during the storage of a chilled or frozen product. These changes are significant enough for potential consumers to be made aware of the fact that the texture of the product changes considerably during its shelf life. Copyright © 2009 Society of Chemical Industry