Effect of LTLT heat treatment on cathepsin B+L activity and denaturation of myofibrillar proteins of pork

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Title: Effect of LTLT heat treatment on cathepsin B+L activity and denaturation of myofibrillar proteins of pork
Author: Dominguez-Hernandez, Elisa
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Food and Environmental Sciences
Publisher: Helsingin yliopisto
Date: 2015
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-201510193744
Thesis level: master's thesis
Discipline: Food Science
Food Science
Food Science
Abstract: The aim of this project was to study the physical and chemical changes in the myofibrillar protein fraction during low-temperature long-time (LTLT) heat treatment of pork, in relation to cathepsin activity and evolution of tenderness. Porcine Longissimus dorsi muscles were cut, vacuum packaged and cooked in water baths at 53, 58, 63, 68 and 73°C. The process was monitored at: 1, 8 and 24h. Allo-Kramer shear force (AKSF), residual activity of cathepsin B+L, surface hydrophobicity (SH) and particle size of myofibrils were measured. Results showed that toughness decreased markedly between 53°C and 63°C and later increased to 73°C. Toughness also decreased with time. Myofibrillar SH, increased with temperature, but not with time, indicating aggregation and/or gelation. Treatments with low AKSF had smaller particles, suggesting that meat was easier to break, both macroscopically and microscopically. The high associated catheptic activity could be the reason for the weakening of myofibrils. They also might be able to prevent their aggregation and transition into a hard compact gel. As temperature increases, denaturation-aggregation-gelation overcomes proteolysis and bigger particles were detected. In conclusion, LTLT sous-vide cooking (53 and 63°C) allows the control of short term changes in myofibrils (so they do not toughen) and permits the slow ones (proteolysis) to decrease toughness of prime cuts.
Subject: Sous-vide
particle size
shear force

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