Studies On The Properties And Storage Stability Of Crisp Grass Carp Muscle

Grass carp(Gtenopharyngodon idellus) is one of the freshwater fish which occupied the largest yields in China. The grass carp after a breeding of making grass crap muscle crisp was known as "crisp grass carp(Ctenopharyngodon idellus C. et V)". A significant difference was observed in microstructure and textural properties between grass carp and crisp grass carp, which was appreciated by customers because of its crispy taste. The changes of the microstructure, nutritional ingredient and texture proporties of the crisp grass carp muscle during crisping breeding and thermal, textural properties and storage stability of muscle were studied, which provides a theoretical basis for processing and storage of crisp grass carp. The results included the following:(1)Differences in muscle and muscle fiber of grass carp and crisp grass carp were observed and studied. After the crisping breeding, the muscular diaphragm between muscle bundle were increased, muscle bundle were arragened tight; collagen protein content of perimysium from crisp grass carp were higher than grass carp, which were seen by HE staining, collagen protein staining. After the crisping process, the length of myocomma from myofibril increased by the 1.90μm to 2.04μm, the dark band had no change, length of the light band were increased by 40%, the area of myofibril also increased by the 2.27μm2 to 3.15μm2, increased by 39%, which were seen by TEM(transmission electron microscope).(2)The changes of muscle nutrients composition and texture during the crisping breeding were studied. After crisping breeding, the solid materials, protein and lipid contents of crisp grass carp muscle increased. The protein contents of back and oabdominal muscle increased by 1.99%,0.68%, while the fat contents of back and oabdominal muscle increased by 2.22%,2.15%, respectively. The contents of water-soluble, salt-soluble and insoluble protein of back and oabdominal muscle were increased by 0.25%,1.47%,0.68% and 0.70%,0.40%,0.86%. Besides, TAA, EAA, DAA and EAAI of crisp grass carp was a little higher than grass carp. The primary fatty acids were palmitic acid, oleic acid and linoleic acid. The majority of fatty acid were unsaturated fatty acid, while crisp grass carp muscle had a higher content (70.52%) of unsaturated fatty acid than grass carp (65.04%). The hardness and chewiness of cooked crisp grass carp were notable increased.(3)Thermo-physical properties of grass crap and crisp grass crap muscle, effects of NaCl, sucros on thermo-physical properties of crisp grass crap meat were determined.The freezing phase transition range, thawing phase transition range, freezing point, apparent specific heat, enthalpy at the freezing point of grass crap and crisp grass crap muscle were-16.7～-15.1℃and-12.5～-11℃,-2.6～0.0℃and-1.9～0.1℃,-0.4℃and-0.2℃, 124.97J/g·℃and 130.56J/g·℃,357.89J/g and 305.57J/g, respectively. As the contents of the NaCl increased, the phase-transition temperature shifted to the lower temperature range, meanwhile both the apparent specific heat and enthalpy at the freezing point decreased. As the contents of the sucrose increased, freezing peak shifted to high temperature, melting peak had little change, while the apparent specific heat and enthalpy at the freezing point also decreased. NaCl played a leading role when sucrose-NaCl mixture was added.(4) The influence of different storage-temperature on the texture and stability of fat and protein of crisp grass carp muscle were studied. During storage the leaching of myofibrils, the the activity of Ca2+-ATPase, T-SH and A-SH content decreased with the increase of time. While SoANS increased with the prolong of time. However, the changes due to the variation of temperature differences. During storage at 5℃the total collagen content of crisp grass carp muscle decreased, while during storage at-0.5℃,-18℃it was not significantly reduced. The pepsin-soluble collagen make up the majority of collagen, acid-soluble collagen didn't degradate during storage. During storage at 5℃and-0.5℃, the value of TBA increased,while storage at-18℃, the value of TBA showed little increase after 140 days.After storaged at 5℃,-0.5℃and-18℃, the hardness, chewiness of cooked crisp grass carp fillets significantly decreased with the extension of storage time. Cooked crisp grass carp fillets storaged at-0.5℃maintained its texture properties better than 5℃and-18℃.