Changes Of Physicochemical And Protein Functional Properties During Rabbit Ageing

Rabbit meat is a typical three-high and three-low food, with high protein, high lysine, high digestibility, low fat, low cholesterol, low calorie of nutrition health care function. Regular consumption of rabbit meat can alleviate the incidence of diseases such as obesity, hypertension and coronary heart disease, in addition, it also has a beauty and intelligence functions. China’s meat production and export volume ranked the forefront of the world, and production and sales volume was continuing to increase. With the improvement of people’s living standards and health consciousness, consumption of rabbit meat has a lot of room to grow. Postmortem maturity is the transformation process of muscle to meat. After mature tenderization, the meat is soft and flexible, better color, good flavor, greatly improving the eating quality of meat. The paper was based on rabbit rear legs and longissimus dorsi as experimental materials, examined the changes rules of various physical and chemical properties, volatile flavor compounds and myofibril protein functional properties during postmortem ageing, for us to develop mature technology(time) of rabbit meat to provide certain theoretical basis. The main results are as follows:1. During rabbit postmortem ageing, some chemical indexes such as the pH, glycogen, MFI, TVB-N and TBARS value have taken place significant changes, and different anatomical location has some differences. Rabbit rear legs and longissimus dorsi reached the maximum rigidity value at24h and48h respectively, which the pH value continued to rise after72h but the difference is not significant (P>0.05). The average content of glycogen were reduced7.58mg/100g at the24h. In the two anatomical locations, MFI, TVB-N and TBARS value are a trend of increase gradually with ageing time increasing, in which three indexes have significantly positive correlation between (P<0.01). The larger the MFI value, the better the meat tenderness. Before ageing72h, the content of TVB-N in the two anatomical locations are less than 15mg/100g, indicates fresh meat. Ageing168h, TBARS values were greater than the critical value of fresh meat fatty defeat in the two anatomical locations.2. During rabbit postmortem ageing, the shear value, cooking loss, drip loss and color of different anatomical location meat has some differences. Ageing time has significant impact on the color, shear value, cooking loss and drip loss of rabbit meat. During the period of ageing, there is a certain correlation among different physical indexes, including shear value and cooking loss exists very significant positive correlation (P<0.01). With the extension of postmortem ageing time, color values are in decline, and drip loss increases gradually. Shear value and cooking loss respectively reached the maximum value at24h and48h of rabbit rear legs and longissimus dorsi, at this time rabbit get poor quality. As rabbit meat entered rigor off and ageing stage, the meat become suitable for processing with the meat tender, good water-holding capacity and flavor characteristics. When ageing168h, the meat with darker color, surface slightly sticky and edible reduced characteristics.3. During postmortem ageing of rabbit detected six categories volatile flavor compounds in different anatomical locations, including aldehydes, ketones, alcohols, esters, hydrocarbons and furans, which the proportion of aldehydes was the highest, followed by alcohols and hydrocarbons, ketones, esters and furans compounds were low proportion and less in the share of volatile substances. Through comparison of raw and cooked meat samples during the process of ageing resulted that:at the same ageing time point, the relative contents were obvious differences of six categories volatile compounds in different anatomical locations, and relative content of volatile flavor compounds in the same anatomical location were significant difference at different ageing time point. Both relative content and type of volatile flavor compounds have undergone some changes in two anatomical locations cooked meat samples, the type of volatile flavor compounds showed an increasing trend in cooked meat samples, and relative content of most volatile flavor compounds higher than that of raw samples. A higher content of volatile flavor compounds in rabbit such as pentanal, hexanal, heptanal, octanal, nonanal, Z-2-heptenal, E-2-octenyl aldehyde, benzaldehyde, fourteen aldehydes, octadecyl aldehyde,2,3-octanedione, pentanol, octanol,1-octen-3-ol, limonene, styrene, pentyl cyclopropane, pentadecane and so on.4. During postmortem aging of rabbit, functional properties of myofibrillar protein changed in certain degree, and there were some differences between the different anatomical locations. With the extension of postmortem ageing time, myofibrillar protein of the rabbit rear legs and longissimus dorsi in solubility, emulsifying activity index and emulsion stability, foaming capacity and water retention of gel were first decreased and then increased, respectively reached a minimum value in postmortem24h and48h; but turbidity, foam stability, surface hydrophobicity and gel hardness were increased first and then decreased, and in post-mortem24h and48h reached a maximum value respectively. Myofibrillar protein of rabbit rear legs and longissimus dorsi appeared two distinct denaturation temperature point at different ageing time in the heat flow curve, both myofibrillar protein of the two anatomical locations, Tmax peak were decreased in postmortem0-24h and0-48h respectively, which indicated that the properities of myosin were changed, thermal stability was lowered; with the increasing of ageing time, denaturation temperature of myosin increased, damaging protein network structure required more calories. The Tmaxpeakll of rabbit longissimus dorsi muscle was not significant difference with the extension of postmortem ageing time (P>0.05), which described that postmortem actin was relatively stable. The G’of myofibrillar proteins in different anatomical locations of the rabbit after maturation have experienced a trend of increase-decrease-increase, the G’of myofibrillar protein in rabbit longissimus dorsi muscle was greater than that of rabbit rear legs. At85℃, the G’of rabbit rear legs and longissimus dorsi myofibrillar protein respectively reached a maximum value at24h and48h, which was consistent with the ageing time of maximum gel strength.5. Can be concluded from this experiment, the rabbit rear legs and longissimus dorsi respectively reached the maximum rigidity at24h and48h, adequate ageing time was72h and96h respectively. From a variety of factors considered, the better ageing time of the whole carcass was72h, meanwhile, the meat tenderness, water retention, flavor and functional properties of myofibrillar protein is better suitable for processing.