Changes in calpain and calpastatin activities of osmotically dehydrated bovine muscle during storage after treatment with calcium.

Calpain and calpastatin activities were investigated in calcium-treated beef after osmotic dehydration. Dehydrated beef was soaked in 150 mM calcium chloride solution for 3 h, and then stored for 48 h at 3-4 °C. The untreated sample (control) was soaked in deionized water for 3 h instead of calcium chloride solution, after osmotic dehydration. The increase and decrease in the relative activity of crude calpain were observed in the untreated and the calcium-treated meat, respectively, during the storage. When the crude calpains were subjected to DEAE-Sephacel column chromatography, it was found that µ-calpain activity decreased rapidly during the storage in the untreated meat, whereas there was almost no change in the activity of m-calpain during the storage. The decrease of calpastatin activity was moderate compared with the decrease of µ-calpain activity. In the calcium chloride-treated meat, however, no µ-calpain nor calpastatin activities was detectable after 48 h at cold-room temperature, and m-calpain activity after 48 h had decreased to 6.1% of its activity immediately after thawing. It was concluded that 150 mM calcium chloride treatment after osmotic dehydration was sufficient to introduce calcium ions into the meat. In the presence of sufficient calcium, autolysis of calpains and proteolytic degradation of calpastatin, which eventually related to the rate of decrease in calpain and calpastatin activities, clearly seem to be related to a decrease in meat toughness.

Changes in immunoelectron microscopic localization of cathepsin D in muscle induced by conditioning or high-pressure treatment.

Changes in the localization of cathepsin D in postmortem and pressurized rabbit muscles were investigated by immunoelectron microscopy. The anti-cathepsin D monoclonal antibody strongly labeled a large vesicle in a subsarcolemmal part of the cell , which strongly suggests that this is the primary lysosome. The liberation of the cathepsin D entrapped in the lysosomes in the muscle prepared immediately after death proceeded with the progress of the conditioning. The release of almost all cathepsin D from the lysosomes and its absorption on the myofibrils were observed in the muscle conditioned for 14 days. The accumulation of lysosomes having various volumes and shapes accompanied with the disruption of myofibrillar structure was also observed. The liberation of cathepsin D from the lysosomes can be attributed to the modification of membranes permeability of the lysosomes during conditioning. When the muscle was pressurized at 100 MPa, the modification of the round shape of the lysosome was observed. With the increase of the pressure applied to the muscle, the release of cathepsin D from the lysosome due to the disruption of membrane was accelerated, and absorption of the released cathepsin D on the myofibrils was observed. From the results obtained, it was clear that the changes in the localization of cathepsin D accompanied with the modification of lysosomes induced by the brief exposure to high pressure were drastic in comparison with that in the muscle during conditioning.

Meat tenderization by calcium chloride after osmotic dehydration.

In this study, meat was tenderized by dipping the meat in a calcium-containing solution after osmotic dehydration. Dehydrated meats were dipped in a 150 mM calcium chloride solution for 3 h, and after that stored for 24, 48, and 168 h at 3 ∼ 4°C. Then, meat was subjected to texture measurement, sensory evaluations, biochemical analysis and histological observations. A gradual decrease in the firmness and higher tenderness sensory scores were observed in the meat treated with calcium chloride as compared with the untreated meat. Few differences were observed in water holding capacity by treatment at any stage of storage. A gradual increase in the myofibril fragmentation from the calcium chloride-treated meats was observed throughout the storage compared with the controls. Broadening of the I band and a disordered Z-line were observed in the treated meat. The deformation of the honeycomb-like structure of the endomysium was also observed in the treated samples. Therefore, the dipping in 150 mM calcium chloride solution after dehydration can be applied to improve meat tenderness without detrimental effects on other palatability and quality traits.

Meat tenderization by proteolytic enzymes after osmotic dehydration.

The treatment of proteolytic enzymes is one of the popular methods for meat tenderization. In this case, it is very important how to introduce the enzymes into the meat cut. This paper describes meat tenderization by dipping the meat cut in a solution containing proteolytic enzymes after contact-osmotic dehydration. After the dehydration of each piece of meat from culled cow for 18 h by contact-dehydration sheet, each sample was dipped for 3 h in a solution containing papain or proteinases from Aspergillus traditionally used for soysauce production in Japan. It was stored at 3∼4°C for 24, 48 and 168 h, and subjected to texture measurement, sensory evaluations, biochemical analysis and histological observations. The penetration efficiency of the enzyme solution (of around 80%) after the contact-osmotic dehydration seemed to be sufficient. A marked decrease in hardness by texture measurements was observed in the meats treated with proteolytic enzymes and higher sensory scores for tenderness were observed in the meats treated with enzymes as compared with the untreated meat. The papain-treated meat received the highest score in tenderness, but the scores given to juiciness and taste were lower than that of the control. The rapid increases of the fragmentation of myofibrils from the enzyme-treated meat were observed at first 24 h of storage as compared with that of the control. Remarkable degradation of myosin molecule in the myofibrils from the enzyme-treated meats was observed on SDS-PAGE profiles. Considerable degradation of myofibrilar structure especially due to proteolytic removal of Z-lines, was observed among the myofibrils from enzyme-treated meats by electronmicroscopy. The remarkable deformation and disruption of honeycomb-like structure of endomysium were also observed in the meats treated with enzymes. From these results, it was shown that treatment after osmotic dehydration, was effective in tenderizing.