Presentation on theme: "Physical and Chemical test methods for meat (physical evaluation) practical 9."— Presentation transcript:
Physical and Chemical test methods for meat (physical evaluation) practical 9
Meat evaluation There are some important parameters such as temperature, acidity (pH), water activity (a w ) and cooking loss. Other physical parameters are light intensity and mechanical testing for texture.
1-Temperature Storage: Meat and meat products requires low temperatures Chilling between -1 to +4°C Freezing between -18 to -30°C. Cooking Starting from a temperature of about 55°C-100°C needed for denaturation Canning: Meat requires temperatures above 100°C- at least 121°C, and for sterilized products where all micro-organisms are inactivated,.
Some important temp.: Refrigerated rooms (freezer -18°C to -30°C, chiller 0 to +7°C) Chilled meat (+4 to +7°C) Cutting rooms (+10 to +15°C) Curing rooms (+5 to +10°C) Water temperature in cooking vats (+75 to +78°C) Core temperature in meat products upon cooking/pasteurization (approx. +68- 72°C) Core temperature in meat products during sterilization (above +100°C)
2- Humidity The humidity of the air should be below the level which would cause vapour condensation on the surfaces of the meat Vapour condensation may enhance bacterial growth. Storage chillers for fresh meat require a balanced air humidity that does not cause wet surfaces on the meat with resulting accelerated bacterial growth.
Meat boning and cutting rooms45% to 60% Meat packaging rooms45% to 60% Chilling rooms85% to 95% Storage / ripening rooms for meat70% to 85% Ripening rooms for raw fermented ham and sausages 80% to 95% (depending on the stage of ripening) Recommended values for the relative humidity are:
3- Water activity (a w ) A certain number of micro-organisms are inhibited at a w 0.95, but other species are still able to grow. At a w 0.92 all bacteria groups are inhibited, but the growth of molds and yeasts is still possible.
Water holding capacity (WHC) a.Absorbent method : WHC plays a role in meat to be used for further processing. It is also important in meat batters, which have to undergo heat treatment. The WHC can be measured 1. Pressure test Using a glass compressor, where the sample of meat or batter is compressed on a water absorbing sheet of paper. The larger the water infiltrated area on the paper, the poorer is the WHC of the meat/batter. Absorbing zone have to be less than 1cm
2. Chemical method A meat sample (4 g) and 6 ml of 0.6 M NaCl solution is put into a tube. The tube is placed into a water bath for 10 min. Then, the tube is centrifuged at 4000 rpm for 15 min. The tube is poured into a volumetric cylinder in order to collect the separated fluid. The WHC is calculated using the volume of separated fluid (ml). W.H.C for red meat have to be less than 10% in calculation result
3. Cooking loss 20 gram of meat sample is placed in open aluminum boxe Cooked for 15 minute in the oven pre-heated to 200 C° The samples are dried with a paper towel (cooled for 30 min to 15 C° ). Total cooking loss is estimated on each sample as percentage ratio between cooked and raw weight. Cooking loss%, have to be in between 20-45% for well cooked red meat