Meat Quality Testing
Meat quality is normally defined by the compositional quality (lean to fat ratio) and the palatability factors such as visual appearance, smell, firmness, juiciness, tenderness, and flavor. The nutritional quality of meat is objective yet “eating” quality, as perceived by the consumer, is highly subjective.
|Testing||Quality Assurance||Quality Control|
|The process of executing a system with the intent of finding defects.||A set of activities designed to ensure that the development and/or maintenance process is adequate to ensure a system will meet its objectives.||A set of activities designed to evaluate a developed work product.|
Why quality testing of meat is important?
- To improve the quality of product
- Market shift from Quantity Oriented to Quality Oriented
- Consumer consciousness about health
- Safety of meat
- competitiveness of food production more dependent on the reliability of the safety and the quality of the food
- acceptability of the production procedures than on quantity and price.
- Sensory evaluation
- Physical testing
- Chemical testing
- Microbiological testing
It makes use of the senses to evaluate the general acceptability and quality attributes of the products.
Fig. 1: Areas of the tongue where taste buds and reception areas for different tastes are located
- Sense of sight is used to evaluate the general appearance of the product such as color, size, shape etc.
- Sense of smell for the odor
- Sense of taste for the flavor which includes the four basic tastes sour, sweet, bitter and salty
- Sense of touch for the texture either by mouth feel or finger feel
- In the simplest way of sensory testing it is useful to have an appropriate testing room available with lights, temperature and seating arrangements with individual testing compartments so as not to distract the members of the panel.
- Panel is composed of ten well trained panelists.
Common test methods used in sensory evaluation are:
- Paired comparison test for simple difference where two coded samples are presented to the panelists for evaluation on simple difference.
- Triangle test where three coded samples are presented at the same time, two are identical and the third is odd and the panelist is asked to identify the odd sample .Tests for simple difference and the triangle test are very useful methods for quality control and product development. Newly formulated products can be evaluated by determining if a simple difference exists between the new products developed and the old ones
- Hedonic scale rating test or acceptability test where samples are tested to determine their acceptability or preference. Hedonic scale rating can be used for internal factory testing, and this method is also suitable for market research by determining the consumer’s acceptance or preference for certain products.
Color of meat
“fresh” color – red for beef, veal for lamb products, pink for pork, and varying colors for chicken. Before the meat product reaches consumers, meat and poultry processors use color to monitor processing and ensure the quality and freshness of the meat
Another quality factor is smell. The product should have a normal smell. This will be different for each of the species (i.e. beef, pork, chicken), but should vary only slightly within the species. Any rancid or strange smelling meat should be avoided.
Meat should appear firm rather than soft. When handling the retail package, it should be firm, but not tough. It should give under pressure, but not actually be soft.
Juiciness depends on the amount of water retained in a cooked meat product. Juiciness increases flavour, helps soften meat – making it easier to chew, and stimulates saliva production in the mouth. Water retention and lipid content determine juiciness. Marbling and fat around edges helps hold in water. Water losses are from evaporation and drip losses. Meat aging can increase water retention and therefore increases juiciness.
Has been linked to several factors, such as the animal’s age, sex or the muscle location. One important way to tenderize meat is by aging. Carcasses are aged by holding them at refrigeration temperatures for extended periods of time after slaughter and initial chilling.
Flavour and aroma are intertwined to create the sensation the consumer has during eating. These perceptions rely on the smell through the nose and on the sensations of salty, sweet, sour and bitter on the tongue. Meat flavor is affected by type of species, diet, cooking method and method of preservation (e.g. smoked or cured)
Physical Test Methods:
- Acidity (pH)
- Water activity (aw)
- Water binding capacity
- Light intensity
- Texture. All routine physical testing can be carried out with portable instruments.
Important temperature control points are:
- 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)
- Water temperature in cooking vats (+75 to +78°C)
- Core temperature in meat products upon cooking/pasteurization (approx. +68/72°C)
- Sterilization temperature in autoclaves (above +100°C)1
based on the thermo-electrical effect. the two metals are exposed to different temperatures. On one welding point reference temperature is taken. The other welding point is exposed to the temperature to be measured. We take temperature reading on the instrument.
Why pH measurement is important?
pH measurement is useful for:
- Evaluation of meat quality for further processing, in particular the water binding capacity
- Control of ripening of raw fermented products, which is connected with drop in pH
- Control of acidity of ingredients such as brines, marinades etc
Portable instruments are battery driven and have glass electrodes.
Typical pH values for meat and meat products are:
|Product||pH value (range)|
|Meat mixes in jelly + vinegar added||4.5 to 5.2|
|Raw fermented sausage||4.8 to 6.0|
|Beef||5.4 to 6.0|
|Pork||5.5 to 6.2|
|Canned meats||5.8 to 6.2|
|Curing brines||6.2 to 6.4|
|Blood sausages||6.5 to 6.8|
|Muscle tissues, immediately after slaughter||7.0 to 7.2|
|Blood||7.3 to 7.6|
It is measured by Hygrometer. Hygrometers measure the relative humidity and are used in production and storage rooms of the meat industry. Recommended values for the relative humidity are:
|Meat boning and cutting rooms||45% to 60%|
|Meat packaging rooms||45% to 60%|
|Chilling rooms||85% to 95%|
|Storage / ripening rooms for meat||70% to 85%|
|Ripening rooms for raw fermented ham and sausages||80% to 95%
(depending on the
stage of ripening)
Water Activity Measurement:
The amount of free water available for the growth of microorganisms. Bacteria usually require at least aw 0.91 and fungi at least aw 0.71.
To check the stability of dry fermented products during their ripening to find out at which point the products remain stable at ambient temperature. Meat preservation for dried products (dried meat, meat floss etc.)
AW – meter:
Through evaporation an equilibrium of humidity in the small airspace above the product and the humidity of the sample is build-up and this is directly measured by means of a hygrometer built into the lid of the instrument .Pure water aw-value of 1. Typical aw in meat products (left) and limiting aw for the growth of microorganisms (right).
|Fresh meat||0.99 (0.99 to 0.98)||Pseudomonas||0.93||Most bacteria between
aw 0.91 – 0.96
|Cooked ham||0.97 (0.98 to 0.96)||E. coli||0.93|
|Raw-cooked sausages||0.97 (0.98 to 0.93)||Salmonella species||0.91-0.95|
|Liver sausages||0.96 (0.97 to 0.95)||Listeria||0.93|
|Blood sausages||0.96 (0.97 to 0.86)||Cl. botulinum types||0.91-0.95|
|Raw-fermented ham||0.92 (0.96 to 0.80)||Cl. perfringens||0.93-0.95|
|Raw-fermented sausages||0.91 (0.96 to 0.70)||Bacillus species||0.90-0.95|
|Dried meat||0.70 (0.90 to 0.60)||Lactobacillus||0.90|
Water holding capacity (WHC):
- role in meat processing.
- Low WHC results in separation of jelly and/or fat during heat treatment
The WHC can be measured using a glass compressorium (Fig. 429), where the sample of meat or batter is compressed onto a water absorbing sheet of paper. The larger the water infiltrated area on the paper, the poorer is the WHC of the meat/batter
Sensory testing (chewing) is sufficient . But for more accurate results we use instruments to test tenderness/toughness or homogenous/fibrous structure of meat and meat products. Instruments for texture measurement:
- The instrument shown in the photo, measures the shear-force necessary to cut through meat/meat products.
- Texture measurements are done by ripening, cooking etc
Simple Methods of Chemical Analysis:(Protein, fat, water, ashes:
Chemical analyses to determine the content of protein, fat, water and minerals (ashes) of processed meat products are carried out to establish the nutritive and economic value of the products. Weighed and ground sample is prepared for respective analysis.
(Microwave Drying) The difference in weight between the fresh and dried samples represents the water content
|Sample size||Approximate Drying Time|
|3 x 10g||3.5 – 4.5 min.|
|3 x 25g||7.5 – 9.5 min.|
|2 x 50g||8.5 – 11 min.|
Protein content: (Kjeldahl method)
Nitrogen compounds and then distilled and titrated to determine nitrogen quantitatively, with which the protein component can be calculated. In a simplified approach protein is not chemically determined, but can be calculated (approximately) as the remaining component, after water, fat and ashes content has been determined and subtract%. Only for meat
% Protein = 100% – (%water + % ash + % fat)
ether-extraction using the Soxhlet apparatus
Place the dried sample inside the soxhlet extraction tube connected to the soxhlet flask. Pour enough ether into the extraction tube. Extract for 10 hours, at 3-4 drops per second.
sample is placed in a constant weight porcelain crucible with cover.
- muffle furnace, and at a temperature of 600°C the sample is ignited for two hours.
- After ignition the crucible is placed in the oven to bring down the temperature for about 30 minutes ,then cool in a dessicator for another 30 minutes. Difference in weight is mineral content.
Microbiological Sampling and Testing:
- Contact method : The microbiological culture medium is put in direct contact with the surface of equipment or tools to be tested. The culture medium containing the microbes from the test surface is incubated e.g. at 30°C for 2 days. Each bacterium grows as a bacterial colony visible to the naked eye. Colonies can be counted to allow assessment of the degree of contamination.
- Swab method: Microorganisms collected by the swab technique are rinsed off with sterile water . The microbial content of the liquid is tested.
- Destructive methods: (for use on meat/meat products)A standardized sample is cut out (“destructive”) from the surface of meat or meat products, for example by using a sterile knife and metal frame.
Total Plate Count (using nutrient agar):
- Meat sample (10 grams meat + 90 ml sterile distilled water or 0.1% peptone water). Homogenize in stomacher. First dilution.
- Transfer 1 ml from first dilution (101) to second test tube (Test tube contains 9 ml. of sterile distilled water) (2nd dilution or 102) then from second test tube transfer 1ml to the third tube (3rd dilution or 103) and so on up to the 4th or 6th dilution.
- Inoculate and incubate at 37°C
- normal plates 25-250 counts
- plates with more than 250 colonies for all dilution – too numerous to count
- plates with no CFU. Report as less than 1 times the corresponding dilution used.
Selective Plate Count:
- Xylose lysine deoxycholate agar (XLD agar) is a selective growth medium used in the isolation of Salmonella, Macconkey agar for E. coli.
- BD LBS Agar (also known as Rogosa Agar) for lactobaccilus.