VM 561 Characteristics of Meat Animals PDF

1. CHARACTERISTICS OF MEAT ANIMALS AND DETERMINANTS OF MEAT QUALITY VM 561 (VET PUBLIC HEALTH II) Helena A Ngowi Department of Veterinary Medicine and Public Health Sokoine University of Agriculture, Morogoro, Tanzania April 2024...

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CHARACTERISTICS OF MEAT ANIMALS AND DETERMINANTS OF MEAT QUALITY VM 561 (VET PUBLIC HEALTH II) Helena A Ngowi Department of Veterinary Medicine and Public Health Sokoine University of Agriculture, Morogoro, Tanzania April 2024 1  INTRODUCTION Learning objectives Upon completion of this topic, students should be able to: Describe the characteristics of meat animals Discuss the determinants of meat quality Describe various methods for meat quality control (sensory, physical, chemical, and biological) Reference Book Meat Hygiene - Gracey et al Read Chapter 1 – The Food Animals 2  MEAT AND MEAT ANIMALS Meat - all parts of an animal that are intended for, or have been judged as safe and suitable for, human consumption (CAC/RCP 58-2005) Common meat animals include: – Domestic ungulates (bovine, porcine, ovine, caprine, equine) – Domestic birds (poultry) – Lagomorphs (hare, rabbits, pikas) – Farmed game – Farmed game birds – Wild games (mammals and birds) – Other animals as otherwise specified by the competent authority 3 MEAT ANIMALS … Domestic ungulates 4 MEAT ANIMALS … Domestic birds 5 MEAT ANIMALS … Lagomorphs 6 MEAT ANIMALS … Farmed game 7 MEAT ANIMALS … Farmed game birds 8 MEAT ANIMALS … Wild game 9  NORMAL CHARACTERISTICS OF MEAT There are basically two types of meats: – Red meat (sometime known as dark meat) – White meat Colour difference is due to variations in muscle activity, which in turn influences the muscle pigment (myoglobin) 10 NORMAL CHARACTERISTICS OF MEAT … Details on the colour development mechanisms can be found elsewhere in the literature Red meat White meats ? 11 NORMAL CHARACTERISTICS OF MEAT … There can also be great variation within one type of meat because of various factors (including animal nutrition). For example, different varieties of fish Tilapia Salmon 12 NORMAL CHARACTERISTICS OF MEAT … These are also normal fish colours 13 NORMAL CHARACTERISTICS OF MEAT … Meat colour variation can also occur within an individual animal For example, the thigh and leg muscles of chicken are darker than the breast and wing One of the reasons is variation in muscle activity between the different parts of the animal 14 NORMAL CHARACTERISTICS OF MEAT … Knowledge on the variation in the normal colour and other characteristics of different meats is very important for judging the quality of meat and meat products 15  MEAT QUALITY ATTRIBUTES The quality of any type of meat and meat product can be defined based on two major aspects: (1) Safety (2) Eating quality 16  MEAT QUALITY ATTRIBUTES … (1) Safety aspect The meat should not contain any harmful microorganisms or other unfavourable substances Obvious signs of a healthy animal are: - Quick and smart appearance - Well-disposed body reflexes even when resting - Move easily and steadily - Normal health parameters (e.g. cardinal parameters) Animals in advanced state of pregnancy have their blood contaminated with foetal waste materials 17  MEAT QUALITY ATTRIBUTES … (2) Eating quality aspect The eating quality of meat/meat product as for other food products is defined by the consumer: – Freshness; – Proportion of lean meat to fat; – Palatability (texture & consistence, juiciness, good flavour); – Appropriate use of additives and extenders (for processed) 18  MEAT QUALITY ATTRIBUTES … (2) Eating quality aspect … Preferences on meat eating qualities can differ greatly between individuals and contexts. For example, In most tropical countries, mature animals are preferred for slaughter because: - Their meats fit well with most food preparations - Most people prefer chewable rather than tender meat - Taboos against slaughter of younger animals In many temperate countries, meat from young animals may be the most preferred 19  MEAT QUALITY CONTROL General meat inspection provides an initial step towards meat quality control by screening out unacceptable meat that can be detected during an eye- and-knife examination of the meat (our main focus) Nevertheless, an actual meat quality control uses approved techniques to ascertain the quality of meat or meat product The application of quality control on a regular basis is regarded as necessary for all types of meat plants 20  MEAT QUALITY CONTROL METHODS There are different methods of testing the quality of meat or meat product Depending on the accuracy needed, the methods can be simple or more complicated needing more sophisticated devices In order to inform consumers and processors about the quality, simple and fast methods are most suitable in most cases 21 MEAT QUALITY CONTROL METHODS … However, exact details on residues, toxins and special food components can only be obtained through specialised laboratories Meat quality control methods can be classified into: – Sensory (organoleptic) evaluation – Physical test methods – Chemical analysis – Microbiological examination We outline here basic methods of quality control used in connection with handling and processing of meat 22 MEAT QUALITY CONTROL METHODS … Although basic methods are simple and will in some cases only provide approximate results, they may help to improve the: – quality of products – quality consciousness of staff – good manufacturing and hygienic practices in general The following mainly refer to the basic methods of quality control used in connection with handling and processing of meat 23 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality Consists of describing the attributes of meat and meat products, which can be perceived by natural sense organs Sense of sight is used to evaluate the general appearance of the product such as colour, size, shape, cleanness, etc. Sense of smell - odour Sense of taste - flavour which includes the four basic tastes sour, sweet, bitter and salty 24 Sense of touch - texture either by mouth feel or finger feel. MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Sensory evaluation can be performed by one individual or more objectively by a panel of well trained individuals (usually employees of the meat plant) The way consumers or processors check the appearance of meat is subjective. E.g. lean vs fat meat 25 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Sensory evaluation of processed meat will help recognise special product treatments (e.g., chilling, cooking, smoking, drying, …) An ideal panel is composed of ten (or fewer) well trained panelists who are knowledgeable at sensory testing 26 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Only people with good sensory capability, should be chosen in order to find out differences in colour, texture, flavour and taste All panelists must use proven and identical test methods in order to make their results comparable Each panelist is given a score-sheet, where they mark their findings Score-sheets of the team are evaluated and a test result for each individual product is produced based on multiple observations 27 Food sensory evaluation panel 28 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Common test methods used in sensory evaluation are: 1. Paired comparison test for simple difference Two coded samples are presented to the panelists for evaluation on simple difference 2. Triangle test Three coded samples are presented, two are identical and the third is abnormal and the panelist is asked to identify the abnormal sample 3. Hedonic scale rating test or acceptability test 29 Samples are tested to determine their acceptability or preference MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Skilled graders are able to classify different carcasses by checking the size, the volume of the muscular tissue, fat layers … Sensory evaluation methods can be of great value in most developing countries where no sophisticated methods are available 30 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Colour Fresh meat surfaces that have been in contact with air for only a short period turn into bright red colour because of the influence of oxygen in the air (Oxygen + Myoglobin) In the absence of oxygen, the meat remains or become dark red Meat which is in the process of losing its freshness no longer shows bright red colour even when intensively exposed to air 31 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Consumers prefer tender and juicy meat The best way to examine the consistency of meat is by chewing 32 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Smell and taste (aroma and flavour) Smell and taste are related to each other somehow, thus they have to be evaluated together for the reliable determination of product’s flavour The smell of fresh meat is slightly acidic, which increases with time because of formation of acids such as lactic acid Spoiling meat has unpleasant odour The freshness of meat is generally indicated by its smell and appearance 33 MEAT QUALITY CONTROL METHODS … 1. Sensory (organoleptic) evaluation of meat quality … Smell and taste (aroma and flavour) … Overall flavour is affected by spices and those compounds produced by ripening or heat treatment Test panelists should not smoke or eat spicy meals before starting the test, and should rinse their mouth frequently with warm water during the test 34 MEAT QUALITY CONTROL METHODS … 2. Physical test methods Physical test methods focus either on the: – Actual condition of meat and meat products or – Conditions around the meat or meta product (e.g. storage room, …) Physical test methods are easily applicable, though they need use of equipment Temperature Storage of meat and meat products requires low temperatures: – Chilling (-1oC to +4oC) retards microbial growth – Freezing (-18oC to -30oC) inhibits microbial growth 35 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Cooking of meat requires high temperatures: – 55oC to 100oC (denaturation) – Canning of meat requires temperatures > 100oC – Temperatures of ≥ 121oC are required to sterilise the product Thus different temperatures are required for different purposes Thermometers or other temperature recorders are used to monitor temperatures 36 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Temperature … Glass thermometers should not be used in direct contact with the meat because they may break Thermometers are most useful when permanently fixed to walls of chillers, production rooms, cooking equipment or autoclave Digital thermometer Electronic thermometer Digital thermometer 37 Measuring temperature of meat directly 38 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Humidity In some special field of meat processing and storage, air humidity is of importance Vapour condensation may enhance bacterial growth Storage chillers require humidity of around 70% to avoid evaporation and wetting on the surface of the meat Generally, there are different requirements for different purposes 39 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Humidity … Suitable hygrometers (or other devices) are required for the exact measurement of humidity 40 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Water activity Water activity (aw) = free water available in the food product It is that water in the food product that microbes can utilise. It ranges from 0 (no water available) to 1 (all water is available) Microbes need a certain degree of moisture to grow in food The lowest aw permitting growth of spoilage organisms are: – Normal bacteria 0.91 – Normal yeasts 0.88 – Normal moulds 0.80 41 – Halophilic bacteria 0.77 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Water activity … Dried meat such as biltong reaches sufficiently low aw to be shelf-stable (the reduction of aw should be as fast as possible) The proper way to determine aw is to measure the humidity of the remaining air in a hermetically closed small cabinet, which is to a certain extent filled with the product sample aw meter Meat 42 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Water activity … After a short time a hygroscopic equilibrium between the sample and the surrounding air will be reached If the test has been carried out at exactly 25oC, after 2 hours the reading of the instrument corresponds to the actual aw of product If this temperature cannot be maintained, corrective calculations will be necessary (find out) aw meter Meat 43 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Examples of aw values for different meat products Meat product aw Fresh raw meat 0.99 – 0.98 Cooked harm 0.98 – 0.96 Frankfurter-type sausages 0.98 – 0.93 Liver sausage 0.97 – 0.95 Raw cured harm 0.96 – 0.80 Dry sausage (salami type) 0.96 – 0.70 Dry meat 0.75 – 0.50 44 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Airtight closure of cans For shelf-stable canned meat products, two aspects are important from the microbiological standpoint: – Sterilisation of the product (to kill microbes and their spores) – Hermetically sealing of the can (to avoid re-contamination) Cans should be checked from time to time for any perforation A simple method is to use an air-pump with a special device to penetrate the can. Pump the air into an empty can An inflated can is dipped into water to see if there is any 45 indication of perforation (E.g. air bubbling) MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Weight difference Considerable amount of water is lost from meat during handling, processing or storage because of evaporation or dripping This loss result in weight difference Unpacked meat and meat products are especially subject to considerable evaporation losses During cooking of meat, losses of 30 – 35% are unavoidable 46 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Weight difference … Information of weight losses is of economic and tech importance Weight losses can easily be measured using scales (before and after assessment) 47 MEAT QUALITY CONTROL METHODS … 2. Physical test methods … Salt concentration in brines Brines are used in some types of meat processing Brines contain mostly salt, sugar and nitrite dissolved in water Salt should not exceed 2.5 – 3% in cooked cured products and 4.5 – 5% in raw cured and dried products Salimeter is an equipment used to measure salt concentration in the brine. The equipment is dipped into the brine and the level of 48 sinking examined MEAT QUALITY CONTROL METHODS … 3. Chemical methods Chemical characteristics of foods are related to the product itself and refer primarily to the content of specific substances of food The test methods are generally complicated and need sophisticated equipment However, there are also some simple, quick and accurate methods as discussed below 49 MEAT QUALITY CONTROL METHODS … 3. Chemical methods … pH measurement The pH-value or acidity of meat is important in relation to the meat’s microbiological and keeping quality In a live animal the muscle tissue pH is about 7.0 – 7.1 At around 24 hours after slaughter the pH goes to the lowest level of about 5.6 – 5.8 (read about the mechanism behind) pH of meat is not uniform in different carcasses or parts of a carcass 50 MEAT QUALITY CONTROL METHODS … 3. Chemical methods … pH measurement … There are two types of abnormal reactions with regard to pH in meat: 1. The pH may fall too fast (within 1 hour to the lowest normal level) 2. The pH may fail to fall. Thus remaining in the neutral point The 1st phenomenon occurs only in pigs and results to pale soft exudative (PSE) meat (not suitable for sausages) The 2nd phenomenon occurs in beef and pork results to dark firm and dry (DFD) meat (can be good for cooked meat products because it has good water holding capacity) 51 MEAT QUALITY CONTROL METHODS … 3. Chemical methods … pH measurement … pH measurement is of particular importance for the selection of raw materials for meat processing pH is measured using a pH meter on the surface of the meat or the meat itself (by pushing the sensor into the muscle or by means of an incision using a knife) pH meter 52 Measurement of pH of meat 53 MEAT QUALITY CONTROL METHODS … 3. Chemical methods … 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 54 MEAT QUALITY CONTROL METHODS … 3. Chemical methods … pH measurement … 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 55 MEAT QUALITY CONTROL METHODS … 3. Chemical methods … Moisture/fat/protein determination Essential for the evaluation of quality of different meats and meat products Various sophisticated and expensive methods For routine analyses, where not necessarily highly accurate but reliable results are needed, cheaper and less complicated methods can be applied Needs a specially designed laboratory scale + some other devices 56 MEAT QUALITY CONTROL METHODS … 3. Chemical methods … Moisture/fat/protein determination … Procedure: 1. Homogenise the sample; 2. Weigh the sample (W1); 3. Fast dry the sample using infrared beam or microwave oven; 4. Weigh the dried sample (W2). Weight of water (moisture) = W1-W2) 5. Dissolve the fat using a fat-extracting liquid (e.g. methanol); 6. Remove the fat together with the extracting liquid; 7. Evaporate the solvent; 8. Weigh the residue (W3) = weight of the fat content; 9. Burn the residue in a muffle furnance; 10. Weigh the residue after burning (W4) = weight of ash (minerals) 57 Moisture (%) + Fat (%) + Ash (%) + Protein (%) = 100%. Calculate protein MEAT QUALITY CONTROL METHODS … 3. Chemical methods … Moisture/fat/protein determination … This method is not precise, but it is fast and provides useful results about composition of meat Some other chemical tests use indicator papers 58 MEAT QUALITY CONTROL METHODS … 4. Microbiological examination The purpose is to determine the degree of bacterial contamination in meat and meat products Microbiological examination methods require laboratory facilities Unclean conditions will always indicate high microbiological contamination 59 MEAT MEATQUALITY QUALITYCONTROL CONTROLMETHODS METHODS… … 4. Microbiological examination … Microbiological testing can be done: – Qualitatively as microbiological screening, for example by contact (trigger) such as using an impression plate – Quantitatively by determining the exact number of microorganism per sample unit (in cm2 or grams) by using the swab or destructive method Quantitative testing can be either determination of – The entire contaminating flora, also called “total plate count” – A specific group of microorganisms out of the entire flora, also called “selective plate count”. 60 MEAT QUALITY CONTROL METHODS … 4. Microbiological examination … Sampling methods Contact (Trigger) method Microbiological culture media in special moulds are lightly pressed against surface of meat to be tested The microbes adherent to the surface of these meat are absorbed by the surface of the culture media The contaminated media are incubated for 1-2 days at 30-35oC Microbial colonies can be identified and counted 61 MEAT QUALITY CONTROL METHODS … 4. Microbiological examination … Sampling methods … Contact (Trigger) method The media to be used is determined by the type of microorganism targeted Plate before impression (left) Impression on test surface and after impression and62 (purple colour) incubation (right) MEAT QUALITY CONTROL METHODS … 4. Microbiological examination … Sampling methods … Agar sausages (etc) can be used instead of Petri-dish agar media 63 MEAT QUALITY CONTROL METHODS … 4. Microbiological examination … Sampling methods … Swab method Surface contamination related to a certain area can be sampled using a sterile swab Microorganisms collected by the swab technique are rinsed off with sterile water and the microbial content of the liquid is tested Sampling with swab Rinse off bacteria in sterile water + 64 transfer to culture media MEAT QUALITY CONTROL METHODS … 4. Microbiological examination … Sampling methods … Swab method … One disadvantage of the swab method is that some microbes may remain in the swab, and hence, underestimate microbial load in the food product 65 MEAT QUALITY CONTROL METHODS … 4. Microbiological examination … Sampling methods … Destructive method 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 The sample received, which has a defined surface area, is further standardized by removing tissue from the bottom layer until a standardized weight (e.g. 10g) is achieved The trimmed sample is homogenised and analysed for microbial contamination 66 MEAT QUALITY CONTROL METHODS … 4. Microbiological examination … Microbial analysis methods Total plate count Selective plate count READ ABOUT THEIR PROCEDURES 67