Meat Preservation-1.pdf

Meat Preservation  Meat preservation controls spoilage.  It inhibits microorganism growth, slows enzymatic activity, and prevents fatty acid oxidation.  Extends meat's freshness and safety.  Ensures meat is healthy and bacteria-free....

Meat Preservation  Meat preservation controls spoilage.  It inhibits microorganism growth, slows enzymatic activity, and prevents fatty acid oxidation.  Extends meat's freshness and safety.  Ensures meat is healthy and bacteria-free.  Various preservation methods are used.  Method depends on the meat's intended use. Why Preserve Meat? 1. Delays products spoilage 2. Extends life of the products 3. Improves product quality Meat preservation – How? All preservative methods manipulate environmental conditions to discourage microbial growth, grouped into three categories:  Control by temperature  Control by moisture  Control by lethal agents Here are a few common methods: 1. Chilling/Rrefrigeration  Meat preservation by refrigeration involves keeping meat at cold temperatures.  Chilling slow down the growth of bacteria and other microorganisms.  It is necessary to reduce the temperature of carcass immediately after evisceration to 4ºC within 4 hours of slaughtering 1 Types of Chilling Methods a. Immersion chilling  The product is immersed in chilled (0 - 4ºC) water. b. Air chilling:  Carcasses are misted with water in a room with chilled air.  Air chilling procedure is safer than the water chilling procedure with respect to microbiological count.  It helps to prevent denaturing of proteins Chilling process  Choose fresh, high-quality meat.  Handle meat with clean hands and tools to prevent contamination.  Wrap meat in airtight packaging to prevent exposure to air, which can cause spoilage.  Use materials like vacuum-sealed bags, plastic wrap, or aluminum foil.  Refrigerate meat at temperatures between 0°C to 4°C.  Cooling must be rapid with the aim to lower the temperature of deepest portion.  Ensure a consistent temperature by avoiding frequent opening of the refrigerator.  Label packages with the date of refrigeration to track freshness.  Rotate meat, placing older packages at the front for first use.  Proper air circulation in the storage area helps in even cooling.  Fans and ventilation systems are often used.  The humidity level is controlled to prevent meat from drying out.  Ideal humidity is around 85-90%.  Meat is usually vacuum-packed or wrapped in plastic to protect from contamination and dehydration.  Packaging helps in maintaining quality during storage. 2   Chilled meat should be used within a certain period, typically a few days to a week, depending on the type of meat.  Labels often indicate the best-before date. Types of Meat and Storage Duration  Poultry: 1-2 days  Ground Meat: 1-2 days  Fish and Shellfish: 1-2 days  Beef, Pork, Lamb (Steaks, Chops, Roasts): 3-5 days  Cured Meats (Bacon, Ham): 7 days Rate of chilling and its effects  Air speed and Relative Humidity must be controlled to minimize surface desiccation.  Airspeed should be monitored and reduced as soon as temperature difference between meat surfaces and surrounding drops.  Greater the bulk of carcasses and their fat cover longer the cooling time.  Over-effective chilling of pre-rigor beef and lamb may lead to cold shortening.  Reduce temperature to 15°C and maintain until onset of rigor and completion of rigor.  Fresh chilled meat will still deteriorate with time due to surface changes during cooling. - Consistency of surface connective tissue changes will restrict further evaporation so encourage mould and bacterial growth  Surface desiccation/drying, increased salt concentration will promote oxidation of Myoglobin to Metmyoglobin resulting in dark colours. Advantages  Low temperatures inhibit the growth of most bacteria, extending the meat's shelf life.  Keeps the meat’s nutrients intact for longer periods compared to other preservation methods. 3   Retains the meat's natural taste and texture, making it more appealing when cooked.  Allows for longer storage, so you don’t have to cook or consume the meat immediately.  Reduces the risk of spoilage and foodborne illnesses. Disadvantages  Only extends the shelf life by a few days to weeks; not suitable for long-term storage.  If not kept at the correct temperatures, bacteria can still grow, leading to spoilage and health risks.  Other foods stored in the refrigerator can contaminate the meat.  Over time, even refrigerated meat can lose moisture and deteriorate in quality. 2. Freezing  Freezing is highly effective for preserving meat.  It lowers meat temperature.  Slows or stops microbial activity, enzyme action, and oxidation. Principles of Freezing  Rapid Freezing: - Quick freezing helps form small ice crystals, which minimize cell damage.  Slow Freezing: - Forms large ice crystals that can rupture cell walls, leading to texture and quality loss.  Fast freezing produce better quality than low freezing Preparation for Freezing  Choose fresh, high-quality meat to freeze.  Cut meat into portions suitable for future use.  Use moisture-vapor-proof materials for packaging like heavy-duty aluminum foil, freezer paper, or vacuum-sealed bags.  Date and label packages for easy identification. 4 Freezing Process Pre-freezing: Cool meat in the refrigerator before placing it in the freezer. Freezer Temperature:  Maintain at or below -18°C (0°F).  Ideal temperature -55ºC  Commercially temperature -29ºC  Domestically temperature -185ºC  Almost 98% of water freezes at -20ºC  Complete crystal formation occurs at -65ºC  Microbial growth stops at -12ºC  Works by stopping enzyme activity& microbial growth of bacteria ,yeast & moulds. Placement: Place meat packages in a single layer in the coldest part of the freezer for fast freezing. Storage Duration  Beef (Red Meat): Can be stored for up to 12 months.  Lamb: Can be stored for 6 - 9 months.  Pork: Can be stored for up to 6 months.  Ground Meat: Can be stored for 3 to 4 months.  Processed Meats: Can be stored for up to 2 months. Quality Maintenance  Ensure airtight packaging and remove as much air as possible from packages before sealing.  Frequent opening of the freezer can lead to temperature changes that affect meat quality.  Meat can be refrozen if it has been thawed in the refrigerator and remains at a safe temperature (≤ 4°C).  Refreezing can lead to moisture loss and quality degradation. 5   Handle raw meat with care to prevent contamination of other foods.  Use a freezer thermometer to ensure proper temperature.  Prevent spoilage and maintain quality by adhering to recommended storage times. Rate of freezing and its effects  Rapid freezing creates small ice crystals, causing minimal damage and distortion to muscle fibers and reducing water loss.  Slow freezing leads to large ice crystals, resulting in significant damage and distortion to muscle fibers and increased water loss as drip.  Additional water loss during slow freezing may occur due to surface protein denaturation from higher salt concentration.  Temperature range from -1.5°C to -5°C is crucial; most water in meat (about 75%) freezes here, where major tissue damage can happen.  Rapidly freezing meat to -5°C within 12 hours minimizes damage.  Glycoproteins (antifreeze proteins) help reduce cell damage during freezing by: - Lowering the freezing point of water. - Changing ice crystal morphology to needle-like structures via adsorption at the ice nuclei surface. - Preventing re-crystalization.  Meat can be treated with glycoproteins by soaking or injecting the animal 24 hours before slaughter. Effect of frozen storage  Dehydration (freezer burn) - Air pockets (whitish or amber patches) on frozen meat surface are caused by sublimation of ice crystals. - Larger ice crystals from re-crystallization result in more muscle fiber damage and increased drip loss. 6   Pre-rigor frozen meat may experience cold shortening upon thawing, causing more drip loss.  Drip loss is attributed to protein denaturation and breakdown.  Extended cold storage can lead to oxidative rancidity of exposed fats, especially in pork.  Adequate packaging and glazing minimize oxidative rancidity. Advantages  Extends the usability of meat for months.  Preserves nutritional value when done correctly.  Easy access to a variety of meats. Disadvantages  Possible when ice crystals form during slow freezing or repeated thawing.  Requires consistent energy input to maintain freezing temperatures. Frozen Meat 7 3. Canning  Canning is a method used to preserve meat by sealing it in airtight containers and then heating it to kill spoilage-causing microorganisms.  The process prevents bacteria, yeasts, molds, and enzymes from spoiling the meat. Selection and Preparation of Meat  Choose fresh, high-quality meat.  Trim off excess fat.  Pre-cook or prepare the meat as desired. Canning Process  Pack the meat into canning jars, leaving appropriate headspace (room at the top of the jar for expansion during heating).  For moist meats, add broth, water, or tomato juice.  Use a utensil to release trapped air bubbles.  Wipe jar rims clean.  Attach lids and screw-on bands finger-tight. Heat Processing  Place jars in a pressure canner (Typically, meats require high pressure).  Ensure temperatures reach at least 116-121°C to destroy Clostridium botulinum spores.  Mainly pork products such as ham are pasteurized and canned.  Involves mild heat treatment