Food Size Reduction Reviewer

SIZE REDUCTION REVIEWER TYPES OF FORCES USED IN SIZE REDUCTION SIZE REDUCTION COMPRESSION FORCES - Applied to brittle foods like crystalline...

SIZE REDUCTION REVIEWER TYPES OF FORCES USED IN SIZE REDUCTION SIZE REDUCTION COMPRESSION FORCES - Applied to brittle foods like crystalline Also called comminution. solids to fracture them. Process of reducing the average size of solid IMPACT FORCES food. - Important in reducing hard materials, Includes: grinding, compression, or impact where collisions cause food to break forces. apart along lines of weakness. Related processes for liquids include: SHEARING (ATTRITION) FORCES homogenisation, emulsification, and - Used for fibrous or softer foods, atomisation. tearing them apart. BENEFITS OF SIZE REDUCTION KEY THEORY INCREASED SURFACE AREA. - Size reduction operations involve - Enhances drying, heating, cooling rates. compression, impact, and shearing - Improves extraction efficiency (e.g., fruit forces, with one force typically juice, cooking oil). dominating. CONTROLLED PARTICLE SIZE - Elastic stress limit (E): The point where - Essential for functional or processing the material returns to its original properties (e.g., icing sugar, spices). shape after stress is removed. - Allows for more complete ingredient - Exceeding the elastic limit causes mixing (e.g., dried soup, cake mixes). permanent deformation, reaching the IMPACT ON FOOD QUALITY yield point (Y) and eventually the breaking point (B). QUALITY IMPROVEMENTS - Enhances eating quality and suitability for further processing. - Expands the range of available products. POTENTIAL DEGREDATION - May promote enzymatic or microbial degradation. - Requires additional preservative treatments. METHODS OF SIZE REDUCTION CHOPPING: Completely random; general term. STRESS-STRAIN BEHAVIOR IN FOODS CUTTING: Diving food with a knife. SLICING: Thin, uniform cuts usually lengthwise. DICING: Small, uniform cubes METHODS OF SIZE REDUCTION MILLING - Produces powders or pastes of increasing fineness (e.g., spices, flours, powdered sugar). EMULSIFICATION AND HOMOGENISATION - Creates products like mayonnaise, milk, butter. Elastic Limit (O–E): Up to this point, the material LAWS GOVERNING ENERGY IN SIZE REDUCTION behaves elastically, returning to its original pe after KICKS LAW stress is removed. States tat the energy required to reduce Yield Point (Y): Beyond this point, food materials begin particle size is proportional to the ratio of the to flow or deform plastically. initial size to the final size of the material. Breaking Point (B): At this point, the material fractures Works well or coarse grinding, where the and cannot return to its original shape. change in surface area is small, such as when reducing large chunks of material. MATERIAL TYPES COARSE GRINDING: RR = Below 8:1 - Hard, Brittle Foods (1): Foods like nuts FINE GRING GRINDING: RR = Can exceed 100:1 and hard candies that fracture without significant deformation. - Hard, Ductile Foods (2): Materials that can deform before fracturing (e.g., firm cheeses). E: Energy required per mass of feed (J) - Soft, Ductile Foods (3): Softer foods Kk: Kick’s constant like dough that deform extensively d1: average initial size of the pieces (m) before breaking. d2: average size of the ground particles (m) - Soft, Brittle Foods (4): Foods that d1/ d2: Size reduction ratio (RR) break easily, like crackers or chips, but without much deformation. RITTINGER’S LAW ENERGY REQUIRED FOR SIZE REDUCTION Proposes that the energy is proportional to the increase in surface due to the size BREAKING STRESS IN SIZE REDUCTION reduction. - When strain exceeds the elastic stress Best for fine grinding where increase in limit, the food permanently deforms. If surface are is significant. (Flour and spices) stress continues, the yield point (Y) is reached, and beyond that, the food fractures at the breaking point (B). KR: Rittinger’s Constant - As the food breaks, stored energy is released as heat. Additional fissures BOND’S LAW must be created to reduce the particle A combination of the previous laws. size further, requiring more energy. Used for hard foods like grains or sugars. FACTORS AFFECTING ENERGY INPUT - Friability of the Food: Determines how Less precise easily a food breaks along lines of weakness. Foods with fewer lines of weakness require more energy to reduce in size. W: Bond work index (J/kg) (40 000–80 000 - Moisture Content: Moisture influences J/kg for hard foods the ease of size reduction. Dry foods d1: diameter of the sieve aperture that may lead to dust creation and allows 80% of the mass of the feed to pass. excessive energy consumption, (m) whereas moist foods may require less d2: diameter of sieve aperture that allows energy. 80% of the mass of the ground material to pass. FOOD EXAMPLES (m) - Foods with low moisture (e.g., pasta or flour) need more energy to grind than foods with higher moisture content. - EQUIPMENT FOR SIZE REDUCTION OF SOLID FOODS COST-EFFECTIVE - Low operating costs and less frequent CATEGORIES OF FOOD MATERIALS blade sharpening. FIBROUS FOODS LONGER BLADE LIFE - Ultrasonic blades stay sharp longer Meats, fruits, and vegetables. compared to conventional blades. Firm texture, requiring specific cutting conditions APPLICATION OF SIZE REDUCTION EQUIPMENT DRY PARTICULATE FOODS Examples: Grains and dry powders. Reduced to fine powders for processing. CUTTING METHODS FOR FIBROUS FOODS MEATS: Tempering (Freezing Just Below Freezing Point); Enhances cutting efficiency by softening meat fibers FRUITS AND VEGETABLES: Cut at ambient or chill temperatures due to their firm texture. IMPORTANCE OF KNIFE BLADE SHARPNESS PROPERTIES AND APPLICAION OF SELECTED SIZE REDUCTION EQUIPMENT SHARP BLADES - Minimize cutting force. - Prevent cell rupture, which leads to product damage and reduced yield. LUBRICANT IN CUTTING - Water as a lubricant in moist foods. - Sticky foods like dates or candied fruits require food-grade lubricants. ULTRASONIC CUTTING TECHNOLOGY Introduced in 1990s Blades or “horns” (probes) vibrate at 20kHz Cutting stroke of 50–100 µm. BENEFITS OF ULTRASONIC CUTTING FOUR MAIN TYPES OF SIZE REDUCTION EQUIPMENT FOR FIBROUS FOODS. SUPERIOR CUT QUALITY - Cleaner, more precise cuts with 1. SLICING AND FLAKING EQUIPMENT minimal disturbance to the food 2. DICING EQUIPMENT structure. 3. SHREDDING EQUIPMENT 4. PULPING EQUIPMENT LOWER CUTTING FORCE - Reduced energy consumption and ADVANCED SLICING EQUIPMENT blade wear. CONTROLLED PARTICLE SIZE COMPUTER-CONTROLLED DESIGNS - Can cut multi-layered products or hard - SLICING AND FLAKING EQUIPMENT particles in soft matrices. - DICING EQUIPMENT SELF-CLEANING BLADES - SHREDDING EQUIPMENT - Significantly fewer crumbs and debris - PULPING EQUIPMENT during the cutting process. DICING EQUIPMENT DISC MILLS - First, food is sliced. Single-Disc Mills: Food passes through a gap - Then, rotating blades cut the slices into between a stationary casing and a rotating strips. grooved disc. - Another set of rotating blades cuts the Double-Disc Mills: Two discs rotate in opposite strips into cubes. directions for greater shearing. - Used for vegetables, fruits, and meats. Pin-and-Disc Mills: Intermeshing pins provide additional shearing and impact forces for SHREDDING EQUIPMENT enhanced grinding. HAMMER MILL HAMMER MILLS - Modified with knives instead of hammers for a cutting action. Comprises a high-speed rotor fitted with swinging hammers inside a cylindrical PULPING EQUIPMENT chamber. COMBINATIN OF COMPRESSION AND Disintegrates food mainly through impact SHEARING forces. - Used for juice extraction, oil Widely used for crystalline and fibrous production, and pulping meats. materials like sugar and spices. ROTARY FRUIT CRUSHER ROLLER MILLS - Cylindrical screen with high-speed brushes/paddles forces pulp through Widely used for wheat milling. perforations. Involves two or more steel rollers pulling food - Example: Grapes, tomatoes, or soft through the nip (space between rollers). fruits. Main Force: Compression. - Perforation size controls pulp fineness. Additional Forces: Shearing if rollers rotate at OTHER PULPING TECHNIQUES different speeds or are fluted. Adjustable nip size for various foods, with BOWL CHOPPER overload springs protecting against damage. - Used to chop meat and harder fruits/vegetables into a pulp. MODES OF OPERATION IN MILLS - Common in making sausagemeat, Free Flow: Food passes through in a single mincemeat preserves. pass. - Slowly rotating bowl moves Choke Conditions: Food stays in the mill until ingredients beneath high-speed it's small enough to pass through the screen. rotating blades. Recirculation: Larger particles are recirculated SIZE REDUCTION OF DRY FOODS until desired size is reached. Dry foods require specialized equipment for EFFECT ON FOODS size reduction. Purpose of Size Reduction:Controls textural Selection of equipment depends on food type. and rheological properties. BALL MILLS Impact on Texture: Textural changes in foods like bread, hamburgers, and juices depend on Cylindrical steel containers filled with steel size reduction conditions. balls. Oxidative Deterioration: Shearing forces dominate at low speeds, while - Cell disruption increases surface area, impact forces are stronger at high speeds. promoting oxidation and higher Used to produce fine powders, such as food microbial and enzymatic activity. colorants. - Moist foods require preservative Rod mills, a variation, use rods instead of balls measures like chilling or freezing post- for handling sticky or adhesive foods. size reduction to avoid rapid deterioration. SENSORY CHARACTERISTICS FACTORS AFFECTING STABILITY - Type and amount of emulsifier. CHANGES DURING SIZE REDUCTION - Size of globules in the dispersed phase. - Small, often unreported, changes in - Interfacial forces, viscosity of the color, flavor, and aroma of dry foods. continuous phase, and density - Oxidation of carotenes leads to differences. bleaching and nutritional loss. ROLE OF EMULSIFYING AGENTS - Volatile compounds in spices and nuts - Reduces interfacial tension between are lost during size reduction. phases, preventing droplet - In moist foods, cell disruption coalescence. accelerates enzymatic reactions, - Emulsifiers lower the energy required causing quicker flavor, aroma, and to form emulsions. color deterioration. - Synthetic emulsifiers (glycerol esters, NUTRITIONAL VALUE sorbitan esters of fatty acids) are commonly used for food processing. LOSSES DUE TO SIZE REDUCTION - Emulsifiers are classified as polar and - Increased surface area accelerates t he non-polar. oxidation of fatty acids and carotenes. SLECTED EMULSIFYING AGENTS - Vitamin C and thiamin losses during - Agents with low HLB values (below 9) size reduction are significant (e.g., 78% are lipophilic and used for w/o reduction in Vitamin C during slicing of emulsions; those with HLB values cucumber). between 8 and 11 are intermediate - Nutritional losses during storage and used as wetting agents; and those depend on temperature, moisture with high values (11 to 20) are content, and oxygen concentration. hydrophilic and are used for o/w emulsions, detergents and solubilizers. STABILIZER - POLYSACCHARIDE HYDROCOLLOIDS: Stabilizers are polysaccharides that dissolve in water to form viscous solutions or gels. In O/W emulsions, stabilizers increase viscosity and prevent coalescence FIVE MAIN TYPES OF HOMOGENISERS SIZE REDUCTION OF LIQUID FOODS 1. High-speed mixers EMULSIFICATION & HOMOGENIZATION 2. Pressure Homogenisers - Emulsification creates stable emulsion 3. Colloid mills by mixing immiscible liquids. 4. Ultrasonic homogenisers - Homogenization is more intense, 5. Hydroshear homogenisers and microfuidisers reducing droplet size and increasing HIGH SPEED MIXERS particle number in the dispersed phase. High-speed mixers use turbines or propellers - Both processes affect food to pre-mix emulsions of low-viscosity liquids. functionality and texture but not They operate by shearing the food at the edges nutritional value or shelf life. and tips of the blades. Commonly used for emulsification in food THEORY OF EMULSIONS processing. TYPES OF EMULSIONS - Oil in Water (O/W): e.g., milk. - Water in Oil (W/O): e.g., margarine. PRESSURE HOMOGENISERS Ice Cream and Cake Batters Consists of a high-pressure pump operating at ICE CREAM: An oil-in-water (o/w) emulsion 10,000–70,000 × 10³ Pa. incorporating air for softness and scoopability. Liquid is forced through a small gap at high Freezing stabilises the emulsion, and velocity, creating turbulence and shear forces. commercial ice cream has higher overruns. Used widely in milk pasteurisation, ice cream, CAKE BATTERS: o/w emulsions where the and soup production. continuous phase is starch, sugar, and flavours. COLLOID MILLS Color, Aroma, and Nutritional Value Disc mills with a small clearance (0.05–1.3 mm) Colour: Increased reflectance from between rotating and stationary discs. homogenised fat globules enhances food Used to create high shearing forces, suitable whiteness (e.g., milk). for high-viscosity liquids. Aroma: Volatile components are dispersed, Effective for peanut butter, meat, or fish improving flavour. pastes. Nutritional Value: Improved digestibility of fats and proteins; chilling or freezing can lead ULTRASONIC HOMOGENISERS to minor losses. Uses high-frequency sound waves (18–30 kHz) to cause compression and cavitation of air bubbles. Produces emulsions with droplet sizes of 1–2 μm. Commonly used for salad creams, baby foods, and essential oil emulsions. HYDROSHEAR HOMOGENISERS AND MICROFLUIDISERS Hydroshear homogenisers create shear by spinning liquid in increasingly smaller circles. Microfluidisers pump fluids into chambers, creating shear and turbulence. Droplets smaller than 1 μm are produced. EFFECT ON FOODS Viscosity or Texture Homogenisation affects the mouthfeel and texture of liquid and semi-liquid foods. Example: Reduces fat globules in milk, giving a creamier texture. Dairy Products and Margarine BUTTER: Created by churning cream, forming butter grains. MARGARINE: A water-in-oil (w/o) emulsion, produced from oils and skim milk emulsified together. Texture achieved through crystallization of fats during chilling.