Engineering and thermal processing Engineers are different from scientists What do scientists do? What do engineers do? The importance of simplifying assumptions examples Engineers deal with Heat transfer, always runs from hot to cold so refrigerators or freezers need pumps (energy input) Mass transfer Mass balance Consider a simple drier The 2nd Law of Thermodynamics:everything goes to maximumrandomness (entropy) Unless you put in energy Electric, microwave, pressure, thermal, ionizing Types of Heat Transfer (demo) Conduction Convection Radiation Most food processing involves the addition or removal of energy.Most types of food spoilage have engineering solutions. Thermal Processing and Refrigeration Heating and Cooling: Heat transfer (heating or cooling) is driven by ΔT (the temperature difference) ΔT (°F) Boiling H2O 152 Oven 350°F 292 Broiler @ 2000°F 1940 Refrigerator 40°F 20 Household Freezer 10°F 50 Commercial Freezer -40°F 100 Liquid Nitrogen -380°F 440 Assume a Room Temperature of 60°F. Pasteurization: 7 log kill for Salmonella in Milk = % Pasteurization of eggs: 3 log reduction = % 145°F for 3 to 4 mins. Fruit juices are pasteurized to reduce microbial count and inactivate enzymes; they were thought not to carry pathogens. Temperature: 145°F (63C) 161°F (72C) 212°F (100C) 280°F (131C) Time: 30 min 15 sec