1 / 22

Engineering and thermal processing

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.

tamaraj
Download Presentation

Engineering and thermal processing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Engineering and thermal processing

  2. Engineers are different from scientists • What do scientists do? • What do engineers do? • The importance of simplifying assumptions • examples

  3. 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

  4. 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

  5. Most food processing involves the addition or removal of energy.Most types of food spoilage have engineering solutions.

  6. Thermal Processing and Refrigeration

  7. Heating and Cooling: • Heat transfer (heating or cooling) is driven by ΔT(the temperature difference) Assume a Room Temperature of 60°F.

  8. Pasteurization: • 7 log kill for Salmonella in Milk = 99.99999% • Pasteurization of eggs: 3 log reduction = 99.9% 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 0.01sec 6 sec

  9. Log Numbers

  10. Log vs linear

  11. Pasteurizers (Ohio State University) 80 C for thirty seconds 60 C for thirty minutes

  12. Canning: • Invented by Appert in 1790s. • Commercial sterility. • Destroys pathogens and spoilage organisms that can grow. • Requirements for high acid foods (pH < 4.6) are not very stringent. Why? • Can be done in a boiling water bath. Home canned tomatoes, OK Home canned beans, No

  13. Requirements for low acid (pH >4.6) foods are very strict • Low acid foods pH > 4.6 • Target is C. botulinum 12 log reduction = 99.9999999999% • 2 to 4 min @ 250°F • Requires certified retort operators, approved process

  14. Flow Chart: Canning of Corn (FAO) Blanching!

  15. Flow Chart: Canning of Peas (FAO) Flow Chart for the pea canning process Blanching!

  16. Mild vs. Severe Heat Treatment: • Mild Heat Treatment): • Aims: • Kill pathogens • Reduces bacterial load (Food is not sterile) • Inactivate enzymes • Advantages: • Minimal damage to flavor, texture, and nutritional quality. • Disadvantages: • Short shelf life • Another preservation method must be used, such as refrigeration or freezing • Examples: • Pasteurization • Blanching • Severe Heat Treatment: • Aims: • Kills all bacteria • Food will be commercially sterile • Advantages: • Long shelf life • No other preservation method is necessary • Disadvantages: • Food is over-cooked • Major changes in texture, flavor, and quality • Examples: • Canning

  17. Refrigeration and Freezing:(85 % of food is frozen at some point) Freezing: • Slowly: • Water migrates • Freeze “pure” • Solutes concentrate • Large crystals • Rapidly: • Freezes in place • No solute concentrate • Small crystals • Better structures

  18. How refrigeration works Simplified Energy Input Condense Expand

  19. Freezing: • 3 Types: • Plate Freeze • Contact with very cold surface • Blast Freeze • Very cold air • Very high velocity • Immersion • N2 • Flash Frozen = “IQF”

  20. Processing can create multiple products– Apple Juice Bottle – “hot pack” Clear glass Brown plastic Concentrate Liquid Frozen Metal can Aseptic – Brix pack (“Sipps”)

  21. “Nonthermal” processingnext lecture… • High pressure • Irradiation • UV light • Pulse light • High intensity light • Pulsed electric field

  22. How pumpkin pies are made… Happy Thanksgiving!

More Related