FDST4l10lectures19-28

FDST4l10lectures19-28 - Spring 2010 FOOD SCIENCE...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Spring 2010 FOOD SCIENCE 4010--Lecture 19 Dielectric, ohmic and infrared heating PRINCIPLES: Microwaves heat foods by oscillating water molecules which induce friction. Radio frequency heating can be more focused on a specific location with more precise control than other types of heating. Ohmic heating is particularly effective in preserving foods with particulates. -Cold spots always changing with particulates. Ohmic heating like electrocution, on-off heating. You know precisely how much heat, and even heating patterns. Infrared radiation affects eating quality through surface characteristics and color of the food. -Omitted by hot objects. 3 main things, surface temps of heated and heating objects, surface properties of each, shapes of each. Color typical of baking. Seals in aroma and flavor. Dries food. Thermal conductivity is the limiting factor in infrared radiation but not in dielectric or ohmic heating. -Thermal conductivity depends of the properties of the food. Dielectric and ohmic heating pass through food, with no additional heat after stopped. Food Processing Technology Chapter 18
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
DISCUSSION QUESTIONS: 1. How are the two types of dielectric heating similar? How do they differ? 2. How are microwaves used to temper foods? What are some of the products that are tempered by microwaves? 3. What are the four requirements needed for ohmic heaters to be commercially successful? 4. List and describe four types of pretreatments of solid foods before ohmic heating? 5. What are the approximate emissivities of four materials in food processing? What is the significance of these differences?
Background image of page 2
Spring 2010 FOOD SCIENCE 4010--Lecture 20 Chilling and controlled- or modified-atmosphere storage and packaging PRINCIPLES: Food deteriorates biologically, chemically and physically. -Food processing/preservation is designed to prevent or slow deterioration. Longer from time of harvest to time of consumption the more important it is. Biological deterioration – microbial decay, senescence… preprogrammed death. Chemical – oxidation, browning. Easier to control enzymatic browning. Physical – loss of moisture (transpiration, evaporation), breakdown of texture (wilting, shriveling). Microbial growth in foods can preserve them, spoil them or make them unsafe. -Fermentation – bread, kimchi, sauerkraut, soy sauce. Spoilage not an indicator of safety. Controlled-atmosphere storage involves the monitoring of gas composition and maintaining composition within given tolerances. -Slow down respiration, slow down senescence. Respiration, transpiration, senescence, death. Lowering level of oxygen, required for respiration and increase CO2. Lower oxygen too much, fermentation. Exact concentration of gases known and controlled. Modified-atmosphere storage and packaging involves setting of the initial
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 19

FDST4l10lectures19-28 - Spring 2010 FOOD SCIENCE...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online