Milling Journal - Q3 2008 - (Page 33)

and energy rises to hold more water, evaporation accelerates. During physical activity, people perspire as a mechanism to cool themselves through evaporative cooling. Just feel the trunk of your body after a session of tennis, golf, or mowing your yard. Your skin feels cool because heat energy in your body causes water evaporation to occur, and it takes a lot of energy for water to transition from a liquid to a gas. We know that when the humidity is high, the cooling effect is not as great as when the humidity or moisture in the air is low. Water vapor that loses energy and slows down allowing the molecules to become more heavily attracted to each other forms liquid or condensate. A cold beverage taken out of the cooler on a warm humid day provides a common example of condensation when the can “sweats.” The air around the can cools, causing the air to lose moisture-holding capacity. Water molecules slow down and attract each other, forming a film or droplets on the container’s surface Cold wheat transferred from the grain storage elevator to the mill for cleaning and processing often causes condensation to form on the transfer screw conveyor or drag conveyor as it passes into the mill. The condensation drips on the flour creating a slipping hazard, and the moisture remaining on the conveying equipment causes it to rust and fail early, requiring unscheduled replacement. Packaging of freshly baked bread at a temperatures greater than 10 degrees above ambient results in condensation in the package Equilibrium moisture content and relative humidity and water activity are critical values in the storage and maintenance of flour quality. The numbers related here are less important than product quality because customers don’t eat the numbers; they consume the flour. In Figure 1 (right), a general sorption isotherm showing how biological products equilibrate with their respective environment is presented. Unlike your car, where an incremental increase or decrease in gas flow results in the same equilibrium speed on a flat road, the equilibrium moisture content may be different depending if the relative humidity is increasing (adsorption) or decreasing (desorption). Sorption Isotherm and Flour Flour also equilibrates with its environment. For example, 14% moisture flour will dry out in areas of low relative humidity, and will increase in moisture content in areas of high humidity. The increase and Response No. 331 Response No. 332 MILLING JOURNAL Third Quarter 2008 33 http://www.bealldeg.com http://www.columbiaokura.com http://www.bealldeg.com http://www.columbiaokura.com

Table of Contents Feed for the Digital Edition of Milling Journal - Q3 2008

Milling Journal - Q3 2008 Contents Milling News Far West Rice Generates Own Power New IAOM-KSU Resident Courses Theodore "Ted" Korolchuk: Miller of the Year IAOM News New IGP Wheat/Flour Web Site Wheat Tempering and Surfactants New ADM Milling Center 2008-09 IAOM Officers Controlling Condensation International IAOM Meetings Pest Management/Subramanyam 2008 Wheat Crop Quality Report Product Quality/Gwirtz Buhler 2009 Resident Courses Northern U.S. Wheat/Backman Horizon Milling to Close ON Mill 2nd Quarter Milling Production Chilled Rolls Belting Product Reviews Milling News Enrichments Phil Weisenberger Obituary Material Handling Pneumatic Systems Mixers Roller Mills Roll Corrugation Product Reviews Storage Transportation Equipment Product/Service Directory Ad Index

Milling Journal - Q3 2008

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