2/25/14 Fennema's Food Science Technology Food Chemistry Fourth Edition ·Food preservation: food safety food quality
2/25/14 1 Food Science & Technology • Food preservation: food safety food quality
2/25/14 2 Water and lce Purt III Food Systems. 多 Davd s Reid and Owen R.Fennema Less important CONTENTS r'5a 12 r加c作okan ra6som0og 21 Mo 213.1 The lle 2
2/25/14 2 Less important
2/25/14 Food Safety Food Quality ·Chemical Nutrition ·Biochemical ·Sensory flavor ·Microbiological appearance texture Water Food Water is the principle component of foods Water functions as a medium for chemical reactions. Water functions as a medium for microbiological growth
2/25/14 3 Food Safety • Chemical • Biochemical • Microbiological Food Quality • Nutrition • Sensory flavor appearance texture Water & Food • Water is the principle component of foods. • Water functions as a medium for chemical reactions. • Water functions as a medium for microbiological growth
2/25/14 Phases or States of Water Phases or States of Water ·Solid(ice) State of water depends on temperature and pressure. ·Liquid At constant pressure it requires heat to change temperature and state. ·Gas or vapor At constant temperature,it requires changes in pressure to change state. Temperature change Phase change ercee2gacwaeraequeuoasee ·Ice to liquid water requires80 calg at0℃ ·10 g ice at0℃requires: Toraise the temperature of 100g water from 10to20c 10x100=1000 calories 10 x 80=800 calories One calorie is not the same as one food Calorie ·“Ice Diet" .1 Calorie(food calorie)=1000 calorie one meter. 800 Calories will melt 8,000g ice 4
2/25/14 4 Phases or States of Water • Solid (ice) • Liquid • Gas or vapor Phases or States of Water • State of water depends on temperature and pressure. • At constant pressure it requires heat to change temperature and state. • At constant temperature, it requires changes in pressure to change state. Temperature change • 1 calorie of heat per gram of water is required to raise the temperature of water one ºC. • To raise the temperature of 100 g water from 10 to 20 ºC requires 10 x 100 = 1000 calories • One calorie is not the same as one food Calorie • One Joule is 0.2390 cal (1 J = 1N . M) 1 J is the energy required to lift a small apple one meter straight up. Phase change • Ice to liquid water requires 80 cal/g at 0 ºC • 10 g ice at 0 ºC requires: 10 x 80 = 800 calories • Ice Diet • 1 Calorie (food calorie) = 1000 calorie • 800 Calories will melt 8,000g ice
2/25/14 Phase diagram of Water Temperature control Liquid Ice and liquid water mixture I atm Temperature =0C Solid Vapor Temperature Liquid Pressure cooke 121 Liquid or 1 atm 0℃ 100C Retort 1 atm 0℃ 100rC Solid Solid Vapor Vapor or freeze dricd Temperature Temperature 5
2/25/14 5 Temperature control • Ice and liquid water mixture Temperature = 0 ºC • Liquid water and steam Temperature = 100 ºC • At normal pressure (one atm) the temperature cannot go above 100 ºC with liquid water present. Temperature Pressure 1 atm 0ºC 100ºC Phase diagram of Water Temperature Pressure 1 atm 0ºC 100ºC 121 ºC Temperature Pressure 1 atm 0ºC 100ºC Sublimination or freeze dried