FSC 325 EXAM 3 Continuous Heat Sterilization and Pasteurization Questions and Answers , 100% Pass

FSC 325 EXAM 3 Continuous Heat Sterilization and Pasteurization Questions and Answers , 100% Pass pasteurization - ANSWER -heat treatment below 100C main function inactive enzymes kill non-spore forming bacteria kill yeasts and molds The severity of the heat treatment depends on pH of food - ANSWER -Low acid foods (pH 4.5) Destruction of pathogenic bacteria High acid food (pH 4.5) Destruction of spoilage MO Inactivation of enzymes Extent of heat required determined by - ANSWER -The D value of the most heat resistant enzyme or MO which may be present in food May be batch or continuous examples: Milk - 12D63 in C. burnettii (D63 = 2.5 min.) Z = 4.1C 63°C for 30 min. or 71.5°C for 15 sec. 2 | P a g e Created by Grace Amelia © 2025, All Rights Reserved. Liquid whole eggs - 9D in S. seftenburg 60°C for 3 min. or 64.4°C for 2.5 min. Processes and equipment pasteurization - ANSWER -LTLT Low temperature, long time Equipment specifications. Thermometers (3; liquid juice, airspace and controller) Agitators/headspace heater Vat Advantages good for low volume Easy to operate, control, clean and relatively inexpensive. Disadvantages Efficiency is very low, since heat recovery is ZERO. High Temperature, Short Time - ANSWER -High Temperature, Short Time Milk - 71.5C for 15 sec Higher Heat, Short time (HHST) Better retention of nutrients Also called flash pasteurization Example: Milk 88 degree C for 1 sec 3 | P a g e Created by Grace Amelia © 2025, All Rights Reserved. 94oC for 0.1 sec 100oC for 0.01 sec HTST for milk - ANSWER -Alkaline phosphatase (ALP) Naturally occurring enzyme in milk Has similar heat resistance to heat resistant pathogens If ALP is destroyed then milk is adequately pasteurized Pasteurization - a very good idea - ANSWER -a very good idea, since many of the pathogens found in milk/ contaminated juice cause communicable diseases in man. Pasteurization of packaged foods - ANSWER -Some liquid foods are pasteurized after packaging Usually done with hot water if packaged in glass Steam/Air mixtures or hot water used for metal or plastic containers batch or continuous Pasteurization of unpackaged liquids - ANSWER -Low viscosity foods (milk, milk products, fruit juices and liquid eggs) Usually done as a continuous operation Plate heat exchangers - ANSWER -most widely used Consist of a series of thin vertical stainless steel plates 4 | P a g e Created by Grace Amelia © 2025, All Rights Reserved. Plates form parallel channels Liquid food and heating medium are pumped in alternate channels Usually set up in counter current patterns Components of HTST - ANSWER -Balance tank Plate heat exchanger Holding tube Flow diversion valve Positive displacement pump Or centrifugal pump with meter-based control Heat Recovery (Regeneration) - ANSWER -Using the hot pasteurized product to pre-heat the cold product Reduces the amount of cold water needed to cool the product up to 95% of heat is recovered Types of Heat Exchangers - ANSWER -Tubular plate Scraped surface Direct steam 5 | P a g e Created by Grace Amelia © 2025, All Rights Reserved. Nearly every system employs an indirect preheating system, typically a plate based HTST system, to heat the product to about 170˚F. This reduces the work done by the UHT equipment without any deleterious effect on the product flavor. After preheating: - ANSWER -The product is pumped into the high temperature/pressure chamber (next slide) where the steam and product are mixed. The chamber temperature is approximately 285˚F - 295˚F