Editing Pasteurization (section)

===Equipment===

Food can be pasteurized either before or after being packaged into containers. Pasteurization of food in containers generally uses either steam or hot water. When food is packaged in glass, hot water is used to avoid cracking the glass from [[thermal shock]]. When plastic or metal packaging is used, the risk of thermal shock is low, so steam or hot water is used.<ref name="Fellows-2017"/>

Most liquid foods are pasteurized by using a continuous process that passes the food through a heating zone, a hold tube to keep it at the pasteurization temperature for the desired time, and a cooling zone, after which the product is filled into the package. [[Plate heat exchanger]]s are often used for low-[[viscosity]] products such as animal milk, nut milk, and juices. A plate heat exchanger is composed of many thin vertical stainless steel plates that separate the liquid from the heating or cooling medium. 

[[Shell and tube heat exchanger|Shell and tube heat exchangers]] are often used for the pasteurization of foods that are [[non-Newtonian fluid]]s, such as dairy products, tomato [[ketchup]], and baby foods. A tube heat exchanger is made up of concentric stainless steel tubes. Food passes through the inner tube or tubes, while the heating/cooling medium is circulated through the outer tube.

Scraped-surface heat exchangers are a type of shell and tube that contain an inner rotating shaft having spring-loaded blades that serve to scrape away any highly viscous material that accumulates on the wall of the tube.<ref>{{Cite book|title=Introduction to Food Process Engineering|last=Smith|first=P. G|publisher=Food Science Text Series|year=2003|pages=152–54, 259–50}}</ref>

The benefits of using a [[heat exchanger]] to pasteurize foods before packaging, versus pasteurizing foods in containers are:
* Higher uniformity of treatment
* Greater flexibility with regard to the products that can be pasteurized
* Higher heat transfer-efficiency<ref name="Fellows-2017"/>
* Greater throughput with many other processes of using the milk 


After being heated in a heat exchanger, the product flows through a hold tube for a set period to achieve the required treatment. If pasteurization temperature or time is not achieved, a flow diversion valve is used to divert the under-processed product back to the raw product tank.<ref>{{Cite journal|date=2005-06-01|title=HACCP with multivariate process monitoring and fault diagnosis techniques: application to a food pasteurization process|journal=Food Control|language=en|volume=16|issue=5|pages=411–422|doi=10.1016/j.foodcont.2004.04.008|issn=0956-7135|last1=(Kosebalaban) Tokatli|first1=Figen|last2=Cinar|first2=Ali|last3=Schlesser|first3=Joseph E.|hdl=11147/1960|hdl-access=free}}</ref> If the product is adequately processed, it is cooled in a heat exchanger, then filled.