Pasteurization is a mild heat treatment in which food and beverages are heated to <100°C. Pasteurization destroys enzymes and kills some, but not all, of the microorganisms present. On the other hand, food sterilization is a process that implies the application of heat above 100°C, usually ranging between 110°C and 121°C. The severe heat inactivates or kills the most heat-resistant microorganisms, Bacillus, and Clostridium spores (Clostridium botulinum).
The prevalence of unwanted microbes in the food makes it contaminated and unfit for consumption. The food is spoiled due to the metabolic activities of microorganisms as they continue to increase. The type of food spoilage varies depending on the microbial species; for instance, Pseudomonas are significant rancidity causes in butter. These gram-negative bacteria accelerate the digestion of fats in butter and produce glycerol and acids, which causes a foul smell and rancid taste.
Do you ever wonder why we need to cook meat at high temperatures for a long time? Meat has many bacteria as we obtain it from animal sources. Cooking meat at high temperatures kills these food-borne pathogens. Consumption of raw meat increases the chance of developing food-borne diseases. Moreover, canned food is sterilized to improve its shelf life. Damaged cans or poor-quality material fill the cans with gas, creating a hostile environment for bacteria.
Delving into details of pasteurization and sterilization uncovers aspects like the significance of food pH, optimum temperature, spoilage test, pasteurization products, etc. High school students are unaware of these details, and some might get dazed when they face complex information. We’ll discuss five practical strategies to help ease the learning process and make these topics more approachable for students.
Image from Pasteurization and Sterilization Virtual Lab.
Pasteurization and sterilization are temperature-based techniques with many intricacies, like how to use a pasteurization machine. What should be the optimum temperature and time for a given product to make it purified? Such aspects make students feel overwhelmed by the subject.
In food technology, heat treatment is applied to reduce or destroy microbial and enzyme activity. Therefore, it preserves food quality and ensures the safety of the food. Heat treatments like sterilization and pasteurization require working and handling high-temperature conditions. Some students might not pay attention and follow guidelines which could result in accidents. Contrary to this, some students might feel anxious and worried about hot stuff.
The growth of microbes, including yeast, molds, and bacteria, is prevented by very low or high pH. Many foods have a pH low enough to offer some protection against microbes' spoilage but not low enough to inhibit the microbe's growth completely. Yeast and molds can tolerate lower pH than most bacteria. The pH level of food also determines the time and temperature of the heat treatment it needs.
The difference between pasteurization and sterilization is tricky. It takes experience to identify and choose appropriate heat treatment. Some products need more extensive measures depending on the type of microbes. Also, the food packaging helps decide the process. For instance, canned food is often preserved for a more extended period of time; hence food sterilization is a better method. The temperate and time duration of heat treatment differs for each type of food or beverage.
Learning pasteurization and sterilization doesn't have to be burdensome; instead, it could be a fun experience for students and educators. Please review the five effective strategies discussed below and share them with your colleagues and students.
Storytelling is a great way to make lessons more exciting and fun for students. Introduce notable names behind the invention of these processes with highlights of their journey. It would make students appreciate the efforts of scientists and learn about their significance.
The technique of using heat to preserve foods dates back centuries when the term used for this process was “appertization.” Nicolas Appert pioneered the sterilization method, the French master confectioner and chef. He was a knowledgeable and passionate person. At the beginning of the 17th century, the French army felt the need for food that could be preserved for a longer time. They requested Appert to come up with a solution. He worked hard to solve this problem and founded the first commercial canning factory. Initially, the food was placed in glass bottles covered with cork and sealed with wax. These secured and sealed bottles were put in boiling water for hours or days. Continuous heating kills pathogens spoiling food, resulting in improved shelf life.
Pasteur used his knowledge of microbes and fermentation to report another remarkable invention named pasteurization. In 1863, the wine industries in France were near to collapse as wine quality was hard to maintain and often got contaminated. The emperor of France, Napoleon III, knew Pasteur's abilities and requested he looks at his problem. Pasteur realized that wine gets contaminated due to the presence of microbes. He performed a simple experiment in which he heated wine at 50-60 °C (120–140 °F), which killed these microbes and remarkably increased the wine quality. Since then, this heat-killing method has been used to preserve and purify many foods and beverages.
Scientific topics like pasteurization and sterilization with practical demands are understood better with hands-on experiments. An educational trip to processed milk factories or food packaging facilities would encourage students to learn more about the topic. Show them the operational mode of the pasteurization machine to better understand the flow of food products in different compartments of the device.
Acidity increases as the food spoil; thus, acidity can be quantified to measure food quality. Food becomes more acidic as the microbes' metabolism by-product increases. The pH level of food can be measured using pH electrodes/meters or titration. Checking the food's pH level is an exciting and easy-to-handle activity.
Make your lessons interesting with the help of real-world examples and exciting facts. Students appreciate learning about things related to the world around them. For instance, students are familiar with milk spoilage if it rests in the refrigerator for too long. Spark their curiosity by telling the science behind milk’s sour taste. Some milk bacteria survive pasteurization and may convert carbohydrates into acids, making the milk taste sour.
Older people, kids, pregnant women, and people with weak immune systems are more susceptible to falling sick with consuming unpasteurized food. In Canada, it is illegal to sell unpasteurized cheese. Check the label before buying cheese, and you always prefer pasteurized cheese. The unpasteurized juices are available in glass bottles with a concise shelf life. It is safe to consume these bottled juices but remember to check the expiry dates before enjoying your drink.
Inquiring is an integral part of the learning process. Questioning assists students in directing their learning as they strive to integrate existing knowledge and new information to make sense of these ideas. Some of the questions related to the topic are as follows:
What is boiling?
Do you know at what temperature milk boils?
Could bacteria survive temperature extremes?
What is the shelf life of bottled orange juice?
How many days would pasteurized milk stay fresh in the refrigerator?
Is honey pasteurized?
Some microbes don't die; instead, they stop growing in pasteurization. Won’t this make pasteurization a non-reliable technique of food preservation?
What is the advantage of using glass containers in food packaging?
A virtual laboratory simulation is a great way to teach pasteurization and sterilization. At Labster, we're dedicated to delivering fully interactive advanced laboratory simulations that utilize gamification elements like storytelling and scoring systems inside an immersive and engaging 3D universe.
Check out Labster's simulations for Pasteurization and Sterilization Virtual Lab. In this simulation, you’ll help an organic farmer increase his peach juice's shelf life. It would help you understand the basics of spoilage detection experiments in an interactive way. You’ll be able to decide which packaging and heat treatment are suitable for Adam’s peach juice.
Please take a look at the snippet below taken from the Labster simulations, or get in touch to find out how you can start using virtual labs with your students.