How do you safely package food using thermal processing?

1 Types of thermal processing

There are different types of thermal processing, depending on the temperature, time, and pressure applied to the food. The most common ones are pasteurization, sterilization, and canning. Pasteurization is a mild heat treatment that reduces the number of spoilage and pathogenic microorganisms, but does not eliminate them completely. It is suitable for foods that are refrigerated or consumed within a short time, such as milk, juice, and beer. Sterilization is a more intense heat treatment that destroys all microorganisms and spores, making the food shelf-stable for a long time. It is suitable for foods that are stored at ambient temperature, such as canned vegetables, fruits, and meats. Canning is a form of sterilization that involves filling and sealing containers with food and then heating them in a retort or a water bath.

2 Principles of thermal processing

The main principle of thermal processing is to achieve a certain level of microbial safety and stability for the food product, without compromising its quality and acceptability. To do this, you need to consider the following factors: the type and characteristics of the food, the type and level of microorganisms present, the type and size of the container, the type and intensity of the heat source, and the cooling method. You also need to measure and record the temperature and time of the thermal process, and verify that it meets the required standards and regulations.

3 Thermal process design

To design a thermal process for your food product, you need to follow these steps: first, identify the target microorganism that poses the greatest risk or challenge for your food, and determine its heat resistance and growth potential. Second, conduct thermal death time (TDT) studies to find out how long it takes to kill a certain percentage of the target microorganism at a given temperature. Third, calculate the process lethality or F-value, which is the equivalent time in minutes at a reference temperature (usually 121.1°C or 250°F) that delivers the same amount of microbial destruction as the actual process. Fourth, select the appropriate type and size of the container, and ensure that it can withstand the thermal process and provide an adequate seal. Fifth, choose the best heating and cooling method for your food product, such as steam, water, air, or oil, and optimize the heat transfer and distribution within the container. Sixth, validate and evaluate your thermal process using methods such as temperature sensors, computer simulation, or microbiological testing.

4 Quality aspects of thermal processing

Thermal processing can have both positive and negative effects on the quality of food. On one hand, it can enhance the color, flavor, texture, and nutrient availability of some foods, such as tomatoes, corn, and beans. On the other hand, it can cause undesirable changes such as browning, softening, loss of vitamins, and formation of off-flavors and toxic compounds in some foods, such as milk, meat, and fruits. To minimize the quality deterioration of food during thermal processing, you need to consider the following aspects: the composition and pH of the food, the presence and activity of enzymes, the type and concentration of additives, the packaging material and headspace, and the storage conditions.

5 Safety aspects of thermal processing

Thermal processing can also pose some safety hazards for the food and the operator. The main ones are: thermal shock, which is the sudden change in temperature that can cause the container to crack or explode; botulism, which is a rare but deadly form of food poisoning caused by the toxin produced by Clostridium botulinum, a spore-forming bacterium that can survive and grow in low-acid, anaerobic, and moist conditions; and recontamination, which is the introduction of microorganisms or foreign materials into the food after the thermal process, either through leaks, punctures, or improper handling. To prevent these hazards, you need to follow the good manufacturing practices (GMPs) and the hazard analysis and critical control points (HACCP) principles, and monitor and inspect your thermal process and product regularly.

6 Future trends of thermal processing

Thermal processing is constantly evolving and improving to meet the changing needs and demands of the consumers and the industry. Some of the future trends of thermal processing are: novel technologies, such as microwave, ohmic, and high-pressure processing, that can achieve faster and more uniform heating, lower energy consumption, and better quality retention; smart packaging, such as active, intelligent, and edible packaging, that can extend the shelf life, indicate the freshness, and enhance the functionality of food; and personalized processing, such as 3D printing, that can create customized food products with different shapes, textures, flavors, and nutritional profiles.

7 Here’s what else to consider

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