How Does Hot Fill Packaging Work ?

n the conveyor belt glass bottles. factory shop for the production of glass bottles and beverage
Photo by Albert Karimov, c/o

If you have ever needed to stabilise a beverage or sauce, then hot-fill is one processing method that you must have thought about. The technique is simple: a hot-filling process involves sterilising a product usually with heat, which is then filled into a container so that the residual heat also sterilises the package’s internal surfaces and the cap which is then fitted. Hot-filling is a secure method of ensuring a product becomes safe to consume and also prolongs its shelf-life. It does so by reducing the level of harmful bacteria in a product along with those associated with the packaging which would not only make the product unsafe but damages or contaminates it too. The process always extends the shelf-life which means less product is wasted.

Hot-filling is often performed with glass containers but some very tough plastics too can withstand the sort of heat processing temperatures that sterilisation needs to thoroughly treat both product and pack. Generally, products which you can see in these examples are fluids or pastes are one which already have some hurdles to promoting bacterial or mould growth such as a pH below 4.5 are often used. The types of product sterilised this way include:-

  • Soft drinks
  • Nectars and juices
  • Soups
  • Sauces
  • Water and flavoured waters
  • Sports, isotonic, hypotonic and hypertonic drinks
  • Vegetable and fruit juices
  • marinades

Solid products such as meat, whole vegetables or any other type which is solid will not be suited to hot-filling.

The Way Hot-Filling Technology Works

Hot-filling typically involves heating the product to a temperature of at least  91-93 degrees Centigrade or 194 degrees Fahrenheit for a few seconds, or at 71 degrees Centigrade for a few minutes (usually 15 minutes). This is designed to kill micro-organisms in the product or at least reduce them to a safe level. The heated product is then filled into the bottle which is closed with a cap and then turned upside down or on its side so that all internal surfaces including the cap are exposed to the hot liquid. The process is carefully controlled to avoid cold spots because any temperature drops which do not thoroughly reduce the number of harmful bacteria can produce a potentially unsafe product through incorrect sterilization. Hot-fill is generally effective against spores in particular which are the more robust form you might find a microorganism in.

What Types of Packaging Are Used

 Glass has always been a traditional material for this type of process. PET bottles are able to withstand some very high temperatures but other plastics are too brittle to take high heat. Whilst there are environmental concerns to plastic, such bottles made of this material are becoming reusable and less expensive to make.

The Benefits of Hot-Filling With PET Bottles

A number of benefits occur using hot-fill with PET bottles to ensure the safety of your product. Among them are the following:

  • Consumers can consistently trust the safety of the product
  • Products have a longer or more robust shelf life
  • No preservatives are needed and the product remains as natural as possible
  • PET bottles are light weight and easier to transport than glass
  • PET bottles are more cost effective than glass
  • Taste, vitamins, and nutrients are preserved with this process

Issues With Hot-Filling

  • Over heating causes nutrient losses especially with heat-sensitive vitamins.
  • Colour losses
  • Flavour and aroma losses
  • Incorrect sterilisation temperatures.
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