You may have heard of the term hot filling, but do you know what the benefits are and why it is so widely used in automated fill lines these days?
Hot filling is a process of choice for many juices and beverages because it eliminates the need of preservatives and chemicals while maintaining the same level of shelf life and nutritional properties of the beverage. With consumers becoming more aware of potential harmful effects of preservatives, hot filling is now the obvious choice as the process is rather simple and less complex compared to it's alternatives.
Hot filling is generally suitable for fruit juices, vegetable juices, flavored waters, and sports drinks that have a pH level of < 4.5.
The Process of Hot Filling
The process of hot filling involves several steps, each step is essential to maximize the benefits of shorter fill time and extended shelf life without preservatives.
- The beverage is pasteurized and heated to the hot filling temperature, generally between 190 - 203 F (or 90 - 95 C) in a heat exchanger for at least 15 - 30 seconds. This process typically kills all microorganisms in the liquid.
- The liquid is cooled to around 180 - 185 F (82 - 85 C) and filled at the filling station. In some cases, nitrogen is introduced into the head space (the empty space between the liquid and the brim) to remove oxygen in order to avoid oxidation. The closure is then applied immediately after. This process will sterilize the inner surface of the container.
- The container is either tilted on to one side or inverted to ensure the closures is also sterilized with the hot liquid touching the inside surface.
- The container / closure package is then brought to a cooling station (water bath or shower) to cool it rapidly, this process will help preserve the product taste and nutritional properties. The cooling process will also create a vacuum inside the container, preventing microbial growth.
- The cooled bottle / closure package is dried and decorating label is applied.
Bottles Options When it Comes to Hot Filling
It is important to note that not all bottles are hot fill compatible. A quick review of our Which Plastic Is Right For Me Infographic
reveals that most common plastic resin cannot withstand hot filling temperatures (Refer to Temperature Tolerance characteristics section for details). However, there are common technologies that will enable a specific type of PET plastic to be hot fill compatible. They are generally referred to as "Heat-set PET".
Heat-set PET is now a common plastic container type in many hot fill beverage applications. They are specifically made to withstand hot-fill temperatures, in some cases up to 192 F, while maintaining clarity and lightweight characteristics. PET is also recyclable, making it a good alternative to glass, which is also hot fill compatible. We have compiled a short (not exhaustive list) of heat-set PET bottles here
as a reference.
In Review : The Benefits of Hot-Filling
There are many options, and considerations, when it comes to hot-filling your beverage, such as barrier properties required, UV coating to reduce sunlight reaction and extend shelf life. It is best to consult with an knowledgeable expert to find a proper match for your product.
In summary, hot-filling is a good option for many fruit and vegetable juices, water enhancing and tea drinks as it eliminates the need of preservatives, while preserving ambient temperature shelf life of 6 - 12 months, and stock available hot-fill compatible containers are readily available these days making the process more feasible than before. While the aforementioned shelf life is merely an estimate, the duration is actually determined by the oxygen barrier sensitivity of the beverage, size and type of beverage bottle, and storage conditions.