Blast chilling should now be used in all commercial restaurants, cafes and bistros; basically anywhere that prepares and serves food to the public. When blast chilling first came about it was not compulsory by law to integrate this practice into daily routines however as the concern for safe guarding the public against potentially harmful bacteria was addressed, the law stated that blast chilling was in fact obligatory to any food preparation businesses which plan to later regenerate pre-prepared foods. But what is blast chilling and how has it come about?
What is blast chilling?
Blast chilling is a term used to describe the method of cooling food to a low temperature quickly meaning that it passes through the food danger zone quickly therefore harmful bacteria is not given the opportunity to develop and multiply. Much research was undertaken in this area and the results proved useful in determining how the blast chiller should work and the temperature boundaries it must meet. The data found also highlighted the speed at which the food items must be taken to the desired temperature. Bacteria multiply fastest between 8˚C/46˚F and 68˚C/154˚F. This information allowed researchers to deduce that a blast chiller must be able to reduce the core temperature of cooked food from 70˚C/158˚F to 3˚C/37˚F or below within the time frame of a maximum of 90 minutes. By following this practice, the food is considered safe to store for consumption at a later date. Although this method of chilling food safely and effectively was originally designed for commercial food premises however was later also incorporated into the preparation and production of ‘instant’ foods, ensuring that the quality of the product remained as tasty after storage as it was when fresh.
The origins of blast chilling
The idea for the design of the blast chiller was taken from the refrigerator theory and these two products are therefore often thought of as cousins. Prior to the invention of what we now recognise as the refrigerator, people would have to use preservation techniques such as soaking in salt or brine and storing in ice houses to ensure that the food remained as fresh as possible. It was not until 1842 with the invention of the refrigerator, although in a simple and less technical form, that these methods of preservation were abandoned. By 1880 the first frozen cargo of food products managed to reach British shores from Australia safely and without being compromised. By the beginning of the 20th century, people were beginning to discover that the idea of blowing cold air over the surface of food ingredients was highly effective as a method of quick freezing and therefore allowing safer storage of food which was to be used at a later date. The idea of the refrigerator storing food at a consistent low temperature gave way to designers and inventors taking the basic concept and creating a way to speed up the process so that food could be chilled to a safe temperature in as short a period of time as possible. This led to the birth and commercialisation of the blast chilling practice being an essential part of the food industry. Blast chillers, as with all high grade pieces of equipment, can be pricy to purchase and thus makes them more easily accessible to commercial properties and food businesses rather than for occasional and unnecessary use in the domestic environment.
The science bit
Many people, often those who deal with the expense of having to invest in these pieces, often wonder what makes blast chillers more effective than an ordinary freezer. Why should they invest large sums of money for something which can also seemingly be achieved with a large scale domestic item? Well, the method involved in the blast chilling process, although appearing to achieve the same effect as a piece of domestic equipment does actually differ although it is not noticeable to the naked eye. It is this difference which makes the blast chilling process truly unique and a must have for any commercial food business. When food is stored in a domestic freezer the water held inside becomes frozen; these crystals being relatively large in size. A blast chiller promotes a rapid freezing process, the result being that the crystals formed inside the foods are much smaller. The size of the frozen crystals which form can have a dramatic effect on the food once it is thawed. Larger crystals will rupture the cells of the food as they melt therefore having a detrimental effect on the overall flavour and texture of the item. The thawing of smaller crystals does not have the same impact on the food meaning that the taste and texture is preserved. All blast chillers work on the same basic principle of passing a constant flow of chilled air over the surface area of the food and so speeding up the whole process. Some blast chillers now also incorporate changeable shelving which means that the user can tailor the space provided by moving the shelving higher or lower, to suit each individual piece of food which they wish to chill.
So other than the size of the crystals which are formed internally within the food, how does a blast chiller differ from a domestic appliance? With standard refrigeration and freezer compartments, food is often stacked one above the other with the air being circulated often becoming stagnant. The cool air being pumped into the compartment not only has to cool the food but also chill the stagnant air surrounding the ingredients. It is this factor which increases the amount of time needed to chill foods in a domestic setting. This is the issue which needed to be addressed when the first blast chillers were being designed. How could the time required to chill items be reduced? The differing arrangement of blast chillers from their domestic refrigeration cousins proved to be the answer to decreasing the amount of time needed to complete the task. Blast chillers have a larger space between the trays meaning that the chilled air has more room to circulate. The cold air is also being pumped continuously around the chamber rather than being allowed to stagnate and so warm up.
Blast chillers also have different chilling modes rather than only being placed at one setting.
- Soft chill
This setting chills the core temperature of foods quickly and effectively down to a range of approximately 3˚C. It is best used for delicate items which have a low density such as green salads for example.
- Hard chill
This setting is more suitable for food products with a higher fat content such as cuts of meat, broths and portioned meals. The temperature of the food will fall to approximately -15˚ within a short a period of time as possible.
- Shock freezing
Shock freezing can reduce the core temperature of high risk foods to a temperature of approximately -18˚C in around 4 hours. This prevents any harmful bacterium from forming on foods which are known to produce and grow bacterium more quickly.
As with all pieces of equipment there are advantages and disadvantages which must be taken into consideration when researching the best model for your business. Overall the positives far outweigh the negatives as you are guaranteed to be storing and later serving safe food products to your customers.
- The smaller crystal formations result in the texture, flavour and colour of the food being locked in and preserved. The nutritional value will also not be lost as is the case when dealing with some domestic units.
- The rapid cooling encourages an ‘ice skin’ to form on and around the food product meaning that more delicate items which would normally suffer aesthetically from the freezing process will be preserved in a much more effective fashion. Fruit extracts, certain pasta dishes and soufflés for example are prone to suffering from dehydration and thus the physical appearance of the piece once taken out of storage is badly affected. The ‘ice skin’ acts as a perfect barrier to prevent these problems from arising.
- The speed at which the ingredients are chilled guarantees 100% food safety and effectively inhibits the growth of any potentially harmful microorganisms from developing.
- Blast chillers will often be designed with different compartments therefore the risk of cross contamination is greatly reduced.
- As the size of blast chillers is relatively large they can handle greater quantities of food. This ensures that food waste is kept to a minimum and the chef has a greater choice of ingredients for use in the future.
- The final result of thawed pieces which were blast chilled is overall more effective and of better quality. The structure remains the same as when fresh and the integral features are not hindered in any way.
- Blast chillers are expensive to purchase and therefore must be factored into the initial set up budget and costs.
- The amount of energy required to run these pieces can be high and so lend themselves mainly to businesses as opposed to domestic settings.
Capable of blast chilling from 70˚C – 3˚C in 90 minutes, the compact design sits neatly in both large and small kitchens.
Blast chillers are now an essential piece of equipment for any commercial food business which stores food ingredients on a daily basis. Not only do these units guarantee that the products which you are storing will be kept in almost fresh condition with regards to nutritional value, colour, taste and texture but you are also assured that there will be no future risk of any unwanted bacteria being passed to your customers. These items are now a legal requirement in commercial kitchens and although they may be costly to purchase the reward of safety and quality that they offer will be well worth the investment.