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Vacuum Cooling Explained

21/06/2018 11:37 AM

Energy savings | Reduced baking times | Increased quality | Increased Productivity | Longer shelf Life

Sometimes when traditional methods of production are replaced by more efficient or more hygienic technology the foods produced lose some of their attractive sensory quality. However, there are examples where modern technology improves products, as is the case with Revent's Vacuum Cooling System. Vacuum cooling baked goods has been experiencing a renaissance in recent years.

Vacuum cooling oven hot bakery products has been around for more than 40 years, but it is only recently that Revent has improved technology to a level where it has gained wide acceptance. Vacuum cooling/baking is suitable for all types of bakery products with a moisture/free water content of 5% and more.

The method offers numerous benefits: bakery products stay fresher longer, have a larger baked volume, more flavour and potentially less baking time. Products blast frozen after Vacuum Cooling often remain crispy when defrosted, i.e. Croissants.

Customers are often medium to large specialist bakeries however industrial demand is on the rise. Revent has developed a multi-level automated VC system for industrial applications. Innovative business people are the ones most interested.

Cost savings can be significant, for example, there can be significantly less shift hours worked, reduced wastage, and potentially cooling cost savings due to the high cost of usual methods like spiral coolers, blast chillers etc. Increased productivity is another advantage as baking times can be reduced*

What is Vacuum Cooling?

It’s all about the laws of thermodynamics. The answer is too detailed to explain in this brief document. Please see these Wikipedia article on Vacuum Cooling which explain in detail.

The “COOLING CURVE” is completely programmable in the Revent system and Revent systems go to pressures other systems struggle to get to which makes for a more efficient process. The pressure inside the Revent vacuum cooling chamber is reduced to approximately 4mbar (millibar)* This causes the boiling point of the “FREE” water remaining in the products to decrease. Because the free water is boiling it evaporates removing heat (energy) from the product. This process happens in the static cooling process only much slower and with more loss of moisture. The longer, slower cooling time also increases the risk of bacterial growth.

In practical terms, the products are baked for a shorter period then immediately transferred to the vacuum chamber where the firm crust forms completely and the bread cools down.

A rack of Par-Baked items straight out of oven cool down to approx. 25° in the vacuum chamber in about 3 minutes*, retain a better volume and appearance.

Baking products turn brown and crusts form due to the MAILLARD reaction. The colouring occurs relatively slowly and requires a lot of energy. Whilst fully baked products still require to be coloured this
can be achieved in a shorter time with higher baking temperature. The object is to have an acceptable crust colour and have the starches fully set.

Fully baked bread must then cool down to moderate temperatures (or be shock chilled/frozen) before it can be further processed, sliced & packed. Both processes - the drying of the crust and cooling - can be massively expedited through vacuum cooling.

Significantly increased demand is a result of high energy costs. Mechanical cooling requires time and energy.

Bread can stay fresh and crisp longer. Bread retains approx. 1-2% more moisture. Par-baked breads have a better appearance and structure.

Any loss of flavour compared with normal cooling has not been detected, in fact it is often an improvement. Additional advantages are a 15-20% shorter baking time, which lowers overall energy requirements and frees up baking capacity, shock cooling of par-baked bread is no longer necessary, par-baked small loaves, croissants and cakes should have a lower spore count for longer than if they were cooled via more “traditional methods”.

It is claimed that by some that packed bread can be stored for longer periods* (extended shelf life) with reduced risk of mould as products are cooled through the “danger zone” quicker and bread can be sliced and packed in 7-10 minutes after baking.

The space required is similar to that of a rack oven and costs of purchasing extra ovens to cope with capacity could be postponed.

A further use for vacuum baking is the production of crust-less bread, for example, club sandwich bread. The bread in the baking tin is transferred to the vacuum chamber immediately after baking to a light or no colour, where it is ‘finished’ or ‘gelatinised’. The usual process is to bake the bread with a crust and then cut the crust off, resulting in considerable waste.

In summary, Baked or Par baked products can be baked for a shorter time. Vacuum Cooling lowers the core temperature in the baked product in minutes allowing sliced or packed almost immediately. The loaves no longer need to be stored in an acclimatised room for hours or passed through expensive, energy hungry refrigerated coolers. There are many references around the world and online or if you would like more information please ask.

Find out more about the Revent's Vacuum Cooling System. If you would like more information or would like a demo, Give us a call at 0800 503 335 or email us at WebOrders@SouthernHospitality.co.nz to find out more.

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Southern Hospitality Ltd