Improving the mould free shelf life of bakery products
Posted: 24 August 2016 | | 1 comment
Mould free shelf life (MFSL) is a critical parameter in the bakery industry. Formulation and parameters such as Aw and the use of preservatives such as propionates and sorbates are traditionally used to ensure the length of MFSL is acceptable to consumers, retailers and manufacturers.
However, the current trend to reduce or eliminate the use of ‘artificial’ preservatives and the rise of organic foods is challenging the traditional methodologies.
A number of new technologies and processes can help bakers extend their MFSL without the use of preservatives, or with reduced quantities. These include infra red, ultra violet light, vacuum cooling, cold plasma and sourdough systems. This article will examine each technology/ process in turn and discuss the associated benefits and drawbacks.
Vacuum cooling is a rapid evaporative technique that can be used for various foods and vegetables1. The major characteristic of vacuum cooling that benefits MFSL is that the product can be cooled extremely quickly whilst enclosed in a chamber.
It works according to the principle that when liquid evaporates, it needs to absorb heat to reach the higher energy level of molecular movement in the gaseous phase2. The amount of energy required is called latent heat. Water boils at 100°C at a pressure of 1 atmosphere, however a pressure reduction will cause the water to boil at a lower temperature. The resulting vapour generated during vacuum cooling is then removed by vacuum pump3.
Most vacuum cooling apparatus are operated in batch-wise processes. Products with a raised temperature are placed in a vacuum chamber soon after baking. When the vacuum pump is switched on, air is evacuated and the chamber pressure starts to decrease. As soon as the saturation vapour pressure corresponds to the temperature of the product, water inside the product begins to boil and latent heat is released. This causes the temperature of the product to decrease rapidly.