Ultra High Temperature Treated Milk

Technical Field

It is presented methods and apparatuses related to the field of processing liquid food products using heat treatment, for instance, ultra high temperature (UHT) treatment of milk.

Background

It has been found that when heat treating milk in order to kill unwanted microorganisms by using so-called ultra high temperature (UHT) treatment and later filling the UHT treated milk in a bottle or similar package, an unpleasant smell may occur when opening the bottle. Though a smell may be an indication that the milk is not feasible to drink, this is not always the case. Instead the smell may be an effect of that substances that are non-harmful are gathered in large concentrations in a head space of the bottle and when opening the bottle these are all at once posed to a person opening the bottle for drinking the milk. Since an unpleasant smell is not placing the product, in this case the milk, in a favorable position, it is in the interest of the dairy or food producer to change the process, if possible, to avoid that this smell occurs.

The problem with unpleasant smell also occurs in other kinds of packages holding UHT milk, for instance packages from roll fed carton based systems, such as the Tetra Brik™ system, with no or little head space, but often to a less extent. However, when a part of the milk is poured out, for instance before applying an opening device to the package, head space will be formed and the same problem appear also in this type of package.

Therefore, in particular when using packages with head space like bottles, a blank fed system or any other system in which packages are filled separately with UHT milk or any other product that can cause air born substances that can cause unwanted smell in the head space of the package, there is a problem.

Summary

Accordingly, the methods and apparatuses described herein preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above mentioned problem.

According to a first aspect it is provided a method for processing a liquid food product, such as milk, said method comprising injecting a gas comprising at least one oxidizing agent to said liquid food product, and heat treating said liquid food product.

When using the method creation of sulphur based components can be prevented. If said product contains omega 3 fatty acids and/or vitamins, when using the method creation of sulphur based components can be prevented without affecting a concentration of omega 3 free fatty acids and/or vitamins.

The method may further comprise de-aerating said liquid food product in order to remove at least part of said gas injected to said liquid food product.

The oxidizing agent may be oxygen.

The gas may have an oxidizing agent concentration of 3-10%.

The liquid food product may be heat treated by using ultra high temperature treatment.

The liquid food product may be heat treated by using a direct steam injection device.

The liquid food product may be de-aerated in a flash vessel.

According to a second aspect it is provided a system for processing a liquid food product, such as milk, said system comprising an injection device arranged for injecting a gas comprising at least one oxidizing agent to said liquid food product, and a heat treatment device arrange to heat treat said liquid food product.

The system may further comprise a de-aerator arranged for de- aerating said liquid food product in order to remove at least part of said gas injected to said liquid food product. The gas comprising at least one oxidizing agent may be oxygen.

The gas may have an oxidizing agent concentration of 3-10%.

The heat treatment device may be arranged for ultra high temperature treatment.

The heat treatment device may be a direct steam injection device.

The de-aerator may be a flash vessel.

According to a third aspect it is provided a liquid food product produced according to the method according to the first aspect.

According to a fourth aspect it is provided a method comprising processing said liquid food product according to the first aspect, and filling said liquid food product into a package.

The package may have an open end through which said liquid food product is filled, and said method may further comprise closing said open end of said package.

Brief description of the drawings

The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, wherein:

Fig 1 a-1 c illustrates an example of how a carton bottle can be filled with a liquid food product.

Fig 2 illustrates an example of a system for UHT treatment of milk.

Fig 3 is a flow chart showing steps of a method for processing a liquid food product.

Detailed description of preferred embodiments

There are different ways of filling a bottle, or bottle-like package, with a liquid food product. In case of having a PET bottle, the PET bottle is formed, thereafter filled with the liquid food product via a spout and finally closed with a cap. In case of having a carton bottle package, such as Tetra Evero™, another approach may be used. Due to that the package is produced in a different way than the PET bottle the approach for filling a carton bottle usually differ from the same process for filling the PET bottle. The most significant difference is an effect of that the carton bottle is formed by first making a carton sleeve, e.g. by folding a carton blank around a mandrel and making a longitudinal sealing, and then forming a plastics upper part, comprising a shoulder portion, a neck portion and a lid, by injection molding this onto to the carton sleeve. After having formed the upper part of the carton bottle, while keeping this upside down, it can be filled via a not yet closed bottom of the carton bottle. After having filled the carton bottle, and sealed and formed the bottom, the carton bottle can be turned and fed downstream to secondary packing.

In fig 1 a it is illustrated a general example of a carton bottle 100 comprising a sleeve portion 102 made of a carton, being provided with plastics layers and an Aluminum layer, and an upper portion 104 made of plastics, such as HDPE and/or LDPE.

In fig 1 b it is disclosed a general example of the carton bottle when this has been filled with the liquid food product via the open bottom of the package.

In fig 1 c it is disclosed a general example of the carton bottle when the bottom has been sealed and formed, and the carton bottle has been turned to an upright position.

Fig 2 generally illustrates an example of a system 200 for UHT treatment of milk using a direct steam injection device. Instead of using a direct steam injection device, other types of UHT heat treatment devices can be used as well, such as steam infusion devices or tubular heat exchangers only to mentioned a few.

There are generally two different types of systems for UHT treatment of milk, direct UHT sytems and indirect UHT systems. The direct UHT systems could for instance be a so-called steam injection based UHT system in which hot steam is injected to the milk in order to provide for that this is rapidly heated to about 140 degrees C and kept at this tempeature for a few seconds before it is cooled down rapidly, for instance by using a vacuum vessel, also known as a flash vessel. Alternatively, the direct UHT system could be a so- called steam infusion based UHT system in which the milk is heated rapidly by injecting this into a steam chamber, instead of injecting the steam into the milk. An indirect UHT system can use a tubular heat exchanger for heating the milk to about 140 degrees C. An advantage with using an indirect UHT system is that less energy is needed compared to a direct UHT system. A disadvantage is that the milk is not as rapidly heated as in the direct UHT system, which has the effect the taste of the milk is to a higher degree is affected in the indirect UHT system compared to the direct UHT system.

More in detail, in the direct UHT system illustrated in fig 2, milk is transferred into the system 200. In order to compensate for an uneven flow of milk a balance tank 202 may be used. From the balance tank 202 the milk can be transferred via a feed pump 204 to a plate heat exchanger 206, or alternatively a tubular heat exchanger, for pre-heating the milk. The milk can at this stage be pre-heated to about 80 degrees C, i.e. above pasteurization temparature, in order prevent growth of unwanted microorganisms or at least keep this growth at a low level. The plate heat exchanger 206 can be divided in different sections, and hot water may be used as a heat transfer media when heating the milk and cooling water may be used the heat transfer media when cooling the milk. Although not illustrated in fig 2, the plate heat exchanger 206 may be a so-called regenerative plate heat exchanger using milk in a late stage of the process to be cooled down for heating milk in an early stage of the process to be heated.

As can be readily understood by the skilled person in the art, the system 200 illustrated in fig 2 is only one out of many different possibilities when designing a UHT plant. For instance, as indicated above, different types of heat exchangers can be used.

Before or after having pre-heated the milk oxygen may be added by using an oxygen injection device 208. By introducing a small amount of oxidative gas (for example oxygen in 3 - 10% concentration), or put differently a gas comprising at least one oxidizing agent, an amount of substances causing unwanted smell, e.g. thiols, can be reduced.

By only introducing this small amount of oxygen the unwanted smell can be avoided at the same time as e.g. vitamin C and omega 3 fatty acids are not significantly affected. The reason for this is that thiols have a higher affinity to oxygen compared to e.g vitamin C and omega 3 fatty acids.

In the particular example illlustrated in fig 2, after having injected oxygen in the milk this is transferred to a steam injection head in which hot steam is injected into the milk. The steam injection head may be a so-called ring nozzle steam injector used, for instance, in the solution Tetra Therm Aseptic VTIS™ marketed by Tetra Pak.

In order to make sure that the milk is kept at a temperature above 135 degrees C and at least 1 second, or any other combination of temperature and time decided by the operator or stipulated by food safety regulation, a holding tube 212 may be used.

After being fed from the holding tube 212 the UHT treatment of the milk is finalized and the milk is transferred to a vacuum vessel 214, or flash vessel, in order to flash cool the milk. One reason for flash cooling the milk is in order to make sure that steam introduced by the steam injection head 210 is removed from the milk. In order to control the amount of vapour, or steam, that is removed a vacuum pump 21 6 may be used.

A side effect of the flash cooling is that added oxygen is also removed from the milk. In other words, when flash cooling the milk this will at the same time be deaerated. Therefore by adding oxygen just before the steam injection head 208, the added oxygen will only be in the milk during the UHT treatment when the risk that thiols are formed is high, but not before and after when there is a risk that the oxygen may react with vitamins and omega 3 fatty acids and as an effect reduce the concentration of these in the milk.

After having flash cooled the milk, this can be fed via a centrifugal pump 218 to a homogenizer 220 arranged for aseptically homogenizing the milk. Thereafter, the milk may pass through a different section of the plate heat exchanger 206 before being transferred to an aseptic tank 222 or a filling machine 224, such as Tetra Pak A6™ marketed by Tetra Pak or other filling machine arranged to fill bottles, such PET bottles, carton bottles or any other package where thiols can be gathered in the head space.

In order to clean the system 200 an Cleaning In Place (CIP) tank 226 may be used. By adding oxygen or any other oxidative agent into the milk less sulphur based components, like thiols, will be formed with the positive effect that less or no unpleasent organoleptic properties, such as smell and taste, will occur when opening the package and drinking the milk. One reason for this is that the sulphur based components are oxidized by the added oxidative agent, e.g. oxygen.

In alternative embodiment, the oxidizing agent, such as oxygen, is added before the milk is pre-heated, that is, after the feed pump 204, but before the heat exchanger 206. In one test, using this alternative

embodiment, 2,5 l/min of oxygen at a pressure of 5,3 bar was added to the milk, being at a temperature of 9,3 degreees C and flowing at 4000 l/h, with a good result in terms of reduced number of sulphur based components in the milk after UHT treatment. In another test, using the same embodiment, 5,0 l/min of oxygen at a pressure of 5,7 bar was added to the milk, being at a temperature of 8,7 degrees C and flowing at 4000 l/h, also with good results in terms of reduced number of sulphur based components in the milk after UHT treatment.

Fig 3 generally illustrates a method 300 for preventing smell in UHT milk that may be part of a method for processing a liquid food product, such as UHT milk.

In a first step 302 oxygen is added to the liquid food product.

In a second step 304 the liquid food product is heat treated.

Optionally, in a third step 306 the liquid food product is deaerated in order to remove the added oxygen, or at least a part of it. This step may be combined with the step of flash cooling the liquid product in order to remove vapour added in the heat treatment step when this is made by using steam injection.

Optionally, in a fourth step 308, before adding oxygen, the milk may be pre-heated to e.g. about 80 degrees C.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.