PROCESS AND APPARATUS FOR PACKAGING A FLUID FOOD PRODUCT CONTAINING SOLID PIECES

Technical field

The present invention relates to a process and an apparatus for packaging a fluid food product containing solid pieces.

The prior art comprises the practice of sterilisation by autoclave of packages of fresh or dry food products having low acidity packaged in glass jars, or in containers made of tinplate or flexible cardboard containers (known in the sector as "retort").

In this context, the expression "low acidity" relates to products having a pH greater than 4.5.

Background art

As it is known, for solid foodstuffs having low acidity, such as cubed fruit, legumes, nuts etc. in water- or oil-based liquid, pasteurisation alone is not sufficient to eliminate the pathogenic micro-organisms constituting a risk for the health of the consumer.

Containers filled and closed are then placed in an autoclave for a time necessary for completing the sterilisation (for example 40 minutes) and at a suitable temperature according to the pre-selected product.

Products sterilised in an autoclave remain whole since they are not moved significantly during the heat treatment. As they are treated at high temperatures and for an adequate time, these products have high preservation times.

PET containers, differently to glass and tinplate, are not suitable for treatment in an autoclave. In fact, PET containers are not able to withstand temperatures higher than 65°C. Where packaging is done using PET containers, the product must therefore be sterilised prior to filling, by means of a UHT treatment (acronym of "Ultra High Temperature").

This treatment, however, has the drawback of compromising the integrity of the solid parts of the product, which tend to reduce to mush or in any case lose their wholeness, much appreciated by the consumer.

A solution utilising UHT treatment is described in US 5,972,405. It comprises, on conclusion of the thermal sterilisation process, the final product transiting into a cooling apparatus able to reduce the temperature to about 21 °C prior to filling the PET containers. This solution is very expensive from the energy-consuming point of view as it requires lowering the temperature of the whole final product to 21 °C.

Even the ohmic heating used as an alternative to direct or indirect heat treatment (UHT) has a destructive effect on the solid parts, due to the high thermal excursion imposed on the product, which is rapidly brought to a high temperature (about 140°C) and then cooled to around 20°C. Though the heating is very rapid and managed carefully, the step of heat pause and especially of cooling - very prolonged - risk compromising the integrity of the solid parts.

Disclosure of the invention

In this context, the technical task underpinning the present invention is to disclose a process and an apparatus for packaging a fluid food product containing solid pieces, which obviate the drawbacks of the prior art as described in the foregoing.

In particular, the aim of the present invention is to provide a process and an apparatus for packaging a fluid food product containing solid pieces, which enable maintaining as far as possible the integrity of the product contained, i.e. preserving the solid consistency of the food.

The specified technical task and the set aims are substantially attained by a process for packaging a fluid food product containing solid pieces, comprising the steps of:

- boiling under high pressure, i.e. in a condition of overpressure with respect to the external environment, a first fluid mixture formed from the solid pieces and a first fluid;

- lowering the temperature of the first fluid mixture maintaining in any case the first mixture in a condition of overpressure relative to the external environment;

- providing for a sterilising thermal treatment for a second fluid;

- after the thermal treatment, cooling the second fluid to a temperature of lower than 60°C;

- once the second fluid has cooled, introducing a pre-established quantity thereof into the first fluid mixture so as to obtain said fluid food product;

- introducing a pre-established quantity of the fluid food product into a PET container.

For example, the solid pieces are selected from among: pieces of fruit or vegetables, or cereals, or legumes, or nuts, or aloe cubes, or hydrated basil seeds, or grass jelly.

For example, the first fluid is water or a mixture based on water or tea or milk.

The second fluid can be for example milk or fruit juice or tea or broth.

During the high-pressure boiling step, the first fluid mixture is preferably constantly mixed.

A step of introducing a pre-established quantity of the second fluid into the PET container (already partly filled with the fluid food product) is preferably included so as to dilute the fluid food product.

In a preferred embodiment, the step of lowering the temperature of the first fluid mixture consists in evacuating part of the vapour produced by boiling. The specified technical task and the set aims are substantially attained by an apparatus for packaging a fluid food product containing solid pieces, utilising the above-described process and comprising:

- a pressure tank configured to bring said first fluid mixture to boiling under pressure;

- a sterilising thermal treatment unit of the second fluid;

- an additional tank containing the second fluid;

- at least one conduit configured to put said additional tank in selective communication with said pressure tank; - at least a first filling valve communicating with said pressure tank in order to deliver a pre-established quantity of fluid food product into the PET container.

The apparatus preferably comprises mixing means (of known type) for mixing the first fluid mixture.

The apparatus preferably comprises a second filling valve communicating with the additional tank for delivering the pre-established quantity of the second fluid into the PET container.

In an embodiment, the apparatus comprises a sleeve external of the pressurised tank. A fluid at a temperature such as to cool the first fluid mixture circulates in the external sleeve.

Brief description of drawings

Further characteristics and advantages of the present invention will more clearly emerge from the non-limiting description of a non-exclusive but preferred embodiment of a process and an apparatus for packaging a fluid food product containing solid pieces, as illustrated in figure 1 , which represents a simplified schematic view thereof.

Detailed description of preferred embodiments of the invention

With reference to the figures, reference numeral 10 denotes an apparatus for packaging a fluid food product 1 containing solid pieces 3.

The fluid food product 1 is preferably a product having low acidity. In this context, the expression "low acidity" relates to products having a pH greater than 4.5.

The process for packaging the fluid food product 1 first includes a step of boiling under high pressure, i.e. in a condition of overpressure with respect to an external environment, a first fluid mixture 2 formed from solid pieces 3 and from a first fluid 4.

For example, the solid pieces 3 can be selected from among: pieces of fruit or vegetables, or cereals, or legumes, or nuts, or aloe cubes, or hydrated basil seeds, or grass jelly.

For example, the first fluid 4 is water or a mixture of water and one or more food thickeners (edible gums such as xanthan gum, gellan gum, carboxymethyl cellulose) or a tea- or milk-based fluid, possibly with one or more edible food thickeners added.

The weight ratio between solid pieces 3 and first fluid 4 in the first fluid mixture 2 depends on the type of final food product 1 that is to be obtained.

For some types of product 1 , prior to the step of high-pressure boiling a step of pre-cooking of the solid pieces 3 is included.

The step of boiling the first fluid mixture 2 at high pressure is carried out inside a pressure tank 1 1 .

During the high pressure boiling step, a temperature of about 120°C is reached, and maintained for a time lapse that is predefined according to the product 1 to be obtained.

During the high-pressure boiling step, the first fluid mixture 2 is preferably continuously mixed in order to facilitate a uniform heating. In particular mixing means 12 are included for mixing the first fluid mixture 2 configured for realising an extremely delicate mixture which prevents damage to the solid pieces 3. For example, the mixing means 12 are mechanical agitators of known type.

On conclusion of the predefined time lapse, the temperature of the first fluid mixture 2 is lowered while maintaining the first mixture 2 always in a condition of overpressure relative to the external environment. For example, a part of the steam produced by the boiling can be evacuated. This is obtained by allowing a part of the steam to be released from the pressure tank 1 1 , up to reaching a temperature which is however maintained constantly above 90°-100°C (for example 105°-1 10°C).

Alternatively, the temperature can be lowered by providing an external sleeve in which, for example, water glycol circulates.

In the meantime, a second fluid 5 is subjected to a thermal sterilising treatment in a special thermal treatment unit 13. The thermal treatment unit 13 is preferably configured for carrying out a UHT treatment. The second fluid 5 can be for example milk or fruit juice or tea or broth. Following the UHT treatment, the second fluid 5 is cooled to below 60°C, for example down to about 20°-25°C, and transferred to an additional tank 14.

In figure 1 , the flow of the second fluid 5 from the thermal treatment unit 13 to the additional tank 14 is schematically represented by the arrow denoted by "A".

A pre-established quantity of already-cooled second fluid 5 is introduced into the first fluid mixture 2 so as to obtain the fluid food product 1 , which is therefore formed by the solid pieces 3 immersed in the first fluid 4 and the second fluid 5.

At least one conduit (not illustrated) is preferably included which is configured to put said additional tank 14 in selective communication with said pressure tank 1 1 .

In figure 1 , the flow of the second fluid 5 from the additional tank 14 to the pressure tank 1 1 is schematically represented by the arrow denoted by "B".

In fact, the second fluid 5 further cools the first mixture 2 such that the fluid food product 1 is at a temperature of about 60 ^C -65°C.

At this temperature it is possible to carry out the filling of a PET container 15 without damaging it. The filling is carried out by means of a first filling valve 1 6 communicating with the pressure tank 1 1 .

In figure 1 , the flow of the fluid food product 1 from the pressure tank 1 1 to the PET container 15 is schematically represented by the arrow denoted by "C".

Optionally also a pre-established quantity of the second fluid 5 will be poured into the PET container 15 so as to dilute the fluid food product 1 . The filling is carried out by means of a second filling valve 18 communicating with the additional tank 14.

The dilution is carried out after having partially filled the PET container 15 with the fluid food product 1 , coming from the pressure tank 1 1 . The PET container 15 preferably passes from a station in which it is positioned below the first filling valve 16 to a station in which it is positioned below the second filling valve 18 (represented in figure 1 by arrow "D"), or remains in the same filling station, which is configured for carrying out a dual filling, i.e. with two substances.

In figure 1 , the flow of the second fluid 5 from the additional tank 14 to the already partially-filled PET container 15 is schematically represented by the arrow denoted by Έ".

In a further embodiment, it is possible to further drop the temperature of the fluid food product 1 , i.e. bringing it down to below 60 ^C -65°C. To do this, after having cooled down to 20°-25°, the second fluid 5 is subjected to a further sub-cooling down to about 5°-10° before placing it into the first fluid mixture 2.

In fact, the first fluid 4 functions as a transport fluid for the solid pieces 3. The second fluid 5 instead represents the beverage or soup that is the basis of the final product 1 .

For example, starting from a first fluid mixture 2 constituted by solid pieces 3 and by the first fluid 4 in a weight ratio 1 :1 , by adding the pre-established quantity of second fluid 5, the product 1 is diluted to the preferred solid- liquid percentages.

The weight ratio between solid pieces 3 and first fluid 4 in the first fluid mixture 2 depends on the type of final food product 1 that is to be obtained.

In order to evaluate the integrity of the product obtained, two parameters are used. In the present description, reference is made to a final food product 1 containing peanuts as the solid pieces 3.

A first parameter - known as the hardness index - is an indication of the consistency of the peanuts. This index is obtained by measuring the force necessary for crushing a peanut. Two measurements from this index were made:

- a measurement of the peanuts contained in the canned product (prior art) and the result was 23.5 N

- a measurement of the peanuts treated by boiling (the process proposed in this document) and the result was 19 N.

Therefore, the process of the invention gives a result comparable to the desired target (produced in a can or a like retort container).

The forces were measured using a dynamometer of known type.

A second parameter - known as the damage rate - is constituted by the percentage of non-whole peanuts (i.e. those destroyed by the described process) with respect to the total. The damage coefficient is 25%.

From the description the characteristics of the process and the apparatus for packaging a fluid food product containing solid pieces according to the present invention clearly emerge, as do the results and advantages thereof.

In particular, thanks to the high-pressure boiling the sterility of the solid pieces is guaranteed without excessively compromising the integrity thereof. In fact, the solid pieces are mixed with a transport fluid (the first fluid) and are subjected to only a slight mixing, which leaves the solid consistency unaltered.

With respect to the solution disclosed in US 5,972,405, which included the dropping of the temperature to 21 °C for the whole final product, the cooling here to 20-25°C relates only to the second fluid. Therefore, the energy consumption is decidedly lower.

In fact, the cooling of the first fluid mixture is obtained by heat exchange thanks to the introduction of the beverage or soup (the second fluid) which is already at 20°-25°C or even 5°-10°C (and is therefore pre-cooled). In this way, the integrity of the solid pieces is also conserved. This integrity is not preserved in the solution of US 5,972,405, in which the whole product is cooled to 21 °C.

The proposed solution is particularly advantageous for packaging in PET containers of the fluid food products having low acidity, which cannot withstand treatment in an autoclave. The proposed solution is also advantageous in the packaging of fluid food products having high acidity, where the consumer greatly appreciates the solid pieces remaining integral.