EP4640307A1

EP4640307A1 - Method of distributing food particles in a liquid food product

Info

Publication number: EP4640307A1
Application number: EP25170493.8A
Authority: EP
Inventors: Dragana Arlov; Erik Fältman
Original assignee: Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 2024-04-25
Filing date: 2025-04-14
Publication date: 2025-10-29
Also published as: WO2025223923A1

Abstract

A method (200) of distributing food particles (112) in a liquid food product (110) held in a vessel (100). The vessel comprising an agitator arrangement (150) for circulating the particles and the liquid in the vessel, to thereby generate a circulating flow (F) in the vessel. The method comprising: receiving (S202) the liquid food and the particles in the vessel, and actuating (S204) the agitator arrangement to generate the circulating flow, thereby distributing the particles homogeneously in the liquid. The liquid food product is a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas<sup>n</sup> and a flow behavior index n in a range of 0.25-0.50. The food particles have an average particle size in a range of 5 to 20 mm. At least 90% of the food particles have a size in the range of 5 to 20 mm.

Description

Technical Field

The invention relates to the field of food production. More particularly, it is related to a method of distributing food particles in a liquid food product having a relatively speaking high viscosity.
The method comprises actuating an agitator arrangement to distribute the food particles in the liquid food product.

Background Art

Yoghurts, soups, sour milk and similar food products that contain solid ingredients are popular food products. The solid ingredients may, for example, include berries, nuts, or pieces of vegetables or fruit.
Ideally, the consumer should find an even amount of solid ingredients in every consumer package of a food product. It is thus desirable to ensure a uniform distribution of the solid ingredients throughout a product before filling the product into consumer packages.
To this end, in the production of food products with solid ingredients, a tank or buffer tank provided with some form of mixer is generally positioned just before the filling machine, which ultimately fills the food product into a consumer package. In this way it is safeguarded that the solid ingredients are mixed as evenly as possible, and that each consumer package has more or less the same amount of solid ingredients.
The mixing of the solid ingredients with the food product itself is generally made in so-called horizontal buffer tanks which are provided with a mixer. In such tanks, the mixer produces a circulating flow of the food product thereby mixing the solid ingredients therein with the food product. Further, horizontal buffer tanks are generally tubular or circular tanks arranged in a lying down fashion. The mixer is commonly arranged symmetrically with respect to a geometry of the tank so as to provide a uniform circulating low within the tank. The use of a centrally arranged mixer in combination with a horizontal tank is considered to provide the most uniform mixing and is therefore strongly recommended when setting up a production line for food products of the above kind.
To provide for an even more efficient mixing of the food products buffer tanks are commonly provided with baffles which affect the circulating flow produced by the mixer. Baffles are, as is known in the art, plates or essentially flat elements which protrude from the walls of the tank. When the circulating flow impinges on the baffles, the circulating flow locally alters its direction and flow behavior thereby enhancing the mixing of the food product with the solid ingredients.
Buffer tanks of the above type do however suffer from outspoken drawbacks. A drawback emanates from the fact that a horizontal tank occupies a significant space in relation to its volume. Thus, horizontal tanks require a large footprint which in turn means that valuable space in a production facility is occupied by the buffer tank.
Another drawback is associated with the baffles. The use of baffles results in that the buffer tanks are more complicated to fabricate and also to clean and maintain. Moreover, more material is required to manufacture the buffer tanks.
Further, when buffer tanks of the above type are used for mixing products having a relatively speaking high viscosity, the mixing of the food product and the solid ingredients tend to be unsatisfactory in the sense that the solid ingredients are not evenly distributed form consumer package to consumer package.
Even though buffer tanks currently available and the way they are used provide high reliability of mixing of food products and solid ingredients, there is still a room for improvement related to mixing of food products and solid ingredients, particularly so when the food products have a relatively speaking high viscosity.

Summary

It is an objective to at least partly overcome one or more of the above-identified limitations of the prior art.
One such objective is to provide a method of distributing food particles in a liquid food product held in a vessel, in which the food particles are homogenously distributed in the liquid food product.
Another objective is to provide such a method which is capable of handling non-Newtonian shear thinning liquid food products of a relatively speaking high viscosity.
Yet another objective is to provide such a method which is capable of handling a wide range of high viscosity liquid food products and food particles of different properties.
One or more of these objectives, as well as further objectives that may appear from the description below, are at least partly achieved by a method of distributing food particles in a liquid food product held in a vessel according to the independent claim, embodiments thereof being defined by the dependent claims.
A first aspect of the present disclosure relates to a method of distributing food particles in a liquid food product held in a vessel. The vessel comprises an agitator arrangement for circulating the food particles and the liquid food product in the vessel. The agitator arrangement is configured to generate a circulating flow in the vessel. The method comprises: receiving the liquid food product and the food particles in the vessel, and actuating the agitator arrangement to generate the circulating flow of the liquid food product and the food particles thereby distributing the food particles homogeneously in the liquid food product. The liquid food product is a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.5. The food particles have an average particle size in a range of 5 to 20 mm. At least 90% of the food particles have a size in the range of 5 to 20 mm.
By the method, food particles may be homogeneously distributed in a non-Newtonian shear thinning liquid food product of a relatively speaking high viscosity, such as in a yoghurt or an ambient soup.
The agitator arrangement is configured to generate a circulating flow in the vessel, such that the liquid food product and the food particles are circulated within the vessel. Thus, the "agitator arrangement" may be any type of arrangement which is capable of generating a circulating flow of the food particles and the liquid food product in the vessel. In this way, the food particles are distributed within the liquid food product.
The liquid food product and the food particles are received in the vessel. Thus, the liquid food product and the food particles are introduced in the vessel in any suitable way such that the food particles may be distributed in the liquid food product by actuating the agitator arrangement. In a commercial installation, the liquid food product and the food particles are typically introduced in the vessel in an automated or semi-automated manner.
By "distributing the food particles homogeneously in the liquid food product" is here meant that the food particles are distributed such that only minor variations to the amount of food particles form one liter to another liter emptied from the vessel exists. A variation of below 40 milliliters of food particles per liter of the mixture of the food particles and the liquid food product may be encompassed as being homogeneous herein.
The liquid food product is a non-Newtonian shear thinning liquid food product meaning that its apparent viscosity or effective viscosity is decreased when subjected to shear stress.
The agitator arrangement is in practice configured to subject the non-Newtonian shear thinning liquid food product to a shear stress such that the apparent viscosity of the liquid food product decreases when actuating the agitator arrangement.
The non-Newtonian shear thinning liquid food product may have a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.50 according to the power-law model.
Thus, by actuating the agitator arrangement, the apparent viscosity of the liquid food product will decrease, thereby facilitating the distribution of the food particles in the liquid food product.
In the following, various embodiments of the first aspect are defined. These embodiments provide at least some of the technical effects and advantages described in the foregoing, as well as additional technical effects and advantages as readily understood by the skilled person, for example in view of the following detailed description.
In some embodiments, the vessel may be void of baffles. By "void of baffles" is here meant that the vessel does not have any plate like structures extending more than 5 cm from an inner wall of the vessel. Thus, the vessel does not have any structure at its wall significantly affecting the circulating flow of the food particles and the liquid food product.
In some embodiments, the agitator arrangement may comprise a vertically arranged rotary shaft provided with one or more impellers configured to generate the circulating flow in the vessel in response to rotating the rotary shaft. In this way, the circulating flow may be produced in an efficient manner. Further, the liquid food product may be subjected to shear stress by the one or more impellers such that its apparent viscosity decreases.
In some embodiments, the circulating flow may have a major vertical component. Thus, the food particles and the liquid food product may be moved more along the (positive and negative) vertical direction than along any other direction such as any radial direction of the vessel. Further, the food particles and the liquid food product may be moved more along the (positive and negative) vertical direction than along a horizontal or tangential direction of a vertical wall of the vessel.
In some embodiments, the vertically arranged rotary shaft may be arranged at a radial distance from a vertical central axis of the vessel. The present inventors have surprisingly found that by arranging the vertically arranged rotary shaft at a radial distance from a vertical central axis of the vessel, the distribution of the food particles in the liquid food product may be even more homogenous. This is in contrast to the well-known motto of providing the agitator arrangement centrally located in the vessel.
In some embodiments, the vertically arranged rotary shaft may be arranged at a radial distance of 6-8 cm from the vertical central axis of the vessel.
In some embodiments, the vertically arranged rotary shaft may be arranged at a radial distance from the vertical central axis of the vessel corresponding to 10 to 40%, or 20 to 38%, of a radial distance from the vertical central axis of the vessel and an outer radial wall of the vessel.
In some embodiments, the agitator arrangement may comprise a first impeller configured to predominantly force the liquid food product and the food particles in a downward direction along the rotary shaft. In this way, the liquid food product and the food particles may be drawn mainly downwards along the rotary shaft. However, the first impeller may for natural reasons force the liquid food product and the food particles in other directions than the downward direction, although not to the same extent.
In some embodiments, the agitator arrangement may comprise a second impeller provided below the first impeller and configured to predominantly force the liquid food product and the food particles in an outward radial direction of the rotary shaft. In this way, the liquid food product and the food particles may be pushed mainly outwards from the rotary shaft. However, the second impeller may for natural reasons force the liquid food product and the food particles in other directions than the outward direction, although not to the same extent.
In some embodiments, the first impeller may have a pitch of 5 to 15 cm, preferably 8 to 10 cm. Thus, the displacement of the first impeller may be 5 to 15 cm, preferably 8 to 10 cm, during a 360 degrees rotation of the rotary shaft and hence the first impeller.
In some embodiments, a leading major surface of a blade of the first impeller may have an areas in a range of 80 to 120 cm².
In some embodiments, a blade of the second impeller may have a pitch angle of 80 to 90 degrees, preferably 85-90 degrees. Thus, a blade of the second impeller may have an angle of 80 to 90 degrees, preferably 85-90 degrees between the plane of rotation of the second impeller and a line extending through the centerline of the propeller cord.
In some embodiments, a blade of the second impeller may be formed of a flat material. Thus, a blade of the second impeller may be non-curved.
In some embodiments, a leading major surface of a blade of the second impeller may have an area in a range of 65 to 85 cm².
In some embodiments, the liquid food product may comprise one or more of yoghurt, soup, sour milk, cottage cheese, tomato paste or sauces.
In some embodiments, the liquid food product may have a flow consistency index K in a range of 9-11 Pas ⁿ and a flow behavior index n in a range of 0.35-0.45.
In some embodiments, the food product particles may comprise one or more of berries, nuts, grains, cereals, fruits, vegetables, chocolate, nougat, cookies, cakes, brownies and candy
In some embodiments, the food particles may have an average particle size in a range of 7 to 18 mm, preferably 10 to 15 mm.
In some embodiments, the food particles may have a density within a range of 800 to 1200 kg/m³, preferably 900 to 1100 kg/m³. The food particles may be floating food particles. Thus, the food particles may float in the liquid food product. The food particles may be sinking food particles. Thus, the food particles may sink in the liquid food product.
In some embodiments, the vessel may be a vertically arranged tank of a circular cross section. In this way the footprint of the vessel may be significantly reduced as compared to when using a horizontal tank or buffer tank according to industry standard. Moreover, the flow characteristics of the circulating flow is generally satisfactory in a tank of a circular cross section.
In some embodiments, the method may further comprise, repeatedly actuating the agitator arrangement for a predetermined period of time. In this way, the operating time of the agitator arrangement may be reduced. When the food particles and the liquid food product essentially have a corresponding density, the food particles will in practice remain static in the liquid food product for a certain time. Thus, during such conditions it may be possible to repeatedly actuating the agitator arrangement in time intervals and still get a homogeneous distribution of the food particles in the liquid food product.
In some embodiments, the agitator arrangement is the sole agitator arrangement provided in the vessel and is solely responsible for and capable of circulating the food particles within the liquid food product.
In some embodiments, the method comprises actuating exclusively the agitator arrangement to generate the circulating flow of the liquid food product, such that no other device or unit is operated to induce or assist in generating the circulating flow of the liquid food product in the vessel.
As used herein, the term "agitator arrangement" may refer to a single agitation device configured to circulate the food particles and the liquid food product within the vessel, wherein the device is rotatable about only one, single, rotational axis. In this case, the agitator arrangement does not include multiple rotatable components with separate axes of rotation, nor does it comprise a combination of mixers; rather, it consists of a single unit that operates around a defined, singular axis to generate the circulating flow.
Still other objectives, embodiments, and aspects, as well as additional features and advantages will appear from the following detailed description as well as from the accompanying schematic drawings.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which:

Fig. 1 is a schematical partial cross-sectional view of an example a vessel comprising an agitator arrangement.
Fig. 2 is a flow chart illustrating a method of distributing food particles in a liquid food product held in a vessel.
Fig. 3 is a graph illustrating the results of a comparative experiment in which floating particles have been distributed in a non-Newtonian shear thinning liquid test product of a relatively speaking high viscosity.
Fig. 4 is a graph illustrating the results of a comparative experiment in which sinking particles have been distributed in the non-Newtonian shear thinning liquid test product.

Detailed Description

Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments are shown. Indeed, the subject of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure may satisfy applicable legal requirements.
Where possible, any of the advantages, features, functions, devices, and/or operational aspects of any of the embodiments described and/or contemplated herein may be included in any of the other embodiments described and/or contemplated herein, and/or vice versa. In addition, where possible, any terms expressed in the singular form herein are meant to also include the plural form and/or vice versa, unless explicitly stated otherwise. Accordingly, the terms "a" and/or "an" shall mean "at least one" or "one or more", even though the phrase "one or more" or "at least one" is also used herein. The terms "multiple", "plural" and "plurality" are intended to imply provision of two or more elements. The term "and/or" includes any and all combinations of one or more of the associated listed elements. Although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing the scope of the present disclosure.
Well-known functions or constructions may not be described in detail for brevity and/or clarity. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
Like reference signs refer to like elements throughout.
Fig. 1 is a schematic overview of an example system 10 which may be used to distribute food particles 112 in a liquid food product 110 held in a vessel 100.
The system 10 is designed for and hence suitable for distributing food particles 112 in a liquid food product 110, where the liquid food product 110 is a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.50. In other words, the system 10 is designed for and hence suitable for distributing food particles 112 in a liquid food product 110 of a relatively speaking high viscosity. Further, the system 10 is designed for and hence suitable for distributing food particles 112 having an average particle size in a range of 5 to 20 mm in a non-Newtonian shear thinning liquid food product 100 having the above the above viscosity characteristics according to the power-law model. The system 10 is further designed for a situation where at least 90% of the food particles 112 have a size in the range of 5 to 20 mm.
The present inventor has after significant experimentation found that a liquid food product 110 having a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.50 results in a distribution of the food particles 112 in the liquid food product 110 which is particularly homogeneous.
The flow consistency index, denoted as K, is a parameter commonly used in the modeling of generalized Newtonian fluids, particularly within the context of the power-law model, which is a common rheological model to describe non-Newtonian behavior. The power-law model is used for characterizing fluids whose viscosity changes with the rate of shear but does not depend on the time of shearing.
In the power-law model, the viscosity µ of a fluid is given by the equation: $μ = K {\dot{γ}}^{n - 1}$ where:

K (the flow consistency index) is a coefficient that represents the viscosity level at a given shear rate and essentially adjusts the viscosity to match the flow behavior of the fluid. It has units of Pa · s ⁿ , where n is the flow behavior index.
γ̇ is the shear rate, measured in s^-1.
n is the flow behavior index, a dimensionless number that indicates the degree of shear-thinning or shear-thickening behavior of the fluid:
If n < 1, as is the case for the liquid food product, the product is shear-thinning (pseudoplastic). If n > 1, the fluid is shear-thickening (dilatant). If n = 1, the fluid behaves as a Newtonian fluid, and K becomes equivalent to the constant viscosity. For the liquid food product, the flow consistency index K and the flow behavior index n can be determined by using a conventional rheometer.

In some examples the food particles 112 may have an average particle size in a range of 7 to 18 mm. The present inventor has after significant experimentation found that food particles 112 having an average particle size in a range of 10 to 15 mm results in a distribution of the food particles 112 in the liquid food product 110 which is particularly homogeneous.
The food particles 112 may typically be berries, nuts, vegetables or pieces thereof. The food particles 112 may be blueberries typically having an average size of about 15 x 10 mm. The food particles 112 may be hazelnuts typically having an average diameter of about 11 mm. The food particles 112 may be walnuts typically having an average size of about 15 x 11 x 11 mm. The food particles 112 may be pieces of carrots typically having an average size of about 12 x 12 mm. The food particles 112 may be pieces of potatoes typically having an average size of about 11 x 11 mm. The food particles 112 may be peas typically having an average diameter of about 7 mm. Other types of food particles 112 such as grains, cereals, fruits, chocolate, nougat, cookies, cakes, brownies, and candy, are also conceivable.
Further, the food particles 112 may typically have a density within a range of 800 to 1200 kg/m³. The present inventor has after significant experimentation found that food particles 112 having a density within a range of 900 to 1100 kg/m³ results in a distribution of the food particles 112 in the liquid food product 110 which is particularly homogeneous.
The system 10 may in a commercial installation for instance form part of a production line for yoghurt or soup. Yoghurts and soups are generally non-Newtonian shear thinning liquid food products having a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.50. Other liquid food products, such as sour milk, cottage cheese, tomato paste or sauces are also conceivable.
In practice, the system 100 may be arranged directly upstream a filling machine configured to fill the liquid food product 110 and the therein distributed food particles into consumer packages. To this end, the vessel 100 is provided with an outlet 104 at its bottom. Thus, the outlet 104 may in practice be connected to a filling machine via a duct, a pipe or similar. A valve may be provided at the outlet 104.
The depicted vessel 100 of Fig. 1 is a vertically arranged tank of a circular cross section. In other words, the vessel 100 has a general cylindrical shape apart from its tapering bottom portion 101 which is provided to enable gravity assisted flowing or feeding of the liquid food product 110 and the food particles towards the outlet 104. The depicted vessel 100 is rotationally symmetric about its central axis CA.
Vessels 100 of the subject kind may come in different sizes. In a commercial installation the volume of such vessels 100 may span from about hundred liters to several thousand liters depending e.g., on the type of liquid food product 110 and the capacity of the production line at hand.
The vessel 100 may be fabricated from stainless steel or any other suitable material. The vessel 100, like the other components of the system 10, are to advantage designed to maximize food safety.
The vessel 100 comprises, as depicted in Fig. 1, an agitator arrangement 150. The agitator arrangement 150 is configured to generate a circulating flow F in the vessel 100. To this end, the agitator arrangement 150 may as shown in Fig. 1 comprise a vertically arranged rotary shaft 152. The rotary shaft 152 depicted in Fig. 1 extends into the vessel through a dedicated opening provided at the top of the vessel 100. An upper end of the rotary shaft 152 is coupled to a motor 158 which is configured to rotate the rotary shaft 152 about its longitudinal axis when actuated or operated. The motor 158 may be an electrical motor, a pneumatic motor or a hydraulic motor to give a few non-limiting examples. Thus, the agitator arrangement 150 of Fig. 1 is actuated by activating the motor 158.
The rotary shaft 152 may, as illustrated in Fig. 1, be provided with one or more impellers 154, 156 configured to generate the circulating flow F in the vessel 100 in response to rotating the rotary shaft 152. The agitator arrangement 150 of Fig. 1 comprises a total of three impellers 154, 156 of two different kinds. It is, however, conceivable to use any number of impellers 154, 156. Further, more than two types of impellers 154, 156 are conceivable.
The present inventor has surprisingly found that by arranging the vertically arranged rotary shaft 152 at a radial distance r from the vertical central axis CA of the vessel 100, an even more homogeneous distribution of the food particles 112 in the liquid food product 110 may be achieved although such an arrangement of the vertically arranged rotary shaft 152 clearly goes against the industry standard or motto of providing a centrally arranged agitator arrangement or mixer.
After significant experimentation, the present inventor has found that the distribution of the food particles 112 in the liquid food product 110 may become particularly homogeneous when the vertically arranged rotary shaft 152 is arranged at a radial distance r from the vertical central axis CA of the vessel 100 corresponding to 10 to 40 % of a radial distance R from the vertical central axis CA of the vessel 100 and an outer radial wall 102 of the vessel 100. In other words, the present inventor has found that offsetting the vertically arranged rotary shaft 152 a distance corresponding to 10 to 40 % of the radius of the vessel 100 results in a particularly advantageous situation. Other amounts of offsetting the vertically arranged rotary shaft 152 is conceivable, such as 20 to 35 %. The amount of offsetting of the vertically arranged rotary shaft 152 which gives the most homogeneous distribution of the food particles 112 in the liquid food product 110 may depend on the type of food particles 112 and on the type of liquid food product 110. Thus, the amount of offsetting of the vertically arranged rotary shaft 152 may to advantage be tailored depending on the type of food particles 112 and on the type of liquid food product 110.
After said significant experimentation, the present inventor has found that a favorable distribution of the food particles 112 in the liquid food product 110 may be achieved by arranging the vertically arranged rotary shaft 152 at a radial distance r of 6-30 cm, or 6-20 cm, from the vertical central axis CA of the vessel 100.
However, for large vessels 100, i.e., vessels 100 having a volume exceeding 5000 liters the vertically arranged rotary shaft 152 may to advantage be arranged at a radial distance r of 40 to 80 cm from the vertical central axis CA of the vessel 100.
Correspondingly, for small vessels 100, i.e., vessels 100 having a volume below 100 liters the vertically arranged rotary shaft 152 may to advantage be arranged at a radial distance r of 15 to 50 cm from the vertical central axis CA of the vessel 100. Of course, for both large and small vessel, the radial distance r should be selected so that the rotatory shaft and its impellers do not touch that tank wall.
The circulating flow F may, as illustrated in Fig. 1, have a major vertical component. The fact the circulating flow F has a major vertical component emanates from the design and configuration mainly of the impellers 154. The impellers 154 are as illustrated in Fig. 1 configured to predominantly force the liquid food product 110 and the food particles 112 in a downward direction DD along the rotary shaft 152. In this way, the circulating flow is provided with a major vertical component. The impellers 154 may have a pitch of 5 to 15 cm. It is currently believed that a pitch of 8 to 10 cm of the impellers 154 provides for an optimal distribution of the food particles 112 in a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.50, given that the food particles 112 have an average particle size in a range of 5 to 20 mm, and that at least 90% of the food particles 112 have a size in the range of 5 to 20 mm.
The impellers 154 may according to an example have a diameter of 300 mm. The impellers 154 may according to an example be arranged at a distance from each other along the vertically arranged rotary shaft 152 which corresponds to the diameter of the impellers 154. In other words, impellers 154 having a diameter of 300 mm may be spaced apart 300 mm along the vertically arranged rotary shaft 152.
The impellers 154 may according to an example have a diameter of 200 mm. The impellers 154 may according to an example be arranged at a distance from each other along the vertically arranged rotary shaft 152 which corresponds to the diameter of the impellers 154. In other words, impellers 154 having a diameter of 200 mm may be spaced apart 200 mm along the vertically arranged rotary shaft 152.
Further, it is currently believed that a favorable distribution of the food particles 112 in the liquid food product 110 may be achieved when a respective leading major surface of the blades 155 of the impellers 154 has an area in a range of 65 to 85 cm².
Other diameters, blade sizes and inter-distances of the impellers 154 are however conceivable.
The circulating flow F may, as illustrated in Fig. 1, be pushed outwards at the location of the impeller 156, which is provided below the impellers 154. The lower impeller 156 may as illustrated in Fig. 1 be configured to predominantly force the liquid food product 110 and the food particles 112 in an outward radial direction RD of the rotary shaft 152. In this way, the circulating flow is provided with a minor radial component. The blades of the impeller 156 may according to an example have a pitch angle of 80 to 90 degrees. It is currently believed that a pitch angle of the blades of 85-90 degrees of the impeller 156 provides for an optimal distribution of the food particles 112 in a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas" and a flow behavior index n in a range of 0.25-0.50, given that the food particles 112 have an average particle size in a range of 5 to 20 mm, and that at least 90% of the food particles 112 have a size in the range of 5 to 20 mm.
The blades 157 of the lower impeller 165 may to advantage be made of a flat material sheet, meaning that the pitch angle of the blades 157 may be equal over their major leading surface.
Curved or non-flat blades 157 are however conceivable, although such design is of limited relevance when the major purpose of the blades is to predominantly force the liquid food product 110 and the food particles 112 in the outward radial direction RD of the rotary shaft 152. Hence, such curved or non-flat blades 157 will not be discussed any further herein.
Further, it is currently believed that a favorable distribution of the food particles 112 in the liquid food product 110 may be achieved when a respective leading major surface of the blades 157 of the impeller 156 has size (areas) in a range of 80 to 120 cm².
By the system 10 depicted in Fig. 1 the food particles 112 may be distributed homogenously in the liquid food product 110 by actuating the agitator arrangement 150 to generate the circulating flow F of the liquid food product 110 and the food particles 112. To this end, in a commercial installation, the liquid food product 110 and the food particles 112 may to advantage be introduced in the vessel 100 in an automated or semi-automated manner whereafter the agitator arrangement 150 is actuated by operating the motor 158 such that food particles 112 are distributed homogeneously in the liquid food product 110.
Now turning to Fig. 2. A method 200 of distributing food particles 112 in a liquid food product 110 held in a vessel 100 will be described. The method 200 may be used in a system 10 to distribute food particles 112 in a liquid food product 110 held in a vessel 100 as described above in conjunction with Fig. 1. Hence, the vessel 100 comprises an agitator arrangement 150 for circulating the food particles 112 and the liquid food product 110 in the vessel 100. The agitator arrangement 150 is configured to generate a circulating flow F in the vessel 100. Thus, by the below method 200, food particles 112 may be homogeneously distributed in liquid food product 110.
The method 200 comprises receiving S202 the liquid food product 110 and the food particles 112 in the vessel 100. In a commercial installation, the liquid food product 110 and the food particles 112 are typically received in the vessel 100 in an automated or semi-automated manner. Manual reception of the liquid food product 110 and the food particles 112 in the vessel 100 is also conceivable.
The method 200 proceeds by actuating S204 the agitator arrangement 150 to generate the circulating flow F of the liquid food product 110 and the food particles 112, thereby distributing the food particles 112 homogeneously in the liquid food product 110. The liquid food product 110 is a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas" and a flow behavior index n in a range of 0.25-0.50. The food particles 112 have an average particle size in a range of 5 to 20 mm. At least 90% of the food particles 112 have a size in the range of 5 to 20 mm.
The method 200 may further comprise, repeatedly actuating S206 the agitator arrangement 150 for a predetermined period of time. Such predetermined time may in practice involve actuating the agitator arrangement 150 for a certain time at regular intervals. For instance, the agitator arrangement may be actuated for 5 minutes every 15 minutes. For instance, the agitator arrangement may be actuated for 5 minutes every 30 minutes. For instance, the agitator arrangement may be actuated for 2 minutes every 10 minutes. For instance, the agitator arrangement may be actuated for 1 minute every 5 minutes. Other time intervals and predetermined actuating times are however conceivable. Such repeatedly actuating of the agitator arrangement 150 for a predetermined period of time may to advantage be used in when the food particles 112 and the liquid food product has more or less the same density, such that the food particles 112 remain more or less static in the liquid food product 110 for a certain time. Further, such repeatedly actuating of the agitator arrangement 150 for a predetermined period of time may to advantage be used in the liquid food product has a significant viscosity (when not being agitated by the agitator arrangement 150) such that the food particles 112 remain more or less static in the liquid food product for a certain time.

Experiments

In the following selected experiments conducted by the present inventor will be described and discussed to clearly demonstrate that that the above-described method 200 may be used to distribute food particles 112 homogeneously in a liquid food product 110 using a test setup in large corresponding to the system 10 of Fig. 1. More specifically it will be clearly demonstrated that food particles 112 may be homogeneously distributed in a liquid food product 110 when the liquid food product 110 is a non-Newtonian shear thinning liquid food product 100 having a flow consistency index K in a range of 7-14Pas" and a flow behavior index n in a range of 0.25-0.50 when the food particles 112 have an average particle size in a range of 5 to 20 mm, and when at least 90% of the food particles 112 have a size in the range of 5 to 20 mm.
During the experiments, a test setup largely corresponding to the system 10 of Fig. 1 was compared to two state of the art systems. Given this, the reference numerals of Fig. 1 will be used below when appropriate to increase the legibility of the description of the experiments. During the experiments, a transparent vertical circular vessel 100 having a total volume of 200 liters was equipped with an agitator arrangement 150 having a vertically arranged rotary shaft 152 driven by an electrical motor 158. The rotary shaft was provided with a total of three impellers 154, 156 of which two impellers 154 were configured to predominantly force a test product including test particles in a downward direction DD. Each one of the two impellers 154 had a diameter of 200 mm, three blades with a pitch of 60 degrees cm and a blade area of 75 cm². The third impeller 156 was arranged at the lower end of the vertically arranged shaft 152 and was configured to predominantly force the test product and the test particles in an outward radial direction RD of the rotary shaft 152. The third impeller 156 had diameter of 200 mm, two blades of a blade pitch angle of 90 degrees and a blade area of 100 cm².
The vertically arranged rotary shaft 152 of the agitator arrangement was arranged at a radial distance r from the vertical central axis CA of the vessel 100 corresponding to 15% of the radial distance R from the vertical central axis CA of the vessel 100 and the outer radial wall 103 of the vessel 100.
The vessel 100 was void of baffles.
A non-Newtonian shear thinning liquid test product with a relatively speaking high viscosity was prepared by mixing water and 1,3 % CMC30'000. The prepared liquid test product had a flow consistency index K of 11 Pas ⁿ and a flow behavior index n of 0.4.
A first test batch was prepared by mixing the shear thinning liquid test product with test particles of a first type in the form of floating particles formed form a plastic material. The first type of test particles had a rising velocity of 0.003 cm/s, and an oval shape typically measuring 4 mm and 2,5 mm respectively along its major axes. The test particles of the first type did correspond to 10 volume % of the first test batch.
A second test batch was prepared by mixing the shear thinning liquid test product with test particles of a second type in the form of sinking particles formed form a plastic material. The second type of test particles had a sinking velocity of 0.015 cm/s, and a spherical shape typically measuring 5 mm in diameter. The test particles of the second type did correspond to 10 volume % of the second test batch.
For both test batches, the distribution capabilities of the test setup was tested and compared to the distribution capabilities of two state of the art systems. The first and the second state of the art systems did in large correspond to the test setup described above. However, the first state of the art system had its agitator arrangement arranged centrally and the vessel was provided with baffles. The second state of the art system had its agitator arrangement arranged centrally (like the first state of the art system) but was void of baffles.
During all tests, the respective test bathes were received at a vessel. Hence, the first test batch including the liquid test product and the test particles of the first type was received at a vessel for each test. Correspondingly, the second test batch including the liquid test product and the test particles of the second type was received at a vessel for each test.
For each test, the agitator arrangement of the vessel was actuated continuously while performing the respective tests. Thus, a circulating flow of respective test bathes were greeted to distribute the respective tests particles in the liquid test product. During all test, the motor of the agitator arrangement was driven at a drive frequence of 20Hz, resulting in that the outermost tip of the blades of the two uppermost impellers had a velocity of 2,1 m/s.
Now referring to Fig. 3. Fig. 3 is a graph illustrating a comparison between how well the test particles of the first type are mixed in the shear thinning liquid test product while using the test setup and the two state of the art systems. In other words, the distribution capabilities of the test setup is compared to the two state of the art systems while using the first test batch (floating test particles).
The vessel 100 was emptied and test volumes were sampled after each 10 liters emptied up until 140 liters emptied. The same procedure was repeated for the test setup and for the two state of the art systems. In Fig. 3, the deviation from a target value is plotted for the test setup as well as for the two state of the art systems. The deviation is given as a test particle volume deviation in milliliters per liter of the mixture of the test particles of the first type and the shear thinning liquid test product. Thus, the closer to 0 the more homogenous distribution of the test particles. In practice, a deviation of 0 corresponds to 10 volume % of test particles of the first type. As can be seen in Fig. 3, the test setup, denoted "Off centered agitator without" baffles clearly performs better than the two state of the art systems denoted "Centered agitator with baffles" and "Centered agitator without baffles" respectively for the floating test particles. The superior performance of the test setup for the floating particles of the first test batch is clearly shown by the measurements of the test setup being closer to the target value for almost all samples. To even more clearly show the superior performance of the test setup relative standard deviations, i.e., deviations form average, have been calculated for the test setup and for the two state of the art systems for the floating particles of the first test batch. Further, relative standard deviations have been calculated with the first and last samples removed as well as with the two first and two last samples removed. It is generally more relevant to compare the relative standard deviations with the initial and final samples removed, since such samples tend to represent a state in which the emptying of the vessel is not stable, e.g., owing from opening a valve or the test batch running low in the vessel.

For the first test batch (the floating test particles) the following relative standard deviations were obtained from the respective tests illustrated in Fig. 3.

RSD - Relative standard deviations, floating particles, first test batch
Setup/system used	All samples	First and last samples removed	2 first and last samples removed
Centered agitator with baffles	0.097	0.098	0.087
Off centered agitator without baffles	0.066	0.062	0.054
Centered agitator without baffles	0.192	0.169	0.157

From the above, it clearly follows that the test setup, denoted "Off centered agitator without" baffles clearly performs better than the two state of the art systems denoted "Centered agitator with baffles" and "Centered agitator without baffles" respectively. In all cases in the above table, the relative standard deviation is lowest for the test setup. Hence, the distribution of the first type of test particles is most homogenous in the liquid test product for the test setup.
Now referring to Fig. 4. Fig. 4 is a graph illustrating a comparison between how well the test particles of the second type are mixed in the shear thinning liquid test product while using the test setup and the two state of the art systems. In other words, the distribution capabilities of the test setup were compared to the two state of the art systems while using the second test batch (sinking test particles).
The vessel 100 was emptied and test volumes were sampled after each 10 liters emptied up until 140 liters emptied. The same procedure was repeated for the test setup as well as for the two state of the art systems. In Fig. 4, the deviation from a target value is plotted for the test setup as well as for the two state of the art systems. The deviation is given as a test particle volume deviation in milliliters per liter of the mixture of the test particles of the second type and the shear thinning liquid test product. Thus, the closer to 0 the more homogenous distribution of the test particles. In practice, a deviation of 0 corresponds to 10 volume % of test particles of the second type. As can be seen in Fig. 4, the test setup, denoted "Off centered agitator without" baffles clearly performs better than the two state of the art systems denoted "Centered agitator with baffles" and "Centered agitator without baffles" respectively for the sinking test particles. The superior performance of the test setup for the sinking test particles of the second batch is clearly shown by the measurements of the test setup being closer to the target value for almost all samples. To even more clearly show the superior performance of the test setup relative standard deviations, i.e., deviations form average, have been calculated for the test setup and for the two state of the art systems for the sinking particles of the second test batch. Further, relative standard deviations have been calculated with the first and last samples removed as well as with the two first and two last samples removed. As stated above, it is generally more relevant to compare the relative standard deviations with the initial and final samples removed, since such samples tend to represent a state in which the emptying of the vessel is not stable, e.g., owing from opening a valve or the test batch running low in the vessel.

For the second test batch (the sinking test particles) the following relative standard deviations were obtained from the respective tests illustrated in Fig. 4.

RSD - Relative standard deviations, sinking particles, second test batch
Setup/system used	All samples	First and last samples removed	2 first and last samples removed
Centered agitator with baffles	0.243	0.229	0.230
Off centered agitator without baffles	0.211	0.152	0.128
Centered agitator without baffles	0.306	0.266	0.260

From the above, it clearly follows that the test setup, denoted "Off centered agitator without" baffles clearly performs better than the two state of the art systems denoted "Centered agitator with baffles" and "Centered agitator without baffles" respectively. In all cases in the above table, the relative standard deviation is lowest for the test setup. Hence, the distribution of the second type of test particles is most homogenous in the liquid test product for the test setup.
Form the above, it has clearly been demonstrated that the test setup has a superior performance compared to the two state of the art systems for both floating and sinking test particles, when the respective test particles are mixed in a non-Newtonian shear thinning liquid test product with a flow consistency index K of 11 Pas ⁿ and a flow behavior index n of 0.4.
Form the above tests, it may be concluded that the test setup while using the above method 200 has a superior performance compared to state of the art systems when it comes to distributing food particles in a liquid food product held in a vessel, wherein the liquid food product is a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.50, wherein the food particles have an average particle size in a range of 5 to 20 mm, and wherein at least 90% of the food particles have a size in the range of 5 to 20 mm.
From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.

Claims

A method (200) of distributing food particles (112) in a liquid food product (110) held in a vessel (100), the vessel (100) comprising an agitator arrangement (150) for circulating the food particles (112) and the liquid food product (110) in the vessel (100), wherein the agitator arrangement (150) is configured to generate a circulating flow (F) in the vessel (100), the method comprising:
receiving (S202) the liquid food product (110) and the food particles (112) in the vessel (100), and

actuating (S204) the agitator arrangement (150) to generate the circulating flow (F) of the liquid food product (110) and the food particles (112), thereby distributing the food particles (112) homogeneously in the liquid food product (110), wherein the liquid food product (110) is a non-Newtonian shear thinning liquid food product having a flow consistency index K in a range of 7-14 Pas ⁿ and a flow behavior index n in a range of 0.25-0.50, wherein the food particles (112) have an average particle size in a range of 5 to 20 mm, and wherein at least 90% of the food particles (112) have a size in the range of 5 to 20 mm.
The method (200) according to claim 1, wherein the agitator arrangement (150) comprises a vertically arranged rotary shaft (152) provided with one or more impellers (154, 156) configured to generate the circulating flow (F) in the vessel (100) in response to rotating the rotary shaft (152).
The method (200) according to claim 2, wherein the vertically arranged rotary shaft (152) is arranged at a radial distance (r) from a vertical central axis (CA) of the vessel (100).
The method (200) according to claim 3, wherein the vertically arranged rotary shaft (152) is arranged a radial distance (r) of 6-20 cm from the vertical central axis (CA) of the vessel (100).
The method (200) according to claim 3, wherein the vertically arranged rotary shaft (152) is arranged at a radial distance (r) from the vertical central axis (CA) of the vessel (100) corresponding to 10 to 40 % of a radial distance (R) from the vertical central axis (CA) of the vessel (100) and an outer radial wall (103) of the vessel (100).
The method (200) according to any one of claims 2 to 5, wherein the agitator arrangement (150) comprises a first impeller (154) configured to predominantly force the liquid food product (110) and the food particles (112) in a downward direction (DD) along the rotary shaft (152).
The method (200) according to claim 6, wherein the agitator arrangement (150) comprises a second impeller (156) provided below the first impeller (154) and configured to predominantly force the liquid food product (110) and the food particles (112) in an outward radial direction (RD) of the rotary shaft (152).
The method (200) according to claim 6, wherein the first impeller (154) has a pitch of 5 to 15 cm, preferably 8 to 10 cm, and/or wherein a leading major surface of a blade (155) of the first impeller (154) has size in a range of 65 to 85 cm².
The method (200) according to claim 6 or 7, wherein a blade (157) of the second impeller (156) has a pitch angle of 80 to 90 degrees, preferably 85-90 degrees, and/or wherein a leading major surface of a blade (157) of the second impeller (156) has size in a range of 80 to 120 cm².
The method (200) according to any one of the preceding claims, wherein the liquid food product (110) comprises one or more of yoghurt, soup, sour milk, cottage cheese, tomato paste, or sauces.
The method (200) according to any one of the preceding claims, wherein the liquid food product (110) has a flow consistency index K in a range of 9-11 Pas ⁿ and a flow behavior index n in a range of 0.35-0.45.
The method (200) according to any one of the preceding claims, wherein the food particles (112) comprise one or more of berries, nuts, grains, cereals, fruits, root vegetables, chocolate, nougat, cookies, cakes, brownies, and candy.
The method (200) according to any one of the preceding claims, wherein the food particles (112) have an average particle size in a range of 7 to 18 mm, preferably 10 to 15 mm.
The method (200) according to any one of the preceding claims, wherein the food particles (112) have a density within a range of 800 to 1200 kg/m³, preferably 900 to 1100 kg/m³.
The method (200) according to any one of the preceding claims, wherein the method (200) further comprises, repeatedly actuating (S206) the agitator arrangement (150) for a predetermined period of time.