RU2841688C1 - Method of producing stable fruit filler - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: method for producing a stable fruit filler includes steps of adding active pectin methyl esterase (PME) to the fruit filler for carrying out a step for fermenting the fruit filler with subsequent inactivation of PME in fruit filler to produce stable fruit filler. Gelling is prevented or at least considerably reduced in the presence of active PME in the fruit filler by way of applying mechanical stress to the fruit filler containing active PME. Thus an improved consistency is ensured. Improvement of consistency is shown by decreasing Bostwick units, at least by 1 Bostwick unit, cm/min. Where Bostwick units are measured in accordance with ASTM F1080-93, including balancing of samples at 20 °C with additional stirring with a propeller mixer for 25 s at 25 rpm. Decrease in Bostwick units is a decrease compared to fruit filler without fermentation, as well as in comparison with the fermented food filler, which is not subjected to mechanical stress during fermentation. Mechanical stress from 1 to 100 Pa is applied to the fruit filler containing active PME by stirring, shaking, pumping or combinations thereof.

EFFECT: invention is aimed at production of a stable fruit filler.

26 cl, 3 dwg, 2 tbl, 4 ex

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

Fruit fillings are obtained from fruits with the optional addition of sugars, stabilizers, colorants and flavors.

LEVEL OF TECHNOLOGY

Fruit fillings are obtained from fruits with optional addition of sugars, stabilizers, colorants and flavors. Stabilization of fruit filling is required to ensure its homogeneity and ease of use in the final product (e.g. yoghurt).

However, there is a high demand for fruit fillings with a small list of ingredients, and therefore consumers are demanding that stabilizers not be added.

Treatment of fruit compositions with purified pectin methyl esterase (PME) enzyme, optionally with addition of calcium salt, is used in the food industry to increase viscosity and stability of fruit compositions. PME removes methyl ester groups of pectin, thus producing pectic and pectic acids, which can bind to each other via cationic cross-links to form a gel-like structure. For example, treatment with PME for 200 minutes or more caused gelation in various fruit juices. International application WO 01/58286 A1 discloses a method for preserving food products, such as fruits, berries or vegetables, comprising pre-treating the food products in a liquid medium to displace gases present in the food products, subjecting the pre-treated food products to a pressure of at least 300 MPa, and contacting the food products under reduced pressure in a liquid medium with calcium ions and PME. Thus, PME is used to harden the fruit pieces, not to increase the viscosity of the product.

The treatment of fruit puree with PME, which enables the production of fruit fillings without a stabilizer, is disclosed in European patent EP 0 624 062 B1, where pectinesterase and calcium chloride are added to a fruit or vegetable food composition to demethoxylate pectin, and where the demethoxylated pectin forms a gel. European patent EP 1 009 246 B1 (international application WO 99/011 148 A1) discloses a method for producing a fruit or vegetable product, in which PME and pectin are added to a PME-insensitive fruit or vegetable paste to increase the strength and improve the texture of fruit or vegetable products having a low dry matter content. US Patent Application US 2013/0004648 A1 discloses a method for producing a stable and homogeneous fruit filling, in which, among other things, a fruit mixture is treated at a pressure of 50 mbar to 1000 mbar. International Application WO 2005/016029 A1 discloses a method for producing a vegetable product from vegetable pieces, in particular by keeping blanched vegetable pieces in the presence of an endo-acting pectinase (not PME!) at a temperature of 60°C to 90°C to depolymerize the pectin molecule and reduce the need for mechanical treatment. Thus, the pectinase step is carried out by incubation for 2 hours at 70°C without stirring. The enzymes are then inactivated. During this enzymatic treatment, no mechanical stress is applied, for example to prevent gelation. In addition, the material subjected to enzymatic treatment is fruit pieces and not fruit puree. International application WO 2004/049824 A1 discloses a method for producing a shelf-stable fruit spread, in particular comprising the step of incubating fruit pulp with PME at 27-40°C for 2-4 hours to allow liquefaction of the pulp and thus a reduction in the viscosity of the pulp by 60-80%. For example, banana pulp was treated with a special enzyme mixture (containing polygalacturonase (PG) and PME) to ensure a reduction in the viscosity of the pulp (after adding raisins and jackfruit concentrate). Accordingly, instead of thickening, the enzyme cocktail used in this document provides a liquefying effect, after which a concentration step is required to obtain a puree with a low viscosity. During this enzymatic treatment, no mechanical stress is applied, for example to prevent gelation. The stability is related to microbiological stability rather than structural stability (uniformity of the fruit filling). International application WO 2017/035458 A1 discloses a method comprising treating cake with enzymes to improve the palatability of the cake and reduce viscosity. The enzymes or enzyme mixtures include pectinase, hemicellulose and/or cellulase; PME treatment is not disclosed, and the enzymatic treatment is used to reduce viscosity rather than to thicken the fruit puree. International application WO 2020/204924 A1 discloses a method for producing processed fruits with a step of preparing tempered fruits by tempering a fruit premix at a temperature of 110-160°F for 20-60 minutes in the presence of PME to harden the fruit pieces, rather than to increase the viscosity of the product. Such hardening of the fruit pieces requires the addition of a Ca ²⁺ salt. International application WO 96/11588 A1 discloses a method for producing a tomato-based product by subjecting tomato paste to a high-pressure shear field, followed by incubation with PME to achieve the desired consistency until the PME is inactivated. During this process, compaction of the tomato paste is achieved by incubating the PME. During this enzymatic treatment, no mechanical stress is applied, for example, to prevent gelation. Accordingly, the formation of texture is not prevented during fermentation, and the consistency and shape formation are achieved during fermentation rather than after the cooling stage (i.e. after pasteurization/enzyme deactivation). However, this method is only suitable for a limited range of fruit preparations, mainly for preparations with a high content of fruit puree (pulp), the texture of which is also provided by the large amount of water-insoluble particles present in the system.

There remains a need for a wider range of stable packaged fruit products that do not require the addition of additional stabilizers.

An additional problem is the delivery of products in large containers (shipping containers) for industrial applications (e.g. as a yoghurt additive). Without whey support, the fruit cell aggregates tend to settle slowly, creating a viscosity gradient in the container and making it difficult to dose the milk portion.

Thus, the aim of the present invention is to provide production methods applicable to a wide range of fruit preparations with a high or low puree (pulp) content or with fruit pieces or whole fruits. Another aim is to provide methods that allow stabilizing fruit pieces within the preparation. Another aim is to provide methods that allow the product to be manufactured without the need to add exogenous stabilizers, preserving the original composition of the original fruit material from which the production of the fruit product began. Preferably, the methods do not require the addition of calcium salts or acidity regulators.

ESSENCE OF THE INVENTION

Thus, the present invention relates to a method for producing a stable fruit filling, comprising the steps of adding active pectin methyl esterase (PME) to a fruit filling to carry out a fermentation step of the fruit filling, followed by inactivation of the PME in the fruit filling to produce a stable fruit filling, wherein gelation is prevented or at least significantly reduced in the presence of active PME in the fruit filling by applying mechanical stress to the fruit filling containing active PME.

Thus, the present invention relates to a method for producing a stable fruit filling comprising a fermentation step (i.e., treatment with PME for a limited period of time), wherein gelation (i.e., formation of jelly) during the fermentation step is prevented or significantly reduced.

A particularly preferred method comprises the following steps:

1. A stage of heating the fruit, during which the fruit's own pectin enzymes are deactivated and some of the pectin bound to the cell walls is dissolved. A stage of crushing the fruit is not necessarily included if whole fruit is used as the source of the puree.

2. PME treatment ("fermentation stage"), which is carried out to reduce the esterification of pectin and to increase its gelling ability. Since the PME treatment is carried out at relatively low temperatures at which pectins can be converted into gel, the crosslinking of the pectin chains, leading to the formation of a gel that is irreversible under shear and heat treatment, is prevented by applying mechanical stress to the fruit filling of the present invention. In addition, in order to reduce gelation, the addition of Ca salts before or during the fermentation stage should be avoided. Accordingly, the fermentation stage of the present invention is carried out by thickening the fruit filling, in particular the puree (for example, by achieving a decrease in Bostwick units by at least 1 Bostwick unit [cm/min]). Therefore, it is necessary to use PME in this fermentation stage without any viscosity-lowering additives, such as viscosity-lowering enzymes such as PG.

3. Heating to pasteurization temperature, pasteurization and cooling. Mechanical shear to prevent gelation may be maintained until the filling has reached 70°C; above this temperature, the shear rate is adjusted in accordance with standard manufacturing practice.

The gelatinous structure is formed during the cooling of the fruit filling (not already during the fermentation process) and partly after the filling of the container (shipping container) with the filling. This process allows for the production of stable fruit fillings that do not require the addition of exogenous stabilizers. In addition, preventing gelation during fermentation also allows for the proper handling of the fillings in subsequent production stages, which is particularly advantageous for industrial processes carried out at the serial production level. The addition of Ca salts is also not required, which allows for a product with a clean label. This process also allows the use of frozen fruit puree as a starting material. Frozen fruit retains more pectin, and such purees also improve the color and taste. This also implies that the method of the present invention demonstrates the best efficiency in obtaining fruit fillings that are not fillings from nightshade fruits, in particular are not fruit fillings from potato, tomato or eggplant, i.e. fruit fillings from strawberry, peach, apricot, fig, pear, cherry, sweet cherry, apple, blueberry, mango, banana or mixtures thereof.

Gelling is prevented during the fermentation stage by applying mechanical stress. This is preferable to other anti-gelling means because it can be easily and smoothly integrated into the fruit filling production process and does not require the addition and removal of anti-gelling chemicals or the use of complex devices or equipment during the production process.

The corresponding (significant) reduction or prevention of gelation in the method according to the invention is achieved by the present invention, for example, by applying a mechanical stress of 1 to 100 Pa, preferably 3 to 20 Pa, to the fruit filling containing the active PME. Preferably, such mechanical stress is applied in the method according to the invention by stirring, shaking, pumping or combinations thereof, in particular by stirring. In fact, as also shown in the examples section below, there is a large difference in the reversibility and the elastic modulus values when the shear stress is increased from 0.5 to 3 Pa. As has also been confirmed experimentally, when the shear stress is further increased to 20 Pa, the increase in the elastic modulus is smaller. Accordingly, applying a shear stress of 0.5 Pa is a suitable lower limit for obtaining the advantageous effects according to the present invention. In preferred methods according to the present invention, a shear stress of at least 1 Pa, in particular at least 3 Pa, is applied.

The combination of an appropriate mechanical shear during the fermentation according to the present invention (which exceeds the yield point of the formulation mixture and can be determined for each formulation, as shown for example in Example 4) and heat treatment of the fruit before the fermentation step reduces the flow rate on the Bostwick consistometer by at least 1 cm/min, preferably by at least 2 cm/min, in particular by at least 3 cm/min, and/or makes it possible to obtain stable fruit fillings with a flow rate of ˂10 cm/min and having a gel-like structure (elastic modulus (Gʽ) ˃ loss modulus (Gʽʽ) at low shear.

A suitable method for determining mechanical stress described and used in the present invention is disclosed by Läuger et al. in their paper, “Discrepancies in the Specified Data and Presentation of a New Data Set for ^NIST® Standard Reference Material SRM 2490” (available at https://www.researchgate.net/profile/Joerg_Laeuger/publication/269407610_Discrepancies_in_the_Specified_Data_and_Presentation_of_a_New_Data_Set_for_NIST_Standard_Reference_MaterialR_SRM_2490/links/548af3d20cf2d1800d7dace8/Discrepancies-in-the-Specified-Data-and-Presentation-of-a-New-Data-Set-for-NIST-Standard-Reference-MaterialR-SRM-2490.pdf) and can be performed using the described It contains a rheometer (Physica MCR 501 rheometer from Anton Paar (AT)) with temperature control by Peltier elements by recording the shear force by means of torque at each measurement point (shear stress covers all types of mechanical stress).

The present invention provides for the application of mechanical stress to prevent the formation of gels during the fermentation process. Jelly formed during fermentation (in the absence of stirring) is characterized by a small tan δ (˂0.2) and is shear-irreversible. However, if mechanical shear is applied during the fermentation stage, the formation of a strong gel is prevented and the shear-irreversibility of the gel is improved.

The IUPAC definition states that a gel is a non-liquid colloidal network or polymer network that is expanded throughout its volume by a liquid. A gel comprises a solid internal three-dimensional network structure that encloses a volume of liquid medium and holds it in place by surface tension effects. Both by weight and by volume, gels are essentially liquid in composition and thus have a density similar to that of their constituent liquids. Due to the aqueous nature of the gels produced by the processes of the art (as associations of pectic and pectic acids through cationic cross-links, hydrogen bonds or hydrophobic interactions), the gels referred to herein are hydrogels and have - with the exception of fruit pieces - approximately the density of water. The three-dimensional solid is the result of hydrophilic polymer chains held together by cross-links. Due to the inherent cross-links, the structural integrity of the hydrogel network does not dissolve at high water concentrations. Hydrogels are highly absorbent (they can contain more than 90% water) natural or synthetic polymer networks. Hydrogels also have a degree of flexibility very similar to natural tissue due to their significant water content. A "significant" or "substantial" reduction in the present invention is defined as a reduction compared to the same filling without the application of mechanical stress during the fermentation step. The reduction can be determined by comparing the Bostwick units of the final products from mechanically untreated fruit fillings with the final products obtained using the present invention.

Bostwick units are used to determine the consistency of materials. The consistency of various liquid and semi-liquid processed fruits and vegetables and similar products can be determined (in Bostwick units [cm/min]) by measuring these fillers in a consistometer for their flowability. Bostwick units can be measured according to the disclosure of U.S. Patent Application US 2295710 A, Steele et al. (Dysphagia 29 (2014), 355-364), Perona (Appl. Rheol. 15 (2005), 218-229), McCarthy et al. (J. Food Sci. 72 (2009), E291-E297), Balestra et al. (Proc. Food Science 1 (2011), 576–582, specifically for physicochemical and rheological measurements of fruit purees) or ASTM F1080-93 (2019; Standard Test Method for Consistency of Viscous Liquids Using a Consistometer). The Bostwick consistometer is a simple benchtop device in which a fixed volume of liquid is released from a flow chamber into an adjacent channel marked to measure the leading edge of the liquid when it comes to a standstill. The Bostwick unit is expressed as the distance traveled (cm) over an interval of 30 or 60 seconds. The correlation of Bostwick units and other rheological units is known in the art and is illustrated, for example, in Steele et al. (2014), McCarthy et al., Balestra et al., and Perona (2005).

Accordingly, the mechanical stress applied according to the present invention should preferably lead to an improvement in consistency, which is defined by a reduction in Bostwick units of at least 1, preferably at least 2, in particular at least 3 Bostwick units (in [cm/min]). Alternatively, a significant reduction in gelation is also achieved if a reduction of at least 20%, preferably at least 25%, in particular at least 30% of the Bostwick units is achieved. In preferred embodiments of the present invention, a reduction of at least 5, preferably at least 6, in particular at least 7 Bostwick units or, alternatively, in relative terms, of 40% or more, preferably of 50% or more, in particular of 60% or more, can be obtained by the present invention, especially in combination with other process steps such as preheating (see examples). In particularly preferred embodiments, the consistency of the fruit fillings is improved by at least 10, preferably at least 13, in particular at least 15 Bostwick units compared to a fruit filling without a fermentation step. Bostwick units are measured in cm/min, preferably by the method described in ASTM F1080-93 and as measured in the examples. In case of doubt, the Bostwick units described herein are measured by this standard method (including equilibration of the samples at room temperature (20°C) and using additional mixing with a propeller stirrer for 25 seconds at 25 rpm, as shown in the examples).

Accordingly, the present invention is based on the unexpected effect that applying mechanical stress to the fruit filling during the fermentation step (e.g. by stirring) leads to an unexpected improvement in viscosity (or a decrease in flowability) compared to a fruit filling without fermentation, as well as compared to a fermented fruit filling that is not subjected to mechanical stress during fermentation. During the development of the present invention, it was found that if irreversible gelling is formed at an early stage of the process (e.g. during fermentation), this leads to a deterioration in the product characteristics (e.g. jelly formed as a result of a process in which mechanical stress is not applied during fermentation no longer recovers after subsequent destruction (e.g. under the action of heat or shear stress)). If this gelling is prevented or at least significantly reduced during the fermentation according to the present invention, more gelling occurs in subsequent stages before the final product is obtained, and therefore the products obtained by the present method have improved product characteristics (e.g. the product is thicker and more stable). In fact, when a jelly is formed after the fermentation process carried out according to the present invention, for example during the cooling process, especially with constant stirring, this jelly formation may even be reversible. Accordingly, when using the present invention in the fermentation process, less jelly formation is achieved during the fermentation stage. However, subsequently (for example after cooking and cooling, etc.) more jelly is formed. Without applying mechanical stress during fermentation, more jelly formation is achieved at this fermentation stage, but this jelly is subsequently irreversibly destroyed, for example, as soon as a heating stage is applied (in fact, it has also been surprisingly found that upon cooling this jelly cannot be restored, so that a more liquid product is obtained as the final product). In carrying out the present invention, it was also noted that - for the present method and the products obtained by it - gelation is associated with higher viscosity and lower Bostwick values (although, in principle, gelation is the formation of a three-dimensional network, while viscosity is the resistance to flow, in the present invention a product is obtained for which the Bostwick consistometer analysis (depending on the yield point and viscosity) turned out to be a suitable indicator of apparent viscosity).

DETAILED DESCRIPTION OF THE INVENTION

The method according to the present invention is a significant further improvement of the method for producing fruit compositions using PME, which makes it possible to improve the stabilization of fruit fillings, especially when they also contain pieces of fruit in the filling composition.

In the course of the present invention, it was found that a combination of two stages is required to obtain a stable fruit filling: heat treatment of the fruit puree prior to fermentation and application of mechanical stress during fermentation. This method according to the present invention allows obtaining fruit/vegetable fillings, jams, sauces that do not require the addition of an exogenous stabilizer (such as pectin, citrus fiber, starch, LBG, guar gum, xanthan gum, carrageenan). The products obtained by the method according to the present invention also do not require the addition of calcium salts or acidity regulators and can contain fruit puree in an amount of up to 10%. Thus, the present invention allows to maximize the amount of fruit pieces in the fruit filling and at the same time maintain a minimum amount of puree. According to preferred embodiments of the present invention, the present method, in particular, allows to obtain fillings prepared only from fruits (including whole fruits, fruit pieces, fruit purees and fruit juice concentrate). Preferably, mechanical stress is applied to the fruit filling containing the active PME by means of stirring, shaking, pumping or a combination thereof, in particular stirring. These methods have proven to be particularly easy to integrate into fruit processing processes, including on a large scale, and are therefore particularly suitable for use in the food industry.

The fermentation step of the fruit filling using PME can be carried out in a manner already known in the art, except for the application of sufficient mechanical stress during this fermentation process.

According to a preferred embodiment of the present invention, the fruit or puree or fruits used for the fruit filling are subjected to heat treatment prior to the fermentation step. Heat treatment of the puree prior to fermentation is advantageous since it serves to inactivate naturally present enzymes, in particular polygalacturonase (PG). Heat treatment is particularly advantageous for purees prepared from frozen fruits since the enzymatic activity in such purees after thawing is high since the cells are damaged and the enzyme is released. The inactivation of natural PG and PME in fruits has been studied for many fruits (T. Duvetter, D.N. Sila, S. Van Buggenhout, R. Jolie, A. Van Loey, and M. Hendrickx. Pectins in Processed Fruit and Vegetables: Part I-Stability and Catalytic Activity of Pectinases. Vol. 8, 2009-Comprehensive Reviews in Food Science and Food Safety). Preferably, this heat treatment before fermentation is carried out at a temperature of from 60°C to 110°C, preferably from 75°C to 95°C, and/or for from 30 seconds to 30 minutes, preferably for 5-10 minutes.

According to a preferred embodiment, the method of the present invention eliminates the addition of an active viscosity-reducing enzyme, in particular the addition of a PG enzyme, to the process.

Preferably, the fermentation step is carried out for 1 to 120 minutes, preferably 2 to 60 minutes, in particular 5 to 30 minutes; and/or at a temperature of 20°C to 60°C, preferably 30°C to 50°C, in particular 35°C to 40°C, and/or with stirring at 10 to 500 rpm, preferably 20 to 100 rpm, in particular 30 to 50 rpm.

Preferably, the present method further comprises a step of heating the fruit before adding the PME to the fruit filling and a step of heating after the enzymatic treatment using the PME, in particular the pasteurisation step, wherein preferably the mechanical stress is also applied during the heating step, in particular at a temperature below 70°C. The step of heating the fruit is preferably carried out before adding the PME to the fruit filling and is preferably carried out for 1 to 120 minutes, preferably 2 to 60 minutes, in particular 5 to 30 minutes.

According to a preferred embodiment of the present invention, the fermentation step is followed by pasteurization of the fruit filling, in which the enzyme is deactivated, and cooling of the preparation containing the deactivated enzyme. The pasteurization step is preferably carried out at a temperature of at least 60°C, preferably at least 70°C, in particular at least 80°C; and/or with a duration of at least 1 min, preferably at least 3 min, in particular at least 5 min. During the cooling step, jelly formation may be allowed. If no mechanical stress is applied during the fermentation process, the jelly obtained by such methods includes clots of harder jelly in the matrix.

The fruits processed according to the present invention can be any fruits. A preferred fruit raw material is a material that is currently subjected to a fermentation step (using PME) in modern food processing plants. Accordingly, the fruits to be processed according to the present invention are preferably fruit preparations sensitive to PME. Preferred fruit preparations according to the present invention are preparations selected from strawberry ( Fragaria ananassa ), peach ( Prunus persica ), apricot ( Prunus armeniaca ), fig ( Ficus carica ), pear ( Pyrus ), cherry ( Prunus cerasus ), sweet cherry ( Prunus avium ), apple ( Pyrus malus, Malus pumila ), blueberry ( Vaccinium cyanococcus ), mango ( Mangifera indica ), banana ( Musa acuminata ); or mixtures thereof.

The present invention is applicable to a very diverse range of fruit fillings, which means that there is no need for a high or low puree content or a limitation on the inclusion of fruit pieces. In fact, the present invention allows for stable fruit fillings to be obtained, which contain fruit pieces and also hold them three-dimensionally in a stable shape (i.e., the fruit pieces do not sink to the bottom during storage). Accordingly, the fruit filling of the present invention may also preferably contain fruit pieces or whole fruits.

It is this three-dimensional stability, maintained during storage, that allows additional components to be included in the fruit product of the present invention both in a divided (e.g. layered) structure and in an already mixed structure. Therefore, in a preferred embodiment of the present invention, the fruit filling contains additional nutritional components, preferably cereals, seeds, nuts or mixtures thereof.

By using the present invention, it is possible to eliminate the addition of exogenous components such as stabilizers. By using the present method, it is also possible to eliminate the addition of calcium salts during the production process. Thus, a preferred embodiment of the method according to the present invention is a method in which Ca salts are not added during production, in particular in which Ca salts are not added before the inactivation of the PME.

According to a preferred embodiment of the present invention, it is possible to obtain a food product which (in addition to the inactivated PME) contains only material derived from fruit raw material. Thus, this preferred embodiment provides a stable fruit filling consisting only of fruit in the form of fruit puree, fruit juice, fruit pieces or mixtures thereof and inactivated PME.

Preferably, the fruit filling is a fruit puree, i.e. a fermentable but unfermented product obtained by any suitable physical process such as sifting, crushing, grinding the edible portion of whole or peeled fruit without removing the juice.

Unlike many fermentation methods using PME disclosed in the prior art, the present invention does not require the use of high pressure. Accordingly, the method of the present invention can be carried out under normal pressure conditions. Thus, the method of the present invention, at least the fermentation step, is preferably carried out without applying a high pressure of 300 MPa or more, even more preferably without applying a pressure of 180 MPa or more, in particular when the fermentation step is carried out under atmospheric pressure conditions.

On the other hand, the present method, of course, also allows for the addition of additional components that are added in known methods for producing fruit products. For example, the present method can also be carried out in an embodiment in which Ca ²⁺ ions are present during production.

According to a preferred embodiment, the fruit filling according to the present invention has a pH value of from 3.0 to 7.0, preferably from 3.2 to 5.5, in particular from 3.5 to 4.2.

The present invention is suitable for large-scale food industry. Accordingly, in a preferred method of the present invention, the stable fruit filling obtained by the present method is packaged in a form that is stable during storage.

The present invention is further illustrated by the following examples and figures, but is not limited thereto.

Fig. 1 shows an example of a rheological curve during a 4-stage test (X-axis: time [s], Y-axis: storage modulus Gʽ [Pa], loss modulus Gʽʽ [Pa]);

Figure 2 shows the gel formation during fermentation and the reversibility of strawberry jellies at two different shear rates (X-axis: time [s], Y-axis: storage modulus Gʽ [Pa], loss modulus Gʽʽ [Pa]); 0.1% shear strain corresponds to a shear stress of 0.5 Pa, 0.5% shear strain corresponds to a shear stress of 1 Pa;

Figure 3 shows the effect of shear during fermentation on the resulting values of storage and loss moduli after high shear application, i.e. the effect of different shear stress [Pa] during the fermentation step (X-axis) on the Gʽ and Gʽʽ [Pa] values after high shear treatment (Y-axis).

EXAMPLES

EXAMPLE 1. FRUIT FILLING OF STRAWBERRY, BANANA AND PEACH

Standard recipe

Fruit puree - 50%

Sugar - 50%

(mushroom PME - 0.05%)

Typical recipes (1 kg sample) containing only fruit puree and sugar were prepared with or without a preheating step and with or without stirring during the fermentation step. The preparation was carried out in the laboratory on a Miniterm Ecotherm F water bath (Dinkelberg Analytics). The samples were stirred at 40 rpm.

Strawberry and peach puree were prepared from individually quick-frozen fruits (not previously subjected to heat treatment), and then part of the puree was additionally heated at 90°C for 10 minutes. For banana puree, an aseptic method was used, with some effect of heat treatment being noticeable.

Fermentation was carried out at 40°C for 10 minutes.

Strawberry Banana Peach Control (no fermentation) 24 13 18 No stirring, no preheating 18 8 14 Stirring, without preheating 12 6 8 Without stirring, preheating 9* 7 9 Stirring, preheating 7.5 5 5

In another technology, fruit fillings made of apricot, pear and apple contain 50% fruit puree and 50% sugar. Here, the effects of mixing and pasteurization of the puree were not studied separately. The results of consistency measurements (Bostwick flow) for fruit fillings according to the present invention ("Fermentation") compared to fruit fillings without a fermentation step ("No Fermentation") are as follows:

No fermentation Fermentation Apricot 10 5.5 Pear 18 5.2 Apple 15 3.5

The Bostwick flow rate is measured over 60 seconds.

The figures given in the tables are the consistency values measured in Bostwick units ([cm/min]) as determined in the final product. Briefly, this consistency was determined using a Bostwick consistometer (CSC Scientific Co., Fisher Scientific, Nepean, ON, Canada) for evaluating the resistance to flow of fruit preparations according to the ASTM standard method (ASTM, 2019; Standard F1080-93). Before measuring the sample in the Bostwick consistometer, the samples were equilibrated at room temperature (20°C) and additionally stirred (Heidolph propeller stirrer, RZR 2102, 25 s at 25 rpm). The flow along the inclined plane is caused by the effect of gravity on the product. The flow distance depends on the viscosity as well as the elastic properties and adhesion of the product to the consistometer surface. The spring-loaded valve was first closed to allow the reservoir to be filled to the upper limit (75 ml), and then the valve was opened, instantly releasing the fruit filling. The distance (in cm) that the fruit fillings traveled in 60 s was recorded. Three replicates were performed for each of the fruit fillings analyzed. The shorter the flow distance, the better the consistency of the fruit filling.

With each fruit, you can see the positive effects of both mixing and pre-processing the puree.

EXAMPLE 2. MANGO FILLING MADE FROM FRUIT COMPONENTS ONLY.

Preparation of 1 kg of sample was carried out in the laboratory on a Miniterm water bath.

Mango puree (pasteurized) - 20%

Mango cubes 9x9-55%

Grape juice concentrate - 24%

Pectin methylesterase - 0.1%

Water - 0.9%

Mix all components except PME and heat to 40°C.

Add PME, then stir the mixture for 10 minutes (in the laboratory at 40 rpm), then immediately heat to 85°C.

Pasteurize the mixture for 10 minutes at 85°C and cool while stirring to 30°C.

Pour the filler into the container; store the container in a cool place 8-15°C.

The filler thus obtained has a Bostwick flowability of 6.5 at 20°C and is stable for at least an observation period of 56 days.

EXAMPLE 3. STRAWBERRY FILLING WITH SUGAR

Strawberry - 50%

Sugar - 25%

Strawberry puree - 25%

Pectin methylesterase (Aspergillus niger) - 0.05%

Slowly add 200 kg of whole frozen strawberries to a cooking kettle containing 10-15 litres of water.

Heat the fruit to 65°C, then prepare the puree.

Heat the resulting puree to 90°C for 5 minutes.

Add 200 kg of sugar

When the sugar is completely dissolved, add 400 kg of 10x10 strawberry cubes.

Heat the mixture to 40°C and add the PME enzyme solution.

Stir the mixture for 10 minutes at 16 rpm, then immediately heat to 85°C.

Pasteurize the mixture for 10 minutes at 85°C and cool while stirring to 30°C.

Pour the filler into a container with a capacity of 800 l; store the container in a cool room at 8-15°C.

The average shear rates during the mixing stage of the production process were about 10-20 s ^-1 (CFD computer modeling). The viscosity of the fruit mixture during the fermentation stage was in the range of 1000-2000 mPa×s, which gives shear stress values from 10 to 40 Pa.

The resulting strawberry fruit filler was stable for 42 days. This example demonstrates that scaling up the method of the present invention from laboratory to industrial scale was successful.

EXAMPLE 4. SHEAR STRESS OF A MODEL SYSTEM

During laboratory and industrial line testing, it was noted that low or no shear during fermentation resulted in a decrease in final viscosity. In the following experiments, shear stress was quantified in a series of rheometer tests.

Rheological testing method :

Fermentation was carried out at 20°C (also for handling reasons). The enzyme concentration was adjusted accordingly (increased from 0.1% to 0.2%). Model systems were chosen in such a way that after 10-12 minutes of fermentation a strong unstable jelly is formed, but at first the mixture is relatively liquid.

Recipe for making strawberries :

Strawberry puree from individually frozen fruits (70%) was mixed with sugar (30%) and pasteurized (to inactivate strawberry enzymes) and then cooled to ambient temperature. The filling was sieved through a fine sieve (0.5 mm) to remove any particles that could affect the measurement results.

The amplitude sweep was measured in the model system before adding the enzyme and also 10 minutes after adding the enzyme (since measuring the full amplitude sweep takes time, the first point was recorded 10 minutes after the start of fermentation and the last point was recorded approximately 15 minutes later). By measuring the amplitude sweep, the linear viscoelastic range of the product was found. A point (shear force 0.5%) was selected for the kinetic tests, which was within the linear viscoelastic range. The kinetic tests were carried out according to the following procedure: add the enzyme and start the timer. After stirring for 15 seconds, the sample was placed in a rheometer (PP50 measuring system) and equilibrated. The curve recording began exactly 2 minutes after adding the enzyme.

The kinetic stage without high shear included 1-2 stages.

A controlled pre-shear was applied at a fixed shear strain (Gʽ and Gʽʽ were measured with a modular compact rheometer MCR 302 at such a shear, the shear stress was also recorded by the rheometer).

A 0.5% shear strain was applied for 5 min (Gʽ, Gʽʽ and shear stress were recorded).

The kinetic shear test included 3 of 4 stages. Stage 2 was omitted when the non-high shear curve was recorded.

A controlled pre-shear was applied at a fixed shear strain (Gʽ and Gʽʽ and the shear stress were also recorded by a rheometer).

A 0.5% shear was applied for 1 min (Gʽ, Gʽʽ and shear stress were recorded).

High shear was applied for 20 seconds.

The recovery of Gʽ and Gʽʽ (recorded at 0.5% shear strain) was monitored.

An example of a rheological curve during a stage 4 test is shown in Fig. 1.

Changing the time in stage 3 from 20 seconds to 1 minute did not change the results, so the time was kept at 20 seconds. Shear reversibility can be defined as the % G’ or complex modulus G* loss after applying shear. However, during the present test, the enzyme remains active and continues to work. Therefore, to more accurately measure the shear reversibility of the product, the results of the stage 2 kinetic test (without high shear) were compared with the stage 3 test (with high shear applied), or a stage 4 test was used where the curve fit from stage 2 was compared with the recovery curve (stage 4).

The magnitude of the shear was varied by varying the shear strains applied in stage 1. However, it is also important how many measurement points were taken. If only one measurement was taken for 10 seconds, the shear was lower. If every second was measured, the shear was higher. The shear stress was recorded automatically (it is directly proportional to the torque). As the product hardened, the shear stress also increased. Therefore, average shear stress values were used in stage 1. To study the effect of fermentation time, only stage 1 was added, and the other stages were left unchanged.

Results :

It was noted that initially much more gelation was formed in the absence of shear. But then this gelation became irreversible as soon as we applied high shear (see Fig. 2). We studied the gelation at different shear stresses. In the strawberry formulation, a large difference in reversibility and elastic modulus values was observed as the shear stress increased from 0.5 to 3 Pa, but as the shear stress was further increased to 20 Pa, the increase in elastic modulus was smaller (Fig. 3). Accordingly, in this model system, applying a shear stress of 0.5 Pa is a suitable lower limit to obtain the preferred effects of the present invention, however, the shear level data cannot be generalized since the fruit systems we studied have very different viscosity and yield stress values.

Further increases in shear stress (e.g. above 100 Pa) may lead to degradation of other stabilizers naturally present in fruit purees, especially native starches. High shear may also lead to a reduction in particle size and loss of viscosity. Therefore, applying high shear does not provide any additional benefits.

It is obvious that more intense stirring increases the rate of the enzymatic reaction, so the observed effect may also be related to a higher fermentation rate. However, before the application of high shear, the products that were intensively stirred did not have a higher viscosity than the products that were not stirred (weakly stirred). Also, to prove that the positive effect of the present invention is the result of a change in texture due to mechanical stress, and not a higher degree of fermentation, additional tests were carried out with a higher enzyme concentration and a longer fermentation time. In these tests, it was noted that increasing the enzyme concentration or the fermentation time did not improve the shear reversibility of the products that were not stirred.

Methods used

Measurement of mechanical stress [Pa]

The mechanical stress is measured in Pa by the method disclosed by Läuger et al. in their paper "Discrepancies in Reported Data and Submission of a New Data Set for ^NIST® Standard Reference Material 2490" and performed using the rheometer described there (Anton Paar (AT) Physica MCR 501 rheometer) with Peltier temperature control.

Brix and pH Measurement

Brix and pH measurements are carried out using an RX-5000 refractometer from Atago LTD (Japan) and an InoLab 730 WTW GmbH (Weilheim, Germany) pH meter, respectively.

Viscosity measurement

The viscosity of the puree was measured using a Brookfield viscometer (spindle 3, 10 rpm). The final fillers were fed to a Brookfield viscometer and a Bostwick consistometer. In all cases, the samples were equilibrated at room temperature. Before measuring the sample on the Bostwick consistometer, the samples were additionally shaken (Heidolph, RZR 2102 propeller stirrer, 25 sec at 25 rpm) to ensure homogeneity.

Additional viscoelastic tests were performed on a modular compact rheometer MCR 302 (Anton Paar GmbH, Graz, Austria), the temperature of which was controlled by a Haake K20 and DC5 (Haake, Karlsruhe, Germany). A plate-on-plate measuring system (PP50) was used. The results were collected using the RheoCompass software. The temperature was always set to 20°C, and the measurement was started after 2 minutes of maintaining a constant temperature. The tests were always performed in replicates.

To determine the viscoelastic properties of the substance, the gamma amplitude was logarithmically increased from 0.01 to 1000%. To interpret the viscoelastic properties, the ratio between Gʽ/Gʽʽ at an angular frequency of 10 1/s is used to describe the strength of the strawberry filling.

Shelf stability

The products were stored in transparent containers (500 ml) for 2 months at a temperature of +10°C. Floating of pieces and syneresis were noted, but the exact amount of liquid separated from the jelly was not measured. Bostwick flowability at the end of the shelf life was measured again and compared with the value after 1 day. The permissible difference to confirm the presence of stability during storage was ˂2 Bostwick units.

The present invention is further defined by the following embodiments:

1. A method for producing a stable fruit filling, comprising the steps of adding active pectin methyl esterase (PME) to a fruit filling, followed by inactivating the PME in the fruit filling to produce a stable fruit filling, wherein gelation is prevented or at least significantly reduced in the presence of active PME in the fruit filling due to mechanical action on the fruit filling containing active PME.

2. The method according to embodiment 1, wherein the fruit filling is a puree.

3. The method according to embodiment 1 or 2, wherein the puree or fruits used for the fruit filling are heat treated prior to the fermentation step.

4. The method according to embodiment 3, wherein the heat treatment is carried out at a temperature of from 60°C to 110°C, preferably from 75°C to 95°C.

5. The method according to embodiment 3 or 4, wherein the heat treatment is carried out for 30 seconds to 30 minutes, preferably for 5-10 minutes.

6. The method according to one of embodiments 1-5, wherein a mechanical stress of 1 to 100 Pa, preferably 3 to 20 Pa, is applied to the fruit filling containing the active PME, preferably by stirring, shaking, pumping or a combination thereof.

7. The method according to one of embodiments 1-6, wherein the fruit fillings are fillings selected from strawberry ( Fragaria ananassa ), peach ( Prunus persica ), apricot ( Prunus armeniaca ), fig ( Ficus carica ), pear ( Pyrus ), cherry ( Prunus cerasus ), sweet cherry ( Prunus avium ), apple ( Pyrus malus, Malus pumila ), blueberry ( Vaccinium cyanococcus ), mango ( Mangifera indica ), banana ( Musa acuminata ); or mixtures thereof.

8. The method according to one of embodiments 1-7, wherein the fruit filling comprises pieces of fruit or whole fruit.

9. The method according to one of embodiments 1-8, wherein the fruit filling contains additional nutritional components, preferably cereals, seeds, nuts or mixtures thereof.

10. The method according to one of embodiments 1-8, wherein the stable fruit filling consists of fruits in the form of fruit puree, fruit juice, fruit pieces or mixtures thereof and inactivated PME.

11. The method according to any one of embodiments 1-10, wherein the Ca ²⁺ ions are present during production, in particular wherein the Ca ²⁺ ions are present prior to inactivation of the PME.

12. The method according to one of embodiments 1-10, wherein Ca ²⁺ ions are not added during production, in particular Ca ²⁺ ions are not present prior to inactivation of the PME.

13. The method according to one of embodiments 1-12, wherein the filler has a pH from 3.0 to 7.0, preferably from 3.2 to 5.5, in particular from 3.5 to 4.2.

14. The method according to one of embodiments 1-13, wherein the stable fruit filling is packaged in a form that is stable for storage.

15. The method according to one of embodiments 1-14, wherein the method further comprises a step of heating the fruit before adding the PME to the fruit filling and a step of heating after the enzymatic treatment of the PME, in particular a pasteurization step, wherein preferably mechanical stress is also applied during the heating step, in particular at temperatures below 70°C.

16. The method according to one of embodiments 1-15, wherein the fermentation step is carried out for 1 to 120 minutes, preferably 2 to 60 minutes, in particular 5 to 30 minutes.

17. The method according to one of embodiments 1-16, wherein the fermentation step is carried out at a temperature of from 20°C to 60°C, preferably from 30°C to 50°C, in particular from 35°C to 40°C.

18. The method according to one of embodiments 1-17, wherein the fermentation step is carried out with stirring at a speed of 10 to 500 rpm, preferably 20 to 100 rpm, in particular 30 to 50 rpm.

19. The method according to one of embodiments 1-18, wherein the method further comprises a pasteurization step at a temperature of at least 60°C, preferably at least 70°C, in particular at least 80°C.

20. The method according to one of embodiments 1-19, wherein the method further comprises a pasteurization step lasting at least 1 min, preferably at least 3 min, in particular at least 5 min.

21. The method according to one of embodiments 1-20, wherein the method further comprises the step of heating the fruit before adding the PME to the fruit filling to at least 50°C, preferably at least 65°C, in particular at least 75°C.

22. The method according to one of embodiments 1-21, wherein the method further comprises the step of heating the fruit before adding the PME to the fruit filling for from 1 to 120 minutes, preferably from 2 to 60 minutes, in particular from 5 to 30 minutes.

23. The method according to one of embodiments 1-22, wherein the method provides an improved consistency defined by a reduction in Bostwick units by at least 1, preferably at least 2, in particular at least 3 Bostwick units [cm/min].

24. The method according to one of embodiments 1-23, wherein the method provides an improved consistency defined by a reduction in Bostwick units by at least 5, preferably at least 6, in particular at least 7 Bostwick units [cm/min].

25. The method according to one of embodiments 1-24, wherein the method provides an improved consistency determined by a reduction in Bostwick units by at least 20%, preferably at least 25%, in particular at least 30%.

26. The method according to one of embodiments 1-25, wherein the method provides improved consistency, defined by a reduction in Bostwick units by at least 40%, preferably 50%, in particular at least 60%.

27. The method according to one of embodiments 1-26, wherein the method excludes the addition of an active viscosity-reducing enzyme to the process.

28. The method according to one of embodiments 1-27, wherein the method eliminates the addition of active polygalacturonase (PG) enzyme in the process.

29. The method according to one of embodiments 1-28, wherein the fruit filling is a filling that is not a fruit filling from the fruits of nightshade crops, in particular, it is not a fruit filling from potatoes, tomatoes or eggplants.

30. The method according to one of embodiments 1-29, wherein the process, at least the fermentation step, is carried out without applying a high pressure of 300 MPa or more, preferably without applying a pressure of 180 MPa or more, in particular wherein the fermentation step is carried out under atmospheric pressure conditions.

Claims (26)

1. A method for producing a stable fruit filling, comprising the steps of adding an active pectin methyl esterase (PME) to a fruit filling to carry out a fermentation step of the fruit filling, followed by inactivating the PME in the fruit filling to produce a stable fruit filling, wherein gelation is prevented or at least significantly reduced in the presence of the active PME in the fruit filling by applying mechanical stress to the fruit filling containing the active PME, thereby providing an improved consistency determined by a decrease in Bostwick units of at least 1 Bostwick unit, cm/min, wherein Bostwick units are measured in accordance with ASTM F1080-93, including equilibrating the samples at 20°C with additional mixing with a propeller mixer for 25 s at 25 rpm, wherein the decrease in Bostwick units is a decrease compared to the fruit filling without fermentation, as well as in comparison with a fermented food filling that is not subjected to mechanical stress during fermentation; wherein a mechanical stress of 1 to 100 Pa is applied to the fruit filling containing the active PME by means of stirring, shaking, pumping or combinations thereof. 2. The method according to claim 1, wherein the fruit filling is a puree. 3. The method according to claim 1 or 2, wherein the puree or fruits used for the fruit filling are subjected to heat treatment before the fermentation stage. 4. The method according to claim 3, wherein the heat treatment is carried out at a temperature of 60 to 110°C, preferably 75 to 95°C. 5. The method according to claim 3 or 4, wherein the heat treatment is carried out for 30 s to 30 min, preferably for 5-10 min. 6. The method according to one of claims 1-5, wherein a mechanical stress of 3 to 20 Pa is applied to the fruit filling containing the active PME by means of stirring, shaking, pumping or combinations thereof. 7. The method according to one of claims 1 to 6, wherein the fruit fillings are fillings selected from strawberry 2 (Fragaria ananassa), peach (Prunus persica), apricot (Prunus armeniaca), fig (Ficus carica), pear (Pyrus), cherry (Prunus cerasus), sweet cherry (Prunus avium), apple (Pyrus malus, Malus pumila), blueberry (Vaccinium cyanococcus), mango (Mangifera indica), banana (Musa acuminata); or mixtures thereof. 8. The method according to one of claims 1 to 7, wherein the fruit filling comprises pieces of fruit or whole fruit. 9. The method according to one of claims 1 to 8, wherein the fruit filling contains additional nutritional components, preferably cereals, seeds, nuts or mixtures thereof. 10. The method according to one of claims 1 to 8, wherein the stable fruit filling consists of fruit in the form of fruit puree, fruit juice, fruit pieces or mixtures thereof and inactivated PME. 11. The method according to one of claims 1 to 10, wherein Ca ²⁺ ions are added during production, in particular Ca ²⁺ ions are present before the PME is inactivated. 12. The method according to one of claims 1 to 10, wherein Ca ²⁺ ions are not added during production, in particular Ca ²⁺ ions are not present until the PME is inactivated. 13. The method according to one of claims 1 to 12, wherein the filler has a pH of from 3.0 to 7.0, preferably from 3.2 to 5.5, in particular from 3.5 to 4.2. 14. The method according to one of claims 1 to 13, wherein the stable fruit filling is packaged in a form that is stable for storage. 15. The method according to one of claims 1 to 14, wherein the method further comprises a step of heating the fruit before adding the PME to the fruit filling and a step of heating after enzymatic treatment of the PME, in particular a pasteurisation step, wherein preferably mechanical stress is also applied during the heating step, in particular at temperatures below 70°C. 16. The method according to one of claims 1 to 15, wherein the fermentation step is carried out for 1 to 120 minutes, preferably 2 to 60 minutes, in particular 5 to 30 minutes. 17. The method according to one of claims 1 to 16, wherein the fermentation step is carried out at a temperature of from 20 to 60°C, preferably from 30 to 50°C, in particular from 35 to 40°C. 18. The method according to one of claims 1 to 17, wherein the fermentation step is carried out with stirring at a speed of 10 to 500 rpm, preferably 20 to 100 rpm, in particular 30 to 50 rpm. 19. The method according to one of claims 1 to 18, wherein the method further comprises a pasteurization step at a temperature of at least 60°C, preferably at least 70°C, in particular at least 80°C. 20. The method according to one of claims 1 to 19, wherein the method further comprises a pasteurization step lasting at least 1 min, preferably at least 3 min, in particular at least 5 min. 21. The method according to one of claims 1 to 20, wherein the method further comprises the step of heating the fruit before adding the PME to the fruit filling to at least 50°C, preferably at least 65°C, in particular at least 75°C. 22. The method according to one of claims 1 to 21, wherein the method further comprises the step of heating the fruit before adding the PME to the fruit filling for from 1 to 120 minutes, preferably from 2 to 60 minutes, in particular from 5 to 30 minutes. 23. The method according to one of claims 1 to 22, wherein the improved consistency is determined by reducing the Bostwick units by at least 2, in particular at least 3 Bostwick units, cm/min. 24. The method according to one of claims 1 to 23, wherein the improved consistency is determined by reducing the Bostwick units by at least 5, preferably at least 6, in particular at least 7 Bostwick units, cm/min. 25. The method according to one of claims 1 to 24, wherein the improved consistency is determined by a reduction in Bostwick units by at least 20%, preferably by at least 25%, in particular by at least 30%. 26. The method according to one of claims 1 to 25, wherein the improved consistency is determined by reducing the Bostwick units by at least 40%, preferably by 50%, in particular by at least 60%.