WO1997015198A1

WO1997015198A1 - Composite food product with moisture barrier

Info

Publication number: WO1997015198A1
Application number: PCT/EP1996/004652
Authority: WO
Inventors: Wilhelmus M. J. G. Heuvel; Stephen David Lewis; Kevin John Povey
Original assignee: Unilever N.V.; Unilever Plc
Priority date: 1995-10-23
Filing date: 1996-10-18
Publication date: 1997-05-01
Also published as: AU7492696A

Abstract

A composite food product is provided that has a keepability at 5 °C of at least 4 weeks, preferably at least 6 weeks, comprising a first edible material having a water activity of at least 0.90 and a second edible material having a water activity of at most 0.6, said edible materials being in contact with and being separated by a fat continuous edible barrier, the fat of that barrier being a triglyceride fat having a solid fat content of at least 70 % at 5 °C and having on at least 50 % of the available glyceride positions, esterified fatty acid residues having a chain length of 12 - 18 C atoms, wherein the barrier has a composition selected from the group consisting of: a composition (A) comprising 70 - 100 wt.% of said fat, and a composition (B) comprising: 40 - 95 % of said fat, and 5 - 60 % of lactose, the combined amount of fat and lactose constituting 80 - 100 % of the composition (B).

Description

Composite food product with moisture barrier

The invention relates to a composite food product having a keepability at 5 °C of at least 4 weeks comprising two edible materials having different water activities said edible materials being in contact with and separated by an edible moisture barrier.

Moisture migration between materials having different water activities in a composite food product has long been known to be a problem adversely affecting the keepability of such products. Many proposals have been made to reduce or overcome the problem. Most work has concentrated on edible moisture barriers, to be included in the product, physically separating the materials with different water activities. Alternative approaches have been studied as well but these efforts have not produced solutions that are effective, practically feasible and applicable to a wide range of different product types.

Specific moisture barriers that are applicable only for special types of products have been developed as well. For example US 4,820,533 proposes a barrier consisting of a rigid substrate in the form of a sheet, e.g. a cookie, biscuit or wafer, covered on both sides with a layer based on shellac. One of the shellac based layers can be replaced or supplemented with a fat based layer, e.g. chocolate or compound or dairy fat based. Basically the edible fat layer can be based on any edible fat or fat based composition. The rigidity of the substrate of the barrier limits its practical applicability, while the use of shellac in food is considered undesirable by many customers. WO 93/24024 discloses products which are packed in a beaker. At the bottom of the beaker for example a layer of crispies is packed. The crispies may have been provided with a choco- coating. On top of this, a layer of fat or oil containing material is poured. The remainder of the beaker is filled with a product such as yoghurt . The fat or oil containing material should contain at least 70% fat or oil. The materials should be creamy at 5 - 20 °C and should have a viscosity at 5 °C of at most 40000 cP and at 20 °C of at least 5000 cP. To achieve this at least 50% of the fat or oil employed, is oil substantially liquid at 20 °C. Use of such an approach to preventing moisture migration is restricted to products packed in a beaker or similar container. Furthermore the barrier layer has to be rather thick to be effective.

A lot of proposals have been made for use as moisture barrier of film or coating-like material containing as an essential component, protein, e.g. a milk protein or collagene. Examples of such barriers are given in e.g. EP 465,801, DD 296 829, EP 393 361 and EP 383 134.

WO 92/01394 describes as moisture barrier a film comprising protein and polysaccharide, partially or completely coated with a hydrophobic material. As hydrophobic material, e.g. coconut oil, beeswax, palm oil, palmkernel oil, acetylated monoglyceride, glycerol monostearate, steroyl lactate and polyglycerolester can be used.

EP 451 491 discloses a barrier coating comprising a mixture of an edible fat and a milk protein in the form of a membrane. The barrier coating may comprise up to 60% sugar. For example chocolate can be used as the coating.

Other publications disclose the use of lipids or lipid based compositions as barrier against moisture migration. EP 375240 describes such coating containing as lipid, polyol fatty acid esters containing at least 4 fatty acid ester groups. DE 3921454 recommends the use of a moisture barrier layer for cream gateaux. The layer can be chocolate, nougat, icing or fat with a high melting point. EP 509 566 recommends for preventing moisture migration between puff pastry and its filling to apply a layer of pastry dough onto the puff pastry dough and onto the pastry dough a layer of wax, sucrose polyester or triglyceride, particularly preferred being aceto-fat. Also disclosed is the use of mixtures of liquid vegetable oil and partially hydrogenated fat in addition to or replacement of the aceto-fat. EP 183595 describes to coat fish with a fat layer of e.g. lard, tallow, palm oil, cocoa butter, and apply bread crumbs or pepper to the outside coating. The fat layer reduces moisture migration from the fish to e.g. the breadcrumbs during storage and serves as fat to fry the fish in.

EP 23152 describes the coating of ice-cream with a fat- based barrier.

FR 2680635 describes the use of a barrier layer to separate a wafer and ice-cream. GB 2263615 describes converture coated ice cream products comprising a moisture barrier.

The scientific literature also shows many papers related to the area. J. Food Science, 4.2, (1984) , 1478 - 1481 and 1482 - 1485 describe studies on edible bilayer films, in particular films of stearic and palmitic acids as one layer and hydroxy propyl methylcellulose as the other. JAOCS (1960) , 3_7_, 1-4 investigates layers of cocoabutter in different polymorphic forms, of fully hydrogenated cottonseed oil and mixtures of such oils with liquid cottonseed oil, chocolate liquor and sweet milk chocolate, and paraffin. J. Food Science 53 (4) . (1988) , 989-998 is concerned with layers of chocolate . However these studies are mostly confined to assessment of water vapour permeability through the layer. They are of limited value for practical applications because vapor phase diffusion is only one of the mechanisms involved in moisture migration. Food Technology, December 1986, 47 - 59, a comprehensive review on edible films and coatings, mentions as examples of additional mechanisms, liquid diffusion driven by a water concentration gradient, liquid movement caused by capillary forces and surface diffusion of adsorbed water at solid interfaces. Such other mechanisms are particularly applicable in case of chilled food products. For example at 3 °C, a relative humidity of 100% corresponds to a water vapour pressure of only 5.7 mmHg. Of the above papers only J. Food Science 53 (4) . (1988) , 989 - 998 takes the investigation a step further and studies gels with high and low water activity at 20 °C in contact with the film. It concludes: these results obtained in ideal conditions substantiate the potential of chocolate coatings as moisture barrier in heterogeneous mixed moisture foods.

Thus, the prior art makes many suggestions about barriers to reduce moisture migration. However, none of them gives guidance how to select from all these possibilities a set of appropriate barriers for use in composite food products requiring a keepability at 5 °C of at least 4 weeks wherein one part has an a_w of at least 0.90 while the part adjacent to it has an a_w of at most 0.6. Most of the above barriers were developed in relation to products requiring only a short keepability at temperatures above 0 °C, for example fish coated with breadcrumbs or pepper, and doughs supplied with fillings, e.g. pizza's and other bakery items. Such products are usually consumed within a few days or are stored frozen. Furthermore, in the systems described in the prior art mostly the a_w's of the parts to be separated are less extreme. For example, WO92/01394 reports for both the pastry and the materials put on top of it, a_w- values well above 0.90. In other studies, the a_w values of the parts to be separated were both below 0.85. This can make a dramatic difference. For example, J. Food Science (1984) , 4_9_, 1482 - 1485, reported for their study on water vapour permeability of the bilayer film comprising stearic or stearic and palmitic acids as one of the layers:

* The water vapor transmission rate increased from 4.2 g/m² day at 90% RH to 25.5 g/m² day at 97% RH.

* The permeability did not only depend on the RH gradient but also on the absolute values of RH between which the difference was kept constant: the permeability value increased from 0.69 (g) (mil)/ (m²) (day) (mmHg) for the 65-33% RH range to 10.1

(g) (mil)/(m²) (day) (mmHg) for the 97-65% RH range. The paper concludes that one should only consider applying the film in foodsystems in which the water activity of the high a_w component is below 0.90. Furthermore, few studies were addressed to inhibiting moisture migration at chilled temperature, e.g. about 5 °C.

We have studied this problem and we found the suggestions in the prior art of little help. For example, we found, as illustrated in the examples, the performance of chocolate and of aceto-glycerides as barriers in the present systems to be poor. Furthermore we found that some barriers substantially adversely affected the eating quality of the food product. But we also found barriers that had very satisfactory performance.

Accordingly, the present invention provides a composite food product having a keepability at 5 °C of at least 4 weeks preferably at least 6 weeks, comprising a first edible material having a water activity of at least 0.90 and a second edible material having a water activity of at most 0.6, said edible materials being in contact with and being separated by a fat continuous edible barrier, the fat of that barrier being a triglyceride fat having a solid fat content of at least 70% at 5 °C and having on at least 50 % of the available glyceride positions, esterified fatty acid residues having a chain length of 12-18 C atoms, wherein the barrier has a composition selected from the group consisting of

* a composition (A) comprising 70 - 100 wt % of said fat and

* a composition (B) comprising

40 - 95% of said fat, and 5 - 60% of lactose, the combined amount of fat and lactose constituting 80 - 100% of the composition (B) .

Food products which are intended to be kept frozen such as ice-cream are generally not stable for 4 weeks at 5°C and hence then not covered by the present invention.

Preferred embodiments of the invention are described in claims 2 - 10.

We found that in order to obtain a satisfactory barrier in this kind of food product, the barrier should be fat continuous, and should predominantly consist of triglyceride fat. We found only one exception to this rule. If in the fat a substantial amount of lactose is incorporated an even better barrier may be obtained. If instead of lactose, e.g. sucrose is employed the barrier performance is not good. Limited amounts of other materials can be incorporated in the barriers consisting predominantly of fat or fat and lactose, e.g. cocoapowder or milkprotein. Such further inclusions preferably constitute less than 10%, more preferably less than 5% of the barrier composition, and most preferably they are substantially not present at all. In particular incorporation of any significant amount of water in the barrier composition is dispreferred. Barriers of fat and lactose perform particularly well if the barrier composition consists essentially of 40 - 80 wt % fat and 60 - 20 % lactose, more preferably 50 - 70 wt % fat and 50 - 30 % lactose.

We further found that for satisfactory results, the triglyceride fat employed must have a solid fat content at 5° C of at least 70%, preferably at least 75%, more preferably 80 - 95 %. The solid fat content can conveniently be measured using NMR. The sample to be measured is conditioned by heating the fat to a temperature of at least 60 °C, keeping the sample for at least 10 minutes at 60 °C, then keeping it for 60 minutes at 0 °C, and subsequently for 30 minutes at the measuring temperature. A further requirement for the fat is that at least 50 % of the available glyceride positions are esterified with fatty acid residues that have a chain length of 12 - 18 carbon atoms. Preferably, substantially all available glyceride positions are esterified with fatty acid residues. Thus, the content of mono- and diglycerides in the fat is preferably low, e.g. 7 % or less, more preferably 0 - 5 %, especially 0 - 3 %. Free glycerol is preferably not present at all. If the amount of not- esterified glyceride positions is insignificant, then the above requirement is equivalent to the requirement that at least 50 mole % of the fatty acid residues of the fat have a chain length of 12 - 18 carbon atoms. If more than 50 mole % of the fatty acid residues had shorter chain length or if the combined amount of such shorter acids and un- esterified glyceride positions was more than 50 % of the totally available glyceride positions, while providing the required solid fat content at 5 °C, as in the case of aceto-fat either the prevention of moisture migration was inadequate or poor eating qualities resulted, or both. If a fat with more than 50 mole % of fatty acids having a chainlength longer than 18 C-atoms, having an N5 above 70 was used, the barrier was waxy and caused the product to have an unpleasant mouthfeel. To prevent such waxiness, the fat should have the above specified fatty acid chain length and should further preferably have a slip melting point of at most 48 °C, more preferably 28 - 43 °C, particularly 30 - 35 °C.

Most of the prior art addresses the problem of moisture migration from the point of view that increase of moisture in the low a_w material adversely affects the quality of that component. For example, increase of moisture in pastry or pizza bottoms, makes such bakery materials loose their crispness. However, in some types of composite foodproducts, additional problems can arise, for example, in foodproducts in which the high a_w material forms the centre part of the product and the low a_w material constitutes a layer partly or wholly covering the centre part with the barrier in between the 2 parts. In such products, the low a_w material can for example be a fat based coating for example a chocolate type material. In such products, a substantial amount of moisture reaching the coating may cause the coating to crack and may cause it to become soggy, i.e. the chocolate would loose its desired snap. Water may then evaporate from the coating and cause condensation on the inside of the packing material. But apart from such problems, there are other complications. Even if the moisture in the coating does not reach levels high enough to cause this kind of problems, the barrier may not be good enough. If for example the barrier itself takes up a significant amount of water, whether or not it allows it to go into the coating, the loss of water in the centre part may cause it to shrink thereby creating a gap between the centre and the barrier/coating. Furthermore, in such kind of products the loss of moisture from the centre can rapidly cause a perceivable adverse effect on the eating quality of the centre. Therefore, the barrier should not only prevent too much water reaching the low a_w material, it should also prevent too much loss of moisture from the centre part.

We found it preferable for at least 60 mole %, more preferable for at least 70 mole % of the fatty acid residues of the triglyceride fat to have a chainlength of 12 - 18 C atoms. We further found it preferable for at least 50 mole %, preferably at least 60 mole %, more preferably at least 70 mole % of the acid chains to have a chainlength of 16 - 18 C atoms. We found for example that fats with high contents of C12 - C14 acids may be difficult to handle. For example, high a_w material will in practise often be fairly soft. It may then be convenient to freeze such material before applying a barrier. We found that in such cases when using fats with high contents of C8 - C14 fatty acids, e.g. coconut fat or palmkernel oil or hydrogenated palmkernel oil as the barrier fat, the barrier had a tendency to crack, possibly due to fast crystallisation and shrinkage upon coming into contact with the frozen material.

Furthermore we found that with some fats the barrier layer in the product may be somewhat brittle. This may cause the product to be troublesome to eat, e.g. pieces of barrier fragmenting and flying away while cutting the food product or biting into it. Brittleness may also make the barrier vulnerable. A brittle barrier is at risk of cracking during handling the product, e.g. during transport. A brittle barrier may show excellent performance in preventing moisture migration under test conditions in the laboratory, in actual practice its performance may be poor due to cracking caused by the handling of the product. We found that such risks can be reduced and accordingly it is preferred to incorporate in the fat 1 - 50 mole % of fatty acid residues having a chainlength of 2 - 14 C atoms, preferably 4 - 14 C atoms. An amount of 3 - 20 mole % of such fatty acid residues is particularly preferred. The balance of the fat preferably consists substantially, i.e. for 95% or more of C 16 - C 18 fatty acid residues.

If a barrier predominantly consisting of fat and lactose is employed, depending on the ratio applied, the risk of brittleness may be less pronounced, and only little benefit may be obtained from incorporating such shorter chain fatty acid residues into the fat.

To obtain all the above desired properties of the fat we found it particularly advantageous to employ as primary source of C16 - C18 fatty acid residues, fats having high contents of symmetrical HUH triglycerides, particularly HOH triglycerides, wherein H indicates palmitic and stearic acid residues, U indicates oleic and linoleic acid residues and O indicates oleic acid residues, e.g. stearin fractions of high stearic acid containing versions of soyabean oil, rapeseed oil, sunflower oil etc. and particularly cocoabutter, palmoil mid fractions, illipe fat, shea oil stearin and sal fat stearin and mixtures of 2 or more of such fats. As primary sources of the shorter chain fatty acids we found particularly the use of butterfat and optionally hydrogenated, fractionated and/or interesterified coconut oil and palmkernel oil and mixtures of 2 or more thereof to be beneficial. The source of the C16 - C18 fatty acids and the source of the shorter chain fatty acids may be mixed and interesterified and/or modified otherwise, but preferably the fat used in or as the barrier composition consists of a mixture of the C16 - C18 fatty acid source and the source of the shorter chain fatty acids, which mixture has not been modified otherwise. As used herein, the term modification does not include refining of the fat for the removal of undesired colour, flavour or other undesirable minor components f om the fat . As an alternative to prevent brittleness, fat rich in HUH triglycerides, and especially HOH triglycerides as mentioned above can also be mixed with a small amount of a lower melting oil, preferably an oil rich in H00 triglycerides. For example palmoil can be used for this purpose, the use of palm oil olein being particularly preferred. In such an approach however, care should especially be taken that N5 does not become lower than 70. With this kind of fat composition an N5 of 80 - 90 is particularly preferred.

The barrier can be applied on one of the edible materials in conventional manner, e.g. by spraying, brushing or enrobing. If the fat employed in or as the barrier is a polymorphic fat having a high content of symmetrical HUH triglycerides, the barrier composition is preferably tempered before applying it to one of the edible materials. Tempering can be done as is commonly applied in the chocolate industry. However, we found that especially if the barrier is applied onto a material that is frozen, and the product is subsequently kept at a temperature at or below about 5 °C, such fats can also be applied without tempering. No adverse effects have been observed from the use of such untempered fats in products kept for a period exceeding 8 weeks. In a preferred approach the barrier is applied to a shaped portion of the first edible material. Suitably this is done by enrobing the shaped portion with top and bottom enrobing as is commonly applied in the confectionery industry. The barrier composition should have a proper viscosity for this purpose. Depending on the composition applied this can usually be achieved at a temperature of about 35 - 50 °C, particularly about 40 °C. If the first edible material is soft, it can be beneficial to prepare the shaped portions in frozen condition, e.g. at -20 °C and enrobe them while they are frozen. After the fat in the barrier has crystallized sufficiently then the second edible material can be applied, e.g. also by enrobing. If so desired, before applying the second edible material, the shaped portion with the barrier applied to it, may first be cooled back, e.g. to -20 °C.

Preferably the preparation is carried out such that the barrier constitutes a layer in the product between the first and second edible material having a thickness of 0.2 - 3.0 mm, preferably 0.5 - 1.5 mm.

The water activity of the first edible material of the food product preferably is 0.93 - 0.99, more preferably 0.95 - 0.98. Preferably the first edible material is watercontinuous and has a pH of 3.8 - 5.2, particularly 4 - 5. Preferably it includes 40 - 70 % water, and 6 - 20 % preferably 8 - 15 % protein. It further suitably contains 3 - 30 % preferably 5 - 25 % carbohydrate, particularly mono- and/or disaccharides and 10 - 30 % preferably 15 - 25 % fat. In a particularly preferred embodiment the first edible material comprises at least 50 % unripened soft cheese, also referred to as fresh cheese, Frischkase or Fromage frais, or a similar material on the basis of acid casein, contains at least 8 % protein and has a pH of 4.0 - 5.1. It may further include sugar, syrup, pieces of nuts or fruits or the like, fruit puree etc. The material preferably includes gas, e.g. nitrogen, preferably corresponding to an overrun of 5 - 100 %, preferably 10 - 50 %.

The second edible material preferably has a water activity of at most 0.55, more preferably of 0 - 0.50. Preferably it has a continuous fat phase. It is particularly preferred that it is substantially waterfree. In particular it includes at least 20 %, preferably at least 25 % of fat having an N5 of at least 70, preferably at least 75, and mono and/or disaccharides in particular sucrose. Optionally it includes dry milk constituents and/or dry cocoapowder possibly incorporated in the edible material in the form of cocoamass or cocoaliquor, and/or material derived from nuts or the like. It may include minor amounts of lecithin, vanillin etc. In a particularly preferred embodiment the second edible material is a chocolate, e.g. real chocolate based primarily on cocoabutter and optionally milkfat as fat or a chocolate imitation product. It is especially preferred for the second edible material to be a white chocolate. The second edible material may also include air or other gas, but this is not a preferred feature.

Preferably, both the first and the second edible material are present in the composite food product as coherent parts of the foodproduct having a defined shape. Thus, they are preferably present as a block, a coherent layer or an otherwise shaped coherent portion, rather than as a fluid or as many individual small particles. The barrier preferably constitutes a layer of fairly homogeneous thickness between the separate parts preventing direct contact between parts of first edible material and parts of second edible material. The composition food product may contain 2 or more coherent parts of first or second edible material or both. It may e.g. comprise a plurality of layers of alternately first and second edible material. In such case preferably barrier is applied everwhere appropriate to prevent direct contact between first and second edible material .

Preferably, the first edible material constitutes the centre part of the product, the barrier constitutes a layer fully covering the surface of the centre part, e.g. applied by enrobing, and the second edible material constitutes a layer fully covering the outer surface of the barrier layer. In such product, preferably the barrier constitutes 5 - 25 %, preferably 8 - 15 % of the product and the second edible material constitutes 15 - 60 %, preferably 20 - 40 % of the product, the balance consisting of first edible material.

Throughout this specification except where indicated otherwise, all parts, proportions and percentages refer to weight, except in relation to fatty acid residues which are expressed in mole and in relation to gas which is expressed with reference to volume.

Examples :

Comparative examples A

Trials were done wherein as low a_w component a white chocolate was used. The a_w of the chocolate was 0.46. No barrier layer was used in these trials. The white chocolate had the following composition:

29.7 parts cocoabutter

46.4 parts sugar 23.5 parts full fat milk powder p.m. lecithin p.m. vanillin

As high a_w component, 2 compositions were used having an a_w of 0.75 and of 0.97, respectively. As material having an a_w of 0.75, large pieces of Turkish Delight were used. The material with the a_w of 0.97 had the following composition: fresh cheese (22% fat) 90 parts

Sucrose 9 parts locust bean gum 0.5 parts flavour 0.5 parts

From this high a_w composition, shaped portions to constitute the centre part of the composite foodproduct, were prepared as follows: All ingredients were mixed in a Stephan cutter, the mixture was heated to 79 °C, pasteurized and then cooled to about -2 °C. The cooled material was extruded into a strand having a height of 16 mm and a width of 24 mm. The strand was cooled down to -25 °C and cut into pieces of 50 mm length. The weight of the centre pieces thus obtained was 18 g. Analysis of these parts gave the following results Dry matter 43.7 %

Protein 9.5 % Fat 20.1 %

Carbohydrate 13.7 % pH 4.6

From the pieces of Turkish Delight, a thin surface layer was removed. The resulting pieces were somewhat but not much smaller than the pieces of a_w = 0.97 material. The Turkish Delight pieces were also cooled to -25 °C.

The chocolate composition was processed in a manner as conventionally applied in the confectionery industry, except that no tempering was applied. The frozen centre pieces were enrobed using top and bottom enrobing with the chocolate composition which had a temperature of 37 °C. The amount of chocolate in the endproduct was 30 % in both cases. The products were packed in sealed plastic foil.

The products were stored at 5 °C and evaluated after 4 and 8 weeks. After 8 weeks, in the product with the a_w = 0.75 centre, the moisture content of the chocolate was still only 1%. No cracks had formed in the chocolate layer and no other product defects were observed.

For the product with a_w = 0.97 material in the centre, after 4 weeks the moisture content of the chocolate had increased to 21%. After 8 weeks, no further increase was noted. After 4 weeks substantial cracks had developed in the chocolate layer and after 8 weeks the cracks were worse. The taste and texture of the centre after 4 and 8 weeks had notably deteriorated due to moisture loss, at some part of the product a gap had developed between the centre and the chocolate and visible condensation had occurred on the inside of the packaging material.

These trials show the enormous difference in possible problems caused by moisture migration in this kind of system depending on whether the a_w of the primary edible material is moderately high (0.75) or high (0.97) .

Comparative example B

In these trials aceto-glycerides and beeswax were evaluated as barrier. The same white chocolate as in comparative example A was used (code W2) . In addition also a chocolate including lactose was employed (code Lac) . Its composition was: Sucrose 23.2 %

Lactose 23.2 % Cocoabutter 43.2 %

Full cream milk protein 10.0 %

Vanilla p.m.

Lecithin p.m.

As high a_w component, the same material as described in comparative example A having a_w = 0.97 was used.

The aceto-fat used was Admul AC 2722K ex Quest Naarden Netherlands. It contained 32 % C2 acid residues and 32 % C16-C18 acid residues calculated on the availably glyceride positions. The balance of the glyceride positions was not esterified. Its N5 was 96. The White beeswax used was pharmacopea grade ex Exeter bee supplies.

The shaped portions to constitute the centre parts of the products, were produced as described in comparative example A and cooled to -20 °C. Barrier composition was heated to 60 °C. The centre part was dipped halfway into the barrier composition for about 2 seconds, the barrier was allowed to harden for about 1 minute, then the other half of the centre was dipped into the barrier composition such that a small overlap with the first applied barrier material was created. The products were cooled to -20 °C, then the chocolate coating was applied by enrobing and the product was packed and stored as described in comparative example A. For comparison, also product without barrier was produced.

The barrier and chocolate were applied such that they accounted for 10% and 27% of the endproduct respectively.

The products were evaluated upon storage during a period of 8 weeks. Evaluation included panel assessment of cracking in a 0-4 scale with the following meaning 0 : no cracking 1 very slight damage to chocolate layer 2 borderline acceptable cracking 3 unacceptable cracking 4 severe cracking

The moisture content of the barrier plus coating was analyzed, and also the moisture content of the centre portion. From this the moisture loss of the centre portion, expressed in percentage points reduction in water content of the centre part, was calculated.

The evaluation also included qualitative assessment of the eating quality of the products. The following results were obtained:

Chocolate Barrier Moisture Moisture content in loss in chocolate + centre barrier (% ) portion (% points)

Storage 0 4 8 0 4 8

W2 - 0 21 20 0 14 13

W2 aceto-fat 0 10 11 0 7 7

Lac aceto-fat 0 9 10 0 6 7

W2 beeswax 0 3 3 0 2 2

Lac beeswax 0 3 3 0 1 2

Chocolate Barrier Cracking of chocolate

Storage (weeks) 1 2 3 4 6 8

W2 - 0 0 2 3 4 4

W2 aceto-fat 0 1 1 1 2 3

Lac aceto-fat 0 1 1 1 3 3

W2 beeswax 0 0 0 0 0 0

Lac beeswax 0 1 1 1 1 1

In a blind evaluation by the trained panel 3 days after production, the products with beeswax as barrier were rejected because of the waxy impression that the products gave in the mouth. A criticism on the products with aceto- fat as barrier was that they were gummy. The product got stuck in an unpleasant way to the teeth. Furthermore, the panel found that both the beeswax and the aceto-fat had a negative influence on the taste of the product. Upon storage the products without barrier and those with aceto-fats are found by the panel to deteriorate. The chocolate became somewhat soggy and lost its snap. The centre parts texture and mouthfeel was judged to have become less good. The products with beeswax as barrier were found to change very little during the storage.

These trials showed:

* aceto-fat as barrier shows some reduction of moisture migration but not nearly sufficient to provide the desired shelflife.

* both aceto-fat and beeswax are unacceptable as barrier because of their adverse effect on the eating quality of even the fresh product . * the precise composition of the chocolate employed does not have a major influence on the moisture migration nor on the customer perceivable changes in product properties caused by moisture migration.

Examples 1 - 2 and comparative examples C - E Comparative example B was repeated except that

* trials were only done with W2 chocolate as low a_w edible material .

* the temperature of the barrier composition was 50 °C. * the chocolate too was applied by dipping into the molten chocolate mass of 37 °C, in a similar way as was done for the barrier.

the amount and type of barrier applied were:

Example Barrier composition Amount (% on end produkt)

Comp. Ex. C - -

Comp. Ex. D W2 27

Example 1 Cocoabutter (CCB) 10

Example 2 50% CCB + 50% lactose* 27 omp. Ex.E 50% CCB + 50% sucrose 10 crystalline lactose was used

The amount of low a_w component, i.e. W2 chocolate, applied as outer layer of the product was 27 % calculated on end product.

The cocoabutter employed had an N5 of 91. Conversion to methylesters and GLC analysis showed that of its fatty acid residues about 99 mole % had a chainlength of 16 - 18 C atoms. The balance consisted mainly of C20 and C22 acid while a very small amount of C14 was detected. It had a slip melting point of about 34 °C. The content of mono- and diglycerides of the cocoabutter were 0.2 % and 2.2 % respectively. Free glycerol was not found. Only about 1 % of the available glyceride positions were not esterified with fatty acid residues.

The development of the moisture content of the barrier plus chocolate layer during storage and the corresponding loss of moisture from the centre in percentage points were: Moisture content of barrier + chocolate (%)

Storage (days) 0 7 14 21 31 37 52 56

Example Barrier

Comp . E . C . - 0 10 .6 15. .2 21 .5 23 .3 25. .0 24 .9 25 .3

Comp . Ex . D W2 0 4 .5 7. .4 9 .7 12 .2 9 .9 13 .0 12 .0

Example 1 CCB 0 2 .4 2 .0 3. .3 6. .0 4. .9 6. .9 8. .3

Example 2 CCB + lactose 0 4 .5 2 .4 2 .0 2. .2 2. .3 2, .3 2. .2

Comp . Ex . E CCB + sucrose 0 4 .1 6. .2 7. .0 8. .3 9. .2 11. .9 10. .3

Moisture loss f rom centre pa rt (pe rcentage points) •

Comp . Ex . C _ 0 5.1 7.3 10.3 11.2 11.9 11. .9 12, .1

Comp . Ex . D W2 0 4.3 7.1 9.3 11.7 9.5 12 .5 11. .5

Example 1 CCB 0 1.5 1.3 2.2 3.9 3.2 .5 5. .5

Example 2 CCB + lactose 0 n.d 2.3 1.9 2.1 2.2 2 .2 2. .1

Comp . Ex . E CCB + sucrose 0 2.7 4.1 4.6 5.5 6.0 7. .8 6. .8

Except for the product without barrier, during the first 4 weeks of storage, no cracking occurred in any of the products. The products of example 2 did not crack up to 10 weeks. The other samples showed a bit of cracking within 8 weeks but it did not become a serious problem except in the product without barrier.

The data from the moisture analyses and the comments from the panel on eating quality were consistent with each other:

* For the products without barrier or with W2 or CCB plus sucrose as barrier the moisture loss from the centre upon storage had a quite noticable negative effect on the quality of the product. In these products also substantial gaps developed between the filling and the barrier / coating. * The products with CCB and CCB + lactose as barrier suffered much less from moisture loss from the centre. Very little or no gap developed between the centre and the barrier / coating. The products showed very little quality deterioration during the storage period, especially the product with CCB + lactose was still found to be excellent after 8 weeks storage.

The panel did comment that the CCB barrier was slightly brittle. Overall the product with the CCB + lactose barrier was judged to be the best, that with CCB as barrier was ranked as second best.

Examples 3 - 6

Example 1 was repeated except that both the barrier and the chocolate were applied using bottom and top enrobing on pilot plant scale. The temperatures of the barrier and chocolate compositions were 50 and 37 °C, respectively. To investigate the effect of thickness of the barrier and chocolate layers, trials were also done in which either or both of the layers were applied 2 times. Accordingly products were prepared comprising the following amounts of barrier and chocolate coating:

Amount of barrier Amount of chocolate (% on end product) (% on end product)

Example 3 10 ( lx) 27 ( lx) Example 4 20 ( 2x) 27 ( lx) Example 5 10 ( lx) 54 ( 2x) Example 6 20 ( 2x) 54 ( 2x)

The samples were evaluated 7 times over a storage period of 60 days. The moisture uptake by the barrier + chocolate for all products at all times was less than 2.5%. The 23

corresponding loss of moisture from the centre was less than 2 percentage points.

Products were stable up to 8 weeks with regard to cracking, condensation in the packaging and gap formation between filling and barrier.

Overall there was very little difference between the 4 products, showing that an amount of 10 % barrier calculated on end product, corresponding to a layer of about 1.2 mm thick is sufficient for good performance. The amount of chocolate can be chosen according to consumer preference without significant effect on the keepability of the product.

Examples 7 - 9 and comparative example F

Example 1 was repeated except that as barrier composition the following fatblends were used:

Example 7 8 9 Comp.Ex.F

CCB 100% 80 55 30

Palm oil olein 0% 20 45 70

N5 91 85 74 61

All fatblends comprised about 98 - 99 mole % of C16-C18 acids, about 1 mole % of C20-C22 acids, the balance consisting essentially of C14 acids. The slip melting points of the blends with palm olein were very similar to those of CCB i.e. about 31-34 °C. The amount of unesterified glyceride positions ranged between about 1 % for example 7 and about 2 % for comparative example F.

The samples were evaluated weekly for a period of 8 weeks The averaged results of the 9 evaluations were: Example 8 9 Comp . Ex . F

Moisture in barrier/coating 3.9 4.1 4.3 5.4

Cracking 0.8 1.3 1.9 2.6

Gap 0.8 1.4 1.8 1.9

Condensation 1.5 1.5 2.5 2.5

In the fresh product and after 8 weeks the moisture content of the centre portion was analyzed. The following results were obtained:

Moisture content of centre part (%)

Fresh product After 8 weeks at 5 °C

Ex 7 57.8 54.7 Ex 8 58.0 53.9

Ex 9 58.0 54.0

Comp. Ex F 58.6 51.2

These results illustrate that for barriers with higher N5 values better prevention of moisture migration is achieved.

The panel judged the barrier of example 7 to be slightly brittle. This was less so with the barriers of examples 8 and 9 and the comparative example.

Examples 10 - 13 and comparative example G

Example 1 was repeated except that as barrier composition the following fatblends were used: Example 10 11 12 13 Comp.Ex.G

Hydrogenated palmkernel oil (smp 39 °C) - 12.5% - 50%

CCB - 60 % - - 50%

Coconut oil 80% 12.5%

Coberin ^®* - 100% Palm oil olein 20% 15% - 50% 50%

N5 81.2 85.3 92.2 79.3 68.4

*Coberin is a cocoabutter equivalent ex Loders Croklaan, London, UK, consisting of shea stearin and palmmid fraction.

The proportion of glyceride positions not esterified with fatty acid residues was less than 4 % for all samples. The fats of example 12 and comparative example G consisted for more than 95% of C16-C18 acids. The fatty acid contents of the other 3 examples were approximately as follows.

(mole %) Ex 10 Ex 11 Ex 13

C4-C14 acids 72 22 43

C16-C18 acids 28 77 56

C12-C18 acids 77 92 85

The samples were evaluated weekly for a period of 8 weeks

The averaged results of the 5 evaluations were:

Example 10 11 12 13 Comp.Ex.G

Moisture in barrier/coating 4.1 4.1 3.7 5.8 6.0 Cracking 1.3 1.1 0.3 1.3 2.1

Gap 1.4 1.1 1.1 1.3 1.6

Condensation 1.5 1.9 1.5 1.8 2.5 Taking into account also the observations from the panel evaluation, clearly comparison example G performed less good than the other examples. All these examples were overall still acceptable after 4 weeks storage at 5 °C. Examples 10 - 12 were still acceptable after 8 weeks storage.

Examples 14 - 16

Example 3 was repeated except that the following materials were used as barriers in the indicated amounts.

Example Barrier composition Barrier amount

(% on end product)

14 CCB 10

15 85% CCB, 15% butterfat 10

16 70% CCB, 5% butterfat, 13

25% lactose

Properties of fat used

Example 14 15 16

N5 91 82 88

Unesterified glyceride positions (%) <1 <1 <1

C4-C14 acids (mole %) 0.1 7 3

C16-C18 acids (mole %) 99 92 96

C12-C18 acids (mole %) 99 95 97

After 4 weeks storage at 5 °C all 3 products were still quite acceptable. On the basis of visible and organoleptical evolution the barrier of example 14 was judged to be the most effective in preventing adverse effects of moisture migration. Regarding brittleness of the barrier as perceived by eating the fresh product, example 16 was found to be excellent, example 15 was also very good while the barrier of example 14 was felt to be a little brittle.

Regarding overall evaluation of the product, both fresh and after storage, all 3 products were found to be very good.

Claims

1. Composite food product having a keepability at 5 °C of at least 4 weeks preferably at least 6 weeks, comprising a first edible material having a water activity of at least 0.90 and a second edible material having a water activity of at most 0.6, said edible materials being in contact with and being separated by a fat continuous edible barrier, the fat of that barrier being a triglyceride fat having a solid fat content of at least 70 % at 5 °C and having on at least 50 % of the available glyceride positions, esterified fatty acid residues having a chain length of 12 - 18 C atoms, wherein the barrier has a composition selected from the group consisting of

* a composition (A) comprising 70 - 100 wt % of said fat, and

* a composition (B) comprising

40 - 95 % of said fat, and

5 - 60 % of lactose, the combined amount of fat and lactose constituting 80 - 100 % of the composition (B) .

2. Food product according to claim 1 wherein the fat comprises 1 - 50 mole % preferably 1 - 30 mole %, more preferably 3 - 20 mole % of fatty acid residues having a chainlength of 2 - 14 C atoms, preferably 4 - 14 C atoms.

3. Food product according to claims 1 - 2 wherein the fat comprises at least 50 mole %, preferably 60 - 99 mole %, more preferably 70 - 97 mole % of fatty acid residues having a chainlength of 16 - 18 C atoms.

4. Food product according to claims 1 - 3 wherein the fat has a slip melting point of at most 48 °C, preferably of 28 - 43° C, more preferably of 30 - 35 °C.

5. Food product according to claims 1 - 4 wherein the first edible material has a water activity of 0.93 - 0.99, preferably 0.95 - 0.98.

6. Food product according to claims 1 - 5 wherein the second edible material has a water activity of at most 0.55, preferably 0 - 0.50.

7. Food product according to claims 1 - 6 wherein the barrier constitutes a layer in the food product between the first and the second edible material having a thickness of 0.2 - 3.0 mm., preferably 0.5 - 1.5 mm.

8. Food product according to claims 1 - 7 wherein the first edible material constitutes the centre of the product, the barrier constitutes a layer covering the surface of the centre part and the second edible material constitutes a layer covering the outer surface of the barrier layer.

9. Food product according to claims 1 - 8 wherein the first edible material is watercontinuous and comprises at least 50 % unripened soft cheese or a similar material on the basis of acid casein, comprises at least 8 % protein and has a pH of 3.7 - 5.1.

10. Food product according to claims 1 - 9 wherein the second edible material is a substantially waterfree fatcontinuous material, preferably chocolate, more preferably white chocolate.