WO2001089313A1

WO2001089313A1 - Edible products with coatings comprising amorphous trehalose

Info

Publication number: WO2001089313A1
Application number: PCT/GB2001/002344
Authority: WO
Inventors: Geoffrey Royston O'sullivan
Original assignee: British Sugar PLC
Current assignee: British Sugar PLC
Priority date: 2000-05-26
Filing date: 2001-05-24
Publication date: 2001-11-29
Anticipated expiration: 2002-11-26
Also published as: AU5863301A; GB0012938D0; GB2362555A

Abstract

The invention provides edible products comprising a core and a coating layer, wherein the coating layer comprises a solid, amorphous trehalose. Preferably, the coating layer comprises a substantial fraction of amorphous trehalose. The invention also provides a method of manufacture of such edible products, comprising the step of enrobing a core with a trehalose syrup.

Description

EDIBLE PRODUCTS WITH COATINGS COMPRISING AMORPHOUS

TREHALOSE

The present invention relates to edible products having a coating comprising amorphous solid trehalose, and to processes for the production thereof.

Boiled sweets (also known as hard candies) usually consist of an amorphous glass of sucrose, usually in combination with other sugars such as glucose, glucose oligomers and fructose, together with colouring, flavouring and other additives. The glassy state gives the conventional translucent appearance but has the disadvantage that it is strongly hygroscopic in the case of sucrose and most other common disaccharides, so that water pick-up makes the sweet sticky and can also lead to partial crystallisation giving a grainy appearance. To avoid this, the sweets are either individually wrapped to protect them, or are dusted with icing sugar (the latter option means that the sweets are no longer translucent in appearance). Some disaccharides such as lactose do not form a good glass at all, but instead undergo significant crystallisation to give an unacceptable opaque grainy sweet; such sugars are not used to make boiled sweets.

US-A-5314701 describes a sugar-free hard candy having a multilayer structure in which the external layer comprises a mixture of a first component selected from hydrogenated starch hydrolysates, xylitol, polymers of low-calorie saccharides, or mixtures thereof, and a second component which is a substance that is weakly hygroscopic in its crystalline form, such as hydrogenated isomaltulose, mannitol, erythritol or maltulose. The external layer is applied as a solid or plastic layer by wrapping or coextrusion. There is no mention of applying the external layer by enrobing. There is no mention of the use of trehalose in the external layer, and indeed such use of trehalose (a sugar) would be excluded for sugar-free products such as those of US-A-5314701.

Trehalose (α-D-glucopyranosyl-α-D-glucopyranoside) is a naturally occurring disaccharide that is found in certain fungi and drought-resistaηt plants. It can also be produced by fermentation. Trehalose alone does not make a boiled sweet of good translucent appearance, because of its relatively low solubility compared to sucrose. A significant amount of crystalline trehalose is present in a trehalose boiled sweet, resulting in a grainy visual appearance and poor texture. The trehalose content must be below 50% before a boiled sweet can be made, and even then the trehalose may give some graining.

Similarly, coating a material with trehalose by the conventional edible industry techniques of spraying or panning gives a crystalline coating which would give a boiled sweet an unacceptable grainy non-translucent appearance.

JP-A-9238642 describes the use of a mixture of trehalose and polyol sweeteners in edible compositions. The trehalose is used principally as a non-cariogenic sweetener. The trehalose is intimately mixed with the polyols in the composition, and does not appear to be described as a coating.

JP-A-9154493 describes coating an edible material, such as the centre of a chewing gum, to make it more stable even in high moisture conditions inside the mouth. The coating contains trehalose, apparently in crystalline form.

EP-A-0739986 describes syrups having high trehalose contents, and a range of uses for such syrups. It is stated that the syrups can be formulated as foodstuffs by coating, but there is no suggestion that the resulting coatings contain amorphous trehalose.

It is an object of the present invention to produce edible products exhibiting reduced water pick-up and stickiness compared to amorphous sucrose-based products such as boiled sweets.

It is a further objection of the present invention to produce edible products exhibiting reduced moisture loss over time when exposed to a dry atmosphere.

It is a further object of the present invention to provide -processes for the production of edible products according to the present invention. It has been found that trehalose can be coated onto edible cores, in particular boiled sweets, as an amorphous coating having an attractive appearance. The coatings also reduce the problem of moisture pick-up and stickiness of earlier hard confections. The coatings can also be used to reduce moisture loss from hydrated cores.

Accordingly, the present invention provides an edible product comprising an edible core and a coating layer having a composition different from that of the core, wherein the coating layer comprises solid amorphous trehalose.

Preferably, the coating comprises at least about 50% by weight of sugars (including sugar alcohols, monosaccharides, disaccharides and trisaccharides), and more preferably it comprises at least about 75% of sugars. The trehalose may be the predominant sugar present in the coating. That is to say, it may be present in greater amount than any other sugar in the coating.

Preferably, the coating layer comprises at least about 25% of trehalose by weight of the coating layer, more preferably at least about 50%, and most preferably at least about 80% by weight. The coating layer may consist essentially of solid trehalose, together with optional small amounts of flavourings and colourings. Preferably at least about 50% of the solid trehalose in the coating is substantially or completely amorphous, and more preferably substantially all of the trehalose in the coating is substantially or completely amorphous.

In certain preferred embodiments the coating layer is a hard candy layer, for example a layer consisting essentially of sugars, colorings and flavorings. Preferably, the coating layer is substantially glassy and preferably it is transparent.

Preferably, the coating layer is substantially continuous. This enables the coating layer to provide a barrier to moisture migration into or out of the core. Preferably, the coating layer substantially completely covers the core, and more preferably it does completely cover the core. Typically the mean thickness of the coating layer is from about 0.1 to about 2 mm, more preferably about 0.2 to about 1.0 mm. In certain embodiments the coating layer has a smooth outer surface.

Preferably, the coating layer comprises less than about 20% by weight of water, and more preferably it comprises less than about 10% by weight of water based on the total weight of the coating, still more preferably less than about 5% by weight of water.

Preferably, the coating layer makes up from about 3 to about 20% of the total weight of the edible product, more preferably from about 7 to about 10% by weight of the total weight of the edible product.

In addition to the solid amorphous trehalose, the coating may further comprise other sugars, for example a sugar selected from the group consisting of isomalt, mannitol, and mixtures thereof. Preferably, the coating contains less than about 10% by weight of sucrose, and more preferably it is substantially free of sucrose.

The core of the edible product may be any edible substance that is compatible with a sugar coating. Preferably, the core comprises less than 25% of water on a weight basis. The invention is especially useful to protect cores that are hygroscopic from moisture penetration.

In certain embodiments the product consists essentially of a boiled sweet, and more preferably the core comprises an amorphous glass of sucrose, preferably also comprising glucose, glucose oligomers and fructose, together with appropriate colouring, flavouring and other additives.

In other embodiments the edible product according to the present invention may be a sugar coated medicament. In pharmaceutical applications, the reduced solubility and improved stability at low pH of trehalose compared to sucrose may also be advantageous in controlling dissolution of medicaments in oral drug delivery systems, or for taste masking of bitter or other off-tastes in foods or pharmaceuticals. In other embodiments the edible core comprises fruit pieces, dried fruit pieces, nuts or expanded or rolled cereal grain pieces. For example, the coating may be applied to a breakfast cereal to increase the shelf life of the product by maintaining the moisture contents and individual textures of the component fruits, nuts or cereals in the product over time and under varied temperature conditions. In yet other embodiments the edible core comprises a dough product such as a cookie or a wafer. The invention is especially suitable to reduce moisture migration when the dough product is assembled into a product such as a jam sandwich or an ice cream sandwich.

The edible core may comprise caramel or fruit pieces, for example for use in ice cream products, to minimise moisture migration on storage.

The edible products according to the present invention include foods, pharmaceuticals and animal feed stuffs. In edible applications, the use of coating layers based on amorphous trehalose provide the further advantage that the positive heat of solution of trehalose can mask the negative heat of solution of some other sweeteners as described in our co-pending patent application GB 9911783.0.

Normally, the coating layer is less hygroscopic than the core. Preferably, the coating is less hygroscopic than an equivalent pure amorphous sucrose layer having the same moisture content. That is to say, the coated product shows less weight gain per unit area at 20°C and 65% relative humidity after 24 hours than the core coated with an amorphous pure sucrose layer having the same initial moisture content. This results in reduced stickiness of the products according to the present invention on storage in humid air, relative to pure amorphous sucrose products.

Preferably, the moisture uptake of the product at 65% relative humidity and 20°C after 10 days is less than about 1 % by weight of the product. The coating containing amorphous trehalose is equally useful for preventing moisture loss from food products such as fruit pieces. Preferably, the moisture loss of the product at 10% relative humidity and 20°C after 10 days is less than about 1 % by weight of the product.

The coating on the edible products of the invention reduces moisture migration and moisture pick-up, thereby assisting in the production of boiled sweets and other food products for hot and humid climates with a minimum of protective packaging. The coating layer also provides mechanical support for the core to maintain the shape of the core, as well as providing a moisture barrier.

The coating may also contain small amounts of the ingredients of the core which migrate during the coating process. Addition of a small amount of maltose to the coating, preferably from 0.1 to 20%, based on the weight of the trehalose, may possibly help to control the crystallisation of the trehalose and hence minimise the possibility of grain formation in the coating.

The coating layer may comprise a major fraction of trehalose in combination with up to 50% by weight on a dry solids basis, preferably less than 25% by weight on a dry solids basis of other sugars such as glucose or fructose.

The coating layer may also comprise conventional amounts, preferably from 0.1 to 5% by weight, more preferably from 1 to 3% by weight, of other ingredients selected from the group consisting of: colouring agents; acidulants such as citric acid or other edible acids; flavouring agents such as menthol or other flavouring esters or alcohols, and mixtures thereof.

The sugar in the coating layer is preferably substantially all amorphous. That is to say, it is substantially free of crystalline regions observable by light scattering, and preferably it is substantially free of long range crystalline order detectable by X-ray diffraction. In a second aspect the present invention provides a process for the production of an edible product, comprising the steps of: providing an edible core; and enrobing the core with a sugar syrup comprising trehalose.

Enrobing is a term in the edible industry for a process of applying a layer by dipping into, or passing through a curtain of, an appropriate liquid. In the present invention, the liquid used for enrobing is a syrup comprising the trehalose of the coating layer. The temperature and solids content of the syrup are adjusted to give the ideal viscosity and moisture content of the coating layer. Preferably, the concentration of the syrup is from 50% to 80% by weight total sugars, more preferably 70% to 80% by weight total sugars. Preferably, the temperature of the syrup in the enrobing step is from 20°C to 140°C, more preferably from 100°C to 120°C.

After enrobing, the amorphous applied to the foodstuff is dried by low temperature desiccation or drying. Suitable methods include: (1 ) drying in ambient air for 16 to 24 hours; (2) drying in a traditional stoving room for 16 to 24 hours at 35 to 50°C until dry; (3) drying in conventional cooling tunnels modified to provide air at 45 to 100°C and 0 to 14% relative humidity for 30 to 60 minutes. In any case, the temperature of the coating preferably does not exceed 100°C, more preferably it does not exceed 60°C, in the drying step. Depending of the drying method, the drying step may be followed by a cooling step before packaging the products.

The process according to the present invention is preferably specifically adapted for the production of an edible product in accordance with the present invention.

When enrobing on a commercial scale, the trehalose coating syrup may be used unchanged for some considerable time, often several days. Under these conditions a sucrose coating syrup would darken markedly in colour through caramelisation, while traces of acidulant leached from the edible core would cause some hydrolysis of sucrose to invert sugars. With a coating bath of trehalose syrup, neither of these disadvantages occurs. Therefore, preferably, the step of enrobing is carried out with a syrup that is substantially free of sucrose. The coating layers of the edible products according to the present invention are therefore also preferably substantially free of sucrose.

Specific embodiments of the present invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows graphs of measured weight gain against time in a humid atmosphere for samples of a conventional boiled sweet and the same sweet coated with amorphous trehalose; Figure 2 shows graphs of measured weight gain against time in a humid atmosphere for samples of two different conventional wafers, and for the same wafers coated with amorphous trehalose; and

Figure 3 shows graphs of measured weight gain against time in a humid atmosphere for samples of a short bread biscuit (cookie) and the same biscuit coated with amorphous trehalose.

Example 1

A coated boiled sweet according to the invention was prepared as follows.

A commercially available boiled sweet obtained from a local retail outlet was dipped into a solution of trehalose having a concentration of 80% w/w at a temperature of 115°C for 2 to 5 seconds. This applies a coating that is 3 to 9% of the product by dry weight. The sweet was dried at 45°C for 24 hours at 11 % relative humidity.

The moisture pick-up of the coated boiled sweets was compared with that of uncoated boiled sweets by placing both sweets in atmospheres having controlled relative humidity and temperature.

The uncoated product was more sticky to the touch than the trehalose coated product even at the start of the test. The products were each placed in an atmosphere at 65% RH and 20°C for 7 days, and weighed and inspected at intervals. The weight measurements are shown in Fig. 1. It can be seen that the uncoated sweet takes up water from the atmosphere much more rapidly than the coated sweet. In fact, the uncoated sweet became extremely sticky after only a few hours. The coated sweet remained dry to the touch after 7 days.

In a further test at 75% RH and 20°C, the uncoated sweet underwent complete deliquescence within two days. In contrast, the coated product had taken up only 0.5% w/w of moisture after two days and remained dry to the touch.

Example 2

Ice-cream (1 ) and Pompador (2) wafer products having a moisture content of 12% were coated in a 70% trehalose solution and dried at 45°C. These products were placed in a climatic chamber (65% RH and 25°C) with uncoated reference products.

The results are shown in Figure 2. It can be seen that the uncoated products take up three to five times as much water after 8 and 24 hours. This is highly significant in terms of the retained crispness of the products.

Example 3

Short bread biscuits (cookies) having a moisture content of 28% were coated in a 70% trehalose solution and dried at 45°C. These products were placed in a climatic chamber (65% RH and 25°C) with uncoated reference products.

The results are shown in Figure 3. It can be seen that the uncoated products take up significantly more water after 8 and 24 hours.

Example 4

Jam sandwich products were made from the wafers and biscuits of Examples 2 and 3 and a jam having a moisture content of 84%. The products were then placed in sealed moisture-impermeable packaging and left for several days before assessment of the product texture.

It was found that the uncoated biscuit product was really soft and wet, whereas the coated biscuit was softer than at the start of the test, but still had a snappy texture when broken.

The wafer products were very similar in texture for the coated and not coated products. However, the trehalose coated products retained more of their original crunchy brittle texture.

Example 5

Caramel sandwich products were made from the wafers and biscuits of Examples 2 and 3 and a caramel having a moisture content of 55%. The products were then placed in sealed moisture-impermeable packaging and left for several days before assessment of the product texture.

The uncoated biscuit product did show signs of softening over the period of the text, with the coated product showing very little if any signs of softening. The texture of the coated wafer products remained unchanged over the period of the test, with the non-coated product showing some signs of softening.

These results suggest that products that a number of well known products that combine a caramel with a wafer or short cake biscuit, should prove to be a very successful application for this technology.

The above embodiments have been described by way of example only. Many other embodiments falling within the scope of the accompanying claims will be apparent to the skilled reader.

Claims

1. An edible product comprising an edible core and a coating layer having a composition different from that of the core, wherein the coating layer comprises solid amorphous trehalose.

2. An edible product according to claim 1 , wherein the coating layer comprises at least about 25% of said trehalose by weight of the coating layer on a dry solids basis.

3. An edible product according to claim 2, wherein the coating comprises at least about 50% of said trehalose by weight of the coating layer on a dry solids basis.

4. An edible product according to any preceding claim, wherein the coating layer consists essentially of the solid trehalose, flavourings and colourings.

5. An edible product according to any preceding claim, wherein the coating layer is a hard candy layer.

6. An edible product according to any preceding claim, wherein the coating layer is substantially continuous.

7. An edible product according to any preceding claim, wherein the coating layer comprises less than about 10% by weight of water.

8. An edible product according to any preceding claim, wherein the coating layer makes up from about 3 to about 20% of the total weight of the edible product.

9. An edible product according to claim 8, wherein the coating layer makes up from about 7 to about 10% by weight of the total weight of the edible product.

10. An edible product according to any preceding claim, wherein the coating layer is from about 0.1 to about 2 mm thick.

11. An edible product according to claim 10, wherein the coating layer is from about 0.2 to about 1.0 mm thick.

12. An edible product according to any preceding claim, wherein the coating further comprises a sugar selected from the group consisting of isomalt, mannitol, and mixtures thereof.

13. An edible product according to any preceding claim which is a confectionery product or a sugar coated medicament.

14. An edible product according to claim 13, which is a hard candy.

15. An edible product according to any of claims 1 to 12, wherein the edible core comprises fruit pieces, dried fruit pieces, or breakfast cereal pieces.

16. An edible product according to any of claims 1 to 12, wherein the edible core comprises a cookie.

17. An edible product according to any preceding claim, wherein the coating layer is substantially transparent.

18. An edible product according to any preceding claim, wherein the moisture uptake of the product at 65% relative humidity and 20°C after 10 days is less than about 1 % by weight.

19. An edible product according to any preceding claim, wherein the moisture loss of the product at 10% relative humidity and 20°C after 10 days is less than about 1 % by weight.

20. A process for the production of an edible product according to any one of claims 1 to 19, comprising the steps of: providing an edible core; and enrobing the core with a sugar syrup comprising trehalose.

21. A process according to claim 20, wherein the step of enrobing is carried out with a sugar syrup at a temperature of from 20 to 140°C.

22. A process according to claim 20 or claim 21 , wherein the step of enrobing is carried out with the sugar syrup containing from 50 to 85% dissolved sugars.

23. A process according to any one of claims 20 to 22, wherein the step of enrobing is carried out with a syrup that is substantially free of sucrose.