GB2362555A

GB2362555A - Amorphous sugar coatings

Info

Publication number: GB2362555A
Application number: GB0012938A
Authority: GB
Inventors: Geoffrey Royston O'sullivan
Original assignee: British Sugar PLC
Current assignee: British Sugar PLC
Priority date: 2000-05-26
Filing date: 2000-05-26
Publication date: 2001-11-28
Also published as: GB0012938D0; WO2001089313A1; AU5863301A

Abstract

Edible products comprise a core and a coating layer a major fraction of which is an amorphous sugar. The coating can have a different composition from the core, and is preferably less hygroscopic. The amorphous sugar is preferably weakly hygroscopic, and may be trehalose, isomalt, mannitol or mixtures thereof. The edible product is preferably food such as a boiled sweet, but it may be a pharmaceutical or animal feed stuff. The core may be caramel, fruit, cereals or ice cream. The coating layer may also contain colouring agents, citric or other edible acids, and flavouring agents such as menthol. The edible product is produced by enrobing the core with a sugar syrup of the coating layer. The sugar syrup is preferably free of sucrose.

Description

2362555 1 EDIBLE PRODUCTS The present invention relates to edible products

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 20 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 (a-D-g lucopyra nosyi-a-D-g 1 u copyra nos ide) is a naturally occurring disaccharide that is found in certain fungi and droughtresistant 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 2 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 polyof 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.

It is an object of the present invention to produce edible products having reduced 20 water pick-up and stickiness compared to amorphous sucrose-based products such as boiled sweets.

It is a further object of the present invention to provide processes for the production of edible products according to the present invention.

The present invention provides an edible product comprising a core and a coating layer having a composition different from that of the core, wherein the coating layer comprises a major fraction of an amorphous sugar.

It has been found that trehalose and other sugars can be coated onto edible cores, in particular boiled sweets, as an amorphous coating having an attractive appearance and also overcoming the problem of moisture pickup and stickiness of earlier hard confections.

3 Normally, the amorphous sugar coating layer is less hygroscopic than the core. Preferably, the amorphous coating is less hygroscopic than an equivalent pure amorphous sucrose layer having the same moisture content. That is to say, the amorphous layer shows less weight gain per unit area at 200C and 65% relative humidity after 24 hours than the core, or preferably than 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 the core alone, and preferably relative to pure amorphous sucrose 10 products.

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. 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 or cereals in the product over time and under varied temperature conditions. The edible core may comprise caramel or fruit pieces, for example for use in ice cream products, to minimise moisture migration on storage.

Preferably, the edible product is a confectionery product, or it may be a sugar coated medicament. Preferably, 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.

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.

4 Preferably, the amorphous sugar of the coating is selected from the group consisting of trehalose, isomalt, mannitol, and mixtures thereof. More preferably, the amorphous sugar comprises trehalose, still more preferably the amorphous sugar comprises a major fraction (typically at least 60% based on the total dry weight of sugars in the coating, more preferably at least 75%) of trehalose, and most preferably the amorphous sugar consists essentially of trehalose. 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, 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 comprises a major fraction of the amorphous sugar. Preferably it comprises more than 50% of the sugar on a dry solids weight basis, more preferably at least 75% of the sugar on a dry solids weight basis. Preferably, the coating layer comprises less than 10% of water by weight.

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.

Preferably, the coating layer makes up from 3 to 20% by weight of the edible product, more preferably from 7 to 10% thereof. Preferably, the thickness of the coating is from 0.1 to 2mm, more preferably from 0.2 to lmm.

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.

Preferably, the coating layer is substantially continuous. Preferably, the coating 5 layer is substantially transparent and preferably the coating layer is glassy.

The coating layers in the edible products according to the present invention exhibit significantly reduced water-pick up under ambient conditions of temperature and humidity than prior art sucrose based boiled sweets. This enables the products according to the present invention to be stored in the open in normal atmospheric conditions without bonding together into a sticky mass. Preferably, the products according to the invention exhibit a weight gain of less than 1 % on storage at 65% relative humidity and 200C for 10 days, preferably less than 0.5%, and most preferably less than 0.25% The present invention also provides a process for the production of an edible product comprising the steps of: providing an edible core; and enrobing the core in a coating layer comprising a major fraction of an amorphous sugar.

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 sugar 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 200C to 14WC, more preferably from 1OWC to 1200C.

After enrobing or coating, the amorphous coating 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 500C until dry; (3) drying in conventional cooling tunnels modified to 6 provide air at 45 to 1 OOOC and 0 to 14% relative humidity for 30 to 60 minutes. In any case, the temperature of the coating preferably does not exceed 1000C, more preferably it does not exceed 60'lC, in the drying step. Depending of the drying method, the drying step may be followed by a cooling step before packaging the 5 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 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 aciduiant 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 also preferably substantially free of sucrose.

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.

In pharmaceutical applications, the reduced solubility and improved stability at low pH of trehalose compared to sucrose may 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.

Specific embodiments of the present invention will now be described further, by way of example, with reference to the accompanying drawing, which shows 7 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.

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 1150C 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 450C 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 200C for 7 days, and weighed and inspected at intervals. The weight measurements are shown in the attached drawing. 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 200C, the uncoated sweet underwent complete deliquescence within two days. In contrast, the coated product had taken up only 0.5% w1w of moisture after two days and remained dry to the touch.

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

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Claims

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

2. An edible product according to claim 1 which is a confectionery product or a sugar coated medicament.

3. An edible product according to claim 1, which is a boiled sweet.

4. An edible product according to any preceding claim, wherein the amorphous sugar is selected from the group consisting of trehalose, isomalt, mannitol, and mixtures thereof.

5. An edible product according to claim 4, wherein the amorphous sugar comprises trehalose.

6. An edible product according to claim 5, wherein the amorphous sugar 20 consists essentially of trehalose.

7. An edible product according to any preceding claim, wherein the amorphous sugar makes up at least 50% by weight of the coating layer on a dry solids basis.

8. An edible product according to claim 7, wherein the amorphous sugar makes up at least 75% by weight of the coating layer on a dry solids basis.

9. An edible product according to any preceding claim, wherein the coating 30 comprises less than 10% by weight of water.

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

9

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

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

13. An edible product according to claim 12, wherein the coating layer is from 0.2 to 1.0 mm thick.

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

15. An edible product according to any preceding claim, wherein the coating 15 layer consists essentially of the amorphous sugar, flavourings and colourings.

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

17. A process for the production of an edible product comprising the steps of:

providing an edible core; and enrobing the core with a coating layer comprising a major fraction of a substantially amorphous sugar.

18. A process according to claim 17, wherein the step of enrobing is carried out with a sugar syrup at a temperature of from 20 to 14TC.

19. A process according to claim 17 or claim 18, wherein the step of enrobing is carried out with the sugar syrup containing from 50 to 85% dissolved sugars.

20. A process according to any one of claims 17 to 19, wherein the step of enrobing is carried out with a syrup that is substantially free of sucrose.

21. A process according to any one of claims 17 to 20, which is adapted to produce an edible product according to any one of claims 1 to 16.