PROCESS FOR MANUFACTURE OF COATED FROZEN CONFECTION

Abstract

The invention relates to a process for the manufacture of a coated frozen confection, the process comprising the steps of (a) manufacturing a frozen confection, followed by; (b) imparting thermal energy to the surface of the frozen confection, sufficient to cause at least partial melting of the surface of the frozen confection, followed by; (c) allowing the surface of the frozen confection to refreeze, followed by; (d) coating the frozen confection in a liquid coating, which subsequently solidifies to provide a solid coating.

Claims

1. A process for the manufacture of a coated frozen confection, the process comprising the steps of a) manufacturing a frozen confection, followed by; b) imparting thermal energy to the surface of the frozen confection, sufficient to cause at least partial melting of the surface of the frozen confection, followed by; c) allowing the surface of the frozen confection to refreeze, followed by; d) coating the frozen confection in a liquid coating, which subsequently solidifies to provide a solid coating; characterised in that the thermal energy imparted in step b) is imparted in a non-contact manner.

2. A process according to claim 1 wherein, the amount of thermal energy imparted to the surface of the frozen confection is from 1 to 500 J/cm.sup.2, more preferably from 2 to 400 J/cm.sup.2, most preferably from 5 to 300 J/cm.sup.2.

3. A process according to claim 1, wherein the thermal energy is evenly applied over the surface of the frozen confection in step (b).

4. A process according to claim 1, wherein the frozen confection is not contained within a mould during step (b).

5. A process according to claim 1, wherein the thermal energy is imparted by convective means or by radiative means.

6. A process according to claim 1 wherein the frozen confection is at a core temperature of from −30° C. to −5° C. immediately prior to imparting thermal energy in step (b).

7. A process according to claim 1, wherein the surface of the frozen confection prior to step (b) has troughs with a volume of 1.5 to 550 mm.sup.3 and surface openings having a minimum diameter of from 0.05 to 7.5 mm.

8. A process according to claim 1, wherein the frozen confection is manufactured by extrusion and cutting the extruded product.

9. A process according to claim 8, wherein the cut product is placed onto a freezing surface at a temperature of −15° C. or below, more preferably −25° C. or below, most preferably −30° C. or below.

10. A process according to claim 9, wherein the freezing surface is made of a metal, such as stainless steel or aluminium.

11. A process according to claim 10, wherein the freezing surface is a stainless steel platform, which is preferably arranged to carry the frozen confectionery through a freezer, preferably a blast freezer.

12. A process according to claim 1, wherein the coating is chocolate.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0058] FIG. 1A is a photograph of an ice cream product with an apparently smooth surface prior to being coated.

[0059] FIG. 1B is a photograph of the ice cream product of FIG. 1A after it has been coated in chocolate.

[0060] FIG. 2A is a photograph of an ice cream product prior to being coated and has an induced series of troughs.

[0061] FIG. 2B is a photograph of the ice cream product of FIG. 2A after it has been coated in chocolate.

[0062] FIG. 3A is a photograph of an ice cream product prior to being coated and has an induced series of troughs and has been thermally treated.

[0063] FIG. 3B is a photograph of the ice cream product of FIG. 3A after it has been coated in chocolate.

[0064] FIG. 4A is a photograph of an ice cream product prior to being coated and has an induced series of troughs and has been thermally treated.

[0065] FIG. 4B is a photograph of the ice cream product of FIG. 3A after it has been coated in chocolate.

EXAMPLES

Example 1

Radiative Heat

[0066] Smooth Surface

[0067] An ice cream of a conventional formula was carefully produced by extrusion in known manner and cut into frozen confection portions of such a size and dimension as a commercially available consumer ice cream product. An image of the produced ice cream is shown in FIG. 1A.

[0068] The produced ice cream had an essentially smooth surface with no observable troughs in the surface. The ice cream was then subsequently dipped into a molten chocolate coating at 46° C. and removed to allow the coating to crystallise as its heat was drawn into the body of the frozen ice cream.

[0069] An image of the coated ice cream is shown in FIG. 1B. The resulting coated ice cream produced a largely smooth chocolate surface. However, even when the production of the ice cream core is carefully controlled, bubbles may still form as evidenced by FIG. 1B in which a bubble has formed and caused an imperfection on the coating as can be observed on upper part of the product on the left hand side.

[0070] Rough Surface

[0071] To introduce the effect of roughness to the surface in a controlled and repeatable manner, approximately 700 holes were introduced into the surface of the frozen confectionery each with a diameter of about 0.3mm and depths of up to 5.5 mm, by applying a wire brush to the surface of the ice cream. An image of the produced ice cream is shown in FIG. 2A.

[0072] The frozen confectioneries were then dipped in liquid nitrogen and left to warm at room temperature to allow any liquid nitrogen that entered the holes to vaporise. This was to simulate the nitrogen atmospheric conditions the frozen confectioneries would typically be subjected to during manufacture, and to ensure that nitrogen gas had filled the troughs.

[0073] The frozen confectioneries were then dipped into a chocolate coating at 46° C. and withdrawn, allowing the chocolate coating to crystallise as its heat was drawn into the body of the frozen ice cream. Bubbles could be seen to form in the liquid chocolate coating as it began to cool before solidifying, giving the appearance of a low quality product. An image of the coated ice cream is shown in FIG. 2B.

[0074] As the liquid chocolate crystallised, numerous bubbles were seen to appear in the coating of chocolate, giving the appearance of a low quality product.

[0075] Thermally Treated Surface—Radiative Heat

[0076] To introduce the effect of roughness to the surface in a controlled and repeatable manner, approximately 700 holes were again introduced into the surface of the frozen confectionery each with a diameter of about 0.3 mm and depths of up to 5.5 mm, by applying a wire brush to the surface of the ice cream.

[0077] The surface that was roughened was then heat treated by suspending the roughened surface 5 cm above a hot plate at a temperature of 250° C. for 108 seconds. An image of the thermally treated ice cream is shown in FIG. 3A.

[0078] The area of the roughened surface was 38 cm.sup.2. Assuming a thermal conductivity of air=0.024 W/m/° C. at a rate given by k.Math.A.Math.(T.sub.1−T.sub.2)/d, gave thermal transfer rate of 0.5016 W. Carried out over 108 seconds translates into 54.2 J. This is therefore 1.43 J/cm2 applied to the roughened face.

[0079] The thermally treated ice cream was then dipped in liquid nitrogen and left to warm at room temperature.

[0080] The ice cream was then dipped into a chocolate coating at 46° C. and withdrawn, allowing the chocolate coating to crystallise as its heat was drawn into the body of the frozen ice cream. No bubbles could be seen to form in the liquid chocolate coating as it began to cool before solidifying. An image of the coated ice cream is shown in FIG. 3B.

[0081] It can thus be seen that the introduction of troughs representing surface roughness cause bubbles to appear on the surface of the ice creams when it is coated in chocolate. Furthermore, thermally treating the ice creams with a controlled quantity of heat prior to being coated in chocolate prevents the bubbles from forming.

Example 2

Conductive Heat

[0082] Thermally Treated Surface—Conductive Heat

[0083] To introduce the effect of roughness to the surface in a controlled and repeatable manner, approximately 700 holes were again introduced into the surface of a frozen confectionery each with a diameter of about 0.3 mm and depths of up to 5.5 mm, by applying a wire brush to the surface of the ice cream.

[0084] The surface that was roughened was then heat treated by contacting it with a stainless steel block at 20° C. which was held on the product surface for 5 seconds to give a thermal transfer of 52.5 J/cm.sup.2. An image of the thermally treated ice cream is shown in FIG. 4A.

[0085] The thermally treated ice cream was then dipped in liquid nitrogen and left to warm at room temperature.

[0086] The ice cream was then dipped into a chocolate coating at 46° C. and withdrawn, allowing the chocolate coating to crystallise as its heat was drawn into the body of the frozen ice cream. No bubbles could be seen to form in the liquid chocolate coating as it began to cool before solidifying. An image of the coated ice cream is shown in FIG. 4B.

[0087] It can thus again be seen that this alternative approach of thermally treating the ice creams with a controlled quantity of heat prior to being coated in chocolate again prevents the bubbles from forming.

Example 3

Generation of Bubbles

[0088] In order to more accurately understand the nature of the troughs which give rise to the formation of bubbles, experiments were carried out. This involved intentionally inducing troughs (referred to as “recesses”) of various dimensions to understand the conditions under which bubbles are formed.

[0089] Stick-based ice cream blanks (i.e. uncoated frozen confections) were provided. They were removed from a freezer at a temperature of −25° C. and punching tools such as pins or nails were used to created cylindrical recesses of varying widths (Diameters of 0.6, 1, 2, 3.7, 5, 6.8, 8.3, and 12.8 mm) and of varying depths (Depths of 1, 2, 3, 4, 5, 10, 15 mm). Volumes of the recesses in mm.sup.3 were calculated using the formula: Pi×(radius).sup.2×(height) and are shown in Table 1. For each volume, recesses were created in triplicate.

TABLE-US-00001 TABLE 1 Volumes of recesses for a given depth and diameter. Diameter of recess (mm) 0.6 1 2 3.7 5 6.8 8.3 12.8 Depth of 1 0.28 0.79 3.14 10.75 No recesses with these recess (mm) 2 0.57 1.57 6.28 21.50 dimensions were created 3 0.85 2.36 9.42 32.26 4 1.13 3.14 12.57 43.01 5 1.41 3.93 15.71 53.76 98.17 181.58 270.53 643.40 10 2.83 7.85 31.42 107.52 196.35 363.17 541.06 1286.80 15 4.24 11.78 47.12 161.28 294.52 544.75 811.59 1930.19

[0090] Following the creation of the recesses, the products were dipped in liquid nitrogen for 7 seconds, then left at ambient temperature for approximately 20 seconds after which they were dipped into a chocolate coating at 3 different temperatures (36° C., 46° C., and 56° C.)

[0091] Each recess volume and opening diameter was assessed for its propensity to form a bubble. They were given the following scores: [0092] 0%: No bubble formed [0093] 33%: 1 of the triplicate recesses formed a bubble [0094] 66%: 2 of the triplicate recesses formed a bubble [0095] 100%: All 3 of the triplicate recesses formed a bubble

[0096] The scores are shown in Table 2 from which is can be seen that recesses having a volume of from 1.5 to 550 mm.sup.3 and an opening of diameter from 0.05 to 7.5 mm consistently produced bubbles in the coating.

TABLE-US-00002 TABLE 2 Scores showing propensity of recesses of a given volume and openings having a given diameter to form bubbles in coatings at various temperatures. Temperature Recess depth Diameter of recess (mm) of coating (mm) 0.6 1 2 3.7 5 6.8 8.3 12.8 36° C. 1  0%  0%  33%  0% No recesses with these 2  0%  0%  33%  67% dimensions were created 3  0%  0%  33%  33% 4  0%  0%  33%  33% 5  33%  0%  67%  67% 10  67%  67% 100% 100% 15 100%  33% 100% 100% 46° C. 1  0%  33%  33%  0% No recesses with these 2  33%  33%  33%  33% dimensions were created 3  33%  0%  0%  0% 4  0%  67%  33%  33% 5  0%  67% 100%  33% 10  33%  67% 100% 100% 15 100% 100% 100%  67% 56° C. 1  0%  0%  0%  67% No recesses with these 2  33%  0%  33%  67% dimensions were created 3  33%  33% 100% 100% 4  0%  67%  33% 100% 5  67%  67% 100% 100% 100%  0% 0% 0% 10  67% 100% 100% 100% 100% 67% 0% 0% 15 100% 100% 100% 100% 100% 67% 0% 0%