Food or edible material: processes – compositions – and products – Processes – Molding – casting – or shaping
Reexamination Certificate
1998-04-06
2001-05-08
Nessler, Cynthia L. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Molding, casting, or shaping
C426S524000, C426S565000, C426S566000, C426S567000, C062S306000, C062S342000, C062S343000
Reexamination Certificate
active
06228412
ABSTRACT:
CROSS-REFERENCE TO RELATED PCT APPLICATION
This application is a national stage application of International Patent Application PCT/EP97/02593 filed May 12, 1997.
BACKGROUND OF THE INVENTION
The present invention relates to manufacture of frozen aerated products, particularly ice creams, and also to use of extrusion procedures.
A conventional process for manufacturing aerated frozen products, in particular ice cream, comprises the operations of blending, homogenizing, pasteurizing, freezing and hardening the mixture to be frozen. Aeration of the mixture or expansion is carried out during the freezing step in a proportion such that the volume increases by 70 to 120%. On leaving the freezer, the temperature of the aerated mass is typically −5 to −6° C. The mass is then hardened at −40 to −45° C. in a hardening chamber until the temperature of the product reaches −18° C. or lower at the core for bulk products or −30° C. for products extruded as bars.
An attempt has been made to reduce the temperature of the mass leaving the freezer for reasons of energy saving and with the object of improving the texture, for example in the direction of improved oiliness. Insurmountable problems have however been encountered with conventional equipment with the high viscosity of the ice cream mass at temperatures below −7 to −8° C. These problems have been partially resolved by using two freezers with a scraped surface in series, the first being a conventional one delivering aerated ice cream at approximately −7° C., and the second being specially designed to treat the highly viscous material to lower its temperature to approximately −10° C.
Within the same type of ideas, European Patent Application Publication No. 0 561 118 describes a three-step process for producing ice cream at a low temperature, down to −20° C., which is an exit temperature so that a hardening step may be entirely dispensed with for bulk products and considerably be shortened for extruded products. Further, in a first step, a so-called pre-expansion step, air is incorporated into the mixture to be frozen at a positive temperature. In a second step, the aerated mass is cooled in a scraped surface exchanger and leaves at approximately −6° C. During the third step, a screw device cools the mass to approximately −20° C.
U.S. Pat. No. 5,024,066 also discloses a two-step system. Pre-expansion takes place in the first step during which air is added to the mass to be frozen at a positive temperature. In the second step the aerated mass is cooled by means of an archimedean screw with a rough surface provided with scraping knives at its periphery, to a negative temperature sufficiently low to ensure a stable texture of the frozen mass, which enables the products to be stored directly in a cold chamber.
SUMMARY OF THE INVENTION
The object of the present invention is to carry out expansion and cooling operations on the mass in a single step in a single apparatus, which is easier to control and is less bulky than known devices, as well as to simplify the freezing process at a low temperature while deriving the previously mentioned advantages regarding energy and texture and it has been found surprisingly that it is possible to aerate and mix and cool a composition to be frozen in a single step with a mono-screw extrusion apparatus (an extrusion apparatus having only a single screw which extends longitudinally within a barrel for processing material, such as described further below by the drawing Figure description) so that, at a low temperature, a frozen aerated product having an improved and stable texture is extruded, when it would have been feared that the texture of the frozen composition would be damaged during treatment in a mono-screw extrusion apparatus.
The invention concerns a process for manufacturing aerated frozen products, wherein an unfrozen composition suitable for being aerated and frozen for preparing a frozen aerated composition is mixed, aerated, frozen and cooled to a temperature lower than or equal to −8° C. and is passed through a die, characterized in that the operations take place in a single step in a single mono-screw extrusion apparatus situated in a barrel provided with means for aeration and cooling.
DETAILED DESCRIPTION OF THE INVENTION
In order to put the process of the present invention into practice, there is prepared in a conventional manner a composition for ice cream, low-fat ice cream or sorbet, based, according to the recipe, on milk, skimmed milk, cream, concentrated milk, powdered milk or butter oil, to which are added sucrose, glucose, fruit dextrose, fruit pulp and stabilizing hydrocolloids such as, for example, carragheenates, alginates, carob gum, emulsifiers such as, for example, partial glycerides and flavourings. After intimately mixing the ingredients in the proportions dictated by the recipe, the mixture is pasteurized, cooled and then may optionally be homogenized, preferably hot, under stringent conditions enabling the mean size of the fat globules to be reduced to around 8-20 microns. After cooling and homogenizing at a low temperature, close to 0° C., the composition may be allowed to ripen for a certain length of time at that temperature. Homogenization and maturing are optional steps.
This composition, optionally homogenized and ripened, is introduced, preferably at approximately 2-7° C. into a mono-screw apparatus which is described below in greater detail, in which it is conveyed to an air injection zone where it is expanded to 0-150%, strongly cooled to −8 to −20° C., and then forced through a die.
Work in the mono-screw apparatus is carried out surprisingly without excessive shear, so that the increase in pressure does not exceed approximately 50 bar in the region of the die, and the screw may be revolved at 100 to 600 rpm. The emerging product is characterized by a mean ice crystal diameter of 10 to 30 microns, which is appreciably less than that which can be obtained with conventional freezers. The result is an improved texture in the sense of better oiliness and better creaminess.
Thus, the present invention also provides an apparatus for putting the process into practice, comprising an endless screw, placed in a barrel provided at one of its ends with an extrusion die and at the other end with means for feeding the composition to be frozen and, in an intermediate zone, means for feeding in air, the barrel being provided with a sleeve through which cooling fluids flow.
The endless screw may have successive segments where its form varies from one segment to another, from the point of view of the orientation of the threads and their pitch. The configuration of the screw is chosen so as to carry out operations for transporting, mixing, shearing and compressing the mass through the die and to encourage, optionally, the incorporation of gas so as to obtain good expansion. Zones can be provided for mixing, for example by mono-lobe or bi-lobe discs with a positive orientation, having a transporting effect or with a negative orientation having a return effect, or by a segment with an inverse screw pitch inducing a return.
The barrel is provided with means for cooling consisting of a jacket with, preferably, one self-contained cooling circuit per segment, with valves controlling the flow rate of cooling agent which enables the temperature of each segment to be regulated individually. The screw may also have an internal cooling circuit.
Air may be injected by means of flow meters through pipes at different regions of the barrel, preferably in the second half of its length, preferably from either side thereof. In this way, it is possible to achieve 0 to 150% and preferably 30 to 120% expansion.
The die may have a horizontal or vertical outlet. The geometry and dimensions of the die or, as the case may be, the diameter and length of the outlet pipe which may be associated therewith are designed to ensure a counter-pressure of the order of 4 to 50 bar and preferably 4 to 25 bar. The counter-pr
Fayard Gilles
Groux Michel John A.
Nessler Cynthia L.
Nestec S.A.
Vogt & O'Donnell, LLP
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