Food or edible material: processes – compositions – and products – Products per se – or processes of preparing or treating... – Foam or foamable type
Reexamination Certificate
1999-07-06
2002-12-24
Bhat, Nina (Department: 1761)
Food or edible material: processes, compositions, and products
Products per se, or processes of preparing or treating...
Foam or foamable type
C426S516000, C426S519000
Reexamination Certificate
active
06497913
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to a method of preparation of an aerated frozen product such as ice cream, wherein at least part of the aerated frozen product premix is subjected to an ultra high pressure treatment. The invention also relates to an aerated frozen product obtained according to this process.
BACKGROUND TO THE INVENTION
Ultra high pressure (UHP) is a known method for killing spores and has been suggested as a suitable route to food product pasteurisation. In Japan a range of pressure de-contaminated products such as jellies, preserves, purees and sauces have been launched on the market (Byrne, M. (1993) Food Engineering International, 34-38).
Furthermore isolated, native proteins have been subjected to UHP. These proteins are in their native form, they have not been treated chemically or thermally before the pressure treatment by methods which significantly modify their protein structure (van Camp, J; Huyghebaert, A (1995) Food Chemistry 54(4) 357-364; Okamoto, M; Kawamura, Y; Hayashi, R; (1990) Agric Biol Chem 54(1) 183-189). It is generally believed that there would be no advantage in subjecting proteins which have already been substantially denatured by for example an initial heat-treatment prior to UHP.
DE 42 26 255 discloses the treatment of cream with ultra high pressure in order to crystallise the fat.
It has now been discovered that the presence of a fine microstructure is critical to produce the correct texture and quality of ice cream. Organoleptic evaluation of ice cream done by the applicant of the present invention has shown that small air cells and ice crystals are associated with increased creaminess and reduced iciness, which are recognized parameters for good quality ice cream. For example, for a given ice cream formulation, a reduction in gas cell and/or ice crystal size will enhance creamy texture (and reduce ice crystal perception, nevertheless the sensory attributes are not directly influenced by the de-emulsified fat level. However, the ice cream microstructure produced in a scraped surface heat exchanger (freezer) has been found to be unstable and both ice and air structure coarsen significantly in the time taken to harden the product to typical storage temperatures of −25° C. Therefore, an important step to achieve small gas cells in ice cream is to stabilize gas cells during hardening.
To retain the desired microstructure, it has now been found that it is necessary to generate a partial network of fat aggregates adsorbed onto the air interface to provide a steric barrier to gas cell coalescence. To generate this fat network, a proportion of the oil droplets need to partially coalesce as a consequence of the shear regime encountered within the ice cream freezer. It is known that the collision efficiency (the probability of two colliding droplets remaining permanently in contact) can be significantly affected by the initial droplet size and the protein surface coverage. The collision efficiency decreases as the droplet size decreases. However, small molecule surfactants can displace protein at the oil:water interface and allow a higher collision efficiency at a given droplet size.
In the processing of ice cream, an homogenization step is used to generate small oil droplets, preferably with a monomodal size distribution to allow the controlled fat destabilization under shear. For an ice cream premix, the average droplet size, d[3,2], upon homogenization is typically 0.6-1.0 &mgr;m. Numerous process and product variables affect homogenization efficiency. Those which have been found to have the largest effect on the final droplet size distribution are the dispersed phase volume, the type and level of surfactant used and, in particular, the pressure applied during homogenization. It has now been found that by using an homogeniser operating at higher pressures (ca. 2000 bar) than those conventionally used (ca. 150 bar), it is possible to generate smaller oil droplet sizes (ca. 0.3&mgr;m) in an ice cream premix.
Generation of significantly smaller, and therefore a higher number of, oil droplets can allow stabilization of a larger air:water interface, leading to smaller discrete gas cells which in turn alter the organoleptic quality of the ice cream. However, it has now been discovered that very small oil droplets will give inherently stable ice cream mixes which will not generate the desired microstructure unless the desired level of fat partial coalescence occurs. To achieve this, it is necessary to either increase the collisional force between the droplets or reduce the steric barrier to coalescence. This is achieved by either optimizing the applied shear stress during processing or by manipulating the interfacial composition by the appropriate selection of emulsifiers.
It has also been discovered that the sensory properties of ice cream is dependent on the size of the fat droplets. For a given air cell size, the ice cream with the smallest fat droplets scores best on creaminess when blind tested by a trained panel.
Definitions
Emulsifiers
Emulsifiers are defined as in Arbuckle, W. S., Ice Cream, 4th Edition, AVI publishing, 1986, ch 6 p92-94.
Stabilizers
Stabilizers are defined as in Arbuckle, W. S., Ice Cream, 4th Edition, AVI Publishing, 1986, ch 6, p84-92. They can for example be locust bean gum, carrageenan, guar gum, gelatin, carboxy methyl cellulose gum, pectin, algin products and mixtures thereof.
Frozen Aerated Dessert
A definition of a frozen aerated dessert can be found it Arbuckle, W. S., Ice Cream, 4th Edition, AVI Publishing, 1986, ch 1, p1-3. Preferably, a frozen areated dessert accodring to the invention is a milk or fruit based frozen aerated confection such as ice cream. An ice cream is a frozen food made by freezing a pasteurized mix with agitation to incorporate air. It typically contains ice, air, fat and a matrix phase and preferably;
milk/dairy fat 3 to 15% (w/w)
milk solids non fat 2 to 15% (w/w)
sugar and other sweeteners 0.01 to 35% (w/w)
flavours 0 to 5% (w/w)
eggs 0 to 20% (w/w)
water 30 to 85% (w/w)
Overrun:
Overrun is defined as in Ice Cream—W. S. Arbuckle—Avi Publishing—1972—page 194.
Destabilising Emulsifier
Destabilising emulsifier means any emulsifier which gives, at a level of 0.3%, a level of extracted fat of at least 25% in an ice cream premix containing 12% butter oil, 13% skim milk powder and 15% sucrose as described in on figure 4 in ‘The stability of aerated milk protein emulsions in the presence of small molecule surfactants’ 1997—Journal of Dairy science 80:2631:2638.
Examples of such destabilising emulsifiers are unsaturated monoglyceride, polyglycerol esters, sorbitan esters, stearoyl lactylate, lactic acid esters, citric acid esters, acetyllated monoglyceride, diacetyl tartaric acid esters, polyoxyethylene sorbitan esters, lecithin and egg yolk.
Methods
Ice Cream Premix Production
In a jacketed 500 liter mix tank, water is added at 85° C., then milk powder, sugar, stabilizers, butteroil with emulsifier dissolved are added and mixed with high shear mixer and heated to maintain a temperature of 65° C. for standard production and 55° C. for production according to the invention:
Standard production: the premix is heated with plate heat exchanger to 83° C., homogenize with Crepaco single stage valve homogeniser at 140 bar. After holding at 83° C. for 15 seconds the mix was cooled with a plate heat exchanger to 5° C. and held at this temperature for at least two hours prior to freezing.
Invention: the premix was heated with a plate heat exchanger to 83° C. and held at this temperature for 15 seconds to pasteurize the mix. The mix was tempered at 55° C. (+/−5° C.) in a holding tank prior to homogenization and collected after a single pass through the homogeniser (Nanojet Impinging Jet, ref: Verstallen, A., Apparatus for homogenizing essentially immiscible liquids for forming an emulsion described in U.S. Pat. No. 5,366,287) at an input pressure of 1600 bar (+/−50 bar). During homogenization there is a temperature rise of 2-2.5° C./100 bar. Imme
Gray Sarah Jane
Turan Susan
Bhat Nina
Good Humor - Breyers Ice Cream, division of Conopco, Inc.
McGowan, Jr. Gerard J.
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