Food or edible material: processes – compositions – and products – Processes – Cooling – freezing – or treating cooled or frozen product,...
Reexamination Certificate
2001-01-05
2003-03-11
Yeung, George C. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Cooling, freezing, or treating cooled or frozen product,...
C062S057000, C426S417000, C426S443000
Reexamination Certificate
active
06531173
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the preparation of food products which comprise or include hydrogenated fat.
BACKGROUND OF THE INVENTION
Hydrogenated fats, for example hydrogenated rape seed, hydrogenated palm oil and hydrogenated sunflower seed, are commonly used in the food industry in the production of spreadable food products including table margarine, dairy and non-dairy spreads and peanut butter and in the production of shortenings.
Shortenings in particular are used in the bakery industry in the production of bread, cakes, biscuits, pastries and the like. For reasons of taste and texture including an ability to control crumb structure in the final product, shortenings are designed to possess a predetermined proportion of fat crystals dispensed in a continuous or substantially continuous oil phase, for example 15% to 20% fat crystals in solid shortenings and 8% to 12% fat crystals in pumpable shortenings.
There are well known problems associated with the production of such shortenings and other food products incorporating hydrogenated fats. In particular, the required fat crystalline structure may be difficult to achieve in general and in any event may take such a long time that it imposes undesirable delays and costs in the manufacturing processes overall.
For example, table margarine or peanut butter is commonly produced using what is known as “scraped surface technology”, in which a molten fat is brought in to contact with a cold surface, for example one cooled by mechanical refrigeration, where it crystallises and is scraped away so that more crystallisation can take place. There are various designs of scraped surface technology apparatus which usually share a common feature of a maximum cooling rate in the order of 400° C. to 600° C. per second. Applying such techniques to fats or to mixtures containing fats (such as typical peanut butter mixtures, for example) generally produces crystals of the fat having a particle size typically of 1 &mgr;m or more.
In addition, the solid fat phase in shortenings produced by scraped surface technology often continue to crystallise during storage, even when processing is followed by conditioning in cold storage before distribution. This means that shortenings used in baked products at different intervals after processing often contain different levels of solid fat and therefore have different functionality, giving rise to potential variations in the quality of the baked product.
Another common use for hydrogenated fats is as a stabiliser and to control texture in food products. Many products such as peanut butter contain an oil which is liquid at ambient temperature; there is a potential for phase separation to occur over time, which produces a layer of oil on the surface of the product and which therefore has the effect of lessening the “shelf life” of the product. This problem is usually addressed in commercial products by the addition of fat stabilisers composed of triglyceride or triglyceride/monoglyceride fat mixtures which have a crystalline structure at ambient temperatures; these additives dissolve in the oil phase when the product is hot and, on cooling, gradually crystallise in to a network which entraps the oil phase and thereby reduces the tendency towards phase separation. The presence of these crystals of fat and/or monoglycerides also increases the stiffness of the resulting mixture, which gives a set, or firm, product, and one which is less sensitive to handling or shearing, and having improved spreading properties. In the case of table margarines and dairy and non-dairy spreads, a similar process is designed to produce an aqueous phase dispersion in a network of crystals of fat and/or monoglycerides which provides good spreadability at room temperatures.
However, in all of these cases, the time required for a stable crystal network to build and for optimum firmness to be reached may take weeks, and the prolonged storage of a food product as an essential element of the manufacturing process is undesirable and costly to the food processing industry and leads to additional cost to the consumer.
The invention is concerned with an improved method for forming such food products which can generally overcome the difficulties described above with existing methods.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a method of forming a food product which includes therein a hydrogenated fat, the method comprising contacting a spray of the product in liquid form with a cryogen so as to cool the liquid product and effect a rapid conversion of the liquid product to a solid.
The main aim of the invention is to provide small crystals of liquid fat and a correspondingly large number of these crystals dispersed in a liquid phase of the fat structure.
Preferably, the rate of cooling of the food product in the method exceeds 1000° C. per second, more preferably exceeds 2000° C. per second and is advantageously at least 5000° C. per second or at least 10000° C. per second or higher up to 40000° C. or 50000° C. or more.
The spray of liquid fat is advantageously formed by atomisation, preferably by urging the liquid fat through an atomising nozzle in communication with an external source of gas, for example air or nitrogen, under pressure.
The cryogen is preferably down to a temperature of at least minus 75° C., for example 79.8° C. of carbon dioxide snow, or more preferably down to at least minus 185° C., for example minus 194° C. of liquid air or minus 196° C. of liquid nitrogen. Temperatures between minus 75° C. and minus 185° C. may usefully be employed by mixing a cryogen, for example liquid nitrogen, with air.
The liquid food product is preferably directed in to the cryogen by causing the spray thereof to contact a spray of cryogenic liquid. More preferably, the spray of liquid food product is directed downwardly in to the spray of liquid cryogen which may itself be preferably directed substantially horizontally or upwardly in to a counter-current spray of the liquid food product. This latter method is generally known as “spray crystallisation” and is described in our European Patent Specification No. 0 393 963.
It has been found that the method of the invention, by virtue of its rapid cooling of the liquid food product, produces a product with a crystalline structure of fat particles dispersed in an oil phase which, by variation of the amount of cryogen employed and hence the rate of cooling of the liquid fat droplets, can produce a product with a minimum crystal size and a maximum number of such crystals per unit mass of solid fat in the product.
It has been found that a control of the cooling rate can provide a much smaller crystal size and a corresponding greater number of crystals than can be produced using conventional methods in the food industry. Typically, the crystal size should be 0.5 &mgr;m or less, ideally 0.1 &mgr;m or less.
Because the invention produces such rapid crystallisation, no ordered crystal network is formed and therefore re-crystallised fats are typically shear stable. Also, the multiplicity of very small crystals so formed confers stable Theological properties on the product once it has been brought to ambient temperature. Scraped surface technology processes initiate crystallisation of fat, but the process may continue slowly for days or weeks. This is very significant as the invention can greatly reduce if not obviate the time a food product needs to be stored before it can be used. In preferred embodiments of the invention the product, which after cooling is in particulate form, is brought to ambient temperature and either introduced directly in to a mixture of other food ingredients or mechanically worked (by conventional means such as a pinworker, which produces an extruded plastic solid) and can immediately be introduced in to containers for sale or use, because the completion of crystallisation of the hydrogenated fat is so very rapid.
The invention has been found to be applicable to all hydrogenated fats including hydrogenated rape seed, hydrogenated s
Cohen Joshua L.
Pace Salvatore P.
The BOC Group plc
Yeung George C.
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