Food or edible material: processes – compositions – and products – Surface coated – fluid encapsulated – laminated solid... – Frozen material
Patent
1999-06-18
2000-11-21
Bhat, Nina
Food or edible material: processes, compositions, and products
Surface coated, fluid encapsulated, laminated solid...
Frozen material
426241, 426243, 426602, 426524, 516 21, A23L 336, B01F 1700
Patent
active
061499544
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an edible water-in-oil micro-emulsion for thawing of a food product which is subjected to microwave energy and the method of use of such an edible water-in-oil micro-emulsion for thawing. The invention also relates to a frozen food product comprising an edible water-in-oil micro-emulsion effective for enhancing thawing of the food product, and to the process of providing such a frozen food product.
BACKGROUND OF THE INVENTION
For most applications frozen food needs to be brought to the melting temperature before further processing, such as cutting, recipe formulation or cooking can take place. Thawing of frozen food in the household or on an industrial scale is traditionally done by leaving the food material (e.g. at -20 to -30.degree. C.) for a period to thaw in at least ambient temperature. In a factory environment blocks of frozen food e.g. raw fish, meat, poultry, vegetables at -20 to -30.degree. C., are conventionally left in thawing cells wherein the energy is transmitted to the product by convection or conduction.
An alternative to these conventional thawing methods is to thaw the frozen product by microwave energy. The frozen product is placed in a special applicator and subjected to the application of short microwave pulses. The use of pulsed microwave power is dictated by the very low values of the thermal diffusivity of the frozen products and the requirement of long equilibrium times after each pulse in order to avoid excessive heating of parts of the food products. Depending on the size and nature of the frozen product, the processing time when subjected to microwave energy at 2.45 GHz generally ranges from 30 min. to a couple of hours for a 500 to 5000 grams block.
The above discussed thawing methods however suffer from serious drawbacks in that they are relatively slow and that they do not provide a uniform thawing of the food product.
SUMMARY OF THE INVENTION
It has surprisingly been found that, by treating a food product in accordance with the invention, the food product may be rapidly and uniformly thawed.
Accordingly, the present invention provides an edible water-in-oil micro-emulsion for thawing of a food product. The water-in-oil micro-emulsion when at a temperature below 0.degree. C. comprises water in super cooled a state which, when subjected to microwave energy at a temperature below 0.degree. C., acts as a microwave energy absorber.
According to the present invention it has been found that the low thermal diffusivity can be compensated by direct deposition of microwave energy everywhere in the frozen product. The invention may allow a uniform heating patent, and the application of a continuous full power microwave energy is then possible, and permits rapid heating without any need for equilibrium times after microwave application. For example, the thawing time for a conventional 1000 grams block of poultry is about 30 min while a similar block treated according to the invention is thawed in about 10 min.
Furthermore, the invention aims to provide an edible micro-emulsion having the above described characteristics while being "neutral" in terms of induced taste and release of flavour.
In the present context a micro-emulsion is a substantially thermodynamically stable dispersion of at least two immiscible liquids (phases) containing an appropriate amount of surface active agents (surfactants and co-surfactants). When put together, the two immiscible liquids separate rapidly. The addition of surfactants in right amounts, and if necessary also co-surfactants, would lead to the formation of interfacial layers between the two phases, thus lowering the interfacial tension between the two phases down to about zero, which is the condition required for coexistence at equilibrium of the two phases. The dispersed phase is characterised by a droplet size in the range of 0.01 to 0.5 .mu.m.
The micro-emulsion according to the invention is a water-in-oil micro-emulsion i.e. dispersion of aqueous droplets in an oil continuous phase. It compr
REFERENCES:
patent: 5043173 (1991-08-01), Steinke et al.
patent: 5045337 (1991-09-01), El-Nokaly et al.
Patent Abstracts of Japan, vol. 012, No. 275 (C-516), Jul. 29, 1988 and JP 63056259 A (Asahi Denka Kogyo KK), Mar. 10, 1988.
Bhat Nina
Nestec S.A.
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