Food or edible material: processes – compositions – and products – Processes – Packaging or treatment of packaged product
Patent
1987-01-28
1988-05-31
Yeung, George
Food or edible material: processes, compositions, and products
Processes
Packaging or treatment of packaged product
44 33, 126263, 426113, A23L 310, F24J 100
Patent
active
047480351
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF THE INVENTION
This invention relates to a method for heating a food contained in a preserve can, such as a tin or a dish, by reaction of quicklime with water contained in an envelope or housing adjacent to that containing the food.
It has been found that overburnt lime is very sensitive to water and that the reactivity of said lime diminishes in course of time , this phenomenon being probably due to the absorption of a small amount of water, despite the measures which are taken for separating the two reagents (quicklime and water) until it is desired to cause them to react with each other.
In fact, even if the water is contained in an impervious plastic container and if a layer of microcrystalline wax is poured onto the surface of the lime layer, a reduction of the reactivity of the overburnt quicklime is observed, so that the duration of the reaction of the quicklime with water becomes too long. Therefore, the maximum temperature which can be reached in the food diminishes when time gradually becomes longer, in proportion to the degradation of the quicklime by the water, so that the time needed for reaching a suitable temperature for the consumption of the food becomes unduly long. This phenomenon is particularly apparent when the food is at a low initial temperature (0.degree. to 10.degree. C.).
It has now been found that it is possible, in a surprisingly simple manner, without using other reagents than water and quicklime, to avoid said drawbacks and to considerably improve the transmission of heat from the reaction mixture to the food, while avoiding projections of lime milk and/or heat losses by emission of water vapor.
According to the present invention, quicklime having a high or medium reactivity is added to overburnt quicklime in a proportion of 6 to 75% by weight of the total weight of used quicklime (quicklime having a high reactivity+quicklime having a low reactivity).
The proportion of quicklime having a high or medium reactivity is preferably of about 12 to 50% by weight with respect to the total weight of lime.
When less than about 6% by weight of quicklime having a high or medium reactivity with respect to the total weight of quicklime are used, no noticeable influence of the addition of this quicklime having a high or medium reactivity is found. When, on the other hand, more than about 75% by weight of quicklime having a high or medium reactivity are used, the reaction is too quick and heat losses such as water vapor emission and/or lime milk projections occur.
According to the present invention, for a standard preserve can containing 420 grams of food, about 17 to 100 grams of quicklime having a high reactivity are preferably used with respect to a total amount of quicklime (overburnt quicklime+quicklime having a high or medium reactivity) of 140 to 200 grams.
The terms "quicklime having a high or medium reactivity", as used herein, refer to a softly burnt quicklime, i.e. a lime burnt at a temperature comprised between 900.degree. and 1150.degree. C. This type of lime which is commonly manufactured and used is a very porous lime reacting quickly when contacted with water.
In the process according to this invention, the two types of quicklime are preferably used as grains of a size of about 2 to 5 mm. The grains of quicklime of one type may be mixed with grains of the other type. It is also possible to use two superimposed layers containing each a single type of quicklime. So, it is possible to use, for example, a layer of grains of quicklime having a high or medium reactivity on top of a layer of grains of overburnt quicklime or vice versa.
When quicklime having a high or medium reactivity is added, it has been surprisingly found that the amount of water reacted with the mixture of overburnt quicklime and of quicklime having a high or medium reactivity can be reduced from 0.75 part by weight to 0.4 part by weight of water for each part of quicklime. This has the advantage of diminishing the weight and volume of the used heating materials (reagents).
When a mixture of overb
REFERENCES:
patent: 2579405 (1951-12-01), Sukacev
patent: 4501259 (1985-02-01), Apellaniz
Tarahelm Limited
Yeung George
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