Food or edible material: processes – compositions – and products – Processes – Heat treatment of food material by contact with glyceridic...
Reexamination Certificate
2002-03-19
2004-02-10
Yeung, George C. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Heat treatment of food material by contact with glyceridic...
C099S407000, C099S408000, C426S439000
Reexamination Certificate
active
06689408
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention concerns a method for deep-frying products to be deep-fried and a device for carrying out this method.
In conventionally designed immersion fryers a relatively few products to be deep-fried are fried in a relatively large amount of hot fat.
The quality features of products that have been deep-fried are a fine crust, a soft hot inside and a low fat content which, however, must not be so low as to reduce the typical fried taste.
In traditional immersion fryers, the exceptionally low thermal conductivity of the fat requires a large amount of fat to act as a heat accumulator so that, once the products to be deep-fried are placed in the fat, the drop in temperature in the frying zone is limited to such an extent that the crust formation prevents the products to be deep-fried from being fully soaked with fat as quickly as possible. The large amount of fat in the immersion fryer must be heated all day long because of the long heating-up time. What is more, around the heating elements temperatures of up to 300° C. predominate, which means that the thermal gradient is 130° C. at a target fat temperature of 170° C. This partial overheating and the thermal permanent load of the fat contribute to a considerable extent to a reduction in the quality of the fat.
In the system of a conventionally designed immersion fryer (standing liquid, heating by means of an enclosed heating coil or via the external walls) during deep-frying the drop in temperature in the deep-frying zone is intensified when the quantity of fat is reduced, since the cooling effect resulting from the introduction of products to be deep-fried is not offset by additional heating owing to the extremely slow thermal convection in the medium. An example of this is standard household fryers, which always produce deep-fried products of inferior quality.
That is why, in system gastronomy, the method used is to keep on increasing the quantity of fat and hence the storage of heat in the immersion fryer, resulting in a products to be deep-fried-to-fat ratio of currently up to 1:29, which corresponds to two baskets containing 680 grams of chips in 40 liters of fat; this ratio may even go up to 1:58, since only one basket is often used. But here too, because of the slow convection of heat from the heating surfaces to the deep-frying zone, the added effect is limited and the deep-frying quality can be improved further.
On the other hand, reducing the amount of fat is desirable since this has a number of advantages during deep-frying, chips (referred to in the U.S. as french fries, but referred, in this application by the British term “chips”) absorb approximately 5% of their original weight in deep-frying fat. This fat is taken out of the system and must be replaced by fresh fat in order to maintain the overall quantity of fat. In conventionally designed immersion fryers this does in fact improve the quality of the fat for a short time, but the harmful substances that are released accumulate over time, with the result that the quality of the fat continues to fall until the limiting values are exceeded after about 20 to 30 hours of operation and the entire contents of the fryer have to be discarded. The most important harmful substances are total polar materials and polymers. They arise out of the degraded products of the products that have been deep-fried, and out of chemically transformed fat components (see above: thermal permanent load and partial overheating). After approximately 4 to 5 operating hours, the quality of the products that have been deep-fried diminishes with the rise in the amount of harmful substances that are released, hence apace with the progressive worsening of the quality of the fat, since the harmful substances are absorbed by the products to be deep-fried. The refreshing effect brought about by replacing the fat that has been removed does not last and cannot ultimately prevent the quality of the fat from falling to the legally prescribed point at which the fat must be renewed (24% for total polar materials, 12% for polymer components). By reducing the amount of fat in proportion to the amount of products to be deep-fried, the refreshing effect brought about by replacing the fat that has been absorbed increases proportionally (since the quantity of fat that has been removed and needs to be replaced remains constant in relation to the quantity of the products to be deep-fried, while the amount of fat that needs to be refreshed is reduced) until finally the harmful substances no longer accumulate beyond the limiting values, but settle around a constant value which gets smaller as the products to be deep-fried-to-fat ratio gets lower.
With such an effective refreshing method there is no longer any old fat that needs to be discarded and so a quality of fat can be achieved that is consistently good, but, using the state-of-the-art immersion frying method, adequate convection of heat to the frying zone to produce quality frying cannot be achieved. Because the temperature is too low and cannot rise, so much fat penetrates the products to be deep-fried before the crust is formed that the quality of the products to be deep-fried drops massively (in this case not through the accumulation of harmful substances but as a result of not achieving the aforementioned quality features).
Methods and devices for deep-frying products to be deep-fried in hot fat are also known, in which the fat is pumped into a cycle in which it is heated up, brought into contact with the products to be deep-fried and filtered. In this case, a very large quantity of hot fat is always brought into contact with a relatively small quantity of goods to be deep-fried during the deep-frying process. The disadvantage of this is that, for example, the large amount of fat cannot be heated up quickly for individual frying processes. As a result, the fat must be kept at a constant operating temperature of between 170° C. and 190° C. and it is similarly exposed to a damaging permanent load. Nor can a refreshing effect like the one described above be achieved. What is more, the state-of-the-art method is very cost intensive and also harmful to the environment, since a very large quantity of fresh fat is always needed to deep-fry a relatively small amount of products to be deep-fried. The advantages of this cycle frying method over the immersion frying method relate only to the temperature distribution in the frying zone.
According to the state of the art it is therefore impossible to produce deep-fried products of a qualitatively high standard by capitalizing on the advantages of a reduced quantity of fat.
SUMMARY OF THE INVENTION
Proceeding on the basis of the existing state of the art, this invention is based on the problem of coming up with a method for deep-frying products to be deep-fried and a device for carrying out this method which, by minimising the quantity of fat used, guarantees the consistent quality of the fat, avoids the emergence of old fat that has to be disposed of and limits the use of fresh fat for the replacement of fat that is discharged together with the products that have been deep-fried. At the same time, this method generates sufficiently high temperatures in the deep-frying zone, which can be maintained during the deep-frying process, in order to achieve the quality of deep-fried products that meets the requirements of collective and individual gastronomy, to improve this quality even further and to maintain it at a constantly high level for an unlimited period of time. In addition, the thermal permanent load and partial overheating of the fat must be avoided so as to limit the build-up of harmful substances.
By keeping the quantity of fat circulating in a circuit or cycle as small as possible, the quantity of fat circulating in the fat cycle is always sufficient not to break the cycle. The small amount of circulating fat allows extremely short heating-up times, with the result that the fat can be heated up for each deep-frying process according to requirements. Constantly keeping a large quan
Nockermann Bernd
Nockermann Martin
Nockermann Otto
Nockemann Bernd
Nockermann Bernd
Nockermann Martin
Sonnenschein Nath & Rosenthal
Yeung George C.
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