Food or edible material: processes – compositions – and products – Processes – Cooling – freezing – or treating cooled or frozen product,...
Reexamination Certificate
2000-03-09
2001-05-22
Yeung, George C. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Cooling, freezing, or treating cooled or frozen product,...
C062S063000, C062S374000, C062S380000
Reexamination Certificate
active
06235332
ABSTRACT:
TECHNICAL FIELD
The invention relates to an improved method for food freezing of delicate items of food in a strongly cooled flow of air through a freezing tunnel on board ships and on land in the processing of delicate products. More particularly, the present invention relates to a method for freezing delicate items of food in a freezing tunnel comprising a freezing tunnel having means for providing a strongly cooled flow of air to act as a freezing agent, at least two or more endless conveyor belts supported therein, a movable feeding conveyor and a transfer conveyor, where said items of food do not tolerate being dropped between the freezing conveyors until they have gained sufficient frozen stiffness to preserve their undeformed shape; the said method consisting of placing the said delicate items of food on the freezing conveyors for being conveyed through the freezing tunnel for a sufficient freezing dwell time in the freezing tunnel for the particular foodstuff being fully frozen; gaining that by having one or more of the freezing conveyors stopping in a fixed sequence. By increasing the number of conveyors that are stopped in a fixed sequence it is possible to increase the efficiency of the freezer beyond that of conventional ones.
BACKGROUND ART
By using conventional methods the products to be frozen in a conventional freezing tunnel, having at least two or more freezing conveyors supported therein, are fed onto the top freezing conveyor which conveys the products through the freezing tunnel in a continuous movement. On this freezing conveyor only the surface of the products gets to be frozen. The products, though, hardly become firm enough in shape to be moved undeformed onto the next freezing conveyor where the item is fully frozen. Finally the product is delivered from the end of the last freezing conveyor for further processing.
A U.S. Pat. No. 3,708,995 describes a freezing tunnel of the above-mentioned conventional type with a multiple run conveyor, which is formed by three layers of endless conveyor belt, where each conveyor belt moves in the opposite direction compared to the conveyor belt next in row below. In said freezing tunnel the products to be frozen are dropped from the one freezing conveyor belt to the other. The total dwell-time of the products in the freezing tunnel increases with the number of freezing conveyors used and thereby the efficiency per area occupied by the freezing tunnel in the field of general freezing of foodstuff.
The most important factor that limits the efficiency of conventional freezing tunnels in the field of freezing delicate individual items of food, where appearance and shape of the product is important, is the length of time the individual items can dwell in the tunnel free of each other, exposed to the cold flow of air that freezes them without being subjected to any handling that will deform them.
In conventional freezing tunnels such as the one described in U.S. Pat. No. 3,708,995 the time it takes for the products to gain their frozen shape and become sufficiently firm to allow their transfer without damaging their form between the top freezing conveyor and lower freezing conveyors is limited by the area and speed of the top freezing conveyor.
Thus, the main factors that can be utilized to control the surface freezing dwell time of the product on the top freezing conveyor for safe transfer between the freezing conveyors are the size and speed of the top freezing conveyor belt.
Therefore, when the efficiency of the conventional freezing tunnel is under consideration concerning the quick freezing of delicate foodstuff, the actual number of freezing conveyors is irrelevant if the product can not be transferred undamaged and undeformed between the conveyors since it is the surface freezing dwell time of the product on the first conveyor which matters.
Thus it is the area and the speed of the first and topmost freezing conveyor belt which determines the efficiency of conventional freezing tunnels in the field of freezing of delicate products.
For example, a fish fillet to be frozen in a freezing tunnel will need a certain freezing dwell time to reach the firmness needed to stand the handling that accompanies being moved between freezing conveyors. If the fillet is not sufficiently firm in shape to be moved between the conveyors its shape will be altered and deformed when moved between the conveyors in a conventional freezing tunnel. The fillet will therefore take on a deformed shape in its fully frozen condition on the lower freezing conveyors and—thereby, as a sales product—become unsuitable merchandise according to the demands made in the market for frozen fish fillets.
For these reasons conventional tunnel freezers can take up a lot of space, depending on the desired size of the topmost freezing conveyor belt. That can become a major problem when it comes to tunnel freezing delicate products on board ships or in a factory where available space is limited and of the utmost importance for a producer who wants to achieve acceptable productivity.
The extreme cost of building and running large tunnel freezing rooms is considerable and can be decisive in the feasibility of using tunnel freezing as a production method, and the profit achieved by the added value gained by this method of freezing delicate individual items of food can be lost.
DISCLOSURE OF THE INVENTION
The method for freezing of delicate items of food of the present invention, is characterized by feeding, by means of the movable feeding conveyor, the upper freezing conveyors, which all rotate in the same direction, in a fixed sequence, where the first one of the said freezing conveyors to be fed stops when its surface area has been fully covered with the products to be frozen and the feeding conveyor moves by a controlling device to the next one in the sequence of the said freezing conveyors, which starts running thereby until its surface area has been fully covered with the products to be frozen, whereby it stops and the feeding conveyor moves over to the third one in the sequence of the said freezing conveyors, which starts running thereby until its surface area has been fully covered with the products to be frozen, whereby it stops, while in the meantime the two of the said freezing conveyors which were fed first in the sequence have stayed at a standstill, whereby the delicate products on the first freezing conveyor belt have had enough freezing dwell time during said standstill for them to gain their frozen shape and sufficient stiffness before being dropped without being deformed or damaged onto the bottom freezing conveyor belt, which runs at such a speed in the opposite direction compared to the upper conveyors that thereby, on said conveyor, the said products freeze completely through on their way out of the freezing tunnel for further processing.
The method is particularly suitable for freezing delicate products which cannot be moved between freezing conveyors without altering their shape and form, thus being damaged when moved between the freezing conveyors and becoming unsuitable as a viable product.
By this method the time for freezing through the surface of delicate products is multiplied, depending on the number of freezing conveyors used, when tunnel freezing products which cannot be moved between conveyors without damage to said products.
By this method efficiency is increased compared to freezing tunnels as well as the freezer described in U.S. Pat. No. 3,708,995.
REFERENCES:
patent: 3402568 (1968-09-01), Kamin et al.
patent: 3708995 (1973-01-01), Berg
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Yeung George C.
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