Food or edible material: processes – compositions – and products – Measuring – testing – or controlling by inanimate means – Preparing solid product in final form by heating
Reexamination Certificate
2000-01-06
2002-09-24
Yeung, George C. (Department: 1761)
Food or edible material: processes, compositions, and products
Measuring, testing, or controlling by inanimate means
Preparing solid product in final form by heating
C426S523000
Reexamination Certificate
active
06455085
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of control of cooking apparatus, and in particular to control over the heat transfer rate to food products being cooked in a particular cooking apparatus such as frying apparatus. Cooking apparatus for implementing the method is also disclosed.
BACKGROUND ART
Cooking apparatus cooks food items by exposing such to a heated liquid cooking medium such as an oil, gas or molten solid fat. The liquid may be oleaginous or aqueous depending on the nature of the cooking process, whether boiling or frying. Gaseous media may include steam or heated air or other gases. Conventionally, the cooking process -achieved by transfer of heat to the food material - is controlled by controlling two variables, the temperature of the cooking medium; and the time for which food items are exposed to the cooking medium.
A number of problems may arise with this form of control in practice. For example, while temperature may be controlled it has generally been controlled in a somewhat imprecise way, the temperature being that guessed by the operator to be the optimum for the cooking process on the basis of minimal temperature data. A similar imprecision applies to the cooking duration. The duration may be approximately correct but not optimum. Then, a still further level of complexity and lack of precision may result where there is no single cooking temperature that is applicable throughout the entire cooking process but rather the temperature should be a function of time, that is, changing throughout the cooking process. By way of example might be mentioned the cooking of a meat item where it may be desired to seal the outside of the item at high temperature at the commencement of the cooking process, the temperature then being varied downward to a value which is then maintained for the remainder of the cooking process.
Further variability in cooking temperature may result from temperature variations caused, for example, by loading of frozen food items into the cooking chamber or cooking zone during the cooking process. The loading operation will cause temperature drop on contact of frozen items with heated cooking medium. This problem that requires to be addressed.
A vat frying application, as commonly used in the quickservice food industry, is one employing the principle of deep frying of food items by immersing them in a body of heated cooking medium. Deep frying is a process of significant concern to the Applicant. In that case, a difficulty arises that is largely accepted in conventional practice, that is control over the temperature at one specific location within the body of cooking medium. This is a compromised system in which local overheating and underheating may take place, not only compromising the efficiency and quality of the cooking process and the food items that result from it but also leading to problems with the operation of the equipment itself. Even if temperature control is attempted, thermal inertia of the cooking medium filled vat results in poor control response and unbalanced temperature profile.
If there is local overheating of cooking medium, food items may be overcooked or may be non-uniformly cooked. If temperature is high local to a heating element, food particles and crumbs in this location may carbonise causing a cleaning and cooking medium quality problem. The cooking medium may degrade, product texture may be adversely affected or the oil uptake into the product may be increased. The latter situation may be undesirable where oily food product quality is desired to be avoided. Overheating may be a particular problem where carbonised food particles deposit in the pipes conveying the cooking medium within a given cooking apparatus.
In vat fryers, complete dismantling, cleaning or replacement of the pipes might be required every three to five years or even less depending on the capacity and usage of the cooking apparatus. In any event, any deposition of “scale” will interfere with the efficiency of heating of the cooking medium by a heat exchanger and may be compensated for by techniques that may actually exacerbate the overheating problem, for example heating of the heat exchange element or heating medium to higher temperatures where overheating becomes even more likely.
Previous practice has aimed at addressing such problems by mechanical design measures such as scrapers and augers for removal of crumb deposits. Oil removal devices may also be required. For example, vats may be equipped with cross flow arrangements aimed at causing mixing of the cooking medium and a more uniform heating. Cold zones might be provided in regions where crumbs are likely to deposit such that the temperature is maintained below the carbonisation temperature. Steam purging might also be employed in an effort to prevent carbonisation but this technique is potentially dangerous. In addition, filtration systems such as drum filters, belt filters (with paper or cloth belts) or other complex filtration systems may be installed. Drum and belt filters which expose oil to air are undesirable.
SUMMARY OF THE INVENTION
It is the object of achieving better control over the cooking process by reducing the above problems with the minimum resort to complex mechanical arrangements that forms the basis of this invention.
With this object in view, the present invention provides a method of at least partially cooking food items by exposing them to a heated liquid cooking medium supplied by cooking medium delivery means to a cooking zone of a cooker including a control unit which, during a cooking process;
(a) controls the temperature of the cooking medium delivered to the cooking zone to a pre-determined setpoint specific for the food items by controlling heat output from a heat exchanger for heating cooking medium throughout the cooking process;
(b) controls the rate of convective heat transfer to the food items by directly controlling a sensed condition of cooking medium delivered to the cooking zone, other than temperature which is controlled in step (a), related to the rate of convective heat transfer; and, optionally,
(c) controls the rate of convective heat transfer to the food items by controlling a sensed condition of the cooking zone related to the rate of convective heat transfer.
Temperature control may be achieved throughout the cooking process by appropriately heating the cooking medium to a pre-determined setpoint for the cooking process using suitable heat exchangers which are operated bearing in mind the particular nature of the cooking medium being heated. For example, in the case of frying, where the cooking medium is an oil or molten fat, heating is desirably conducted in the absence of air using, for example, the flow heater arrangements as described in our Australian Patent No. 666944; and co-pending International Patent Application No. PCT/AU98/00552, filed 16th Jul., 1998, the contents of which are hereby incorporated herein by reference. Such heat exchangers may include a cooking medium cooling sub-system. Temperature may be varied as desired throughout the cooking process by suitable control over heat exchange element output.
The control over the rate of transfer of heat from cooking medium to food item may be achieved in a number of different ways. In establishing this control, the applicant has recognised that the cooking process commonly proceeds by a convective heat transfer mechanism rather than a conductive heat transfer mechanism. The thermal conductivity of cooking media such as oils and fats is quite low. Indeed oils and fats are insulators which only poorly conduct heat to food items being cooked.
Mechanisms of convective heat transfer rate control predicated on this understanding, must advantageously take into account the cooking process, the nature of food items to be cooked, such mechanisms may include the induction of turbulence in the cooking, medium especially local to a food item being cooked or, particularly desirably, control over the pressure or rate of flow of cooking medium delivered to the cooking zone or s
VOS Industries Ltd.
Westman Champlin & Kelly P.A.
Yeung George C.
LandOfFree
Method of controlling the operation of cooking apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of controlling the operation of cooking apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of controlling the operation of cooking apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2838752