METHOD AND APPARATUS FOR MAKING FOOD CHIPS

Field of the invention

The invention relates to a method and apparatus for making chips of food, comprising a heat source.

Background of the invention

Potato chips and other snack foods are very popular. There are many methods in preparing snack foods such as potato chips and other forms of vegetable and grain chips such as corn or tortilla chips. Most of these methods rely on cooking the snacks in oil, known as deep frying. The deep frying creates a very crisp structure and lower the moisture content but will allow some uptake of oil. The frying process typical results in a fat content of 20-45 % fat.

Fat is very high in calories and heavy intake of calories might lead to overweight. Apart from overweight, high intake of fat may also lead to other health problems such as heart deseases and knee problems. Most major health organisations recommend that not more than thirty percent (30%) of the total calorie intake be from fat.

Generally, there are two very importing factors when it comes to food; price and taste. It has therefore been an object over a long period of time to cost effectively produce a fat-free snack food product, for instance potato chips, that looks, feels and taste similar to deep fried chips.

Having recognised the long felt need, other inventors have attempted to produce a commercially acceptable fat-free potato chips. Earlier attempts have needed considerable economic investments in microwave or radiowave techniques or have not got the desireable taste and structure similar to deep fried chips.

In a process disclosed in US 4,283,425, a single step of heating by microwaves (910-915 mhz or 2400-2500 mhz) was used. The slices were also dipped in or sprayed with an edible oil prior to final microwave cooking which led to a fat content of 3-5% by weight which is too high to be classified fat-free. Thus, this product was basically a "low-fat" potato chip.

In a further process disclosed in US 4,800,090, sliced potatoes were first subjected to an infrared (high intensity 46 micron wavelength) heating step to warm their exterior, then to a microwave energy (915-2450 mhz) heating step to warm their interior, and finally to another infrared (4-6 micron wavelength) heating step to brown them into a crisp, fat-free, potato chip snack food product that was low in calories and had a long shelf life.

US 4,906,483 discloses a process in which the microwave cooking step was employed early in the process to activate the release of starch while the potato slices were still immersed in water followed by a cold water rinse and final cooking in radiant heat until brown and crisp to produce a fat-free potato chip.

US 5,470,600 discloses a process in which the slices are initially cooked in a three zone primary oven by first radiant heating the slices and then subjecting the slices to two successive stages of forced air heating and a final cooking in a dielectric heater by subjecting the slices to long wavelength radio frequency electromagnetic waves.

A still further fat-free process is disclosed in US 4,919,965, in which the potato slices are simultaneously finally cooked by compressing them between dual opposed heating surfaces which were 50% relieved driving the moisture into the voids in the cooking surfaces to produce a fat-free potato chip.

Summary of the invention

It is an object of the present invention to fill a long felt need by providing an apparatus and a method for making a fully cooked fat-free food chip product with a long shelf life that looks, feels and tastes like a conventional deep fried chip in an economical continuous process without using any cooking oil whatsoever.

This object is achieved by an apparatus according to claim 1 and a method according to claim 7. According to the present invention, an apparatus for making chips, comprises a source of heat and a conveyer belt arranged such that, when in use, chips are held between the belt and the heat source at least a part of the path of the belt, and wherein the belt is steam permeable. The steam permeable belt allows for steam to leave the chip while being heated and hence dried.

Therefore the apparatus and method of the present invention is suitable for the preparation of fat free chips made from a variety of

vegetables, grains, fruit and the like which can be cut or otherwise formed into flat, generally thin slice shaped portions. Any potato traditionally used for conventional deep frying chip processes may be used. Some varieties of potato that have normally been undesirable for deep frying may be used. The present invention may be used to prepare chips from raw vegetables, potatoes and the like that have been cut into slices. The methodology of the present invention is also suitable for preparation of a variety of products that are flat slice shaped and traditionally baked, such as crackers, some sort of buiscuits and the like. The present invention is especially adapted for the preparation of potato chips.

Initial preparation of raw potato includes washing, scrubbing, cutting them into pieces and then washing the slices from excess starch and moisture. The slices are preferably 0,4-3 mm thick but more preferable 0,7- 1 ,2 mm thick. Preferably, at least the chips contacting surface of the belt comprises a non-stick material, such as e.g. teflon. The belt could for instance be glass fiber belts coated partially or completely with a non-stick material such as teflon. The food contacting surface of the heat source could also be coated with a non-stick material or for instance be made of stainless steel. In a preferred embodiment of the present invention the heat source is a drum dryer, i.e. the belt is arranged at least partially circumferentially of the drum dryer. Preferably the drum dryer also rotates with the same speed as the belts such that friction and hence wear is avoided. For more efficient heating and drying, a heating mantle is preferably arranged circumferentially radially outside of the drum dryer and the belt.

The slices should be mono layered and fed between the belt and the heat source. If a conveyer belt following the drum is used it should be very thin, preferable a teflon coated glass fiber belt with a thickness of 0,075 to 1 mm, more preferable 0,075-0,15 mm. Any commercial drum dryer of smaller size or up to 6 meters wide and 6 meter in diameter could be used. The food contacting surface of the drum dryer could be coated with a non-stick material or comprising other food grade material, e.g. stainless steel, and the chips are scraped off from the drum dryer. The choice of source of heating is of less importance. The temperature of the drum dryer could be 110-250 ⁰ C on the surface but more preferable 130-220 ⁰ C. The belt should be porous or perforated, i.e. steam permeable, and covered with a heat restrained and food grade material such as teflon or silicon, preferably a porous teflon coated

glass fiber belt with a thickness of 0,075 to 1 mm. The belt should be pressing against the food slices. The food slices and the belt preferably follows the rotation of the drum. The process time is preferably between 10 and 300 seconds but more preferable between 90 and 200 seconds. If desired the slices could be fully cooked in this stage so they reach a final moisture level of about 2-6 % but they could also be partially cooked and fully dried out by other commercial available drying machines such as hot air blowers, by IR or microwaves. For economical reasons the final drying is preferably carried out by using for instance a jetblower. An alternative embodiment of the apparatus according the invention comprises a second belt arranged such that, when in use, chips are held between the two belts, the second belt arranged between the first belt and the heat source, wherein at least a part of the path of the two belts are arranged adjacent said heat source and wherein the belts are arranged for synchronous movement at said part of the path for heating the chips.

Preferably, in this embodiment, at least the chips contacting surfaces of the belts comprises a non-stick material such as teflon. It is also with this embodiment advantageous to use a drum dryer, wherein the two belts move with the same speed and also with the same speed as the drum dryer in order to avoid friction and hence wear.

Short description of the figures

The invention is explained below in more detail with reference to figures. Figure 1 is a perspective view of an embodiment of the apparatus according to the present invention.

Figure 2 is a side view of the embodiment shown in figure 1.

Description of exemplary embodiment of the invention Figures 1 and 2 disclose an outline of an embodiment of the apparatus

1 according to the present invention. 0,8 mm slices of potato 2 are monolayered on a 0,075 mm conveyer belt 3 of glass fibre covered with teflon. The conveyer belt 3 and the slices of potato travels around a 2 meter wide and 2,5 meter diameter drum dryer 4 of an initial surface temperature of 175 C. Heating elements 5 of black painted steel are arranged 2,5 mm above the drum dryer 4 and set to 175 C. The slices 2 are pressed down to the drum with a 0,22 mm thick porous conveyer belt 6 of glass fibre covered with teflon

and the speed is set such that the potato slices 2 are dried for 2 minutes and 15 seconds until the slices of potato reaches a moisture level of about 30 %. The slices then falls down on a open mesh conveyer belt 7 travelling with the same speed as the drying drum. A further open mesh conveyer belt 8 holds the potato slices together with the first open mesh conveyer belt 7 while the potato slices 2 are exposed to forced hot air from below and above. The blowers 9 have a 12 mm opening and are set to 200 C and 20 m/s. The potato slices 2 reaches a final moisture level of about 7%. The potato slices 2 could then optionally be fed into a seasoning unit (not shown) before the packaging.

As an alternative it is possible to feed potato slices 2 between the steam permeable conveyer belt 6 and the drum dryer 4, i.e. omitting the first conveyer belt 3. Advantageously, the drum dryer 4 surface contacting the potato slices 2 are coated/covered with a food grade material. Also, whether one or two conveyer belts are used, it is possible to two or more drum dryers 4 after one another, for instance, if there is a limitation to the height of the apparatus or for reasons of quality of the produced food. Also, a first drum dryer at a temperature about 200-220 ⁰ C could be used as a first step. The second drum dryer could be set at a slightly lower temperature of about 180- 200 ⁰ C and then a third drum dryer at a temperature of about 160-170 ⁰ C could be used for the final stage. External heating elements could also be used. The above described method/apparatus could be used in order to speed up the process and at the same time minimize the risk of burning the food. The foregoing is a disclosure of preferred embodiments for practicing the present invention. However, it is apparent that device incorporating modifications and variations will be obvious to one skilled in the art. Inasmuch as the foregoing disclosure is intended to enable one skilled in the art to practice the instant invention, it should not be construed to be limited thereby, but should be construed to include such modifications and variations as fall within the scope of the claims. For instance, the optimum time for the process in the apparatus according to the invention will be different if the food is preheated or pre-treated in some way.