Field of innovation

This invention relates to an apparatus and method for coating food snack pieces with a small amount of oil, fat or other lipophilic substances.

Background of the innovation

In many applications in the snacking industry food pieces are deep fried in oil to get a good texture and flavour. Frying leads to a very high fat content of 20 to 40%, which is an undesirable feature by many consumers. It is well known in the art, that potato slices and other vegetables can be baked monolayer without any oil, by using microwaves, infrared, hot air, fluidized bed, steam or combinations thereof, to create fat free chips. One of the first to describe a production of fat free chips was US 4 800900 by JR August et al, claiming a process where a monolayer of slices are treated in infrared, then microwaves and then a second infrared heat step to crisp the surface.

Totally fat free potato chips have not reached any larger commercial footprint. W02012104215 to Spurr et al teaches that the consumer demand that potato chips that looks, feels and taste like deep fried chips. Spurr et al further teach that adding 7-13% oil to sliced potatoes and then heat them with microwaves and hot air will create a similar mouthfeel, texture and look as deep fried chips and suggest a first dipping of the potato slices in 90 C oil for about 90 seconds and then cleaning them with water and air jets. In WO 2012104217 to Spurr et al describes that it is desirable to first pre-dry oiled potato slices overlapping in a microwave oven and then dry the slices in a rotary microwave oven but face a problem of clumping of potato slices. Spurr et al claim a separating devise of potato slices after the pre dry and before being tumbled.

US20170112180 to J Ashourian et al describes a continuous feed of potato slices through a dip in an emulsion of oil and water claim a continuously mixer for water and oil and feed the tank. To get an even adding of oil the same amount of emulsion must be left on each slice. The emulsion will also leave extra water necessary to dry away. GB 2324952 to R M Rolston et al describes that two sets of rotary sprayer discs are mounted above and below the conveyor, spraying oil onto a monolayer of potato slices before baking. WO 9410857 to J Bell et al suggest to spray or brush the surface of a monolayer of potato slices with oil before baking.

A magnificent limitation with monolayer potato slices through a major part of the process is that it creates huge space and difficulties to make cost efficient ovens and process lines. Special slicers are also needed, as for example a Grote HS 640. Chips industry is mainly using centrifugal slicers, as Urschel CC slicers, with a normal throughput of 1 kg slices per second. The slices are then normally continuously washed to get rid of surface starches. One example of such continuous washer is Gentlewash™ from Heat and Control lid. When slices are conveyed out of the Gentlewash™ they are rather spread out over the conveyor but with some overlap. If oil would be applied directly onto the bed of slices coming out of the washing step it would both miss the overlapping parts and the surface water would reject_the oil and make the coating uneven. If slices, in this stage, are tumbled, in for example a seasoning drum, while being sprayed with oil, the slices will easily stick to each other and creates uneven oil layer.

There is a need for an apparatus and method for applying a very small amount of oil or other fluid liquid to coat sliced product before further steps of baking or heating and that can do it with high industrial throughput.

Summary of the invention

It is an object of the present invention to fill a long felt need by providing an apparatus and method for coating food pieces with oil, fat, lipophilic substances or other coatings before further baking or processing, in an economical continuous process and with high throughput. In particular the invention relates to an apparatus for coating potato slice

This object is achieved by an apparatus according to claim 1 and a method according to claim 5. An apparatus for continuously coating food pieces comprising: a first part comprising a vibrating feeding conveyor having an upstream and downstream end ; an open ended heating cavity with heat sources for heating food pieces conveyed through the cavity by the vibrating conveyor ; a second part placed at the downstream end of the first vibrating conveyor comprising; a high speed conveyor belt having a upstream and downstream end; Sprayers placed further downstream the end of the fast conveyor , arranged in such way that they can spray coating on airborne and gliding food pieces.

A method of coating food pieces comprising a) a first step of moving food pieces on a vibrating feeding conveyor from a first upstream end to a second open downstream end through a heating cavity wherein heat is transferred to the food pieces. b) a second step of conveying the food pieces on a fast conveyor from a first upstream end to an downstream end in such speed that the food pieces will get airborne and glide from the end of the conveyor and spraying the food pieces with coating while being airborne and gliding.

Therefore the apparatus and method of the present invention is suitable for preparation of low fat snacks of a variety of raw materials. Food pieces may include potato, sweet potato, parsnip, beetroot, avocado, zucchini, pineapple, apple, or any fruit or vegetable that can be eaten as snacks in a dried state. Food pieces can be made from dough that are formed to pieces or sheeted, rolled and cut may be used, as for example nachos. The apparatus and method may also be used for extruded food pieces including direct expanded or dried pellets. The present invention may also be used for popcorn or peanuts and other nuts. The present innovation is suitable for any food piece that is gaining of having a thin coating before further processing or for other means as for example giving the food snack pieces a final luster.

The apparatus and method of the present innovation is especially adopted for coating potato slices Standard industrial steps of preparation of raw slices is preferable and may include steps of destoning and washing of potatoes, scrubbing or peeling, pulse electric field treatment, slicing, washing of excess starch from slices and chemical treatment. A standard pulsed electric field (PEF) setting, when treating 2400 kg an hour of potatoes is 0,4 to 1,4 kJ per kilo slices and could go as high as 20 kJ per kg. The PEF could be done with any commercially available equipment as from for example Kea-Tec or Scandinova and setting ranges of voltage of 0-30 kV, current range of 0-700A, pulse repetition frequency of 0-500 Hz and pulse length of 0,5-10 micro s. The potatoes are preferably sliced to 0.4-3 mm thick but more preferable 1.0 to 2.2 mm thick. In the washing of slices 0,1 to 3% of salts can be used. Even though a pulsed electric field treatment makes a smoother cut there are usually some broken cells with trapped starches. As slices are heated the starches can swell and get sticky and therefore it can be advisable to use starch dissolving enzymes in the washing step; selected from the group consisting of an amyloglucosidase, glucose oxidase, laccase, lipase, maltogenic amylase, alfa,, beta, or gamma amylase, pectinase, pentosanase, protease, and transglutaminase; or emulsifiers that reduce or totally counteracts stickiness.

In the present innovation the potato slices are coated in apparatus having two parts and steps. First the potato slices are vibration conveyed through a cavity of infrared heat and/or hot gas that will heat the slices and dry the surface. The vibrations, heat and drying will make the slices easy to separate. In an exemplifying embodiment of the present invention an input flow was set to 2400 kg per hour of 1,5 mm potato slices of the sort Lady Rosetta with a dry matter of 21,7%. The potato slices were vibration conveyed from downstream end to upstream end for 12 seconds on stainless steel 2 mm kernet network with 86% open area and sized of width 1200 mm and length of 3600 mm. The heating unit applies 60 kW per kilo slices. The heating unit applied hot gas blown down on the slices with impact speed 3 m/s and gas temperature of 180 C. The second part and step is a high speed conveyor that when correctly managed separate the slices and make them airborne after the end of the fast conveyor. Sprayers further down the projected path of the gliding slices create upward and downward curtains of coatings which the slices glide through. By regulating the speed of the conveyor and the flow in the sprayer a controlled and even coating can be achieved. In an exemplifying embodiment of the present invention the fast conveyor convey was set to 20 m/s and consisting of a teflon coated glasfiber 4 mm net endless conveyer. Spraying unit was set to yield a film of 1,9% oil based on initial wet base onto every slice.

When coating other food snack pieces, as for example directly expanded snacks or nuts it is not always necessary to use the first part of the machinery as the surface is already dry and food pieces are easy to separate and only the second part and step is needed to be applied. The vibrating conveyer could still be used but could also be replaced by another conveyor as long as the food snack pieces will be singulated on the high speed conveyor and through the curtains of coating. The second part and step can also be used alone if potato slices or other food pieces have been pre dried by other means.

An advantage of the present invention is that a very even coating can be applied to potato slices in a high throughput manner. Another advantage of the present invention is that oil can be added to a heated surface which in turn leads to even more effective moister diffusivity and high overall drying rate and easy separation of the slices in further drying steps.

The vibrating conveyor can be made of any food grade and heat stable material as metal linked sheet, metal nets, perforated plate, a grid, expanded metal, a malignant grid or a welded grille. It is preferable if the sheet has large holes areas for good throughput of radiation and/or hot gas. When processing extruded corn curls, cuts from extruded wholegrains or sheeted corn masa it is preferable to change the conveyor as the food pieces otherwise easily got stuck in a the hole areas. The conveyor can be changed to a solid metal sheet. It is preferable that the metal sheet is not totally flat but has a patterned and texturized surface to minimize the surface contact with the food pieces. It is also referable all metal parts should be covered with a high infra-red reflecting material as gold, silver, ceramics, aluminum or other high reflecting material covered so the uptake of rays would be minimized. When using a solid metal sheet it is obvious that the lower heating units are turned down or off. There are many alternatively commercial available motovibrators and also many well-known designs of vibration feeders and also alternative ways of placements of the motovibrator. Any well- known or commercial type of vibrating feeder and vibrator system, that fulfill the purpose of separating and feeding the food pieces could be used in the present innovation. The potato slices can be vibration conveyed from downstream end to upstream end for 3 to 400 seconds or even longer depending on distance to convey but it is more preferable with a time of 6 to 30 seconds.

The heating unit can be built up numerous alternative kinds of heaters capable of drying off the surface water and heat the product as for examples porous shortwave burners, ceramic, metallic fiber mediumwave burners and catalytic longwave burners embedded combustion gas burner, thermal oil radiators or electrical elements SER burners, electrical wire or direct fire burners as ribbon burners. All above heaters can reach a sufficient initial drying but with differentiated efficiency and power density. In the examples of infrared heaters the wavelengths can vary between 550 to 12000 nm. There are many frequencies, combinations and overtones of frequencies that can heat the food pieces. In one embodiment the heating tube is a halogen heater lamp with a power of 1000 W and emit, when set on full power, a peak wavelength of 1100 nm and a color (CCT) of 1012 K. The tube has a gold reflector on the back of the quartzglas. This type of tubes can be placed very close to a next tube and can together with other bulbs create a heating panel with up to 200 kW per square meter. The heat can easily be regulated by phase shifters or be pulsed. The heating tube could also be placed sparser to reach a heat intensity that match the product to be coated. By changing the bulb different lamps can be chosen to match the food pieces to be dried and heated, as shortwave, midwave or longwave lamps with wavelengths of.750 to 6000 nm. As parts of the infrared rays can be reflected on the food pieces, penetrates through or miss the food pieces it is preferable to have infrared reflecting boundaries of the heating zone so the rays will be redirected to the slices and not heating the environment. It is preferable that all parts of the heating unit facing the heating tube is of infrared reflecting material as gold, silver, aluminum or ceramics or other infrared and heat reflecting material. The heating unit applies 2 - 400 kW infrared heat per kilo and more preferable 20 to 60 kW. A fan in the heating unit can blow gas onto the slices with a preferable impact speed of average 0,1 to 12 m/s more preferable 1 to 6 m/s . As the gas pass the heating element it will exchange heat to the gas and the gas temperature is preferable regulated to 60 to 250 C, more preferable 110 to 200C. Energy efficiency is an important factor for economic and environmental reasons but also for increased efficiency of the heating unit. Therefore the energy from vaporing steam is preferable collected in an outgoing venting pipe and used in other process steps or led to a condenser. In a most preferable arrangement the steam is led to a gas separator taking condensate away and leading back hot gas to the heat units. The energy transferred by gas and by the heating element could be balance against each other from 0 to 100% depending on product. A method wherein the heating unit transfers a total of 50 kJ to 1195 kJ to be absorbed by the per kg of potato slices or snack food pieces.

The high speed conveyor can be made of various food grade materials such as for example stainless steel, urethane, polypylene, acetal, polyethylene, silicone or Teflon covered glasfiber net. It can be driven by any suitable commercial available motor. The fast conveyor convey can be set to 1 to 600 m/s and more preferable 3 to 80 m/s. There are some variables to consider; you want the conveyor to grip the pieces but at the same time easily leave the conveyor and make a good projected path from the end of the conveyor. You also want good speed but if the conveyor speed is set too high there is a tendency that the potato slices or other snack food pieces starts to spin or flip. In one embodiment the fast conveyer is an Teflon coated glasfiber 4 mm net endless conveyer and a speed of 20 m/s and each slice totally separated from another and made a good projected path. The sprayers could be using compressed air to spray the food pieces that passing by. The downside with compressed air is that it easily produces a mist that attaches to other equipment and also disturbs the path of the slide flying potato slices. The coating of the food snack pieces as potato slices could be made by a bakery spinning plate oiler or a vertical oil curtain but it is to the inventor findings that the easiest and most controllable way is to use a hydraulic spray as a PulsaJet™. Other hydraulic system can be used as well. The food pieces are coated with 0,01 to 30 weight percentage of oil and more preferable 0,1 to 3% of oil.

It is obvious for the one skilled in the art that other substances than oil, fat and other lipophilic substances or other coatings could be used in the apparatus and method. It is also obvious that the apparatus and method is not changed due to different earlier steps of treatment of the food pieces or further processing steps of the coated food pieces.

The novel features of the present invention will be further explained by the drawings and detailed descriptions. It should be understood that the drawings are for illustration and descriptions are not intended to as a definition of the limits of the present illustration.

Brief description of the drawings

The drawing in figure 1 to 6 describe one embodiment and method of an exemplifying apparatus for coating food snack pieces.

Figure 1 is a top view of the coater.

Figure 2 is a side view of a vibrator feeder part of the apparatus.

Figure 3 is a side view of an upper heating element unit above the vibrating conveyor that feeds the food pieces forward.

Figure 4 is sectional view of separated parts of a vibration conveyor net and three upper heating units and three lower heating units of the apparatus.

Figure 5 is a side view of a self-standing heating unit, fast conveyor and sprayer unit.

Figure 6 is a sectional perspective view of the coater

Detailed description Figures 1, 2, 3, 4, 5 and 6 disclose an outline of an exemplifying embodiment of the apparatus and method in according to the present invention. It should be noted that same reference signs throughout the accompanying drawings refer to same of like components.

Figure 1 is a top view of the apparatus for continuously coating food pieces comprising: A primary conveyor 101 for vibrating feeding food pieces 103 from an upstream end 105 and downstream end 106, driven by vibramotors 107, 109, through an open ended heating cavity 110. A high speed endless conveyor 111 having a upstream end 112 and downstream end 113 for accelerating food pieces 103 coming out of the heating cavity 105 arranged in such way that food pieces 103 will be shortly airborne when leaving the high speed conveyor end 113. A spraying unit 115 placed further downstream the high speed conveyor belts end 113 for coating the food pieces while being on the projected flying path. Food pieces can then be further baked or processed 160. The high speed conveyer 111 consist of an teflon coated glasfiber 4 mm net endless conveyer and preferable set to 1-600 m/s. The spraying unit 115 is preferable set to apply 0,01 to 30 weight percentage of oil or other coating. The apparatus consist of two divided 114 parts and it is possible to run the spraying unit 115 freestanding.

Figure 2 is a side view of a vibration conveyer comprising a suspended body 205 hanging on a substructure 203 with the aid of a wire 207 attached in a spring 210. The conveyer 101 is attached to the body 205. The motovibrator 107 is attached to the body 205. In the illustrated embodiment a pair of counter-rotating external electric motovibrators from the WAM-group is fitted in parallel on both sides of the suspended body 205. The motovibrator 107 has eccentric weights fitted on both shafts creating a sinusoidal force and the angle of the weight could be turned from 0 to 100% eccentricity. The full speed frequency of the present motovibrator is 1000 Hz and can easily be controlled by an inverter or other steering equipment. By changing the angle, frequency and eccentric weights of the motovibrator 107 a suitable amplitudes and vector can preferable be set to get a good separation and flow and reach a total separation of every food piece by the conveyor downstream end 106. The conveyor 101 in the illustrated example is made of stainless steel krenel network, 2 mm thick steel wire, diameter of 15 mm and an open area of 86% and is attached to the substructure 205 by screw it tight with a distance 213.. The conveyor 101 can easily be changed depending on what food pieces that are being processed.

Figure 3 is a side view of an upper part of a heating unit 305 comprising a fan 301 and a heating tube 302 for creates a heating and drying effect upon the food pieces 103. The heating tube 302 has an end connector 304. An electrical wire 306 goes through an isolating material 308 and to an electrical wire terminal 310. The fan 302 blows gas through a holed plate 312 and down towards the food pieces 103 on a vibrating conveyor 101 and passing the heating tube 302 and the connectors 304. The gas going into the fan 302 could be taken from fresh air or pre heated fresh air, steam or cleaned and recycled steam. A mirror unit as the upper unit 305 can be placed beneath the conveyor 101 but facing upward. The heating tube 302 is a halogen heater lamp with a power of 1000 W and emit, when set on full power, a peak wavelength of 1100 nm and a color (CCT) of 1012 K. The tube has a gold reflector on the back of the quartzglas.

Figure 4 is sectional view of separated parts of the vibration conveyor 101 and three upper heating units and three lower heating units 305 of the apparatus. The conveyor 101 has stabilizing crossbars 419. The upper and lower heater units 305 and the conveyor 101 are separated in figure 4 but closed when in operation and arranged in such way that leaving a space for the conveyor 101 between the heater units 305. Adjacent side plates 405 and an inlet/outlet plates 407 are attached to the heating unit 305. It is preferable that the inlet/outlet plate 407 is lower plate than the side plates 405 for creating a gap between the upper and lower heating units when moved together and enable easy infeed and outfeed of food pieces. The adjacent side plates 405 has holes 413 wherein the stabilizing crossbars 419 can move. When in operation the conveyor 101 is connected to the vibrating body 205. The upper or the lower heating units 305 could be turned off so heat is only applied from one side.

Figure 5 is a side view of an coating unit without the vibrating feeder seen in figure 2 comprising . Upper heating and lower heating unit 305, a high speed conveyor 111 for accelerating food pieces so they can slide fly through curtains of oils created by an upper sprayer 515 and a lower sprayer 519.. The upper sprayer 515 and the lower sprayer 519 are airless sprayer that are driven with hydraulic pressure, a hydraulic system PulsJet™ from Spaying System Co, with a flat nozzle creating an oil curtain that is narrow in the direction of travelling. PulsaJet sprays can provide a very controllable flowrate of oil by pulsing the oil, with up to 25000 cycles per minute and regulate the oil flow from 10 to 100%. If wanted to one of the sprayers could be turned of and only coating one side. Excess oil from the upper sprayer 515 is spayed into a collector 517 and excess oil from the lower sprayer 519 is sprayed into another collector 521. Energy efficiency is an important factor for economic and environmental reasons but also for increased efficiency of the heating unit 305. Therefore the energy from vaporing steam is preferable collected in the outgoing venting pipe 550 and is preferable used in other process steps or led to a condenser. In a most preferable arrangement the steam is led to a gas separator taking condensate away and a blower leading back hot gas to the heat units 305 by an incoming pipe 351 to one or multiple heating units 305.

Figure 6 is a sectional perspective view of the coater comprising a vibrating conveyor 101 feeding food pieces 103 out heating unit 305 and into the spraying unit 115 and their onto a high speed conveyor 111 which move so fast that the food pieces keep their momentum forward as the conveyor returns turns at it's downstream end 113 and slide fly between an upper sprayer 515 and an oil collector 517 through an oil curtain 611 and keep slide fly through a second oil curtain 617 between a lower oil spray 519 and a collector 521. The food pieces could then be landed for further processing 160.