WO2001015539A1

WO2001015539A1 - Apparatus and method of steam treating food, particularly fish

Info

Publication number: WO2001015539A1
Application number: PCT/NZ2000/000172
Authority: WO
Inventors: Suzanne Hills; Ronald Oates
Original assignee: The New Zealand King Salmon Co. Ltd.
Priority date: 1999-09-01
Filing date: 2000-09-01
Publication date: 2001-03-08
Also published as: AU7461700A

Abstract

The present invention relates to a method and apparatus for the steam treatment of food products. The apparatus (1) comprises a frame (2) housing a plurality of at least partially open chambers (3). The chamber (3) is provided with steam admission means (9, 10, 12, 13), and means (9, 10) for retaining a product (14) to be treated. The apparatus further comprises sealing means (15) adapted to seal at least one chamber (3) to provide a steam treatment area. Indexing means are also provided to move at least one chamber (3) into contact with the sealing means (15) to allow for steam treatment of the product (14).

Description

APPARATUS AND METHOD OF STEAM TREATING FOOD, PARTICULARLY FISH

Field of the Invention

The present invention relates to a method and apparatus for steam treatment of food products. In particular, but not exclusively, the method and apparatus are adapted for steam treatment of fish during production of fish products such as smoked salmon.

Background

Lister/a monocytogenes is a pathogen that has been isolated from external surfaces of fish. During filleting and other processing of fresh fish, contamination of the fish flesh with L. monocytogenes from the external fish surfaces can occur. The presence of L. monocytogenes in chilled, long shelf life, ready-to-eat food products, such as smoked salmon, is a food safety hazard. Cold smoked salmon in particular is a product that presents consumers with a risk of contracting listerosis as there is no heating step during processing to eliminate L. monocytogenes from the product.

A number of other potentially dangerous pathogens are found on a range of food products so the need to treat food products to provide products that are safe for consumption is always present.

It is therefore an object of the invention to provide a method and apparatus for steam treatment of food products, which minimises or at least reduces contamination of the final food product by bacteria or other pathogens. It is a further object of the invention to at least provide a useful choice. Summary of the Invention

In a first aspect the present invention provides steam treatment apparatus comprising:

a plurality of at least partially open chambers, each being provided with steam admission means and means for retaining a product to be treated; sealing means adapted to seal at least one chamber to provide a steam treatment area; and indexing means to move at least one chamber into contact with the sealing means, to allow steam treatment of the product.

Preferably, the apparatus comprises four chambers located about a central shaft. More preferably, the shaft is rotatable.

Preferably, the apparatus comprises four stations, one of which is a steam treatment station comprising the sealing means referred to above. Preferably, the other stations include a loading station, a rinsing station and an outfeed station.

Preferably, the steam admission means comprises one or more tubes each being provided with a plurality of holes. In one embodiment, some tubes are located adjacent a diffuser, which is adapted to diffuse steam exiting the holes.

Preferably, the means for retaining a product to be treated is a support tube, which may also be one of the steam admission tubes referred to above. More preferably, the support tube is provided with a support hook at one end thereof. In one embodiment the support hook is a two-pronged hook. Preferably, the sealing means comprises a door, adapted to sealingly engage with an open face of the chamber.

Preferably, the loading station is adapted to allow manual loading of the product to be treated into each chamber.

Preferably, the rinsing station comprises rinsing means to allow rinsing of the product after steam treatment. More preferably, the rinsing means comprises one or more spray units.

Preferably, each chamber is pivotally attached to the apparatus, allowing pivoting of the chamber relative to the apparatus at the outfeed station, for unloading of the treated product.

In a second aspect the present invention provides a method for steam treatment of a product, using apparatus as described above.

Preferably, the method comprises the steps of:

- locating product to be treated into one or more chambers of the apparatus described above; indexing the chambers such that at least one chamber containing product to be treated is in contact with and sealed by sealing means of the apparatus; - adrnitting steam to the sealed chamber(s) for a predetermined period of time; and removing the steam treated product from the apparatus.

Preferably, the indexing occurs as part of a continuous cycle. Preferably, the product is treated with steam for between about 1 and about 20 seconds. Preferably, the steam is maintained at about atmospheric pressure.

Preferably, the steam treated product is rinsed after treatment with the steam. Preferably, rinsing is with cold potable water, for a period of about 5 seconds.

In a third aspect the present invention provides a steam treated food product when prepared by a method of the invention.

Further aspects of the invention will become apparent from the following description. This description is given with reference to the accompanying drawings, Nn which:

Figure 1 : shows a plan view of apparatus according to a first aspect of the invention.

Figure 2: shows an end view of the apparatus shown in Figure 1 .

Figure 3: shows a side view of the apparatus shown in Figure 1 .

Figure 4: shows a plan view of a steam treatment chamber forming part of the apparatus shown in Figure 1 .

Figure 5: shows a side view of the chamber shown in Figure 4.

Figure 6: shows a front view of the chamber shown in Figure 4.

Figure 7: shows a fish support steam tube forming part of the chamber shown in Figure 4, with the retained fish in dotted outline. Figure 8: shows details of a fish support hook forming part of the fish support steam tube shown in Figure 7.

Figure 9: shows the plan view of the chamber shown in Figure 4 in more detail

Figure 10: shows a side view of a steam seal on a door forming part of the chamber shown in Figure 4.

Figure 1 1 : shows a plan view of a spray wash chamber forming part of the apparatus shown in Figure 1 .

Figure 1 2: shows a front view of the wash chamber shown in Figure 1 1 .

Figure 13: shows a side view of the wash chamber shown in Figure 1 1 .

Detailed Description of the Invention

The method and apparatus of the present invention may be used in the production of a wide range of food products including fish, animal, vegetable and fruit products. In particular, but not exclusively, the method and apparatus may be used to treat or pasteurise cold smoked salmon. The following description is given with reference to the production of cold smoked salmon, although it should be appreciated that the method and apparatus may be used to produce other products.

The method and apparatus of the present invention have particular application in providing an effective iistericidal step in the production of fish or animal products, although the method and apparatus may also be used to control or destroy other pathogens. The method and apparatus provide the effective stericidal step without affecting the textural quality of the product, or with only minimal or limited effect.

In general terms, the method of the invention involves steam treating the external surfaces of gilled and gutted salmon in the apparatus of the invention. The apparatus applies saturated steam at 1 00°C to all external surfaces of the fish for about 10 seconds. The steam heats all external surfaces (the skin, gill and gut cavities) where L. monocytogenes may be present to kill the bacteria, but does not heat up or damage the internal flesh of the fish. This means the characteristic uncooked texture of cold smoked salmon is maintained or largely maintained after treatment by the method of the invention.

A particular embodiment of the invention is now described with reference to the accompanying drawings. It can be seen from Figures 1 to 3 that the apparatus 1 of the invention comprises a frame or housing, that is not described in detail but is generally indicated by the numeral 2. The frame 2 houses four chambers 3. The chambers 3 are preferably formed of stainless steel and are provided on a rotating central pivot 4 and rotating frame 4a.

The apparatus 1 preferably has four stations, designated i) loading 5, n) steam treatment 6, in) rinsing 7, and iv) outfeed 8, which are further described below.

A chamber 3 is shown in more detail in Figures 4 to 6. Each chamber 3 is preferably provided with a fish support steam tube 9, which has a fish support 10 at one end. In this embodiment of the invention the support 1 0 comprises 2 prongs in a U-shape. The support 10 is preferably hollow and perforated, as shown in Figure 8. The steam tube 9 may also have a rod diffuser 1 1 located adjacent to it, shown in Figure 5. Each chamber 3 is further provided with one or more outer steam tubes 1 2, which have additional steam tubes 1 3 extending therefrom. These tubes direct steam to specific areas of the fish, a manner further described below.

For clarity and conciseness, further description is now given with reference to the operation of apparatus 1 .

During operation, each fish 14 is manually loaded into a chamber 3, steam treated, rinsed and deloaded from the apparatus 1 . Preferably, deloading is automatic.

As will be apparent from figures 3 and 7, the fish 14 is placed into the chamber 3 at the loading station 5 by placing the fish 14 over the fish support steam tube 9 and hooking the gill covers of the fish 14 over the two prongs of the fish support 10. The fish 14 is thus hanging vertically in the centre of the chamber 3.

Once the fish 14 has been loaded into the apparatus 1 , an operator indexes the apparatus by suitable means such as a button or foot pedal (not shown). The chamber 3 at the loading station 5 thereby indexes to the steam treatment station 6, the chamber 3 at the steam treatment station 6 indexes to the rinse station 7, the chamber 3 at the rinse station 7 indexes to the outfeed station 8, and the empty (unloaded) chamber 3 at the outfeed station 8 indexes back to the loading station 5. It will be appreciated that this indexing occurs as part of a continuous cycle.

At the steam treatment station 6, a door 1 5 moves in and seals the chamber 3. This can be seen in Figure 9. Preferably, the door 1 5 is pneumatically driven and formed of stainless steel. As shown in Figure 3, the door 1 5 may be moved by means of rams 1 6.

When a chamber 3 indexes to the steam treatment station 6 and the door 1 5 (which may be provided with rubber seal 1 7) moves in to seal the chamber 3, the steam tubes 9 and 1 2 match up with connecting tubes 1 8 in the door 1 5 (as shown in Figure 10). Each connecting tube 18 may include a flexible steam hose 1 9.

Pressure regulated steam is then introduced into the sealed chamber 3 through a steam distribution system, via door 1 5 for a set period of time. Each chamber 3 has a steam distribution system, which comprises the fish support steam tube 9 and fish support 10 (on which the fish 14 is hanging) in the centre of the chamber, and the one or more outer steam tubes 1 2 and 1 3. In the embodiment of the invention shown in the accompanying drawings, two steam tubes 1 2 are provided, each of which has one or more additional steam tubes 1 3.

The tubes 9 and 1 2 and support 1 0 are provided with a plurality of perforations or holes 20 (see Figures 7 and 8) through which the steam is introduced from a steam boiler (not shown) . Preferably, the steam is introduced in a uniform manner.

The rod diffuser 1 1 assists in diffusing the steam from the fish support tube 9. Correct direction of direct steam jets emerging from the perforations or holes 20 is important, to prevent physical damage to the fish. The additional steam tubes 1 3 are also directed at the fish being treated to ensure, as far as possible, complete steam coverage of the fish. The additional steam tubes 1 3 may be moved as required for treatment of other products such as poultry. Pressure of the steam at time of release into the chamber 3 is controlled by a pressure switch so that steam may not be vented into the chamber until a preset pressure has been achieved by the boiler.

The time may be varied between about 1 to about 20 seconds. Time and release pressure are controlled by a programmable logic controller (PLC - not shown). The steam temperature in the chamber 2 is 100°C.

At the end of the steam treatment, the steam is vented for about 5 seconds through a large exhaust (not shown) containing a fan to quickly extract the steam from the chamber 3.

In the embodiment of the invention shown in the drawings, the door 1 5 is provided with a vent 21 and an associated flap (not shown). The vent is held shut by steam pressure during steam treatment but opens to allow air flow when the exhaust fan activates.

After venting the steam through exhaust 22, the door 1 5 moves back and releases from the chamber 3. The base of each chamber 3 is sloped outwards to allow condensation to drain out of the chamber 3 when the door 1 5 is opened.

The chamber 3 then indexes forward to the rinse station 7. At the rinse station 7 the fish 14 is rinsed with cold potable water for a period of about 5 seconds to wash away loose scales and cool down the chamber 3. The water is directed into the chamber 3 with a series of spray units 23, as shown in Figures 1 1 -1 3.

Preferably, the spray units 23 comprise a water inlet 24 and spray nozzles 25. 45°, as shown in Figure 3. This is preferably achieved by providing apparatus 1 with a pneumatically driven ram 26 and fixing each chamber 3 to the apparatus 1 by means of a hinge 27 (see Figures 3 and 5).

The fish 14 slides off the fish support tube 9 and support 10 onto a bridging chute (not shown). The chute can be connected to a manual filleting bench or filleting machine for the immediate filleting of the fish. The empty chamber 3 then moves back to an upright position and indexes back round to the loading station 5.

The steam treatment time, steam door, steam venting time, rinsing time, outfeed and chamber indexing may all be controlled by a PLC with multiple programmes.

In one preferred form, the capacity of the apparatus 1 is approximately four to six fish per minute. The steam time is the limiting factor on the machine capacity. For example, a steam time of 1 0 seconds, plus 5 seconds for the steam venting, gives a capacity of four fish per minute. For a steam time of five seconds, plus five seconds for steam venting, the apparatus capacity is six fish per minute.

Preferably, apparatus of the invention is hygienically designed with stainless steel construction and easy to clean features. All joints are fully welded, and there are no crevices, dead spaces or voids in the design. The apparatus is easily dismantled; for example, chambers 3 are removable from the centre pivot and frame- 4, 4a for cleaning.

Although the invention has been described with reference to the production of fish products, and in particular steam treated cold smoked salmon products, it should be appreciated that the method and apparatus of the invention have applications for other food products to eliminate pathogens or reduce the overall bacterial loading on the outside of the product. It should also be appreciated that the apparatus may be adapted to accommodate other types of gilled and gutted fish and also other eviscerated animals such as poultry.

Although the present invention has been described with reference to a preferred embodiment, it should be appreciated that improvements and modifications may be made to the invention without departing from the scope of the invention.

Claims

Claims:

1 . Steam treatment apparatus comprising:

- a plurality of at least partially open chambers, each being provided with steam admission means and means for retaining a product to be treated; sealing means adapted to seal at least one chamber to provide a steam treatment area; and - indexing means to move at least one chamber into contact with the sealing means, to allow steam treatment of the product.

2. Apparatus according to claim 1 , comprising a plurality of stations, each one associated with one of the at least partially open chambers.

3. Apparatus according to claim 1 or claim 2, comprising the four at least partially open chambers.

4. Apparatus according to claim 3, in which the chambers are located about a central shaft.

5. Apparatus according to claim 4, in which the shaft is rotatable.

6. Apparatus according to any one of claims 2 to 5, in which one of the stations is a steam treatment station.

7. Apparatus according to claim 6, in which the steam treatment station includes the sealing means.

8. Apparatus according to any one of claims 2 to 7, further comprising a loading station.

9. Apparatus according to any one of claims 2 to 8, further comprising a rinsing station.

10. Apparatus according to any one of claims 2 to 9, further comprising an outfeed station.

1 1 . Apparatus according to any one of the preceding claims, in which the steam admission means comprises one or more tubes each provided with a plurality of holes or perforations.

1 2. Apparatus according to any one of the preceding claims, further comprising at least one diffuser.

1 3. Apparatus according to any one of the preceding claims, in which the means for retaining a product to be treated is a support tube.

14. Apparatus according to claim 1 3, in which the support tube is provided with a support hook at one end thereof.

1 5. Apparatus according to claim 14, in which the support hook comprises two-prongs arranged in a U-shape.

1 6. Apoaratus according to any one of claims 13 to 1 5, in which the support tube is provided with a plurality of holes or perforations.

1 7. Apparatus according to any one of the preceding claims, in which the sealing means comprises a door, adapted to sealingly engage with an open face of one of the partially open chambers.

1 8. Apparatus according to any one of claims 8 to 1 7, in which the loading station is adapted to allow manual loading of the product to be treated into each chamber.

1 9. Apparatus according to any one of claims 9 to 1 8, in which the rinsing station comprises rinsing means to allow rinsing of the product after steam treatment.

20. Apparatus according to any one of claims 9 to 1 9, in which the rinsing means comprises one or more spray units.

21 . Apparatus according to any one of the preceding claims, in which each chamber is pivotally attached to the apparatus, allowing pivoting of the chamber relative to the apparatus at the outfeed station, for unloading of the treated product.

22. A method for steam treatment of a product, comprising the steps of:

locating product to be treated into one or more chambers of the apparatus of any one of claims 1 to 21 ; - indexing the chambers such that at least one chamber containing product to be treated is in contact with and sealed by sealing means of the apparatus; admitting steam to the sealed chamber(s) for a predetermined period of time; and removing the steam treated product from the apparatus.

23. A method according to claim 22, in which the indexing occurs as part of a continuous cycle.

24. A method according to claim 22 or claim 23, in which the product is treated with steam for between about 1 and about 20 seconds.

25. A method according to any one of claims 22 to 24, in which the steam is maintained at about atmospheric pressure.

26. A method according to any one of claims 22 to 25, in which the steam treated product is rinsed after treatment with the steam.

27. A method according to any one of claims 22 to 26, in which rinsing is with cold potable water, for a period of about 5 seconds.

28. A product when treated by a method of any one of claims 22 to 27 and/or when treated in apparatus of any one of claims 1 to 21 .