GB1592148A - Food process - Google Patents

Abstract

The baked articles are baked in a packaging made of flexible impermeable film which acts as an aseptic block and is provided with ventilation apertures. The ventilation apertures are sufficiently small to prevent infection during cooling. After cooling, the apertures are sealed and the sealed pack is heated to pasteurise the contents. The maximum size of each aperture amounts to approximately 0.5 cm. The apertures are formed by slots or perforations in the wall of the film, or by slots which are formed by breaks in a sealing seam of the package.

Description

(54) FOOD PROCESS (71) We, UNILEVER LIMITED, a company organised under the laws of Great Britain, of Unilever House, Blackfriars, London E.C.4, England, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to packaging baked goods and in particular part-baked bread, buns, cake and like baked goods made from dough or pastry prepared from flour and to processes for their preparation.

Bread normally goes stale within a few days of being baked, the crust becoming soft and conversely the crumb becoming hard. It can be stored for longer periods at deep-freeze temperatures, e.g. -20"C or below, but staling occurs, albeit more slowly, even at these low temperatures. Bread can also be part-baked and stored in this condition until the customer is ready for it, when it is given a short, second bake forming a brown crust. Similar considerations apply to other baked goods, whether prepared from a dough base or a pastry base, for example Danish and puff pastry or a batter base, e.g. cakes.

Whatever the method employed, it is highly desirable to protect baked goods in storage from the effects of moisture, air and contamination by micro-organisms, and to this end methods have been proposed in which the goods are baked wrapped. The present invention provides a packaging process enabling wrapped baked goods to be stored for prolonged periods in suitable conditions, with markedly little deterioration and, in particular, to be stored in a part-baked condition, from which they can be restored by a second baking to a substantially fresh condition.

Our British Patent 1,550,000 provides a process for the preparation of baked goods having an improved shelf-life, comprising baking the goods enclosed in a foil package, permitting vapour to pass during baking and cooling through at least one small aperture in the package seam and thereafter hermetically sealing and heat-pasteurising the packaged goods. Each aperture is smaller than the length thereof through the seam.

The present invention is based on the discovery that bigger apertures may still be small enough to limit the extent of infection during cooling to provide aseptic packaging after sealing the apertures and pasteurising the package content.

The present invention therefore provides a method of packaging baked goods aseptically wherein the goods are baked in a package comprising a flexible impervious foil providing an aseptic barrier and furnished with vent means for the relief of pressure across the walls of the package, wherein each said vent means is at most 30 m.m. across but less in depth and after cooling sealing said vent means and heating the sealed package to pasteurise the contents thereof.

The greatest distance across each vent is preferably 0.5 cms, particularly 0.1 to 0.5 cms.

The operation of the invention is as follows: dough or other starting material is baked in a foil package furnished with vents permitting vapour to pass, especially water vapour, for example through one or more small holes in the package during baking and subsequent cooling to prevent the package in turn bursting and collapsing. The package is then allowed to cool before being hermetically sealed, the package material providing an aseptic barrier.

Any condensed vapour which would otherwise have provided an active substrate for the proliferation of harmful micro-organisms is rendered inocuous by heat-pasteurising the sealed package. In this second heating operation comparatively little vapour is generated, insufficient to burst the sealed package.

The severity of conditions for post-pasteurisation that can be applied after sealing the package is limited to the strength and heat-resistivity of the package and is necessarily less than that for example of sealed cans. The conditions required are determined by the extent of infection that takes place during cooling, which is found to condescend upon the size, nature and number of the apertures ventilating the package on cooling. The statistical significance of a limited number of failures can also be taken into account in deciding these characteristics of the apertures, since if a consistently small but finite proportion of failures be accepted then a more convenient method of applying the invention may be possible. It is also relevant to take into account and if necessary control the infectiveness of the ambient atmosphere surrounding the package itself, although it is assumed that the packaging zone is never sterile.

It is surprising that the size of the vents could have a bearing on the extent of infection introduced during cooling, when the amount of air sucked in will be the same other things being equal, whatever the size of hole. It is further surprising that substantially bigger apertures can be used than those described in our above patent specification and that they may be provided by holes in the wall of the pack as an alternative to the channels or ducts across the seam joining the top and bottom parts of the package, as described in that Application. By the use of bigger vents greater flexibility of operation is possible. Vent means through the wall of the package instead of a closure seam may be provided beforehand, in the sheet foil or film from which the package is prepared, and standard methods of construction of the package may be used. Bigger vent means through a sealing seam than those disclosed in our above patent specification lend themselves well to simple methods of packaging construction and sealing techniques. It may for example be suitable to arrange vent means in the form of slits, as preferably multiple interruptions in a closure seam extending along an entire wall of a package of roughly rectangular form. Each interruption is then preferably not more than 30 mm in length to minimise the possibility of the vent gaping wide due to the structural weakness of the sheet foil or film. Nevertheless, since the length of the slits provided by the interruptions is relatively great, less critical means are required for their preparation. Vents through the seam may also be provided in accordance with the invention following the methods disclosed in our above patent specification by suitably sized formers laid across the seam direction between the top and bottom parts of the package and withdrawn after the seal is formed or in the case of open tubes used as formers, left in the seam.

The vents can be sealed after cooling by for example applying a patch, or sticking together with adjacent material surrounding each vent. Interruptions in a closure seam may be sealed by pressure over the seam.

Effective protection from contamination after baking may instead be provided by hermetically sealing the package in an outer container, for which a wide range of material is suitable, including plastic film, for example hydrocarbon polymers such as polypropylene, other film-forming polymeric substances, for example acrylic and vinyl polymers and coated regenerated cellulose derivatives, most of which can be heat-sealed. The limited pasteurisation conditions required permit the use of sealing means less resistant to heat than the packaging foil itself. Suitably the foil material comprises laminated polyolefin/poly-ester or -amide retaining its shape during baking. The heat resistant and impervious requirements it must meet necessitates the use of expensive material for the package foil but with the use of vents to relieve the pressures generated by baking and cooling, very thin material may be used, and the package may comprise a deep-drawn tray and lid combination, made from laminated sheet from 50 to 250 microns in thickness and still capable of withstanding the moderate pasteurisation conditions made possible by the limited infection during cooling using the vents of the invention.

Baking temperatures for the preparation of part-baked bread and similar leavened goods are preferably 100 to 2000C, for periods preferably from 30 minutes to 1B hours, particularly 100 to 175"C for from 40 to 75 minutes, e.g. 120 to 1600C for about an hour, the precise conditions being insufficient to confer a browned appearance to the product. Preferably the temperature is permitted to fall by 20"C to 30"C during baking. Part-baking should be sufficient to confer rigidity to the product and prevent its collapse and to effect complete gelatinisation of the starch content, at the same time ensuring that the action of the leavening agent is completed and arrested. The water activity of the baked product, at least for bread should not exceed 0.96.

It is preferred to effect at least part of the proving of leavened dough products in the package, sufficient space therefore being left in the package for this purpose.

After proving, the dough is preferably baked with progressive fall in temperature for 40 to 75 minutes.

Preferably the interior of the product is made commercially sterile by the baking operation. In conventional baking or part-baking of leavened goods the combination of temperature and time normally is insufficient to ensure that the interior is made sterile.

Interior temperatures of at least 900C and preferably in the region of 100"C are desirable according to the present invention for a period of at least 30 minutes. It may be necessary in order to ensure that the goods are made homogeneously commercially sterile, to obtain temperature measurements in the interior of the products. It will be understood that by commercially sterile is meant a condition in which while all bacteria may not necessarily be absent, severe pasteurisation has been effected, and substantially only spore-forming bacteria can remain.

After cooling to permit the water vapour to condense, preferably lasting at least 10 minutes, more preferably 20 minutes, the package of wrapped, baked dough is sealed by closing each aperture or enclosing in a container providing an outer covering impervious to air moisture and bacteria and the whole then heated to pasteurise the contents of the container. Vapour should not escape into the outer pack if this is used, while packing otherwise a partial vacuum is generated likely to lead to the collapse of the pack. The cooling step should ensure that this precaution is taken.

The package and its contents are pasteurised by heating, preferably to at least 750C, especially about 90"C but preferably not more than 110 C, for a period of preferably up to 1 hour, at least 10 minutes, preferably at least 2 hour and especially about 4 hour; principally destroying bacteria, moulds and other micro-organisms present between the films and any that may have entered the inner wrapper. Pasteurisation may also be effected by infra-red heat treatment. These temperatures are oven interior temperatures.

It is a surprising feature of the invention that, providing the baking conditions realise a water activity at or below 0.96%, no spore growth is evident in part-baked bread, when packaged in accordance with the invention, even after storage for several months at ambient conditions, e.g. 10 to 25"C. Such growth soon appears in bread baked in open conditions, even with lower water activity than this.

Shelf-life of the products of the invention may be enhanced by including accepted preservative in the dough or whatever comestible material is baked. Thus, acetic acid and/or acceptable acetates, e.g. calcium acetate, may be included in suitable amount.

The invention is suitable for the preparation both of part- and fully-baked leavened and unleavened goods such as bread, buns, cakes, scones, muffins, crumpets and pastries. The invention may also be applied to the preparation of packaged cooked meals in predetermined portions which may or may not include baked goods. It is applicable, therefore, to the packaging of cooked comestibles generally.

Several inner packages may be sealed within a common outer container for them all. The wrapping inner package and/or outer container may consist of a preformed bag closed by folding/sealing the mouth, as the case may be. Alternatively, each or both may be formed by wrapping sheet material around the product and inner pack. Again, the inner package and outer container may be made by thermal forming, the outer at least being heat-sealed at its overlapping edges. Either or both may be made from transparent material. The outer container may be made of laminated material combining strength and imperviousness, e.g.

of aluminium, polyolefine and vinyl or polyamide sheets laminated together.

The amount of space occupied in the outer container by the inner package or packages is not critical but it is preferable to avoid cramming.

Example 1 Dough was prepared by kneading together the following ingredients for 20 minutes at 27"C in the parts by weight indicated: 50 Bread flour 2.5 Yeast 1 Salt 1.25 Sugar 1.5 Fat 22.8 Water Rolls weighing about 55 grams each were prepared from the dough and packed six at a time into gas and water-vapour impermeable trays, deep-drawn from polyvinyl chloride sheet and provided with a lid of similar material provided with a vent 0.3 cm diameter, which was then sealed on by high frequency means, to provide an otherwise hermetically sealed container. The dough was proved at 30"C with a relative humidity 80 to 85% for 35 minutes.

After proving the trays were put in a continuous belt oven for 60 minutes. The temperature profile through the belt oven was as follows: First 4 : 138 - 140"C Second-: 142 - 144"C Third-: 140 - 142"C Last : 120 - 122"C.

The interior of the pack reached a temperature of 90"C for a period of more than 30 minutes. The baked products were cooled for 20 minutes at a temperature of approximately 24"C. An adhesive patch was then applied over the hole.

After a cooling period of 10 minutes or more the sealed, packaged containers were placed on the belt of a pasteurisation oven and pasteurised for 45 minutes, with an air temperature inside the oven of 95"C.

After pasteurisation the products were cooled for at least 1 hour and then packed in cartons. The rolls were firm but white and were stored at 10 to 20"C for a month. They were then unpacked and baked briefly to confer a brown surface crust. The rolls were then tasted and pronounced satisfactory by a tasting panel.

Example 2 The following ingredients for the preparation of French bread were kneaded together as described in Example 1, but at 25"C and the dough was proved in bulk for 20 minutes at 24"C:- 25 Untreated bread flour 1.25 Yeast 0.50 Salt 0.3 Fat 0.4 Sugar 12.5 Water A second proving was carried out for 20 minutes at 28"C with a relative humidity of about 75% on balls of the dough weighing about 210 grams each. The dough pieces were then formed into the final shape of French sticks and packed in a tray as described in Example 1.

The hole in the lid as before was however nearer the edge to admit air in the restricted passage between the lid and the flanged edge of the tray adjacent the seam.

A final proving in the trays was carried out for 40 minutes at 30"C with a relative humidity of about 85%. The pieces were then baked in the packs for 50 minutes in a belt oven with the following temperature profile: First 4 of the oven: 150 - 155"C Second 4 of the oven: 145 - 1500C Third a of the oven: 140 - 145"C Last 41 of the oven: 120 - 125"C.

Similar internal temperatures were reached as in the previous Example.

The packs were cooled for 20 minutes at about 25"C and sealed as before by applying a patch over the hole in the lid.

After a cooling period of at least 10 minutes the sealed containers were pasteurised for 45 minutes in an oven at a temperature of 95"C. After pasteurisation the products were cooled for at least one hour and then packed in cartons. As before, after storage and final baking to provide a brown crust, the sticks were found excellent to the taste.

Claims (17)

WHAT WE CLAIM IS:

1. Method of packaging baked goods aseptically wherein the goods are baked in a package comprising a flexible impervious foil providing an aseptic barrier and furnished with vent means for the relief of pressure across the walls of the package, wherein each said vent means is at most 30 mm across but less in depth and after cooling sealing said vent means and heating the sealed package to pasteurise the contents thereof.

2. Method according to Claim 1 in which the greatest dimension of each vent is 0.5 cm.

3. Method according to Claim 2 in which the greatest dimension is 0.1 to 0.5 cm.

4. Method according to any of the preceding claims in which the vents comprise channels and ducts constituted by interruptions in a closure seam of the package.

5. Method according to Claim 1 in which the vents comprise one or more slits through the package wall.

6. Method according to Claim 5 in which the vents each comprise crossed slits.

7. Method according to any of the preceding claims in which the package is sealed in an outer container.

8. Method according to any of the preceding claims in which the foil comprises a laminate of polyester/polyolefine synthetic resin.

9. Method according to Claim 8 in which the package comprises a deep-drawn tray and lid therefor.

10. Method according to any of the preceding claims comprising pasteurising the sealed package by heating at a temperature from 75 to 1100C.

11. Method according to any of the preceding claims in which the goods comprise dough which is packaged and part-baked in the package.

12. Method according to Claim 11 wherein the dough is baked in the package at a temperature providing a minimum internal dough temperature of 90"C for at least 30 minutes and a maximum water activity of 0.96.

13. Method according to Claim 12 in which the dough is baked to a temperature from 100 to 200"C for a half to 12 hours.

14. Method according to Claim 3 in which the dough is baked to a temperature from 120 to 1600C for about an hour.

15. Method according to any of the preceding Claims 11 to 14 in which the baking temperature is permitted to fall by from 20 to 300C during baking.

16. Method of packaging baked dough products as claimed in Claim 1, sealed in the package substantially as described with reference to Example 2.

17. Packaged cooked baked food products whenever produced by a method as claimed in any of the preceding Claims 11 to 16.