Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
534~
This invention relates to packaging baked goods
and in particulax 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. -20C 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 desi-
rable 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 pxolonged 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.
-2- ~e - `~ ' . '
1~Ca'7~3~
Our co-pending Canadian Patent Application No.
250,566 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, thereafter hermetically sealing
the heat-pasteurizing the packaged goods, wherein the mean-
free path of each aperture is smaller than the length there-
of.
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 pasteurizing the
package content.
The present invention therefore provides a packag-
ing of 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 located in
the walls of the package for the relief of pressure, wherein
the said vent means are small enough to limit infection on
cooling while having a mean-free path larger than the length
thereof and the length thereof is not more than 30 mm and
after cooling sealing said vent means and heating the sealed
package to pasteurize the contentsthereof.
The mean-free path is the greatest width across
the mean cross-section of the vent.
The operation of the invention is as follows:
dough or other starting material is baked in a foil package
furnished
B~
7534
with vents permitting vapour to pass, especially water
vapour, for example through one or more small holes in the
package during baking and subReguent cooling to prevent
the package in turn bursting and collapsing. The package
is then allowed to cool before being hérmetically 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 compara-
tively little vapour is generated, insufficient to burst
the sealed package.
The severity of conditions for post-pasteuriza-
tion that can be applied after sealing the package is
limited to the strength and heat-resistivity of the pac-
kage 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 fail-
ures 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 ......
--4--
q~
7534
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 b used than those described in our co-pending
Canadian Application No. 250,566 and that they may be pro-
vided by holes in the wall of the pack as an alternative tothe 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 in-
stead 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 co-pending Canadian Application No. Z50,566 also lend
Z0 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 mul-
tiple 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 minimize the possibility of the vent gaping wide due to
..
753~
the structural weakness of the sheet foil or film. Never-
theless, since the length of the slits provided by the
interruptio~ is relatively great, less critical means are
required for their preparation. Vents through the seam
may also be provided in accordance with the invention fol-
; lowing the methods disclosed in Canadian Application No.
250,566 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 forexample applying a patch, or sticking together with adja-
cent 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 vinylpolymers and coated regenerated cellulose derivatives, most
of which can be heat-sealed. The limited pasteurization
conditions required permit the use of sealing means less
resistant to heat than the packaging foil itself. Suitably
the foil material comprises laminated polyolefine/poly-ester
or -amide retaining its shape
B.
.
~75;3~
during baking. The heat resistant and impervious require-
ments lt must meet necessitates the use of expensive mate-
rial 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 com-
prise 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 pasteurization
conditions made possible by the limited infection during
cooling using the vents of the invention.
saking temperatures for the preparation of part-
baked bread and similar leavened goods are preferably lO0
to 200C, for periods preferably from 30 minutes to l l/2
hours, particularly lO0 to 175C for from 40 to 75 minutes,
e.g. 120 to 160~C 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 20C to 30C during baking. Part-baking should be
sufficient to confer rigidity to the product and prevent
its collapse and to effect complete gelatinization 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, suffi-
cient space therefore being left in the package for this
purpose.
~ fter 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 conven-
tional baking or part-baking of leavened goods the
-7-
~97~3~
combination of temperature and time normally is insufficient
to ensure that the interior is made sterile. Interior
temperatures of at least 90C and preferahly in the region
of 100C 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
pasteurization has been effected, and substantially only
spore-forming bacteria can remain.
After cooling to permit the water vapour to con-
dense, 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 con-
tainer providing an outer covering impexvious to air, mois-
ture and bacteria and the whole then heated to pasteurize
the contents of the container. Vapour should not escape
into the outer pack if this is used, while packing other-
wise 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 pasteurized by
heating, preferably to at least 75C, especially about
90C but preferably not more than 110C, for a period of
preferably up to 1 hour, at least 10 minutes, preferably
at least 1/2 hour and especially about 3/4 hour; prin-
cipally destroying bacteria, moulds and other micro-
organisms present between the films and any that may haveentered the inner wrapper. Pasteuri~ation may also be
effected by infra-red heat treatment. These temperatures
are oven interior temperatures.
534
It is a surprising feature of the invention that,
providing the baking conditions realize 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 25C. 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 prepa-
ration 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/ox 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 over-
lapping 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 lami-
nated together.
The amount of space occupied in the outer container
_g _
;3~
by the inner package or packages is not critical but it is
preterable to avoid cramming.
EXAMPLE 1
Dough was prepared by kneading together the fol-
lowing ingredients for 20 minutes at 27C in the parts by
weight indicated:-
Bread flowr
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 circular hole 0.3 cm diameter, which was then sealed
on by high frequency means, to provide an otherwise herme-
tically sealed container. The dough was proved at 30C
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 1/4 : 138 - 140C
Second 1/4 142 144C
Third 1/4 : 140 - 142C
Last 1/4 : 120 - 122C
The interior of the pack reached a temperature
of 90C for a period of more than 30 minutes. The baked
products were cooled for 20 minutes at a temperature of
approximately 24C. An adhesi~e patch was then applied
over the hole.
After a cooling period of 10 minutes or more the
--10--
7~3~
sealed, packaged containers were placed on the belt of a
pasteuri~ation oven and pasteurized for 45 minutes, with
an air temperature inside the oven of 95C.
After pasteurization 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 20C for a
month. They were then unpacked and baked briefly to con-
fer 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 25C and the dough was proved in bulk for 20
minutes at 24C:-
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 28C 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 ad~acent the seam.
A final proving :in the trays was carried out for
40 minutes at 30C 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:-
--11--
~Q7534
First 1/4 of the oven : 150 - 155C
Second 1/4 of the oven : 145 - 150C
Third 1/4 of the oven : 140 - 145C
Last 1/4 of the oven : 120 - 125C
Similar internal temperatures were reached as in
the previous Example
The packs were cooled for 20 minutesat about 25C
and sealed as before by appl~ing a patch over the hole in
the lid.
After a cooling period of at least 10 minutes
the sealed containers were pasteurized for 45 minutes in
an oven at a temperature of 95C. After pasteurization 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.
-12-
