NL8105828A - Part-baked bread vacuum-packed in protective gas - is inserted in pack whilst hot, and cooled by rapid evacuation to maximise shelf life - Google Patents

Abstract

The process is intended for increasing the shelf life of partly baked and packed bread whereby, after partly baking, the bread is inserted into the pack, the pack then evacuated, a protective gas (e.g. carbon dioxide with or without nitrogen) introduced, after which the pack is sealed. The bread is inserted into the pack immediately after baking whilst still hot and is cooled by the subsequent evacuation, preferably to below 5 kPa within 10.s. The description contains details of tests using different bread preparation recipes, gas introduction and sealing methods, and storage conditions.

Description

t VO 2652 -1-

Method for improving the shelf life of packaged bread that is not completely baked.

The invention relates to a method for improving the shelf life of partially baked packaged bread, wherein the bread is placed in the packaging after baking, then the packaging is vacuumed, then rinsed with a protective gas and finally the packaging is hermetically closed.

Partially baked packaged bread, further referred to as semi-baked packaged bread, is intended for sale to consumers who further bake it at home in a household oven, the so-called brown and serve. Because in this operation the retrograded starch is again converted into gelatinized starch and because a crispy crust is formed, such a bun is in a number of respects comparable to fresh bread.

In the conventional manufacture of such semi-baked packaged bread, after baking, the bread is placed for at least 30 minutes in a room where it can cool, e.g. from 100 ° C to 30 ° C. The bread is then placed in the package. In order to improve the shelf life of the bread, the package is rinsed with a protective gas before the package is hermetically closed (sealed). According to a known variant, after the bread has been introduced therein, the package is evacuated before rinsing with protective gas.

The shelf life in the brown and serve method is mainly limited by microbial spoilage, thus by the occurrence of mold and by the development of bacterial spores that have survived the baking process.

It has now been found that the necessary cooling of the semi-baked bread can be realized by vacuum suction in the package within a very short time and that the risk of contamination associated with the usual cooling method is thus drastically reduced. The result is a markedly improved shelf life of the semi-baked packaged bread, while at the same time the production process requires less time and space.

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The method according to the invention is therefore characterized in that the bread is brought into the package in a still warm state immediately after baking and cooled therein by vacuum suction.

The invention is applicable to the production of half-baked bread or rolls of all existing types, both of the white bread type and of the brown bread type, as much of the hard bread as of the soft bread type.

The bread is preferably baked at a temperature of about 200 ° C for a time period of 8 to 20 minutes.

The time between kneading the ingredients and baking, in which the bread is allowed to rise, is preferably kept as short as possible.

According to the invention, the bread is taken out of the oven after baking and immediately placed in the package while it is still warm, after which it is immediately vacuumed. Preferably, a reduced pressure below 5 kPa is realized within 10 seconds.

The deeper the vacuum, the faster the bread cools and the air and water vapor formed are removed. To prevent condensation on the package, it may be recommended to keep the package or the entire vacuum chamber at a slightly elevated temperature, eg about 60 ° C. Although multiple rolls are possible in one package, the best results are obtained when only one roll is used per package.

After the vacuum operation, rinsing is carried out with a shielding gas.

Examples of suitable shielding gases are CO 2 and / or mixtures thereof. A shielding gas containing CO 2 is preferred, as it inhibits the development of microorganisms. Sometimes the shielding gas preferably consists exclusively of CO 2 gas, although the co-presence of e.g.

N2 may be preferred in case the package has some CC permeability.

The subsequent seal stage is fully known per se and will not be discussed further here.

The invention is further elucidated on the basis of a number of test series.

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Trial series I

The tests were carried out with both white bread rolls and wholemeal bread rolls. In preliminary tests, it was first checked which recipe was suitable for the research.

All preservative gases were used: carbon dioxide and mixtures of carbon dioxide and nitrogen in the ratio 70:30 and 50:50.

For comparison, tests were also carried out with nitrogen and air.

Tests were carried out with two modes of packaging: vacuum packaging, in which the packaging is first evacuated before being rinsed beforehand with the protective gas and so-called flow-pack, rinsing only before the packaging is sealed.

Choice of the recipe and preparation process of the rolls a. White bread 15 All tests were carried out with a top patented flour. To determine which recipe was most suitable, rolls were baked according to a hard bread and a soft bread recipe. The recipe for hard bread contained 2% improver for hard bread and 5% yeast, for soft bread 6% milk powder, 6% white bread cream and 6% yeast (counting 20 counts based on the flour content).

Both kinds of rolls were baked at about 200 ° C for 10 minutes. They were kept for one day before baking. Baking was done at about 230 ° C for 5 minutes. Both sandwiches were then sensory assessed. It was found that the crust properties of the bread were valued higher according to a hard bread recipe than that of the soft bread. The quality of the bun was further improved by adding 2% white bread cream. Further tests were therefore carried out with the following recipe in parts by weight and method: flour 100 30 water 56 yeast 5 salt 2 improver for hard bread 2 white bread cream 2 In some tests, a pesticide, calcium acetate, was additionally added; the addition was 0.2% based on the flour. This 8105828-4 additive gives reasonable protection against ling, while the taste of the acetate was not yet a nuisance.

Starting from 1200 g of flour, the dough was kneaded in a Stephan kneader, type UMTA 10. The preparation process was as follows: 5 kneading 90 s bulb 30 min. Proofing approx. 60 min. Baking time approx. 10 min.

dough temperature 30 ° C

10 proofer temperature 30 ° C

oven temperature 200 ° C

b. Wholemeal bread rolls

The tests were performed with Tarvo whole wheat flour. Just as was the case with white bread, good results were obtained if white bread cream was added in addition to a hard bread improver. The recipe (in parts by weight) and the method by which the storage tests were carried out were as follows: wholemeal flour 100 water 64 yeast 5 salt 2 hard bread improver 2 white bread cream 2 In some tests, a pesticide, calcium acetate, was additionally added. The addition, the taste of which was not yet perceived as a nuisance, but which still gave some protection, was 0.2% based on the flour.

Kneaded in a Stephan kneader, type UMTA 10; the working method was as follows: kneading 2 min. ball gray 30 min. proofing approx. 50 min. baking time approx. 10 min

35 dough temperature 30 ° C

proofer temperature 30 ° C

oven temperature 200 ° C

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The packaging and the packaging material

The packaging was done in two ways: - a vacuum-sealing method, whereby the opened packaging with the half-baked bread roll is vacuumed (a pressure of 4 kPa was reached in a time frame of 6 seconds) before rinsing with the shielding gas. Then it is sealed. In the tables of results, this method is indicated by V.

- a flow-pack seal method. In the opened package with rolls, protective gas is blown so long that it has displaced the air present. Then it is sealed. This method is denoted by F.

One-sided saran-coated cellophane bags of 165 x 265 mm from Sidac, Utrecht were used as packaging material.

In the storage tests, the water vapor permeability was found to be such that the weight loss of the package was approximately 2% in one month (25 ° C and an average RH of 40%).

Bottle gas of food grade, i.e. with a negligible bacterial count, was always used as the gas. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 8 105 828

Storage test design 2

For each storage test, 10 packs with 3 rolls each were used. Periodically, it was checked how many packages were still in good condition. The inspection for mold was initially done visually; when in doubt, the rolls were examined microbiologically 6. At the end of the storage test, 7 packages in good condition were assessed for odor and a number of rolls were also baked 8. The evaluation for odor was mainly aimed at detecting development of ling.

10

In total, 4 series of storage tests were carried out.

11 a. The influence of the method of packaging.

12

Buns were packaged according to the two aforementioned 13 methods. In the flow-pack-seal method, the roll must first be cooled for 14 before it is packed. This is not necessary with the vacuum seal method 15, because the roll is cooled very quickly to about 30 ° C during vacuum suction by evaporating water. Therefore, with this method, both after cooling for 30 minutes (indicated in the results table denoted by K) and packed directly from the oven (denoted by W).

In addition, in order to check the influence of a post-contamination, a test was carried out in each method that involved conscious contamination.

This was done by lightly dusting the rolls with flour. In the table of results this is indicated by B, in contrast to the method in which as much post-contamination as possible was prevented (0).

These tests were performed with CO 2 as a shielding gas.

These experiments were stored at 25 ° C.

10 b. the influence of the type of gas.

This series of storage tests has been carried out with rolls that were packed immediately after baking according to the vacuum sealing method. One series was performed in which post-contamination was prevented as much as possible (0), another in which post-contamination was deliberately applied by dusting with flour (B). The tests were performed with CO 2, mixtures of CC> 2 and 70:30 and 50:50, and air. When using air, the variant in which the rolls were contaminated is omitted.

c. storage tests with white and brown bread.

The following variants were tested in this series of tests: - addition of the longitudinal pesticide calcium acetate; - accelerating the baking of the rolls by storing them at 0 ° C for 2 days; - after packaging, post-sterilize for 8 minutes at 120 ° c. The core temperature then became 90 ° C.

One day after packaging, the oxygen content of 10 packages was determined.

The rolls were stored at 20 ° C. After storage for 4 weeks, the rolls were assessed for mold growth. The oxygen content of the package was determined. The sandwiches were judged for odor, especially the occurrence of ling. A number of sandwiches were baked and then sensory assessed.

d. The same tests as under c were carried out at a storage temperature of 30 ° C.

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Results

The results are summarized in Tables 1 to 4.

Table A shows the results of the tests with the different packaging methods. All packages containing deliberately contaminated rolls showed mold growth after 3 weeks (runs 2, 4 and 6). Of the other packages, these had the best shelf life according to the vacuum-seal method; after both hot and cold packaging (tests 1 and 3) the shelf life was 4 weeks or longer. After 5 weeks, however, more than half of the cold-packed bread rolls were no longer in good condition. 10 The shelf life with a flow-pack-seal packaging was considerably shorter (test 5). This table also includes a test in which nitrogen was packaged. The protective effect of CO 2 appears from a comparison of test 7 with test 3: with CC> 2 a shelf life of 4 weeks, with only one week.

15 Striking was the slow growth of mold spots once present, which we attribute to the low oxygen tension. In addition to fungal spots, small white dots often appeared on the crust. These turned out to be wild yeasts in microbiological research. Gas evolved in some packages, including Test 5, causing them to inflate.

Regarding the odor, a number of differences could be observed. In all tests, including in the other series, a sour smell developed, reminiscent of yeast. This odor disappeared upon baking. Packaging with only this odor as the only deviation is marked in the table in good condition. Moreover, there are indications that this odor development decreases as the bun is baked better before packaging. When mold, no matter how minor, occurred, the smell was musty. In some cases, a rotting odor developed and, finally, ling was also observed in some experiments, including 30 packages in which gas had evolved.

Table B shows the results of the storage tests with different gases. Packed according to the vacuum seal method, immediately after baking. The shelf life of all the gases used was good if the bun was not contaminated (tests 1, 8, 10, 12 and 14). If this were the case, the shelf life was only a few weeks, if the package contained CO 2 or mixtures with CC 2 (tests 2, 9 and 11), and 8105828 -8- less than one week if used (test 13). These tests demonstrate the protective effect of CC2. The results are inconclusive as to the minimum percentage of CO 2 that is necessary for an adequate shelf life; 100% CC ^ did not give a significantly better result than 50% CO ^ and 50% ^.

The packages with 100% CO ^ slowly but surely evacuated · Those with mixtures of CO ^ and ^ to a lesser extent. Packages with air and ^ will not shrink.

In these first two test series, relatively little attention was paid to the gas density of the seal and the oxygen tension was also not measured, because the measuring device was not yet available. It is assumed that mold has occurred in a number of packages due to somewhat leaky packaging.

Table C shows the results of the storage tests at 20 ° C with both white and brown bread. In this test series, too, it was packaged directly from the oven in CC2 according to the vacuum seal method. After 4 weeks of storage, all packages were still in good condition.

When checking the oxygen tension, it was found to be less than 1% in all cases one day after packaging. After 4 weeks 20, in a number of packages, an oxygen tension was greater than 5%.

It is suspected that gas diffusion occurs especially at the seal. This explains this higher oxygen tension. It was also noteworthy that the typical sour smell with packaging with a higher oxygen tension was less than with packaging with a lower oxygen tension. Fragrance components may also diffuse from the package.

Sterilization showed that the packaging was not resistant to the high temperatures. This is confirmed by the high oxygen tension measured in those packages after 4 weeks. Despite this, all packages were in good condition after 4 weeks of storage.

Table D shows the results of the storage tests at 30 ° C

given. Of the 10 packages, 6 were rejected after 4 weeks, of which 4 due to a long odor, 1 due to a rotten odor and 1 due to mold (sterilized, probably a leaky package). The packages containing a pesticide were all in good condition.

35 The following experiences were gained in assessing the bread rolls baked after storage. The slightly acidic air almost completely disappeared during baking. The eating properties of the white bread crust are good. The crumb is tender and fairly similar to fresh bread. The smell of the bun is clearly different from that of fresh bread. In addition, with brown bread it was experienced that the bran had a somewhat stale taste.

An investigation into the nature of the fungal growth that sometimes occurred showed that this concerned the chalk fungus (Trichosporon variable), which is common in bakeries.

10 Evaluation - A method in which the packaging is evacuated before flushing with shielding gas is preferable to a flow-pack method.

- To limit post-contamination, pack as soon as possible after baking. The rolls are cooled in the package by drawing the vacuum. Then sterilization is not necessary.

- With this method of packaging, a shelf life of 4 weeks can be achieved even in air. The use of CX ^ provides additional security.

- When using CO ^ the necessity of a support gas, e.g.

20 N £, depending on the CC ^ density of the package. The closer the packaging is, the less the need for a support gas.

- A sour smell develops in the packaging. The odor can be reduced by baking stronger before packaging. The off-odor disappears during baking. The odor can also be influenced by choosing a package with a certain gas permeability.

- In the summer it is recommended to use a pesticide.

- Preferably a hard bread recipe should be used. A soft bread recipe gives a too brittle crust when baking. 1 8105828

Table A. Influence of the manner of packaging on the shelf life.

Tasting with white bread, contaminated (B) and uncontaminated (0). 10 packages were used per test; the table shows the number of packaging that is still in good condition. All experiments were stored at 25 ° C.

«-10- kept for several weeks test type vacuum / warm / contaminated / ---- no. Gas flow pack cold uncontaminated 1 2 3 4 5 1 C02 VWO 10 10 10 9 9 2 C02 VWB 9 8000 3 C02 VK 0 10 10 10 10 4 5 4 CC> 2 VKB 95000 5 CC> 2 FK 0 10 1 4 4 1 0 6 CC> 2 FKB 10 0 0 0 0 10 7 N2 VK 0 10 2 0 0 0

Table B. Influence of the gas on the shelf life. Tasting with white bread.

All rolls were immediately packed in gas after baking, vacuum drawing, contaminated (B) and uncontaminated (O). 15 10 packages were used per test. The table shows the number of packages that are still in good condition.

_ Λ _, number of weeks retained test type besI, et / uncontaminated -, - "r- 3SS 1 2 3 4 5 20 1 CO2 O 10 10 10 9 9 2 B 9 8 0 0 0 8 CO2 / N2 70 / 30 O 10 10 9 9 9 9 B 10 9 7 0 0 25 10 co2 / N2 50/50 0 10 10 10 10 9 11 B 10 7 6 0 0 12 N2 O 10 9 9 9 6 30 13 B 4 0 0 0 0 1 2 8105828 air O 10 10 10 10 7 2 B _____ -11-

Table C. Storage tests with white and brown bread at 20 ° C. Tests were performed with the addition of calcium acetate, with sterilization after packaging and with accelerated aging by first storing at 0 ° C for 2 days and without these measures. Per 5 test 10 packages, assessed after 4 weeks of storage.

test white / calcium-sterilized number of number of brown acetate no. gaskets approved C> 2> 5% approved 10 16 W - 3 10 17 W x - 4 10 18 W - x - 8 10 19 W x 5 10 15 20 B - - - 4 10 21 B x - 3 10 22 B - x - 8 10

Table D. Storage tests with white and brown bread at 30 ° C. Tests were performed with the addition of calcium acetate, with sterilization after packaging and with accelerated aging by first storing at 0 ° C for 2 days and without these measures. 10 packages per test, assessed after 4 weeks of storage.

test white / calcium sterilized aged number 25 no. brown acetate gaskets in good C> 2> 5% state 23 W 5 9 24 W x - 6 10 25 W - x - 9 9 30 26 W - x 4 10 27 B - - - 3 7 28 B x - 3 10 29 B, - x - 7 9 8105828 -12-

Trial series II

In test series I on the shelf life of half-baked packaged rolls, it was stated that a storage of such rolls developed in the package was a rather characteristic sour odor. The cause of this odor is unknown. The influence of the duration of the pre-process and the baking conditions on the development of this odor has been investigated.

Formulation and Methods The tests were performed with white bread rolls. The formulation is the same as that stated in test series I. The method also corresponded to the one mentioned there, although this preliminary process was varied when the preliminary process was examined and the duration of the baking under baking conditions.

Immediately after baking, the rolls were packed in CO in one-sided saran-coated cellophane bags, as indicated in the above report. The rolls were assessed for odor by a panel of test bakers after 3 weeks storage at 30 ° C.

20 Trial design a. Duration of the preliminary process.

Compared was a process of dividing and bulging (short) immediately after kneading and a process of giving 2 x 30 minutes of balling (long) after kneading.

25 b. Duration of baking.

Sandwiches with a baking time of 8 minutes (short) and 20 minutes (long) were compared.

Results 30 The results are summarized in table Ξ. Remarkably, when using a long pre-process, the sour odor was much more pronounced than when using a very short proving process. A very short baking time resulted in a sweet, sweet air with three sandwiches. One of the rolls had a few black dots on the side. With a long baking time of 35 ', the buns had a pretty good smell.

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The conclusion is that a short pre-process and a relatively long baking time, at a low temperature, are the best conditions for preparing semi-baked rolls.

5 Table E. Influence of pre-process and baking time on the development of odor with semi-baked bread. Assessed after 3 weeks storage at 30 ° C. 10 packages per test.

number of approved comments regarding odor 10 short 10 pre-process ----— long 10 4x sour odor x) short 9 3x woe odor baking time ---— long 10 lx sour odor 15 x) lx black dots on the crust.

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Claims (2)

1. A method for improving the shelf life of not fully baked packaged board, wherein the bread is put into the packaging after baking, then the packaging is vacuumed, then rinsed with a protective gas and finally the packaging is hermetically closed characterized in that the bread is brought into the package in a still warm condition immediately after baking and cooled therein by vacuum suction. A method according to claim 1, characterized in that a reduced pressure below 5 kPa is realized within 10 seconds. 3. Process according to claim 1 or 2, characterized in that CO 2 or a CO 2 / N 2 mixture is used as the shielding gas. &&&&&& 15 8105828