A Treatise on Baking

Reproduced on the FAQ for alt.bread.recipes website

+ The alt.bread.recipes FAQ
Search the FAQ
FAQ Statistics
+ A Treatise On Baking
Wheat and Flour
The Scientific Manufacture of Bread
Essential Factors Influencing Bread Quality
Temperature and Humidity
Rope and Mold
Increasing Bakery Efficiency
Miscellaneous Information
+ Part II

Rope and Mold

[ACH Foods, Inc., the copyright owner, has graciously permitted the reproduction of A Treatise on Baking, by Julius E. Wihlfahrt, in HTML format on the alt.bread.recipes FAQ Web site. You may link to it but you may not republish it in any other venue without written permission of ACH Foods, Inc.]



I. Rope Defined
II. Cause and Source of Infection
  A. Rope is Caused by the Bacillus Mesentericus
  B. Former Exaggerated Views Regarding Rope Infection
  C. Rope Organisms Prevalent in Air and Dust
  D. Yeast Can Not Carry Rope Organisms
  E. Importance of Understanding the Cause and Prevention of Rope
III. Evidence and Characteristics of Rope
  A. Odor and Taste of Loaf
  B. Discoloration of Crumb
  C. Stickiness of Crumb
  D. “Foxy” Crust Color
IV. A Method for Detecting Rope
V. General Precaution Measures Against Rope
  A. Use of Vinegar
  B. General Cleanliness
  C. Removal of Stale Bread
  D. Storage Conditions for Raw Materials
  E. Dough Temperature
  F. Healthy Vigorous Panary Fermentation
  G. Baking
  H. Cooling and Wrapping of Bread
  I. Storage of Bread
VI. Immediate Steps to Be Taken When Rope Appears
  A. Exercise All Precautionary Measures
  B. Changes in Dough Batch,—Conditioning—Baking and Bread Cooling
    1. Vinegar in doughs
    2. Stiffer doughs
    3. Reduction in sugar
    4. More age on doughs
    5. Baking conditions
    6. Cooling and wrapping
  C. Methods of Eliminating Rope Infection Throughout the Bakery
    1. Live steam—treatment of shop and equipment
    2. Formaldehyde treatment
      (a) Washing of floors with formaldehyde solution
      (b) Fumigating with formaldehyde
VII. Investigation of Source of Rope in the Bakery
  A. Examination of Material
  B. Baking Test Method
  C. General Preliminary Procedure
  D. “Check” Dough
  E. “Test” Dough
  F. Examination of Check and Test Loaves
    1. Both sets of loaves exhibiting ropiness
    2. None of the loaves exhibiting ropiness
    3. The case of the development of rope only in the test dough
  G. Importance of Confirmation of Baking Tests by Bacteriological Examination
VIII. Mold Defined and Explained
IX. The Growth and Distribution of Molds
X. Protective Measures Against Mold
  A. General Cleanliness
  B. Baking, Cooling and Wrapping of Bread
  C. Filtered and Washed Air in the Bakery
XI. Mold in Bread Cannot Be Caused by the Ingredients Used

Prevention and Elimination


Rope is the name given to a bread disease which results in breaking down the starch and protein of the loaf producing a discolored and sticky condition in the crumb which is accompanied by a characteristic disagreeable odor and nauseating taste. Ropiness in bread is not noticeable directly after baking but usually makes its appearance from 12 to 36 hours after the bread has left the oven. This bread disease most always occurs during the hot humid months and very rarely during cold winter months.



Rope in bread is caused directly by the growth and development of micro-organisms belonging to the group known as the “bacillus mesentericus” and commonly spoken of as the “rope bacillus.”

The rope bacillus is a tiny rod shaped organism which can only be seen by means of the microscope. The rope bacillus is generally present in a special form known as spores. These rope spores are quite resistant to heat and when contained in bread doughs they can pass thru the oven without being killed and hence are able to develop and grow later on in the baked loaf.

The rope bacillus occurs naturally in the soil and is most frequently present on the outer part of vegetables and grains. This organism is quite generally carried by the potato and for a long time it was spoken of as the potato bacillus.


Formerly, many exaggerated views were held concerning the manner in which bread doughs became infected with the rope organisms. Many people believed that rope would only develop in unclean bakeries and when this disease became apparent, they were very likely to immediately blame the flour as the source of infection. However, an intensive study concerning rope and its development in bread has yielded much enlightening information correcting some of these former views. In some instances, rope has developed in clean bakeries and in many cases it has been found that the flour could not be condemned as the basic cause of this condition.


The rope organisms like other bacteria and mold spores are present to a certain extent practically everywhere in the air and carried by dust particles. If conditions are not particularly favorable to their growth, and they do not occur in abundance, they will not produce any apparent evidence of ropiness.

While flour and certain other raw materials in the bakery may become infected with rope organisms, it is not correct to immediately attribute the source of rope to the flour unless a careful and thorough investigation proves this to be the case.


Incidentally the rope organism will not develop under mildly acid conditions. Because of the fact that yeast is grown on a slightly acidified media, it is obvious that yeast cannot become a carrier of the rope organism. In like manner, the source of rope infection cannot be traced to those malt extracts which contain a small percentage of acid.


In view of the fact that rope is a condition which may appear even in well regulated bakeries and because this bread disease can steal a baker’s business from him like a thief in the night, it is very important for every baker to become familiar with the nature of rope, the conditions which favor its development as well as measures which should be taken to prevent its occurrence and to eliminate it directly after it has first become noticeable. Therefore, this general subject is discussed further in the following paragraphs.



The first indication of a ropy condition in bread is usually the detection of a peculiar unpleasant odor and taste of the loaf resembling that of over-ripe cantaloupe.

This odor and taste is faint during the early stages of the development of rope but becomes stronger and more obnoxious as the rope condition progresses.

Rope usually becomes first apparent in the center of the loaf and later spreads throughout the entire loaf.


In addition to the characteristic odor developed, rope in bread results in a gradually darkening of the crumb which eventually becomes dark brown. This discoloration usually becomes evident in the center of the loaf and gradually spreads through the entire interior of the loaf.


One very significant indication of rope in bread is the development of a sticky, viscous condition of the crumb. If a small portion of the crumb is pressed between the fingers and then pulled apart, it will sometimes stretch readily into long silky strands of web-like threads. This is undoubtedly the reason why this bread disease has been named “rope.”


The crust of a “Ropy” loaf frequently exhibits a “foxy” or peculiar reddish color.


Rope is readily detected by the baker thru the manifestation of the peculiar characteristics and unmistakable evidences of rope described above.

Every baker should maintain a continual “look-out” for the appearance of rope especially during hot humid weather. This can be done as follows:

Three or four loaves of bread should be selected at random from each day’s baking. These loaves should be stored under relatively warm and moist conditions so that if rope is liable to become evident in these particular loaves, it will have the conditions which are most favorable for its development. One loaf should be cut and carefully examined about 12 to 18 hours after baking and another 24 hours later, and still another one day after this,—thus covering a total period of about 3 days. If the odor or appearance of any of these loaves indicates the development of rope, immediate steps should be taken to remedy the situation. Frequently in this way the baker will be able to observe the occurrence of rope through the detection of a faint “ropy” odor before it becomes very pronounced. Thus the baker can take the necessary steps to prevent rope development in other dough batches before it progresses too far or gets out of hand.

If rope does not become apparent in any of these “test” loaves, it has practically no chance of developing during the one or two days’ storage in the home of the customer.



The rope organisms even when present will not thrive or develop “rope” in the finished loaf if there is sufficient acidity in the dough. Hence, in the summer time, the addition of one pint of 90 grain vinegar to each barrel batch of dough is a precaution well worth while especially in shops where there is a tendency toward the development of rope.

If the vinegar is purchased locally, it is advisable to ascertain its strength. The ordinary commercial vinegar sold is usually about “40 grain” in strength. If such vinegar is employed as a preventive against rope, a little more than one quart should be used in every dough containing one barrel of flour. The amount of vinegar used of course, should displace an equivalent quantity of the water ordinarily employed in the dough.

Incidentally, one quart of vinegar weighs approximately two pounds. Thus, if one quart of vinegar is added to a certain dough formula calling for 1 barrel of flour and 120 pounds of water, the amount of water employed with this vinegar should be accordingly reduced to 118 pounds.

The vinegar is added to the dough batch by merely first stirring it into the bulk of the water, thus forming a very dilute solution of vinegar.

To be more specific, the following procedure of mixing should be adhered to:—

  1. Dissolve salt in a small portion of the total water.
  2. Dissolve yeast in another small portion of the total water.
  3. If dried milk is used, it should be dissolved in the proper manner in another portion of the water.
  4. Stir the vinegar to be used in the remainder of the water.
  5. Add the salt solution to the water containing the vinegar and next add the sugar, milk and malt. Mix these together for a few turns of the mixing arms of the mixer.
  6. Start to draw the flour into the mixer.
  7. When the flour is about half drawn in, add the yeast solution.
  8. After the yeast has been incorporated, add the shortening.
  9. Then finish mixing.

The use of vinegar as a precaution against rope will in no way impair any of the qualities of the finished loaf and affords a very easy and effective insurance against the development of rope. It is preferable to use white distilled vinegar for this purpose.


While it is not true that rope only occurs in bakeries which are not kept clean, it is, nevertheless, a fact that tiny particles of old dough in cracks in the floor, wall, machines or pans offer an excellent opportunity for the rope organisms to thrive and multiply. Naturally, where conditions of this sort exist, the doughs are more likely to become infected than where the bakery and all equipment are kept scrupulously clean.

A bakery is not necessarily actually clean because it merely appears to be so to the casual observer. Care should be taken daily to remove all remote traces of dust, dough, grease, flour, crumbs, etc., from the walls, floors and all equipment, through the use of ordinary cleansing agents. Otherwise, the dust arising from such particles of waste material is apt to carry and distribute rope infection throughout the bakery.


Stale bread or other baked goods should not be allowed to accumulate in the bakery, inasmuch as they furnish an ideal breeding place for rope organisms with the attendant danger of spreading.


While the flour or any one other raw material is not necessarily the direct source of rope infection,—it must be kept in mind that these organisms are likely to find their way into such materials and will thrive if proper storage conditions are not adhered to. Cleanliness, proper ventilation, sunlight, and cool temperatures are inhibitive to the development of the rope organisms, whereas, dampness, warmth, the accumulation of dirt and poor ventilation encourages the growth of these organisms.


Warm dough temperatures are more conducive to the development of the rope organism than cooler dough temperatures. This is one of the many reasons for the maintenance of relatively low dough temperature.


The maintenance of a vigorous healthy fermentation and conditioning of the dough batch by the use of liberal amounts of yeast, assists in creating the desired gradual increase in acidity throughout the dough, thus aiding in the prevention of the growth of the rope organisms.


Moisture is one of the factors which encourages the growth of the rope organism. Hence, a condition of ropiness is more likely to develop in an underbaked loaf than in one which has been thoroughly baked out.

From this standpoint alone, it is important to avoid flash heat in the oven which results in the crust forming too quickly. Such a condition necessitates the removal of the bread from the oven before the interior is properly baked and the excessive moisture remaining in the crumb, especially in the summer time, often results in the appearance of rope where it might not otherwise occur.


Bread which is not thoroughly cooled before wrapping is more susceptible to the development of rope than a loaf which has been adequately cooled. Hence, it is always advisable to cool the bread after baking, gradually,—although as rapidly as possible to a point where the interior of the loaf is about 90 degrees F. before wrapping. Electric fans can be used to good advantage in cooling the bread.


Bakery products of course, should be marketed as quickly as possible after baking. However, if bread or other baked goods are packed in baskets, crates, boxes or other containers a few hours before delivery or kept in them after delivery, extreme care should be taken to keep such containers as well as all delivery vehicles scrupulously clean and to avoid holding the bread under warm or humid conditions.



If all of the precautions taken to prevent the occurrence of rope described in the preceding paragraphs are conscientiously followed out,—there is very little chance of rope developing in the resulting bread. However, if in any case, ropiness does become apparent, all of the precautionary measures should be immediately put into practice together with the . modifications and more drastic steps which are described in the following paragraphs.

1. Vinegar in Doughs

While the use of vinegar in the dough batch has been previously described as a preventive of rope,—the amount specified should be doubled in any case where rope has actually been observed. In other words, one quart of 90 grain vinegar or about 2 1/2 quarts of 40 grain vinegar should be used in every barrel batch of dough made up.

2. Stiffer Doughs

When rope has made its appearance it is advisable to set the dough a little stiffer than usual, by using slightly less water in the dough than formerly.

3 Reduction in Sugar

The sugar content of the dough should be slightly reduced, or better still—the sugar used should be replaced by a high grade malt extract which contains a small amount of lactic acid.

4. More Age on Doughs

In shops where a condition of rope has been observed, the doughs should be allowed to age a little longer than usual, inasmuch as the additional acidity created thereby will assist in retarding the development of the rope organisms.

5. Baking Conditions

The bread should be baked out just as far as possible without impairing its softness or other qualities. Usually a slightly cooler oven and a longer baking period will assist toward this end.

6. Cooling and Wrapping

While the rapid and complete cooling of bread prior to wrapping has been discussed as a preventive measure against rope, it is especially important that this point be heeded more strictly than ever, if rope has already appeared.


Just as soon as ropiness has made its appearance in bread, it is necessary to take immediate steps to clean every part of the bakery and all equipment by use of solutions such as vinegar which will be effective in killing or retarding the growth of the rope bacillus. There are several very effective ways of doing this which may be employed jointly or separately, Some methods which have proved successful for this purpose are described as follows:—

1. Live Steam—Treatment of Shop and Equipment

Live steam may be used as a means of cleaning the shop, floors, pans and all general equipment coming in contact with the dough. This live steam should be under pressure and delivered by means of a steam hose. When employed, this steam should be applied to every article being treated for several minutes. The nozzle of the steam hose should be held close to each piece of equipment so as to insure close contact with the hot steam. Steam at 100 lbs. pressure is very hot, namely 338 degrees F. In cases where steam is used, % is important to avoid using steam at a lower pressure because it will not be as hot and consequently not as effective in killing the rope organism. As a matter of fact, steam at only 5 or 10 lbs. pressure lacks force and is not much hotter than the temperature of the interior of the loaf in the ordinary baking process. Such steam therefore, is not hot enough to destroy the rope infection.

2. Formaldehyde Treatment

An effective means of sterilizing the bakery and killing rope infection is through the use of formaldehyde. In severe cases of rope, this treatment is especially advisable, and may be divided in four parts as follows:—


This should be carried out while there is no work going on in the shop. First secure commercial liquid formaldehyde of standard strength (40 % U. S. P.). Mix one part of this with twenty parts of hot water. Scrub the floors of the bakery with this dilute solution, getting it well into all corners and crevices. While the formaldehyde fumes will not injure the machinery, this solution should not be applied to the troughs or other equipment and should not come in contact with any materials. After washing the floors with formaldehyde thoroughly wash the same with hot water.


Fumigating with formaldehyde is best done overnight. Saturday is generally most convenient. Where rope is not too severe, it usually can be checked for a few days by adhering to the instructions previously stated,—until there is no work going on in the shop and then the fumigation

can take place. In order to fumigate the bakery with formaldehyde proceed as follows:—

  1. Close the place up tight.
  2. Burn three large sized formaldehyde candles free from sulphur for every 100 square feet of floor space.
  3. After fumigating, be sure to “air” the shop thoroughly.
  4. Do not permit formaldehyde fumes to come in contact tvith flour or other ingredients.



By closely observing the necessary preventive and curative measures for rope as described in the foregoing paragraphs, it is extremely doubtful that any case of rope will get the best of the baker.

Even though these measures do result in eliminating rope after it has once appeared, it is very important to carefully examine the raw materials and general shop conditions in order to locate the exact cause of the rope infection and to eliminate the same so as to prevent any recurrence of rope.

If any particular material is suspected to be the cause, it is well to set this aside from all other materials and to conduct the trial baking test in order to ascertain whether or not this suspicion can be confirmed.


In order to make clear the method of conducting this test, let us assume that the baker wishes to test out one or specific ingredient which may be under suspicion.

The procedure in conducting these baking tests are described in the following paragraphs.

  1. Select some room outside of the part of the bakery where the commercial doughs are handled, which will be suitable for the making up of small test doughs by hand.
  2. Thoroughly clean, fumigate and then ventilate’ the room.
  3. Select the utensils necessary for the making up of two trial doughs, each of which should be large enough to produce about six loaves.
  4. Thoroughly clean and sterilize all utensils to be used. This can be done by cleaning them and by thorough heating in the oven.
  5. The baker handling these utensils should wash his hands in a disinfectant solution before starting in. His uniform should also be freshly laundered and clean.
D. “CHECK” DOUGH With the exception of the particular ingredient to be tested, all the

materials necessary for the work should be taken from the bakery into the room where the trial baking tests are to be made.

Then a new sample of the particular ingredient under investigation should be secured from some source outside of the bakery. Care should be taken to make sure that the sample selected will not cause rope in bread. One dough large enough to produce several loaves should be made up using this ingredient. This dough should not contain any vinegar and should be moderately slack. It should be handled in the regular way. During the fermentation period and while in the pan it should be covered with a clean sterilized cloth to prevent infection. When placed in the oven the cloth should be removed and care taken to avoid overbaking. After baking the loaf should be cooled, wrapped, and placed in a cabinet where a fairly warm and humid condition is maintained. Thus if rope is at all likely to develop, it will surely do so under these favorable conditions.


Directly after making the first “check” dough as described above, a sample of the ingredient to be tested should be brought into the room from the bakery,—and a test dough made up using this ingredient together with the other necessary materials taken from the same lot as those used in the check dough.

The formula and shop conditions should be same as those employed in the check dough and the same care should be exercised in handling and baking the dough.

The baked loaf should be wrapped in the same manner and placed under similar conditions of temperature and humidity.


After 24 hours, one loaf from each dough should be examined and thereafter at intervals of 12 hours for about three days.

This examination may result in any one of three ways, each of which are explained as follows:—

1. Both Sets of Loaves Exhibiting Ropiness

If the loaves from both the check dough and the test dough develop rope, the indication is that some material other than the one under investigation is the cause of the infection. This of course is only true provided due precaution and care has been exercised in handling both doughs and that the new sample of the ingredient being investigated and used in the “check” dough has been previously proven not to develop a ropy loaf.

In such a case where the evidence secured indicates that some ingredient other than the one being investigated is the carrier of the rope infection, each ingredient used should be tested in the same manner by means of further baking tests.

2. None of the Loaves Exhibiting Ropiness

In case none of the loaves from either set of doughs develop rope,

it is quite apparent that the development of rope in the bakery can not be attributed to the particular ingredient in question or any of the other ingredients used. In this event, it would appear that some other source of infection existed in the shop which probably has been removed by the necessary cleaning and disinfecting measures taken.

3. The Case of the Development of Rope Only in the Test Dough

If the “check” loaves are free from rope but it is observed that ropi-ness develops in any of the “test” loaves, the indication is that the particular ingredient being tested and used in the “test” dough was at fault. This ingredient should be promptly removed from the storage room and not used until further investigated. However, no definite conclusion should be drawn until the baking test has been repeated with similar results, and then confirmed by bacteriological tests conducted under the supervision of a man who has been trained in this scientific line of work.


If the baking tests described above indicate that any one particular raw material is the cause of rope, this one ingredient should be removed from contact with the other materials and not used. However, before being sure of this indication, actual bacteriological tests are necessary.


The word “mold” refers to a certain group or class of tiny plants which are visible to the naked eye and which are made up largely of a cottony, thread-like structure which presents a “furry” appearance. Molds are unquestionably familiar to practically everyone, inasmuch as nearly all household foods, if kept for a period of time under warm or moist conditions will exhibit mold growth. There are various types of molds,—differing somewhat in general appearance, color and rapidity of growth.

The color of these molds is usually brown, red, orange, yellow, green, blue, pink, white or black. While the majority of the common molds are not poisonous, a few of them are said to be detrimental to health.


As the mold plant grows and develops on food or other organic matter, little thread-like stalks or “whiskers” become noticeable. A tiny ball usually develops on the top of these stalks and is often spoken of as the spore sack. This sack contains hundreds of tiny mold seedlings or spores each of which is so small that it can only be seen through the microscope. On the slightest disturbance such as a mild breeze, these spore sacks break,—releasing numberless mold spores which float away in the air as tiny specks. Naturally, under ordinary conditions some of these spores find a lodging place on bread or other foods exposed to the atmosphere. Furthermore, mold spores can be carried from one place to another by flies or other insects.

Under proper conditions of food, warmth and humidity these spores will thrive and produce a luxuriant growth of mold plants and thus the process of reproduction and distribution of mold continues. Mold spores usually settle on the outside of the bread or other foods and therefore, mold growth first appears on the exterior surface. Then the thread-like projections of the mold plant extend themselves into cracks or tiny openings on the surface and thus the mold spreads from the exterior to the interior of the loaf. The subject of mold in relation to bakery products should be of interest to every baker and should be given serious consideration inasmuch as a loaf of bread which becomes moldy prior to delivery or very shortly thereafter, frequently proves disastrous to the sale of that particular loaf.

In this connection, it should be remembered that there are certain conditions which pre-dispose and encourage the development of mold in bread and other bakery products. On the other hand, certain sanitary precautions may be taken which will aid materially in delaying or preventing the development of mold and if these precautions are conscientiously adhered to, it will be rare that the baker will be confronted with the mold problem.



While some mold spores are floating about in practically all ordinary atmosphere, the presence of stale bread,—crumbs, old waste dough 01 other similar material in or near the bakery as well as unclean machinery, wrapping paper, bread boxes, wagons or cases offer ideal conditions for the rapid development of mold plants from which numberless mold spores are produced.

These mold spores then contaminate the atmosphere in the neighborhood of the moldy material and this mold laden air circulates throughout the immediate vicinity. In this way such products as bread coming in contact with this air are naturally infected with a greater number of mold spores than ordinarily and under these conditions there is a much greater likelihood of the subsequent appearance of mold in products thus exposed and infected.

Therefore, one of the first preventive measures against mold is the maintenance of absolute cleanliness throughout the bakery, including machinery, equipment, wrappers, bread boxes, delivery wagons, etc., as well as all bakery premises. This of course, means frequent scrubbing of the bakery and thorough cleaning of all machinery and equipment coming in contact with the bread or other baked goods. Furthermore, no stale bread or rubbish should be allowed to accumulate in the bakery or in the immediate neighborhood.

Molds thrive best in dark places. Hence it is important that the bakery be amply supplied with sunlight and well ventilated.


As a preventive against the development of mold in bread; it is essential that the loaf be completely baked, having a crust which is not unduly moist.

The loaf should be thoroughly cooled and the crust surface dry before wrapping. If bread is wrapped while still warm, it will be in an ideal condition for the rapid development and growth of any mold spores. Furthermore, the wrapping paper used should be stored in a dry, clean, cool place and kept absolutely protected from dust. Bread boxes or cases should be kept scrupulously clean and properly ventilated for if they are not, some of the moisture escaping from the loaf may condense on the surface causing a moist or humid condition which encourages the growth and development of molds.


The installation of air filters and air washing equipment whereby the air entering the bakery is first cleaned, aids considerably in eliminating the dust particles which carry mold spores in the air. Such a system serves as a preventive measure against the development of mold in bread by cutting down materially the number of mold spores floating about in the air of the bakery and in this way the chances of the subsequent occurrence of moldy bread is greatly reduced.

The infection of bread and other bakery products with mold spores takes place after the product is baked; namely, during the cooling, wrapping, handling, delivery or storage. While it is impossible for the baker to control the conditions under which the bread is handled after delivery to the customer, it is quite certain that if the proper protective measures against mold are taken in the bakery, there will be very little likelihood of complaint on the part of the housewife concerning moldy bread.


Many tests have been conducted which demonstrate that the development of mold in bread cannot be traced to any of the ingredients used. This is due to the fact that the temperature reached by the dough in the baking process is sufficiently high to kill any mold spores which might be present in the dough, and the loaf directly after baking is thereby rendered sterile insofar as mold is concerned.

Design and Layout: © Anthony Kohn, 2004-7
Content: © Janet Bostwick, Barry Harmon, Anthony Kohn, Dick Margulis, 2004-7
All rights reserved.
"A Treatise on Baking is © ACH Foods Inc, and is reproduce on the alt.bread.recipes FAQ website with permission.
This page can be found at http://abrfaq.info/treatise/202
It was accessed at 01:37, 07 Jul 15 (GMT +1000)