5 replies to this topic

[moskito]

Dear all,

 

we are a large bakery producing biscuits and cakes mainly based on wheat flour. Does anybody know literature data or can provide data for inactivation of B. cereus (vegative and spores) during baking?

Wheat flour/wheat bran/wheat germ or whole meal can be contaminated by this type of microorganism. The range can be from 10 - 10000 cfu/g.

 

We have to cover 2 cases:

- biscuits of less than 0,5 cm height in worst case, i.e. water is removed rather rapidly. On the other hand surface temperature is higher than 100°C. Inside it is 100°C as long as sufficient water is present (assumption because we are not able to measure core temperature. Baking time 7-12 min depening on type of biscuit.

- cakes auf 300 - 500 g. Core temperature will reach around 95°C during process, which takes 30 - 45 min. Water will not be removed. Depending on type 12 - 18% water will be present.

 

Does anybody can support me with data.

 

Rgds

moskito

[SUSHIL]

Hello Mr Moskito,

Food borne diseases caused by B. cereus are associated with 4 log to 8 log cells/spores per g of the food vehicle. Low numbers of its spores, too low to cause food borne poisoning, can be found in a wide range of foodstuffs. Spores can germinate and multiply in humid, low acid foods, from 4-5°C to 55°C.

The number of spores in processed foods must be kept as low as possible by proper cleaning and disinfection of equipments. Rapid cooling is necessary to prevent germination and growth of B. cereus spores. Low pH (below 4.5), reduction in aw (below 0.91) would inhibit B. cereus. In other cases, refrigeration below 4°C is necessary to prevent growth of all types of B. cereus, including psychrotrophic strains.

 

Vegetative bacteria (including pathogens), moulds, yeasts and viruses are readily destroyed during the baking process, however post-baking contamination from air, equipment, food handlers and fillings can occur. A freshly baked product is considered to be sterile, but spores of certain bacteria such as Bacillus Cereus which originates from the flour can survive the baking process. The toxins produced by B.cereus and S. aureus are heat stable and will survive cooking or baking and result in food poisoning symptoms.
     Ingredients other than flour pose a greater safety risk in bakery products these include egg, dairy products, synthetic creams, custards and icing and can be the source of serious food safety hazards. Other ingredients added post baking, such as spices, nuts and fruit fillings or toppings may also be potential sources of contamination.
     Post-baking contamination can be controlled with proper Food Safety Management System in place. Newer technologies such as modified atmosphere packaging can be employed to improve shelf life.
     As means of confirming that the baking facility has established controls that are effective in maintaining production that is free of spoilage and pathogenic micro-organisms, a program of environmental monitoring should be introduced. The implementation of a microbiological testing program will serve as a measure to assess the effectiveness of the cleaning program as well as the adherence to Good Manufacturing Practices.

The microbiological testing program should be used to effectively monitor your food safety management system. Trend analysis must be conducted to effectively monitor hygiene standards as well as ensuring continual improvement.

 

The microbiological testing program-

• Surface and hand swabs
• Water sampling
• Product analysis of raw and finish goods. This includes testing ingredients used in product
   formulation as well as packaging material.
• Air monitoring

   Most importantly the results obtained from microbiological analysis must be used as part of the corrective action program and where contamination is identified an effective root cause analysis must be conducted.
     Microbiological analysis must be seen as a tool for the effective monitoring of the food safety management system in which the results are used as part of the corrective action and continual improvement program.

 

Attached below files-

Attached Files

•  Survey of the Microbiological Examination of Fresh Cream Cakes.doc   134.5KB   144 downloads
•  Bacillus cereus in foodstuffs.pdf   197.37KB   311 downloads

[Charles.C]

Dear moskito,

 

I suggest you have a look at this parallel thread - 

 

http://www.ifsqn.com...wth/#entry67520

 

And also at the sub-links in Post #4.

 

Logically you appear to need some more temperature data.

 

Rgds / Charles.C

 

@Sushil - Thank you for your frequent re-use of files posted elsewhere in this forum. It would be appreciated if you could additionally  include forum links to the  source of these attachments since the original context may be equally valuable.

 

PS - 10^4 cfu/g of B.cereus is rather high. I'm not a wheat scientist but may be approaching the potential toxin generation level. For example this typical summary (info. is much amplified in other files / links preceding) - 

 

Bacillus (B.) cereus is a sporogenous bacterium which is present all over the world. As a result of contamination with sporophorous soil particles or dust, B. cereus can be easily transmitted to foods. Through heat treatment the germ is killed but its spores survive.

The complete avoidance of contamination of foods is difficult because of the worldwide occurrence of the bacterium. A low bacterial count is normally no problem for consumers. However, certain deficient storage conditions can result in the germination of the spores and / or multiplication of germs on foods. When consuming foods contaminated by B. cereus, toxins and / or germs are taken up which can result in food poisoning and / or gastro-intestinal infections in humans. A germination of the spores can be prevented by rapid cold storage of the heated foods. For that reason the emphasis must be placed on the maintenance of the cold chain.

Characteristics

The initial contamination dosage on foods with B. cereus is in most cases very low (<10²-10³ CFU/g). As a rule multiplication in foods to a total bacterial count of 10⁵ to 10⁸ colony-forming units of the germ per gram (CFU/g) is required to generate relevant amounts of toxins in foods or in the small intestine.

The vegetative form of B. cereus grows in a range of 10 to 50°C, with a temperature optimum between 30 and 40°C. However, the individual cold-tolerating strains can also multiply at temperatures of 4 to 6°C; in these cases the generation times are, however, considerably longer. Below a pH value of 4.8B. cereus strains cannot multiply. However, the acid tolerance between the strains varies considerably. The minimum water activity value (aw value), which allows for a multiplication, is at approximately 0.92. The heat resistance of the spores is strongly dependent on the food matrix. In general, the heat resistance of the spores corresponds to that of other mesophilic spore-forming bacteria growing optimally at mean temperatures but strain variability is very high. Usual heat treatments kill vegetative cells. Temperatures below 100°C allow the survival of individual spores; a sufficient and rapid cooling after heat treatment is, therefore, necessary in order to prevent the germination of spores. The destruction of the competitive flora by heat treatment supports the germination of the spores and the transition to the vegetative phase. The surviving spores are usually causing a B. cereus disease.

Two types of disease can be differentiated:

(i) an emetic intoxication. In this case a heat, pH and proteolysis-stable toxin (cereulide) preformed in the food during the multiplication of the vegetative cells is taken up.

(ii) the diarrhoea type. In this case vegetative cells or spores of B. cereus are taken up via the food. The spores form a heat-labile enterotoxin in the small intestine – preformed toxins are taken up more rarely; this requires, however, a very high initial B. cereus bacterial count in the food.

The incubation time and intoxication by preformed toxin occurs almost exclusively after the consumption of starch-containing foods such as rice and noodles. Meat and meat products play a subordinate role for the emetic type. However, contaminated meat and contaminated meat products are among the possible causes of the diarrhoea type. In the event of an insufficient cooling of meat and meat products and a previous contamination of the products with B. cereus there can be a critical multiplication of the germ on food. A similarly problematic cause are long warming phases of contaminated foods in a temperature range between 15 and 65°C. This might result under certain circumstances in diarrhoea.

http://www.bfr.bund....reus-54345.html

[SUSHIL]

Hello Charles,

I don't re-use files from the forum which are posted elsewhere in this forum.They may have been posted previously on this forum by somebody. I obtain these files from internet.If they have been posted in this forum your forum should devise a system that these files do not get posted/ duplicated on this forum.

It is hard to find where these files have been posted,otherwise members who are posting their questions could have easily searched the forum and got their replies without posting their question on this forum.

[moskito]

Dear both,

thank you for the response.

Charles, you are right, I am looking for more temperture data. First, I need this for the risk assessment. Second, one of our customers wants to fix a specification with B. cereus < 100 cfu/g. My data of final product analysis show no out-of-spec results. But the general load with B. cereus is low. But I have no data, if contamination would be high. Therefor I am looking for some inactivation data.

 

Rgds

moskito

[Charles.C]

Dear moskito,

 

Regarding my previous post -  by “more temperature data”, I actually meant data regarding yr own process to compare with that in the various refs supplied.

 

I guess the crucial information, as usual, is the T vs t profile in yr biscuits, combined with knowledge of such items as pH, Aw etc.

 

I’m unclear as to whether the data already supplied was sufficient to answer yr OP or otherwise ? .

 

Heat resistance B.cereus Spores

 

Psychotrophic, mesophilic, and thermophilic members of the Bacillus genus produce spores that have low, medium, and high heat resistances respectively (eg D-values of a few minutes at about 80degC for some of the psychotrophs, at about 100-120degC for many of the mesophiles, and at well above 120degc for some of the thrermophiles.

(Micro.safety of foods, Lund)

 

I guess that most B.cereus spores are  mesophilic although some psychrophilic strains apparently exist also.

 

Some Specific data  B.cereus -

 

Rice

D(100degC) = 1.2 -7.5 mins (depends on strain, food,etc)

(Any) Emetic toxins will be inactivated 90 min at 100°C at pH 8.6

(Any) Diarrhoeal toxin will be inactivated 5 min at 56°C

(source, B.cereus data sheet, NZFA)

 

Bread

D(95degC) – 2.9min

D(95degC) – 36.2min

(source, ICMSF vol.5.)(ex Kaur 1986)

 

Various

See my previous attachment, table 5, pp1

 

Unfortunately have not seen any specific data on “Biscuits”. Two or 3 other posters are I believe active in this product area so might like to advise if they happen see this thread.

 

Consider this comment from my previous attachment pp1 -

 

Sterilization is the most effective way to control Bacillus cereus spores.  Considering heat resistance data (Fernandez et al 1999), 3 min at the constant temperature of 105 ºC can produce 5 log reductions in the population of a high resistant Bacillus cereus strain. Temperatures higher than 105 ºC should protect food from this microorganism in most instances. However, only canning can ensure complete destruction of B. cereus spores. Other heating processes such as normal cooking, mild heat application on refrigerated processed food of extended durability (REPFED’s ) or pasteurization are not enough to kill  all  Bacillus  cereus  spores.  These  treatments  will  activate  spores,  thus  readily triggering germination and enhancing further vegetative cell multiplication. Therefore, a rapid cooling process is required, followed by storage at temperatures of refrigeration, to avoid the multiplication of vegetative cells to a level that could endanger the safety of the product.

Establishing standard cooling procedures for heat treated foods is advisable (Collado et al.  2003).  As  the  growth  rate  of  B.  cereus  is  similar  and  not  higher  that  that  of Clostridium  perfringens  in  the  range  of  temperatures  critical  during  cooling  (see  § 4.1.1), the procedures developed for C. perfringens would likely also prevent B. cereus foodborne poisoning.

 

The previous linked thread (and pp1) notes that the consequence of germination will vary, ie within  certain pH / Aw limits (eg <4.5, < 0.92 respectively) no further vegetative growth will occur. Such data is so far lacking in yr OP.

 

I can make a few predictions regarding the  process described in OP –

 

(1) if yr input material has B.cereus > 100cfu/g, then the basic quality may be questionable although not necessarily unsafe.

(2) The achieved baking reduction of  B.cereus (vegetative / spore) levels for the  product requires knowledge of core temperature / time.

Based on previous threads / attachments, the vegetative component should not be an issue assuming 100degC is reached in the core / yr quoted process time (assuming a target 6D reduction)..

 If one assumes a spore reduction target of 6D  (depending on worst case initial/target final levels) and a D(100degC) range of, say, 1-5mins, a core temp. of 100degC appears to be approx. associated with a minimum time of 6-30min. So yr stated conditions may be inadequate to “eliminate” B.cereus spores in some cases.

(3) Any remaining B.cereus spores post-baking may/may not germinate and those which do may/may not vegetatively multiply depending on factors such as lag time, cooling profile, pH, Aw. I have not seen any published lag time data for present setup however pp1 and  (computed) B.cereus data quoted in an earlier thread for seafood matrices suggests that delay times may be significant. Also in view of above quoted extract see the  section on C.perfringens in pp3.

 

 

Rgds / Charles.C