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 -
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)
D(95degC) – 2.9min
D(95degC) – 36.2min
(source, ICMSF vol.5.)(ex Kaur 1986)
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