Bacillus cereus does not grow in sake or during its manufacture

Sake has long been recognized as the safe product free frommicrobiological hazard. However, amid the consumers’ growing concern
over food safety, the discussion about the food safety on scientific basis isimportant for consumers’ reassurance. Recently, several studies havereported the presence of spores of Bacillus cereus in sake. Accordingly, toconfirm the microbiological safety of sake, we investigated the content andgrowth of B. cereus. First, we examined whether B. cereus spores grew
during sake production process through a spore addition test; consequently,
we observed no growth or germination of B. cereus spores during sakeproduction process. Next, we conducted a survey to assess the density of B.

cereus in various commercial sake products; consequently, we found thatthe density of these bacteria in sake is less than in other foods and notenough to be infectious, and the emetic toxin produced by B. cereus was
not detected in any sake samples. Therefore, we concluded that the safety
risk of B. cereus in sake is negligible.
[Explanation of terminology]
Bacillus cereus

Bacillus cereus is a spore-forming bacterium that is commonly found in soil, on vegetables, and in many
raw and processed foods (101–103/g). Food poisoning of B. cereus is mostly associated with a bacterial celldensity at minimum 105/g in food; thus small amounts of B. cereus result in a low risk of food poisoning.

B. cereus cannot grow in sake or during the sake manufacturing process;hence, there is a low risk of food poisoning by B. cereus in sake.

Bacillus cereus does not grow in sake or during its manufacture

SteamGrowth during the koji making process (Spore addition test)

765432107654
3210

Initial spore concentrations

Koji-Initial water activity

Fermentationmash

No growth ofB. cereus or toxin
production wasobserved during thekoji-making
process.

Frequency

Survey of the concentration of B.cereus spores and toxins
B. cereus is120
commonly found in100
food at a80
concentration of60
~103/g.
40
No toxin peak was observed.

200CFU/mL

At the start

4At the end

Control

2N.D.

＋
355＋1255＋2455＋2445

Saccharification(˚C) 55
No growth or toxin production was observed.
* Lactic acid was added at the start of coolingmakingKoji

6N.D.
Starter Spore addition－culture Cooling time(hr) 3

Steamed rice

2 h after Inoculation of koji
At the end of koji making process

Growth during starter culture making process (kouon-touka-moto)As a result of a survey ofcommercial sake, only a small
amount of B. cereus was foundcompared with other foods,
and no toxin was detected.

Density of B. cereus cells during fermentation(Spore and vegetative cell additions)
Spore
Vegetative cell
8Filtration
6
No growth of4
B. cereus or2
toxin production
0was observed.
-2Storage
Fermentation (day)Fermen-tation

Pressing

3Sake

Log 10 cfu/mL

Heat deactivation of all but
heat-tolerant spores

Lactic acidYeast

Log 10 cfu/g-shubo

Rice

We investigated the growth of B. cereus insake and confirmed its safety for consumers.

Log 10 cfu/g-mash

Several studies reported the presenceof B. cereus spores in sake

Spore reduction by filtration

2Filtration10

N.D.

N.D.

Spores were
removed byfiltration.

B. cereus does not grow or produce

Product toxin in sake or during the sakemanufacturing process.