Rejuvelac is essentially a natural (yeast and lactic) fermentation of sprouted grains.  One person quoted something to the effect of at its peak it is a pleasant tonic, but fermented too long or fermented wrong, it is simply putrid.  If the grains were rye, it could be called Kvass (Russian or Slavic origin). There are three general steps:

Soaking Sprouting Fermenting

The soaking and sprouting steps are essentially the same as “sprouting” in the food code or in FDA guidance.  Sprouting grains should be carried out in acidified water OR at refrigeration temperatures.  Ambient temperatures are not needed for seeds or grains to sprout.

Use canning citric acid powder to acidify tap water to pH ≤ 4.2.  Sprout grains in the acidified water at ambient temperatures.  Alternatively: sprout grains in plain tap water under refrigeration ≤ 41F.  Both of these methods will prevent ALL foodborne illness bacteria from growing.  Yes, Listeria monocytogenes can grow at ≤ 41F, but it grows VERY slowly.  Please see this LINK for an inexpensive and recommended pH meter.

After sprouting, the sprouts and husks are rinsed in potable water.  The acidified water is not needed for the rinse.  Fermentation is the next step.  Water is added to the sprouted seeds.  An ACTIVE culture should be added.  A wild fermentation is not recommended.  One concern with this process is the possible presence of bacterial pathogens.  Salmonella has been implicated in foodborne illnesses in sprouts and Bacillus cereus in grains and rice.  Note that Kvass and sourdough bread processes have a heating step and baking step respectively.  Rejuvelac does not.  In fact it is advertised as ‘raw”.  The control, therefore, is to have a culture that is active and ferments rapidly.  An active culture provides competitive inhibition, reduces available nutrients and lactic acid bacteria fermentation reduces the pH.  The concern then is that if one relies on the natural wild biota to grow from a few cells to many, during this time, pathogens can also grow from a few cells to many.

Add an ACTIVE fermentation culture.  Choose one of three methods.  1. Use a commercial dried or freeze dried culture.  2. Use a culture from a very recent successful previous batch.  3- Create a mother culture from wild microorganisms.  No 3. is essentially making a mini batch solely to grow an active culture.  An active culture is a necessity to minimize foodborne illness bacterial growth until fermentation reducing the pH of the Rejuvelac first to pH ≤ 4.6, then preferably to pH ≤ 4.2.  generally, Rejuvelac is fermented in 1-2 days at ambient temperature.  If it takes longer than this, it is a sign that the culture was not ACTIVE and the batch should be discarded.

A natural sprout biota (wild) culture will likely be a mixture of yeasts and lactic acid bacteria (think sourdough bread). The natural culture is allowed to ferment the sprouted grain water producing a yeasty (bready) smell along with a lactic acid sourness.  A purchased culture is more likely to be a lactic acid bacteria that will produce a yogurt like smell that has less of a bready smell.

Quality Control - Refrigeration
Rejuvelac that has been fermented to pH ≤ 4.2 is no longer TCS (temperature control for safety).  It does NOT have to be refrigerated for food safety.  Refrigeration is therefore solely for quality.  This means that if you were to transport or sell Rejuvelac at ambient temperature (e.g. at a farmer’s market), it could remain outside of refrigeration safely.
Soaking All pathogens Refrigeration ≤ 41F
Sprouting All pathogens Refrigeration ≤ 41F or acidify to pH ≤ 4.2
Fermenting All pathogens Ferment with an active culture dropping the pH to ≤ 4.2 as rapidly as possible
Aging At pH ≤ 4.2 no pathogens can grow* Refrigeration ≤ 41F for quality (not safety)
*it is possible that if E. coli O157 or Salmonella were present they could survive.

The following is a file containing two USDA FSIS authored guidance documents on cured, fermented, and dried meats including the USDA FSIS model HACCP plan.  It is recommended that retail operators wanting to produce dry and semi-dry sausage and dried whole muscle meats use this guidance to educate themselves before they consider writing a HACCP plan. Secondly, operators should become familiar with the formatting and required elements of a food code HACCP Plan as specified in the latest edition of the food code section 8-201.14.

This question comes up often.  ROP requires HACCP.  No ROP, no HACCP.

First, a common item exclusion for a different reason.  All acid foods pH ≤ 4.2 are non-TCS.  As a non-TCS food, no HACCP.  So, cold bagging dressings, acidic sauces, etc does not require HACCP because its non-TCS.

What about cold bagging TCS foods, like proteins?  The answer from FDA is no vacuum or removal of air, not ROP, no HACCP.  Read their interpretation carefully.

Download (PDF, 369KB)

Here is section “I” of the current version of FDA’s Acidified Process Filing form 2541e.  Here are some hints for completing the form when using a hot fill hold (HFH) process.

  • First, note the blacked out portions.  Nothing needs to be entered in these areas.
  • Column 1 is 01 for your first filing (of the form).
  • Column 2 is 01 for the first step (in this one step process)
  • Column 3 – check the box “Lowest Hold temp.” and below the word Fahrenheit write in the temperature provided by your process authority.  A standardized default value often used is 180F.
  • Column 4 – is the amount of time the HFH food must stay at the temperature indicated in Column 3.  This is usually minutes, so check the box “minutes”.  If the process authority said to invert food container and hold 1 minute; then right-side-up and hold 1 minute (the total time equals 2 minutes).  Write in 2.00 in the box below “minutes”.
  • Column 6 captures the scientific data that the process authority (PA) provides.  It is best not confuse this with processing time and temperature.  Just enter the data.  In almost all cases the “Other F” box is checked.  Write in the values provided by your PA for Ref T, Z, and below that: minutes (t).
  • Lastly, Column 11 is for Other factors.  If the processing time and temperature provided by your PA is valid only for a specific pH range, it will be indicated here.

Traditional tempeh is made from mold fermented soybeans. Whole soybeans are soaked, dehulled, cooked, cooled, and fermented. Specialty tempeh may include other sources of starches such as beans or whole grains.

From a food safety perspective,
tempeh is analogous to the hazards of sushi rice.

Sushi rice is soaked and cooked with the intention of warm holding for an extended period. Tempeh is soaked and cooked with the intention of fermenting at 30C for 24-48 hours. In both, the cooking process eliminates vegetative pathogens. This leaves the three sporeforming pathogens as hazards.

Spore forming pathogen Possible Control Measures
C. botulinum pH ≤ 4.6; presence of oxygen, competitive microbial cultures
C. perfringens pH ≤ 5.3; presence of oxygen, competitive microbial cultures
B. cereus pH ≤ 4.3; competitive microbial cultures

Tempeh soybeans, beans, or grains are soaked to hydrate them from their dried state. Hydrating these starches also hydrates the bacterial and mold spores present. Therefore, it is safest to hydrate at refrigeration temperature. Alternatively, the soaking water can be acidified to pH ≤ 4.3 by adding a mild acidulant such as vinegar, lactic acid, or acetic acid. High acid levels inhibit the three spore-forming pathogens. Later, during fermentation high acid levels will favor mold growth over growth of spoilage microorganisms. This acidulation step is not traditional, but is analogous to food safety changes made to traditional preparations of sushi rice.

Once hydrated and dehulled, the starches are cooked. As noted above, cooking eliminates all of the vegetative pathogens, leaving just the three spore-forming pathogens a concern.

After cooking, the dehulled soybeans are spread thin to cool. Spreading the starches thinly exposes all of the surfaces to air. Oxygen will prevent Clostridium growth and may lead to lethality. It is noted that at the microcosm level, there will likely be anaerobic areas. Bacillus cereus is facultative. Acidulated starches will prevent growth of these pathogens regardless of the presence or absence of oxygen.

Historically, the competitive microbial culture in tempeh was a Rhizpus (R. oryzae or R. oligosporus) usually originating from a banana or plant leaf the cooked soybeans were wrapped in. Today, a tempeh culture can easily be purchased. Starter spores are sprinkled onto the surface. The tempeh is allowed to ferment at about 30C for 24-48 hours. If using a quality starter culture, the mold will grow rapidly in ≤ 4h (functioning as a competitive antimicrobial culture). After 24-48h the tempeh will be held together by white mold mycelium indicating a successful ferment.

from wikimedia white mycelium with black sporangiospores

After 48h the tempeh culture may sporulate producing dark or black spores. This is not harmful, but is considered a quality defect. Likewise, fermenting past 48h may develop ammonia byproducts reducing quality and increasing the pH. An increase in pH is less of a concern to food safety at this point, since an active (competitive inhibitory) mold culture is present.

Tempeh is best stored frozen.  If kept refrigerated it will over-ripen in about 2-3 days (black spores and ammonia).   If left at ambient temperature it will over-ripen in 12-24h.  An additional food safety hurdle is that most tempeh is fried or deep fried.

For some additional details on Tempeh consult The Book of Tempeh (Wm Shurtleff).