What is fermentation Chemistry, how are tempeh, yoghurt, sourdough and soy sauce made using microorganisms, and what does precision fermentation in Singapore mean? Fermentation uses selected microorganisms or their enzymes to transform substances in a food or production medium. Yeast can convert sugars into carbon dioxide and ethanol under suitable conditions; lactic acid bacteria can convert sugars into lactic acid and other products, influencing pH, flavour and texture; and fungi such as Rhizopus play central roles in ordinary soybean tempeh production. Singapore’s Food Agency (SFA) distinguishes familiar traditional fermented foods from certain new foods produced by biomass fermentation—where microbial biomass itself may become an ingredient—and precision fermentation—where microbes act as production systems for particular purified ingredients such as proteins or flavour molecules. A food’s fermented status is not automatic proof that it contains living probiotic organisms, is risk-free, or can safely be manufactured at home.
For Hougang Secondary Science, SEC Chemistry and JC students searching for fermentation equations, yeast carbon dioxide, lactic acid pH, why yoghurt thickens, how tempeh works, microbial protein and Singapore SFA novel-food rules, begin with three clear questions: Which microorganism or enzyme performs the transformation? Which molecules enter and leave the process? What evidence shows the food is safe and produced under appropriate controls? The school-level ethanol equation C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ illustrates how glucose can be converted to ethanol and carbon dioxide in a simplified yeast fermentation model, but real food fermentations involve wider biochemical pathways and mixtures. SFA explains that genuinely novel fermentation-derived foods require safety assessment and approval before sale in Singapore. This guide gives a worked chemical-mass calculation, compares traditional and precision processes and links food science to learning continuity without presenting dangerous DIY fermentation recipes.
A little spoonful of yoghurt contains a big Chemistry story
A student opens a cup of yoghurt. It is thicker and tastes different from ordinary milk. What changed? The story can involve microorganisms using milk sugars, producing lactic acid, changing pH and altering interactions among milk proteins. A person does not need to see individual bacterial cells to know that a biochemical process may be involved. The evidence appears in flavour, acidity and texture.
Now imagine a second process where carefully selected microbes make a particular protein or flavour molecule for a food manufacturer. Instead of selling the complete fermented food, the manufacturer may purify the target ingredient. Both systems involve microbes, but their finished products and safety assessments can be very different. That is why “fermented” is a starting clue, not a complete explanation.
What the Singapore Food Agency says fermentation means
The Singapore Food Agency: New Foods from Fermentation explains that traditional fermented foods include bread, yoghurt, soy sauce, tempeh, miso and kimchi, made by microorganisms such as bacteria, yeast and fungi. SFA uses this familiar history to explain the emergence of new fermentation-derived foods. It describes biomass fermentation and precision fermentation as two newer categories that may involve different ingredients and safety considerations.
| Category | What is transformed or produced? | Product question for the student |
|---|---|---|
| Traditional fermentation | A food substrate is transformed by suitable microbes and their enzymes | How did its acidity, texture or flavour change? |
| Biomass fermentation | A microbial culture is grown for biomass that may be used as food protein | Which organism makes up the ingredient, and how is safety established? |
| Precision fermentation | Microbes make a target ingredient, which is then recovered and purified | What specific molecule is produced and how is it separated? |
| Uncontrolled spoilage | Unwanted microbes or conditions produce changes that may be unsafe | What evidence differentiates a controlled process from contamination? |
The categories should not be collapsed into “all fermented foods are cultured yoghurt”. Precision fermentation is a manufacturing technique that can make an ingredient not normally associated with a traditional fermentation recipe. Its regulatory status depends on the product, organism, prior consumption history and applicable SFA assessment.
Yeast and the glucose-to-ethanol school equation
A familiar classroom representation of alcoholic fermentation is C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. In this simplified net equation, one mole of glucose yields two moles of ethanol and two moles of carbon dioxide. It conserves carbon, hydrogen and oxygen atoms: the reactants contain six carbon atoms, twelve hydrogen atoms and six oxygen atoms, and the written products contain the same totals.
Real yeast metabolism involves many enzyme steps, competing pathways, biomass growth and changing conditions, so the school equation is a useful stoichiometric model rather than a complete factory flowsheet. It also should not be treated as an instruction for producing alcohol at home. The Why Bread Rises: Yeast and Fermentation explores the different educational question of how gas from yeast helps bread dough expand.
Worked example 1: how much carbon dioxide is theoretical?
Question: A hypothetical complete reaction follows the simplified equation C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. If 9.00 g glucose is converted exactly according to the equation, what mass of CO₂ is produced? Use Mᵣ(glucose) = 180 and Mᵣ(CO₂) = 44.
Solution: From the balanced equation, 180 g glucose produces 2 × 44 = 88 g CO₂. Thus 9.00 g glucose corresponds to 9.00 × 88/180 = 4.40 g CO₂. This is the stoichiometric theoretical amount under the given complete-conversion model. It says nothing about actual commercial production rates, biological yields, food suitability or safe processing conditions.
Transfer: If real measurements gave less CO₂, the student should not automatically conclude that the equation violates mass conservation. Real processes may not convert every molecule exclusively through the assumed route; carbon can be found in other products and biomass. The experiment’s system boundary and measurements matter.
Lactic acid, pH and why yoghurt can thicken
In an appropriate yoghurt fermentation, bacteria metabolise suitable milk sugars to produce lactic acid and other substances, lowering pH. This can affect the electrical charges and interactions among milk proteins, including casein, contributing to the gel-like texture associated with yoghurt. It is not simply that a liquid has “evaporated into a solid”. Chemistry of acids and protein structure help explain the change.
A good student answer identifies the substrate, microbial action, acid change and protein response. The sibling Why Yoghurt Sets: Lactic Acid and Casein gives more detail about yoghurt setting and casein. The exact organisms and formulation depend on the product, so do not assume every food described as a yoghurt alternative follows the same process.
Tempeh and other fungal foods: not every fermentation is sour milk
Traditional soy-based tempeh is associated with the growth and activity of suitable Rhizopus fungi. The fungal network can help bind the beans into a coherent cake, while enzymes and biochemical changes affect the food. This is a different type of fermentation from lactic acid bacteria thickening milk, and it has different substrate and process requirements.
A crucial food-safety distinction: ordinary soy tempeh is not the same product as certain fermented corn or coconut products known as tempeh bongkrek. SFA warns that improperly controlled fermentation of some corn or coconut products can allow production of bongkrekic acid, a dangerous toxin that cannot reliably be removed by ordinary washing or cooking. The SFA: Bongkrekic Acid in Certain Fermented Corn and Coconut Products explains these risks and advises against unsafe home fermentation of such products. Students should not generalise this hazard to claim that every commercially prepared soy tempeh is the same thing.
Why different microbes create different products
| Microbial system | Useful transformation | What must be kept separate |
|---|---|---|
| Yeast in a suitable dough | Produces gas that can help dough rise | Gas generation versus the full mechanism of gluten structure |
| Lactic acid bacteria in suitable milk | Generate lactic acid and contribute to changed acidity and protein behaviour | pH change versus simple water loss |
| Rhizopus fungus in soy tempeh | Grows a mycelium and transforms the bean substrate | Fungal fermentation versus lactic acid fermentation |
| Precision-fermentation production strain | Generates a particular purified protein or flavour molecule | Purified ingredient versus whole living culture |
| Unwanted contaminant organisms | May cause spoilage or toxin formation | Fermentation label versus demonstrated food safety |
Students sometimes ask whether the living microbe is always supposed to be eaten. The answer depends on the finished food. Some traditionally fermented foods may contain living cultures when consumed; others have been heated or processed. Precision-fermentation products can be designed to separate the desired ingredient from production microorganisms. Always describe the actual product instead of using the word “probiotic” as a synonym for “fermented”.
What is precision fermentation, and why does it matter in Singapore?
In precision fermentation, an appropriately selected production organism is used to generate a desired molecule—for example, certain proteins or flavour components. The target ingredient is then recovered and purified as needed. SFA notes examples involving milk proteins, vanillin and heme-related ingredients. This can create possible new ways to supply familiar functional molecules, but safe commercial use depends on evaluation of the organism, processing, impurities, allergens and finished food.
For students, the key scientific question becomes what is the output molecule and how is its identity and quality confirmed? Producing a familiar chemical through a novel biological process does not make all other process risks disappear. The SFA: Novel Foods Regulatory Approach explains Singapore’s novel-food regulatory approach; new foods from fermentation without the appropriate established history require SFA approval before sale.
Biomass fermentation is a different industrial idea
In biomass fermentation, microorganisms themselves are cultivated as a significant part of the food ingredient, rather than simply being discarded after making a purified target molecule. The food may consist partly of fungal, yeast, algae or other permitted microbial biomass. Its composition, digestibility, allergens and contamination risks require appropriate assessment. This differs from precision fermentation even when both use tanks, controlled growth and engineered production systems.
Understanding that distinction helps with future Chemistry, Biology and food-technology study. It shows why a manufacturing method and a product category are not the same piece of information. The method describes how something is made; the product analysis determines what it is and whether it meets applicable requirements.
Why acidity alone does not prove a fermented food is safe
Acidity can inhibit some undesirable microorganisms under appropriate circumstances, but different microbes have different tolerances, and a reading taken once does not establish that all safety risks have been controlled. SFA’s SFA: Safety of Home Fermentation explains the need for appropriate cultures, hygiene, controls and careful storage when discussing home fermentation. It also warns about possible contamination and allergens.
Do not treat a general pH number from another food or recipe as a universal safe target. In particular, SFA provides product-specific kombucha guidance that should not be copied automatically into tempeh, milk products, pickled vegetables or novel foods. A student’s role here is to understand why process conditions matter, not to manufacture an untested food product for consumption.
Food safety is not the same as successful flavour
A fermented food can taste sour or have the expected texture while still raising other possible safety questions. Conversely, safe commercially manufactured fermentation-derived ingredients can come from processes that do not look or taste like traditional foods. Relevant evidence may include the identity of the organism, substrate quality, contaminants, hygienic controls, processing conditions and actual product testing.
SFA’s discussion of new foods highlights risks such as undesirable microbes, harmful substances and allergens. It requires appropriately novel fermentation-derived foods to undergo safety review before being permitted for sale. The scientific habit worth teaching is to keep sensory observation separate from validated safety evidence.
Worked question 2: interpretation of a pH change
Question: In a fictional laboratory dataset, a controlled culture produces a solution whose pH changes from 6.2 to 4.6. A student writes, “The culture has produced acid, so the finished food must be safe.” Which parts of that conclusion can be supported?
Answer: The pH readings show the tested solution has become more acidic under the measurement conditions. Acid production could be a reasonable hypothesis with suitable supporting evidence. However, pH measurements alone do not identify every chemical present or prove microbiological safety. Other tests and validated process controls would be needed. This answer separates a useful observation from an unsupported guarantee.
The three mistakes a Science tutor should diagnose
| Student statement | Underlying missing idea | Next question |
|---|---|---|
| Fermentation always makes alcohol | Different microbial pathways | Which organism and products are relevant? |
| Any sour food is safe | Measurement versus safety proof | What else must be tested? |
| Tempeh is made by exactly the same bacteria as yoghurt | Microbial identity | What role does fungal mycelium play? |
| Precision fermentation and yoghurt are identical | Manufacturing category | Is the whole food transformed, or a molecule produced then purified? |
| The school equation gives actual industrial yield | Stoichiometric model versus real process | Where can material go besides the idealised products? |
| Every fermented food contains live probiotics | Processing and product definition | Was it heated or purified after fermentation? |
A four-session Science and Chemistry learning programme
| Session | Learning aim | Independent evidence |
|---|---|---|
| 1 | Classify microbes and fermentation products | Distinguish yeast, lactic bacteria and fungal systems |
| 2 | Connect reactions and pH with measured changes | Explain an unseen acidity or CO₂ calculation |
| 3 | Compare traditional, biomass and precision fermentation | Describe what is consumed and what is purified |
| 4 | Evaluate safety claims from supplied evidence | Identify a conclusion that needs more testing |
In an eduKate-style three-pupil tutorial, one learner can analyse a balanced equation, one the pH dataset and one the SFA definition of novel food; then each answers a changed question independently. This helps reveal whether the learning gap is chemical, biological or about interpreting evidence. It does not require students to ferment food at home, handle cultures or taste an experimental sample.
Where the learning leads
- Lower Secondary Science: microorganisms, chemical changes, fair tests and the distinction between observation and inference.
- Secondary 3–4 Chemistry: organic compounds, reaction equations, acids and pH, and mass conservation.
- JC H1/H2 Chemistry: kinetics, equilibria, acid-base systems and analytical evidence.
- Beyond school: food science, biotechnology, bioprocess engineering, quality assurance and regulation.
Read Why Bread Rises: Yeast and Fermentation for the dough example, Why Yoghurt Sets: Lactic Acid and Casein for lactic acid and casein, and Chemistry in Singapore Food for broader Singapore food Chemistry. The Singapore Chemistry and Bioprocess Study Pathways introduces relevant course families, while the Hougang Chemistry and Science Curriculum Library connects this new fermentation shelf to the Hougang Science and Chemistry reference library.
Frequently asked questions
Does fermentation always produce ethanol?
No. The products depend on the microorganism, substrate and pathway. Lactic acid fermentation, yeast ethanol fermentation and fungal food fermentation are different processes.
Is ordinary soy tempeh the same as tempeh bongkrek?
No. SFA’s specific warning concerns dangerous toxins associated with certain improperly fermented corn and coconut products. Do not conflate that with all soy-based tempeh.
Do novel foods made by precision fermentation need SFA approval?
Where they fall under SFA’s novel-food framework, the required safety assessment and approval apply before sale. The exact status depends on the ingredient and production process.
Does pH below 5 prove a fermented food is safe?
No. There is no universal single pH threshold establishing safety for every fermented food. Product-specific safety controls, suitable microorganisms and contamination evidence matter.
Is precision fermentation directly examinable for every SEC Chemistry candidate?
Not as a universal module. It is an applied crosswalk from school chemical reactions, organic molecules and scientific evidence to contemporary food biotechnology.
Official SFA information and connected study guides
- Singapore Food Agency: New Foods from Fermentation
- SFA: Safety of Home Fermentation
- SFA: Bongkrekic Acid in Certain Fermented Corn and Coconut Products
- SFA: Novel Foods Regulatory Approach
- SFA: How to Read Food and Nutrition Labels
- Why Bread Rises: Yeast and Fermentation
- Why Yoghurt Sets: Lactic Acid and Casein
- Singapore Chemistry and Bioprocess Study Pathways
- Hougang Chemistry and Science Curriculum Library
SFA food-science and safety resources were reviewed in October 2026. Worked examples are original learning exercises; this article does not supply or endorse a home fermentation procedure.