End of September 2026: in Year 2 of the vocational course in food service and hospitality (the Italian indirizzo Servizi per l’enogastronomia e l’ospitalità alberghiera), the subject — normally “Food Science and Culture” (Scienza e cultura dell’alimentazione), but the name changes from school to school, so check your planner — is closing its first block on nutrients (covered in Year 1; I wrote about it in nutrients in Year 1 of hotel school) and opening the one on food safety: contamination and HACCP. The first test on this topic typically falls between late October and November — about four to eight weeks from now — and in vocational schools short-notice oral tests are often added, not just the written one.
It is a very practical topic, tied to what you actually do in the kitchen lab, but for that very reason full of technical words that look alike (foodborne infection and food intoxication, contamination and infestation) and of an acronym, HACCP, that has to be learned as a precise procedure and not as a slogan to recite from memory.
How a food becomes contaminated
A food is said to be contaminated when it contains something that should not be there and that can harm whoever eats it. Contamination falls into three categories, and it is the first question you will be asked to see whether you have understood the basic logic:
- Physical contamination: a foreign body that has ended up in the food by mistake — a fragment of glass, a piece of plastic from packaging, a hair, a splinter from a damaged wooden chopping board. It is prevented with visual checks and equipment in good condition.
- Chemical contamination: chemical substances that should not be in the food — residues of detergents or sanitisers not rinsed off properly, pesticide residues above the limits, migration of substances from packaging unsuitable for food contact. It is prevented by following the technical data sheets of cleaning products and the rinsing times.
- Biological contamination: the most relevant in the kitchen, caused by micro-organisms (bacteria, viruses, moulds) or by their toxins. It is the one that most of the syllabus focuses on, because it is the one HACCP was created to manage.
Micro-organisms and growth factors
The bacteria responsible for biological contamination do not grow equally well everywhere: they need precise conditions, and knowing them is what lets you prevent contamination instead of merely discovering it afterwards.
The factor most cited in tests is temperature. The approximate ranges (the exact values can vary slightly from source to source, so treat them as orders of magnitude, not as absolute numbers to the last digit):
| Temperature range | Effect on bacteria |
|---|---|
| Below 0 °C (freezing) | growth stopped; bacteria do not multiply but often stay alive |
| 0-5 °C (refrigerator) | growth strongly slowed |
| 5-60/65 °C | danger zone: ideal temperature for bacterial multiplication |
| Above 65-70 °C | most pathogenic bacteria are destroyed by cooking |
The “danger zone” is the key concept: a food left for too long in that range — for example cooled slowly at room temperature instead of in a blast chiller, or kept out of the fridge during preparation — gives bacteria time to multiply to a dangerous amount. Other factors that influence bacterial growth, to be mentioned more briefly: moisture (bacteria prefer damp environments), availability of nutrients, pH (many pathogens prefer a neutral environment) and exposure time.
Foodborne infection or food intoxication: not synonyms
It is the distinction most often asked, to check whether you have understood the mechanism, not just the name of the micro-organism:
- Foodborne infection: the food contains the living micro-organism, which keeps multiplying and producing toxins even after ingestion, inside the intestine. Symptoms appear with some delay, because it takes time for the bacterium to multiply in the body. Example: Salmonella, often associated with raw or undercooked eggs and with poultry.
- Food intoxication: the food already contains the toxin previously produced by the micro-organism, even if the micro-organism itself is no longer alive or present in significant quantities. Symptoms can appear much more quickly, because the toxin acts at once. Example: Staphylococcus aureus, which produces a heat-resistant toxin — cooking can kill the bacterium but does not always destroy the toxin already formed.
Two other names that often recur in this year’s syllabus, only as established references: Clostridium botulinum (produces botulinum toxin, dangerous above all in badly sterilised preserves or home-made foods in oil) and Listeria monocytogenes (it develops even at refrigerator temperatures, which is why it is a particular risk for products such as soft cheeses and cured meats kept for a long time).
Cross-contamination
Cross-contamination is the transfer of micro-organisms from a contaminated food (typically raw) to one that was not, via an intermediate carrier: a chopping board not washed between a cut of raw chicken and one of raw vegetables, the operator’s hands, a knife, a work surface. It is one of the most closely checked points in the kitchen lab, and also one of the simplest to prevent: dedicated chopping boards and utensils (often colour-coded), washing hands between one task and the next, physical separation between raw and cooked.
The seven principles of HACCP
HACCP stands for Hazard Analysis and Critical Control Points, in Italian “analisi dei pericoli e punti critici di controllo”: it is the self-checking system that every food business must apply, according to the Codex Alimentarius and incorporated into European legislation (EC Regulation 852/2004). It is not a check done by someone else at the end: it is a procedure that the business applies to itself, continuously. The seven principles, in the order in which they are applied:
- Hazard analysis: identify, for each stage of the process (from buying raw materials to serving), which hazards — physical, chemical, biological — may arise.
- Identification of critical control points (CCPs): among all the stages, which are the points where a hazard can actually be prevented, eliminated or reduced to an acceptable level. Not every stage is a CCP: only those where the control is truly decisive.
- Setting critical limits: for each CCP, a measurable value that separates safe from unsafe — a minimum cooking temperature, a maximum time of exposure to room temperature.
- Monitoring system: how and when you check that the critical limit is respected — for example measuring the core temperature of the product with a probe thermometer.
- Corrective actions: what to do if monitoring finds that a critical limit has not been met — for example discarding the product or cooking it for longer.
- Verification procedures: periodic checks that the system as a whole really works (internal audits, calibration of instruments).
- Documentation and record-keeping: keep a written record of everything that was checked, when and with what result — it is what makes the system demonstrable in the event of an inspection.
Worked exercises: finding the CCPs
For each of the three cases the reasoning is the same: list the stages of the process, identify where the main hazard lies, and decide at which of those stages the control is truly decisive (that is, it is a CCP).
Case 1 — home-made mayonnaise (with raw eggs). Stages: buying eggs, preparation (raw eggs whisked with oil), storage, serving. The main hazard is biological: Salmonella may be present in raw eggs. The main CCPs are the quality and storage of the eggs before use (refrigerator temperature, expiry date) and the storage temperature of the mayonnaise after preparation, because once whisked it remains a raw, not a cooked, product, so it must be kept in the refrigerator and eaten within a short time — no later stage “corrects” the initial risk.
Case 2 — roast chicken. Stages: buying, raw storage, cooking, possible cooling, serving. Here there are two CCPs, different from each other: the cooking, which must reach a core temperature sufficient to destroy pathogens (roughly above 70-75 °C, a value to check with a probe thermometer, not by eye), and — if the chicken is not served at once — rapid cooling after cooking, so as not to let the already cooked product slowly pass through the danger zone (5-60/65 °C). One stage to cite as a hazard but not as a CCP in its own right: cross-contamination between raw chicken and other foods during preparation, prevented with separate chopping boards and utensils.
Case 3 — tiramisu. Stages: preparing the cream (raw or pasteurised eggs, mascarpone), assembly, storage, serving. As with mayonnaise, the main hazard is biological and concerns the raw eggs. The decisive CCP is the cold chain: if the at-risk ingredient is raw egg, the only way to limit bacterial multiplication is to keep the product in the refrigerator at all times, from preparation to serving, minimising the time spent at room temperature. An observation often asked about in oral tests: using pasteurised eggs instead of fresh raw eggs moves the CCP further upstream (to the choice of raw material) and reduces the risk at its root.
Typical mistakes
- Confusing foodborne infection and food intoxication: the difference is whether the food contains the living micro-organism or only its already formed toxin, not the type of symptom.
- Treating every stage of the process as a CCP: only the stages where the control is truly decisive are; listing them all as CCPs is as common a mistake as forgetting them.
- Forgetting cross-contamination as a category of its own, distinct from direct biological contamination of a single food.
- Treating temperature values as absolute numbers to the last digit: they are indicative thresholds, useful for reasoning, not physical constants to be quoted to the exact degree.
- Confusing contamination (the presence of something harmful) with infestation (the presence of pests such as insects or rodents): they are related concepts but not the same phenomenon.
For this subject there is no dedicated practice test yet: you will find the school practice tests for maths and physics. For the full picture of the previous year on this course, start from nutrients in Year 1 of hotel school; if you also need to review energy metabolism, I wrote about it in basal metabolism and energy requirements; and if you want to see how the same conceptual framework of prevention applies on another vocational course, the comparison is in primary, secondary and tertiary prevention in hygiene. If you would like a hand preparing for the test, start with a free introductory call. The rest of the science syllabus is on the sciences page.
