FOOD90023: pass the exams, not just read the notes
Your complete guide to University of Melbourne's food microbiology unit. See where the marks are, work real practice questions, and study with an AI tutor that knows FOOD90023.
Sia generates FOOD90023 practice questions, walks through bacteriophages and microbial metabolism step by step, and quizzes you on the material the exam weights most heavily.
Worked example
A food carries N0 = 100 cells of a bacterium with a generation (doubling) time g = 20 min, and it is held in the danger zone for 5 hours under conditions that keep it in log-phase growth. Using N = N0 × 2^n, what is the final cell count N?
Find the number of divisions n. The hold time is t = 5 hours = 300 min and each division takes g = 20 min, so n = t / g = 300 / 20 = 15 divisions.
Confirm with the exponential form N = N0 e^(ut), where the specific growth rate u = ln 2 / g = 0.6931 / 20 = 0.03466 per min. Then ut = 0.03466 × 300 = 10.40, e^10.40 = 32,768, and N = 100 × 32,768 = 3,276,800 cells, which matches.
So the final count is about 3.28 × 10^6 cells (log10 N = 6.5). The answer is option index 2.
The trap: Option B (32,768) is 2^15, the number of cells one single cell becomes, not the count from N0 = 100 starting cells. You must multiply by N0: N = N0 × 2^n, not just 2^n. The other common slip is using n = 5 (the hours) instead of n = t / g = 15 divisions, which gives the far-too-small 100 × 2^5 = 3,200. Always convert the hold time and the generation time to the same units before dividing. classic slip!
One exam decides 50% of your grade. Covers the whole subject; the largest single component. This whole page is built around that.
Overview
What FOOD90023 is, and where it sits
FOOD90023 Food Microbiology is a postgraduate (Level 9) subject in the University of Melbourne's Master of Food Science, run by the School of Agriculture, Food and Ecosystem Sciences at Parkville. It builds the microbiology a food scientist needs end to end: how microorganisms are named and classified, the structure of the bacterial cell, fungi (yeasts and moulds) and bacteriophages, microbial metabolism (respiration versus fermentation), the nature of microbial growth and the factors that control it, foodborne hazards and the microorganisms of food-safety concern, conventional and rapid identification methods, predictive microbiology, and the thermal and non-thermal inactivation of microbes. A practical laboratory program runs alongside the lectures and emphasises modern instrumental microbiological techniques.
The recommended background is chemistry and/or biology, and the subject assumes you are already in an honours or postgraduate coursework program. The required text is Ray and Bhunia, Fundamental Food Microbiology, 4th edition (CRC Press). Lectures are delivered as videos in the LMS followed by a live Zoom or webinar session, and the weekly laboratory practicals are outlined in the Laboratory Manual, which must be read before each session. The total time commitment is about 120 hours across the semester (48 contact hours).
The defining feature for study is that the assessment is almost entirely written: 70% of the grade is two closed-book short-answer exams (a 20% mid-semester exam and a 50% final), plus a 1000-word practical report at 20% and six fortnightly quizzes at 10% combined. There is very little number-crunching, the main exception being the microbial growth calculation. Marks come from explaining mechanisms clearly and backing each point with an example, so the subject rewards understanding and written articulation far more than memorised lists.
Difficulty & time commitment
Is FOOD90023 hard, and how much time does it take?
FOOD90023 is manageable if you keep a weekly rhythm and treat the back half as the main event. Across student reviews the pattern is consistent: it starts gently and steepens, and the heaviest assessment is the part that separates grades.
A read across student reviews and course feedback. See what students say ↓
The difficulty curve and the assessment weighting point the same way: the back half is harder and worth more. Front-loading effort there is the highest-return decision in the unit.
Is this unit for you
Who tends to do well, and who tends to struggle
You will likely do well if
- You can write a clear, structured short answer that defines a term, explains the mechanism and finishes with a concrete food example, because that is exactly how the two written exams are marked.
- You build the picture across the whole subject (cell, metabolism, growth, hazards, identification, control) rather than memorising disconnected lists, since exam scenarios cross several lectures at once.
- You read each week's practical in the Laboratory Manual before the session and keep careful notes, which feeds straight into the 20% practical report.
- You drill the recurring exam workhorses early: the bacteriophage food-industry question, comparing bacterial and fungal spores, the classes of disease-causing microorganisms, and the growth calculation N = N0 e^(ut).
You may struggle if
- You revise by memorising bullet lists; the short-answer exams reward explained mechanisms and examples, and list-only answers leave marks on the table.
- You treat the fortnightly quizzes as the main game; together they are only 10%, while the two written exams are 70% of the grade.
- You leave the heavier back-half topics (hazards, identification, predictive microbiology, inactivation) to cram, even though they carry the most exam weight.
- You skip the growth calculation as 'the maths bit'; it is the one quantitative item that reliably appears and is easy marks once you practise N = N0 × 2^n and N = N0 e^(ut).
- Practise writing full-sentence short answers under time, then self-mark against the standard 'definition plus mechanism plus food example', which is what the markers reward.
- Make a one-page sheet of the recurring exam themes (bacteriophages in food, spore comparison, exotoxin categories, MLF and its inhibitors, the growth equation) and rehearse each from memory.
- Master the growth calculation cold: n = t / g, N = N0 × 2^n, then confirm with N = N0 e^(ut) using u = ln 2 / g, and always report log10 N because the marker rewards the working.
- Connect each spoilage or pathogen organism to its control: which intrinsic and extrinsic factor (temperature, pH, water activity) limits it, and which inactivation step removes it, so you can answer applied scenario questions.
Syllabus
The 12 topics, week by week
The exam-weight marker on each topic shows where the marks concentrate. The amber topics carry the highest exam weight.
T1 · Introduction and safety in microbiology laboratories
Lecture 1; Lab ManualWhat food microbiology covers, why it matters for food safety and quality, and laboratory biosafety: aseptic technique, biosafety levels and safe handling of cultures before the practical program begins.
T2 · Naming and classifying microorganisms
Lecture 2Microbial taxonomy and the classification system, binomial nomenclature, and the features used to identify the major microorganisms found in food.
T3 · The bacterial cell
Lecture 3Anatomy of the bacterial cell, the Gram-positive versus Gram-negative cell wall, endospores, and the structures that matter for survival and identification.
T4 · Fungi: yeasts and moulds
Lecture 4Yeast and mould structure and classification, sexual and asexual reproduction, mycotoxins, and the dual role of fungi in food spoilage and in fermentation.
T5 · Bacteriophages
Lecture 5What bacteriophages are, the lytic and lysogenic cycles, and their applications, advantages and disadvantages in the food industry (a recurring exam theme).
T6 · Microbial analysis: media and methods
Lecture 6Microbial culture media, selective and differential media, plate counts and the principles of isolating and enumerating microorganisms from food.
T7 · Microbial metabolism
Lecture 7How microorganisms generate energy: aerobic respiration versus fermentation, glycolysis and ATP yield, oxygen classes, and malolactic fermentation (MLF) and its inhibitors.
T8 · Microbial growth and controlling factors
Lecture 8The growth curve (lag, log, stationary, death), binary fission and exponential growth, the difference between doubling time and specific growth rate, and the intrinsic and extrinsic factors (temperature, pH, water activity) that control growth in food.
T9 · Microbial hazards and food safety
Lecture 9Classes of disease-causing microorganisms, infection versus intoxication, exotoxins and endotoxins, and the strategies that minimise the risk of food poisoning.
T10 · Microbial identification
Lecture 10Conventional identification methods and their limitations, the contrast with rapid and molecular methods, and what validation and evaluation of an analysis method mean.
T11 · Predictive microbiology
Lecture 11Summarising microbial growth responses to environmental factors as mathematical models, the advantages of predictive microbiology, and how predictions are made and used in food safety.
T12 · Microbial inactivation
Lectures 12 to 13Thermal and non-thermal inactivation, D and z values, the principles behind heat processing, and bacteriocins as natural antimicrobial agents.
How it's assessed
Assessment structure
| Component | Weight | Format & timing |
|---|---|---|
| Fortnightly quizzes (6) | 10% | Six online quizzes on the LMS, one every fortnight, 10% combined; MCQ-style, similar to the mid-semester MCQ section. One quiz roughly every two weeks across the semester. Low stakes; all six together are worth only 10%. |
| Practical report | 20% | One written report of 1000 words based on the laboratory program and the data generated in practicals (made available via the LMS). Submission opens 11 May; due 18 May by 5pm (S1 2026 dates, subject to change). Independent scientific writing; marked on method, analysis and report writing. |
| Mid-semester exam | 20% | Closed-book written exam, 1 hour: Section A short-answer questions answered in full sentences with examples, plus Section B MCQs; basic calculator permitted. S1 2026 sitting was 16 April, 4:00 to 5:00pm (date subject to change). Covers the first half of the subject; answer in full sentences and give examples. |
| Final exam | 50% | Closed-book written exam, 2 hours: short-answer questions answered in full sentences with examples (define-and-explain and applied scenarios); basic calculator permitted. Formal examination period. Covers the whole subject; the largest single component. |
- Pass on a weighted average of at least 50%. No single-component hurdle is stated in the subject materials reviewed.
- Both written exams are dominated by short-answer questions answered in full sentences, where the marker rewards a clear mechanism plus a worked example (for instance: define bacteriophages and explain their food-industry uses; compare bacterial and fungal spores; explain the growth equation N = N0 e^(ut) with an example). The mid-semester exam adds an MCQ section similar to the fortnightly quizzes.
- Calculator policy: Closed-book exams. Students may have access to a basic calculator (needed only for the growth calculation and plate-count arithmetic).
This is an exam-cram unit. With the exams at 70% of the grade and the final exam alone at 50%, your result is overwhelmingly decided by how well you perform under time pressure. Covers the whole subject; the largest single component.
Final exam timing: approx mid-to-late Nov 2026 (estimated S2 offering; the source materials are the S1 2026 offering, so confirm the date and the offered semester against the official University of Melbourne exam timetable). Confirm the exact date and venue on the official exam timetable.
How to actually pass it
A weekly rhythm, two checklists, and the traps to avoid
The unit rewards consistency over cramming, and practice over re-reading. Here is the loop that works, then what to have nailed before each exam.
The weekly loop
Before the mid-semester checklist
- Drill the first-half topics (lab safety, classification, the bacterial cell, fungi, bacteriophages, microbial analysis) as short-answer questions answered in full sentences with examples.
- Rehearse the recurring questions: define bacteriophages and their food-industry uses, the classes of disease-causing microorganisms, and what validation and evaluation of an analysis method mean.
- Practise the Section B MCQ style using the fortnightly quizzes, since the mid-semester MCQs are similar.
- Confirm you can compare bacterial and fungal spores and explain why spores resist harsh conditions, a common cross-topic question.
Before the final heaviest topics
- Cover the whole subject, but give extra time to the higher-weight back half: microbial growth, foodborne hazards, identification, predictive microbiology and inactivation.
- Practise the growth calculation timed: n = t / g, N = N0 × 2^n, confirm with N = N0 e^(ut), and report log10 N.
- Rehearse the applied scenario question (for example, the spoiled-can-of-meat problem): explain the likely organism and changes, then the analysis method to isolate and identify it.
- Prepare define-and-explain answers for metabolism (respiration versus fermentation, MLF and its inhibitors), exotoxin categories, and the mechanisms of genetic transfer in bacteria.
The mistakes that cost marks
Answering in bullet lists instead of full sentences. The exam instructions explicitly ask for full-sentence answers with examples. A list of keywords loses the explanation and example marks even when the facts are right. Practise writing the answer as a short structured paragraph: definition, mechanism, food example.
Treating the quizzes and report as the main event. The six fortnightly quizzes are 10% combined and the practical report is 20%. The two closed-book written exams are 70% of the grade. Polishing quiz and report marks while underpreparing for the written exams misreads where the marks sit.
Skipping the growth calculation. It is the one quantitative item that reliably appears, and it is easy marks once practised. The common slips are forgetting to multiply by N0 (so quoting 2^n instead of N0 × 2^n) and not converting the hold time and generation time to the same units before computing n = t / g.
Memorising lists without the food link. Naming organisms or factors without explaining how each one spoils food, causes illness, or is controlled is exactly the gap the applied scenario questions probe. Tie every organism to its growth-limiting factor and its inactivation or control step.
Teaching team
Who teaches FOOD90023
The bios below are factual. The star ratings are not ours: they are impressions from students who have taken the unit, so you can hear from people who sat in the lectures.
A/Prof Said Ajlouni
Associate Professor in the School of Agriculture, Food and Ecosystem Sciences at the University of Melbourne, coordinating and lecturing FOOD90023 Food Microbiology in the Master of Food Science.
Teaching team as listed in the unit materials reviewed. AskSia does not rate lecturers; star ratings are submitted by students who have taken FOOD90023.
What students say
What students actually say about FOOD90023
Recurring themes from student reviews, paraphrased in our own words.
- Read as a broad but moderate postgraduate subject: lots of conceptual food microbiology to absorb rather than heavy quantitative work.
- The pressure point is that most of the grade is two closed-book written exams where answers must be in full sentences with examples, so understanding matters more than rote lists.
- The back-half topics (hazards, identification, predictive microbiology, inactivation) carry the most exam weight and reward steady revision over cramming.
- The subject follows the Ray and Bhunia text and the LMS lecture videos closely, with a live webinar each week for applications.
- Students build short-answer practice and concise summaries of the recurring exam themes (bacteriophages, spore comparison, the growth equation) to prepare for the written exams.
- Demand for clear, worked walkthroughs of the microbial growth calculation and structured model answers for the common short-answer questions.
Recurring student opinions, paraphrased and aggregated, not official course information.
Set texts
The prescribed reading
The syllabus references map straight onto these.
Fundamental Food Microbiology
Bibek Ray and Arun Bhunia.
Where it fits
Prerequisites, related units & why it matters
Postgraduate subject in the Master of Food Science. Entry assumes eligibility for an honours or postgraduate coursework program, with recommended background knowledge in chemistry and/or biology. It is not available as a breadth subject.
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FAQ
Frequently asked questions
Is FOOD90023 hard?
It is moderate for a postgraduate subject. The content is broad conceptual microbiology rather than heavily quantitative, so there is little number-crunching beyond the growth calculation. The challenge is that 70% of the grade is two closed-book written exams where you answer short-answer questions in full sentences and must back each point with an example, so it rewards genuine understanding and clear scientific writing over memorised lists.
How is FOOD90023 assessed?
Six fortnightly quizzes worth 10% combined, a 1000-word practical report worth 20% (S1 2026 due 18 May), a 1-hour mid-semester written exam worth 20%, and a 2-hour final written exam worth 50%. You pass on a weighted average of at least 50%, with no single-component hurdle stated in the materials reviewed. The two written exams together are 70% of the grade.
What is the exam format?
Both exams are closed-book and written. They are dominated by short-answer questions that you answer in full sentences with examples (for instance, define bacteriophages and explain their food-industry uses, or compare bacterial and fungal spores). The mid-semester exam also has an MCQ section similar to the fortnightly quizzes. A basic calculator is permitted, mainly for the growth calculation.
How much maths is involved?
Very little. The main quantitative item is the microbial growth calculation, N = N0 × 2^n and the equivalent N = N0 e^(ut) with the specific growth rate u = ln 2 / g, plus basic plate-count and dilution arithmetic. A basic calculator is allowed. The rest of the subject is conceptual: classification, cell structure, metabolism, hazards, identification, predictive modelling and inactivation.
What textbook does FOOD90023 use?
The prescribed text is Ray, B. and Bhunia, A., Fundamental Food Microbiology, 4th edition (CRC Press, Taylor and Francis). Lectures are delivered as LMS videos followed by a live Zoom or webinar session, and the weekly laboratory practicals are set out in the Laboratory Manual, which you should read before each session.
Is there a lab component, and how does the report work?
Yes. A practical laboratory program runs alongside the lectures and emphasises modern instrumental microbiological techniques; the data generated in the practicals are made available on the LMS. You write one 1000-word practical report worth 20% (S1 2026 submission opened 11 May, due 18 May by 5pm). It is marked on independent scientific writing, so read each week's practical in the Laboratory Manual before the session.
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