Food Microbiology Classic Questions and Answers
Multiple choice questions:
1. Which of the following are prokaryotic microorganisms (bacteria). 2. The first person to discover microorganisms was (Leewenhoek)
3. In the second period of the development of microbiology, (Pasteur and Koch) laid the foundation. 4. The main component of the capsule is (sugar).
5. Use to measure the size of bacteria (microns). 6. The main component of the cell wall is (peptidoglycan).
7. For culturing yeast (maltose agar). 8. The general conditions for culture medium sterilization are (121°C for 15 minutes).
9. The characteristics of actinomycete colonies are (dry and wrinkled). 10. The main asexual reproduction of yeast is (budding).
11. The main reproduction method of mold is (sporulation). 12. Aspergillus spores are (exospores). 13. Mold colonies are (larger) than those of yeast.
14. Which description of viruses is wrong (sensitive to antibiotics). 15. Viruses have (a type of nucleic acid). 16. Bacteriophages can be used for (diagnosis and treatment). 17. Those that can lyse bacteria and actinomycetes are (cleavage phages). 18. What can be used for bacterial identification and typing is (phage).
19. The total number of bacteria is measured (the number of all living bacteria). 20. The most approximate value of coliform bacteria measured in (100) milliliters or grams of food sample. 21. The method for measuring the number of coliforms is (37) °C. 22. The temperature for cultivating yeast is usually (28) °C.
23. The amount of agar added to the solid culture medium is (2)%. 24. The time for complete determination of coliform bacteria is (72) hours.
25. Botulinum toxin releases (exotoxins). 26. What has an inhibitory effect on breadstick disease (calcium propionate)
27. Fruit juice and fruit wine can generally be preservative (sodium sulfite). 28. The commonly used preservative in beverages is (sodium benzoate).
29. The most commonly used food sterilization method is (pasteurization). 30. The permeability of sucrose at the same percentage concentration is 10% worse than that of table salt.
31. GMP is (Good Manufacturing Practice). 32. It is an anaerobic microorganism (Botulinum toxin).
33. The optimal concentration of alcohol disinfection is (75)%. 34. The following are non-cellular microorganisms (viruses).
35. The first person to use solid culture media was (Koch). 36. The main component of spore heat resistance is (DPA).
37. Use (microns) to measure the size of bacteria. 38. The main component of the cell wall is (peptidoglycan).
39. The main component of flagella is (protein). 40. The characteristics of yeast colonies are (sticky, larger).
41. The reproduction of viruses is mainly (sporulation). 42. The main reproduction method of mold is (sporulation).
43. Penicillium spores are (exospores). 44. Which description of the virus is wrong (individuals are very small). 45. Viruses have (two kinds of nucleic acids).
46. Bacteriophages can be used to (identify bacteria). 47. Those that can lyse bacteria and actinomycetes are (cleavage phages).
48. What can be used for bacterial identification and typing is (rhizomes). 49. The total number of bacteria is measured (acetic acid bacteria).
50. The number of coliform bacteria measured is the most approximate value of coliform bacteria per (1) milliliter or gram of food sample.
51. When making semi-solid culture medium, the amount of agar added is (5)%. 52. The complete coliform determination time is (one day) hours.
53. Staphylococcus aureus releases (exotoxins). 54. What has an inhibitory effect on breadstick disease is (sodium benzoate)
55. Fruit juice and fruit wine can generally be preservative (potassium sorbate). 56. Microorganisms occupy (4) kingdom in the biological world classification system.
57. The prokaryotic microorganisms are (actinomycetes). 58. The first scientist to use agar was (Koch).
59. The main component of flagella is (protein). 60. Use (microns) to measure the size of bacteria.
61. The main component of the spores that can resist adverse environments is (DPA) 62. The main component of the capsule is (polysaccharide).
63. The conditions for sterilization of lactose-containing culture media are (a 115°C for 30 minutes). 64. The characteristics of mold colonies are (velve-like, cotton-like).
65. The main asexual reproduction of Carlsbergia yeast is (budding). 66. Rhizopus spores are (endospores).
67. Which description of viruses is wrong (sensitive to antibiotics). 68. Viruses have (a type of nucleic acid).
69. Bacteriophages can be used for (diagnosis and treatment). 70. Those that can lyse bacteria and actinomycetes are (lytic phages).
71. What can be used for virus identification is (inclusion body). 72. The total number of bacteria is measured (the number of all living bacteria).
73. For the plate counting method, (37)°C is used. 74. The amount of agar added to the solid culture medium is (2)%.
75. The complete measurement time of coliform bacteria is (72) hours. 76. Botulinum toxin releases (exotoxins) toxins.
77. What has the inhibitory effect on bread sticky disease is (calcium propionate). 78. Fruit juice and fruit wine can generally be preserved with (sodium sulfite).
79. The commonly used preservative in beverages is (sodium benzoate). 80. The sterilization method used for long-term milk is (ultra-high temperature instant sterilization).
81. The permeability of glucose at the same concentration is (smaller) than that of table salt. 82. Generally, the place with the largest number of microbial species is (soil).
83. The direct counting method counts (larger) than the objective and actual value. 84. Which of the following are prokaryotic microorganisms (actinomycetes).
85. The first person to discover microorganisms was (Leewenhoek). 86. Pathogenic microbiology was founded by (Koch).
87. The main component of the cell wall is (peptidoglycan). 88. The characteristics of actinomycete colonies are (dry and wrinkled).
89. The main reproduction method of viruses is (replication). 90. Aspergillus spores are (exospores).
91. Which description of viruses is correct (non-cellular structure). 92. Viruses have (a type of nucleic acid).
93. What can prove the existence of phage is (phage plaque) 94. What can lyse bacteria and actinomycetes is (fission phage).
95. What can be used for bacterial identification and typing is (phage). 96. The microorganism with the strongest resistance to adverse environments is (Bacillus).
97. The total number of bacteria measured is the most approximate value of coliform bacteria per (100) ml or gram of food sample.
98. The method of measuring the number of coliform bacteria is the (lactose bile salt) culture medium. 99. Staphylococcus aureus produces (exotoxins) toxins.
100. The substance that inhibits bread stickiness is (calcium propionate). 101. The commonly used preservative in beverages is (sodium benzoate).
102. The sterilization method for acidic food is (pasteurization). 103. The permeability of salt at the same concentration is (larger) than that of maltose.
104. The largest number of microbial species in the air (Gram-positive bacteria). 105. Lactic acid bacteria are commonly used for yogurt fermentation.
106. Which structure can bacteria lack and still survive (cell wall). 107. The largest group and number of microorganisms in nature are (chemoheterotrophic microorganisms). 108. The optimal concentration of alcohol disinfection is (75)%. 109. Which description of the virus is correct (obligate parasitism).
110. Viruses have (enzyme deficiency). 111. Actinomycetes can be used to (prepare antibiotics). 112. What can be used for mold identification and classification is (rhizoids).
113. The direct counting method determines (the number of total viable bacteria). 114. The first person to use agar to culture microorganisms was ( )
115. It was Watson and Crick who discovered the structure of nucleic acids and laid the foundation. 116. The main component of the capsule is (sugar).
117. Use to measure the size of yeast (microns) 118. The main asexual reproduction of yeast is (budding). 110. The main reproduction method of mold is (sporulation). 120. Aspergillus spores are (exospores). 121. The amount of agar added when cultivating solid culture media is (2)%.
122. Botulinum toxin releases (exotoxins) toxins. 123. What has an inhibitory effect on breadstick disease (calcium propionate)
124. The commonly used preservative in carbonated drinks is (sodium benzoate). 125. The sterilization method for canned green beans is (ultra-high temperature sterilization).
126. The permeability of maltose and salt at the same concentration (salt is larger). 127. The main raw material in the fermentation industry is (starch).
128. The anaerobic microorganism is (Bacillus tetani). 129. Which structure can bacteria still survive without (cell wall).
130. The largest group and number of microorganisms in nature are (chemoheterotrophic microorganisms).
2. Fill in the blanks:
1. The structure of a bacterial cell from the outside to the inside is (bacterial wall), (bacterial membrane), (bacterial plasm), (bacterial nucleus), and the special structures of bacterial cells are (spore), (flagella), (capsule).
2. The reproduction method of bacteria is 44 (fission), the main reproduction method of yeast is 45 (budding), and the reproduction method of viruses is 46 (replication).
3. The culture medium is divided into three types according to its purpose (enriched medium), (selective medium), and (identification medium). According to its components, it is divided into (natural culture medium), (synthetic culture medium), and (semi-synthetic culture medium).
4. The key to Gram staining is (alcohol decolorization) and the alcohol concentration used is (95%).
5. The main way of virus reproduction is (replication).
6. Methods for preserving bacterial strains include (low temperature preservation method), (drying preservation method), (air isolation preservation method), (vacuum freeze-drying preservation method) 44
7. The steps for isolating and screening bacterial strains from nature include (sampling), (propagation culture), (pure species isolation), (pure culture), and (production performance measurement).
8. The reproduction method of mold is (spore reproduction), the reproduction method of bacteria is (binary fission), and the main reproduction method of yeast is (budding).
9. Food microbiology is the study of (morphological structure and physiological characteristics), (application of beneficial microorganisms), (control process of food deterioration), (microorganisms related to food hygiene)
10. Commonly used preservatives in beverages are (sodium benzoate) and (potassium sorbate).
11. The four phases of the single cell growth curve are (adaptation phase), (logarithmic phase), (equilibrium phase), and (decline phase).
12. Dry heat sterilization methods include (flame sterilization), (dry air sterilization method) and moist heat sterilization methods include (pasteurization), (high-pressure steam sterilization method), (intermittent sterilization method), (Boiling sterilization method).
3. Short answer questions:
1. What are the characteristics and main groups of microorganisms?
Bacteria, yeast, actinomycetes, molds, viruses
Its body is tiny, measured in microns, its structure is simple, single-celled or cell-free, its growth and reproduction are fast, its metabolism is strong, its effects are great, and its genetic stability is poor and it is easy to mutate.
2. What are the forms of viruses? What are the characteristics of viruses?
Strong rod, filamentous, elastic, brick-shaped, tadpole
They are extremely small, have no cell structure, are obligate parasites, have little resistance to nature, and have no specific effect on antibiotics.
3. What principles should be followed when preparing culture media?
It must comply with the nutritional characteristics of microbial strains. For example, yeast and mold need a higher carbon-nitrogen ratio, and bacteria need more nitrogen. Lactic acid bacteria need to be cultured with amino acids and vitamins, and some microorganisms need to add growth factors.
It is clear whether the cultured bacteria are secondary metabolites, and then the nutrient ratio is determined according to the purpose.
A low carbon-nitrogen ratio in fermented seeds means a high nitrogen content, and a high carbon-nitrogen ratio for the accumulation of secondary metabolites.
Appropriate pH is very important for the growth of microorganisms. Bacteria are neutral, yeasts and molds are acidic, and attention should be paid to the adjustment of pH during the metabolic process.
To adjust the appropriate osmotic pressure to adapt to microorganisms
4. What is a single cell growth curve and what are the characteristics of each phase.
Single-cell microorganisms or multi-cell microorganisms are inoculated into a liquid environment to grow. The curve drawn with the growth time as the horizontal axis and the logarithm of the number of bacteria as the ordinate is divided into an adaptation period, a logarithmic period, an equilibrium period, and a decline period.
During the adaptation period, the number of bacteria decreases, their growth and reproduction is zero, their metabolism is active, and they are sensitive to the external environment.
In the logarithmic phase of cell division, there are more secondary metabolites in the intense equilibrium phase, and antibiotics are generally used during this period.
5. What are the methods for sterilizing food, and give examples.
Pasteurized beer, wine, milk, acidic foods
UHT sterilized canned food, cold sterilized meat, UHT instant sterilized milk
6. What are the stages in the development of microbiology, which mainly represent scientists and their main contributions?
Speculation period Observation period Leeuwenhoek observed the physiological period of microorganisms Pasteur, Koch vaccine, pasteurization, solid culture medium molecular biology period Watson nucleic acid structure
7. What are the main structural components and reproduction process of viruses?
Protein shell, only one nucleic acid, and no complete enzyme system
Adsorption - invasion - deshelling - biosynthesis - assembly and release
8. What is a microbial growth curve and which periods it is divided into.
Single-cell microorganisms or multi-cell microorganisms are inoculated into a liquid environment and grow for a lifetime. The horizontal axis is the horizontal axis and the logarithm of the number of bacteria is the vertical axis. The curve is divided into adaptation period, logarithmic period, equilibrium period and decay period.
9. What is the coagulant added to the solid culture medium and what are its characteristics?
Agar is not used by microorganisms. It melts at 100 degrees and solidifies at 45 degrees. It does not melt like gelatin when cultivating microorganisms. It is a good coagulant and can be used to observe the colony morphology of microorganisms.
10. Methods and steps for screening microbial strains from nature.
Sampling - enrichment culture - pure strain isolation and streaking - pure culture - production performance measurement
11. What are the special structures of bacterial cells, their main components and functions.
Because DPA is extremely resistant to adverse environments, spores are used in sterilization tests.
Flagellar proteins have motility functions such as Salmonella
The polysaccharide structure secreted by encapsulated bacteria outside the cells has pathogenic and protective properties.
12. What are carbon sources, nitrogen sources, and carbon-nitrogen ratios.
Substances that can provide carbon sources, such as sugars, substances that can provide nitrogen sources, peptone,
C/N is the ratio of the molar concentration of carbon atoms to nitrogen atoms, which has a great influence on the accumulation of fermentation products. Seed cultivation requires more nitrogen, and secondary product cultivation increases carbon.
13. What is homofermentation and what is heterofermentation?
The product produced by homofermentation is lactic acid. In addition to lactic acid, heterofermentation also produces ethanol and other substances.
14. What are the measurement methods for microbial growth?
Plate counting, hemocytometer, scale dry weight, turbidimetry
15. What fermented foods and related products can be produced using bacteria, yeast, and mold.
Bacterial vinegar, yogurt, MSG yeast wine, bread, vitamins
Mold sauce, soy sauce, bean curd, citric acid, amylase, pectinase
16. What are the ways microorganisms absorb nutrients?
Simple diffusion, facilitated diffusion, active transport, group translocation
17. What are the methods for sterilizing food, and give examples.
Pasteurization, milk, beer, soy sauce, acid food, boiling sterilization, liquid food
Ultra-high temperature sterilization of canned food targets spores and anaerobic bacteria
18. What are infectious food poisoning and toxin food poisoning?
Food poisoning is caused by eating food that contains a lot of bacteria, such as salmonella
Food poisoning is caused by eating foods that contain large amounts of toxins, such as Staphylococcus aureus
19. What are the types of microbial nutrition, and give examples.
Chemoautotrophic photoautotrophic chemoheterotrophic bacteria saprotrophic, parasitic photoheterotrophic
20. What are the characteristics of food poisoning?
In summer and autumn, outbreaks occur when dining together in collective canteens, not contagious, short incubation period, gastrointestinal symptoms of vomiting and diarrhea
21. Why is it necessary to adjust the pH when preparing culture media, and how to adjust it?
Different strains of bacteria require different pH, such as yeast, acidic, and bacteria neutral.
Use 0.1 sodium hydroxide, hydrochloric acid and test paper to adjust. Sometimes a buffer solution is used. For example, acid is produced after the metabolism of sugar, and alkali is produced after the metabolism of amino acids.
4. Essay questions:.
1. What microbiological indicators are included in the food hygiene standards? What are their food hygiene significances?
The first two commonly used are total number of bacteria, coliforms, and pathogenic bacteria.
Coliforms are a group of Gram-negative non-bacilli that ferment lactose and produce acid and gas.
Coliform bacteria come directly or indirectly from the feces of humans or warm-blooded animals. It is rare to come from other sources than feces. Therefore, coliforms are ideal fecal contaminants. The detection of enteric pathogenic bacteria Salmonella and Shigella is difficult. Enteric pathogenic bacteria and coliforms come from the same source, so coliforms are indicator bacteria of intestinal enteropathogenic bacteria.
The total number of bacteria can indicate the degree of food contamination. 10,000/square centimeter can be maintained at zero temperature for 6 days, and 1,000/square centimeter can be maintained for 12 days. The greater the number of bacteria, the easier it is to spoil.
2. What are the environmental factors for microbial growth? How to use this factor to promote fermentation production.
Temperature, moisture, oxygen, pH, osmotic pressure, chemicals
The temperature should be adjusted to the optimal growth temperature according to the low temperature of 10 to 15 degrees, the thermophilic temperature of more than 45 degrees, and the mesophilic temperature of 20 to 28 degrees and 37 to 45 degrees. The optimal pH, such as yeast and mold, should be adjusted to 4 to 5.8. Osmotic pressure: Hypertonic microorganisms need to add an appropriate amount of salt to meet their growth needs.
Moisture and oxygen: For microbial growth, the water activity needs to be above 0.9 for bacteria and above 0.88 for yeast.
Only by adjusting environmental factors to the most suitable conditions for the microorganism can fermentation production be promoted. Regulate nutritional carbon to nitrogen ratio
3. The ways in which microorganisms contaminate food and their control measures.
Soil, air, water, people and animals carried, processing machinery, packaging materials, raw materials and auxiliary materials
a Strengthen the hygiene management of the production environment b Strictly control pollution during the processing process c Pay attention to the hygiene of storage, transportation and sales
4. Discuss the principles and methods of food preservation from the perspective of microorganisms.
It is to prevent the reproduction of microorganisms, control the temperature below the growth temperature, the water activity below the growth of microorganisms, and isolate the air from the packaging. Frozen meat, refrigeration, pasteurized milk, high-temperature sterilized cans, dried milk powder and flour, osmotic pressure pickled salt and sugar, packaging to isolate air, add preservatives, and cold sterilization.
5. What is a single cell growth curve and how to use this curve to guide fermentation industrial production.
It is a curve drawn using time as the abscissa and the logarithm of the number of microorganisms as the ordinate. It is divided into an adaptation period, a logarithmic period, an equilibrium period, and a decline period.
When inoculating, select strains in the logarithmic phase. You can skip the adaptation period and enter the logarithmic phase directly. Try to keep the fermentation in the logarithmic phase and the equilibrium phase. The strains should be in the logarithmic phase. If you want metabolites, keep them in the equilibrium phase. It is necessary to continuously add nutrients, adjust the pH and temperature, and discharge metabolites to prevent it from entering the period of decline.
6. Principles and methods of microbial strain preservation.
Try to keep the bacteria in an environment where inactive growth and reproduction are restricted, such as conditions of dryness, low temperature, lack of oxygen, and lack of nutrients.
Low temperature preservation method: 0~4 degrees Celsius for 3 months. Dry preservation method: bran, soil, sand
Isolated air preservation method, liquid sterile paraffin vacuum refrigeration and drying preservation method plus strain preservation agent
7. Discuss the principles and methods of food preservation from the perspective of food matrix factors and external factors.
Water activity, pH, osmotic pressure, temperature, air, preservatives
Dried: milk powder, flour, sugar and salted; preserved fruit sterilized and sealed: canned
Vacuum deoxygenation preservatives such as sodium benzoate inhibit yeast and mold cold sterilization: meat, grains smoked: sausages
8. What are the applications of bacteria, molds and yeasts in the food industry.
Traditional fermented foods, enzyme preparation bacteria: yogurt, vinegar, MSG, enzyme preparation,
Mold: wine, bread, yeast: soy sauce, paste, pectinase