Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
192 Cards in this Set
- Front
- Back
|
Primary sources of microorganisms in foods
|
Inhabitants
Transients |
|
|
Primary sources of microorganisms in foods
|
Soil and Water
Plants and Plant Products Food Utensils Gastrointestinal Tract Food Handlers Animal Feeds Animal Hides Air and Dust |
|
|
Factors associated with food spoilage
|
Color defects
Undesirable changes in texture Off-odor development Off-flavor development Slime development Any other changes making food undesirable |
|
|
Spoilage is typically from what?
|
Microbial action
|
|
|
Initial microflora on food is what?
|
Highly variable
|
|
|
What happens to microbial diversity as spoilage progresses and what influences this?
|
Diversity become less.
Influenced by storage and packaging conditions. |
|
|
Spoilage characteristics at ~10^6-7
|
Defects may be noticed
|
|
|
Spoilage characteristics at >=10^7
|
Off odors noticed
|
|
|
Spoilage characteristics at >=10^8
|
Tacky/slime formation starts
|
|
|
Types of microbial changes
|
Proteolysis/Putrefaction
Lipolysis Fermentative Spoilage |
|
|
What is Proteolysis/Putrefaction?
|
Aerobic/Anaerobic decomposition of proteins
Decarboxylation and deamination can occur |
|
|
How does Proteolysis/Putrefaction occur?
|
Proteins are decomposed by proteases to amino acids, peptides, ammonia, and H2S
|
|
|
What is Lipolysis and how does it occur?
|
Usually a later type of spoilage where lipids decompose
Fats are degraded by lipases to fatty acids and glycerol |
|
|
What is fermentative spoilage and how does it occur?
|
Desirable or undesirable fermentation
CHO (carbs) are broken down to lactic, btyric, propionic acids, CO2, alcohols, etc |
|
|
When does Pseudomonas usually produce proteases and lipases?
|
Typically during late log phase around >= 10^8 cfu/cm2.
|
|
|
In what order does microbial enzymatic use usually occur?
|
Carbohydrates then amino acids/proteins then fatty acids/lipids
|
|
|
What odors and flavors occur due to microbial enzymatic activities and why?
|
Sour, cheesy, acid due to short chain fatty acids and amines.
|
|
|
What types of microbes are usually responsible for fermentation?
|
Usually bacteria and yeasts
|
|
|
What are some Foodborne Bacterial Pathogens?
|
Arcobacter
Bacillus - anthracis, cereus Campylobacter Clostridium - botulinum, perfrigens Escherichia coli [Enterohemorrhagic, Enteroinvasive, Enteropathgenic, Enterotoxigenic] Listeria monocytogenes Salmonella Shigella Staphylococcus aureus Vibrio - cholerae, parahaemolyticus, vulnificus Yersinia enterocolitica |
|
|
What are some Foodborne Viral Pathogens?
|
Hepatitis A
Norwalk and Norwalk-like |
|
|
What are some Foodborn Parasitic Pathogens?
|
Cryptosporidium parvum
Cyclospora cayetanensis Entamoeba histolytica Giardia lamblia Toxoplasma gondii |
|
|
What are some other microbial-related illnesses?
|
Histamine poisoning
Toxogenic phytoplanktons - Shellfish and Ciguatera poisoning |
|
|
What are the factors affecting microbial growth and survival?
|
Water content
Environmental temperature pH Oxidation-Reduction potential Nutrients Presence/Absence of antimicrobials Other microflora Processing treatment |
|
|
What criteria is used to determine bacterial taxonomy?
|
Phenotypic, Genetic (16S RNA/DNA), Phylogenetic
|
|
|
What are the uses of fungi in foods?
|
Products - soy sauce, beer, wine, breads, some cheeses, etc
Other - production of organic acid |
|
|
What are the bad aspects of fungi?
|
Rot crops
Clogs production lines Scum Production of off-odors or flavors Mycotoxins |
|
|
What are common characteristics of fungi?
|
Eukaryotic
Heterotrophic - Excrete extracellular enzymes, Degrade substrates, Absorb dissolved nutrients Can be filamentous Cell wall of Cellulose and/or Chitin Reproduction - sexual & asexual, asexual only, uncertain No chlorophyll No means of locomotion |
|
|
What are some ways to preserve food?
|
Low/Reduced temperature
High temperature Antimicrobials (preservatives) Radiation Modified atmospheres Drying High pressure processing Pulsed electric fields Aseptic packaging Combination Hurdles |
|
|
What are the three basic types of factors affecting microbial growth?
|
Intrinsic Parameters that are inherent to plants and animals, which can influence microbial activities
Extrinsic Parameters Hurdle Technology |
|
|
What are the stages of microbial growth?
|
Lag, Log, Stationary, Death
|
|
|
What occurs during the lag phase?
|
Cells induce or repress enzyme synthesis and activity
Initiate chromosomes and plasmid replication If they are spores they differentiate into vegetative cells |
|
|
What does the length of the lag phase depend on?
|
Temperature
Inoculum size Physiological state of the organism Also actively growing cells transferred to new environment have shorter lags The environment can be manipulated to extend lag |
|
|
What occurs in the Log (Exponential) phase?
|
Bacterial cells reproduce by binary fission
|
|
|
What is the number of organisms at any time during the log phase directly proportional to?
|
Initial number of microorganisms
|
|
|
What is the temperature effect during the log phase?
|
A decrease of 10 deg C will decrease the growth rate by 2-fold
|
|
|
What conditions should be considered in regards to temperature?
|
Initial load
Size Time & temperature of storage, stock rotation Temperature constancy Packaging - helps keep product clean and dry; may insulate |
|
|
How do low temperatures affect microorganisms?
|
Primarily restrict growth so not effective for bacteria or fungal population but some eukaryotic organisms susceptible
|
|
|
What is the optimum temperature range for thermophiles?
|
55-75 C
|
|
|
What is the minimum temperature range for Thermophiles?
|
40-45 C
|
|
|
What is the optimum temperature range for Mesophiles?
|
30-45 C
|
|
|
What is the optimum temperature range for Psychrotrophs?
|
25-30 C
|
|
|
What is the optimum temperature range for Psychrophiles?
|
12-15 C
|
|
|
What is the minimum temperature range for Mesophiles?
|
5-15 C
|
|
|
What is the minimum temperature range for Psychrotrophs?
|
-5 - +5 C
|
|
|
What is the minimum temperature range for Psychrophiles?
|
-5 - +5 C
|
|
|
What is the maximum temperature range for Thermophiles?
|
60-90 C
|
|
|
What is the maximum temperature range for Mesophiles?
|
35-47 C
|
|
|
What is the maximum temperature range for Psychrotrophs?
|
30-35 C
|
|
|
What is the maximum temperature range for Psychrophiles?
|
15-20 C
|
|
|
What effect does freezing have as a process in relation to microorganisms?
|
Higher organisms like parasites are sensitive while spores are resistant.
Toxins C. botulinum and S. aureus are stable Gram positives are usually more resistant than gram negatives |
|
|
How problematic are pathogens in frozen foods?
|
Pathogen problems are rare as most frozen food is cooked prior to consumption
|
|
|
What are the factors affecting heat resistance?
|
Spores (inherent resistance)
Cell type and number Growth conditions -Stage of growth -Growth temperature -Growth medium Heating environment -ph (Most Important >8 & <6) -Moist heat more effective -Salts -Sucrose -Fat -Protein |
|
|
What does the time/temperature relationship depend on?
|
Type of food
Quantity Liquid/Solid |
|
|
What is the typical cooking temperature?
|
160F (71 C)
|
|
|
What is the typical warming temperature?
|
140F (60 C)
|
|
|
What does blanching do to microbes?
|
Kills a sizable portion of the population, but this is not the primary purpose of blanching
|
|
|
What is pasteurization?
|
Heating sufficient to destroy vegetative forms of pathogens of concern.
Destroys most or all of the vegetative, spoilage microorganisms Usually used in combination with additional factors like refrigeration |
|
|
What is commercial sterility?
|
Thermal treatment that eliminates all microorganisms except thermophilic spores
|
|
|
What pH are low acid foods and what is special about them?
|
> 4.6
Must be canned using steam under pressure for sufficient time |
|
|
What pH are Acid foods?
|
4.6 and below
|
|
|
Where is the Commercial Sterility of Thermally Processed Foods defined?
|
Code of Federal Regulations
|
|
|
What is the D-value?
|
A measure of the heat resistance of a microorganism at a specific temperature.
Time in minutes required to kill 90% (1 log) of population. Size of initial load important. Pasteurization based on 12D Concept |
|
|
What is the Z-value?
|
Thermal death curve - relative heat resistance of a microbe at different temperatures.
The temperature required for a reduction of the D-value by 1 log. |
|
|
Gr- rods; aerobic; related to Pseudomonas; plant inhabitants
|
Acidovorax
|
|
|
G- rods; strict aerobes; common in soils and waters; common on fresh refrigerated food products
|
Acinetobacter
|
|
|
G- rods; aquatic; gas produce from fermented sugars
|
Aeromonas
|
|
|
G- rods; Produce alkaline products from sugars; widely distributed in nature (e.g., compose material)
|
Alcaligenes
|
|
|
Gr+ rods; thermoacidophilic; sporeformers; related to Bacillus species
|
Alicyclobacillus
|
|
|
G- rods; strict aerobes; marine inhabitants; found on seafood; require seawater salinity for growth
|
Alteromonas
|
|
|
G- curved rods; similar to Campylobacter except they grow at 15C and are aerotolerant; found on poultry, pork and some other animal
products |
Arcobacter
|
|
|
G+ sporeforming rods; aerobic; most species are mesophilic; common in soil and water
|
Bacillus
|
|
|
G+ sporeforming rods; common in soil, water, dust and on plants; formerly classified as Bacillus
|
Brevibacillus
|
|
|
G+ rods; closely related to Lactobacillus and Listeria; also share characteristics with Microbacterium; common on refrigerated processed meat and seafood products packaged in gas-impermeable packages
|
Brochothrix
|
|
|
G- rods; formerly classed as Pseudomonas; found on plants and in raw milk; associated with cystic fibrosis patients
|
Burkholderia
|
|
|
G- spiral-shape rods; mesophilic;
microaerophilic to anaerobic; found on poultry and in raw milk |
Campylobacter
|
|
|
G+ rods; previously classified as
lactobacilli; heterofermentative; can grow at 0C; found on vacuum-package meats, fish, poultry |
Carnobacterium
|
|
|
G- rods; mesophilic; found on vegetables and fresh meats
|
Citrobacter
|
|
|
G+ sporeforming rods; anaerobic; most are mesophilic; widely distributed
|
Clostridium
|
|
|
G+ rods; most are mesophilic, some
psychrotrophs; can spoil meat and vegetable products |
Corynebacterium
|
|
|
G- rods; facultative anaerobic; mesophilic; yields positive coliform test; generally not adapted to the gastrointestinal tract
|
Enterobacter
|
|
|
G+- cocci; formerly known as “fecal
streptococci”; can be found in fecal material |
Enterococcus
|
|
|
G- rods; common on plants
|
Erwinia
|
|
|
G- rods; facultative anaerobic; mesophilic; common in fecal material; yields positive coliform and fecal coliform tests
|
Escherichia
|
|
|
G- rods; formerly classed as Pseudomonas; found on plants and in raw milk; associated with cystic fibrosis patients
|
Burkholderia
|
|
|
G- spiral-shape rods; mesophilic;
microaerophilic to anaerobic; found on poultry and in raw milk |
Campylobacter
|
|
|
G+ rods; previously classified as
lactobacilli; heterofermentative; can grow at 0C; found on vacuum-package meats, fish, poultry |
Carnobacterium
|
|
|
G- rods; mesophilic; found on vegetables and fresh meats
|
Citrobacter
|
|
|
G+ sporeforming rods; anaerobic; most are mesophilic; widely distributed
|
Clostridium
|
|
|
G+ rods; most are mesophilic, some
psychrotrophs; can spoil meat and vegetable products |
Corynebacterium
|
|
|
G- rods; facultative anaerobic; mesophilic; yields positive coliform test; generally not adapted to the gastrointestinal tract
|
Enterobacter
|
|
|
G+- cocci; formerly known as “fecal
streptococci”; can be found in fecal material |
Enterococcus
|
|
|
G- rods; common on plants
|
Erwinia
|
|
|
G- rods; facultative anaerobic; mesophilic; common in fecal material; yields positive coliform and fecal coliform tests
|
Escherichia
|
|
|
G- rods; found on plants; can contribute to spoilage of refrigerated meats and vegetables
|
Flavobacterium
|
|
|
G- rods; can contribute to spoilage of refrigerated meats and vegetables
|
Hafnia
|
|
|
G+ cocci; members were originally Micrococcus species
|
Kocuria
|
|
|
G+ rods; “lactic acid bacteria”; those in foods are typically microaerophilic; common on vegetables and in dairy products and refrigerated vacuum-packaged meats
|
Lactobacillus
|
|
|
G+ cocci; “lactic acid bacteria”; produce lactic acid as primarily end product of fermentation; formerly in the genus Streptococcus
|
Lactococcus
|
|
|
G+ cocci; heterofermentative; “lactic acid bacteria”
|
Leuconostoc
|
|
|
G+ rods; commonly found in the environment; L. monocytogenes can grow at refrigeration temperatures
|
Listeria
|
|
|
G+ coccus; can grow in presence of high salt levels
|
Micrococcus
|
|
|
G+ rods; sporeformer; some species related to either the Bacillus or Clostridium species
|
Paenibacillus
|
|
|
G- rods; common on/in plants, seeds, soil, water and humans; new species composed of former Erwinia and Enterobacter species
|
Pantoea
|
|
|
G+ cocci; “lactic acid bacteria”;
homofermentative; they can grow in 18% salt |
Pediococcus
|
|
|
G - rods; facultative anaerobic; mesophilic; common in the intestinal tract; swarming growth of agar plates; common on vegetable and meat products; can contribute to product spoilage
|
Proteus
|
|
|
G- rods; largest genus of bacteria found on fresh foods; common in/on soil, water, vegetables, meat, poultry, seafood; aerobic; many species can grow at refrigeration temperatures
|
Pseudomonas
|
|
|
G- rods; species were once included in Acinetobacter or Moraxella species; aerobic; can grow in 6.5% salt; found on meats, poultry, fish and in water
|
Psychrobacter
|
|
|
G- rods; facultative anaerobic; mesophilic
|
Salmonella
|
|
|
G- rods; can contribute to spoilage of refrigerated vegetables and meats
|
Serratia
|
|
|
G- straight or curved rods; associated with aquatic or marine environments
|
Shewanella
|
|
|
G- rods; facultative anaerobic; mesophilic
|
Shigella
|
|
|
G+ cocci; salt tolerant; mesophilic
|
Staphylococcus
|
|
|
Gr+ rods; anaerobic; sporeformer; related to Clostridium; can cause problems in canning
|
Thermoanaerobacterium
|
|
|
G+ cocci; composed of former group N lactococci; can grow at 10C but not at 45C
|
Vagococcus
|
|
|
G- straight or curved rods; requires low levels of salt; common in marine environments
|
Vibrio
|
|
|
G- rods; closely related to Leuconostoc; species were former Leuconostoc species; heterofermentative
|
Weissella
|
|
|
G- rods; facultative anaerobic; mesophilic
|
Yersinia
|
|
|
Common in dairy products; 1 species can grow in 24% salt and at an Aw as low as 0.65; forms slime on wieners; grows in brine and on cheeses; spoils orange juice concentrate and yogurt
|
Debaryomyces
|
|
|
Yeast found on figs, tomatoes, strawberries, citrus fruits, and cacao beans
|
Hanseniaspora
|
|
|
Yeast common on a variety of foods
|
Issatchenkia
|
|
|
Yeast common in dairy products; can spoil fruits and dairy product
|
Kluyveromyces
|
|
|
Large genus; can spoil pickles and sauerkraut; common on fresh fish and shrimp; important in making some indigenous foods in parts of the world
|
Pichia
|
|
|
bakers’, brewers’, wine and champagne yeasts; also found in kefir grains and wide variety of foods
|
Saccharomyces - S. cerevisiae
|
|
|
Yeast... some are osmophilic and resistant to some chemical
preservatives |
Schizosaccharomyces
|
|
|
Strong fermenters of sugars; Z. rouxii can grow at aw of 0.62; One can grow at pH 1.8; Some involved in miso and shoyu fermentations; some spoil mayonnaise and salad dressing
|
Zygosaccharomyces
|
|
|
Common yeast, can grow at pH 1.8; can spoil beer, wine, soft drinks, and pickles
|
Brettanomyces - B. intermedius
|
|
|
Yeast common in ground beef and poultry and a variety of foods; some
may play a role in fermentation of cacao beans and other products |
Candida
|
|
|
Yeast found on plants, soil, fruits, fish, shrimp, fresh ground beef
|
Cryptococcus
|
|
|
Produce pink/red pigments; some are psychrotrophic; found on
butter, fresh poultry, shrimp, fish, and beef |
Rhodotorula
|
|
|
Involved in cacao bean fermentation; found on fresh shrimp, ground beef, poultry, frozen lamb, and other foods
|
Trichosporon
|
|
|
5 important protozoa in the US
|
1. Cryptosporidium parvum
2. Cyclospora cayetanensis 3. Entamoeba histolytica 4. Giardia lamblia 5. Toxoplasma gondii |
|
|
conditions referred to as “whiskers” of beef or “black spot” on frozen mutton; other species found on a variety of foods
|
Mucor
|
|
|
“bread mold”; produces watery, soft rot on variety of fruits; “black
spot” on beef and frozen mutton; found on bacon and refrigerated meats; one species important in fermentation of tempeh, oncom, and bonkrek |
Rhizopus
|
|
|
1 species; found on refrigerated beef; “whiskers” on beef
|
Thamnidium
|
|
|
Produces heat resistant ascospores; can tolerate low oxidation-reduction potential
|
Byssochlamys
|
|
|
cause brown to black rots of some Fruits and stem-end rot and black rot of citrus fruits; field fungi that can grow on wheat; has been found on red meats; some species can produce mycotoxins
|
Alternaria
|
|
|
black rot of some fruit; some species can spoil oils (e.g., palm,
corn, peanut); some species important in soy fermentation; 2 species produce mycotoxins |
Aspergillus
|
|
|
Found on shrimp; “black spot” of long-term stored beef; common on vegetables and fruits
|
Aureobasidium
|
|
|
Gray mold rot on fruits
|
Botrytis
|
|
|
“black spot” on beef and frozen mutton; some spoil butter and margarine; some rot fruits; field fungi that grow on barley and wheat
|
Cladosporium
|
|
|
Brown rot of citrus fruits and pineapples and soft rot of figs; field
fungi on barley and wheat; some species can produce mycotoxins |
Fusarium
|
|
|
“machinery mold”; especially a problem in tomato processing plants; can spoil some fruits and some dairy products; common on a variety of fruits and vegetables
|
Geotrichum
|
|
|
Brown rot of some fruits
|
Monilia
|
|
|
Blue and green mold rots of fruits; P. roqueforti produces blue cheese; some species can produce mycotoxins
|
Penicillium
|
|
|
1 species; pink rot of fruits; common on variety of grains; some can produce mycotoxins
|
Trichothecium
|
|
|
Can grow at Aw of 0.69
|
Wallemia
|
|
|
Minimum growth Aw is 0.61; maximum Aw is <0.97; is somewhat
heat resistance; spoils licorice, prunes, chocolate syrup |
Xeromyces
|
|
|
What is the F0?
|
The number of minutes required to destroy a specific number of spores at 121.1C (250F) when z is 10C (18F)
It varies for substrate and microorganism |
|
|
What must be used for controlling microorganisms with temperature?
|
Proper sanitation
Proper pH Proper time/temperature relationship Proper sealing Proper container integrity |
|
|
What is the water activity (Aw)?
|
Water needed for microbial growth
P/P0 Vapor pressure of food / Vapor pressure of pure water at same temp. |
|
|
What occurs at low water activity?
|
If low enough, lag phase lasts indefinitely and growth stops
microbes are also more resistant to heat effects |
|
|
What is a Xerophile?
|
Grows at Aw < 0.85
|
|
|
What company plead guilty to salmonella charges?
|
Cadbury
|
|
|
How do you use O-R potential to inhibit aerobic microorganisms?
|
Use facultative microorganisms
|
|
|
What can act as a selective agent for microorganisms in foods?
|
Ox-red potential
|
|
|
How is ethylene oxide used?
|
Can penetrate most organic material.
Used in whole or ground spices except those containing salt. |
|
|
How is ozone used?
|
Unstable, powerful oxidizing agent
Used in water treatment and bottle sterilization |
|
|
What is propylene oxide used in?
|
Dried foods, cocoa, gums, etc
|
|
|
What is altering the atmosphere good for?
|
Large masses of food, esp if heated
|
|
|
What type are most foodborne pathogens?
|
Facultative anerobes or anerobic
|
|
|
What pH range do most bacteria prefer?
|
6.5-7.4
|
|
|
What pH type do most molds and yeast grow in?
|
Acidic
Main cause of spoilage is these foods |
|
|
Most meats are at what pH?
|
5.6 and above
|
|
|
Most vegetables are higher or lower in pH than fruits?
|
Higher
So more susceptible to bacteria than mold |
|
|
Buffering is used more in what?
|
Meats
|
|
|
What does pH have an effect on?
|
Enzyme function
Cell transport of nutrients Younger more than older/resting cells Temperature and salt concentration Lag phase outside optimum range |
|
|
What are the requirements for used of chemical preservatives?
|
Economical
Only if other methods inadequate or unavailable Extend storage life Does not lower food quality Readily soluble Antimicrobial properties over the food's pH range Safe at needed levels Readily identified by chemical analysts Does not retard digestive enyzmes Does not yield more toxic compounds Easily controlled and uniformly distributed in food Wide antimicrobial spectrum |
|
|
Where are organic acids and esters found?
|
Fruits (citric, sorbic, benzoic, etc)
Meats (lactic) Metabolic products of m/o (fermented foods) |
|
|
How do organic acids and esters work?
|
Undissociated form passes through cell membrane then ionizes inside cell interfering with permeability of cell membrane
|
|
|
Shorter chain organic acids and esters inhibit what?
|
Both gram - and +, passing through cell membrane easily
|
|
|
Long chain organic acids inhibit what?
|
Primarily gram positive
Difficult to pass through gram negative |
|
|
What bonus is associated with organic acids and esters?
|
Can potentiate antimicrobial effect of nitrite and sufite
|
|
|
What pH do organic acids and esters form?
|
At lower pH generally < 5,5
|
|
|
What are some problems with organic acids and esters?
|
Less effective if initial cell # is high
Some m/o can use as energy source Resistance varies in strains |
|
|
What are strong acids widely used in?
|
Just carbonated beverages
|
|
|
What is acetic acid good for?
|
It is effective and widely used
|
|
|
What is benzoic acid good for?
|
Antimycotic activity
|
|
|
What is citric acid good for?
|
It has moderate antimicrobial activity
|
|
|
What are p-hydroxy benzoic acids (parabens) good for?
|
Effective over a wider pH range
|
|
|
What is propionic acid good for?
|
A mold inhibitor that is ineffective on yeast
great for baking |
|
|
What is sorbic acid good for?
|
Effective against catalase positive bacteria, yeasts and molds
(good for fermentations) And good against germinating endospores, preventing outgrowth |
|
|
How is NaCl used?
|
Primarily decreases Aw
Used for creating selective environment for lactic acid bacteria Inhibit botulinum |
|
|
What is sulfur dioxide used for?
|
Soft drinks, juices, wines, sausages, pickles
Levels controlled due to hypersensitivity problems |
|
|
What are the types of curing salts?
|
NaCl, NaNO3, NaNO2, KNO3, KNO2
|
|
|
How does nitrite work?
|
Prevents outgrowth of spores
|
|
|
What is the issue with antimicrobial plant substances like eugenol, cinnamic aldehyde, and caffeine?
|
The are weak and using just one results in off-flavor issues.
|
|
|
What is lactoperoxidase?
|
Antimicrobial in milk against sensitive gram negatives
|
|
|
What is Nisin?
|
Heat stable protein (121C) produced by Lactococcus lactis that is inhibitory toward many gram positives by adsorption to the cell membrane and pore formation (inactivation of sulfhydral groups) causing disruption of proton motive force. Used in processed cheeses.
|
|
|
What is the primary action of antimicrobials?
|
To slow growth
|
|
|
How are antibiotics used in food?
|
Not added to food directly but in animal production as a feed supplement and as sub theraputic treatment
|
|
|
What types of ionizing radiation are useful? How?
|
Gamma, x-rays, electron beams
Directly damages genetic material or indirectly through free radicals or peroxide formation |
|
|
What types of ionizing radiation are not useful and why?
|
Alpha particles (poor penetration)
Neutrons (induce radioactivity) |
