FMLec | M5: High-temperature food preservation method

• _ is a traditional fpm involving use of any and all temperature above ambient ( > 10-15C)

• Application in preservation is based on destructive effects of heat on microorganism

• 2 common methods: pasteurization (reduce microbes to safe levels), sterilization (complete elimination)

High-temperature fpm

Enumerate 2 most common methods of high-temp food preservation

• Pasteurization

• Sterilization

Enumerate 7 factors affecting microbial heat resistance

wfsp nit

• Water

• Fats, carbohydrates, proteins

• Salts

• pH

• Number & age of organism

• Inhibitory compounds

• Time & temperature

T/F: In general, increase in water activity leads to decreased heat resistance

TRUE

Bc presence of water allows it to conduct heat

T/F: Temperature and time are inversely correlated to killing effect of heat

FALSE

Temperature and time are directly correlated to killing effect of heat

Relative heat resistance of microorganisms is related to _, e.g., yeast & molds are sensitive to heat (grow best ambient temperature); psychrophiles vs. mesophiles vs. thermophiles

optimal growth temperatures

Explain how water affects microbial heat resistance

• Presence of water allows faster protein denaturation

• Dried vs. Moist cells; dried more resistant because water are absorptive of heat & thus moist feel its effects more

• Increased heat resistance lhwm

  • Low humidity

  • Low water activity

  • Low moisture

Explain how fats, carbohydrates, & proteins affects microbial heat resistance

• Fats generally increase heat resistance of some microorganisms, e.g., long-chain FAs > short-chain FAs

• Carbohydrates increase heat resistance partly due to decrease in water activity

• Proteins increase heat resistance bc they have protective effects on microorganisms

Explain how salts affects microbial heat resistance

• Some salts (Ca²⁺) decrease water activity and thus have protective effect on microbes by increasing heat resistance

• Some salts, however, phosphates increase water activity and thus tend to make some microbes heat-sensitive

Explain how pH affects microbial heat resistance

• Microorganisms have higher heat resistance at their optimum pH (point of comparison is the same microbe)

• Thus, less heat is applied to sterilize acidic food (bc they’re already at a non-optimal pH; lower heat tolerance)

Explain how number & age of organism affects microbial heat resistance

• Number

  • High cell density > low cell density since they would produce also more heat-protective substances compared to low cell

• Age

  • Old cells (stationary) vs. Actively growing cells (log)

    • Stress response activation

    • Higher Aw on actively growing cells; lower heat resistance

  • Lag phase vs. log phase cells

    • Stress response activation

    • Higher Aw on actively growing cells; lower heat resistance

  • Old bacterial spores vs. Young bacterial spores

    • More endospores formed in older culture > younger culture

    • More mature protective layers and relatively lower water content

Explain how inhibitory compounds affects microbial heat resistance

• Decreased heat resistance because the cells are not in their optimal condition and are affected by stress, thus less effective at resisting heat

Explain how time & temperature affects microbial heat resistance

• Time & temperature are both directly correlated to killing effect of heat

  • Higher temp > more effective killing by heat

  • Longer time > more effective killing by heat

• Relative heat resistance of microorganisms are related to their optimal growth temperatures

  • e.g., Yeasts & molds are sensitive to heat bc they grow optimally at ambient temp

  • Psychrophiles (most sensitive) vs. Mesophiles (most resistance) vs. Thermophiles

Enumerate and explain 6 thermal destruction parameters of microorganisms

tt dzf 12d

• Thermal death time

  • Time needed to kill a given no. of microorganisms at a specified temperature

• Thermal death point

  • Temperature needed to kill a given no. of microorganisms at a fixed time (usually 10 mins)

• D value

  • Time needed to destroy 90% of organisms

• Z value

  • Temperature needed to

    • increase death rate by 10-fold

    • decrease D value by 10-fold

  • Kill more in shorter amount of time

• F value

  • Time at a given temperature needed to destroy spores or vegetative cells of a particular organism

• 12-D concept

  • Food safety standard that uses heat to reduce no. of C. botulinum spores in canned food by 10¹² times, ensuring almost complete sterility

  • D = D value, time needed to kill 90% of spores

  • 12 of those steps = 99.9999999999% killed

  • Goal = u want a 12 log reduction of C. bot spores

• _ is the time needed to kill a given no. of microorganisms at a specified temperature

• Changing of either of 2 factors will change time

  • Decontam 121 C by 15 mins

  • If temp increased to 140, time would be shorter

Thermal death time

• _ is the temperature needed to kill given no. of microorganisms at fixed time (usually 10 mins)

• e.g., 100 C for 10³ cells 10 mins exposure

• Increasing no. of cells = increase temp

Thermal death point

• _ is the time needed to destroy 90% of microorganisms

• In figure shown, what is the time needed to destroy organisms by 90%?

• If temp is increased from 50 → 60, time = ?

• 70?

• D value (decimal reduction time)

• 40 mins

• 12 mins

• 4 mins

_ is time needed for survivor curve to traverse 1 log cycle

D value (decimal reduction time)

100 → 10 = 1 log cycle

10 → 1 = 1 log cycle

1 → 0.1 = 1 log cycle

• _ is the temperature needed to increase death rate by 10-fold, decrease D value by 10-fold

  • D value in log (y) vs. Temp (x)

  • At 220 F, D value = 113 mins (time needed to kill 90% microbes)

  • At 237.5 F, D value = 11.3 mins

• Allows for calculation of equivalent heat processes at diff temps

z Value

_ is the difference between temperature of 2 D values

z values

• Determine z Value of the graph shown (z value at 10-fold)

• How about from 10 → 1 ?

• 100 → 220 F = 113 mins (D)

• 10 → 237.5 F = 11.3 mins (D)

• 237.5 F - 220 F = 17.5 F = z value

• 10 → 1

  • 10 = 237. 5 F

  • 1 = 257 F

  • z = 19.5

_ is the time at given temp needed to kill spores or vegetative cells of particular organism

F value

• _ is a process lethality requirement

• Minimum heat process should reduce probability of survival of most resistant C. botulinum endospores to 10^-12

• Applied in canning industry (food > pH 4.6)

  • C. botulinum endospores do not germinate & produce toxins below pH 4.6

12-D concept

• _ is a traditional fpm that lowers moisture content to a point where activities of foodborne microorganisms are inhibited

• Endospores, bacteria, many fungi survive this

• Effects on spoilage

  • Aw = 0.80 and 0.85 → Fungal spoilage in 1–2 weeks

  • Aw = 0.75 → Delay > 2 weeks

  • Aw = 0.65 → ~2 years delay; Very few spoilage organisms

Drying

Enumerate 4 novel techniques in food preservation

phpp

• Pulsed Electric Fields

• High-Pressure Processing

• Pulsed Light Technology

• Plasma Technology

Novel technique

• Nonthermal method of microbial inactivation

• Short time high-intensity sthi electric pulses between two electrodes placed in a food

• Damages the cell membrane

Pulsed electric fields pef

• Also known as high hydrostatic pressure (HHP)

• Nonthermal method of microbial inactivation

• Short duration pressurization sdp of a packaged food in a water-filled, closed chamber

• Changes in microbial protein structures and other macromolecules

High-pressure processing

• Nonthermal method of microbial inactivation

• Short duration high-energy sdhe light pulses (170–2600 nm)

• Acts on nucleic acids, proteins, membranes, and other cellular components

Pulsed light technology

• Low-temperature plasma – Gas mixture of nitrogen, oxygen, and carbon dioxide

• Highly toxic free-radicals and ionic species fris

Plasma technology

T/F: Novel techniques in food preservation are generally better for preserving heat-sensitive food

TRUE

• Fundamental principles, procedures, means priprome needed to design environment suitable for quality food production

• Developed by governments, Committee on Food Hygiene (e.g. WHO), and the food industry

Good Manufacturing Practice (GMP) / Current Good Manufacturing Practice (bc they change over time, is updated over time)

_ is a key factor for industries to produce good quality, safe, affordable products

cGMP

Give 3 examples of general GMP guidelines

ats

1. There should be an adequate number of personnel, as determined by the company, at all levels with knowledge, skills, and capabilities relevant to their assigned functions, in good mental & physical health to be able to execute their duties

2. All employees directly engaged in manufacturing activities shall be trained in the particular operations they perform in accordance with the principles of GMP

3. Plants, buildings, & structures shall be of suitable size, design, & construction to facilitate maintenance & sanitary operations for food manufacturing purposes

   1. Individual working areas shall be adequate so that any risk of confusion & cross-contamination that will affect the safety of the food manufactured will be avoided

*GMP varies across countries

• A tool to assess hazards and establish control systems

• To ensure food safety

Hazard Analysis Critical Control Point (HACCP)

Enumerate 7 HACCP principles

h4c vr

1. Hazard analysis

2. Critical control points (CCPs)

3. Critical limits

4. CCP monitoring

5. Corrective actions

6. Verification

7. Record keeping

HACCP principle

• Preparing a list of steps in the process where significant

  hazards occur

• Describing the preventative measures

• Which hazards can be eliminated or reduced to acceptable levels?

Hazard analysis (HA)

HACCP principle

• Essential for the elimination or acceptable reduction of

  the hazards

• Must be a quantifiable procedure

• Identified using decision trees

Critical control points

HACCP principle

• Describe the difference between safe and unsafe

  products at the CCP

• A quantifiable PARAMETER

• e.g. temperature, time, pH, moisture, aw, salt

  concentration, titratable acidity, available chlorine ttpma sta

Critical limits

HACCP principle

• Establishing mpam

  • Monitoring requirements

  • Procedures to adjust the process

  • Procedures to maintain control

CCP Monitoring

HACCP principle

• To be taken when monitoring indicates a deviation from

  an established Critical Limit

• Must be developed for each CCP

Corrective actions

HACCP principle

• Establish procedures for verification that the HACCP

  system is working correctly

• Conducted routinely or on an unannounced basis

Verification

HACCP principle

• Establish effective record‐keeping procedures that document the HACCP System

• To demonstrate sa

  • Safe product manufacture

  • Appropriate action has been taken for any deviations from the Critical Limits

Record Keeping

_ is the effort to protect food from acts of intentional adulteration, tampering, or contamination atc

Food defense

Explain deliberate food alterations & their consequences

• Food alterations pibf

  • Production or distribution points

  • Individual food items or bulk foods

  • Biocrime – Disgruntled individual/employee

  • Food terrorism – Terrorist groups

• Consequences pepl

  • Public health burden

  • Economic loss

  • Public fear

  • Loss of confidence in political and regulatory authorities

_ are same pathogens that cause outbreaks of foodborne illness due to accidental contamination

Biocrime organisms

Give 3 examples of biocrime cases

• Stepwise analysis of hazards that may be associated with a particular type of food product

• Estimates the probability of adverse effects on health from consuming the product in question

Microbiological risk assessment (MRA)

• _ is a function of the (L) probability of an adverse health effect and the (C) severity of that effect

• f (L,C)

• Higher likelihood + higher consequence → greater risk

• Consequence has more weight relative to likelihood

  • e.g., low likelihood + high consequence → not necessarily low

Risk

Describe general framework of MRA