Food Microbiology: Preservation, Safety, and Detection Techniques

Food Preservation

Prevents spoilage, contamination, and deterioration; extends shelf life and maintains quality; ensures safety by controlling or destroying harmful microbes.

Major Causes of Food Spoilage

Microorganisms (Bacteria, yeasts, molds), Enzymes.

Examples of Microorganisms causing Spoilage

Salmonella, Listeria monocytogenes, Clostridium botulinum.

Goal of Preservation

Destroy or inhibit microorganisms.

Thermal Preservation Methods

Heat destroys microorganisms and enzymes.

Pasteurization

60-85°C for seconds/minutes; example: Milk = 72°C for 15 seconds; destroys pathogens while preserving flavor.

Sterilization / Canning

≥121°C for 15 minutes (commercial sterility); prevents C. botulinum growth in canned foods.

Blanching

90-100°C for 1-5 minutes; inactivates enzymes; maintains color/flavor; common before freezing vegetables.

Advantages of Thermal Methods

Very effective, simple.

Limitations of Thermal Methods

Loss of heat-sensitive nutrients and sensory qualities.

Non-Thermal Preservation Methods

Preserve nutrients, flavor, texture; minimal processing.

High Pressure Processing (HPP)

Uses 100-600 MPa; disrupts microbial cells; maintains freshness; used in juices, guacamole, meats.

Pulsed Electric Field (PEF)

Electric pulses disrupt cell membranes.

UV-C Treatment

Damages microbial DNA.

Cold Plasma

Reactive ions destroy microbes on surfaces.

Irradiation

Uses gamma rays, X-rays, or electron beams; kills insects, parasites, pathogens; used for spices, dried herbs, meats.

Advantages of Non-Thermal Methods

Retains nutrients and quality.

Limitations of Non-Thermal Methods

Expensive equipment.

Types of Chemical Preservatives

Organic acids, Nitrites, Sulfites, Antioxidants.

Organic Acids

Benzoic acid, Sorbic acid; inhibit yeasts/molds.

Nitrites

Prevent C. botulinum in cured meats.

Sulfites

Prevent browning and microbial spoilage.

Antioxidants

BHA, BHT, Vitamin E; reduce oxidation.

Natural Preservatives

Salt, sugar, vinegar, essential oils; clean-label trend (fewer synthetic additives).

Advantages of Chemical Preservation

Easy to use, cost-effective.

Limitations of Chemical Preservation

Consumer concerns about additives.

HACCP

A preventive, systematic program to control biological, chemical, and physical hazards in food production.

Food Safety Purpose

Prevent hazards before they occur, ensure finished product is safe, used widely in processing plants and food service.

FDA

Food and Drug Administration; oversees most domestic & imported foods (non-meat/poultry), regulates labeling, additives, manufacturing.

Key Laws of FDA

FDCA (Food, Drug & Cosmetic Act), FSMA (Food Safety Modernization Act).

USDA

United States Department of Agriculture; regulates meat, poultry, egg products, enforces Federal Meat Inspection Act & Poultry Products Inspection Act.

CDC

Centers for Disease Control and Prevention; not regulatory, tracks foodborne illness outbreaks, provides prevention guidelines.

APHIS

Animal and Plant Health Inspection Service; protects U.S. agriculture from pests/diseases, monitors animal & plant imports and health risks.

Codex Alimentarius Commission

International body (FAO & WHO) that develops global food safety standards for consumer protection and fair trade.

Foodborne Illness Outbreaks

Caused by contaminated food with pathogens, toxins, or chemicals; examples include Salmonella, Listeria, E. coli.

Antimicrobial Resistance (AMR)

Microorganisms become resistant to antimicrobial drugs; antibiotics no longer effective.

Why AMR Matters

Major global threat; resistant bacteria spread through contaminated food, leading to severe infections, higher treatment costs, longer hospital stays, higher mortality.

Causes of AMR

Overuse/misuse of antibiotics in humans and animals, environmental contamination: soil, water, manure, poor hygiene in food processing & handling.

One Health Concept

Humans, animals, plants, environment are interconnected; AMR spreads through soil, water, crops, food, humans.

Prevention Strategies for AMR

Good Agricultural Practices (GAPs), responsible antibiotic use, strong sanitation & hygiene (farm → processing → retail → home).

Molecular Detection Technologies Purpose

Improve accuracy, speed, and sensitivity for detecting pathogens.

PCR

Polymerase Chain Reaction; detects DNA of pathogens, rapid and specific.

Whole Genome Sequencing (WGS)

Analyzes entire genome; tracks outbreaks, virulence, resistance genes.

Metagenomics

Studies all DNA in a sample; identifies non-culturable microbes, detects complete resistome.

Key Preservation Trends

Minimal processing, natural preservatives, consumer preference for 'clean-label' foods, using multiple preservation hurdles for safety + quality.