Contamination VS Spoilage

Contamination is the presence of unwanted materials, chemicals and microorganism which can cause illness to the consumer. 

Cross contamination occurs when microorganism from a contaminated surface are transferred to another surface that is not contaminated. This happens in salads and meat. Meat section should be separated from vegetable section especially when the vegetables are served raw. Cross contamination may come from different sources:

Surface of well washed tomato may
show 700mcgs/cm while unwashed
 tomato would have several thousands

• From green plants and fruits
  Ex. surface of well washed tomato may show 400-700 mcgs/cm, while unwashed tomato would have several thousands. 
• From animals
  - include surface flora, flora of respiration tract and gastrointestinal tract.
• From sewage.
   untreated domestic sewage used to fertilize plant crops may contaminate food with human pathogens
• From soil
  -contains greatest variety of microorganisms of any source of contamination|
  -good source of heat resistant spore forming bacteria. 
• From water
  -main interests; public health aspects and economic aspects.
  -chlorination: 0.025 to 2 parts of available chlorine per million parts of water (residual)
• From air
  - does not contain natural flora of microorganisms
  - microorganisms usually suspended on solid materials or in moisture droplets, mostly molds.
  -number of microorganisms increased by the air current and decreased by direct sunlight and rain.  
• During processing and handling
  -food contacts with the equipment packaging materials and personnel. 

Spoilage is the decay, decomposition or any change in food product that makes it unacceptable to consumer. 

Causes of Spoilage

1. Growth and activity of microorganism
2. Actions of enzymes of plant or animal food.
3. Purely chemical reactions
4. Insects (ex. fly)
5. Physical changes (ex. caused by freezing, burning, drying, pressure, etc.)

Food Classification by Ease of Spoilage

1. Stable or non-perishable foods
   -foods that do not spoil unless handled carelessly
   ex. sugar, flour
2. Semi perishable foods
   -If properly handled and stored, remain unspoiled for a fairly long period.
   ex. potatoes, nuts
3. Perishable foods
   -includes daily foods that spoil readily unless special preservation methods are used
   ex. meat, fish, poultry and vegetables, eggs and milk. 

Factors affecting kinds and numbers of microorganism in food

1. Contamination
   - increased number of microorganism and may even introduced to new kinds (from wash water, plant equipment, transportation, etc) makes preservation more difficult. 
2. Growth of Microorganism
   -brings about the greatest increase in bioburdencausing spoilage. 
3. Pre-treatments
   -may remove or destroy some kinds of microorganisms, add organisms, or change the proportions of those present or inactivate part or all of the food enzymes.

Factors Affecting the Growth of Microorganisms

1. Associative growth
2. Effects of environmental condition
3. Physical state and structure of food.
4. Chemical properties of food
5. Temperature.

What are the factors that affects microbial growth?

Intrinsic parameters

• Nutrient content
  -water
  -energy source -CHO esp. sugars, AA, esters, organic acids
  -Nitrogen Source -for growth-
  -Vitamins and other related growth factors
  -Minerals
• Anti- microbial constituents
  -may naturally occurring substances, are purposely or accidentally added or are developed by microorganism or by processing
  -affect microorganism by:
    >acting on the whole cell
    >acting on the CW or membranes
    >interfering with genetic mechanisms
    >interfering with enzyme systems
    >binding essential nutrients
  
  -examples of naturally occurring inhibitors: lacteninsand anticoliform factor in freshly drawn milk, lysozyme in egg whites and benzoic acid in berries.
   
• Biological structures
  -inner whole, healthy tissues of living plants and animals are sterile or low in microbial content
  -the natural covering of some foods provides excellent protection of vs. the entry of subsequent damage by spoilage organism 

Note: The importance of these parameters are:

1. Predict general types of organisms that are more likely to grow.
2. Predict overall stability of a particular food
3. May Aid in determining the age and possible history of a given food

Extrinsic parameters

• Temperature of Storage - temperatures will support growth are limited to those at which water is liquid.
• Relative Humidity - activity (AW) contributes to the growth of microorganisms in the surface. 
• Presence and Concentration of gasses.
  -Increasing CO2 and/ or reducing O2, the rate of respiration of fresh foods is reduced thus increasing the shelf life. 
• Presence and Activity of Other Microorganism
  -growth rate bacteria>yeast>molds

Seven Highly Effective Habits for Home Food Safety



Habit 1: Hot Or Cold Is How to Hold

Habit 2: Don't Be A Dope, Wash With Soap

Habit 3: Watch That Plate, Don't Cross-Contaminate

Habit 4: Make It A Law - Use The Fridge To Thaw

Habit 5: More Than Two Is Bad For You

Habit 6: Don't Get Sick, Cool It Quick

 Habit 7: Cook It Right Before You Take A Bite