Lesson 8 ·Class 9 · Economic Importance of Bacteria and Fungi · Sort Lab
Spoilage and Preservation
Every method attacks one of the microbe's needs.
Microbes need moisture, warmth and a hospitable chemical environment. Sort each method by what it takes away.
Sorted 0/10
All items sorted — check each bin.
Free play — sort every item into the bin it belongs in; each correct drop tells you why. Switch to when you're ready to test yourself.
Salting and sugaring both work by osmosis, so both belong with the chemical methods, not the drying ones.
What this lesson covers
What you do
- Which methods actually KILL the microbes, and which merely stop them growing? It matters when the food is thawed.
Challenges to clear
- Fill the hostile-conditions bin correctly.
- Sort every method.
- Fill the 'Removes water' box — the oldest trick for keeping food safe.
The task
Microbes need moisture, warmth and a hospitable chemical environment. Sort each method by what it takes away.
What this lesson covers
- Removes water: Sun-drying fish, chillies or grain (Without moisture, bacteria and fungi cannot grow or reproduce.); Making milk powder (Dehydration turns a highly perishable food into a stable one.)
- Removes warmth: Refrigeration (Cold does not kill microbes; it slows their enzymes so they multiply very slowly.); Deep freezing (Growth is halted almost entirely, but the microbes revive on thawing.)
- Kills by heat: Pasteurising milk (Heating then rapid cooling kills pathogens without spoiling the taste.); Canning and bottling (Food is heated and then sealed, so nothing can re-enter.)
- Makes conditions hostile: Salting meat and fish (Salt draws water out of microbial cells by osmosis, killing them.); Making jam with a great deal of sugar (Concentrated sugar works by osmosis, just as salt does.); Pickling in vinegar or oil (Acid or an oil seal makes the environment unlivable.); Adding sodium benzoate (A chemical preservative that inhibits microbial growth directly.)
Hint
Salting and sugaring both work by osmosis, so both belong with the chemical methods, not the drying ones.