Foods can be preserved in many ways by slowing or preventing bacterial growth. which of these methods should be least effective at inhibiting bacterial growth?
a) refrigeration: slows bacterial metabolism and growth.
b) closing previously opened containers: prevents more bacteria from entering, and excludes o₂.
c) pickling: creates a ph at which most bacterial enzymes cannot function.
d) canning in heavy sugar syrup: creates osmotic conditions that remove water from most bacterial cells.
e) irradiation: kills bacteria by mutating their dna to such an extent that their dna-repair enzymes are overwhelmed.

B) Closing previously opened containers: prevents more bacteria from entering, and excludes O₂.

Explanation:

The bacteria are small prokaryotic single celled organisms which are abundantly available on air, water and soil. They live in water, air, soil, inside and outside the body of other organisms in symbiotic or parasitic association. These bacteria particularly invades the food items. The refrigeration, pickling, canning in heavy sugar syrup and irradiation with the radiation all can help in inhibiting the growth of the bacteria.

But closing the cans is the least effective approach as the food is already subjected to the bacterial infection which can contaminate the entire food.