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Food Science and Technology QUESTION #5991
Question 1
In dairy microbiology, 'psychrotolerant' bacteria differ from 'psychrophilic' bacteria in that:
  • Psychrotolerant bacteria cannot grow above \(20^{\circ}\text{C}\); psychrophilic bacteria grow optimally at \(20^{\circ}\text{C}\)
  • Psychrotolerant bacteria have optimal growth above \(20^{\circ}\text{C}\) but can grow slowly at refrigeration temperatures (\(0\text{–}7^{\circ}\text{C}\)); psychrophilic bacteria have optimal growth below \(15^{\circ}\text{C}\)✔️
  • Psychrotolerant bacteria are heat resistant; psychrophilic bacteria are not
  • They are identical terms used interchangeably in dairy science
Correct Answer Explanation
True psychrophiles have optimal growth \(<15^{\circ}\text{C}\) and cannot grow above \(20^{\circ}\text{C}\). Psychrotolerant (psychrotrophs) bacteria grow optimally at \(20\text{–}30^{\circ}\text{C}\) but can also grow at refrigeration temperatures (\(0\text{–}7^{\circ}\text{C}\)), though slowly. Major dairy spoilage organisms (\(Pseudomonas\;fluorescens\)) are psychrotolerant.