Project ForgeThe growth of bacteria (lactobacillus) in milk leads to curd formation. A minimum bacterial population density of 0.8 (in suitable units) is needed to form curd. The population density of lactobacillus in 1 litre of milk is plotted as a function of time, at two different temperatures, 25C and 37C: at 37C, density crosses 0.8 around t=80 min and plateaus near 1.0 by about t=140-160 min; at 25C, density crosses 0.8 around t=120-130 min and plateaus near 1.0 by about t=180-200 min.
Consider the following statements based on this data: i. The growth in bacterial population stops earlier at 37C as compared to 25C ii. The time taken for curd formation at 25C is twice the time taken at 37C
Which one of the following options is correct?
- Only i
- BOnly ii
- CBoth i and ii
- DNeither i nor ii
Explanation
The 37C curve plateaus (growth stops) around t=140-160 min, noticeably earlier than the 25C curve's plateau around t=180-200 min, so statement (i) is TRUE. Curd forms when density reaches 0.8: at 37C this happens around t=80 min, and at 25C around t=120-130 min — that's roughly 1.5x, not exactly double, so statement (ii) is FALSE. Only (i) is correct.
Source: GATE ME 2017 Session 1 (ME-1) (2017)
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