Which of the following is NOT correctly matched ?

Question

UnlockIAS · Accepted Answer

Correct — D, 'Pasteurisation — Tea'. The stem asks which pair is NOT correctly matched, and this is the mismatch. Pasteurisation is the mild, controlled heat treatment devised by Louis Pasteur in the 1860s that kills pathogenic and spoilage micro-organisms in a liquid without cooking it — it is applied above all to milk, and also to fruit juice, beer and wine. Tea is not pasteurised at any stage: tea manufacture runs through withering, rolling, oxidation (trade term 'fermentation') and drying, and the beverage is then made by infusing the leaf in near-boiling water, which is not a pasteurisation process. The other three pairs are all correctly matched, so (d) is the answer.

Why the other options are wrong — (a) Correctly matched, so not the answer. Desalination is precisely the removal of dissolved salts from sea water or brackish water to yield fresh water, whether by distillation (multi-stage flash, multi-effect, low-temperature thermal) or by membranes.  (b) Correctly matched, so not the answer. In reverse osmosis an external pressure greater than the osmotic pressure is applied on the saline side, forcing water through a semi-permeable membrane and leaving dissolved salts behind. It is the standard technology of household water purifiers and of modern desalination plants, and its product is potable water.  (c) Correctly matched, so not the answer. Denaturation is the loss of a protein's native three-dimensional shape (secondary, tertiary and quaternary structure) under heat, acid, alcohol, urea or heavy metals, while the peptide bonds of the primary structure survive. A boiling egg white setting and milk curdling are everyday denaturation.

Concept: Four distinct processes, each with one substance it genuinely acts on. Desalination removes dissolved salt from sea or brackish water to produce fresh water. Reverse osmosis is a pressure-driven membrane separation that pushes solvent the 'wrong' way across a semi-permeable membrane — the workhorse of drinking-water purification and one route to desalination. Denaturation is the disruption of a protein's folded structure without breaking its peptide backbone, which is why a denatured enzyme loses its activity. Pasteurisation is the controlled mild heating of a perishable liquid — classically milk — to destroy pathogens and extend shelf life, run either as LTLT (about 63 °C for 30 minutes) or HTST (about 72 °C for roughly 15 seconds). Match process to substance and the odd pair falls out.

State PCS 2019 Q25 — Science & Technology PYQ with Answer

State PCS 2019 Q25 — Science & Technology PYQ with Answer