Question

Alpha naphthol and KOH is used for ……

(a) Voges-Proskauer test (b) Indole test (c) Citrate test (d) Methyl red test​

Answer 1

indole test or citrate test

Answer 2

OPTION (a) IS CORRECT.

(a) VOGES-PROSKAUER TEST

Explanation:

• To detect the ACETOIN in bacterial broth culture the voges-proskauer test is used.
• In this test, the reagents used are alpha naphthol (5%), and potassium hydroxide (40%).
• To the broth alpha naphthol and KOH are added and the colour change to cherry red indicates the presence of acetoin.
• A yellow-brown colour indicated negative test.
• Therefore, option (a) is correct.