Chapter 16, Problem 1Q

When canned foods spoil, what causes the blackening of the cans?

Summary Introduction

To determine:

The reason for blackening of food can when the food inside it gets spoiled.

Introduction:

The test used to determine the microbe's ability to convert sulfur-containing compounds into sulfides is termed as hydrogen sulfide test. Certain bacteria contain de-sulfhydrase enzyme that removes hydrogen sulfide from the amino acids that contain sulfur, such as cysteine.

Explanation of Solution

Unfavorable environmental conditions such as excessive heat can cause the spoilage of food due to the development of bacteria in the food can. Certain bacteria contain desulfhydrase enzymes that catalyze the removal of hydrogen sulfide from the amino acids found in the protein molecules of the food. Moreover, food items also contain ferrous ions, which further reacts with hydrogen sulfide to form ferrous sulfide that is black in color.

Conclusion

The reason for the blackening of food can when the food inside it gets spoiled is the production of hydrogen sulfide gas that reacts with ferrous ion to form ferrous sulfide that is black in color.