Sweetened condensed milk — principal spoilage type: What is the chief spoilage problem encountered in sweetened condensed milk under improper storage or contamination?

Introduction / Context:
Sweetened condensed milk (SCM) is a high-sugar dairy product where water activity is reduced. High dissolved sugar suppresses many bacteria but still allows growth of osmotolerant yeasts and some molds if contamination occurs. Understanding the predominant spoilage route is essential for setting appropriate hygienic controls.

Given Data / Assumptions:

• Product: sweetened condensed milk.
• Potential defects: yeast gas production, thickening by micrococci, or mold growth.
• We must select the chief or most characteristic spoilage type.

Concept / Approach:
Because of high sugar and low water activity, osmotolerant yeasts that can ferment sucrose may survive and produce carbon dioxide, leading to swelling, frothing, and off-flavors. Although surface molds can grow on exposed areas and some bacteria may cause changes in texture, the principal and most frequently cited spoilage is gassy fermentation by yeasts able to metabolize sucrose at reduced water activity.

Step-by-Step Solution:
Evaluate which organism group thrives in high-sugar matrices.Identify osmotolerant/sucrose-fermenting yeasts as primary survivors.Select gas formation by these yeasts as the chief spoilage mode.

Verification / Alternative check:
Processing guides for SCM highlight stringent hygiene and container integrity to prevent yeast ingress because once present, gassy spoilage proceeds rapidly despite sugar preservation.

Why Other Options Are Wrong:

• Thickening by micrococci: Not the chief spoilage in high-sugar SCM.
• Mold colonies: Possible on surfaces or leaky containers, but not the predominant issue in sealed, properly handled cans.
• All of the above: Overbroad; one main spoilage is expected.
• Lipase rancidity only: Less typical in SCM due to product composition and heat treatment.

Common Pitfalls:
Assuming high sugar eliminates spoilage risk; in fact, it shifts the flora toward osmotolerant yeasts capable of gas production.

Final Answer:
Gas formation by sucrose-fermenting yeasts.