Understanding the sensory changes of spoiled tofu is essential for food safety and quality control in tofu production and processing. Spoilage can be identified through changes in color, odor, and texture, primarily caused by microbial activity.
1. Color Changes
Fresh tofu should have a uniform, milky white appearance. Discoloration is often the first sign of spoilage:
- Yellowing: Commonly caused by Curtobacterium species, indicating early microbial contamination.
- Darkening or dull appearance: Often associated with Pseudomonas fluorescens, which affects surface quality and freshness.
- Reddish coloration: Typically caused by Lactobacillus brevis, signaling advanced fermentation and spoilage.
2. Odor Changes
Fresh tofu has a mild, neutral soybean aroma. Any abnormal odor indicates deterioration:
- Sour smell: Resulting from acid-producing bacteria.
- Rancid or fermented odor: Caused by cocci, streptococci, and various bacillus species.
- Putrid or unpleasant smell: Indicates severe spoilage and the product should not be consumed.
3. Texture and Surface Changes
Texture is a key indicator of tofu freshness:
- Sticky or slimy surface: Caused by microbial growth on the tofu surface.
- Stringy or filament-like residue when touched: A clear sign of advanced spoilage.
Key Food Safety Reminder
If tofu shows any of the above changes in color, smell, or texture, it should be considered spoiled and removed from the production line or retail shelf immediately to ensure food safety and brand protection.
