Investigation on Bacterial Growth and pH in Milk after the Expiration Date

Figure 8

The gross appearance of three types of milk samples opened at different time points after expiration and left at room temperature for 0–24 hours after opening. (a–c) Whole milk (a), 2% milk (b), and fat-free milk (c) immediately after opening on the day of expiration. All three appear as homogeneous white emulsions. (d–f) Whole milk (d), 2% milk (e), and fat-free milk (f) immediately after opening at 10 days after expiration. No visible changes when compared to the day of expiration. (g) Whole milk opened at 6 days after expiration and left open at room temperature for 24 hours appears thickened with lumps. (h) 2% milk sample opened at 8 days after expiration and left open at room temperature for 24 hours appears thickened with lumps. (i) Fat-free milk opened at 10 days after expiration and left at room temperature for 24 hours appears homogeneous.