Table 4.

Transmembrane pressure (TMP)_(±1 experimental error value)_(10⁵ Pa) at the beginning of MF (TMP_i), at the end of MF (TMP_f,) and change in TMP (ΔTMP) after 330 min microfiltration for 1.4 μm microfiltered (M-SMilk), thermized (T-SMilk) or pasteurized (P1-SMilk, P2-SMilk) skimmed milks. Storage time at 4 °C (48 or 96 h) is for raw milk before skimming and microbiological stabilization. Operating conditions: 0.1 μm ceramic membrane; uniform transmembrane pressure system; permeation flux, Jp = 75 L·h⁻¹·m⁻²; volume reduction ratio = 3.0; T = 50 °C).

-	48 h Storage of Raw Milk			96 h Storage of Raw Milk
Milk Type	TMPi	TMPf	ΔTMP	TMPi	TMPf	ΔTMP
M-SMilk	0.53 ± 0.04	0.56 ± 0.04	0.03 ± 0.08	0.50 ± 0.04	0.53 ± 0.04	0.03 ± 0.08
T-SMilk	0.52 ± 0.04	0.56 ± 0.04	0.04 ± 0.08	0.56 ± 0.04	0.69 ± 0.04	0.13 ± 0.08
P1-SMilk	0.52 ± 0.04	0.55 ± 0.04	0.03 ± 0.08	0.57 ± 0.04	0.71 ± 0.04	0.14 ± 0.08
P2-SMilk	0.48 ± 0.04	0.52 ± 0.04	0.04 ± 0.08	0.47 ± 0.04	0.54 ± 0.04	0.07 ± 0.08

For M-SMilk, ∆TMP remained low (0.03 × 10⁵ Pa), regardless of the 4 °C storage duration of raw milk (Table 4). After 4 °C storage for 48 h, heat-treated milks (T-SMilk, P1-SMilk and P2-SMilk) also had low ∆TMP (0.04 × 10⁵ Pa). For T-SMilk, bactofugation had little influence on ∆TMP (results not shown). For pasteurized milks, ∆TMP were similar (0.04 × 10⁵ Pa) for P1-SMilk (low bacteria count, 2.0 g·kg⁻¹ of residual fat) and P2-SMilk (low bacteria count, 0.5 g·kg⁻¹ of residual fat). Conversely, after 4 °C storage for 96 h, TMP increased for heat-treated milks: by 23% for T-SMilk (by 15% when stored for 72 h; results not shown), and by 25% and 15% for P1-SMilk and P2-SMilk, respectively.