Evelyne Boyaval

Acidification of pressure-treated milk

Abstract The behaviour of reconstituted pressure-treated milk towards acidification with glucono-delta-laclone (GDL) was studied. After high-pressure treatment at 250, 450 or 600 MPa for 30 min, GDL was added for 20 h at 4 °C and soluble minerals, 1H NMR relaxation rate and solvation changes with pH were studied, as well as the buffering properties of milk. Solubilization of calcium and phosphorus with pH, changes in a 1H NMR relaxation rate and solvation with pH were enhanced by the pressure treatment between pH 6.8 and 5.2. Between pH 6.8 and 6.1, the changes appeared to be independent of the pressure level, while between pH 6.1 and 5.2, they became dependent on the pressure level. The results are discussed in terms of pH and buffering changes due to the compression-decompression cycle.

Nanofiltration for the recovery of caustic cleaning-in-place solutions: robustness towards large variations of composition

In the dairy industry re-use and multi-use cleaning-in-place (CIP) systems are operated by circulating chemicals and water without taking the equipment apart. The solutions, which become polluted due to the removal of fouling compounds, are drained periodically when they are considered to be too polluted. This work shows the large variations in composition (pollution, surface tension, etc) of the industrial caustic solutions coming from milk standardization and pasteurization plant CIP throughout their life time (7 days) and from 1 week to another. The work is also intended to show how nanofiltration (1 kg mol(-1) molecular weight cut-off) was robust and performed well, with good recovery of caustic solutions, even when faced with large variations of solutions composition: high caustic yield, permeation flux (J) in the range 42-110 l h(-1) m(-2), average chemical oxygen demand (COD) reduction equal to 0.58 and low surface tension change. Equations have been established for the prediction of J as a function of initial membrane hydraulic resistance (Rm) caustic concentration, volume reduction ratio (VRR) and initial soluble COD. When VRR increased, both J and pollution retention decreased despite the increase in irreversible fouling induced by the increase of soluble pollution concentration in retentate. The higher the initial soluble COD, the sharper the decrease in J vs. VRR. Since irreversible fouling was usually small (0.1-3.4 x 10(13) m(-1), that is to say of the same order of magnitude as Rm), the membrane cleaning could be efficiently performed by using single phase sodium hypochlorite alternately with a more expensive acid-base cleaning sequence. The obtained permeate was a clear regenerated cleaning solution with low soluble COD (0.2-3.5 g/l) and surface tension (56-30 mJ m(-2)) which could be successfully exploited owing to its cleaning potential.

Nanofiltration for the recovery of caustic cleaning-in-place solutions: robustness towards large variations of composition☆

In the dairy industry, whatever the cleaning-in-place CIP mode of operation, the cleaning solutions, which become polluted due to the removal of fouling compounds, are drained periodically. The objective of the work is to investigate how large variations of the composition of industrial CIP caustic solutions alter nanofiltration reported to be an efficient membrane separation for the recovery of caustic solutions. The obtained nanofiltrate was a clear regenerated cleaning solution with low soluble chemical oxygen demand, COD (0.2–3.5 g L−1) and surface tension (56–30 mJ m−2) which could be successfully exploited owing to its cleaning potential.