Effect of skim milk treated with high hydrostatic pressure on permeate flux and fouling during ultrafiltration

Abstract

Ultrafiltration (UF) is largely used in the dairy industry to generate milk and whey protein concentrate for standardization of milk or production of dairy ingredients. Recently, it was demonstrated that high hydrostatic pressure (HHP) extended the shelf life of milk and improved rennet coagulation and cheese yield. Pressurization also modified casein micelle size distribution and promoted aggregation of whey proteins. These changes are likely to affect UF performance. Consequently, this study determined the effect of skim milk pressurization (300 and 600 MPa, 5 min) on UF performance in terms of permeate flux decline and fouling. The effect of HHP on milk proteins was first studied and UF was performed in total recycle mode at different transmembrane pressures to determine optimal UF operational parameters and to evaluate the effect of pressurization on critical and limiting fluxes. Ultrafiltration was also performed in concentration mode at a transmembrane pressure of 345 kPa for 130 or 140 min to evaluate the decline of permeate flux and to determine fouling resistances. It was observed that average casein micelle size decreased by 32 and 38%, whereas β-lactoglobulin denaturation reached 30 and 70% at 300 and 600 MPa, respectively. These results were directly related to UF performance because initial permeate fluxes in total recycle mode decreased by 25% at 300 and 600 MPa compared with nonpressurized milk, critical flux, and limiting flux, which were lower during UF of milk treated with HHP. During UF in concentration mode, initial permeate fluxes were 30% lower at 300 and 600 MPa compared with the control, but the total flux decline was higher for nonpressurized milk (62%) compared with pressure-treated milk (30%). Fouling resistances were similar, whatever the treatment, except at 600 MPa where irreversible fouling was higher. Characterization of the fouling layer showed that caseins and β-lactoglobulin were mainly involved in membrane fouling after UF of pressure-treated milk. Our results demonstrate that HHP treatment of skim milk drastically decreased UF performance.

High Hydrostatic Pressure Induced Changes in the Physicochemical and Functional Properties of Milk and Dairy Products: A Review

“…High-pressure treatment of milk and dairy products affects the color parameters and turbidity; these physicochemical properties tend to be modified [10,31,51,52,61,62]. The changes in the color and turbidity in milk have been attributed to the effects of HPP on fat globules and casein micelles, as previously explained in Sections 3.1 and 3.2.1, respectively [10,15,31,51,52].…”

“…Overall, skimmed milk has a decreased opacity and smaller lightness or L* values when compared to whole milk; additionally, subjecting skimmed milk to pressures that exceed 300-400 MPa also results in reduced turbidity [31]. Whole milk behaves slightly differently due to the presence of fat, which acts as a protective barrier; thus, the L* values and opacity are expected to be higher; however, subjecting whole milk to intense-pressure treatments has been shown to reduce its whiteness levels, turbidity, and opacity [10,31,51,52,62]. The a* and b* parameters of the CIE L*a*b* scale of color-which represent the green to redness and blue to yellowness color ranges, respectively-are mostly influenced by the fat and β-carotene content in milk, and high pressure may alter these values; however, lightness is the parameter that is most severely affected by HPP treatments [51].…”

The efficacy and safety of high‐pressure processing of food

“…Although pressures up to 100 MPa did not induce denaturation at room temperature (López‐Fandino et al., 1996; Huppertz et al., 2004a; Ye et al., 2004), denaturation increased with pressure and longer holding times (Kleber et al., 2007; Bravo et al., 2012). Treatments up to 30 min at 400–500 MPa in bovine milk caused 30%‐60% β‐Lg denaturation (Scollard et al., 2000a) and may increase to above 90% at pressures above 600 MPa (Ye et al., 2004; Leu et al., 2017). In an experiment where 600 MPa for 15 min were applied to achieve a reduction of at least 7 log 10 cycles of three food‐borne bacteria ( L. monocytogenes , S. aureus and Pseudomonas aeruginosa ) about 80% of the β‐Lg was denatured (Ramos et al., 2015).…”

Effect of Pectinolytic Enzyme Pretreatment on the Clarification of Cranberry Juice by Ultrafiltration

“…UF of fresh and depectinized juices was performed in a crossflow filtration unit (SEPA-CF, Sterlitech, Kent, WA, USA) as described by Leu et al [27]. A refrigeration coil maintained the fresh and depectinized juices at a constant temperature of 15 • C. The membrane module consisted of a polyvinylidene difluoride (PVDF) flat-sheet UF membrane (Synder filtration inc. Vacaville, CA, USA) with an active filtration surface of 0.014 m 2 and spacer thickness of 31 mil on the feed side.…”