The Use of Membrane Filtration to Increase Native Whey Proteins in Infant Formula

Abstract

The introduction of membrane filtration during infant milk formula (IMF) processing represents an innovative approach to increasing native protein content compared to standard IMF. The objective of this study was to compare IMF powder produced using a standard process and IMF produced from raw bovine skim milk with added whey protein isolate using a split-stream process incorporating a ceramic 1.4 μm filter followed by a polyvinylidene difluoride polymeric 0.2 μm filter. Retentates from 0.2 μm microfiltration (MF) were blended with fat, lactose, and minerals and subsequently high-temperature treated (125 °C × 5 s). The heat-treated retentate was merged with the permeate from the 0.2 μm MF, homogenised, and spray-dried (referred to as membrane-filtered IMF or MEM-IMF). A control IMF was also produced using standard treatment (referred to as high-temperature IMF or HT-IMF) without membrane filtration. Both IMF products were characterised by high-performance liquid chromatography, particle size, and enzyme activity assays. MEM-IMF powder had significantly higher amounts of native (1.1 g per 100 g powder) and monomeric (1.48 g per 100 g powder) whey proteins when compared to 0.18 and 0.46 g per 100 g powder in HT-IMF, respectively. MEM-IMF also exhibited a lower degree of protein aggregation compared to HT-IMF. Comparison of microbial and Maillard by-products markers demonstrated that a safe IMF product could be produced at scale, although levels of the Maillard by-product marker, carboxymethyl-lysine, were not significantly reduced in MEM-IMF. This study demonstrates how membrane filtration can be used to retain native proteins during IMF manufacture.

Comparison of conventional heat-treated and membrane filtered infant formulas using an in vitro semi-dynamic digestion method

“…4) have been reported previously and described in detail. 22 The results from both SDS-PAGE and SEC-HPLC showed that the amounts of water soluble whey proteins were continuously declining during the course of digestion, while the peptide release reached a peak at GE4 in the MEM-IMF samples. Interestingly, the amount of water soluble proteins detected in the HT-IMF digesta was similar from GE3 to GE5 (Fig.…”

“…5B2–B5). 22 Moreover, our previous study had demonstrated that MEM-IMF exhibited residual activity of indigenous enzymes, such as alkaline phosphatase, whereas these enzymes are fully inactivated in the HT-IMF. 22 Hence, MEM-IMF shows a higher initial primary amine content (Fig.…”

“…22 Moreover, our previous study had demonstrated that MEM-IMF exhibited residual activity of indigenous enzymes, such as alkaline phosphatase, whereas these enzymes are fully inactivated in the HT-IMF. 22 Hence, MEM-IMF shows a higher initial primary amine content (Fig. 1, concentration of primary amines, GE0 to GE2) possibly due to the preservation of activated indigenous proteases which may contribute to the digestion of the MEM-IMF, and to the digestion of human milk, as has been shown previously.…”

“…The processing of both IMFs has been described previously. 22 Briefly, both formulas were designed for infants from birth to 6 months (whey protein to casein ratio of 60 : 40) and produced at a pilot scale in the Biofunctional Engineering Facility, Teagasc Food Research Centre. The ratio of macronutrients, protein : lactose : fat, was 1.29 : 7 : 3.49, respectively.…”

“…The membrane filtered IMF (MEM-IMF) can significantly increase the content of native whey proteins. 22 The new process altered the protein hydrolysis profile, amino acid release and protein degradation as demonstrated by a static in vitro adult digestion model, compared to the IMF produced using a high-temperature process (HT-IMF). 23 However, the effect of membrane filtration on the in vitro gastric behaviour still remains unclear, partly due to the limitations of static digestion methods.…”