Abstract
Concentrated micellar casein (CMC) is a high-protein ingredient that can be used in process cheese product formulations. The objectives of this study were to develop a process to produce CMC and to evaluate the effect of sodium chloride and sodium citrate on its storage stability. Skim milk was pasteurized at 76°C for 16 s and cooled to ≤4°C. The skim milk was heated to 50°C using a plate heat exchanger and microfiltered with a graded permeability (GP) ceramic microfiltration (MF) membrane system (0.1 μm) in a continuous feed-and-bleed mode (flux of 71.43 L/m2 per hour) using a 3× concentration factor (CF) to produce a 3× MF retentate. Subsequently, the retentate of the first stage was diluted 2× with soft water (2 kg of water: 1 kg of retentate) and again MF at 50°C using a 3× CF. The retentate of the second stage was then cooled to 4°C and stored overnight. The following day, the retentate was heated to 63°C and MF in a recirculation mode until the total solids (TS) reached approximately 22% (wt/wt). Subsequently, the MF system temperature was increased to 74°C and MF until the permeate flux was <3 L/m2 per hour. The CMC was then divided into 3 aliquots (approximately 10 kg each) at 74°C. The first portion was a control, whereas 1% of sodium chloride was added to the second portion (T1), and 1% of sodium chloride plus 1% of sodium citrate were added to the third portion (T2). The CMC retentates were transferred hot to sterilized vials and stored at 4°C. This trial was repeated 3 times using separate lots of skim milk. The CMC at d 0 (immediately after manufacturing) contained 25.41% TS, 21.65% true protein (TP), 0.09% nonprotein nitrogen (NPN), and 0.55% noncasein nitrogen (NCN). Mean total aerobic bacterial counts (TBC) in control, T1, and T2 at d 0 were 2.6, 2.5, and 2.8 log cfu/mL, respectively. The level of proteolysis (NCN and NPN values) increased with increasing TBC during 60 d of storage at 4°C. This study determined that CMC with >25% TS and >95% casein as percentage of TP can be manufactured using GP MF ceramic membranes and could be stored up to 60 d at 4°C. The effects of the small increase in NCN and NPN, as well as the addition of sodium chloride or sodium citrate in CMC during 60 d of storage on process cheese characteristics, will be evaluated in subsequent studies.
Highlights
Microfiltration (MF) is a membrane process used to separate CN micelles (0.1–0.40 μm) and serum whey proteins (SP; 0.003–0.010 μm) from skim milk, using a semipermeable membrane with a pore size of 0.1 μm
When MF is applied to skim milk, CN is concentrated in the retentate and called micellar casein concentrate (MCC), whereas SP, lactose, soluble minerals, and water pass through the membrane to the permeate
Micellar casein concentrate has been manufactured from skim milk using different MF membranes, such as polymeric spiral-wound (SW) membranes (Govindasamy-Lucey et al, 2007; Lawrence et al, 2008; Zulewska et al, 2009; Beckman et al, 2010; Beckman and Barbano, 2013; Hammam et al, 2021; Marella et al, 2021) or ceramic membranes, including uniform transmembrane pressure (UTP) and graded permeability (GP) membranes (Zulewska et al, 2009; Hurt and Barbano, 2010; Hurt et al, 2010; Adams and Barbano, 2013, 2016; Zulewska and Barbano, 2014; Hammam and Metzger, 2018)
Summary
Microfiltration (MF) is a membrane process used to separate CN micelles (0.1–0.40 μm) and serum whey proteins (SP; 0.003–0.010 μm) from skim milk, using a semipermeable membrane with a pore size of 0.1 μm. Micellar casein concentrate has been manufactured from skim milk using different MF membranes, such as polymeric spiral-wound (SW) membranes (Govindasamy-Lucey et al, 2007; Lawrence et al, 2008; Zulewska et al, 2009; Beckman et al, 2010; Beckman and Barbano, 2013; Hammam et al, 2021; Marella et al, 2021) or ceramic membranes, including uniform transmembrane pressure (UTP) and graded permeability (GP) membranes (Zulewska et al, 2009; Hurt and Barbano, 2010; Hurt et al, 2010; Adams and Barbano, 2013, 2016; Zulewska and Barbano, 2014; Hammam and Metzger, 2018). In a study that compared different MF membranes, the flux was higher in UTP and GP ceramic membranes (54 and 72 L/m2 per hour, respectively) than in SW membranes (16 L/m2 per hour) when skim milk was MF at 50°C in a continuous feed-and-bleed mode using a 3× concentration factor
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