the statue of electronic publish :
South Dakota:M.S.( Kendall Uhrich, South Dakota State University, Dept. of Dairy Science:2019
abstract :
Micellar casein is a high-protein ingredient that can be used in process cheese
products (PCP) formulations. PCP is a dairy food prepared by blending dairy ingredients
(such as natural cheese, protein concentrates, butter, non-fat dry milk NFDM, whey powder, and
permeate) with nondairy ingredients (such as sodium chloride, water, emulsifying salts, color, and
flavors) and then heating the mixture with a continuous agitation to produce a
homogeneous product with an extended shelf-life.
The first objective of this study was to produce a highly concentrated micellar
casein (HC-MC) and evaluate its storage stability. Skim milk was pasteurized at 76پ‹C for
16 sec and kept at .4پ‹C until the following day. The skim milk was heated to 50پ‹C using
a plate heat exchanger and microfiltered (MF) with graded permeability (GP) ceramic
MF membrane system (0.1ƒتm) in a continuous feed-and-bleed mode (flux of 71.43 L/m2
per hour) using a 3پ~ concentration factor (CF). Subsequently, the retentate of the first
stage was diluted 2پ~ with soft-water (2 kg of water: 1kg of retentate) and again MF at
50پ‹C using a 3پ~ CF. The retentate of the second stage was then cooled to 4پ‹C and stored
overnight. The following day, the retentate was heated to 63پ‹C and MF in recirculationmode
(retentate recirculated to system balance tank) until total solid (TS) was
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approximately 22% (wt/wt). Consequently, the MF system temperature was increased to
74پ‹C and MF continued until permeate flux reached less than 3 L/m2 per hour. The HCMC
was then divided into three aliquots of approximately 10 kg each. The first portion
was a control, while 1% sodium chloride added to the second portion (T1) and 1%
sodium chloride + 1% sodium citrate was added to the third portion (T2). Treated HCMC
retentates were transferred at 74پ‹C to sterilized vials and stored at 4پ‹C to study the
storage stability every 30 d. This trial was repeated three times using separate lots of skim
milk. The HC-MC at d = 0 (immediately after manufacturing) contained average 25.41%
TS, 21.65% true protein (TP), 0.09% nonprotein nitrogen (NPN), and 0.55% noncasein
nitrogen (NCN). No difference (P > 0.05) was detected in the composition of control, T1,
and T2 HC-MC during the 60 d of storage at 4پ‹C. However, the NCN content increased
significantly (P < 0.05) from 0.55 to 0.76%, 0.55 to 0.82% and 0.55 to 0.94% in control,
T1, and T2, respectively, during the 60 d of storage at 4پ‹C. Mean aerobic bacterial count
in control, T1, and T2 at 0 d was 2.6, 2.5 and 2.8 log cfu/mL, respectively, and increased
significantly (P < 0.05) to 4.3, 4.06 and 5.3 log cfu/mL, respectively, after 60 d storage at
4پ‹C. Coliform, yeast, and mold were not detected during the 60 d of storage. This study
determined that HC-MC with > 25%TS and > 95% casein as % of TP can be
manufactured using ceramic MF membranes and could be stored up to 60 d at 4پ‹C with
no significant changes in the composition.