ArticlePDF Available

Abstract and Figures

Several freeze-drying and spray-drying methods were investigated in relation to the retention of immunoglobulins (Ig) A, IgG and IgM. Spray drying produced human milk powders with 2% humidity and a good retention of IgG (>88%) and IgM (∼70%). However, only 38% of IgA remained after spray-dying. For freeze-drying, only the highest heating plate temperature used in this study (40°C) brought IgA content down to 55% in a powder with 1.75% residual humidity, whereas milk samples undergoing lower temperatures had higher preservation rates (75% for IgA and 80% for IgG and IgM) and higher residual moisture contents. From these results, it can be concluded that IgA is the most sensitive Ig lost during drying processing of human milk. The best method to generate human milk powders without a significant loss of Ig was thus freeze-drying at 30°C heating plate temperature, which accelerated the process compared to lower processing temperatures, but still had good overall Ig retention.
Content may be subject to copyright.
LDRT #1141781, VOL 0, ISS 0
Spray and freeze drying of human milk on the retention of immunoglobulins
(IgA, IgG, IgM)
Jorge Castro-Albarrán, Blanca Rosa Aguilar-Uscanga, Frédéric Calon, Isabelle St-Amour, Josué Solís-Pacheco,
Linda Saucier, and Cristina Ratti
QUERYSHEET
This page lists questions we have about your paper. The numbers displayed at left can be found in the text of the paper for reference. In
addition, please review your paper as a whole for correctness.
Q1: Au: Please check and confirm the reference. “Permanyer et al.” does not match with the [10].
Q2: Au: Please check and confirm the in-text callout “Fig. 6a”. Only 4 figures were supplied.
Q3: Au: Please check and confirm the in-text callout “Fig. 6b”. Only 4 figures were supplied.
TABLEOFCONTENTSLISTING
The table of contents for the journal will list your paper exactly as it appears below:
Spray and freeze drying of human milk on the retention of immunoglobulins (IgA, IgG, IgM)
Jorge Castro-Albarrán, Blanca Rosa Aguilar-Uscanga, Frédéric Calon, Isabelle St-Amour, Josué Solís-Pacheco, Linda Saucier, and Cristina Ratti
DRYING TECHNOLOGY
http://dx.doi.org/10.1080/07373937.2016.1141781
5Spray and freeze drying of human milk on the retention of immunoglobulins
(IgA, IgG, IgM)
Jorge Castro-Albarrána, Blanca Rosa Aguilar-Uscangaa, Frédéric Calonb,c, Isabelle St-Amourc, Josué Solís-Pachecoa,
Linda Saucierb, and Cristina Rattib
aLaboratorio de Microbiología Industrial, Centro Universitario de Ciencias Exactas e Ingeniería, Universidad de Guadalajara, Guadalajara,
10 Jalisco, México; bInstitut sur la nutrition et les aliments fonctionnels (INAF), Université Laval, Québec, Québec, Canada; cCentre de Recherche
du CHU de Québec (CHUL), Axe Neurosciences, Québec, Québec, Canada
ABSTRACT
Several freeze-drying and spray-drying methods were investigated in relation to the retention of
immunoglobulins (Ig) A, IgG, and IgM. Spray drying produced human milk powders with 2%
humidity and a good retention of IgG (>88%) and IgM (70%). However, only 38% of IgA remained
after spray drying. For freeze drying, only the highest heating plate temperature used in this study
(40°C) brought IgA content down to 55% in powder with 1.75% residual humidity, whereas milk
samples undergoing lower temperatures had higher preservation rates (75% for IgA and 80% for
IgG and IgM) and higher residual moisture contents. From these results, it can be concluded that
IgA is the most sensitive Ig lost during drying processing of human milk. The best method to
generate human milk powders without a significant loss of Ig was thus freeze drying at 30°C
heating plate temperature, which accelerated the process compared to lower processing
temperatures, but still had good overall Ig retention.
KEYWORDS
Freeze drying; human milk;
immunological properties;
spray drying
30
Introduction
Mother’s milk contains compounds that greatly
contribute to the development of immune and digestive
systems, as well as the general growth and immuno-
35 logical support of infants.
[1]
A wide array of important
compounds, such as vitamins and fatty acids, immuno-
globulins (Ig) A, IgG, IgM, and IgD, are all found in
human milk. Of these, IgA, which appears to be both
synthesized and stored in the breast,
[2]
plays a crucial
40 role. Indeed, IgA sheets the intestinal epithelium,
thereby protecting the mucosal surfaces against
entry of pathogenic bacteria and enteroviruses. It
bestows protection against Escherichia coli, Salmonellae,
Shigellae, Streptococci, Staphylococci, Pneumococci,
45 poliovirus, and the rotaviruses.
[3]
When the mother’s own milk is unavailable, the
American Academics of Pediatrics
[4]
recommends using
donor milk. For this purpose, human milk banks have
been created. To reduce the risk of microbial contami-
50 nation that can occur during collection and handling
of human milk, it has to be pasteurized to reduce the
number of viable pathogens.
[5]
The guideline for human
milk banks in the USA and in Spain is to use low-
temperature long-time pasteurization,
[6]
usually 62.5°C
55for 30 min. A study done by Evans et al.
[7]
on pasteur-
ization of human milk for 30 min and temperatures
ranging from 60 to 70°C showed that IgA was preserved
with relative little loss until 70°C (33% loss), while IgG
and lactoferrin were much more labile, displaying losses
60of 77.2 and 85%, respectively, at 65°C. Following
heating for 30 min at 62.5°C, the initial contents of
IgG, lactoferrin, and lysozyme were reduced by 34, 57,
and, 23%, respectively, while IgA content remained
stable.
[7]
However, Permanyer et al.
[6]
found that
65pasteurization of human milk, using the same heating
conditions, induced a 30% decrease in IgA. Other
reports indicate that IgA is stable up to 56°C but
heat-labile at 62.5°C
[8]
and that temperature but not
process time is a critical parameter in determining
70IgA stability.
[9]
Studies by Friend et al.
[10]
reported
reductions of 47, 55, 39, and 73% of lactoperoxidase,
lipase, lysozyme, and protease, respectively, after pas-
teurization of human milk at 62.5°C for 30 min. Hence,
even if human milk is safe for consumption from
75a microbiological point of view after low-temperature/
long-time pasteurization, the potential detrimental
effect of this traditional type of preservation method
on bioactive compounds within human milk should also
be taken into account.
CONTACT Cristina Ratti cristina.ratti@fsaa.ulaval.ca Institut sur la nutrition et les aliments fonctionnels, Université Laval, SGA–FSAA,
2425 rue de l’agriculture, Québec (QC), G1V 0A6, Canada.
© 2016 Taylor & Francis
3b2 Version Number : 11.0.3184/W Unicode (Apr 10 2014)
File path : {1TFJATS}LDRT/v0n0/LDRT1141781/LDRT_A_1141781_J.3d
Date and Time : 16/9/16 and 17:31
80 Storage of human milk was studied after
pasteurization,
[7,10]
cooling or freezing,
[7,11]
and freeze
drying.
[7,10,12]
Recently, Lozano et al.
[12]
suggested that
the stability of human milk, in terms of vitamins, fatty
acids, and antioxidant levels, was higher in freeze-dried
85 milk powders than the reported values for frozen or
fresh milk after the same length of storage.
Milk can be converted into shelf-stable powders by
spray-drying or freeze-drying methods. Spray drying is
a dehydration method where a liquid/slurry is sprayed
90 in fine droplets in contact with air at elevated tempera-
tures. This method is commonly used to dry milk, whey,
yeast, and other high-value products in industry due to
the good final quality of spray-dried powders. Feed flow
rate, atomizer rotation speed, and inlet air temperature
95 have been identified as key parameters affecting powder
quality during spray-drying dairy emulsions such
as whole milk.
[13]
Energy consumption is, however,
a restriction in the widespread use of this drying
method. In addition, the oxygen present in the large
100 volumes of air mixed with the droplets as well as the
high operating temperatures during spray drying could
have a negative impact not only on fat-soluble vitamins
and in CLA contents in milk due to oxidation but also
on other heat-labile compounds such as IgG and IgA.
105 To the best of our knowledge, no studies have been
reported on spray drying of human milk.
Freeze drying is an alternative dehydration method
based on sublimation of the ice contained in a frozen
material and is recognized for producing final products
110 of the highest quality.
[14]
This method is an expensive
process due to increased energy consumption during
the long processing times under vacuum and thus its
application to the food industry has been limited. Freeze
drying of human milk (previously frozen at 80°C)
115 during 24 h in a benchtop unit at 10
3
mBar pressure
and 46°C condenser temperature was proposed
as a good alternative to preserve human milk.
[12]
When
compared to frozen milk at 20°C, the concentrations
of vitamins C and E as well as antioxidant capacity
120 are better retained in freeze-dried human milk. In terms
of Ig, a previous study done by Evans et al.
[7]
suggests
that deep freezing at 20°C is a satisfactory procedure
compared to the more expensive freeze drying (no
operating conditions specified), which showed no
125 additional benefit in this study.
Most of the previous studies on preservation
of human milk have used pasteurization or heat treat-
ments, followed by cool storage or freezing, providing
recommendations mainly focused on bacterial content.
130 However, the combination of both processes (heat pro-
cessing and storage conditions) can lead to a decrease in
bioactive compounds, such as Ig. Other preservation
methods like freeze drying have been studied from the
standpoint of feasibility and final quality of the product,
135but little has been analyzed on the determination of
optimal process conditions in order to decrease costs.
Also, no previous studies have addressed the effect
of human milk dehydration processes on bioactive
immunological components. Furthermore, the use of
140a dehydration method to preserve mother’s milk could
be more beneficial than pasteurization by producing
a powder that can be stored at cold temperatures for
long times without loss in bioactive properties. Thus,
the aim of this work was to study freeze-drying and
145spray-drying methods with different operating con-
ditions for the conservation of human milk with specific
focus on Ig preservation. Determinations of sorption
isotherms and glass transition temperature (T
g
) of
the final powders complete this work in order to have
150indicators about their specific storage conditions.
Materials and methods
Ethical considerations
This study was approved by the Ethical Research
Committee of Université Laval (Québec, Canada) in
155April 2014 (# 2014-034/14-04-2014). Volunteer donors
provided a written agreement about the donation of
excess human milk for this study.
Human milk samples
Surplus human milk was obtained from healthy
160mothers during lactation between 4 and 8 months after
giving birth. Milk was collected in their homes using
an electric extraction pump (Medela
1
), placing the
collected milk in “Pump and Save Bags” (Medela
1
),
and storing afterwards in a freezer at 18°C until
165further processing.
Human milk preparation
All human milk samples (for spray or freeze drying)
were thawed in their storage bags in a water bath
at 30°C for 20–30 min. Several samples (n ¼10) were
170randomized and pooled for each repetition. The pooled
milk was subjected to one cycle of homogenization
at 5,000 psi in an Emulsiflex C50 (Avestin
1
, Mannheim,
Germany).
Freeze drying of human milk
175Thirty (30) mL of pooled milk was poured in Petri
dishes of 9-cm external diameter; the liquid samples
2 J. CASTRO-ALBARRÁN ET AL.
have a thickness of approximately 8 mm. The Petri
dishes were covered and placed inside a Sanyo medical
freezer (MDF 235, Gunma, Japan) at 40°C for a mini-
180 mum of 9 h. Then, the samples were placed inside the
drying chamber of a Virtis freeze dryer (Unitop 4001,
Gardinier, NY, USA), working under vacuum of less
than 30 mTorr, at 85°C condenser temperature (con-
denser separated from the drying chamber), and at 20,
185 30, 4°C heating plate temperatures. In order to establish
freeze-drying kinetics and thus to estimate the final
freeze-drying time at each heating plate temperature,
drying curves were obtained by periodically weighing
the milk samples for up to 10 h. The temperature at
190 the center of the milk sample was followed throughout
the freeze-drying process with a T thermocouple
(TMQSS-040G-18, Omega, Stamford, CT, USA), which
was inserted in the sample center prior to freezing. Final
humidity was determined as described later.
195 Simplified mathematical models were used to
quantify drying kinetics of various food products.
[15]
In this study, experimental data were fitted to the Page’s
equation:
[16]
XXe
X0Xe¼exp k tn
ð Þ ð1Þ
200 where X, X
o,
and X
e
are moisture content in dry basis,
initial, and equilibrium moisture content, respectively,
k is the drying constant (h
n
), n is the Page’s model
parameter, and t is the process time (h). Several
previous works have suggested that X
e
can be neglected
205 in Eq. (1) since it is significantly lower than moisture
content for most of the drying process.
[17]
Spray drying of human milk
Homogenized human milk was kept at 30°C until
the spray-drying process. Spray drying was done in
210 a Niro-Atomizer pilot unit with conical base (Model
209/S, Soeborg, Denmark) fed with a Watson Marlow
1
(Model 503U) peristaltic pump and a nozzle atomizer
(three bar pressure). In order to maximize the yield,
preliminary tests based on overall performance and final
215 powder humidity were done, from which the following
spray-drying operation variables were selected: 180 and
160°C inlet air temperature with feeding rates of 5 and
4 mL/min, respectively. Outlet air temperature was
recorded and yield could be estimated from gravimetric
220 measurements. Final humidity was determined
as described later.
In both spray-drying and freeze-drying processes, the
final product was kept in dark conditions, in desiccators
at 5°C with the presence of Drierite
R
, until further
225analysis.
Humidity and dry mass determination
Total solids and humidity of the dried samples were
determined with a halogen balance HR73-P (Mettler
Toledo
1
, Greifensee, Switzerland). Humidity was
230determined on a wet basis in duplicate measurements.
Immunoglobulin determination
Human milk powders (1 g) were rehydrated to
their initial moisture content by dissolution in distilled
water (approximately 7.15 mL) at room temperature,
235followed by agitation homogenization and centrifuga-
tion at 1500 rpm for 5 min in order to obtain the Ig
in the whey, which was separated and analyzed by
ELISA.
ELISA quantification was performed as previously
240described
[18]
to determine the concentrations of Ig.
Goat antibodies specific to the Fc fragment of human
IgG, IgM, or IgA were used for capture, and the
corresponding HRP-conjugated antibodies, for detec-
tion (all purchased from Jackson Immuno Research
245Laboratories Inc., West Grove, PA, USA). The standard
curves were performed using IgA from human
colostrum (1–10 ng/mL, Sigma-Aldrich, Saint Louis,
MO, USA), IgG from human serum (2.5–50 ng/mL,
Sigma-Aldrich), and IgM from human serum
250(2.5–50 ng/mL, Sigma-Aldrich). The results were
expressed in micrograms per milliliter (µg/mL) of
rehydrated milk.
Sorption isotherms
Lithium chloride (LiCl), sodium chloride (NaCl),
255sodium bromide (NaBr), magnesium chloride (MgCl
2
),
and potassium acetate (CH
3
COOK) saturated
salt solutions were prepared according to the method
described by Ratti et al.
[19]
Relative humidity of the
solutions was verified at ambient temperature
260(20°C) with an AquaLab (Series 3, Decagon Devices
Inc., Pullman, Washington, USA): 14.1% (LiCl), 75.6%
(NaCl), 57% (NaBr), 33% (MgCl
2
), and 25.3%
(CH
3
COOK). Freeze-dried and spray-dried human milk
powders (approximately 300 mg) were placed in alumi-
265num cups over the saturated salt solutions in desiccators
at constant temperature (20°C) until equilibrium was
reached in approximately 7 days.
The dry matter of the solids was determined at 60°C
in a vacuum oven using P
2
O
5
as desiccant. Sorption
270experiments were done in duplicate.
DRYING TECHNOLOGY 3
Experimental sorption data were fitted to the GAB
model
[20]
using the nonlinear regression function of
SigmaPlot 11.0:
[30]
Xe¼XmC K aw
1K aw
ð Þ 1K awþC K aw
ð Þ ð2Þ
275 where a
w
is the water activity and X
m
, C, and K are the
GAB model constants.
Glass transition temperature
Glass transition temperature (midpoint) was deter-
mined by differential scanning calorimeter (DSC) using
280 a thermal analysis system DSC Pyris 1 (Perkin Elmer)
connected to a PC for simultaneous data treatment
(Pyris Software for Windows version 3.52) and to a
refrigeration system with a compressor. The instrument
was calibrated for temperature and heat flow with
285 indium (T
m
¼156.6°C and ΔH ¼28.45 J/g, Perkin
Elmer standard) and checked with distilled water for
which T
m
¼0°C and ΔH ¼333 J/g.
[21]
A 30-mg sample
of each human milk powder was transferred into a high-
volume stainless steel pan (Product #03190029, Perkin
290 Elmer), where an O-ring was inserted. The capsule
was sealed with a cover and immediately weighed. A
similar empty capsule was used as a reference. Capsules
were cooled to 20°C. Scanning was performed by
heating at 5°C/min from 20 to 120°C. The glass tran-
295 sition appeared as an endothermic shift in the specific
heat capacity. Results were obtained in triplicate.
Statistical analysis
Due to limited quantity of collected mother’s milk
available for these studies, only duplicate experiments
300 (n ¼2) were done for each treatment. Results are
reported as the average value with associated standard
error. Nonparametric ANOVA was performed on the
data (Friedman and Kruskal–Wallis tests) using Dunn’s
multiple comparison and with initial concentration
305 as control. Differences were considered significant
at p <0.05.
Results and discussion
Spray drying
Initial solid content of fresh human milk was found to
310be 11.57 0.58%(w/w). Lawrence
[22]
reported a solid
content of 12.0% in mature human milk and 12.8% in
colostrum, whereas Picciano et al.
[23]
found values of
11.85 1.43%. Table 1 shows the parameters resulting
from spray drying of human milk at different operating
315variables. For both combinations of inlet temperature
and flow rate operating variables, the average of powder
humidity obtained after the process was 2.05 0.14%.
However, exit air temperature was 10° higher for a 20°
increase in inlet air temperature, even if the liquid flow
320rate was increased from 4 to 5 mL/min.
Freeze drying
Figure 1a shows the product temperature (dotted line)
during freeze drying of human milk samples at 20, 30,
and 40°C heating plate temperature (solid lines).
325The temperature curves obtained in this work were
similar to most curves available in the literature for pro-
duct temperature increase during the freeze-drying
process.
[24]
The initial temperature of both the heating
plate and product after freezing was 30°C. As the
330temperature of the heating plate was raised, product
temperature increased with a delay corresponding to
the sublimation time. The duration of the sublimation
step had a good correlation with the heating plate
temperature (1.3, 3.0, and 4.5 h for 40, 30, and 20°C,
335respectively). After all the ice was sublimated, the product
temperature increased gradually to reach the heating
plate temperature, the times when the product tempera-
ture reaches 20, 30, or 40°C being 5.2, 7.7, and 8.5 h,
respectively.
340Freeze-drying curves of human milk are presented in
Fig. 1b. Drying rates were fast during the first phase of
drying and slowed down at the end of the process as
expected from the increase of the dry-layer resistance
to heat. An important effect of heating plate tempera-
345ture on residual moisture content was observed. This
positive effect was amplified as the heating plate
Table 1. Operation variables during spray drying and freeze drying of human milk.
Spray drying
Initial milk
total solids (%) T
inlet
(°C) Pressure (bar)
Flow rate
(mL/min) T
exit
(°C)
Final
moisture (%)
11.57 0.58
160 3 4 77.5 2.5 2.09 0.09
180 3 5 87.5 2.5 2.00 0.13
Freeze drying
Initial milk
total solids (%)
Heating plate
temperature (°C)
Freeze-drying
time (h)
Final
moisture (%) k (h
1
) N
11.21 0.41 20 9 2.65 005 0.115 1.52
30 8 3.05 0.15 0.133 1.53
40 6 1.75 0.075 0.170 1.64
4 J. CASTRO-ALBARRÁN ET AL.
temperature increased from 30 to 40°C (Fig. 1b). Times
to complete freeze drying can be extrapolated from
kinetic curves as 9, 8, and 6 h for 20, 30, and 40°C,
350 respectively, which corresponds approximately with
the times when the product temperature reached the
heating plate temperature.
Experimental data of moisture content decrease
as a function of time were fitted to Page’s model,
355Eq. (1). In Fig. 1b, Page’s model predictions are shown
together with experimental data. As can be observed,
this model predicted the freeze-drying kinetics in
human milk samples. The Page’s model fittings para-
meters are presented in Table 1. The rate constant (k)
360in the Page’s model involves the moisture diffusion
coefficient, which is temperature-dependent. Therefore,
as temperature increases, k increases. From Table 1, it
can be seen the rate constant (k) increased slightly
between 20 and 30°C, but as observed previously from
365the kinetic data, the rate constant was markedly
increased when using a 40°C heating plate temperature.
Table 1 also shows the final moisture content of human
milk powders freeze-dried at different heating plate
temperatures, which have a mean value of 2.48 0.61%.
370Effect of dehydration methods on IgA, IgG, and
IgM Content
Immunoglobulins concentrations were measured before
and after spray drying or freeze drying of human milk
and are presented in Table 2. Initial Ig concentrations
375were 215.80–262.68 µg/mL (IgA), 13.92–19.59 µg/mL
(IgG), and 21.95–22.48 µg/mL (IgM). It has to be noted
that each experiment for freeze drying or spray drying
was done with a different pool of homogenized
human milk, explaining the different initial Ig content
380values presented in Table 2. Human milk Ig contents
have been reported to vary depending on different
parameters such as the length of breastfeeding,
the breastfeeding stage, the time of the day when the
milk is extracted, and the geographic origin of the
385mothers.
[25,26]
Permanyer et al.
[10]
Q1reported IgA content
in mature human milk from 247 to 488 µg/mL and an
average of 13.47 µg/mL for IgG, whereas an IgM
concentration of 22.9 µg/mL was observed in the work
of Contador et al.
[25]
Therefore, our results on Ig
390concentration of human milk are in close agreement
with previous studies.
Based on the data presented in Table 2, graphs on
Ig retention were constructed (Figs. 2a and 2b for
spray drying and freeze drying, respectively, at differ-
395ent operation conditions). Spray-drying produced
Figure 1. Freeze-drying of human milk, (a) temperature profile
during freeze drying at 20, 30, and 40°C heating plate tempera-
tures (dotted lines represent product temperature while solid
lines, heating plate temperature), and (b) freeze-drying kinetic
curves of human milk at varying heating plate temperatures
(20, 30, and !40°C).
Table 2. IgA, IgG, and IgM contents of human milk powder spray dried or freeze dried at different operation conditions.
Temperature (°C) IgA (µg/mL) IgG (µg/mL) IgM (µg/mL)
Spray drying Initial 215.80 6.84 13.92 0.80 21.95 5.15
160 (4 mL/min) 77.76 5.00 13.06 0.17 14.62 2.35
180 (5 mL/min) 83.20 1.22 12.26 0.55 16.10 3.39
Freeze drying Initial 262.68 56.40 19.59 0.17 22.48 5.84
20 199.48 33.91 15.36 0.33 19.57 6.28
30 200.62 4.75 16.00 0.70 18.84 5.12
40 144.72 7.00 15.38 0.20 18.40 8.40
Mean standard deviation (n ¼2).
DRYING TECHNOLOGY 5
human milk powders have good retention of IgG
(higher than 88%) and IgM (higher than 67%)
(Fig. 2a). However, only 38% of IgA could be pre-
served after spray dying. Please note from Table 1, that
400 both spray-dried powders have low residual moisture
contents (2%).
For freeze drying, only the highest heating plate
temperature used in this study (40°C) caused a low
retention of immunoglobulin IgA (55%). The other
405 conditions retained over 76% IgA and 80% IgG and
IgM. The reason why different Ig are retained
differently by the same process conditions is unknown
to us. It has been previously reported that IgA is stable
up to 56°C but heat-labile at 62.5°C
[8]
and that tempera-
410 ture rather than process time is a critical parameter in
keeping IgA content.
[9]
The lower retention of IgA at 40°C could be
explained by a longer exposure of the milk sample to
the heating plate temperature (Fig. 1a) as well as its
415 lower residual moisture content (Table 1). In freeze
drying, the lowest moisture content possible is not
necessarily the best optimal condition to preserve pro-
teins (i.e., Ig) since chemical and physical degradation
such as deamination, oxidation, and aggregation may
420 occur
[27]
and accelerate at very low water contents.
Nonparametric ANOVA performed on the Ig
concentrations data before and after freeze-drying/
spray-drying treatments failed to reveal evidence for
significant differences. However, Dunn’s multiple
425comparisons test suggested for spray drying at 160°C
a trend toward a significant reduction of IgA
(p ¼0.0651) and IgM (p ¼0.0911) as well as for IgG
at 180°C (p ¼0.0651), while for freeze drying such
a trend was observed for IgA concentrations between
430Initial vs 40°C treatment only (p ¼0.0605).
The present results indicated that IgA is the most
sensitive Ig during processing human milk by drying.
Reduced moisture contents obtained under specific
operating conditions as well as higher temperatures
435could be the causes of lower retention of IgA during
freeze drying and spray drying. Taking into account that
IgA is believed to be the most important Ig in human
milk,
[2]
the comparison of both dehydration methods
leads to the conclusion that freeze drying at 30°C is
440a particularly promising method to preserve human
milk. In addition, a heating plate of 30°C throughout the
whole sublimation process can accelerate the kinetics
(only 8 h processing time) with good overall immunoglob-
ulin retention (IgA 76.37 µg/mL 1.81%, IgG μg/mL
44581.65 3.61%, and IgM 83.80 µg/mL 22.75%).
Sorption isotherms
The sorption equilibrium isotherms of freeze-dried and
spray-dried human milk powders at 20°C are shown in
Fig. 3. Both curves showed a type-II sigmoid sorption
450form.
[28]
The sorption curves found in this work
showed a progressive increase in water content until
a
w
¼0.6, then the slope of the curve increases until
a
w
¼0.9. Soteras et al.
[29]
found similar behavior when
studying adsorption isotherms at 25°C of whole cow
Figure 2. Human milk IgA, IgG, and IgM retention after
(a) spray-drying at ( ) 160°C and ( ) 180°C and (b) freeze-drying
at heating plate temperatures of ( ) 20°C, ( ) 30°C, and ( )
40°C.
Figure 3. Sorption isotherms of human milk freeze-dried or
spray-dried powders.
6 J. CASTRO-ALBARRÁN ET AL.
455 milk samples, dried in an oven. In our study, differences
in moisture sorption by spray-dried or freeze-dried
human milk samples were not significant.
Human milk freeze-dried at 30°C heating plate
temperature for 8 h presents 3.05% moisture content
460 in wet basis (i.e., 0.0315 kg water/kg dry solids in dry
basis) (Table 1). From Fig. 3, it can be observed that
at this moisture content, 0.2 is the corresponding
approximate water activity at ambient temperature.
Thus, storage of this powder at ambient temperature
465 would require a relative humidity lower than 20%,
or a moisture barrier packaging, to avoid rehydration
of the powder during storage.
The fitted constants of the GAB equation (Eq. (2))
for human milk are X
m
¼0.0596 kg water/kg dry solids,
470 C ¼4.0241 and K ¼0.7423. These nonlinear regression
constants have a standard error estimated to 0.0093.
[30]
Predictions of GAB equation with fitted parameters are
also presented in Fig. 3 together with the experimental
data. These results showed a good agreement between
475 experimental and predicted data. The X
m
parameter
is an important sorption value representing the water
molecular primary layer. Determining the moisture
content for the maximum shelf stability of a dehydrated
product involves the determination of the sorption
480 isotherm and the calculation of the value of X
m
in Eq. (2). The estimated X
m
parameter values from
our data are in agreement with literature values
determined by Garcia-Alvarado et al.
[31]
and Lim et al.,
[32]
ranging from 0.053 to 0.174 kg water/kg dry solids.
485 Glass transition temperature
Figure 4 shows a representative DSC thermograms
obtained for human milk powders processed by freeze
drying at different heating plates temperatures (Fig. 6a
Q2 )
and by spray drying at different air inlet temperatures
490 (Fig. 6bQ3 ). Since the intensity of the thermograms is
solely linked to the mass of the sample and the water
content, the comparison of these curves is done by
matching the temperatures where peaks and step change
in the heat flow appear. The thermograms for freeze-
495 dried and spray-dried human milk powder samples
were similar, presenting three main peaks at 5, 18,
and 33°C, which may correspond to the melting of the
main fatty acids in human milk. Also, glass transitions
are observed in a range of 65–75°C, which corresponds
500 to the glass transition of lactose, the main carbohydrate
present in human milk, at 2–3% water content.
[33]
From curves exampled in Fig. 4, glass transition
temperatures for human milk were estimated to be
63.90 7.57°C and 69.11 5.55°C for spray drying at
505 160 and 180°C inlet air temperature, respectively.
For freeze-dried human milk powders, T
g
values were
69.07 1.29°C, 72.09 5.29°C, and 73.12 0.45°C
at 20, 30, and 40°C heating plate temperatures, respect-
ively. Glass transition temperatures of human milk
510powders were above 60°C, which indicates a good
thermal stability at ambient temperature if the powder
is packaged with moisture-barrier materials. Similar
T
g
results of 61 and 62°C for whole and skim milk,
respectively, were found for cow milk powders.
[34–36]
515Conclusion
The results obtained from this study on dehydration
methods and Ig retention in human milk suggested that
IgA is particularly sensitive and specifically lost during
drying processing. Our data further support the use
520of freeze drying at 30°C heating plate temperature to
generate human milk powders, which can accelerate
the process compared to lower processing temperatures
and minimize the loss of Ig with good retention of
IgA (76.37 1.81%), IgG (81.65 3.61%), and IgM
525(83.80 22.75%). From sorption and glass transition
results, storage of this powder at ambient temperature
Figure 4. Heat flow curves as a function of scanning tempera-
ture (a) freeze-drying and (b) spray-drying. The glass transition is
marked with light circles.
DRYING TECHNOLOGY 7
of freeze-dried powders would be possible as long as the
milk powder is packaged in moisture-barrier materials.
Further research studies based on immunoglobulin
530 structure are recommended in order to explain the dif-
ferential impact of the same drying conditions on Ig
retention values.
Acknowledgments
535 We would like to acknowledge the fruitful discussions and
moral support to this project from nutritionists Marie-Ève
Paradis (INAF, Université Laval), and Julie Lauzière and
Huguette Turgeon-O’Brien (School of Nutrition, Université
Laval).
540 Funding
The research group in the present work would like to thank
the Ministère des Relations Internationales, de la Francopho-
nie et du Commerce Extérieur (MRIFCE), from Québec
(Canada), the Institute for Nutrition and Functional Foods
545 (INAF, Université Laval), and the Consejo Nacional de
Ciencia y Tecnología (CONACYT, México) for their financial
support to this project.
References
[1] Newman, J. How breast milk protects newborns.
550 Scientific American 1995, 273(6), 76–79.
[2] Marshall, J.E.; Raynor, M.D. Myles Textbook for
Midwives; Elsevier Health Sciences: Edinburgh, 2014.
[3] Goldman, A.S.; Garza, C.; Nichols, B.L.; Goldblum,
R.M. Immunologic factors in human milk during
555 the first year of lactation. The Journal of Pediatrics
1982, 100(4), 563–567.
[4] Eidelman, A.I.; Schanler, R.J.; Johnston, M.; Landers, S.;
Noble, L.; Szucs, K.; Viehmann, L. Breastfeeding and the
use of human milk. Pediatrics 2012, 129(3), e827–e841.
560 [5] Ford, J.E.; Law, B.A.; Marshall, V.M.; Reiter, B. Influence
of the heat treatment of human milk on some of its
protective constituents. The Journal of Pediatrics 1977,
90(1), 29–35.
[6] Permanyer, M.; Castellote, C.; Ramirez-Santana, C.;
565 Audi, C.; Perez-Cano, F.J.; Castell, M.; Lopez-Sabater,
M.C.; Franch, A. Maintenance of breast milk immuno-
globulin A after high-pressure processing. Journal of
Dairy Science 2010, 93(3), 877–883.
[7] Evans, T.J.; Ryley, H.C.; Neale, L.M.; Dodge, J.A.;
570 Lewarne, V.M. Effect of storage and heat on antimicro-
bial proteins in human milk. Archives of Diseases in
Childhood 1978, 53(3), 239–241.
[8] Ogundele, M.O. Techniques for the storage of human
breast milk: Implications for anti-microbial functions
575 and safety of stored milk. European Journal of Pediatrics
2000, 159(11), 793–797.
[9] Czank, C.; Prime, D.K.; Hartmann, B.; Simmer, K.; Hart-
mann, P.E. Retention of the immunological proteins of
pasteurized human milk in relation to pasteurizer design
580 and practice. Pediatric Research 2009, 66(4), 374–379.
[10] Friend, B.A.; Shahani, K.M.; Long, C.A.; Agel, E.N.
Evaluation of freeze-drying, pasteurization, high-
temperature heating and storage on selected enzymes,
B-vitamins and lipids of mature human milk. Journal
585of Food Protectection 1983, 46(4), 330–334.
[11] Ramirez-Santana, C.; Perez-Cano, F.J.; Audi, C.; Castell,
M.; Moretones, M.G.; Lopez-Sabater, M.C.; Castellote,
C.; Franch, A. Effects of cooling and freezing storage
on the stability of bioactive factors in human colostrum.
590Journal of Dairy Science 2012, 95(5), 2319–2325.
[12] Lozano, B.; Castellote, A.I.; Montes, R.; Lopez-Sabater,
M.C. Vitamins, fatty acids, and antioxidant capacity
stability during storage of freeze-dried human milk.
International Journal of Food Sciences and Nutrition
5952014, 65(6), 703–707.
[13] Birchal, V.S.; Passos, M.L.; Wildhagen, G.R.; Mujumdar,
A.S. Effect of spray-dryer operating variables on the
whole milk powder quality. Drying Technology 2005,
23(3), 611–636.
600[14] Ratti, C. Hot air and freeze-drying of high-value foods:
A review. Journal of Food Engineering 2001, 49(4), 311–319.
[15] Roberts, J.S.; Kidd, D.R.; Padilla-Zakour, O. Dryings
kinetics of grape seeds. Journal of Food Engineering
2008, 89(4), 460–465.
605[16] Simal, S.; Femenia, A.; Garau, M.C.; Rosselló, C. Use of
exponential, page’s and diffusional models to simulate
the drying kinetics of kiwi fruit. Journal of Food
Engineering 2005, 66(3), 323–328.
[17] McMinn, W.A.M. Thin-layer modeling of the
610convective, microwave, microwave-convective and
microwave-vacuum drying of lactose powder. Journal
of Food Engineering 2006, 72(2), 113–123.
[18] St-Amour, I.; Laroche, A.; Bazin, R.; Lemieux, R.
Activation of cryptic IgG reactive with BAFF, amyloid
615beta peptide and GM-CSF during the industrial fraction-
ation of human plasma into therapeutic intravenous
immunoglobulins. Clinical Immunology 2009, 133(1),
52–60.
[19] Ratti, C.; Araya-Farias, M.; Mendez-Lagunas, L.; Makh-
620louf, J. Drying of garlic (Allium sativum) and its effect
on allicin retention. Drying Technology 2007, 25(2),
349–356.
[20] Santanu, B.; Shivhare, U.S.; Mujumdar, A.S. Moisture
adsorption isotherms and glass transition temperature of
625xanthan gum. Drying Technology 2007, 25(9), 1581–1586.
[21] Sá, M.M.; Figueiredo, A.M.; Sereno, A.M. Glass transi-
tions and state diagrams for fresh and processed apple.
Thermochimica Acta 1999, 329(1), 31–38.
[22] Lawrence, R.A. Storage of human milk and the influence
630of procedures on immunological components of human
milk. Acta Paediatrica 1999, 88, 14–18.
[23] Picciano, M.F.; Guthrie, H.A. Copper, iron, and zinc
contents of mature human milk. American Journal
of Clinical Nutrition 1976, 29(3), 242–254.
635[24] Sagara, Y.; Ichiba, J.I. Measurement of transport properties
for the dried layer of coffee solution undergoing freeze
drying. Drying Technology 1994, 12(5), 1081–1103.
[25] Contador, R.; Delgado-Adámez, J.; Delgado, F.J.; Cava,
R.; Ramírez, R. Effect of thermal pasteurisation or high
640pressure processing on immunoglobulin and leukocyte
contents of human milk. International Dairy Journal
2013, 32(1), 1–5.
8 J. CASTRO-ALBARRÁN ET AL.
[26] Yuen, J.W.; Loke, A.Y.; Gohel, M.D. Nutritional and
immunological characteristics of fresh and refrigerated
645 stored human milk in Hong Kong: A pilot study. Clinica
Chimica Acta 2012, 413(19), 1549–1554.
[27] Chang, L.; Pikal, M.J. Mechanisms of protein
stabilization in the solid state. Journal of Pharmaceutical
Sciences 2009, 98(9), 2886–2908.
650 [28] Rizvi, S.S. Thermodynamic properties of foods in dehy-
dration. In Engineering Properties of Foods; Rao, M.A.,
Rizvi, S.S., Datta, A.K., Eds.; CRC Press Inc.: Boca Raton,
FL, USA, 2005; 239–325.
[29] Soteras, E.M.; Gil, J.; Yacanto, P.; Muratona, S.; Abaca,
655 C.; Sustersic, M.G. Water adsorption and desorption iso-
therms of milk powder: II Whole milk. Avances en Cien-
cias e Ingeniería 2014, 5(1), 57–66.
[30] Sigmaplot 11.0. Analyse and Graph Your Data with
Unparalleled Ease and Precision; Systat Software Inc.:
660 San Jose, CA, USA, 2008.
[31] Garcia-Alvarado, M.A.; De la Cruz-Medina, J.;
Waliszewski-Kubiak, K.N.; Salgado-Cervantes, M.A.
Statistical analysis of the GAB and Henderson equations
for sorption isotherms of foods. Drying Technology 1995,
66513(8–9), 2141–2152.
[32] Talla, A.; Jannot, Y.; Nkeng, G.E.; Puiggali, J.-R.
Experimental determination and modeling of sorption
isotherms of tropical fruits: Banana, mango, and
pineapple. Drying Technology 2005, 23(7), 1477–1498.
670[33] Roos, Y.H. Solid and liquid states of lactose. In Advanced
Dairy Chemistry, Vol. 3; McSweeney, P.L.H., Fox, P.F.,
Eds.; Springer LLC.: The Netherlands, 2009; 17–33.
[34] Ozmen, L.; Langrish, T.A.G. Comparison of glass tran-
sition temperature and sticky point temperature for skim
675milk powder. Drying Technology 2002, 20(6), 1177–1192.
[35] Fernández, E.; Schebor, C.; Chirife, J. Glass transition
temperature of regular and lactose hydrolyzed milk pow-
ders. LWT-Food Science Technology 2003, 36(5), 547–551.
[36] Jouppila, K.; Kansikas, J.; Roos, Y.H. Glass transition,
680water plasticization, and lactose crystallization in
skim milk powder. Journal of Dairy Science 1997,
80(12), 3152–3160.
DRYING TECHNOLOGY 9
... Castro-Albarran et al. [15] dried human milk using spray drying and freeze-drying to study the retention of immunoglobulins, and they reported that freeze-drying at 30°C showed maximum retention. Santos et al. [81] reviewed the use of spray drying and freeze-drying in the manufacture of yogurt powder. ...
Full-text available
Conference Paper
Polisiklik aromatik hidrokarbonlar (PAH’lar) gıdalara uygulanan ısıl işlemler sonucu meydana gelen oluşumu istenmeyen bileşiklerdir. Bu kirleticiler sağlığı olumsuz etkileyen çoğunlukla mutajenik ve kanserojenik olup, bu bileşiklere maruz kalmanın en yaygın yolu diyet alımı yoluyla olması sebebiyle gıdalardaki miktarlarının doğru bir şekilde tespit edilmesi gerekmektedir. Gıda maddelerinin heterojen yapısı ve de çok düşük konsantrasyonda bulunması PAH bileşiklerinin analizini zorlaştırıcı unsurlarıdır. Gıdalarda PAH'ların analizi, analitlerin maksimum seviyede geri kazanımı ve beraberindeki istenmeyen karışımları minimum seviyede tutmak gibi çeşitli analitik parametreler nedeniyle komplike bir analizdir. Gıdalarda PAH bileşiklerini belirlemek için, PAH'ların ekstraksiyonu, ayrılması ve tanımlanması prosedürleri mevcuttur. Bu noktadan hareketle kullanılan yöntemin analit kaybı, fazla miktarda çözücü kullanımı, çevre dostu olmaması, süre gibi kısıtlamaları azaltılması gereken önemli hususlarıdır. Bu amaçla gıdalarda PAH analizleri için daha hassas ve daha hızlı olan elektrokimyasal, ELISA gibi yeni teknikler üzerinde çalışmalar yürütülmektedir. Son yıllarda gıdalarda PAH'ların miktar tayini için yeşil teknoloji prensibine dayalı QuEChERS metodolojisi, yeşil ekstraksiyon tekniklerinin (süper kritik sıvı ekstraksiyonu, manyetik katı-faz ektraksiyonu, mikro ektraksiyon vb.) kullanımlarına odaklanılmaktadır. Bu bildiride, gıdalarda polisiklik aromatik hidrokarbonlar (PAH'lar) tespiti için mevcut temel ve yenilikçi prosedürlere ilişkin güncel bilgilere genel bir bakış sağlamak amaçlanmaktadır.
Conference Paper
GIDALARDA POLİSİKLİK AROMATİK HİDROKARBON (PAH) BİLEŞİKLERİNİN TAYİN YÖNTEMLERİ
Presentation
GIDALARDA POLİSİKLİK AROMATİK HİDROKARBON (PAH) BİLEŞİKLERİNİN TAYİN YÖNTEMLERİ
Full-text available
Article
Kurutma gıdaların raf ömrünü uzatmak için kullanılan en eski yöntemdir. Püskürtmeli kurutmanın temel fikri, çözücünün buharlaştırılmasıyla bir sıvı beslemesinden yüksek oranda dağılmış tozların üretilmesidir. Bu, ısıtılmış bir gazın, bir kap içinde (kurutma haznesi) ideal olarak eşit büyüklükteki, yüksek yüzey-kütle oranı damlacıkları atomize (püskürtülmüş) bir akışkan ile karıştırılmasıyla elde edilir; bu da çözücünün, doğrudan temas yoluyla muntazam ve hızlı bir şekilde buharlaşmasına neden olur. Püskürtmeli kurutma gıda sanayisinde yaygın kullanılmaktadır. Bunun nedeni gıdaların ısıya duyarlı olmaları ve tüketicilerin toz ürünlere olan ilgisidir. Süt tozu, peynir altı suyu proteini, kahve, çay ekstraktları, bebek mamaları, nişasta, enzimler, mikroorganizmalar, mayalar püskürterek kurutma ile üretilen ürünlerden bazılarıdır. Püskürterek kurutulmuş gıdaların kalitesi, çalışma parametrelerine oldukça bağlıdır. Daha iyi duyusal, besleyici özelliklere ve daha iyi proses verimine sahip ürünler elde etmek için ürün özelliklerine göre proses optimizasyonu sağlanması gerekir. Optimum ürün verimi için püskürterek kurutma yöntemi, birçok yöntemle birlikte kullanılabilir. Gıda endüstrisinde yaygın olarak kullanılan yöntemlerden biri olan püskürtmeli kurutucular üstün performanslı kurutma sağlamasına karşın aktif materyali koruyan bir polimer matris içerisinde hapsedilmesi nedeniyle, günümüzde bu yöntem mikroenkapsülasyon tekniği olarak kabul edilmektedir. Bu derlemede, genel olarak püskürtmeli kurutucunun çalışma prensibi, gıda sanayinde kullanım alanları ve değiştirilmiş parametrelerde optimum ürün elde ile ilgili çalışmalar sunulmuştur.
Article
The effects of high-pressure processing (HPP; 300, 400, 500 and 600 MPa for 5 min) compared to Holder pasteurization treatments on the macronutrients, acidity in Dornic, total coliforms, fatty acids (FA) composition, and the triacylglycerols (TAG) profile of mature human milk (HM) were evaluated. The results showed that both processes eliminated the microorganisms present, and the concentration of macronutrients and Dornic acidity did not show significant differences in processes. A total of 34 FAs were identified by gas chromatography with flame ionization detector, with palmitic and oleic acids having the highest concentrations. Regarding the TAG profile determined by direct infusion by electrospray ionization mass spectrometry, TAG PLO (P: palmitic acid; L: linoleic acid; and O: oleic acid) was the one with the highest estimated concentration (6.52 to 7.27%). The evaluation of hierarchical clustering analysis results suggests that processing with lower pressures was more beneficial for HM due to the similarity between the intensities of the TAGs identified in each sample and the control HM sample. Besides, the results obtained on the evaluated components suggested that HPP could be a promising alternative to HoP applied in human milk banks since it maintained the characteristics of HM and is faster than HoP.
Full-text available
Article
Human milk is important for modulating the newborn’s immune and antioxidant response. The applicability of lyophilization and spray-drying processes in human milk donated to human milk banks are alternatives for storage and distribution when breastfeeding is not possible. Therefore, the aim of this work was to detect and quantify cytokines (IFN-ɣ, IL-4, IL-5, IL-10, IL-13, IL-17 A/F, IL-21, and IL-22) and to evaluate the antioxidant capacity in different phases of donated HM submitted to lyophilization and spray-drying processes. The HM donated in natura was submitted to pasteurization, lyophilization and spray-drying processes, then cytokine concentrations were measured using Luminex technology and antioxidant capacity of the superoxide dismutase and catalase enzymes and reduced glutathione levels in vitro. Cytokine profiles, catalase, superoxide dismutase and reduced glutathione profiles were preserved after processing of lyophilization and spray-drying in all phases of donated human milk.
Article
The nutritional and microbiological quality of human milk (HM) before and after spray drying was compared. The results showed that the atomisation of untreated-HM did not significantly change protein, lactose and fat content. The immunoglobulins showed a retention from 70 to 82% for IgA, IgG and IgM. γ-Irradiation (3, 5 and 10 kGy) of frozen and powdered milk as well as Holder pasteurisation (HoP; 62.5 °C for 30 min) of liquid milk were used to decontaminate milk. A dose of 5 kGy irradiation resulted in 99.7% destruction of the total aerobic flora in the powdered milk and in the frozen milk, while it was 95.1% for HoP-treated milk. Macronutrients and bioactive compounds (lysozyme and amylase) present in atomised HM were not affected by γ-irradiation even at a dose of 10 kGy. Despite a slight increase in malondialdehyde, treatment with irradiation at 10 kGy did not alter the antioxidant potential.
Chapter
Human milk is a complex biological fluid which contains the major macronutrients present in all mammalian milks (proteins, comprising caseins and whey proteins, lipids, carbohydrates, minerals, vitamins and enzymes, as well as a complex metabolome) but at levels which differ in significant ways, both qualitatively and quantitatively, from bovine milk. In recent years, detailed studies, undertaken with a view both to understanding infant nutrition and for development of infant formulas that best batch human milk, have revealed the complexity of human milk, in particular in terms of fatty acid, protein and oligosaccharide profiles. Human milk also has a complex and variable microflora, and increasing demand for preserved human milk has led to the exploration of a number of approaches to ensure its safety and stability. In this article, the composition of human milk, properties of its main constituents, and factors affecting their level are reviewed, as well as key aspects of the human milk microbiome and strategies used for the physical and microbiological stabilization of human milk for storage.
Article
The effects of freeze-drying, pasteurization, high-temperature heating and storage on key enzymes, B-vitamins and lipids of pooled mature human milk were determined. Freeze-drying significantly decreased (P<0.05) the activity of lactoperoxidase and lysozyme but had no effect on the lipase or protease of pooled human milk. Storage after freeze-drying destroyed lactoperoxidase activity but had no apparent effect on the other enzymes. Heating at 62.5°C for 30 min or 75°C for 15 min significantly decreased (P<0.05) the activities of lactoperoxidase, lipase and protease. Lysozyme was inactivated significantly only by heating at 75°C. Storage at −25°C following pasteurization had no significant effect on enzyme activity. Biotin, niacin and pantothenic acid appeared to be quite stable and were not significantly altered by freeze-drying, heating and/or storage. Similarly, there were no significant differences in lipid components following processing and storage.
Article
Breastfeeding and human milk are the normative standards for infant feeding and nutrition. Given the documented short-and long-term medical and neurodevelopmental advantages of breastfeeding, infant nutrition should be considered a public health issue and not only a lifestyle choice. The American Academy of Pediatrics reaffirms its recommendation of exclusive breastfeeding for about 6 months, followed by continued breastfeeding as complementary foods are introduced, with continuation of breastfeeding for 1 year or longer as mutually desired by mother and infant. Medical contraindications to breastfeeding are rare. Infant growth should be monitored with the World Health Organization (WHO) Growth Curve Standards to avoid mislabeling infants as underweight or failing to thrive. Hospital routines to encourage and support the initiation and sustaining of exclusive breastfeeding should be based on the American Academy of Pediatrics-endorsed WHO/UNICEF "Ten Steps to Successful Breastfeeding." National strategies supported by the US Surgeon General's Call to Action, the Centers for Disease Control and Prevention, and The Joint Commission are involved to facilitate breastfeeding practices in US hospitals and communities. Pediatricians play a critical role in their practices and communities as advocates of breastfeeding and thus should be knowledgeable about the health risks of not breastfeeding, the economic benefits to society of breastfeeding, and the techniques for managing and supporting the breastfeeding dyad. The "Business Case for Breastfeeding" details how mothers can maintain lactation in the workplace and the benefits to employers who facilitate this practice. Pediatrics 2012; 129:e827-e841
Article
Abstract Although freezing is the most common method used to preserve human milk, nutritional and immunological components may be lost during storage. Freeze-drying could increase the shelf life of human milk, while preserving its original characteristics. Seventy-two samples of freeze-dried human milk were stored for different periods of time, up to a maximum of 3 months, at 4 °C or 40 °C. Vitamin C, tocopherols, antioxidant capacity, and fatty acids composition were analyzed. A new HILIC-UHPLC method improving vitamin C determination was also validated. Ascorbic acid and total vitamin C concentrations significantly decreased at both temperatures, while antioxidant capacity only decreased at 40 °C. Fatty acids composition and both γ-tocopherol and δ-tocopherol contents remained unaltered. The stability after storage of freeze-dried milk was higher than that reported for frozen or fresh milk indicating that freeze-drying is a promising option to improve the preservation of human milk in banks.
Article
High pressure processing (HPP) could be an alternative to Holder Pasteurisation (HoP, 62.5 °C for 30 min) for breast milk preservation in human milk banks. The effect of HPP (at 400 or 600 MPa for 3 or 6 min) was compared with that of HoP. The effect of processing on the immune cells (leukocyte content) and immunoglobulins (IgM, IgA and IgG) was evaluated. Treatment at 400 MPa (for 3 or 6 min) maintained the original levels of immunoglobulins (IgM, IgA and IgG) of breast milk better than HoP. In contrast, at 600 MPa the reduction of the original immunoglobulins levels was similar to that following HoP. HPP and HoP destroyed most leukocytes in breast milk; the percentage of retention of leukocytes after processing was between 4 and 14%. Overall, HPP could be a suitable alternative for the preservation of immunoglobulins in human milk.
Article
Differential scanning calorimetry (DSC) was used to measure phase transitions in samples of Golden Delicious apples after freeze-drying and osmotic drying in a sucrose solution. From DSC traces, glass transition (Tg) and melting (Tm) temperatures were obtained and used to plot the state diagrams for the two types of samples. The Gordon–Taylor equation was able to predict the dependence of the glass transition temperature on moisture content. Before calorimetric analysis, dehydrated samples were equilibrated under a wide range of different relative humidities (aw 0.12–0.93) and sorption isotherms determined. Experimental sorption isotherms agreed with previous results reported in the literature.
Article
Lactose-water samples were dried under selected convective, microwave, microwave-convective and microwave-vacuum conditions in an experimental system (2.45GHz, 90W). Irrespective of the drying technique, a typical drying profile, with a constant drying rate stage followed by two falling rate periods, was exhibited. The magnitude of the drying rate, however, was dependent on the convective air temperature and velocity, and system pressure. The experimental moisture loss data were fitted to selected semi-theoretical and empirical thin-layer drying equations. The mathematical models were compared according to three statistical parameters, i.e. reduced chi-square, root mean square error and residual sum of squares. The drying characteristics were satisfactorily described by the Page, Logarithmic, Chavez-Mendez et al. and Midilli et al. models, with the latter providing the best representation of the experimental data.
Article
Wall deposition of particles in spray dryers is a key processing problem, and information about the glass transition temperature of the amorphous material that arises from spray drying can be used to guide the selection of operating conditions that may minimise wall deposition. The glass transition temperatures for skim milk powder with various moisture contents were determined using Differential Scanning Calorimetry (DSC), and a repeatable glass transition temperature diagram was established from these results. The glass transition temperature decreased as the moisture content increased, as expected (low moisture content 1.65 g/100 g of dry powder, glass transition temperature 87.7°C; high moisture content 4.52 g/100 g of dry powder, glass transition temperature 46.7°C). The glass transition temperature was found to be virtually the same as the sticky-point temperature measured using a thermo-mechanical test. The difference is essentially due to the difference between doing a mechanical test for viscosity (sticky-point) and a phase transition measurement (DSC).
Article
This work aims at identifying the effects of the main operational spray-dryer variables on the milk powder quality. Experiments have been performed in a pilot spray-dryer following the full-factorial design technique to provide data and correlations that predict the whole powder properties as function of the main operational variables of the spray-dryer. The emulsion feed flow rate, the atomization rotation and the inlet air temperature have been chosen as the independent variables while the residual moisture content, the tapped bulk density, the cohesion force enhancement between particles as well as size distribution of agglomerate and its morphology are the response variables that quantify the powder quality. Correlations obtained are analyzed and incorporated into a mathematical model previously developed for simulating the spray-drying of whole milk emulsion.