Effects of physical and chemical properties on the dissolution of sea salt

Science & Technology Development Journal – Engineering and Technology, 4(2):1009-1018
Open Access Full Text Article Research article
Department of Food Technology, Ho Chi
Minh City University of Technology,
VNU-HCM, Ho Chi Minh City, Vietnam
Correspondence
Nguyen Hoang Dzung, Department of
Food Technology, Ho Chi Minh City
University of Technology, VNU-HCM, Ho
Chi Minh City, Vietnam
Email: dzung@hcmut.edu.vn
History
 Received: 25-3-2021
 Accepted: 27-5-2021
 Published: 03-6-2021
DOI : 10.32508/stdjet.v4i2.822
Copyright
© VNU-HCM Press. This is an open-
access article distributed under the
terms of the Creative Commons
Attribution 4.0 International license.
Effects of physical and chemical properties on the dissolution of
sea salt
Nguyen Huu Lan, Nguyen Thi Ngoc Huong, PhamHuu Thinh, Lai Quoc Dat, Nguyen Hoang Dzung*
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ABSTRACT
Salt plays a crucial role in human health. However, excess use of NaCl in food products can be
harmful to health. One suggestion for this problem is optimization salt dissolution to increase the
content of salt ions in themouth. For this purpose, it is important to understand the solubility prop-
erties of salt crystals in saliva. The dissolving process is not only affected by the physical properties
but also by the chemical composition of the salt. This study compared the solubility of four com-
mercial grain salts in four regions in Vietnam (Bac Lieu, Thanh Hoa, Sa Huynh, Vung Tau), one flower
salt in Sa Huynh and a control sample with two particle sizes 1 - 2mm and 2 - 3mm in a Saliva Artifi-
cial Gal – Fovet solution (SAGF). Dissolutionwas determinedby analyzingmicroscopic images taken
by the time and analysis by Bayesian and Partial Least Squared methods. The research evaluated
the influence of physical properties (area, Feret's diameter, circularity, aspect ratio and solidity) and
chemical compositions (sodium, potassium, magnesium, calcium and moisture content) on the
dissolving process. Salt samples showed significant differences in physical and chemical properties
by region. Morphological parameters are affected by conditions of salt crystallization that indicated
through region of origin. Dissolution is evaluated through solubility coefficient, Sa Huynh flower
salt and control salt have the highest solubility coefficient, simultaneously, it is also the smallest
value of roundness and surface index. The projected area, magnesium and sodium content are
the factors which strongly affecting on dissolution of salt samples. These results demonstrated the
possibility to exploit these factors to adjust the solubility of salt as well as the perceived salinity over
time.
Key words: salt, artificial saliva, dissolution, physico-chemical properties, Bayesian
INTRODUCTION
Sodium is an essential nutrient for maintaining blood
plasma, acid-base balance, transmit nerve impulses
and participate in necessary functions for human
cells1,2. Sodium is found naturally in many foods,
such as milk, meat, and seafood. Besides, in some
processed foods, snacks, spices (sodium glutamate)
are also sources of sodium for the body3. Nowadays,
most people are consuming toomuch salt, averaging 9
to 12 g per day, which is approximately twice themax-
imum recommended intake (WorldHealthOrganiza-
tion, 2014). High sodium in the diet can lead to high
blood pressure, cardiovascular disease, and stroke4,5.
It can also cause calcium losses, some of which may
be pulled from bone6. Therefore, it is necessary to de-
velop strategies that reduce the level of sodium intake
while maintaining the salt taste perception in prod-
ucts.
There are many different suggestions for increasing
salt salinity, such as using salt alternatives or alter-
ing the chemical composition by adding a salt addi-
tive, thereby reducing sodium intake body7. Previous
studies showed that from 70 to 95% sodium (or NaCl
salt) can remain in food matrix after a consumer has
swallowed it8,9. For dry foods that are salted directly
to the surface, a significant amount of sodium can be
swallowed completely without the consumer perceiv-
ing the salty taste. The difference in salty taste is actu-
ally caused by the dissolution of the salt in the mouth
by saliva. In it, saliva acts as a solvent to distribute ions
in salt to the taste receptors on the tongue10. There-
fore, the dissolving process of salt will directly affect
the taste of salt in consumers.
Several methods have been developed to study salt
dissolution in the mouth e.g. installing ionic elec-
trodes in themouth. However, this technique has lim-
itations as the levels recorded may not fully reflect the
signal received by the taste buds. Furthermore, having
a string in the mouth can make chewing difficult11.
For this reason, in vitromethods have been developed
with easier implementation while still providing data
for screening12. These methods developed systems
that simulate conditions in the mouth and the use of
natural or artificial saliva in experiments in which salt
solubility is measured using a conductivity probe or
observation system. By this method, Vella, D. et al
Cite this article : Lan N H, Huong N T N, Thinh P H, Dat L Q, Dzung N H. Effects of physical and chemical
properties on thedissolutionof sea salt . Sci. Tech. Dev. J. – EngineeringandTechnology; 4(2):1009-1018.
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Science & Technology Development Journal – Engineering and Technology, 4(2):1009-1018
(2012) found a significant difference between the size
of salt particles and its close correlationwith the disso-
lution rate12. Beside that, Quilaqueo, M. et al (2015)
analyzed the dissolution rate of the salt by video mi-
croscopy images taken at different times. The results
revealed that the solubility rate of salt crystals in water
is higher than in artificial saliva and at higher temper-
atures. The increased surface area after fragmentati ... jected area parameters and max-
imum ferrite diameter also have a very clear positive
correlation. Most physical properties exhibit an in-
verse correlation with the potassium, magnesium and
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Science & Technology Development Journal – Engineering and Technology, 4(2):1009-1018
Table 4: R2 values of dissolution kinetic models
Sample Zero – order First – order Hixon Crowell
BL1 0.9781 0.9850 0.9893
BL2 0.9850 0.9904 0.9903
FS1 0.9562 0.9407 0.9884
FS2 0.9589 0.9535 0.9882
M1 0.9488 0.9433 0.9882
M2 0.9567 0.9428 0.9871
SH1 0.9760 0.9634 0.9869
SH2 0.9777 0.9861 0.9888
TH1 0.9752 0.9850 0.9902
TH2 0.9841 0.9877 0.9929
VT1 0.9797 0.9858 0.9868
VT2 0.9782 0.9821 0.9813
Figure 2: Projected area of salt samples under an optical microscope.
moisture content, while positively correlatingwith the
sodium and calcium content. This shows that during
natural crystallization, the purer the salt samples or
the higher their sodium content, the shape and size
of the salt also differ from those with lower sodium
content.
Salt samples also showed significant differences in
physical and chemical properties by region of produc-
tion. Sa Huynh flower salts and grain salt have high
levels of magnesium, potassium, and moisture, which
are very round. Salt from Vung Tau, Bac Lieu has
high sodium content, high roundness and surface in-
dex. Thanh Hoa salt showed a distinct difference in
the high calcium content.
Evaluate the influence of chemical and phys-
ical properties on the solubility of salt
To evaluate the effect of physical and chemical prop-
erties on the salt solubility, we conduct PLSR analy-
sis with solubility coefficient calculated from the re-
gression equation according to Bayesian method as
dependent variable and 5 physical parameters (Area,
Feret’s Diameter, Circularity, Aspect Ratio and Solid-
ity) as well as 5 chemical parameters (sodium, potas-
sium, magnesium, calcium and moisture content) as
independent variables. The result of RMSEP shows
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Science & Technology Development Journal – Engineering and Technology, 4(2):1009-1018
Table 5: Values from the regression equation following the Bayesianmethod of salt dissolution.
Sample Equivalence coefficient and 90% credible interval
Coefficient 2,5% Credible Interval 97,5% Credible Interval
BL1 0.010 0.005gh 0.009 0.005gh 0.010 0.005g
BL2 0.007 0.001i 0.006 0.001i 0.007 0.002h
FS1 0.038 0.006b 0.036 0.005b 0.039 0.007b
FS2 0.022 0.004d 0.021 0.004d 0.023 0.005d
M1 0.057 0.014a 0.054 0.013a 0.060 0.015a
M2 0.030 0.005c 0.029 0.005c 0.031 0.006c
SH1 0.017 0.003e 0.016 0.003e 0.017 0.003e
SH2 0.009 0.005gh 0.009 0.005gh 0.010 0.005g
TH1 0.012 0.004 f 0.012 0.004 f 0.012 0.004 f
TH2 0.010 0.004g 0.010 0.004g 0.010 0.005g
VT1 0.008 0.003hi 0.008 0.003hi 0.008 0.003gh
VT2 0.004 0.001 j 0.003 0.001 j 0.004 0.001i
Mean value (n = 60) standard deviation
Mean values expressed in different letters in each column indicate significant differences according to ANOVA analysis and LSD test (p <0.05).
Figure 3: Results of PCA correlation circle
that when evaluating combinations of factors, the
combination of 6 factors shows the best explanation
due to the lowest RMSEP value of the 10 combina-
tions is considered (Figure 4).
The analysis results of Variable Importance in Pro-
jected – VIP coefficients in the combination of 6 fac-
tors showed a clear influence of physical and chemical
properties which is presented in Table 6. The results
showed that the chemical composition has a great in-
fluence on the dissolution process when the sodium,
magnesium, potassium and calcium contents have the
highest VIP coefficients of the factors assessed. In
there, magnesium showed the highest influcence on
dissolution process. This is possible because mag-
nesium binds hydration water more tightly than cal-
cium, potassium, and sodium when dissolved, as a
result, the hydrated magnesium cation is difficult to
dehydrate. Among physical properties, Area parame-
ter has the highest coefficient, proving that this is an
important physical factor to consider when evaluat-
ing the solubility of salt. The results also show that
the moisture content also has a slight influence on the
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Science & Technology Development Journal – Engineering and Technology, 4(2):1009-1018
Figure 4: Root Mean Squared Error of Prediction graph of solubility coefficient.
dissolution process as the moisture’s VIP coefficient is
clearly different from the remaining physical param-
eters.
CONCLUSIONS
The results of the solubility of salt samples from 1 to 2
mm and 2 to 3 mm in size in artificial saliva solution
have shown that salt type, morphology and chemical
composition are influential factors affecting dissolv-
ing speed. Flower salts dissolvemuch faster than grain
salt. Projected particle area parameters and sodium,
potassium, calcium, and magnesium content are the
main physical and chemical factors that have great
correlation with the solubility process. The mineral
composition influences the taste perception of salt
(potassium is acidic and magnesium is bitter). There-
fore, the adjustment of salt crystallization in produc-
tion and the chemical composition change the sen-
sory properties of salt. This problem required further,
study on the effect of the physical and chemical fac-
tor on the salinity sensory properties of salt samples
of different origin.
LIST OF ABBREVIATIONS
AR: Aspect ratio
Ca: Calcium
Cir.: Circularity
Feret: Feret’s Diameter
Mg: Magnesium
PLS: Partial Least Squared
PLSR: Partial Least Squares Regression
PCA: Principle Components Analysis
K: Potassium
RMSEP: Root Mean Squared Error of Prediction
SAGF: Saliva Artificial Gal – Fovet solution
Na: Sodium
VIP : Variable Importance in Projected
COMPETING INTEREST
The authors declare that they have no competing in-
terestes.
AUTHORS’ CONTRIBUTION
Nguyen Huu Lan: The conception and design of the
study, Writing – original draft. Nguyen Thi Ngoc
Huong: Methodology, Data curation. Pham Huu
Thinh: Formal analysis. Lai Quoc Dat: Methodology,
Writing – review and editing. Nguyen Hoang Dzung:
Funding acquisition, Supervision, Validation.
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Tạp chí Phát triển Khoa học và Công nghệ –Kĩ thuật và Công nghệ , 4(2):1009-1018
Open Access Full Text Article Bài nghiên cứu
Bộ môn Công nghệ Thực phẩm, Đại học
Bách Khoa, ĐHQG-HCM, TP. Hồ Chí
Minh, Việt Nam
Liên hệ
Nguyễn Hoàng Dũng, Bộ môn Công nghệ
Thực phẩm, Đại học Bách Khoa, ĐHQG-HCM,
TP. Hồ Chí Minh, Việt Nam
Email: dzung@hcmut.edu.vn
Lịch sử
 Ngày nhận: 25-3-2021
 Ngày chấp nhận: 27-5-2021 
 Ngày đăng: 03-6-2021
DOI : 10.32508/stdjet.v4i2.822 
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© ĐHQG Tp.HCM. Đây là bài báo công bố
mở được phát hành theo các điều khoản của
the Creative Commons Attribution 4.0
International license.
Ảnh hưởng của các tính chất vật lý và hóa học đến quá trình hòa
tan củamuối biển
Nguyễn Hữu Lân, Nguyễn Thị Ngọc Hương, PhạmHữu Thịnh, Lại Quốc Đạt, Nguyễn Hoàng Dũng*
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TÓM TẮT
Muối có vai trò quan trọng trong sức khỏe con người. Tuy nhiên, sử dụng quá nhiều NaCl trong
các sản phẩm thực phẩm có thể ảnh hưởng xấu đến sức khỏe. Một hướng giải quyết vấn đề này
là cần tối ưu quá trình hòa tan muối để tăng hàm lượng các ion của muối trong miệng. Để thực
hiện điều đó, điều quan trọng là cần hiểu các đặc tính hòa tan của tinh thể muối trong nước bọt.
Quá trình hòa tan của muối không chỉ bị ảnh hưởng bởi các tính chất vật lý mà còn bị ảnh hưởng
bởi thành phần hóa học của muối. Nghiên cứu so sánh độ hòa tan của 4 mâũmuối thươngmại từ
4 khu vực ở Việt Nam (Bạc Liêu, Thanh Hóa, Sa Huỳnh, Vũng Tàu), 1 mâũ muối hoa từ Sa Huỳnh và
1 mâũ đối chứng ở 2 kích thước là 1 – 2 mm và 2 – 3 mm trong dung dịch nước bọt nhân tạo Gal
– Fovet (SAGF). Sự hòa tan được phân tích qua hình ảnh tinh thể dưới kính hiển vi theo thời gian,
xử lý kết quả bằng phương pháp Bayesian và bình phương tối thiểu từng phần (PLS). Nghiên cứu
đánh giá sự ảnh hưởng của các tính chất vật lý (diện tích hình chiếu, đường kính Feret, độ tròn, tỷ
lệ khung hình và chỉ số bề mặt) và các tính chất hóa học (Natri, Kali, Magie, Canxi và độ ẩm) đến
quá trình hòa tan. Các mâũ muối cho thấy sự khác nhau đáng kể về tính chất vật lý và hóa học
theo khu vực địa lý. Các thông số hình học bị ảnh hưởng bởi điều kiện kết tinh, điều này thể hiện
qua nguồn gốc các mâũ. Độ hòa tan được đánh giá qua hệ số hòa tan, muối hoa Sa Huỳnh vàmâũ
đối chứng có hệ số hòa tan cao nhất, đồng thời, cũng có giá trị độ tròn và chỉ số bề mặt nhỏ nhất.
Diện tích hình chiếu, hàm lượng Magie và natri là những yếu tố ảnh hưởng mạnh nhất. Kết quả
thể hiện khả năng khai thác các yếu tố này để điều chỉnh độ hòa tan của muối cũng như sự cảm
nhận độ mặn theo thời gian.
Từ khoá: muối, nước bọt nhân tạo, hòa tan, tính chất hóa lý, Bayesian
Trích dẫn bài báo này: Lân N H, Hương N T N, Thịnh P H, Đạt L Q, Dũng N H. Ảnh hưởng của các tính 
chất vật lý và hóa học đến quá trình hòa tan của muối biển . Sci. Tech. Dev. J. - Eng. Tech.; 
4(2):1009-1018.
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