Effect of Temperature on the Water Adsorption Isotherms of High-PressureProcessing BarleY Flour

A thesis presented
By

Z:HANG Xilin
Supervisor Tetsuya, Araki, ph,D, Associate Professor

Submitted to the Graduate school Agricultural and Life Sciences, the Universityof Tokyo in partial fulfillment of the requirement for the degree of Master ofAgriculture
January,20l8

Content

Moisture Absorption Isotherm

Discussion:

16

35

Acknowledgements
Prima face4 I am grateful to the God for the good health and wellbeing thatwere necessary to complete this thesis.

I would like to thank my thesis advisor associate professor Tetsuya Araki ofthe
Graduate School of Agricultural and Life Sciences at University ofTokyo. The door toProf. Araki oflice was always open whenever I ran into a trouble spot or had a question
about my research or writing. He consistently allowed this paper to be my own work,
but steered me in the right the direction whenever he thought I needed it.

I would also like to thank associate professor Shigeaki Ueno of the Graduate
School of Education at University of Saitama. Thanks for providing the experimental

lab and necessary experimental equipment for me. When I came into diffrculties inexperiments, he always helped me solve the problems.

I take this opportunity to express gratitude to all of the Department faculty
members for their help and support. I thank my fellow labmates in for the stimulating
discussions, for the sleepless nights we were working together before deadlines, and for

all the fun we have had in the last four years. Also I thank my friends accompanying
me in my most difficult time.
Last but not least, I thank my parents for the unceasing encouragement, support
and attention. I am also grateful to my partner who supported me through this venture.

Introduction
Research Background:
Barley, one ofthe first cultivated grains in the world, is a major cereal grain grownin temperate climates globally. It has been widely considered that barley was widelygrown in Eurasia in 10000 years ago. The exact origin of barley is actually debatable,possibly originating Egypt, Ethiopi4 the near East or Tibet (1). Although barley is oneof the earliest cultivated crops, its cultivation in China and India is thought to beoccurred later. In 2005, barley was ranked fourth among grains in quantity produced,

only behind maize, rice and wheat (2).
Barley is a member of grass family, which has many different varieties. From Genus
Hordeum L,barley is from Monocot group, Poaceae Family. One way to classifr barley
is to identifu it by whether there are two, four or six rows of grains on the head (3, 4,5). Two-row barley can produce 25-30 grains, while six-row can produce 25-60 grains(6) (Figure 1.1). Two-row barley has a lower protein content than six-row barley while
has a more fermentable sugar content. High-protein barley is suitable for animal feed.

Low-protein barley is always used for malting because it needs shorter steeping and hasless protein in the extract that can make beer cloudy. Six-row barley is common in

American lager-style beers, when adjuncts such as com and rice are used. In themeantime, two-row barley is popular in traditional German beers. Few research has
been done on differentiating four-row barley because it has been believed that it isactually a loose six-row barley. Another way to classifu barley is to describe the beards
covering the kemels. In the barley germplasm database, beards (awned) are describedalong the following molphology (6).

1. Long awned

2. Short awned
3. Normal hooded
4. Elevated hooded
5. Subjacent hooded
6.

Long amed in ccntralrow,and aゝ

7.

Shortamed in ccn"al rOvレ

8.

A、vnless Or awnletted in ccntral and lateral rOws

9.

Elcvated hOOds ill central rOゝ r,and aⅧ

Barley Can」 SO be dCSCnbedおmletted Or aⅥ mlcss in lateral rows

,and a,■ 1lcted Or aЧ 41less in lateral r。

(7,8,9)lcss in lateral rO、 、
′
s.

■7s

ヵ

l. Hulled or hulless (naked)
2. Feed or malt type
3. Height (dwarfl
4. Seed color (colorless, white, yellow, blue)(Research has shown that some hulless cultivars are resulting in more digestible,

high-protein feed, especially for swine and poultry (10))
ｌ
ｒ
︐
職

■ｌ Ｌ■

．
︱

ヽ

ス
ー

n
Figure 1'1 Two-Row and Six-Row

Barley(11)'
species with 14 chromosones
Being known as a self-pollinating' diploid
Spontanuem' is abundant in grasslands
barley's wild an ceslor, Hordeum vulgare stbsp'
of Westem Asia and northeast
and woodlands tkoughout the Fertile Crescent area

Africa and is abundant in disturbed habitats, roadsides and orchards'

ln 2016/2017 crop year, barley production amounted to approximately 148'03
million metric tons. In 2017 t2018 crop year, barley production is estimated to be
137.47 million metric tons, which represents a decrease of 9.57 million metric tons or
a -6.5loh in barley production globally (12). Below (Figure 1.2) is the graph of majorbarley producers in 201612017 crop year. As it is indicated from the graph, European

Union produced the largest amount of barley, which is 59.9 million metric tons. It canbe also understood that barrey
because it is more adaptabre

has a wider ecorogical range

than other cereals, tolerating

except for acidic and wet soils'
at altitudes unsuitable for wheat

Maj o r ba rre1.,

many diverse environments

Barley can be grown on so,sunsuitable for wheat, andor oats (13). Because it is highry

dry environment, making it an attractive

than any other cerear

tolerate with salty andtrait and it can be grown near dessert",o,.i1i,ll"".lTlf;;l,r1, ",areas.

r, by co u n rry (in口■■■■■■■■ 9.61()thcrs

ヽ4oroc(:01 0.62:raq

ロ
ロ 1.55

:odia

■
口
: 1.9

China

●■ 2
■● 2.05

Ethiopia

Bclaus ■口1 2.1
■■:3

lran

Kazab曲 m●■■: 3.23

Argcntina

●■
■
■ 3.3

Tu

cy

Cm

a

■■■■■■■■ 8.8

Ukranc■■■■■■■■ 9,■￨￨￨￨口 4.75

Auヽ ralia

13.41

Russla17.55

Euro"an Union

59.9
0

10

20

30

40

50

60

70

Amount in million metric tons
Figure 1.2 Major barley producers worldwide in 201612017, by country
Barley can be used in many different ways, however, the majority ofall barleyis used for animal feed consumption, or malting. High protein barleys are generally
valued for food and feeding, and starchy barley for malting. Malting is one ofthe mostimportant use of barley, which malt is used to produce beer distilled alcohol, malt syrup,malted milk, flavorings and breakfast foods. Both six-row and two-row barley varieties
can be used for malting, but six-row varieties are ideal for beer (14). What is malting?

Malting can also be defined as controlled sprouting, which is a complex interaction ofgenes involved in germination, growth and development (15). The reason why it isnecessary to apply malting is that the starch, protein and nucleic acid molecules that are
stored in barley grains. These large molecules are not good nutrients for brewing yeast
or they are not good for supporting fermentation reactions performed by brewing yeasts.
´０For brewing yeasts to make good use of these nutrients, these large and structurally

complex compounds must be partially degraded into sugars, amino acids andnucleotides. When barley seeds germinate, hydrolytic enzymes are synthesized orconverted to active forms that can readily degrade these large compounds. Steps ofmalting include steep, germination, kilning, browning and optional bleaching. Steep isto raise moistue lo 42-44%o uniformly through kemel. The time for steep should not be

too long or too short. If steep is too long, it could result in mold and bacteria grow; if
steep is too short, poor malt will be formed. Germination is to put barley on beds withforced air and 100% RH l5 "C temperature. The purpose ofthis step is to release alpha-,beta-, amylase, glucosidase, dextrinase. These enzymes are temperature stable duringdrying. Kilning is to reduce moisture and dry malt, while browning to add flavor andcolor. After that, optional bleaching is applied to reduce some of the color. Duringmalting, the acrospire (the plant shoot) grows along one side of the kemel. As it grows,
pre-existing enzymes are released and new enzymes are created in the aleurone layer
which "modify" the endosperm (the protein/carbohydrate matrix starch reserve) for theacrospire's use (16). Malted barley is the source of the sugars, primarily maltose, which

are fermented into beer. The grain partially germinates, releasing enzymes in thealeurone layer (outermost layer ofthe endosperm). New enzymes are created that break

down the endosperm's protein/carbohydrate matrix into smaller carbohydrates, aminoacids and lipids, and open up the seed's starch reserves. The endosperm is composed oflarge and small starch granules that are packed in a protein matrix. The cell walls within

the matrix holding the starch granules are primarily composed of beta-glucans (a typeof cellulose), some pentosans (gummy polysaccharide) and some protein. The degree
to which the enzymes unpack the starch granules (i.e. breakdown the endosperm) for
use by the growing plant (or brewers) is referred to as the "modification." It refers to

all ofthe polyrner-degrading processes that occur during malting. One visual indicatorthat a maltster uses to judge the degree of modification is the lengh of the acrospire
which grows undemeath the husk. The length of the acrospire in a fully modified malt

will typically be 75-100% of the seed length. Drying is used to stop the malting process
when the proper balance between resources converted by the acrospire and resources
consumed by the acrospire has been achieved (17). The reason of malting is to generate

new these enzymes, to break down the matrix surrounding starch granules, prepare thestarches for conversion, and then stop the reaction until the brewer is ready to utilize

the grain. Finally, the green malt is dried with heat and the acrospire and rootlets areknocked off by tumbling' Thekiln drying of the new malt denatures

enzymes, but several types remain, incruding

many of thethe ones necessary for starch conversion.

The amount of enz]lll;,atic starch conversion potential that a malt has is referred

to as its

"diastatic power" (17). Figure 1.3 indicates the change of barley kemel during malting.

1■ １１ １Ｂ ＥＥ Ｆ Ｉ
￨￨

︲︼
劇

L-i

Figure 1 .3 Change of Kemel during Malting
Beta-glucans are soluble dietary fiber component of barley and oat bran' It is

important for the malting industry and indicates how well the endosperm is modified(16). High levels ofbeta-glucan can cause a viscous wort that may cause problems withfiltration or hazy beer. Thus, lower levels of beta-glucan are preferred for brewing.
Brewing is the production of beer by steeping barley malts in hot water andfermenting the resulting sweet liquid with yeast. During brewing, malted barley issoaked in hot water to release the malt sugars. Then the sugar solution is boiled withhops for seasoning. After seasoning, the solution is cooled and yeast is added to start
fermentation. During the fermentation, sugius are digested, and COz and ethyl alcohol

is produced. When the fermentation is completed, the beer is bottled and added withsugar to provide the carbonation ( 17). A high quality malt will contain the right amountol hydrolytic enzymes and metabolites to fulfill these requirements and will have theright degree of fiiability to allow many of its components to be readily solubilized
during mashing (18). During malting and mashing, the barley starch should be almost
completely degraded into sugars that can be utilized by the brewing yeasts, whereas
い０only about 45% of the barley proteinshould be solubirized. Toomuch protein
in beers with poor foaming characteristics g).
(lwheninsufficient protein hydrolysis occurs, the remaining
proteins may interact with
polyphenols to form beer haze precipitatessolubilization is thought to resurt

Four amylolytic enzymes are generally thought to participate in convertingthestarch in malted barley into fermentable sugars: these are a-amylase, b-amylase, aglucosidase and limit dextrinase. During brewing, amylase enzJmes digest amylose(linear starch) and amylopectin (branched starches) into hexose sugars (19). The sugars
are a nutrient source for the yeast to facilitate fermentation. Suffrcient sugars are needed

to obtain the desired alcohol level.

In addition to malting, another important use of barley is for animal feed andhuman consumption. As nutritional scientists claimed that barley is a very good sourceof molybdenum, manganese, dietary fiber, and selenium, and a good source of copper,

vitamin Bl, chromium, phosphorus, magnesium, and niacin (20). Barley can provide
bulk and decrease transit time of fecal matter, thus decreasing the risk ofcolon cancer
and hemorrhoids, barley's dietary fiber also provides food for the "friendly" bacteria inthe large intestine. As those Eco-friendly bacteria ferment barley's insoluble fiber, they

produce a short-chain fatty acid called butyric acid, which serves as the primary fuelfor the cells of the large intestine and helps maintain a healthy colon. These helpful
bacteria also create two other short-chain fatty acids, propionic and acetic acid, which
are used as fuel by the cells of the liver and muscles (20). propionic acid is proved tohave effect on lowering cholesterol. In an animal studies, propionic acid has beenshown to irlhibit HMG-CIA reducrase, an enzyme involved in the production
cholesterol by the liver (21 ). By lowering the
propionic acid contributes to loweringofactivity of HMG_coA reductase,blood cholesterol levels.

Besides, barley's dietary fiber is highto lower cholesterol by binding

in beta glucan (Figure 1.4), which helps

to b,e acids and removing themfrom the body via thefeces' B,e acids are compounds
used to digest fat that are
manufactured by the liverfrom cholesteror (22). whenthey
are excreted along withbarrey,s fiber, the liver
must
manufacture new b,e acids
and uses up more cholesterol,
thus rowering the amountofcholesterol in circulation'
Soluble fiber may arso reduce
the amount of choresteror
manufactured by the liver'
As it is pubrished in the American
Journar of Ctinical０フNulrition, barley's fiber has multiple beneficial effects on cholesterol. In this study of
25 individuals with high cholesterol (postmenopausal women, premenopausal women,
and men), adding barley to the American Heart Association Step 1 diet resulted in asigrificant lowering in total cholesterol in all subjects, plus their amount of large LDL
and large and intermediate HDL fractions (which are considered less atherogenic)
increased, and the smaller LDL and VLDL cholesterol (the most dangerous fractions)

greatly decreased (23). In most cases, beta-glucans form a linear backbone with 1,3
beta-glycosidic bonds but vary with respect to molecular mass, solubility, viscosity,
branching structure, and gelation properties, causing diverse physiological effects in(24)' Waxy
humans and animals. Barley grain usually contains 2-10Vo beta-ghtcan
content' waxy
starch phenotypes are usually associated with high beta-glucan
than barley types withendosperm types generally have greater beta-glucan contents
to be problems in beer
normal starch (25)' Although beta-glucans are considered
problems with filtration or hazy beer'
brewing, causing a viscous wort that may cause
human health'high level ofbeta-glucans are beneficial to
Barlcy,s iber can prevcnt or hclp、

conirmed that ctting high ibcrぉ

ith a nulmber of dillercnt cOndhiOns.A study。ds,suCh as barlcy,helps pκ ve■

AlmOゞ lo,o00 Amcncan adults patiCipttcd in this study ald weFおhean discasc.

llowCdお r19

6 1css cOronar)′ hean

years.Pcoplc cating the inOst iber,21 gramS per day,had 12シ

disease(CHD)and ll%less cardiovascula discase(CVD)COmpared tO thOSC eating
the least,5 gran■ S daily.Those eating thc mostヽ

Vater‐ S01uble dietary ibcr f̀red cVen

bettcr with a 15%● eduCtiOnin nSk OfCHD ald a 109る

nsk reduction in cVD(26).Thc

H

‖

OH

H

H

H
H

H,

H

酬

H0

Figure 1.4 Structureof Beta 1' 3-Glucan

10fiber in barley can also help to prevent blood sugar levels from rising too high in people

with diabetes. FDA suggests that people should increase their intake ofbarley not only
for the benehts of lowering the cholesterol level but also for the potential of reducing
the risks ofhaving heart diseases. Barley is a good source ofniacin, which is a vitamin

B that provide numerous protective actions against cardiovascular risk factors" Niacin
has an effect on reducing total cholesterol and lipoprotein (a) levels. Lipoprotein (a) is
a molecule composed of protein and fat that is found in blood plasma and is very similar

to LDL cholesterol, however, it is even more dangerous as it has an additional moleculeof adhesive protein named apolioprotein (a), which renderc Lipoprotein (a) morc
capable of attaching to blood vessel walls (26). Niacin may also help prevent free
radicals from oxidizing LDL, which only becomes potentially harmful to blood vessel

walls after oxidation. Lastly, niacin can help reduce platelet aggregation, the clumping
together of platelets that can result in the formation of blood clots. One cup of barleysoup will supply you with 14.2%:o of the daily value for niacin.

Beta-glucans in barley not only have benefits on reduction ofblood cholesteroland glucose and weight loss by increased satiety, but also have functional properties infood-processing and end-use quality, with the exception of beer brewing as it was
mentioned in the above text. Positive relationships between beta-glucan content andwater uptake during cooking and the crumb moisture content of bread baked with 30%
barley flour, and a negative relationship with the hardness ofcooked noodles containing
30%o bNley flour were reported (27). Molecular structure of cereal beta-glucans andphysical and functional properties of isolated oat and barley beta-glucans incorporated
into various food products are also mentioned by scientists in 2007 (28).

Although barley has been proved to have plenty of health benefits, there arehuge difficulties on commercial processing of barley food products due to its highviscosity. The amylose content ofbarley starch varies from 0% in zero amylose waxy
to 50% in waxy, 20-30%o in normal and tp to 45%o in high-amylose barley (29). Barleyexhibits lower pasting temperature, and greater hot-paste viscosity, swelling power,
granule fragility and freeze-thaw stability. People can both direct intake barley andintake barley-product indirectly. In Asia countries, wheat and rice are the major staple

in people's dining tables, while barley is not that co rmon as staple diets. As human's
eating habits took a long time to get changed and developed, it is not that reasonable tochange Asian's dietary structure. Another way is to manufacture barley functional foodL7

products, such as barley soup or different types ofproducts. However, the viscosity ofbarley-water mixture is much higher than other starch with water, making it extremely

difficult in food processing. Therefore, lowering viscosity of barley has been studied
by many scholars.

rz

Previous ResearchPrevious research has indicatedthat

relatively lower viscosity than normal

barley flour treated under 600 Mpa has

abarrey flour (30). High-pressure-processedbarley flour was added with water for thebarley starch to gelatinize. The temperature
was adjusted for starch to fury be geratinized.
After the treated barley flour samples
were fully become gelatinization, the viscosity was continuously
measured by Rapid
viscosity Analyzer. As gelatinization starts, the viscosity first reaches
to the highest
amount. After l0 minutes, the viscosity reaches to the lowest

amount. Then theviscosity starts to increase again and then remain in a constant number, which is named
as final viscosity. In this research, the change of viscosity of pressure-treated barleyflour followed the trend ofgelatinization ofnormal starch (Figurel .5). However, barleyflour treated under 550 MPa and 600 Mpa had relatively lower amount of the highest
viscosity and final viscosity than barley flour without pressure treatment. The highest

viscosity during gelatinization decreased as the pressure treated on barley flour
increased (Figure 1.6). As it was indicated in the research, the highest viscosity of
unheated barley flour during gelatinization was 5400 cP.The highest viscosity ofbarleyflour continued to tank as the treated pressure increased but not larger than 300 MPa.
During 350 MPa to 450 MPa, the highest viscosity increased. Barley flour treated under
550 MPa had much lower amount of the highest viscosity in gelatinization. The highest

viscosity in gelatinization of barley flour treated under 600 MPa was 2700 cP.

13

０
０
０
︲
６

100

０
０
０
︲
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90
80

60
０
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50
40

⌒

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20
10

ｎ︶

0

220

440

880

660

MPa

-300 MPa-350 MPa-400 MPa-450 MPa-500 MPa-550 MPa-500-Temp.

30

0‑0.l MPa‑200 MPa

ａ ＥＰ
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1100

Time(SeC)

Figure 1.5 Gelatinization of High-Pressure-Processed Barley (47)

０
︲
０
︲
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０
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０
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ｎ︶

0

100

200

300

400

500

600

Pressure(IMPa)

Figure 1.6 Relation between Highest Viscosity and Pressure (47)

The reason accounting for the decrease of viscosity after high pressure
processing was also been studied. Treated with high pressure, the damaged starch rateincreased, indicating high pressure caused damage in starch granules. It was also been14

proved that swelling power decreased as treated pressure increased. According to Xray diffraction (Figure 1.7), the type of crystals ofbarley flour granules is a combination

oftype V and type B. In 20' , a new peak can be observed. Based on all these evidence,

it was been estimated that amyloseJipid complex was formed during high pressure
processing (31). The formation of amylose-lipid complex is assumed to have close

relation with the decrease of viscosity. Amylose-lipid complex could increase thesolving temperature of amylose, making it more diffrcult for amylose in starch to get
dissolved in water. In order to get dissolved, one has to reach to higher temperature.

Amylose-lipid complex is capable ofinhibiting moisture absorption of starch granules.
Last but not least, amyloseJipid complex combines with amylose in starch granules,
reducing the amount offree arnylose. As the amount of free amylose decreases, fewer
amylose dissolved in water, resulting in inhibiting the elevation of viscosity.

6000

5000

９に
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3000

2000

1000

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Figure l.7x̲ray Barley F10w(47)

15

32

36

40

oisture Absorption Isotherm
Moisfure sorption isotherms describe the relationshipd water activity in food. The water contained in foodr the interactions that exist between the components'he concept of water activity (a*) comes

between moisture content

appears in different forms based

offood and water morecules (32).

from a series of thermodynamic

onsiderations that entail the chemical potential mathematical expression of the.omponent, which constitutes the tendency of a component to escape t}re system. It canalso be defined as the ratio of water vapor pressure at a constant value of pressure andtemperatue. Another widely-accpeted definition is the equilibrium relative humidity of
the air surrounding the food at the same temperatue (33), and it can be expressed inequationl.
﹈
ツ一 ｍ
ｐ
一れ

Qw,f = Q't,v =Equation l.

Where f: food; v: vapor; v,sat: pure water vapor pressure'water activity of food equals the relative humidity of the air above it divided by100, indicating that an equilibrium has been reached, constituting a form of
measurement of the water amount available in food for a reaction series of biochemical
and microbiological nature (33-35).

Food sorption isotherm describes the thermodynamic relationship between
water activity and the equilibrium of the moisture content ofa food product at constanttemperatwe and pressure. It is important to understand sorption isotherms in foodscience and technology because ofdesign and optimization of drying equipment, designof packages, predictions of quality stability, shelflife and calculation of moisturechanges that may occur during storage. Several preservation

for the purpose of extend the sherfrife of food products
availability of water to microorganisms and inhibiting
The tlpicar shape of an isotherm reflects
Weaker water molecule interactions
becomes more unstable' water

physical state of the compounds

processes were developedin the way of lowering the

enzymatic reactions (32, 36-40).

the way in which the water binds thesystem.

generate a greater water activity,

thus, the productactivity depends on the composition,

temperature and

(41).

16

How to acquire sorption isotherms. Empirically, sorption isotherms can begenerated from an adsorption process or a desorption process; the difference between

the curves is defined as hysteresis (Figure 1.8). Water adsorption by food products is aprocess in which water molecules progressive and reversibly mix together with foodsolids via chemisorption, physical adsorytion, and multilayer condensation. One
isotherm can be typically divided into three regions; the water in region A represents

strongly bound water, and the enthalpy of vaporization is considerably higher than theone of pure water. The bound water includes structural water (H-bonded water) andmonolayer water, which is adsorbed by hydrophilic and polar groups of foodcomponents (polysaccharides, proteins and so on). Bound water is unfreezable and it is

not available for chemical reactions or as a plasticizer. In region B, water molecules

bind less firmly than in the first zone, they usually present in small capillaries. The
vaporization enthalpy is slightly higher than one ofpure water. This class ofconstituent
water can be looked upon as the continuous tmnsition from bound to free water. The
properties of water in region C are similar t those of the free water that is held in voids,
large capillaries, crevices; and the water in this region loosely binds to food materials(42-45). Moreover, hysteresis is related to the natue and state of the components offood, reflecting their potential for structural and conformational rearrangements, whichalters the accessibility ofenergetically favorable polar sites. The presence ofcapillaries

in food results in considerable decrease in water activity. The explanation for theoccurrence of moisture sorption hysteresis comprises the ink bottle theory, the moleculeshrinkage theory, the capillary condensation, and the swelling fatigue theory (46).

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Figure

1.8

o

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Watsr Acrrrrry

for a Typical Food Product, showing the hysteresist7

1

Sorption Isotlerm

Brunauer et al., 1940 (47) classified sorption isotherms according to their shapeand processes, establishing five different types; as it is shown in Figure 1.9. Type l:Langmuir and,/or similar isotherms that present a characteristic increase in water

activity related to the increasing moisture content; the first derivative of this plotincreases with moisture content and the curves are convex upwards. This tlpe ofsorption isotherm is tlpically applicable in the process of filling the water
monomolecular layer at the intemal surface of a material. Type 2: sigmoidal sorption
isotherms, in which the curves are concave upwards; it takes into account the existenceof multilayers at the internal surface of a material. Tlpe 3: known as the Flory-Huggins
isotherm, it accounts for a solvent or plasticizer such as glycerol above the glasstransition temperature. Type 4: it describes the adsorption of a swellable hydrophilicsolid until a maximum of site hydration is reached. Type 5: the Brunauer-Emmett-Teller(BET) multilayer adsorption of water vapor on charcoal and it is related to the isotherms
type 2 and type 3. The two isotherms most fiequently found in food products are thetypes2and4(48-50).

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In order to mathematicalry express the relation between
food and its moisture conlent, diverse models have been

the water activity ofdeveloped such as nonrinear,linear, regressional models, constituted in their parameters by two,

three, four, and six

partial regression coefficients, which explain each one of the threezones that theisotherm of sorption of humidity conforms. In many cases, the model that is suitabre
for certain food product is not suitable for a different one, what is more, the model only
exhibits a suitable predictive ability for certain moisture activity ranges.
Several mathematical models have been proposed to describe sorption isotherms.
Some ofthem were developed with theoretical basis to describe adsorption mechanisms(35, 43); whereas the others are just empirical or a simplifrcation of more elaboratemodels. In some ranges of water activity, sorption isotherms can be approximated tolinear equations (44). There are some semi-empirical equations with two or three fitting
parameters to describe moisture sorption isotherms. The most cornmon equations thatare used for describing sorption in food products are the Langmuir equation, the BET

equation, the Oswin model, the Smith model, the Iglesia-Chirife equation, the GABmodel, and the Peleg model (22).

Langmuir equation
Langmuir proposed the following physical adsorption model on the basis of

unimolecular layers with identical and independent sorption sites, and which isexpressed as it is shown in equation 2:

１⁚ ′ノ

１ニ

ヽ

一 ●■

w

ー ７牝

亀どヽ
面

¨

/1

1̲=̲

cMo

Equation 2.

where Mw is the equilibrium moisture content(kg water/kg dry matter), M0 is themonolayer sorbate content (kg water/kg dry matter) and C is a constant.
The value of the monolayer (M0) is of particular importance because it indicatesthe amount of water that is strongly adsorbed in specific sites, and it is considered to be

the value at which a food product is the most stable. Langmuir's isotherm is the most

crucial equation among the theoretical models, which is based on the forces acting
between the product surface and the water condensed from the vapor .rs a19monomolecular layer. The extensions ofthe Langrruir's underpinning idea on multimolecular layers result in the BET and GAB isotherms, which are able to describe

sigrroidalshapedisothermscommonlyobservedinthecaseoffoodandotlrermaterialsof biological origin (45).

Brunauer-Emmett-Teller (BET) equation
The BET equation (equation 3), which is the most
systems, was first proposed by Brunauer, Emmett

widely used model in foodand Teller (43)' It represents a

firndamentalmilestoneintheinterpretationofmulti-layersorptionisotherms'
particularlythetypesllandlll.Itisalsoaneffectivemethodforestimatingtheamount(22' 48)'
water in specific polar sites of dehydrated food systemsof boundMw

MoCq*(t- rru)( t+(c-fiIw) Equation 3

where M 0 is the monolayer moisture content, which represents the moisture content at

which the water attached to each polar and ionic groups starts to behave as a liquidJike
phase. And, C is the energy constant related to the net heat of sorption; it is related tothe difference between the molecules that sorb energy of the first layer and the otherremaining layers. These constants are also the constant characteristic ofthe isotherm ofsorption of monolayer of Langmuir. Almost in all cases, the deviation of the linearityof these graphs indicates that, at high vapor pressures, the amount adsorbed by thesorbent is lower than the one predicted by the isotherm (22, 49).

The BET equation represents a basis in the interpretation of isothermal sorption

multilayers and it has been applied in gas adsorption and porous steam in surfaces andsolids, as well as in water, especially in steam absorption, by homogenous polymers
and other materials. Nevertheless, the considerable success of t}re isotherm is rather

qualitative that quantitative. If we considered the linearized forms of the equations ofisotherms as the estimation ofthe applicability rank that they own in its linear sections,

it can be observed that, in almost all cases, BET graphs are linear only in a limited rangeof water activity from 0.05 to 0.45. This difficulty in the process of fitting theexperimental dates on the totality of the range of relative pressure application20

determined that the main appricationof the BET equation is the one related to theestimation of surface areas (49). The theory
equation has been questioned due to thebehind the development of the BET

assumptions that (a) the rate of condensationon the first layer is equal to the rate ofevaporationenergy ofall of the adsorbates on the first layerfrom the second rayer; (b) the bindingis same; and (c) the binding energy ofthe other layers is equar to the one of pure adsorbates.

The assumptions ofa uniform

adsorbent surface and the absence of rateral interactions between

adsorbed morecules

are incorrect, considering the heterogeneous food surface interactions.

Nevertheless,the theoretical basis that provided this isotherm stimulated the investigation fordeveloping altematives that broaden the scope of the BET equation, or forreformulating the model to find new physical approaches (39, 50). The BET equation

can be considered to be the most useful for determining the optimum moisture
conditions for good storage stability, especially for dehydrated food products (3 I ). The
parameters of the BET equation for different food products are listed on table 1 .1 .

Table l l. Estimated parameters of the BET equation for various food products.

hoductTemP.rC

M,

C

f

Type

Corn flour

1)

0.056

ヨ)2̲=2

0.99

A

Yrm

15

0.ス 〕
6

2.引 18

0.9t

Il

{I"8

7.345

nr

D
D

Il

0̲(55

9.86

nr

A

3r',)

0■ 624

1.r.06

nt

f'

]{)

0.137

26.4v)

nr

Applcs *r

yl

0.334

20.1fr6nr

Chha d podo

35

0.碑 8〕

1..161

0.99.fA
A
D
D

Blucbcrry

.t{)

0.m7

5.713

nr

A

Blucbcr4

.l{)

0100

:0145

nr

D

Dncd pouo'

Drrctl pouo t

Dncd tomrlo
Applcs"'nr: not reported; D: desorption; A: adsorption.
十aw rangc:0.1̲0.5;ホ *aw rangc:0.11‑‑0.5;Ⅲ **aw range:0.25‑0.54.

Oswin model: It is an empirical model that consists in a series expansion for
sigmoid shaped curves and it was developed by Oswin, 1946. Its equation is as below:

27

″

′︱
ヽ
ε

Ｌ

6lp

7- ow )'

Where C and n are constants.

The oswin model was used to relate the moisture content of fatfree dry milk
and freeze dried tea up to a water activity of 0.5, as well as for various food listed inTable 1.2.
Table 1.2. Estimated constants of the Oswin model for several food products

koducrTe-p.'Ccn

R:

Com flour

220. 106

o.n

o.99

Yam

,t5

0.353

0_,195

0.991

Dried pouto

30

0.125

(〕

.461

rtr

Dried pouto

30

0.103

0.548

rlr

Dricd omato pulp

30

0.:X)3().=:41I)r

Dried cashew apple

30

10.72

0.581

().lX,79

Banane pulp

2{)

0.164

1.122

0.91t69

Mango pulp

20

0.114

0.B55

o.w2

G"lic

5{)

0.{D5

().720

0.991

Apple

50

0̲332

0.670

O.S7&i'

Halsey Model: This model provides an expression for the condensation ofmultilayers at a relatively large distance from the surface, assuming that the potential
energy ofa molecule varies as the inverse power of its distance from the surface. Thisequation is good representation of the absorption data regarding isotherms type I, II
and III. Moreover, this equation described the sorption behavior of food products that

ソ
′
面
儡
一
直
話
︲
︲
ｅ
上崎¨¨ｂ
¨
¨
一
Ｓ
ｍ
ａ
・
ｎ

¨
¨
¨
¨
″
一嚇

ｉ叩ｔ
ｅ瑯ｄ
司
¨ Ｒ
ｃ
ｒ
ｂ
︲
︒
ｎ
ｃ
一
一¨
ｓ
ｏ
¨
ｅ
¨
ｍ
ｄ
ｓ
ｓ
ｉ
ｉ
´
．
¨
﹄
﹄
﹈

contain starch. This model is descried as it is expressed as below:

ル
Ｆ■
０

ｅ
Ｃ
ｎ

６
７

Ｃ

・て

¨
¨
赫一

あ

ｌ
ｐ︲ ｉ

Ｓ

︲
．

旋
Ｔ
ｍ肺
； ｔ
ｅ
ｔ

︲
層
ｃ︲
ｍ
Ｍ
ｙ満
ｔ
︐ｂ
．

ｓ ｒ

鰤嶋陥山一
﹈

¨
呻輌
嚇

22

ん

■一
ヽ１ ′

一Ｗ
Ｃ 一α

一ｎ
ｌ

一

′ ︱ヽ

怖

where c and n are constants. The Halsey model was used for various food products,
aS it iS listed in Table l.3.

Table l.3 Ettimated Paraineters Of■ e Halsey Modcl for Vanous Food Products.

Product Temp. oC C,
Corn flour0̲(Ю 2 2̲516

0̲96Fear os rnrrtic

■■

つ

R2

dehvdration

4(〕0̲173 0/66

0̲99

Pcar

40

0.147 0̲853

0.99

Banana pulp

20

0.185 0̲756 0̲9871

Blueberry40

0.108 0̲890,lr

Etlucberry

=1(〕

0.056

1l r

1̲672

Nr: not repoted;

一ε¨Henderson model: This is a commonly used model and it can be expressed as

it is described in the equation listed below:

■

一

′１ ヽ

怖

′

ノ■

Where C and n are constants.

According to this model, a plot of ln(-ln( 1-a*))versus ln M* should give as a result astraight line. However, Rockland observed three localized isotherms that did notprovide precise information on the physical state of water. The constants ofthe
Henderson model in different food products are listed on Table 1.4.

23

Table 1.4 Parameters ofthe Henderson Model for Various Food products

Pr.oductPssion fruir
pecl
Pineepplc
D€CI

Yam

Dry cashew
rDDlc

Walnutkernels
Welnutkcrnels

Tcrllf.

C

OC

tI

R]

25

2,1fft 0̲591 0.990

25

2.M

.15

0̲126 0.126 0̲933

30

0̲0509l.0u 0.9926

?s

0.037

1.781 0.9854

35

0.123

1̲267 0.9990

24

0.601

o.993

Significance of Research

Aspreviousresearchindicatedthepotentialofhighpressureprocessingol
lowering the viscosity of barley flour, it is possible for pressurized barley flour to becommercially manufactured into functional products. However, it is important tounderstand sorption isotherms of both barley flour and high pressure treated barleybecause of design and optimization of drying equipment, design of packages,
predictions of quality stability, shelfJife and calculation of moisture changes that may
occur during storage. Seveml preservation processes were developed for the purpose ofextend the shelf-life of food products in the way of lowering the availability of water tomicroorganisms and inhibiting enzymatic reactions (32, 36-40). In this experiment,
moisture absorption isotherms of barley flour samples (0 MPa 200 MPa and 600 MPa)
were measured and the experimental data was fitted with absorption isotherm model.

?qMethod:
Barley Flour (Mocchiriboshi, 7.2ohprotein,l.6oh fat,77.5% starch) used in thisexperiment were bought from Nagakura Company (Figure 2.1). The material was
manufactured in 2014, which was also used in the experiment named Effect of High

Pressure Processing on Adjusting Viscosity of Barley Flour-lYater Mixture. The
experiment was completed by previous member Mr. Sasao Shoji.

■ＦＦ

Ｆ ＦＦ

Figure 2.1 Appearance of Mocchiriboshi

Barley flour dough samples were prepared by adding 40 grams offlour with 40
grams of distilled water in one-300-ml-Beaker. A glass rod was used for mixing theflour with distilled water until barley flour dough was formed. Polyethylene bags
(FLAEM NUOVA, MAGIC VAC roll, ACO-1025) were used pack barley flour doughand the samples were vacuum-sealed by vacuum sealer (TM-H) manufactured by

FURUKAWA MFG. CO., LTD., which the air was deflated for 15 seconds and thenthe polyethylene bags were sealed for 2 seconds.

Barley flour dough samples were stored in one refrigerator under 4oC for twodays. After two days, the samples were sent to Niigata University of Pharmacy andApplied Life Sciences to perform high pressure processing (The machine was shownin Figure 2.2). Vacuum-packaged Mocchiriboshi samples were pressurized under 200
MPa and 600 MPa through water pressure under 20oC. After the water pressure reached26

to the set pressure, and the temperature reached 20'C, the samples were remained in thepressure for l0 minutes.

Fignre 2.2 is the photo of the High Pressure Processing Machine that wasapplied in this experiment. High pressure processing can be generated either by directcompression (Figure 2.3 and Figure 2.4) and indirect compression("<Jfie principles ofultra high pressure technology and its.pdD,"). In this experiment, direct piston-qpe
compression was applied to increase pressure. The pressure medium in the highpressure vessel is directly pressurized by a piston, driven at its larger diameter end bya low pressure pump.

颯

■L̲

日●
EEE=ヨ
● ●● ●,,● ′●

̲■

●●●
■

ヽ

Figure 2.2 High Pressure Processing Machine27

PR00U〔 T10ADI‖ G:日VESSEL PRE・ FILLiN6■D￨■UHPROCESS10
0ArC,￨

LOW
PRESSuRE

PRODUCT UNLOADINGく■■』PRESSURIZINGE

PROこ ESSED

H!GH

BATCH

PRCSSuR=HICHは ヽ SuRE

Figure 2.3 Principle of High Pressure Processing

ｒ ｌｌｌｌＬ■ヨ

lLa rdn ni?(ix
● ■

′ ノ

Figure 2.4 Direct method for generation ofhigh isostatic pressure uses a piston driven
by a high- pressure pump

The pressurized samples were stored in one freezer under -80'C for two days.

After that, the freezing samples were divided into small pieces through using a hammer.
The, the small samples were added in the beaker and performed fieeze-drying for 24hours. The air in the beaker was removed by using a pump (manufacture by EDWARD
28

The freeze-drying machine is shownCo., Ltd.) to reduce the pressure until -0 1 MPaG'
grounded into powder and readyin Figure 2.5. After freeze-drying, the samples were

for measurements.

L

Figure 2.5 Freeze-Drying Machine

The equilibrium moisture contents of samples were determined by agravimetric technique, in which the weight was weighed discontinuously within athermally stabilized desiccators (Figure 2.6 and Figure 2.7). For absorption, a 2.0009
sample of the freeze-dried pressurized mocchiriboshi flour was placed in a petri dishinside a desiccator. Each experiment was carried out in triplicate.
Saturated solutions with different water activities (Table 2.1) were used tomaintain relatively humidity inside the desiccators. The desiccators were then placedin an incubator (Figure 2.7) under20,25,30 and 35"C. The samples were weighed once

every two hours until they reached equilibrium. The samples were equilibrated until

there was no significant weight change, as evidenced by constant weight values(+0.0019). The period for the barley flour dough to reach equilibrium is 4g hours. The
experiment was carried out in triplicate.

29

」

./

,

ロ

′

Figure 2.6 the Image of Desiccators

「

r― ￢

Ea

L

.:

″一

｀
1■
中レ

．

´

く:'R, ヽ

´

一
一

.ドー

緻

綱目

Figure 2.7 the Image of Incubator

30

Table 2.1 Water Activity of Various Saturated Solutions in the Experiment
Saturated Solutions

Water Activity

Lithiuin chlondc

0.07

Potassium acetate

0.11

Magnesium chloride hexahydrate

0.224

Lithiunl nitrate

0.33

Sodium bromide

0.47

Potassium nitrate

0.577

Sodium hydroxide

0.752

SOdiuiFi Ch10nde

0.924

31

Results

Moisture Absorption Curve of Mocchiriboshi

0 Mpa

17
16

,
′

/
13

′

/

→

"‐

■
'OCChiribOShi OMPa at 20C

mOCChiribOShi OMpa at 30

″

‐●
"―

mOCChibOShi O Mpa at 25C‐‐mOCChiribOShi OMpa at 35C
・●′
'・

12
11

0

0.2

0.4

0.6

0.8

Figure 3.1 Moisture Absorption Isotherm of Mocchiriboshi under 0 Mpa

As it is indicated in Figure 3.1, moisture absorption isotherms follows type 2
isotherms in all temperature. However, the moisture content is varied in mocchiriboshi
being treated under different temperatue. The moisture content ofthe samples firstly
increased quickly as the water activity became higher. However, the speed ofincreasing

moisture content became stable from 0.4 to 0.6. When water activity was over 0.6,
moisture content increased largely. The moisture absorption isotherms of barley flourwith no high pressure processing treatment followed strictly with sigmoidal shape as
introduced in the above text. However, the moisture content differed as the incubation

temperatule changes. In the beginning, the moisture content was higher in barleysamples with lower incubation temperatue. After water activity was over 0.5, themoisture content ofbarley samples with higher incubation temperature tent to reach tohigher amount.

32

ａ
ｐ
︐

Ｍ

ａ

＾υ
０
２

Ｉ
ＬＩ

０
ｈＶ

Ｌ＝
Ｃ
Ｃ
Ｏ

Ｏ

Ｍ

ｅ
Ｖ

︐

ｕ
Ｃ

ｎ
Ｏ

０

０

ｅ

Ｌ０

Ａ

ｕ

０

Ｍ

２
２
︲
２

︵
ぺ ︶︶ＣＯ︶Ｃ００ ｏ﹂コ● 一
ｏ８

ノ
/1,

/

--Fmocchiriboshi 2SC′-+-mocchirlbosih 35C-+- mocchirlboshi 20C.-4-- mocchiriboshi 30 C

12

10

0

0.2

0.4

0.6

0.8

1

Water Activity

Figure 3.2 Moisture Absorption Isotherm of Mocchiriboshi under 200 Mpa

As it is indicated in Figure 3.2, moisture absorption isotherms follows type 2
isotherms in all temperature. However, the moistue content is also varied inmocchiriboshi being treated under different temperatures. The moisture content ofbarley samples treated under 200 MPa is higher than that of barley samples withoutpressure treatment. The moisture content ofthe samples firstly increased quickly as thewater activity became higher. However, the speed of increasing moisture content
became stable fiom 0.4 to 0.6. When water activity was over 0.6, moisture content
increased largely. The moisture absorption isotherms of barley flour with 200Mpa highpressue processing treatment followed strictly with sigmoidal shape as introduced in
the above text. However, the moisture content differed as the incubation temperaturechanges. In the beginning, the moisture content was higher in barley samples with lower

incubation temperature. After water activity was over 0.5, the moisture content ofbarley samples with higher incubation temperature tent to reach to higher amount.

33

Mositure Absorption Curve of Mocchiriboshi600 Mpa
16

15

︵
ｏΣ
Ｓ ︶″Ｅｏ″Ｃ００ ｏ﹂う● 一"―

n10CChiriboshi 600 Mpa at25

mocchiriboshi 600 at 35--+-mocchiriboshi 600 Mpa at
30c―

mocchiribosih 600 Mpa 20C

10

0.2

0.4

0.6

0.8

1

Water Activity

Figure 3.3 Moisture Absorption Isotherm of Mocchiriboshi under 600 MPa

As it is indicated in Figure 3.3, moisture absorption isotherms follows type 2
isotherms in all temperatures. Similar to water absorption isotherms of mocchiriboshi
under different presslre treatments, the moistue content is also varied in mocchiriboshi

being treated under different temperatures. The moisture content of barley samples
treated under 600 MPa is lower than that of barley samples without pressure treatrnent

or mocchiriboshi samples with 200 MPa pressure treatrnent. The moisture content of
the samples firstly increased quickly as the water activity became higher. However, thespeed ofincreasing moisture content became stable from 0.4 to 0.6. When water activity

was over 0.6, moisture content increased largely. The moisture absorption isotherms ofbarley flour with 600Mpa high pressure processing treatment followed strictly withsigmoidal shape as introduced in the above text. However, the moisture content differed
as the incubation temperature changes. In the beginning, the moisture content was

higher in barley samaples with lower incubation temperature. After water activity wasover 0.5, the moisture content of barley samples with higher incubation temperatue
tent to reach to higher amount.

34

Discussion:
In order to calculate moisture content at dry basis, it is important to determine
the water and dry mass ratio (w/d ratio). A preexperiment was performed to determine
the w/d ratio. The amount of barley flour was 1.00 gram. Sample was dried in a generaloven under 105'C for two hours. Then the sample was removed from the oven and theput in room temperature for 30 minutes to cool down. After 30 minutes, the weight ofsample was measured and recorded. Then the sample was dried in the general ovenagain. The same procedure was repeated until the weight of the sample did not change
and remain in the constant range. The equation of dd ratio was listed as follow, andw/d ratio equals 0.1 :of water content
w/d rai _weightweight of diy mass

Moisture content is the quantity of water contained in a material. The amountof moisture in agricultural materials and food products affects the potential for storage
without molding or deterioration from chemical reactions such as oxidation. It also
allects the physical properties of the material. Pa(icle density tends to decrease as the
moisture content increases because the dry components such as starch and protein havea$eaterdensitythanwater.Productswithhighermoisturecontentshavehigher
is an excellent
lower electrical resistances because water
thermal conductivities andconductor of heat and electricity'

Moisture content also affects force-deformationmaterials: wet
to express the moistue content ofcharacteristics. Two methods are used
it is assumed
When performing these calculations'basis and dry basis moisture content'
constant'that the weight of the dry matter remainsthat the sample loses only water andwet basis moisture content (M,,) is described
the ratio of the weight of waterby the percentage equivalent of(Ww) to the total weight of the material(W)'

MFWVWt■ 100
Note that wet basis moisture content can range

from 0 to 100 percent'

Wet basis moisture is used to describe thewater content of agricultural materials

content" is used in the food industry it
and food products. When the term "moistureincontent' One important example occurs
almost always refers to wet basis moisture
pointof whole grains is determined at eachthe grain industry where moisture content
in the marketing channel where thegrain changes ownership'35

Dry basis moisture content (Ma) is described by the percentage equivalent ofthe
ratio of the weight of water (Ww) to the weight of the dry matter(Wa)'

140=1y*/\V6*100
Note that dry weight moisture content can range

from 0 to very large percentages'
moisture changes

duringDry basis moisture is most commonly used for describing
change in the dry basis
drying. When a sample loses or gains moisture' themoisture is linearly related to the weight loss or gain'
In this experiment, moisture content of dry basis was used'

The equation is listed

as follow:

wa, ht a f ter inctb dtton\O.l
Moisture content (dry basis): weight bef ore incllbotion-weight befoie inc,tbationx0 l

As it was indicated in the results, the shapes of the isotherms are characteristicof food with extremely high amount of starch, which sorb relatively small amount ofwater at low water activities and large amounts at high relatively humidity' The sharp
increase in water content at high water activities is due to its high amount of starch,which the smallest unit is glucose. At low water activities, the physical state of thesugars are known to absorb some water than the crystalline materials. At water activities

higher than 0.7, a leaching of sugar was observed, which was more pronounced at

higher temperatures. At water activities lower than 0.6, the equilibrium moisture
content of barley samples decreased significantly as the temperature was raised from
20 to 35"C in samples under all pressure treatments. However, the opposite effect wasobserved at higher water activities, and the barley flour samples absorbed more waterat higher temperatures. It means that in the high humidity region the water activity atconstant water content decreased as the temperature was raised.

At high water activities, the sugars are the determining factor of water
absorption in barley flour samples, either treated with high pressure or treated with mild
or even no pressure. The dissolution ofsugars increased significantly as the temperatue

is raised, off- setting the opposite effect of temperature on the sorption of nonsugar
solids. Similar effects of temperature have been observed by Audu et al (1978) on
sugars, and Weisser et al. (1982) on sugar alcohols. Chinachoti and Steinberg (1984)

found that sucrose added to starch gels increased sharply the sorption of water at water36

activities higher than 0'85' A strong interaction of amorphousstarch was detected by measuring the sorption isotherms

sucrose with gelatinizedof freeze-dried gels. Sugar_

biopolymer interactions may have some effect on tre observed

adsorption isotherms ofthe dried raisins. Roman et al. (1982) found that temperature had
the desorption isotherms ofapples at 20" to 60oc. compared to

the normal effect on

the isotherms ofraisins,there was no crossing of the curves at high water activities, which may

be due to thelower percentage of monosaccharides in the apples.

Equations of absorption isotherms
Six absorption models (Table 4.1) were tested to determine how well they fit
high-pressure-processed barley flour samples.
Table 4.1 Absorption Isotherm Models
卜1● d●

1

CA3(LABU】晨 et」.,1側 力 )

■
午

.

1ア

H」 柿暉」オbrdhm
ユW00餞 li〔 〕
RK)HN,1〕 勁「 Hcodcrrrnr(HENI}ERi0N. l|J5f)}絶け + : laしiC― ′+IC― )翼b.} {′
{′

′

￨

‐
‐
」け
)」

̀″

a.=+fl*4+<41
It o=a.tl,l+go,+Ca:)″彎彗ちイ +■,alPcie事

ELE(:.:り ]

0口極

̲

″

(0馴mN.1悌 輛)
Chu■ ■Hb耐"=」

L■ /{′

― )J

̲●

̀け

″" ‐ +Brh亀 )i1lUNGIPFO付 r,1ヽ 61ηヽ‐ ′A number of theoretical and empirical equations found in the literature were
tested for fitting experimental data of barley flour. The B.E.T equation was foundunsatisfactory, evidently due to the fact barley is mostly comprised of starch, whichchanged considerable the shape ofthe isotherm.

Statistical analysis ofan isotherm may be quantified through five standards: thecoefficient of determination (R2), the residual sum of squares (RSS), the standard errorof the estimate (SE), the mean relative deviation (PE%), and the plot of residuals. ln
this experiment, the coefficient of determination and the mean relative deviation were37

applied to evaluate whether the isotherm fit the mathematical models. The equation of
the mean relative deviation and the coefficient of determination are listed as below:
e xp erimental M -pr e dicte d M
e xperimenta.l M
y

R2=

(

M
MP

Where Meis the experimental value, Mo is the predicted value. The value of R2
close to l, and PE% below 5% indicates a good fit for practical purposes.

The six mathematical models presented in Table 4.1 were used to fit theexperimental data of barley flour samples. The statistical results shown in Table 4.2

indicated that Henderson model presented the best adjustment under the given
conditions. The determination coefficient (R2) was very close to the unit and the PE
was under 5%, indicating that this model is effective to describe the water sorption
isotherm for barley flour samples (0 MPa, 200 MPa 600 MPa) under given temperature.

Table 4.2 Estimated parameters of Henderson model for barley flours at different
temperatures

Parameters ol Henderson model

TemperatureA

B

PE (%)

R2

C

20

356.814

1.864

2.049

0.998

‑1.664253620.496

2.399

4.453

0.998

‑2.15130

1816.316

2.040

3.106

0.996

‑1.539356476.921

2.334

2.480

0.993

‑4.67038

Furthermore, quantitative evaluation ofexperimental sorption data provided
the basis of the GAB model at certain temperature under 600 Mpa is also good fit.

on

Table

4.3 summarizes the estimated constants along with the mean relative (pE%) andcoefficient of determination. At 25'c and 35'c, the low value of pEoz (3.s122-3.6767),
and correlation coefficients R2 (0 .9843-0.9920) close to unity indicate that GAB model

is good fit to the sorption data, and the estimated parameters were statistically
acceptable.

Table 4.3 GAB Model Calculation for Barlev at 600 MPa

Equation

Equation constants

PE

R:

(%)

GAB

a

b

c

20c

3.496

22.2350.8057

6.05230.989425C

4.112

282.846

0.80363.5122

0.992035C

4.496671.4040.88683.67670.984339

Conclusion:
According to the results obtained, moisture absorption isotherms of barleyflours follows type 2 isotherms in all temperatures. . However, the moisture content isvaried in mocchiriboshi being treated under different temperature. The moisture content

ofthe samples firstly increased quickly as the water activity became higher. The shapes
ofthe isotherms are characteristic of food with extremely high amount of starch, which
sorb relatively small amount of water at low waler activities and large amounts at highrelatively humidities. The sharp increase in water content at high water activities is due
to its high amount of starch, which the smallest unit is glucose.

The absorption isotherms of barley flour samples were best described byHenderson model. The determination coefficient (R3) was very close to the unit and the
PE was under 5%, indicating that this model is effective to describe the water sorption

isotherm for barley flour samples (0 MPa" 200 MPa, 600 MPa) under given temperature.

GAB model can also describe the absorption isotherms under 600 MPa under
25.C and 35.C. The determination coefficient (R2) was very close to the unit and the PE
was under 5o%.

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47.Mぉ ter thesis高 圧 処 理 が 大 麦 粉 の 物 性 お よび デ ンプ ンに 及 ぼ す影 響 by
Shoji Sぉ ∞48.

44