160 

 

Journal homepage: www.fia.usv.ro/fiajournal 

Journal of Faculty of Food Engineering,  

Ştefan cel Mare University of Suceava, Romania  

Volume XVI, Issue 3 - 2017, pag. 160  - 166 

 

 

THE USE OF INULIN AND SOY PROTEIN ISOLATE IN PRODUCING  

HARD-DOUGH BISCUITS FOR SENIOR PEOPLE 

 

Antonella DOROHOVYCH
1
, *Mykola PETRENKO

1 

 

1 Department of Bakery and Confectionery Goods Technology, National University of Food Technology 

Volodymyrska str. 68, Kyiv, Ukraine, 01601, captainartyaderain@gmail.com 

*Corresponding author 

Received   22th August 2017, accepted 27th September 2017 

 
Abstract: The article reviews the potential rationale of the addition of inulin and soy proteins to hard-

dough biscuits recommended for senior people’s diet. Hard-dough biscuits were considered as the 

objects of this nutritional enrichment since they have an optimal balance of proteins, fats and 

carbohydrates compared to the rest of flour-baked foods. Our study aimed to examine the role that 
inulin and protein play in the technological processes associated with producing hard-dough biscuits; 

in particular, special consideration was given to the selection of the optimal proportion of the new 

raw components, as well as the effect they cause on the quality of the hard-dough biscuits, the 
emulsion and the dough. The study identifies the role that inulin and soy protein isolate play in the 

heat treatment processes and storage of hard-dough biscuits intended for senior people. 

Recommendations have been given as to the healthy diet for senior people.The authors have proved a 
significant effect of the new raw materials on the structural and mechanical characteristics of dough 

that assumes additional elasticity due to the increase in the volume of bound moisture in the hydrated 

flour. It has been established that the addition of inulin and soy isolate prolongs the duration of the 

heat treatment of hard-dough biscuits. By consuming 100 g of special-purpose hard-dough biscuits, it 
is possible to fill up to 30% of the daily need for fiber in humans. The study has proved the advisability 

of using soy protein isolate and inulin when producing special-purpose hard-dough biscuits for senior 

people because of its enrichment with complete proteins, irreplaceable amino acids and food fibers. 
 

Keywords: functional foods, hard-dough biscuits, geriatric dietetics, soy protein, food fibers 

 

 

1. Introduction 
 

One of the most promising directions in 

the development of confectionery industry 

is the design of new functional food items 

that are capable of providing the necessary 

quantity of biologically active substances 

in the daily ration of a modern person.  

In the setting of the rising trend of 

diminished caloric value of food, the need 

for macro- and micronutrients remains the 

same, since their lack can lead to weaker 

immunity, health deterioration and a 

poorer quality of life. Among the products 

that are considered wholesome are 

functional foods that contain a high 

volume of biologically active components 

(antioxidants, vitamins, amino acids, 

minerals, food fibers), with a lower caloric 

value and low in sugar and fat. 

Consumption of such products improves 

physiological bodily processes, strengthens 

immunity and the person’s overall well-

being, as well as helps prevent chronic 

diseases [1]. 

When designing new functional products, a 

special focus should be placed on the 

requirements for the diets of certain 

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Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava 

Volume XVI, Issue 3 – 2017 

 
 

 
Antonella DOROHOVYCH, Mykola PETRENKO, The use of inulin and soy protein isolate in producing hard-dough 
biscuits for senior people, Food and Environment Safety, Volume XVI, Issue 3 – 2017, pag. 160 - 166 

 

 
161 

categories of population. The nutrition of 

senior people is studied and advised by 

geriatric dietetics. Below is some of such 

advice:  

1. An energetically balanced diet aligned 

with the body’s actual energy demands. 

2. Nutrition aimed at treatment and 

prevention of diseases. 

3. A ration well balanced in irreplaceable 

dietary factors. 

4. Intake of products that normalize 

intestinal microflora. 

5. Consumption of foods that are easily 

processed by food enzymes. 

6. The diet protein/fat/carbohydrates ratio 

should be 1/0.9/3.8 [1]. 

One of the promising ways of making 

functional products is the enrichment of 

existing products in biologically active 

substances through the use of innovative 

raw materials [2]. Among flour-baked 

foods, hard-dough biscuits make a good 

object for this enrichment, as of all other 

kinds of biscuits this one is characterized 

by the most balanced chemical 

composition of proteins, fats and 

carbohydrates, which makes it an 

appropriate foundation for designing 

healthy food recipes. 

The list of scientists who conducted 

research into the design of special-purpose 

bakery includes such prominent names as 

A. Tumanova, A. Dorokhovich, O. 

Yaremenko, M. Levachova, G. 

Sevryukova, and others [3, 4, 5, 6, 7]. In 

particular, a vast range of research on 

baking hard-dough biscuits low in caloric 

value and sugar was conducted in 2008 by 

O. Yaremenko [3]. These studies prove the 

practical sense of using food fibers and 

sugar substitutes in hard-dough biscuit 

recipes in order to impart them functional 

properties [4]. The studies also offer a deep 

analysis of the impact the new raw 

materials have on the processes of 

cooking, heat treatment and storage of 

biscuits.  

To improve the chemical formula of 

biscuits and align it with the prescriptions 

of geriatric dietetics, it was decided to 

enrich it in fiber and protein components, 

since these components are among the 

scarcest ones in today’s ration of senior 

people. The inulin has high degree of 

polymerization, allows it to stay 

undecomposed in the small intestine and 

carry out all the functions that are typical 

for decomposable food fibers The isolated 

soy protein was chosen as the source of 

complete protein. 

Inulin is a straight chain of fructofuranose 

residues connected with β-glycoside links; 

it belongs to the group of polysaccharides. 

It has a neutral sweet taste without 

unpleasant aftertaste, poorly soluble in 

water. A regular intake of inulin can help 

lower sugar in blood, which is of great 

importance for people with diabetes [8]. 

Consumption of inulin facilitates a whole 

range of functions in the human body, 

specifically lowers cholesterol in blood, 

stimulates intestines, reduces the risk of 

formation of malignant tumors in it, etc 

[9]. Inulin is characterized by a low caloric 

value in the range of 1.0-1.5 kcal/g, which 

allows using it in functional recipes. 

Soy isolate is a source of complete protein, 

high in irreplaceable amino acids [10]. Soy 

isolates contain over 92% of protein, 2.5% 

of carbohydrates, 0.5% of fat, 0.5% of raw 

fiber and 4.5% of ash, they have a low 

water content. They are produced through 

the chemical extraction of protein from 

defatted protein meal. Food cooked from 

soy isolates is especially rich in protein 

and low in fat, calories, cholesterol. 

Additionally, isolated soy proteins are 

much better digested than the proteins 

contained in soy flour. The protein isolate 

as a finished product is a white amphoteric 

powder without distinct taste or smell, 

which allows adding it to biscuit recipes 

without changing their organoleptic 

parameters and makes it a cheap and 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava 

Volume XVI, Issue 3 – 2017 

 
 

 
Antonella DOROHOVYCH, Mykola PETRENKO, The use of inulin and soy protein isolate in producing hard-dough 
biscuits for senior people, Food and Environment Safety, Volume XVI, Issue 3 – 2017, pag. 160 - 166 

 

 
162 

practicable protein-enrichment substance 

for functional food products [11].  

The study aims at designing a recipe of 

hard-dough biscuits according to the 

current recommendations of geriatric 

dietetics as to the diet of senior people and 

identifying the way the new raw materials 

(inulin and soy isolate) affect the quality of 

hard-dough biscuits, emulsion and the 

dough used for their production, as well as 

the heat treatment and storage of those 

biscuits. 

 

2. Matherials and methods 

 

The study examined the following objects: 

hard-dough biscuits, semi-finished 

products (dough, emulsion) and the raw 

ingredients for their recipes. First-grade 

wheat flour was used as a baseline raw 

ingredient, and other ingredients included 

powdered inulin and soy protein isolate 

and other components present in the hard-

dough biscuits recipe. The water content of 

the biscuits, semi-finished products and 

raw materials was being controlled using a 

SESH-3 drying oven. The gluten strength 

of the dough was measured with a gluten 

deformation measuring device IDK-2.  

The structural and mechanical performance 

of the dough was measured using the 

Strukturometer ST-1 device and a 

Brabender farinograph [12]. The water-

binding modes in the examined samples 

were identified through a 

thermogravimetric analysis using the 

Derivatograph Q-1500D device, which 

involved measuring the speed of water 

removal and the values of heat effects [13]. 

The sorption and desorption properties of 

hard dough and biscuits made of it were 

examined using a Macben sorption 

pump [14]. 

 

3. Results and discussion 

An important stage of designing a new 

variety of hard-dough biscuits consisted in 

determining an optimal quality of novel 

raw components in the recipe that would 

ensure that the resulting biscuits would 

have organoleptic properties no worse than 

those of customary biscuits. Three biscuit 

samples were studied: the first sample was 

a reference one, with the second sample 

inulin was added in the dough, and the 

third sample was cooked with soy protein 

isolate. The quality of the biscuits was 

evaluated based on their organoleptic 

properties in compliance with DSTU 

3781–14 [15].The biscuits were cooked 

according to a traditional technology in 

laboratory environment [16, 17]. The 

examined samples of biscuits cooked of 

the new ingredients are of comparatively 

bigger volume, a homogeneous structure 

when broken in parts, a higher density and 

a better taste. The optimal quality of the 

biscuits can be observed when the 

proportion of inulin is 7% and of protein 

isolate – 12% of the dough weight. 

The effect that the raw materials cause on 

the structural and mechanical properties of 

hard dough was established through 

measuring its boundary shear and adhesion 

value. Research has shown that the 

changes in the adhesion of hard dough are 

insignificant, whereas both inulin and soy 

isolate notably reinforce the dough 

structure, due to which the boundary shear 

of hard dough increases by 9% and 14% 

correspondingly. This can be explained by 

a greater content of bound liquid in the 

dough attributed to the active processes of 

hydration initiated by inulin and soy isolate 

whose water absorption capabilities are 

much higher than those of flour.   

The quality of the finished hard-dough 

biscuits is mostly determined by the 

structural and mechanical properties of the 

dough they are made of. Dough for the 

hard-dough variety of biscuits should have 

an elastic, springy structure and retain it 

during the kneading, rolling and forming 

of dough balls. That elastic and springy 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava 

Volume XVI, Issue 3 – 2017 

 
 

 
Antonella DOROHOVYCH, Mykola PETRENKO, The use of inulin and soy protein isolate in producing hard-dough 
biscuits for senior people, Food and Environment Safety, Volume XVI, Issue 3 – 2017, pag. 160 - 166 

 

 
163 

structure is attained thanks to the gluten 

frame of the dough that forms as a result of 

the hydration of gluten-forming proteins. 

To establish how inulin and soy isolate 

affect the properties of the gluten frame of 

hard dough, the authors tested (see Table 

1) the dough samples prepared according 

to recipes No. 1, 2 and 3 respectively, with 

inulin and isolated soy protein added to the 

dough.Having evaluated the obtained data, 

it is possible to argue that adding inulin 

and soy protein isolate to the dough 

slackens the gluten complex of hard 

dough; specifically, it reduces gluten 

stretchability and strength. 

The introduction of the new ingredients 

also results in a reduced content of raw 

gluten and a significant decrease in its 

hydration capacity (by 8% and 22% 

respectively), which indicates the reduced 

volume of free water in the dough and, 

obviously, can be attributed to the binding 

of free water by inulin and proteins added 

to the dough. 

 

Table 1. 

Characteristics of the gluten complex of hard-dough biscuits 

Characteristics 

Sample No. 

#1 
reference 

#2 
with inulin 

#3 

with inulin 
and protein 

isolate 

Gluten content, % of flour weight 25.3 21.3 19.0 

Hydration capacity, % 181.0 173.0 159.0 

Stretchability, cm 15 13 12 

Strength IDK-2, device units 72.0 81.0 75.0 

 

The dough test conducted using a 

farinograph (Table 2) verifies the 

assumptions put forward above as to the 

effect of the new raw materials on the 

dough structure.  

The dough containing inulin and soy 

isolate is 18.6% higher in its water 

absorption capacity and has lower 

stretchability, and that is a sign of a 

diminished volume of free water in the 

system and slower structure building 

processes, which is indicated by the double 

increase in the time needed for the dough 

to develop. 

The water content in dough was measured 

using thermogravimetric analysis. The 

analysis was carried out in the temperature 

range of 20-200°С using the Derivatograph 

Q-1500D device.  

Table 2.  

Results of farinogram analysis  

Characteristics 

Sample No. 

#1 

reference 

#2 

with inulin 

#3 
with inulin and 

protein isolate 

Water absorption capacity, cm3/100 g 58.6-55.6 44.8-43.3 71.0-69.5 

Dough development time, min 1.5 1.5 3.0 

Stability, min 0.0 0.0 0.0 

Dough softening, device units 120 140 120 

Elasticity, device units 120 130 105 

 

The test was applied to dough samples 

with water content of 27.0%. 

Derivatograms were analyzed 

according to the commonly accepted 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava 

Volume XVI, Issue 3 – 2017 

 
 

 
Antonella DOROHOVYCH, Mykola PETRENKO, The use of inulin and soy protein isolate in producing hard-dough 
biscuits for senior people, Food and Environment Safety, Volume XVI, Issue 3 – 2017, pag. 160 - 166 

 

 
164 

methodology, with results given in Table 3. 
Table 3.  

Results of derivatographic analysis 

Characteristic 

Sample No. 

#1 

reference 

#2 

with inulin 

#3 

with inulin and 

protein isolate 

Total water content, % 27.0 27.0 27.0 

Free water content, % 59.6 57.1 53.2 

Bound water, % 40.4 42.9 46.8 

Activation energy, kJ/mole 5.32 6.76 8.93 

 

The derivatographic analysis shows that 

the addition of inulin and soy isolate 

significantly affects the free to bound 

water ratio in hard dough. The addition of 

inulin to hard dough increases the volume 

of bound water by 2.5%, while the addition 

of soy protein isolate results in an increase 

of 6.4%. This is accompanied by the 

increase in the value of activation energy 

in the samples different from the reference 

one, which also indicates that when added 

to the recipe, the new raw ingredients 

generate stronger forms of bound water in 

the dough. Such notable increase in the 

volume of bound liquid can be explained 

by the presence of stronger forms of water 

binding in the samples different from the 

reference one. This is accompanied by the 

increase in the value of activation energy 

in the samples different from the reference 

one, which also indicates the emergence of 

stronger forms of bound water in the 

dough and that they require more energy to 

be broken down.  

The increase in the amount of water bound 

in the dough will affect the duration of the 

heat treatment of hard-dough biscuits and 

will require correcting the baking time and 

temperature for the new hard-dough 

biscuits. Besides, the reduced content of 

free water will slow down the hardening of 

the hard-dough biscuits and positively 

affect its shelf life during storage. 

However, the shelf life and storage 

conditions of the biscuits are determined 

not only by the amount of bound water, but 

also by the intensity of sorption and 

desorption processes that take place in the 

course of storage, so the authors examined 

the aforementioned sorption and 

desorption processes using a Macben 

sorption pump for the dough (Fig. 1 and 

Fig. 2) and for the finished hard-dough 

biscuits (Fig. 3). 

Judging from the moisture adsorption 

graph, it is possible to say that the samples 

were adsorbing liquid quite slowly up to 

the pressure of P/Ps=0.35, because the 

pores inside them were filled before the 

start of the adsorption and did not clear in 

time. This is also testified by the 

practically missing surface, as closed pores 

do not take in liquid; however later on they 

got more active, since the sample was 

being diluted under the pressure of liquid 

and evaporated water was being absorbed, 

for the pores in the samples were quite 

large. Sample #2 demonstrated the lowest 

moisture sorption capacity, while sample 

#1 – the highest one. The hysteretic loop 

was also wide in the case of sample #2, 

which indicates that having sucked in the 

water, the sample took a while to dry up to 

its initial state at the same temperature, and 

did not release all its water because its 

adsorption capacity at zero pressure is 

higher than the initial one. 

The greatest number of the smallest pores 

was registered in the sample #1, which is 

evident when looking at the pore radius 

distribution graph (Fig. 2); the peak sizes 

of the pores of the samples #2 and #3 are 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava 

Volume XVI, Issue 3 – 2017 

 
 

 
Antonella DOROHOVYCH, Mykola PETRENKO, The use of inulin and soy protein isolate in producing hard-dough 
biscuits for senior people, Food and Environment Safety, Volume XVI, Issue 3 – 2017, pag. 160 - 166 

 

 
165 

almost identical — 16.8 and 16.2 Å (1.68 

and 1.62 nm), whereas the sample #1 has 

slightly narrower pores of 13.2 Å (1.32 

nm). 

 

 
 

Fig. 1. Sorption/desorption isotherms for the hard 

dough used to cook the biscuits: 1 – reference 

sample, 2 – sample with inulin, 3 – sample with 

inulin and soy protein isolate 

 

Fig. 2. Pore radius distribution graphs for the 

hard-dough biscuit sample: 1 – reference sample, 2 

– sample with inulin, 3 – sample with inulin and 

soy protein isolate 

 

  
Fig. 3. Sorption/desorption isotherms for the hard 

dough used to  

cook the biscuits: reference sample 

 

Fig. 4. Sorption/desorption isotherms for the hard 

dough used to cook the biscuits: sample with inulin 

and soy protein isolate 

 

The calculation of the adsorption energy 

based on the obtained data shows that for 

the sample #1 it is equal to 4.818 kJ/mole, 

for the sample #2 – 4.869 kJ/mole, and for 

the sample #3 – 4.419 kJ/mole. Following 

the analysis of the hard-dough biscuits 

sorption isotherms (Fig. 3), it was 

established that the equilibrium moisture 

values for the reference sample and the 

sample with inulin and soy protein isolate 

in the range of aw = 0.75…0.85 are equal 

to 12.0–12.5%, which in turns implies that 

the effect of the new raw ingredients on the 

sorption capacity of the biscuits  is 

insignificant. Yet  for  hard-dough  biscuits  

that are capable of actively absorbing 

moisture during storage, high sorption 

capacity would negatively affect the 

quality of the product and its shelf life, so 

we recommend packing the finished 

biscuits in vacuum package. 

 

4. Conclusion 

 

The study has shown that, provided they 

are used in optimal proportions, inulin and 



Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava 

Volume XVI, Issue 3 – 2017 

 
 

 
Antonella DOROHOVYCH, Mykola PETRENKO, The use of inulin and soy protein isolate in producing hard-dough 
biscuits for senior people, Food and Environment Safety, Volume XVI, Issue 3 – 2017, pag. 160 - 166 

 

 
166 

soy protein isolate do not cause any 

negative effect on the technological 

characteristics of the dough and the 

finished biscuits, which means they can be 

produced using the existing machinery and 

equipment. The novel hard-dough biscuits 

have the closest to optimal balance of 

proteins, fats and carbohydrates compared 

with ordinary hard-dough biscuits chosen 

as a reference product. Since neither inulin 

nor soy protein isolate have distinct taste 

or flavor, the organoleptic properties of the 

finished biscuits are identical to the 

ordinary hard-dough biscuits. The caloric 

value of the hard-dough biscuits with soy 

protein isolate and inulin is 389 kcal/100 g; 

in addition, it has a higher nutritional and 

biological value and satisfies 30% of 

human daily requirement for fiber and 15% 

of daily requirement for proteins (the 

content of essential amino acids in 100 g: 

isoleucine – 0,75 g, leicine – 1,16 g, lizin – 

0,65 g, methіonіne+cystine – 0,36 g, 

phenylalanіne+tyrosine – 0,97 g, treonine 

– 0,55 g, tryptophan – 0,21 g, valin – 

0,75 g), which makes it reasonable to label 

these biscuits as a functional product.  

The chemical formula of these biscuits also 

takes into account the prescriptions of 

geriatric dietetics, so these biscuits are 

recommended for consumption by senior 

people. Also, due to the absence of white 

granulated sugar in the recipe of the 

biscuits, the finished product will also be 

suitable for consumption by people 

suffering from diabetes. 

 

 

5. References 

 
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[3].YAREMENKO O., DOROHOVICH A. 

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[4].YAREMENKO O., DOROHOVICH A.  

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	1. Introduction