Journal of Engineering Studies and Research Volume 16 (2010) No. 4 44 [619152]

Journal of Engineering Studies and Research – Volume 16 (2010) No. 4 44

RESEARCH REGARDING THE INFLUENCE OF
HYDROTHERMAL PROCESSING ON THE WHEAT MILLING
PROCESS AND ON THE QUALITY OF FLOUR

RUSU TITI1*, NECULAIASA VASILE2

1 SC Morărit Panifica ție SA Roman, Romania
2„Gheorghe Asachi” Technical University Ia și, Romania

Abstract : The study is explaining the way in which the hydrothermal processing of wheat is
influencing the technological characteristics of the wheat berries and the baking quality of
the resulting flour. Also there were established the correlations between the manners of
conditioning and the degree of flour extracti on, the specific power consumption and the
quality of the products and of the sub-prod ucts resulting after the milling process.

Keywords : water, wheat, conditioning, technological characteristics, flour.

1. INTRODUCTION

The purpose of hydrothermal processing of wheat (PHT) in the process of wheat preparation before milling in
the cleaning-conditioning sections is to modify correctly and in the desired direction the technological properties
of wheat berries. PHT (hydrothermal processing) – represents the artificial operation on the wheat berries with water or with water and heat followed by a rest period. Given that in the mills ther e are processed cereals with
different physical, chemi cal and technological characteristics it is n ecessary to ensure a stable quality of the
processed cereals in order to obtain superior quality flou r. For this the conditioning of wheat by means of PHT
and rest occupies a predominant place as regards to the efficiency of using cereals in the processing.

2. THEORITICAL CONSIDERATION REGARDING THE INFLUENCE OF CONDITIONING METHODS ON THE MODIFICA TION OF WHEAT TEHNOLOGICAL CHARACTERISTICS

In the present there are know n the following conditioning methods: cold, ho t, fast, with infrared and ultraviolet
radiations, by magnetic activation of water and cyclical processing of wheat berries with the use of high and low
temperatures. The basic factors which influence the efficiency of the conditioning methods of the wheat berries of different qualities are: humidity, processing period, temp erature, environmental conditions and the rest period.
The conditioning of wheat is peculiarly influencing the structural and mechanical characteristics of wheat
berries, the milling characteristics of wheat berries an d the bakery characteristics of the resulting flours.

The basic indexes which characterize th e structural and mechanical charact eristics of the wheat berries are:
resistance, hardness and the indexes of the rheological characteristics.

The resistance of a wheat berry during milling is a basic index characteristic for it at grounding expressed by the
power consumption and the degree of grinding. The milling characteristics of wheat berries are characterized by
the extraction and the quality of intermediary products fr om the first gristing passages. The modification of the

* Corresponding author, e-mail : [anonimizat]

Journal of Engineering Studies and Research – Volume 16 (2010) No. 4 45

milling characteristics of wheat by means of conditioni ng is connected to the loosening of the endosperm
pursuant to the intensive internal transfer of water during the rest.

The rest period and the degree of moistening depend on the variety of wheat (with a glassy and floury
consistence) and influence the extraction and the quality of intermediary products from the gristing passages [1 –
3].

3. THE TECHNICAL BASE TO PERF ORM THE WHEAT PROCESSING AND
HYDROTHERMALLY DETERMINE THE TEHNO LOGICAL CHARACTERIS TICS OF WHEAT
BERRIES

For the experimental determinations regarding the influence of hydrothermal processing on the modification of
the technological characteris tics of wheat berries were used, as a technical base, the equipments in the
technological scheme of wheat berries preparation before milling in the cleaning-conditioning section of the wheat mill of Roman. The physical-chemical examinations of wheat were performed in the mill’s test laboratory,
and for the finite products in the accred ited laboratory of the br ead and bakery products f actory. The high quality
of the technological equipments in the cleaning-conditioning section enabled a complex research and a comparison of the influence of different methods of hydrothermal processing on the milling characteristics of
wheat berries and on the bakery characteristics of flour. The cold conditioning in the cleaning section is achieved
in two manners; the first one uses three stages of wheat berries moistening and rest, th e first two are basic stages
and the third stage is the final one. This option allows different moistening of wheat berries depending on the
initial humidity and quality and is efficient for the conditioning of high glassiness and low humidity wheat since
only the moistening stage cannot provid e the humidity level necessary for the wheat berries in grist I. According
to the second manner the conditioning is achieved in tw o stages of wheat berries moistening and rest [4].

4. EXPERIMENTAL

The experimental determinations were performed for each manner of hydrot hermal processing of wheat berries.
By means of measures and laboratory tests were dete rmined the milling characteristics of wheat berries,
expressed by extraction of flour, the quality of intermedia ry products from the grist passages, the quality of the
obtained flour and the specific power consumption per ton of milled wheat. By choosing the optimum rest period
for the wheat with hard and soft berries was researched the influence of humidity in grist one on the extraction
and the ashes of semolina, dunst and fl our obtained in grist I ….grist IV.

The experimental data is presented in the tables. In Table 1 are presented the experimental data referring to the
extraction of intermediary products acco rding to the humidity and the rest period of the wheat berries with a
medium glassiness of 68%.

Table 1. The experimental data referring to the extractio n of intermediary products according to the humidity and
the rest period of the wheat berries with a medium glassiness of 68%.
Extraction [%]
Initial
humidity of
wheat
[%] Final
humidity of
berries at
Gr.I
[%] Rest
time
(hours) Large
semolina
from
GrI ..GrIV
[%] Medium and
small semolina
from GrI..GrIV
[%] Dunst from
GrI..Gr.IV
[%]
Total of intermediary
products

[%]
12.5 12.3 – 42.00 20.00 9.0 72.0
12.5 14.5 6 38.50 22.50 12.5 73.5
12.5 15.5 10 36.00 24.00 14.0 74.0
12.5 16.5 12 32.50 26.50 16.7 75.7

From the presented experimental data one can conclude that along with the increase of the humidity action on the berry the structure of th e endosperm is destroyed and this is redu cing the extraction of large and medium
semolina and is increasing the quantity of small semolina and of dunst. The modification of the percentage of

Journal of Engineering Studies and Research – Volume 16 (2010) No. 4 46

other production fractions begins after 3.5 – 4.5 hours of rest, namely when the water began passing in the
superficial layers of the endosperm and stops after 10 – 12 hours of rest, after which the extraction of the other
products is no longer modified. In Table 2 are presented the experimental data regarding the extraction of
intermediary products when milling the soft wheat with a medium glassiness of 45%.

Table 2. The experimental data regarding the extraction of intermediary products when milling the soft wheat
with a medium glassiness of 45%.
Extraction [%] Initial
wheat
humidity
[%] Final
humidity of
Wheat berries
at
Gr.I
[%] Rest
period
(hours) Large semolina
from
GrI ..GrIV [%] Medium and
small semolina
from GrI..GrIV
[%] Dunst
from
GrI..Gr.IV
[%]
Total of
intermediary
product
[%]
12.5 12.3 – 38.00 23.00 10.0 71.0
12.5 14.5 6 36.50 24.80 11.7 73.0
12.5 15.5 8 34.00 26.20 14.0 74.2
12.5 16.5 10 30.50 28.50 16.5 75.5
It can be observed that when conditioning the soft whea t (45% glassiness) and the duration of rest of (6…10
hours), the extraction of large semolina diminishes with 4%, the quantity of medium and small semolina
increases with 3%, the quantity of dun st increases with 1% and the extrac tion of flour increases with 2%. In
Table 3 there are presented the experimental data regarding the influence of wheat conditioning methods on the modification of the characteristics of wheat milling and on the quality of intermediary and finite products.

Table 3. The experimental data regard ing the influence of wheat conditioning methods on the modification of the
characteristics of wheat milling and on the quality of intermediary and finite products.
Extraction and quality of intermediary and finite products
Conditioning
methods Wheat
humidity in
Gr.I
[%] Large
semolina
[%] Ash of large
semolina
[%] Mean of ash
in
interm.
products [%] Flour
ash
[%] Total
extraction
of
[%]
0. 1. 2. 3. 4. 5. 6.
Wheat with a glassiness of 6 8 %
Cold conditioning 15.5 36.0 1.25 0.90 0.65 74.5
Hot circumanience conditioning 16.0 35.1 1.19 0.87 0.63 75.2
Wheat with a glassiness of 4 5 %
Cold conditioning 15.3 34.0 1.15 0.88 0.64 74.2
Hot circumanience
conditioning 16.1 35.5 1.05 0.82 0.62 75.1

I t c a n b e o b s e r v e d t h a t i n c a s e o f c o l d c o n d i t i o n i n g when the water temperature is not higher than 20°C the
quantity of large semolina and the content of ash increases as compared to hot conditioning. Also the total
extraction of flour increases significa ntly, the ash decreases in case of hot conditioning as compared to cold
conditioning, a tendency manifested also for the wheat w ith a glassiness of more than 68%. In Table 4 is
presented the experimental data regarding the influence of conditioning on the specific power consumption per
ton of milled wheat.
For a humidity of 12.5%…12.8% of the unconditioned wheat with a dry layer the wheat berries have the
appearance of some shivery and elastic elements which at a certain dynam ic load on the roll break with a
reduced power consumption as compared to the hot and cold conditioned wheat berries when the humidity is of
15.8% …16.5%. This phenomenon is explained by the fact that the wheat berry is acting as an elastic element so
that it increases the grinding power.

Journal of Engineering Studies and Research – Volume 16 (2010) No. 4 47

Table 4. The experimental data regarding the influence of conditioning on the specific power consumption per
ton of milled wheat.
Conditioning method Power consumption
(kw/tone of milled wheat) Glassiness
[%] Humidity on Grist I
[%]
102 (86) 45 Unconditioned wheat
108 (88) 68 12.5
12.8
88 (89.4) 45 Cold conditioned wheat
94 (94) 68 15.8
86 (102) 45 Hot conditioned wheat
88 (108) 68 16.5

5. CONCLUSIONS

Based on the experimental determinations the following conclusions can be drawn:
– Along with increasing the action of humidity on the wheat berry, the structure of the endosperm is destroyed
and results in reducing the extraction of large and medium semolina and increasing the quantity of small semolina and of dunst;
– The modification of the percentage of other production fractions begins only after 3.5 – 4.5 hours of rest,
namely when the water began passing in the superficial layers of the endosperm and stops after 8 – 10 hours when the extraction of other products is no longer modified;
– The rest period and the moistening degree on the varieties of wheat with a glassy and floury consistency of
more than 68% influences the extraction and the quality of intermediary products from grist I … grist IV; – Along with increasing the rest period from 4 to 24 hour s, the extraction of large semolina from the wheat with
a glassiness of more than 68% was reduced with 2.5% and the flour extraction was increased with 1.5%;
– From the cold conditioned wheat berries result larger semolina than from the hot conditioned wheat berries
from which result smaller semolina due to the loosening of the endosperm;
– The quality of the flour with an extraction of 75.7% certifies the technological efficiency of hot conditioning, a
method which allows uniform moistening of the marginal areas of wheat berries;
– The specific power consumption is lower when milling the cold conditioned wheat berries with a small
glassiness (group III of glassiness) and increases when milling the hot conditioned high glassiness berries (group I of glassiness);
– The arrangement adopted by PHT can adjust the releas e of some biochemical processes in the wheat berry
which are accompanied by quantitative and qualitative modifications of gluten and of the baking quality of flour; – The optimum humidity of wheat berries in grist I must be of 16% – 16.5%;
– The optimum rest period is practically established by means of experimental determinations based on
glassiness and the conditioning method.

REFERENCES

[1] *** Anuarul Asocia ției Speciali știlor din Mor ărit și Panifica ție, Colectie, 1995 – 2003.
[2] *** Buletinul Informativ pentru industriile de mor ărit și panificație, vol. 10, Nr. 2, 1999.
[3] Leonte, M., Preg ătirea cerealelor pentru m ăciniș, Millenium Publishing House, Piatra Neam ț, 2003.
[4] Rusu, T., Necul ăiasa, V., Cercet ări privind influen ța metodelor de condi ționare a grâului asupra calit ății făinii
destinate fabric ării pâinii și produselor de panifica ție, Buletinul IP, Ia și, Tomul LVI (LX), 2010.